U.S. patent application number 15/220816 was filed with the patent office on 2016-11-17 for revision systems, tools and methods for revising joint arthroplasty implants.
The applicant listed for this patent is ConforMIS, Inc.. Invention is credited to Philipp Lang, John Slamin, Daniel Steines.
Application Number | 20160331467 15/220816 |
Document ID | / |
Family ID | 50881769 |
Filed Date | 2016-11-17 |
United States Patent
Application |
20160331467 |
Kind Code |
A1 |
Slamin; John ; et
al. |
November 17, 2016 |
Revision Systems, Tools and Methods for Revising Joint Arthroplasty
Implants
Abstract
Disclosed herein are methods, compositions and tools for
repairing an articular joint having a failed implant. The articular
repair systems are customizable or highly selectable by or
adaptable to individual patients and geared toward providing
optimal fit and function. The surgical tools are designed to be
customizable or highly selectable by or adaptable to individual
patients to increase the speed, accuracy and simplicity of
performing total or partial arthroplasty including revision
surgeries.
Inventors: |
Slamin; John; (Wrentham,
MA) ; Lang; Philipp; (Lexington, MA) ;
Steines; Daniel; (Lexington, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ConforMIS, Inc. |
Bedford |
MA |
US |
|
|
Family ID: |
50881769 |
Appl. No.: |
15/220816 |
Filed: |
July 27, 2016 |
Related U.S. Patent Documents
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Application
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14238989 |
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9402726 |
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PCT/US12/50964 |
Aug 15, 2012 |
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15220816 |
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15137607 |
Apr 25, 2016 |
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14238989 |
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13938081 |
Jul 9, 2013 |
9320620 |
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15137607 |
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13294564 |
Nov 11, 2011 |
8906107 |
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13938081 |
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12660529 |
Feb 25, 2010 |
8480754 |
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13294564 |
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12712072 |
Feb 24, 2010 |
8234097 |
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12660529 |
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61523756 |
Aug 15, 2011 |
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61155362 |
Feb 25, 2009 |
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61269405 |
Jun 24, 2009 |
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61273216 |
Jul 31, 2009 |
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61275174 |
Aug 26, 2009 |
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61280493 |
Nov 4, 2009 |
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61284458 |
Dec 18, 2009 |
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61155359 |
Feb 25, 2009 |
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61220726 |
Jun 26, 2009 |
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61208440 |
Feb 24, 2009 |
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61208444 |
Feb 24, 2009 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B33Y 70/00 20141201;
A61B 17/1778 20161101; A61B 2034/108 20160201; A61F 2/30756
20130101; A61B 5/4533 20130101; A61F 2/46 20130101; A61B 2034/2065
20160201; B33Y 80/00 20141201; A61F 2/389 20130101; A61F 2/38
20130101; A61B 2017/568 20130101; A61B 2034/104 20160201; A61B
17/1675 20130101; A61B 2034/102 20160201; A61B 34/10 20160201; A61B
17/154 20130101; A61F 2002/3069 20130101; A61B 5/4528 20130101;
Y10T 29/49 20150115; A61B 17/1666 20130101; A61B 17/1703 20130101;
A61B 5/4523 20130101; A61B 2034/105 20160201; A61B 34/20 20160201;
A61F 2/3859 20130101; A61F 2/30942 20130101; A61B 17/157 20130101;
A61B 17/155 20130101; A61B 17/158 20130101; A61B 17/1746 20130101;
A61B 17/175 20130101; A61B 5/4514 20130101 |
International
Class: |
A61B 34/10 20060101
A61B034/10; A61B 17/15 20060101 A61B017/15; A61F 2/38 20060101
A61F002/38 |
Claims
1. A method of making a revision implant for repairing a patient's
joint, the method comprising: obtaining image data associated with
at least a portion of a failing implant existing in the patient's
joint; deriving information about the failing implant and the
patient's joint from the image data; obtaining existing information
about the failing implant using original electronic files that have
been used to make the failing implant; and making the revision
implant based on the derived information about the failing implant
and the patient's joint and the existing information about the
failing implant.
Description
RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. Ser. No.
14/238,989, entitled "Revision Systems, Tools and Methods for
Revising Joint Arthroplasty Implants" filed Apr. 3, 2014, which in
turn is a National Stage of PCT/US12/50964, entitled "Revision
Systems, Tools and Methods for Revising Joint Arthroplasty
Implants, filed Aug. 15, 2012, which in turn claims the benefit of:
U.S. Ser. No. 61/523,756, entitled "Revision Systems, Tools and
Methods for Revising Joint Arthroplasty Implants," filed Aug. 15,
2011.
[0002] This application is also a continuation-in-part of U.S. Ser.
No. 15/137,607, filed Apr. 25, 2016, entitled "Patient-Adapted and
Improved Articular Implants, Designs and Related Guide Tools,"
which in turn is a continuation of U.S. Ser. No. 13/938,081, filed
Jul. 9, 2013, entitled "Patient-Adapted and Improved Articular
Implants, Designs and Related Guide Tools," which in turn is a
continuation of U.S. Ser. No. 13/294,564, filed Nov. 11, 2011,
entitled "Patient-Adapted and Improved Orthopedic Implants, Designs
and Related Guide Tools," which in turn is a continuation of U.S.
Ser. No. 12/660,529, filed Feb. 25, 2010, entitled "Patient-Adapted
and Improved Articular Implants, Designs and Related Guide Tools,"
which in turn claims the benefit of: U.S. Ser. No. 61/155,362,
entitled "Patient-Specific Orthopedic Implants And Models," filed
Feb. 25, 2009; U.S. Ser. No. 61/269,405, entitled "Patient-Specific
Orthopedic Implants And Models," filed Jun. 24, 2009; U.S. Ser. No.
61/273,216, entitled "Patient-Specific Orthopedic Implants And
Models," filed Jul. 31, 2009; U.S. Ser. No. 61/275,174, entitled
"Patient-Specific Orthopedic Implants And Models," filed Aug. 26,
2009; U.S. Ser. No. 61/280,493, entitled "Patient-Adapted and
Improved Orthopedic Implants, Designs and Related Tools," filed
Nov. 4, 2009; U.S. Ser. No. 61/284,458, entitled "Patient-Adapted
And Improved Orthopedic Implants, Designs And Related Tools," filed
Dec. 18, 2009; U.S. Ser. No. 61/155,359, entitled "Patient
Selectable Joint Arthroplasty Devices and Surgical Tools," filed
Feb. 25, 2009; and U.S. Ser. No. 61/220,726, entitled
"Patient-Specific Orthopedic Implants And Models," filed Jun. 26,
2009.
[0003] U.S. Ser. No. 12/660,529 is also a continuation-in-part of
U.S. Ser. No. 12/712,072, entitled "Automated Systems For
Manufacturing Patient-Specific Orthopedic Implants And
Instrumentation" filed Feb. 24, 2010, which claims the benefit of
U.S. Ser. No. 61/208,440, entitled "Automated Systems for
Manufacturing Patient-Specific Orthopedic Implants and
Instrumentation" filed Feb. 24, 2009, and U.S. Ser. No. 61/208,444,
entitled "Automated Systems for Manufacturing Patient-Specific
Orthopedic Implants and Instrumentation" filed Feb. 24, 2009.
[0004] Each of the above-described applications is hereby
incorporated herein by reference in its entirety.
FIELD OF THE INVENTION
[0005] This disclosure relates to orthopedic methods, systems and
prosthetic devices and more particularly relates to methods,
systems and devices for articular resurfacing and for correcting
failed surgical resurfacing and/or replacement implants. The
disclosure also includes surgical tools, molds and/or jigs designed
to achieve optimal cut planes in a joint in preparation for
installation of a joint revision implant.
BACKGROUND OF THE INVENTION
[0006] Joint arthroplasties can be highly invasive and often
require surgical resection of the entirety, or a majority of the,
articular surface of one or more bones involved in the repair. In
various procedures, the marrow space can be fairly extensively
reamed in order to fit the stem of the prosthesis within the bone.
Reaming results in a loss of the patient's bone stock and over time
subsequent osteolysis will frequently lead to loosening of the
prosthesis. Further, the area where the implant and the bone mate
can degrade over time requiring the prosthesis to eventually be
replaced. Since the patient's bone stock is limited, the number of
possible replacement surgeries is also limited for joint
arthroplasty. In short, over the course of 15 to 20 years, and in
some cases even shorter time periods, the patient can run out of
therapeutic options ultimately resulting in a painful,
non-functional joint and/or requiring fusion or partial-fusion of
the joint.
[0007] Current joint replacement and/or resurfacing implants, and
the surgical corrections associated with implanting such devices,
are generally accepted to be of finite duration. That is, assuming
the patient's continued survival and/or continued use of the joint,
every joint replacement and/or repair procedure will eventually
require further surgery to repair and/or replace a failed or
failing joint implant.
[0008] Failure of an implant and/or surgical correction can be a
result of various causes. The implant may fracture, loosen or
disassemble in some manner, or components may simply wear out
and/or cease to properly function after prolonged use. Similarly,
implant failure may be due to failure of the underlying support
and/or anchoring structures, either due to continued progression of
disease or pursuant to unexpected and/or excessive stresses.
Moreover, an implant may fail where it has been malpositioned, or
where it is experiencing unexpected/unacceptable loading for a
variety of factors. Another contributing failure factor could be
excessive pain generated and/or felt at the implant site. Other
failure factors can include excessive debris generation, scar
tissue intrusion into the joint space and/or unacceptable
inflammation/swelling of the joint, uncontrollable infection at the
implant site, and or development of necrosis, cysts, malignant
neoplasm or other localized or systemic disease necessitating
implant removal.
[0009] Regardless of the underlying cause, the removal of a failed
implant generally necessitates a surgical intervention to remove or
otherwise revise the original "failed" implant. Such a procedure
also typically involves the placement of a subsequent or "revision"
implant in the joint space, to correct the underlying joint
function and/or otherwise address additional hard and soft tissue
damage that may have occurred during the initial implant removal
process and/or during subsequent preparation and placement of the
revision implant. However, because a significant and potentially
unknown amount of the original anatomical support structure is
generally removed during the original implant surgery to place the
original implant (now failed or failing), because additional native
support structures may be removed with the failed implant, because
the amount of further degradation of the anatomical support
structure (post original surgery) is generally unknown or
undetermined prior to removal of the failed implant during the
revision surgery and because "artifacts" from the failed or failing
implant often distort or otherwise mask anatomical or other
features obtained using non-invasive imaging methods, there remains
a significant need for improvements in the planning and execution
of revision surgeries.
SUMMARY OF THE INVENTION
[0010] Current surgical revision procedures typically fail to
utilize many sources of highly relevant patient and/or implant
related information in planning and executing implant revision
procedures. Moreover, the information available to a surgeon
(and/or information that is presented to the surgeon) is generally
not properly assessed for accuracy and/or cross-referenced/compared
to other available relevant information to ensure accurate
reflection of the condition of the patient's anatomy and/or the
failed implant. The failure to assess multiple sources of
information accurately, the failure to cross-reference and/or
evaluate such information to create a more comprehensive picture of
the failed implant and the patient's disease state, and the failure
to provide a treating surgeon with an accurate pre-operative
evaluation of the failed implant, the patient's anatomy, the
disease state and/or the information regarding the potential
surgical site significantly reduces the opportunity for a surgeon
to correct the failed implant in a "least-invasive" and/or "most
effective" manner. Moreover, the failure to have such information
available during the planning and implant design phase may result
in designing or choosing an incorrect/unsuitable implant and/or an
implant that requires removal of healthy bone stock which could
have been preserved for future use if the patient's anatomy were
appropriately assessed.
[0011] In addition, this disclosure further includes the
realization that one or more components of a failed or failing
implant can often be utilized as one or more accurate reference
points to facilitate the repair or replacement of a failed or
failing partial or total joint replacement implant. In current
revision surgery, a surgeon initially removes the failed implant
components, and then prepares the anatomical support structure for
the revision implant. Because much of the supporting anatomical
structure may have been removed and/or modified (during the
original surgery) to accommodate the original failed implant, and
because addition anatomical degredation, anatomical structure
removal and/or remodeling may have occurred prior to the revision
surgery, a significant amount of time and effort, and a significant
number of surgical tools, are utilized by the surgeon to locate
desired anatomical alignment and/or positioning relative to any
"virgin" anatomical reference points (i.e., intramedullary canal
reference points, etc.). However, much of the additional alignment
efforts can be readily reduced or obviated by the use of anatomical
reference points from the existing implant components, which can
often be readily visualized via non-invasive imaging methods. When
desired reference planes and/or reference positions can be
identified and/or determined relative to such implant reference
points (such as through an electronic evaluation system utilizing
non-invasive imaging information), such reference points can be
particularly useful as anatomical reference points for the planning
and/or conduct of the surgery. Where surgical reference tools
and/or jigs incorporate surfaces that match or otherwise
substantially conform to some portion of the "failed implant," and
are connected to or otherwise positioned relative to the "failed
implant" prior to component removal (or other displacement of the
component relative to the patient's joint), the failed implant can
provide a highly accurate reference for subsequent surgical steps,
including the placement of anatomical reference markers (i.e.,
alignment pins, etc.) or for aligning surgical cutting and or
drilling/reaming tools for the creation of desired cutting
planes/openings. Moreover, because implant "failure" can often be
attributed to the failure of one component or portion of a
component (i.e., a tibial stem will loosen while the femoral stem
remains intact, or a condylar component will fracture with the
remainder of the femoral component attached to the femur), the
remaining component or component portions can often be utilized as
a highly accurate reference position as well.
[0012] This disclosure describes systems, devices and methods for
collecting and assessing multiple sources of patient, implant and
potentially general population anatomical data, cross-referencing
and evaluating the various data sources, and providing an evaluated
output for a surgeon and/or implant designer/manufacturer to use in
choosing, designing, manufacturing and implanting a replacement or
"revision" implant in a selected patient or patients.
[0013] The various embodiments of systems, devices and methods
discussed herein, including the various systems for collecting,
assessing, utilizing and presenting multiple sources of patient
and/or other surgical data, may be particularized or personalized
for a selected "target audience," such as for a surgeon for
planning and performing a surgical implant revision procedure, for
an implant designer for designing a revision implant, or for a
patient who wished to visualize and/or evaluate the outcome of a
knee replacement procedure. Such output may comprise different
data, different presentation methods, differing evaluations and/or
analysis or various combinations particularized based upon an
intended use for the information. In a similar manner, various
embodiments may compare and evaluate prior scan image data relative
to later scan data and create an output "map" or other presentation
of the patient's anatomy, highlighting areas of bone growth or
reduction, as well as changes in bone quality (i.e.,
increases/decreases in cancellous or cortical bone quality or
quantity) as well as other tissue types (i.e., changes in articular
cartilage and/or soft tissue quality and/or scarification). Such
outputs could be extremely useful in diagnosing and/or treating
underlying disease or other issues prior to, during or after
implant or implant revision surgery.
[0014] In addition, this disclosure describes utilizing one or more
portions of an existing "failed implant," either alone or in
combination with other natural or artificial "anatomical features,"
as one or more anatomical reference points to assist in the
planning, surgical preparation and/or alignment of surgical cutting
instruments and/or to facilitate placement of a revision
implant.
[0015] The current disclosure also contemplates the use of various
pre-operative anatomical and "failed implant" data in the design
and implantation of a desired revision implant. For example, where
an implant has fractured or otherwise failed in some manner (such,
for example, due to repetitive loading and wear over an extended
period of time), the pre-operative data as well as other data may
be utilized to determine the failure mode(s) of the implant, and an
implant design approach can be tailored to desirably alleviate or
account for such potential failure after implantation of the
revision implant. Where such failure has been due to long term
repetitive wear, the revision implant and associated surgical
procedure could be chosen to "correct" of modify such loading in
the joint, or the implant/procedure could be modified to increase
the ability of the implant to withstand such loads and/or wear,
such as by thickening the implant dimensions and/or utilizing
harder or more durable materials. Similar design changes could be
utilized where patient implants have failed due to excessive
stress, such as where the patient participates in particular
high-impact sports or the like. Such "improved implants" might
require additional or differing anatomical support (i.e., a larger
joint space to accommodate a thicker implant, potentially requiring
some additional bone resection in various regions), which could
alter the anticipated surgical procedure, but potentially result in
an implant having a significantly better long-term outcome than one
not tailored to accommodate specific loading conditions and/or
real-world performance. Various embodiments contemplate the use of
such additional modeling data in implant design, as well as design
of surgical tools and jigs to facilitate the implantation of such
implant.
[0016] The various embodiments of systems, devices and methods
discussed herein can also desirably utilize pre-operative data to
assess and potentially accommodate unusual and/or unexpected
anatomical situations, such as ideal alignment with the articular
surfaces and the resultant joint congruity. Poor alignment and poor
joint congruity can, for example, lead to instability of the joint.
In the knee joint, instability typically manifests as a lateral
instability of the joint. Lateral instability may manifest itself
in various ways, including pain, loosening of the implant and/or
excessive wear and/or implant failure.
[0017] There is also a need for tools that increase the accuracy of
positioning of a revision implant as well as increasing the
accuracy of cuts made to the bone in a joint in preparation for
surgical implantation of, for example, a revision system for
replacing a failed artificial joint implant. This disclosure
provides novel devices and methods for replacing a portion (e.g.,
diseased area and/or area slightly larger than the diseased area)
of a patient's joint (e.g., cartilage and/or bone) with a
non-pliable, non-liquid (e.g., hard) implant material, where the
implant achieves a near anatomic fit with the surrounding
structures and tissues of the patient's joint. In cases where the
devices and/or methods include an element associated with the
underlying articular bone, this disclosure also provides that the
bone-associated element achieves a near anatomic alignment with the
subchondral bone. This disclosure also provides for the preparation
of an implantation site with one or more bone cuts/resections,
e.g., a single cut, a few relatively small cuts, one or more
chamfer cuts. This disclosure also provides for the preparation of
an implantation site with other modifications, such as burring or
reaming of the articular surface or underlying bone.
[0018] In various aspects, this disclosure includes a method for
providing joint or articular replacement material, the method
comprising the step of producing articular replacement material of
selected dimensions (e.g., size, thickness and/or curvature).
[0019] In another aspect, this disclosure includes a method of
making joint replacement implants, the method comprising the steps
of (a) measuring the dimensions (e.g., thickness, curvature and/or
size) of the intended implantation site or the dimensions of the
area surrounding the intended implantation site; and (b) providing
replacement material that conforms to the measurements obtained in
step (a). In certain aspects, step (a) comprises measuring the
thickness of the cartilage surrounding the intended implantation
site and measuring the curvature of the cartilage surrounding the
intended implantation site. In other embodiments, step (a)
comprises measuring the size of the intended implantation site and
measuring the curvature of the cartilage surrounding the intended
implantation site. In other embodiments, step (a) comprises
measuring the thickness of the cartilage surrounding the intended
implantation site, measuring the size of the intended implantation
site, and measuring the curvature of the cartilage surrounding the
intended implantation site. In other embodiments, step (a)
comprises reconstructing the shape of healthy cartilage surface at
the intended implantation site. Various embodiment include similar
measurements and modeling of "failed implant" components and
surrounding anatomical structures in planning and designing of
revision implants and other replacement materials.
[0020] In any of the methods described herein, one or more
components of the articular replacement material (e.g., the
implant) can be non-pliable, non-liquid, solid or hard. The
dimensions of the replacement material can be selected following
intraoperative measurements. Measurements can also be made using
imaging techniques such as ultrasound, MRI, CT scan, x-ray imaging
obtained with x-ray dye and fluoroscopic imaging. A mechanical
probe (with or without imaging capabilities) can also be used to
select dimensions, for example an ultrasound probe, a laser, an
optical probe and a deformable material or device.
[0021] In any of the methods described herein, the revision implant
can be designed and made for an individual patient, or selected
(for example, from a pre-existing library of repair systems), grown
from cells and/or hardened from various materials. Furthermore, in
any of the methods described herein the implant, e.g., a pre-made
or pre-existing implant selected for a patient, can also be shaped
(e.g., manually, automatically or by machine), for example using
mechanical abrasion, laser ablation, radiofrequency ablation,
cryoablation and/or enzymatic digestion, as well as material
additive technologies including laser sintering, welding, adhering,
etc. In any of the methods described herein, the various materials
can comprise synthetic materials (e.g., metals, liquid metals,
polymers, alloys or combinations thereof) or biological materials
such as stem cells, fetal cells or chondrocyte cells.
[0022] In yet another aspect, this disclosure provides a method of
determining the curvature of an articular surface, the method
comprising the step of intraoperatively measuring the curvature of
the articular surface using a mechanical probe. The articular
surface can comprise cartilage and/or subchondral bone. In a still
further aspect, this disclosure provides a method of producing an
articular replacement material comprising the step of providing an
articular replacement material that conforms to the measurements
obtained by any of the methods of described herein.
[0023] In yet another aspect, an articular repair system comprising
(a) cartilage replacement material, wherein said cartilage
replacement material has a curvature similar to surrounding,
adjacent, underlying or opposing cartilage; and (b) at least one
non-biologic material, wherein said articular surface repair system
comprises a portion of the articular surface equal to, smaller
than, or greater than, the weight-bearing surface that is provided.
In certain embodiments, the cartilage replacement material is
non-pliable (e.g., hard hydroxyapatite, etc.). In certain
embodiments, the system exhibits biomechanical (e.g., elasticity,
resistance to axial loading or shear forces) and/or biochemical
properties similar to articular cartilage. The first and/or second
component can be bioresorbable and, in addition, the first or
second components can be adapted to receive injections.
[0024] Any of the repair systems or prostheses described herein
(e.g., the external surface) can comprise a polymeric material, for
example attached to said metal or metal alloy. Any of the repair
systems can be entirely composed of polymer. Further, any of the
systems or prostheses described herein can be adapted to receive
injections, for example, through an opening in the external surface
of said cartilage replacement material (e.g., an opening in the
external surface terminates in a plurality of openings on the bone
surface). Bone cement, polymers, Liquid Metal, therapeutics, and/or
other bioactive substances can be injected through the opening(s).
In certain embodiments, bone cement is injected under pressure in
order to achieve permeation of portions of the marrow space with
bone cement, such as through, for example, a fenestrated stem or
cannulated screw. In addition, any of the repair systems or
prostheses described herein can be anchored in bone marrow or in
the subchondral bone itself. One or more anchoring extensions
(e.g., pegs, pins, etc.) can extend through the bone and/or bone
marrow. Any anchoring extensions, e.g., pegs or pins, can be porous
or porous coated, e.g., to facilitate bone in-growth.
[0025] In another aspect, a method of designing an articular
implant comprising the steps of obtaining multiple images of a
joint, of an associated implant and/or combinations thereof. In
various embodiments the images can be from multiple angles and/or
at different times during the patient's treatment history. The
images can be cross-referenced and evaluated against each other as
well as against non-patient database information (such as, for
example, a database of normalized individuals from a general or
specific population group), and a resulting output of the patient's
anatomical features and/or estimated anatomical features can be
provided. The output may then be used to design appropriate
surgical tools, jig and implants for use in surgical repair of the
failed implant. The images can include, for example, an
intraoperative image including a surface detection method using any
techniques known in the art, e.g., mechanical, optical, ultrasound,
and known devices such as MRI, CT, ultrasound, digital
tomosynthesis and/or optical coherence tomography images.
[0026] In yet another aspect, described herein are systems for
evaluating the fit of an articular repair system into a joint, the
systems comprising one or more computing means capable of
superimposing a three-dimensional (e.g., three-dimensional
representations of at least one articular structure and of the
articular repair system) or a two-dimensional cross-sectional image
(e.g., cross-sectional images reconstructed in multiple planes) of
a joint and an image of an articular repair system to determine the
fit of the articular repair system (including revision systems).
The computing means can be: capable of merging the images of the
joint and the articular repair system into a common coordinate
system; capable of selecting or designing an articular repair
system having the best fit; capable of rotating or moving the
images with respect to each other; and/or capable of highlighting
areas of poor alignment between the articular repair system and the
surrounding articular surfaces. The three-dimensional
representations can be generated using a parametric surface
representation. The system may perform multiple steps
automatically, in response to user intervention, or any combination
thereof.
[0027] In yet another aspect, surgical tools for preparing a joint
to receive an implant are described, for example a tool comprising
one or more surfaces or members that conform at least partially to
the shape of the articular surfaces of the joint (e.g., a femoral
condyle and/or tibial plateau of a knee joint), of non-joint
anatomy (e.g., femoral neck features), of opposing joint surfaces
and/or of relevant articular or non-articular surfaces of the
"failed implant" or implant component. For example, a surface or at
least a portion of a surface of a surgical tool as described herein
has a shape that is substantially a negative of a portion of a
surface of the joint, which can be a portion of an articular
surface, a portion of non-articular or non-joint surface, etc.
[0028] In certain embodiments, the tool comprises Lucite silastic
and/or other polymers or suitable materials. The tool can be
re-useable or single-use. The tool may be made from one or more
biodegradable materials such that, for example, a single-use tool
can be readily disposed of without any significant, additional
medical waste. The tool can be comprised of a single component or
multiple components. In certain embodiments, the tool comprises an
array of adjustable, closely spaced pins. In any embodiments
described herein, the surgical tool can be designed to further
comprise an aperture or guide therein, for example one or more
apertures or guides having dimensions (e.g., diameter, depth, etc.)
smaller or equal to one or more dimensions of the implant and/or
one or more apertures or guides. Such apertures or guides can
direct and/or control movement of one or more surgical instruments,
e.g., a surgical saw, drill, reamer or broach. Such apertures or
guides can be adapted to receive one or more injectables. Any of
the tools described herein can further include one or more curable
(hardening) materials or compositions, for example that are
injected through one or more apertures in the tool and which
solidify to form an impression of the articular surface.
[0029] In still another aspect, a method of evaluating the fit of
an articular or joint repair system into a joint is described
herein, the method comprising obtaining one or more
three-dimensional images (e.g., three-dimensional representations
of at least one articular structure and of the articular repair
system) or two-dimensional cross-sectional images (e.g.,
cross-sectional images reconstructed in multiple planes) of a
joint, wherein the joint includes at least one defect or diseased
area and optionally a failed or failing implant or component(s)
thereof; obtaining one or more images of one or more articular
repair systems designed to repair the defect or diseased area; and
evaluating the images to determine the articular repair system that
best fits the defect (e.g., by superimposing the images to
determine the fit of the articular repair system into the joint).
In certain embodiments, the images of the joint and the articular
repair system are merged into a common coordinate system. The
three-dimensional representations can be generated using a
parametric surface representation. In any of these methods, the
evaluation can be performed by manual visual inspection and/or by
computer (e.g., automated). The images can be obtained, for
example, using a C-arm system and/or radiographic contrast.
[0030] In accordance with another embodiment, a surgical tool
includes a template. The template has at least one contact surface
for engaging a surface associated with a joint and/or surface of a
"failed implant" or component(s) thereof. The at least one contact
surface substantially conforms with the underlying surface(s). For
example, at least a portion of the at least one contact surface
includes a shape that is substantially a negative of at least a
portion of the underlying surface(s). The at least one contact
surface is optionally substantially transparent or
semi-transparent. The template further includes at least one guide
aperture for directing movement of a surgical instrument, e.g., a
saw, drill, reamer or broach.
[0031] In accordance with related embodiments, the surface may be
an articular surface, a non-articular surface, a cartilage surface,
a weight bearing surface, a non-weight surface, a bone surface
and/or a surface of an existing implant, implant component and/or
"failed implant." The joint has a joint space, with the surface
either within the joint space or external to the joint space. The
template may include a mold. The template may include at least two
pieces, the at least two pieces including a first piece that
includes one or more of the at least one contact surfaces, the
second piece including one or more of the at least one guide
apertures or guide surfaces. The at least one contact surface may
include a plurality of discrete contact surfaces.
[0032] In still further embodiments, the template may include a
reference element, such as a pin or aiming device, for establishing
a reference plane relative to at least one of a mechanical axis and
an anatomical axis of a limb. In other embodiments, the reference
element may be used for establishing an axis to assist in
correcting an axis deformity.
[0033] In accordance with another embodiment, a method of joint
arthroplasty is provided. The method includes obtaining images of a
joint and/or joint implant, wherein the image(s) includes surfaces
associated with the joint and/or joint implant. A template is
created having at least one contact surface that conforms with the
surface(s). The template includes at least one guide aperture or
guide surface or element for directing movement of a surgical
instrument. The template is positioned such that the contact
surface abuts the surface(s) in a predefined orientation.
[0034] In related embodiments of the invention, the joint surface
is at least one of an articular surface, a non-articular surface, a
cartilage surface, a weight bearing surface, a non-weight bearing
surface, a bone surface and/or a surface of an existing implant,
implant component and/or "failed implant." The joint has a joint
space, wherein the surface may be within the joint space or
external to the joint space. The at least one contact surface may
include a plurality of discrete contact surfaces. Creating the
template may include rapid prototyping, milling and/or creating a
mold, the template furthermore may be sterilizable and/or
biocompatible. The rapid prototyping may include laying down
successive layers of plastic. The template may be a multi-piece
template. The multi-piece template may include a first piece that
includes one or more of the at least one contact surfaces, and a
second piece that includes one or more of the at least one guide
apertures or guide surface or element. Obtaining the image may
include determining dimensions of bone underlying the cartilage,
and adding a predefined thickness to the bone dimensions, the
predefined thickness representing the cartilage thickness. Adding
the predefined thickness may be a function of at least one of an
anatomic reference database, an age, a gender, and race matching.
Obtaining the imaging may include performing an optical imaging
technique, an ultrasound, a CT, a spiral CT, and/or an MRI.
[0035] In further related embodiments, the method may further
include anchoring the contact surface to the cartilage. The
anchoring may include using at least one of k-wire and adhesive.
The anchoring may include drilling a bit through the cartilage, and
leaving the bit in place. The anchoring may include forming the
template to normal joint surface, arthritic joint surface or the
interface between normal and arthritic joint surface or
combinations thereof.
[0036] In still further related embodiments, the template may
include a reference element. The method may include establishing,
via the reference element, a reference plane relative to at least
one of a mechanical axis and an anatomical axis of a limb. The
mechanical axis may extend from a center of a hip to a center of an
ankle. Alternatively, an axis may be established via the reference
element that is used to align surgical tools in correcting an axis
deformity.
[0037] In further related embodiments, the method further includes
performing at least one of a muscle sparing technique and a bone
sparing technique. An incision for inserting the template may be
equal to or less than one of 15 cm, 13 cm, 10 cm, 8 cm, and 6 cm.
At least a portion of the template may be sterilized. Sterilizing
may include heat sterilization and/or sterilization using gas. The
sterilized portion may include a mold.
[0038] In accordance with another embodiment, a method of joint
arthroplasty is presented. The method includes obtaining image(s)
associated with a joint. A template is created having at least one
contact surface that conforms with a surface associated with the
joint or "failed implant" and/or component(s) thereof, the template
including a reference element and at least one guide aperture or
guide surface or element for directing movement of a surgical
instrument. The template is aligned in an orientation on the joint
such that the reference element establishes a reference plane
relative to a mechanical axis of a limb. The template is anchored
to the joint/implant such that the contact surface abuts the joint
in said orientation. The mechanical axis may extend, for example,
from a center of a hip to a center of an ankle. A surgical tool may
be aligned using the reference element to correct an axis
deformity.
[0039] In accordance with still another embodiment, a surgical tool
includes a template. The template includes a mold having at least
one contact surface for engaging a joint and/or "failed implant"
surface. The at least one contact surface substantially conforms
with the underlying surface(s). The mold is made of a biocompatible
material. Furthermore, the mold is capable of heat sterilization
without deforming. The template includes at least one guide
aperture or guide surface or guide element for directing movement
of a surgical instrument and/or reference marker (i.e., alignment
pin, etc). In accordance with related embodiments, the mold may be
capable of heat sterilization without deformation. The contact
surface may be made of polyphenylsulfone.
[0040] In accordance with related embodiments, the method may
further include using the second template to direct a surgical cut
on the tibia. Anchoring the second template may occur subsequent or
prior to anchoring the first template. At least one of the first
and second templates may include a mold. The first contact surface
may substantially conform with the femoral joint surface. The
second contact surface may substantially conform with the tibial
joint surface.
[0041] In accordance with another embodiment, a method of
performing joint arthroplasty includes obtaining a first image
associated with a first joint, obtaining a second image of a second
joint, and optionally obtaining a third image of a third joint. A
mechanical axis associated with the first joint and the second
joint and optionally the third joint is determined. A template is
provided for enabling surgery to correct an anatomic abnormality
associated with at least one of the first, second and/or third
joint.
[0042] In another embodiment, gait, loading and other physical
activities as well as static positions of a joint may be simulated
using a computer workstation. The template and the resultant
surgical procedures, e.g. cuts, drilling, rasping, can be optimized
using this information to achieve an optimal functional result. For
example, the template and the resultant implant position may be
optimized for different degrees of flexion and extension, internal
or external rotation, abduction or adduction. Thus, the templates
may be used to achieve motion that is optimized in one, two or more
directions.
[0043] In accordance with related embodiments, the template may
include at least one contact surface for engaging a surface
associated with the first joint, the second joint and/or the third
joint, the at least one contact surface substantially conforming
with the surface. The template may include at least one guide
aperture or guide surface or guide element for directing movement
of a surgical instrument.
[0044] In further related embodiments, obtaining the first image
may include imaging one of at least 5 cm, at least 10 cm, at least
15 cm, at least 20 cm, at least 25 cm, at least 30 cm, and at least
35 cm beyond the first joint. Obtaining the first image/and or
second image and/or the third image may include performing a CT or
an MRI. Performing the MRI may include obtaining a plurality of MRI
scans. Optionally, two or more imaging modalities can be used and
information obtained from the imaging modalities can be
combined.
[0045] In accordance with another embodiment, a method of
performing joint arthroplasty includes obtaining and/or deriving
(using various methods described herein) a computer image of a
surface associated with a first joint. At least one deformity seen
in the computer image is removed pertaining to the surface, so as
to form an improved anatomic or functional result. The at least one
deformity is removed from the surface to create a modified surface.
A template is provided based, at least in part, on the removal of
the deformity. The template includes at least one contact surface
for engaging the modified surface, the at least one contact surface
substantially conforming with the modified surface.
[0046] In accordance with another embodiment, a method of
performing joint arthroplasty includes obtaining a computer image
of a surface associated with a first joint. At least one deformity
seen in the computer image is removed and/or evaluated such as a
biomechanical or anatomical axis deformity, so as to form an
improved anatomic or functional result. The at least one deformity
is removed in the surgical planning by modifying the shape or
position of a template including the shape and/or position of guide
apertures, guide surface or guide elements. A template is provided
based, at least in part, on the removal of the deformity. The
template includes at least one contact surface for engaging the
joint surface. The shape and/or position of guide apertures, guide
surface or guide elements is selected or designed to achieve a
correction of the deformity.
[0047] In accordance with related embodiments, the template may be
used in a surgical procedure. The template may include at least one
guide aperture, guide surface or guide elements, the method further
including using the at least one guide aperture, guide surface or
guide elements to direct movement of a surgical instrument. The at
least one deformity may include a osteophyte, a subchondral cyst,
and/or an arthritic deformation.
[0048] In accordance with another embodiment, a method of
performing joint arthroplasty includes obtaining an image of a
surface associated with a first joint, the image including at least
one deformity. A template is provided, based at least in part on
the image, the template having at least one contact surface for
engaging portions of the surface free of the deformity. The at
least one contact surface substantially conforms with the portions
of the surface. The template is used in a surgical procedure.
[0049] In accordance with related embodiments, the template may
include at least one guide aperture, guide surface or guide
elements, the method further including using the at least one guide
aperture, guide surface or guide elements to direct movement of a
surgical instrument. The at least one deformity may include a
osteophyte, a subchondral cyst, and/or an arthritic
deformation.
[0050] In accordance with another embodiment, a method of
performing joint arthroplasty includes obtaining an image of a
surface associated with a joint and/or "failed implant," the image
including at least subchondral bone. A template is provided, based
at least in part on the image. The template includes at least one
contact surface substantially conforming with the subchondral bone
and/or a surface of the "failed implant." Residual cartilage is
removed from the bone surface in areas where the at least one
contact surface is to contact the subchondral bone. The template is
positioned such that the at least one contact surface abuts the
subchondral bone and/or "failed implant" surface in a predefined
orientation.
[0051] In accordance with another embodiment, a method of
performing joint arthroplasty includes providing a template. The
template is fixated to bone and/or "failed implant" surface(s)
associated with a joint without performing any cuts to the joint.
The template may be used in a surgical procedure.
[0052] In accordance with related embodiments, fixating may include
drilling into the bone and leaving a drill bit in the bone. An
image of a surface associated with a joint may be obtained, the
template having at least one contact surface that conforms with the
surface.
[0053] A method of placing an implant into a joint is also
provided. The method comprises the steps of imaging the joint using
a C-arm system, obtaining a cross-sectional image with the C-arm
system, and utilizing the image for placing the implant into a
joint.
[0054] In accordance with another embodiment, a system for joint
arthroplasty includes a first template. The first template includes
at least one surface for engaging a first surface of a joint, the
surface including a portion that substantially conforms to, matches
or has a shape that is substantially a negative of one or more
portions or all of the first surface. The first template further
includes at least one guide for directing movement of a surgical
instrument. A linkage cross-references at least one surgical tool
relative to said guide and relative to one of an anatomical and a
mechanical axis.
[0055] In accordance with related embodiments, the surgical tool
may be a second template, the second template including at least
one guide for directing movement of a surgical instrument. The
second template may include a surface that includes a portion that
substantially conforms to at least a portion of a second joint
surface. The second joint surface may oppose the first joint
surface. At least one guide of the second template may direct the
surgical instrument in at least one of a cut, a milling, and a
drilling oriented in a predefined location relative to said first
template and adapted in shape, size or orientation to an implant
shape. The shape and/or position of the at least one guide of the
first template may be based, at least in part, on one or more axis
related to said joint. The linkage may be an attachment mechanism,
which may cause the first template to directly contact the at least
one surgical tool, or alternatively, attaches the first template
and the at least one surgical tool such that the first template and
the at least one surgical tool do not directly contact each other.
The linkage may allow for rotation relative to one of an anatomical
and a mechanical axis. The first template may include a removably
attached block, the block including the at least one guide of the
first template.
[0056] In accordance with another embodiment, a system for joint
arthroplasty is presented that includes a first template. The first
template includes at least one surface for engaging a first surface
of a joint, the surface including a portion that substantially
conforms to one or more portions or all of the first surface. The
first template further includes at least one guide for directing
movement of a surgical instrument. A linkage cross-references at
least one surgical tool on a second surface of the joint opposing
the first surface.
[0057] In accordance with another embodiment, a system for joint
arthroplasty is presented that includes a first template. The first
template includes at least one first template surface for engaging
a first surface of a joint and/or "failed implant," the first
template surface substantially conforming to, matching, or having a
shape that is substantially a negative of one or more portions or
all of the first surface. The first template further includes at
least one guide for directing movement of a surgical instrument. A
second template includes at least one second template surface for
engaging a second surface of a joint. In certain embodiments, the
second template includes at least a surface portion that
substantially conforms to, matches, or has a shape that is
substantially a negative of one or more portions or all of the
second anatomical surface or "failed implant" surface. In certain
embodiments, the second template includes at least a surface
portion that engages at least a portion of the first template
through an attachment or engagement mechanism, e.g., a snap fit or
telescopic engagement. The second template further includes at
least one guide for directing movement of a surgical instrument. In
certain embodiments, a linkage cross-references the first template
and the second template.
[0058] In accordance with another embodiment, a system for joint
arthroplasty includes a first template. The first template includes
at least one surface for engaging a first surface of a joint and/or
"failed implant," the surface substantially conforming to,
matching, or having a shape that is substantially a negative of one
or more portions or all of the first surface. The first template
further includes at least one guide for directing movement of a
surgical instrument. A linkage cross-references at least one
surgical tool, wherein the linkage allows for rotation and/or other
movement relative to one of an anatomical and a mechanical axis
associated with the joint.
[0059] In accordance with another embodiment, a method of joint
arthroplasty includes positioning at least one contact surface of a
first template onto a first surface of a joint or failed implant. A
second template is cross-referenced to the first template to align
position of the second template on a second surface of the joint,
the second template including at least one guide. Movement of the
surgical instrument is directed using the at least one guide of the
second template relative to said guide and relative to one of an
anatomical and a mechanical axis.
[0060] In accordance with related embodiments, the at least one
contact surface of the first template substantially conforms to,
matches, or has a shape that is substantially a negative of at
least a portion of the first surface and/or failed implant surface.
The method may further include obtaining electronic image data of
the joint, and determining a shape of the at least one contact
surface of the first template based, at least in part, on
electronic image data.
[0061] In accordance with other related embodiments, the method may
further include, prior to directing movement of the surgical
instrument, positioning at least one contact surface of the second
template to the second joint surface. The at least one contact
surface of the second template may substantially conform to, match,
or have a shape that is substantially a negative of one or more
portions or all of the second surface. The method may further
include obtaining electronic image data of the joint, and
determining a shape of the at least one contact surface of the
second template based, at least in part, on electronic image
data.
[0062] In accordance with yet further related embodiments,
cross-referencing the second template to the first template may
includes attaching the second template to the first template.
Attaching the second template to the first template may include
performing intraoperative adjustments. The second template is
attached to the first template via a pin, and wherein performing
intraoperative adjustments include rotating the second template
around the pin. The method may further include performing an
intraoperative adjustment on the position of the second template on
the second surface of the joint, wherein performing the
intraoperative adjustment includes using one of spacers, ratchets,
and telescoping devices. The method may further include performing
an intraoperative adjustment on the position of the second template
on the second surface of the joint, wherein performing the
intraoperative adjustment includes adjusting for at least one of
joint flexion, joint extension, joint abduction, and joint
rotation. Directing movement of the surgical instrument using the
at least one guide of the second template may include making one or
more cuts or drill holes, the method further comprising implanting
a joint prosthesis as a function of the one or more cuts or drill
holes. The first template may include at least one guide, the
method further comprising directing movement of a surgical
instrument using the at least one guide of the first template.
Directing movement of the surgical instrument using the at least
one guide of the first template may include making one or more cuts
or drill holes, the method further comprising implanting a joint
prosthesis as a function of the one or more cuts or drill holes.
Directing movement of the surgical instrument using the at least
one guide of the second template may include making at least one of
a cut, a drill hole, and a reaming, the method further comprising
implanting a joint prosthesis.
[0063] In still further related embodiments, the first surface of
the joint may be a femoral surface, and the second surface of the
joint may be a tibial surface (or surfaces of implant components
attached thereto). The method may further include obtaining
electronic image data of a joint, determining the at least one of a
mechanical axis and an anatomical axis of the joint based, at least
in part, on the electronic image data, wherein the shape and/or
position of the guide of the second template is based, at least in
part, on the at least one of the mechanical axis and the anatomical
axis. The electronic image data may be obtained pre-operatively,
intraoperatively, optically, an MRI, a CT, and/or a spiral CT. The
first template may include a thickness based, at least in part, on
at least one of a thickness of an implant to be attached to the
first surface of the joint or implant and a desired space between
two opposing surfaces of the joint.
[0064] In accordance with another embodiment, a method of joint
arthroplasty includes positioning at least one contact surface of a
first template onto a first surface of a joint and/or implant. A
second template is cross-referenced to the first template to align
position of the second template on a second surface of the joint,
the second surface opposing the first surface. The second template
includes at least one guide. Movement of the surgical instrument is
directed using the at least one guide of the second template.
[0065] In accordance with another embodiment, a method of joint
arthroplasty includes positioning at least one contact surface of a
first template onto a first surface of a joint, wherein the at
least one contact surface of the first template includes a portion
that substantially conforms to at least a portion of the first
surface of the joint. A second template is cross-referenced to the
first template to align position of the second template onto a
second surface of the joint, the at least one contact surface of
the second template includes a portion that substantially conforms
to at least a portion of the second surface of the joint. The
second template includes at least one guide. Movement of the
surgical instrument is directed using the at least one guide of the
second template.
[0066] In accordance with another embodiment, a method of joint
arthroplasty includes positioning at least one contact surface of a
first template onto a first surface of a joint. A second template
is cross-referenced to the first template to align position of the
second template on a second surface of the joint, the second
template including at least one guide. Cross-referencing allows
rotation of the second template relative to one of a biomechanical
and an anatomical axis. Movement of the surgical instrument is
directed using the at least one guide of the second template.
[0067] In accordance with another embodiment, a method of joint
arthroplasty includes obtaining electronic image data of a joint,
and determining width space of the joint based, at least in part,
on the electronic image data. A template is provided that includes
at least one guide for directing movement of a surgical instrument,
wherein at least one of the shape and position of the guide is
based, at least in part, on the width space of the joint.
[0068] In accordance with related embodiment, the template may
include at least one surface for engaging a surface of a joint, the
at least one surface of the template substantially matches,
conforms to, or has a shape that is substantially a negative of at
least a portion or all of the surface of the joint. Obtaining
electronic image data may include at least one of a CT scan, MRI
scan, optical scan, and a ultrasound imaging. Obtaining electronic
image data may include obtaining image data of a medial space, a
lateral space, anterior space, and/or posterior space of the joint.
At least two of the lateral space, anterior space, and posterior
space of the joint may be compared. Obtaining image data may be
performed in two dimensions or three dimensions, and may include
assessment, evaluation, cross-referencing and correction of data
from multiple image sources and/or from images of the joint and/or
implant from different periods of time or at different times in the
patient's treatment regime. Determining width of the joint may
include measuring the distance from the subchondral bone plate of
one articular surface to the subchondral bone plate of the opposing
articular surface. Alternatively, determining width of the joint
may include measuring the distance from the subchondral bone plate
of one articular surface to the subchondral bone plate of the
opposing articular surface. Obtaining the image data of the joint
may be performed in at least one of joint flexion, joint extension,
and joint rotation. At least one of the shape and position of the
guide may be further based, at least in part, on the anatomical or
mechanical axis alignment of the joint.
[0069] In accordance with another embodiment, a method of joint
arthroplasty includes obtaining electronic image data of a joint,
and determining cartilage loss associated with the joint based, at
least in part, on the electronic image data. A template may be
provided that includes at least one guide for directing movement of
a surgical instrument so as to correct an axis alignment of the
joint, wherein at least one of the shape and position of the guide
is based, at least in part, on the cartilage loss. In a similar
manner, another method of joint arthroplasty includes obtaining
electronic image data of a joint and/or "failed implant," and
determining changes in cartilage and/or underlying bone support of
the anatomical support structure prior to planning and/or
performing a "revision" implantation procedure based, at least in
part, on the electronic image data.
[0070] In accordance with related embodiments, the method may
further include measuring at least one axis associated with the
joint. Measuring may include a standing x-ray, a weight bearing
x-ray, a CT scout scan, a MRI localizer scan, a CT scan, and/or a
MRI scan. Obtaining image data may include a spiral CT, spiral CT
arthography, MRI, optical imaging, optical coherence tomography,
and/or ultrasound. The template may include at least one contact
surface for engaging a surface of the joint and/or "failed
implant," at least a portion of the contact surface substantially
conforms to or matches one or more portions or all of the
joint/implant surface.
[0071] In accordance with another embodiment, a method for joint
arthroplasty includes obtaining electronic image data of a joint,
and determining a plurality of measurements based, at least in
part, on the image data. The measurements may be selected from at
least one of an axis associated with the joint and a plane
associated with the joint. A template is provided that includes at
least one guide for directing movement of a surgical instrument,
wherein at least one of the shape and position of the guide is
based, at least in part, on the plurality of measurements.
[0072] In accordance with related embodiments, obtaining image data
of the joint may include an x-ray, a standing x-ray, a CT scan, an
MRI scan, CT scout scans, and/or MRI localizer scans. The plurality
of measurements may include a plurality of axis, a plurality of
planes, or a combination of an axis and a plane. The template may
include at least one contact surface for engaging a surface of a
joint, the at least one contact surface substantially conforms to,
matches or has a shape that is substantially a negative of one or
more portions or all of the joint surface.
[0073] In accordance with another embodiment, a surgical tool
includes a template having a surface for engaging a joint or
implant surface, and the template surface substantially conforms
to, matches or has a shape that is substantially a negative of one
or more portions or all of the joint or implant surface. The
template further includes two or more guides for directing movement
of a surgical instrument, wherein the shape and/or position of at
least one of the guides is based, at least in part, on at least one
axis related to said joint.
[0074] In accordance with related embodiments, the template further
includes a block removably attached to the surface(s), the block
including the two or more guides. The two or more guides may
include at least one guide for a cut, a milling, and a drilling. A
second surgical tool may be attached to the template, the second
tool including at least one guide aperture for guiding a surgical
instrument. At least one guide of the second surgical tool may
guide a surgical instrument to make cuts that are parallel,
non-parallel, perpendicular, or non-perpendicular to cuts guided by
the first template.
[0075] In accordance with another embodiment, a method of joint
arthroplasty includes performing an extended scan of a joint to
obtain electronic image data that includes the joint and at least
15 cm or greater beyond the joint. At least one of an anatomical
and a mechanical axis associated with the joint is determined
based, at least in part, on the electronic image data. A template
is provided that includes at least one guide for directing movement
of a surgical instrument, wherein at least one of the shape and
position of the guide is based, at least in part, on the at least
one of the anatomical and the mechanical axis.
[0076] In accordance with related embodiments, the joint may be a
knee joint, and performing the extended scan of a joint to obtain
electronic image data includes obtaining electronic image data at
least 15 cm, 20 cm, or 25 cm beyond the tibiofemoral joint
space.
[0077] In accordance with another embodiment, a method of joint
arthroplasty includes performing an imaging scan acquisition that
obtains electronic image data through more than one joint. At least
one of an anatomical axis and a mechanical axis associated with the
joint is determined based, at least in part, on the electronic
image data. A template is provided that includes at least one guide
for directing movement of a surgical instrument, wherein at least
one of the shape and position of the guide is based, at least in
part, on the at least one of the anatomical and the mechanical
axis.
[0078] In accordance with related embodiments, performing the
imaging acquisition includes performing a CT, MRI, an X-ray, and/or
a two-plane x-ray, wherein the CT and the MRI includes a slice,
spiral, and/or volume acquisition. The guide may direct the
movement of a surgical instrument to correct a varus deformity
and/or a valgus deformity.
[0079] In accordance with another embodiment, a method of joint
arthroplasty includes obtaining a first image of a joint in a first
plane, wherein the first image generates a first image volume. A
second image of a joint in a second plane is obtained, wherein the
second image generates a second image data volume. The first and
second image data volumes is combined to form a resultant image
data volume, wherein the resultant image data volume is
substantially isotropic. A template is provided based on the
resultant image data volume, the template including at least one
surface for engaging a first surface of a joint or implant, at
least a portion of the surface substantially conforming to or
matches (or having a shape that is substantially a negative of) one
or more portions or all of the first joint or implant surface. The
template further includes at least one guide for directing movement
of a surgical instrument.
[0080] In accordance with related embodiments, obtaining the first
image and the second image may includes a spiral CT, volumetric CT,
and/or an MRI scan.
[0081] In accordance with another embodiment, a method for joint
arthroplasty includes performing a first cut on a joint to create a
first cut joint surface. Performing the first cut includes
positioning at least one contact surface of a first template onto a
first surface of a joint and/or "failed implant" or component
thereof, the at least one contact surface having a shape that is
substantially a negative of the first surface of the joint and/or
"failed implant" or component thereof. The first template includes
a guide for directing movement of a surgical instrument to perform
the first cut. The first cut is cross-referenced to perform a
second cut associated with an opposing surface of the joint.
[0082] In accordance with related embodiments, cross-referencing
the first cut to make the second cut may include attaching a second
template to the first template so as to assist positioning at least
one contact surface of the second template onto a second surface of
the joint. The second template includes a guide for directing
movement of a surgical instrument to perform the second cut. The
second template may include at least one contact surface portion
that substantially conforms to, matches or has a shape that is
substantially a negative of at least a portion of the second
surface of the joint or a surface of an implant. Cross-referencing
the first cut to make the second cut may include positioning at
least one contact surface of a third template onto at least a
portion of the first cut surface, and attaching a second template
to the third template so as to position at least one contact
surface of the second template onto a second surface of the joint.
The at least one contact surface portion of the third template may
substantially conform to, match or have a shape that is
substantially a negative of the first cut surface. The first cut
may be a horizontal femoral cut, with the second cut being a
vertical femoral cut. The first cut may be femoral cut with the
second cut being a tibial cut. The first cut may be a femoral cut,
and the second cut is a patellar cut. The first cut may be an
acetabular reaming and the second cut is a femoral cut.
[0083] In accordance with another embodiment, a method for joint
arthroplasty includes positioning at least one contact surface of a
template onto a surface of a joint or implant, the at least one
contact surface substantially conforming to, matching or having a
shape that is substantially a negative of at least a portion of the
surface of the joint or implant. The template includes a guide for
directing movement of a surgical instrument. The first template is
stabilized onto the first surface.
[0084] In accordance with related embodiments, the method may
further include obtaining electronic image data of the joint, and
determining a shape of the at least one contact surface of the
first template based, at least in part, on electronic image data.
Stabilizing may include using k-wires, a screw, an anchor, and/or a
drill bit left in place on the joint. Stabilizing may include
positioning the contact surface on at least one or more concavities
and convexities on the joint or implant. Stabilizing may include
positioning the contact surface on at least one concavity and at
least convexity on the joint or implant. Stabilizing may include
positioning the contact surface, at least partially, on an
arthritic portion of the joint and/or "failed implant" or component
thereof. Stabilizing may include positioning the contact surface,
at least partially, on an interface between a normal and an
arthritic portion of the joint or implant. Stabilizing may include
positioning the contact surface, at least partially, on one or more
surfaces of the "failed implant." Stabilizing may include
positioning the contact surface, at least partially, against an
anatomic feature. The anatomic feature may be a trochlea, an
intercondylar notch, a medial condyle and a lateral condyle, a
medial trochlea and a lateral trochlea, a medial tibial plateau and
a lateral tibial plateau, a fovea capities, an acetabular fossa, a
tri-radiate cartilage, an acetabular wall, or an acetabular rim.
Positioning the contact surface on the surface of the joint may
include positioning the contact surface on, at least partially, a
normal portion of the joint. Determining the position of the guide
on the template may be based, at least in part, on ligament
balancing and/or to optimize at least one of flexion and extension
gap. The method may further include adjusting the position of the
guide relative to the joint intraoperatively, using for example, a
spacer, a ratchet device, and a pin that allows rotation.
[0085] In accordance with another embodiment, a method for joint
arthroplasty includes positioning at least one contact surface of a
template onto a surface of a patient's joint, such that the contact
surface, at least partially or a portion thereof, substantially
conforms to and rests on an interface between an arthritic and a
normal portion of the patient's joint surface. The template
includes a guide for directing movement of a surgical instrument. A
surgical intervention is made on the joint with the surgical
instrument based, at least in part, on the guide.
[0086] In accordance with another embodiment, a template includes
at least one contact surface for positioning onto a surface of a
joint, the contact surface at least partially or a portion thereof
having a shape that is substantially a negative of (or
substantially conforms to or matches) an interface between an
arthritic and a normal portion of the joint surface. A guide
directs movement of a surgical instrument.
[0087] In accordance with another embodiment, a method for joint
arthroplasty includes positioning at least one contact surface of a
template onto a surface of a joint, such that the contact surface,
at least partially, rests on, and is substantially a negative of
(or substantially conforms to or matches) of, an arthritic portion
of the joint surface. The template includes a guide for directing
movement of a surgical instrument. A surgical intervention is made
on the joint with the surgical instrument based, at least in part,
on the guide.
[0088] In accordance with another embodiment, a template includes
at least one contact surface for positioning onto a surface of a
joint, the contact surface at least partially being substantially a
negative of (or substantially conforms to or matches) of a normal
portion of the joint surface. The template includes a guide for
directing movement of a surgical instrument.
[0089] In accordance with another embodiment, a method for joint
arthroplasty includes performing a phantom scan of one of a MRI and
CT instrument. Using the one of the an MRI and CT instrument, a
scan on a joint is performed. A shape of the at least one contact
surface of the first template is determined, based, at least in
part, on the phantom scan and the scan of the joint and/or implant,
the at least one contact surface having at least a portion that
substantially matches (or conforms to or has a shape that is
substantially a negative of) at least a portion of the surface of
the joint or implant. The template includes a guide for directing
movement of a surgical instrument.
[0090] In accordance with related embodiments, the phantom scan may
be performed prior to the scan of the joint, the method further
comprising adjusting the one of the MRI and the CT instrument. The
phantom scan may be performed after performing the scan of the
joint, wherein the scan of the joint is optimized based on the
phantom scan.
[0091] In accordance with another embodiment, a method for joint
arthroplasty includes determining a desired femoral component
rotation for one of a uni-compartmental or total knee replacement.
A template is provided that includes at least one guide for
directing movement of a surgical instrument, attached linkage,
and/or tool. At least one of the shape and position of the guide is
based, at least in part, on the desired femoral component
rotation.
[0092] In accordance with related embodiments, determining the
desired femoral component rotation may include measuring one or
more anatomic axis and/or planes relevant to femoral component
rotation. The one or more anatomic axis and/or planes may be a
transepicondylar axis, the Whiteside line, and/or the posterior
condylar axis. The guide may direct a femoral cut, the method
further comprising rotating the template so that the femoral cut is
parallel to a tibial cut with substantially equal tension medially
and laterally applied from medial and lateral ligaments and soft
tissue.
[0093] In accordance with another embodiment, a method for joint
arthroplasty includes determining a desired tibial component
rotation for one of a uni- or bi-compartmental or total knee
replacement. A tibial template is provided that includes at least
one guide for directing movement of a surgical instrument, attached
linkage, and/or tool. At least one of the shape and position of the
guide is based, at least in part, on the desired tibial component
rotation.
[0094] In accordance with related embodiments, determining the
desired tibial component rotation may include measuring one or more
anatomic axis and/or planes relevant to tibial component rotation.
The one or more anatomic axis and/or planes may be at an
anteroposterior axis of the tibia, and/or the medial one-third of
the tibial tuberosity. The guide may direct a femoral cut, the
method further comprising rotating the template so that the femoral
cut is parallel to a tibial cut with substantially equal tension
medially and laterally applied from medial and lateral ligaments
and soft tissue.
[0095] In accordance with another embodiment, a method of hip
arthroplasty includes determining leg length discrepancy and
obtaining electronic image data of the hip joint. A template is
provided that includes at least one guide for directing movement of
a surgical instrument, attached linkage, and/or tool. The template
includes at least one contact surface that is substantially a
negative of (or substantially conforms to or matches) of at least a
portion of the femoral neck or femoral joint implant component,
wherein at least one of the shape and position of the template
and/or guide is based, at least in part, on the electronic image
data.
[0096] In accordance with related embodiments, determining leg
length discrepancy may include a standing x-ray of the leg, a CT
scout scan, a CT, and/or an MRI. The guide may assist a surgical
instrument in cutting the femoral neck.
[0097] In accordance with another embodiment, a method for joint
arthroplasty includes determining a desired femoral component
rotation for a hip. A template is provided that includes at least
one guide for directing movement of a surgical instrument, attached
linkage, and/or tool. At least one of the shape and position of the
guide is based, at least in part, on the desired femoral component
rotation.
[0098] In accordance with another embodiment, a method for joint
arthroplasty includes determining a desired acetabular component
rotation for a hip. An acetabular template is provided that
includes at least one guide for directing movement of a surgical
instrument, attached linkage, and/or tool. At least one of the
shape and position of the guide is based, at least in part, on the
desired acetabular component rotation.
[0099] In accordance with another embodiment, a method for joint
arthroplasty includes determining a desired humerus component
rotation for a shoulder. A template is provided that includes at
least one guide for directing movement of a surgical instrument,
attached linkage, and/or a tool. At least one of the shape and
position of the guide is based, at least in part, on the desired
humerus component rotation.
[0100] In accordance with another embodiment, a method for joint
arthroplasty includes providing a template that includes at least
one surface for engaging a surface of a joint or implant based, at
least in part, on substantially isotropic input data. The surface
includes at least a portion that has a shape that is substantially
a negative of one or more portions or all of the joint or implant
surface. The template includes at least one guide for directing
movement of a surgical instrument.
[0101] In related embodiments, said input data is acquired using
fusion of image planes, or substantially isotropic MRI and spiral
CT.
[0102] In any of the embodiments and aspects described herein, the
joint can be, without limitation, a knee, shoulder, hip, vertebrae,
elbow, ankle, foot, toe, hand, wrist or finger. Moreover, the
various embodiments described herein can assist in the assessment,
planning, evaluation and execution of repair and/or replacement
procedures for virtually any implant, including failed or failing
hip, shoulder, elbow, foot, toe, hand, wrist or finger, ankle or
knee implants as well as spinal implants such as fusion devices,
disc replacement devices (i.e., Charite or ProDisk) and/or pedicle
screws.
BRIEF DESCRIPTION OF THE DRAWINGS
[0103] The foregoing features of this disclosure will be more
readily understood by reference to the following detailed
description, taken with reference to the accompanying drawings, in
which:
[0104] FIG. 1A is a flowchart depicting various methods according
to various embodiments of this disclosure.
[0105] FIG. 1B is a flowchart depicting various alternative methods
according to various embodiments of this disclosure.
[0106] FIGS. 2A-H illustrate, in cross-section, various stages of
knee resurfacing, in accordance with various embodiments of this
disclosure. FIG. 2A shows an example of normal thickness cartilage
and a cartilage defect. FIG. 2B shows an imaging technique or a
mechanical, optical, laser or ultrasound device measuring the
thickness and detecting a sudden change in thickness indicating the
margins of a cartilage defect. FIG. 2C shows a weight-bearing
surface mapped onto the articular cartilage. FIG. 2D shows an
intended implantation site and cartilage defect. FIG. 2E depicts
placement of an exemplary single component articular surface repair
system. FIG. 2F shows an exemplary multi-component articular
surface repair system. FIG. 2G shows an exemplary single component
articular surface repair system. FIG. 2H shows an exemplary
multi-component articular surface repair system.
[0107] FIGS. 3A-E, illustrate, in cross-section, exemplary knee
imaging and resurfacing, in accordance with various embodiments of
the invention. FIG. 3A shows a magnified view of an area of
diseased cartilage. FIG. 3B shows a measurement of cartilage
thickness adjacent to the defect. FIG. 3C depicts placement of a
multi-component mini-prosthesis for articular resurfacing. FIG. 3D
is a schematic depicting placement of a single component
mini-prosthesis utilizing stems or pegs. FIG. 3E depicts placement
of a single component mini-prosthesis utilizing stems and an
opening for injection of bone cement.
[0108] FIGS. 4A-C, illustrate, in cross-section, other exemplary
knee resurfacing devices and methods, in accordance with various
embodiments of the invention. FIG. 4A depicts normal thickness
cartilage in the anterior and central and posterior portion of a
femoral condyle and a large area of diseased cartilage in the
posterior portion of the femoral condyle. FIG. 4B depicts placement
of a single component articular surface repair system. FIG. 4C
depicts a multi-component articular surface repair system.
[0109] FIGS. 5A-B show single and multiple component devices, in
accordance with various embodiments of the invention. FIG. 5A shows
an exemplary single component articular surface repair system with
varying curvature and radii. FIG. 5B depicts a multi-component
articular surface repair system with a second component that
mirrors the shape of the subchondral bone and a first component
closely matches the shape and curvature of the surrounding normal
cartilage.
[0110] FIGS. 6A-B show exemplary articular repair systems having an
outer contour matching the surrounding normal cartilage, in
accordance with various embodiments. The systems are implanted into
the underlying bone using one or more pegs.
[0111] FIG. 7 shows a perspective view of an exemplary articular
repair device including a flat surface to control depth and prevent
toggle; an exterior surface having the contour of normal cartilage;
flanges to prevent rotation and control toggle; a groove to
facilitate tissue in-growth, in accordance with one embodiment.
[0112] FIGS. 8A-D depict, in cross-section, another example of an
implant with multiple anchoring pegs, in accordance with various
embodiments. FIG. 8B-D show various cross-sectional representations
of the pegs: FIG. 8B shows a peg having a groove; FIG. 8C shows a
peg with radially-extending arms that help anchor the device in the
underlying bone; and FIG. 8D shows a peg with multiple grooves or
flanges.
[0113] FIG. 9A-B depict an overhead view of an exemplary implant
with multiple anchoring pegs and depict how the pegs are not
necessarily linearly aligned along the longitudinal axis of the
device, in accordance with various embodiments.
[0114] FIGS. 10A-E depict an exemplary implant having radially
extending arms, in accordance with various embodiments of the
invention. FIGS. 10B-E are overhead views of the implant showing
that the shape of the peg need not be conical.
[0115] FIG. 11A illustrates a femur, tibia and fibula along with
the mechanical and anatomic axes. FIGS. 11B-E illustrate the tibia
with the anatomic and mechanical axis used to create a cutting
plane along with a cut femur and tibia. FIG. 11F illustrates the
proximal end of the femur including the head of the femur.
[0116] FIG. 12 shows an example of a surgical tool having one
surface matching the geometry of an articular surface of the joint,
in accordance with one embodiment. Also shown is an aperture in the
tool capable of controlling drill depth and width of the hole and
allowing implantation of an insertion of implant having a press-fit
design.
[0117] FIG. 13 is a flow chart depicting various methods of this
disclosure used to create a mold for preparing a patient's joint
for arthroscopic surgery.
[0118] FIG. 14A depicts, in cross-section, an example of a surgical
tool containing an aperture through which a surgical drill or saw
can fit. The aperture guides the drill or saw to make the proper
hole or cut in the underlying bone. Dotted lines represent where
the cut corresponding to the aperture will be made in bone. FIG.
14B depicts, in cross-section, an example of a surgical tool
containing apertures through which a surgical drill or saw can fit
and which guide the drill or saw to make cuts or holes in the bone.
Dotted lines represent where the cuts corresponding to the
apertures will be made in bone.
[0119] FIGS. 15A-R illustrate tibial cutting blocks and molds used
to create a surface perpendicular to the anatomic axis for
receiving the tibial portion of a knee implant.
[0120] FIGS. 16A-O illustrate femur cutting blocks and molds used
to create a surface for receiving the femoral portion of a knee
implant. FIG. 16P illustrates an axis defined by the center of the
tibial plateau and the center of the distal tibia. FIG. 16Q shows
an axis defining the center of the tibial plateau to the femoral
head. FIGS. 16R and 16S show isometric views of a femoral template
and a tibial template, respectively. FIG. 16T illustrates a femoral
guide reference tool attached to the femoral template. FIG. 16U
illustrates a sample implant template positioned on the chondyle.
FIG. 16V is an isometric view of the interior surface of the sample
implant template, in accordance with an embodiment. FIG. 16W is an
isometric view of the tibial template attached to the sample
implant. FIG. 16X shows a tibial template that may be used, after
the tibial cut has been made, to further guide surgical tools. FIG.
16Y shows a tibial implant and femoral implant inserted onto the
tibia and femur, respectively, after the above-described cuts have
been made.
[0121] FIG. 17A-G illustrate patellar cutting blocks and molds used
to prepare the patella for receiving a portion of a knee
implant.
[0122] FIG. 18A-H illustrate femoral head cutting blocks and molds
used to create a surface for receiving the femoral portion of a
knee implant.
[0123] FIG. 19A-D illustrate acetabulum cutting blocks and molds
used to create a surface for a hip implant.
[0124] FIG. 20 illustrates a 3D guidance template in a hip joint,
wherein the surface of the template facing the joint includes a
portion that substantially matches at least a portion of the joint
that is not affected by the arthritic process.
[0125] FIG. 21 illustrates a 3D guidance template for an
acetabulum, wherein the surface of the template facing the joint
includes a portion that substantially matches at least a portion of
the joint that is affected by the arthritic process.
[0126] FIG. 22 illustrates a 3D guidance template designed to guide
a posterior cut using a posterior reference plane. The joint facing
surface of the template has a shape, at least in part, that is
substantially a negative of at least of portions of the joint that
are not altered by the arthritic process.
[0127] FIG. 23 illustrates a 3D guidance template designed to guide
an anterior cut using an anterior reference plane, in accordance
with one embodiment. The joint facing surface of the template
substantially matches or conforms to, at least in part, one or more
portions of the joint that are altered by the arthritic
process.
[0128] FIG. 24 illustrates a 3D guidance template for guiding a
tibial cut (not shown), wherein the tibia includes an arthritic
portion. The template is designed to avoid the arthritic process by
spanning across a defect or cyst.
[0129] FIG. 25 illustrates a 3D guidance template for guiding a
tibial cut. The interface between normal and arthritic tissue is
included in the shape of the template.
[0130] FIG. 26A illustrates a 3D guidance template wherein the
surface of the template facing the joint substantially conforms to
at least portions of the surface of a joint that is healthy or
substantially unaffected by the arthritic process. FIG. 26B
illustrates the 3D guidance template wherein the surface of the
template facing the joint substantially matches at least portions
of the surface of the joint that is healthy or substantially
unaffected by the arthritic process. The diseased area is covered
by the template, but the mold is not substantially in contact with
it. FIG. 26C illustrates the 3D guidance template wherein the
surface of the template facing the joint includes a portion having
a shape that is substantially a negative of one or more portions of
the surface of the joint that are arthritic. FIG. 26D illustrates
the 3D guidance template wherein the template closely mirrors the
shape of the interface between substantially normal or near normal
and diseased joint tissue.
[0131] FIGS. 27A-D show multiple molds with linkages on the same
articular surface (A-C) and to an opposing articular surface
(D).
[0132] FIG. 28 illustrates a deviation in the AP plane of the
femoral and tibial axes in a patient.
[0133] FIG. 29 is a flow diagram showing a method wherein measured
leg length discrepancy is utilized to determine the optimal cut
height of a femoral neck cut for total hip arthroplasty.
[0134] FIGS. 30A-C illustrate the use of 3D guidance templates for
performing ligament repair.
[0135] FIG. 31 shows an example of treatment of CAM impingement
using a 3D guidance template.
[0136] FIG. 32 shows an example of treatment of Pincer impingement
using a 3D guidance template.
[0137] FIG. 33 shows an example of an intended site for placement
of a femoral neck mold for total hip arthroplasty.
[0138] FIG. 34 shows an example of a femoral neck mold with handle
and slot.
[0139] FIG. 35 shows an example of a posterior acetabular approach
for total hip replacement.
[0140] FIG. 36 shows an example of a guidance mold used for reaming
the site for an acetabular cup.
DETAILED DESCRIPTION OF THE INVENTION
[0141] The following description is presented to enable any person
skilled in the art to make and use the invention. Various
modifications to the embodiments described will be readily apparent
to those skilled in the art, and the generic principles defined
herein can be applied to other embodiments and applications without
departing from the spirit and scope of this disclosure as defined
by the appended claims. Thus, this disclosure is not intended to be
limited to the embodiments shown, but is to be accorded the widest
scope consistent with the principles and features disclosed herein.
To the extent necessary to achieve a complete understanding of this
disclosure disclosed, the specification and drawings of all issued
patents, patent publications, and patent applications cited in this
application are incorporated herein by reference.
[0142] 3D guidance surgical tools, referred to herein as a 3D
guidance surgical templates, that may be used for surgical
assistance may include, without limitation, using templates, jigs
and/or molds, including 3D guidance molds. It is to be understood
that the terms "template," "jig," "mold," "3D guidance mold," and
"3D guidance template," shall be used interchangeably within the
detailed description and appended claims to describe the tool
unless the context indicates otherwise.
[0143] 3D guidance surgical tools that may be used may include
guide apertures. It is to be understood that the term guide
aperture shall be used interchangeably within the detailed
description and appended claims to describe both guide surface and
guide elements.
[0144] As will be appreciated by those of skill in the art, the
practice of this disclosure employs, unless otherwise indicated,
conventional methods of x-ray imaging and processing, x-ray
tomosynthesis, ultrasound including A-scan, B-scan and C-scan,
computed tomography (CT scan), magnetic resonance imaging (MRI),
optical coherence tomography, single photon emission tomography
(SPECT) and positron emission tomography (PET) within the skill of
the art. Such techniques are explained fully in the literature and
need not be described herein. See, e.g., X-Ray Structure
Determination: A Practical Guide, 2nd Edition, editors Stout and
Jensen, 1989, John Wiley & Sons, publisher; Body CT: A
Practical Approach, editor Slone, 1999, McGraw-Hill publisher;
X-ray Diagnosis: A Physician's Approach, editor Lam, 1998
Springer-Verlag, publisher; and Dental Radiology: Understanding the
X-Ray Image, editor Laetitia Brocklebank 1997, Oxford University
Press publisher. See also, The Essential Physics of Medical Imaging
(2.sup.nd Ed.), Jerrold T. Bushberg, et al.
[0145] This disclosure provides systems, methods and compositions
for repairing joints, particularly for repairing and/or replacing
implants and implant components previously implanted into a
patient's joint, as well as repairing articular cartilage and for
facilitating the integration of a wide variety of cartilage repair
materials into a subject. Among other things, the techniques
described herein allow for the customization of implants and
surgical tools to suit a particular subject, for example in terms
of size, thickness, shapes and/or curvatures. Desirably, such tools
can utilize and existing "failed implant" information and/or
surfaces as one or more anatomical reference points to assist in
the preparation, positioning and/or placement of a replacement
implant for repairing a patient's joint.
[0146] When the shape (e.g., size, thickness and/or curvature) of
the articular cartilage surface is an exact or near anatomic fit
with the non-damaged cartilage or with the subject's original
cartilage, the success of repair is enhanced. The repair material
can be shaped prior to implantation and such shaping can be based,
for example, on electronic images that provide information
regarding curvature or thickness of any "normal" cartilage
surrounding the defect and/or on curvature of the bone underlying
the defect. Thus, the current invention provides, among other
things, for minimally invasive methods for partial joint
replacement. The methods will require only minimal or, in some
instances, no loss in bone stock. Additionally, unlike with current
techniques, the methods described herein will help to restore the
integrity of the articular surface by achieving an exact or near
anatomic match between the implant and the surrounding or adjacent
cartilage and/or subchondral bone. Moreover, if the "failed
implant" only requires replacement of one or more individual failed
components, the procedure may be less invasive than a complete
joint removal and replacement, and could thus be accomplished in a
less-invasive and/or minimally-invasive fashion, desirably with
commensurately less recovery time.
[0147] The various embodiments described in the present disclosure
also contemplate the use of existing "failed implant" components or
portions thereof as anchoring mechanisms, attachment points,
anatomical reference structures and/or as components of the
"revision implant" ultimately used in repairing the patient's
joint. In some instances, components of the "failed implant" may be
useful for a myriad of reasons, including if the "failed" implant
component is well-fixed to the patient's anatomy and failure of the
original "failed" implant was due to other implant components. In a
similar manner, certain components of a partial-joint replacement
may be integrated into the revision system, either as a module or
component of the revision implant, or if the partial-joint
component is "encased" by the revision implant or otherwise used to
support the revision implant components. Similarly, well-secured
anchors or other components from a "failed implant" may be reused
to anchor the revision implant, if desired and available.
[0148] Advantages of this disclosure can include, but are not
limited to, (i) customization of joint repair, thereby enhancing
the efficacy and comfort level for the patient following the repair
procedure; (ii) eliminating the need for a surgeon to measure the
defect to be repaired intraoperatively in some embodiments; (iii)
eliminating the need for a surgeon to shape the material during the
implantation procedure; (iv) providing methods of evaluating
curvature of the repair material based on implant, bone or tissue
images or based on intraoperative probing techniques; (v) providing
methods of repairing joints with only minimal or, in some
instances, no loss in bone stock; and (vi) improving postoperative
joint congruity.
[0149] Thus, the methods described herein allow for the design and
use of joint repair material that more precisely fits the defect
(e.g., site of implantation) and, accordingly, provides improved
repair of the joint.
[0150] I. Assessment of Joints and Alignment
[0151] The methods and compositions described herein can be used to
treat defects resulting from disease of the cartilage (e.g.,
osteoarthritis), bone damage, cartilage damage, trauma, and/or
degeneration due to overuse or age. This disclosure allows, among
other things, a health practitioner to evaluate and treat such
defects. The size, volume and shape of the area of interest can
include only the region of cartilage that has the defect, but
preferably will also include contiguous parts of the cartilage
surrounding the cartilage defect.
[0152] As will be appreciated by those of skill in the art, size,
curvature and/or thickness measurements can be obtained using any
suitable technique. For example, one-dimensional, two-dimensional,
and/or three-dimensional measurements can be obtained using
suitable mechanical means, laser devices, electromagnetic or
optical tracking systems, molds, materials applied to the articular
surface that harden and "memorize the surface contour," and/or one
or more imaging techniques known in the art. Measurements can be
obtained non-invasively and/or intraoperatively (e.g., using a
probe or other surgical device). As will be appreciated by those of
skill in the art, the thickness of the repair device can vary at
any given point depending upon the depth of the damage to the
cartilage and/or bone to be corrected at any particular location on
an articular surface.
[0153] As illustrated in FIG. 1A, typically the process begins by
first obtaining one or more images of a patient's joint that
requires revision. This group of images will typically have a
series of images of the patient's current joint, which typically
includes various images of the "failed" or "failing" implant (i.e.,
"failed implant" images). If available, the groups of images will
desirably further include other images taken earlier in the
treatment progression of the failed joint, including (1) images of
the joint and/or implant taken between the time of original
implantation and "failure" of the prior implant (i.e., "pre-failure
implant" images), (2) images of the joint and/or implant taken at
the time of original implantation (i.e., "initial implantation"
images), (3) images taken prior to initial implantation of the
"failed implant" (i.e., "pre-implant work-up" images), and (4)
images taken prior to significant failure of the patient's natural
joint (i.e., "healthy joint" images). Various additional image
sources useful for this disclosure could include images of the
"failed implant", both pre and post-failure (i.e., "implant data"),
information or images regarding the types and locations of bone
cement and/or bony in-growth structures, and any other anatomical
data available regarding the patient, including resection surface
information, residual cartilage, osteophytes, osteolysis, and/or
information regarding injuries or disease states that may affect
joint and/or bone strength in any manner (i.e., osteoporosis,
arthritis, etc.). Where such additional image groups are readily
available, it may be desirable to include such information in the
current image group. Other sources of information could include
databases of non-patient individuals (i.e., information from
specific or general individuals, including normalized information,
from specific or general population groups).
[0154] Table 1 provides a non-exhaustive list of various data
sources and image characteristics particularly useful in practicing
the present invention:
TABLE-US-00001 TABLE 1 Exemplary Sources of Imaging Data Image
sources Current scan of patient's anatomy, including "failed
implant" and/or "failed anatomy" Time-lapse images or 4D images and
motion studies of "failed implant" Contrast enhanced studies of
"failed implant" Historical scans of patient's healthy joint
currently requiring revision Historical scans of patient's joint
prior to implantation of "failed implant" (pre-failure) Scans of
patients contra-lateral (opposing) healthy joint Scans and/or
databases of healthy individuals and/or "matched" individuals from
general population(s) Historical scans of "failed implant" after
initial implantation but pre-failure Images and/or data regarding
shape, size and features/configuration of "failed implant" (pre-
implantation as well as "follow-up" images and image series) Images
and/or data regarding locations of bone cement of other
non-biologic structures (i.e., anchors, pins, other implants, etc.)
Images and/or data regarding resection surfaces, unresected
surfaces, residual cartilage, osteophytes, osteolysis, bone cement,
or other anatomical features prior to implantation of the "failed
implant" Images or data or templates of implant components of
"failed implant", either obtained in vivo in the patient or, for
example, based on manufacturer's data, in 2D and 3D, including CAD
files or other electronic files
[0155] At any point in the various disclosed embodiment, the
quality and reliability of various images may be assessed for
accuracy, completeness, and are desirably "normalized" to a set
standard or standards to facilitate their use during subsequent
steps of the disclosed invention. It is desirable that images of
poor quality and/or low accuracy will desirably be identified and,
if of lesser utility, given a rating of "low confidence" and/or are
discarded. In a similar manner, higher quality images and/or those
of better accuracy may be given a "higher confidence" rating. If
desired, images may be processed and/or enhanced to improve the
usefulness of data contained therein, in a known manner.
[0156] If desired, the various images in the image group may be
evaluated and/or assessed or "cross-referenced" against one
another. For example, it may be advantageous to compare, contrast
and evaluate the various anatomical image groups over time (i.e.,
healthy joint, initial implantation, pre-failure implant, and/or
failed implant images) to determine disease progression and/or
estimate future disease progression. In a similar manner, it may be
advantageous to compare, contrast and evaluate the various implant
image groups over time (i.e., initial implantation, pre-failure
implant, and/or failed implant images) to determine and/or identify
implant failure modes (i.e., implant fracture, unacceptable or
uneven wear zones, dislocation, modular failures, etc.) or
underlying anatomical failure modes (i.e., underlying support
structure failure, soft tissue disease, kinematic imbalances,
tissue scarification, metastatic disease or infection, etc.).
[0157] "Cross-Referencing" of images in the context of the current
disclosure contemplates the comparison of one image to another
image in the same or a different group of images. Desirably, the
"cross-referenced" images will have a common anatomical or other
reference feature which facilitates the comparison of features
between the relevant images. Cross-referencing can be in 2D and 3D;
2D data can be cross-referenced against 3D data. Historical data
can be cross-referenced against current data. Such
cross-referencing and comparison can be between images, as well as
between individual anatomical features of each image against other
anatomical features in the same image and/or against similar
features from other images.
[0158] In addition, information from one set of images may be
utilized in comparison with other images to identify inaccuracies
or discrepancies across images and/or among image groups, which may
decrease confidence in the accuracy of some images and/or identify
additional areas of anatomical concern (i.e., implant fracture
and/or dislocation). In a similar manner, information from one set
of images may be utilized in comparison with other images to
identify consistencies and/or congruencies across images, which may
increase confidence in the accuracy of the various images (and/or
image components, features or areas of interest) and/or identify
anatomical and/or implant areas that remain unchanged or "not of
concern" over time. The various accuracies and inaccuracies may be
rated and identified in various ways, including through the use of
a "heat map" or "color chart" that provides a 2-D, 3-D or 4-D
(i.e., time-lapse or other such presentation) rendering of the
anatomy and implant, with areas of high confidence in "cool" colors
(i.e., blue and green) and areas of low confidence in "hot colors"
(i.e., yellow and red) corresponding to various comparison factors,
such as (1) significant changes in anatomy, (2) significant changes
in implant characteristics and/or alignment, (3) significant
perceived inaccuracies across image series, and (4) significant
areas or scarification, bone remodeling, etc. Various embodiments
may display and/or identify areas of estimated anatomical margins
and/or implant location as a "confidence contour map" or other
display.
[0159] Another advantage for conducting comparisons across image
series could include identifying and/or correcting imaging
inaccuracies caused or induced by "artifacts" or other factors
during the imaging process. For example, metallic "artifacts"
(including metallic joint replacement implants) are known to affect
the quality of some non-invasive image methods (i.e., x-ray, CT,
MRI, etc.) to various degrees, especially where the "location of
interest" is adjacent to the artifacts. Not only can such artifacts
mask the anatomy near such objects, but such artifacts may cause
significant image distortion, which significantly reduces the
utility of such imaging in planning and assessing anatomical
structures during revision procedures. If desired, artifact
reduction algorithms or other processing steps (including
enhancement of low-metal artifact information), as well as imaging
techniques desirably "less sensitive" to artifact distortion, may
be utilized in an attempt to improve image quality and/or
reliability. In addition, the use and comparison of multiple images
of the same anatomical region and/or implant, utilizing differing
imaging methods (to desirably highlight different types and/or
portions of anatomy and/or implant) are contemplated in various
embodiments. The use of other images in the image series, including
images taken prior to initial implantation of the "artifact," can
be used to cross-check the accuracy of such artifact-laden images,
and may also be used to correct such distortion where applicable.
In a similar manner, data regarding the structure of the "failed
implant" may be especially useful in such situations. The external
margins of the "failed implant" are often readily discernable on
non-invasive images, and knowledge of the internal and peripheral
features of the implant (i.e., implant design, shape and size,
including bone-facing surfaces of the implant) can be calculated
and/or cross-referenced from or against the external margins to
estimate the location of corresponding internal surfaces (which are
desirably adjacent to estimated margins of the anatomical support
structures). Moreover, knowledge of the internal surface location
can be used to cross-reference against other images, including
against other images of the same implant from differing angles, as
well as can be used to identify limits or locations where
anatomical structures can or cannot be. I.e., any image that
identifies an anatomical structure within a location where the
implant exists (i.e., anatomy and implant structure at the same
3-dimensional location) should be either incorrect or may indicate
a fractured, dislocated or otherwise displaced implant. Information
regarding the thicknesses of implant material at various locations
or along various planes may also be useful in evaluating the amount
of distortion experienced in a given image or portion of image.
Similar implant data can be utilized to determine the thickness of
a metal implant along various planes of imaging, and may be
utilized to estimate the amount of implant distortion experienced
as well as to identify "preferred" imaging angle to reduce or
minimize distortion (i.e., choose imaging planes to minimize
implant thickness, or to place known planar implant surfaces
perpendicular to x-ray imaging, etc).
[0160] In one exemplary embodiment, the use of images from a prior
scan of the patient, in combination with a current scan of the
patient (containing failed implant image(s)) and known data
regarding the shape and size of the failed implant (including
internal and external surface dimensions) can be processed and/or
utilized to provide significant useful data regarding the quality
and quantity of anatomical support structure available for use with
a revision implant procedure. By knowing the amount of potential
anatomical support structure remaining, this embodiment allows the
revision implant to be selected and/or designed to require minimum
resection and/or preparation of remaining anatomical support
structures after implant removal. In addition, if the implant has
fractured or otherwise failed in a manner whereby the anatomical
support structure has remained substantially intact, a replacement
(revision) implant can be chosen or designed that requires little
or no alteration to the underlying anatomical support structure
prior to implantation. If desired, the bone-facing structures of
the revision implant can replicate those of the "failed implant"
(to facilitate implantation with little or no cutting or
preparation of the underlying anatomical surfaces), while
alterations to the joint-facing or articulating structures (and/or
the thickness of the implant) can alter the biomechanics of the
revision implant and revised joint in a desirable manner.
[0161] Another alternate embodiment could utilize the original
scans of the patient's anatomy (either prior to or after initial
implantation of the primary implant) to create a revision implant
and/or surgical tools for use in preparing the anatomical support
surfaces for the revision implant. Such devices could include
patient-specific anatomical support surfaces for alignment and/or
placement of the revision implant. If desired, the original scan
data could be normalized, assessed, evaluated and/or corrected as
described herein to improve image accuracy and/or quality.
TABLE-US-00002 TABLE 2 Exemplary Anatomical and Implant Features
Anatomical Features Implant Features Resection surfaces of bone
Internal (bone facing) surfaces of the due to primary implant
"failed implant" Unresected bone surfaces Chamfer cut dimensions
and locations of Residual cartilage the "failed implant", e.g.
based on image Osteophytes data or manufacturer data, in 2D or 3D
Osteolysis External (joint facing) surfaces of the "failed Bone
Cement implant", e.g. based on image data or Bone density
manufacturer data, in 2D or 3D Bone structure Surface corners
Peripheral edge(s) Notches Stem shape of the "failed implant", e.g.
based on image data or manufacturer data, in 2D or 3D Insert shape,
e.g. polyethylene, of the "failed implant, e.g. based on image data
(e.g. actual) or manufacturer data (e.g. prior to failure), in 2D
or 3D
[0162] In a similar manner, the images may be corrected or
otherwise evaluated for accuracies relevant to the type and
size/thickness of the implant, other artifact, or general or
specific known or unknown inaccuracies in the imaging equipment
and/or modality. For example, areas of high metal concentration
(i.e., thicker sections of an implant) may be more prone to
artifact distortion than areas of lesser metal concentration.
Similarly, various metal types may be more or less prone to
artifact distortion, as will artifacts having low-metal content
such as some ceramics and polymers. In addition, the different
types of imaging equipment are likely to have different accuracies,
not only due to the differing imaging modalities (i.e., 2-D vs. 3D
vs. 4D imaging, MRI, CT-scan, CAT, fluoroscopy and x-ray,
ultrasound, PET, and/or other radiographic, nuclear,
photo-acoustic, thermographic, tomographic and/or ultrasonic
imaging techniques, etc.), but also calibration of the related
equipment, age of the scans (i.e., older scans may have been held
to a lower accuracy standard or may have degraded in storage), and
inherent differences in the equipment and/or the various
environments of use (i.e., heat, temperature, etc). All of some of
these various factors may be included with image data to increase,
decrease or otherwise assess the "confidence" of the data accuracy,
which may affect how such data is viewed and/or rated during
assessment, evaluation, comparison/cross-referencing and/or
correction of some of all of the image data. For example, where an
older image depicts an anatomical feature that does not correlate
to more recent image groups, the older image data may be considered
"less reliable" than newer image data, and may be appropriately
assessed (i.e., discarded or assigned a low reliability value) or
alternatively may be judged to be "more reliable" where the older
image was taken without artifact interference, or by a more
reliable imaging modality, etc. Each image or image group
(including individual features of interest within an image) may, if
desired, be assigned such "reliability ratings," or individual
features of images may have differing "reliability ratings", or
combinations thereof. The assessment system may also identify
common anatomical features across differing image groups, which may
affect "reliability ratings" in either a positive or negative
manner.
[0163] This disclosure contemplates a wide variety of "priority" or
"ranking" systems for use with the various assessment and
evaluation systems of the present invention. Virtually any
combination of priorities can be incorporated into the assessment
and evaluation process, typically on a user-defined basis, although
the use of pre-defined priorities and/or groups of priorities is
also encompassed by this disclosure. For example, higher priorities
may be given to data assessed as having a greater "likelihood of
accuracy" as defined by the user and/or system. Such greater
likelihood could be due to a wide variety of factors, including (1)
inherent accuracy of the imaging method, (2) multiple groups of
images identifying a common anatomical feature or features (and/or
"failed implant" feature or features) in the same or similar
location, and/or (3) images where artifacts are absent or have been
corrected for. Similarly, the evaluation process can include
varying priorities as defined by the user or others, including (1)
cost priorities for selecting and/or designing an implant in the
most cost-efficient (or least-cost efficient or any variations
thereof) manner (i.e., manufacturing costs, material costs,
processing/machining costs, use of pre-existing implants versus
custom built implants, etc.), (2) scheduling or availability
priorities for selecting and/or designing an implant in the
time-efficient (or least-time efficient or any variations thereof)
manner (i.e., to ensure an implant will be available for use within
a specified time frame, etc.), and/or (3) inventory management
issues (i.e., to utilize materials and/or implant sizes that are
already manufactured and/or are being manufactured in larger
quantities, etc).
[0164] Once the images have been compared, evaluated,
cross-referenced and/or normalized, one or more composite image
sets or output sets or generated images may be produced that
desirably reflect one or more of the following (1) the most
accurate and correct image or set of images of the failed implant,
(2) the most accurate and complete image or set of images of the
underlying anatomical support structure(s), and/or (3) one or more
images or "boundary diagrams" of the anatomical support structures
that are estimated to remain after removal of the failed implant.
This information may then be used to create revision implants and
surgical tools particularized for use in removing the failed
implant, revising the supporting anatomical structures, and
implanting the revision implant in a desired fashion. Such
information may also assist in evaluating and assessing the
patient's disease state and/or progression of disease and/or
degeneration over a period of time.
[0165] If desired, various embodiments may include a graphical user
interface (GUI) that allows an operator (surgeon, implant designer,
patient, etc.) to conduct pre-operative planning of the revision
procedure, including simulating post-operative alignment of the
revision implant incorporating augments and/or spacers, wherein the
spacer and/or augment can be selected by the user and the alignment
information and possible surface information can be modeled,
displayed and/or built into (or otherwise incorporated into) the
surgical tools and/or surgical implant, including jigs or guides
that the jigs include.
[0166] In various embodiments, an exterior surface model or "frame
diagram" of the failed implant and surrounding anatomical structure
of the joint can be created electronically (and/or physically, if
desired). In a manner similar to the creation of implants and/or
surgical tools and molds described previously in various
embodiments of this disclosure, portions of the frame diagram (or
physical model) may be utilized to create conforming surfaces for
engagement by the surgical tools and molds (i.e., utilizing only
surface features of the failed implant, using surface features of
the failed implant in combination with anatomical features of the
joint surfaces and/or using only anatomical features of the joint
surfaces to align the tools and/or molds). Similarly, portions of
the frame diagram (or physical model) may be utilized to design
and/or select the interior and/or exterior surfaces of the revision
implant.
[0167] It may also be desirous for an evaluation system to have the
capability of evaluating the type and/or size of failed implant in
various image sets, including the capability to identify
unidentified implants or implant components (and possibly verify
the identity of a known or suspected implant type) from a database
of known implant designs. In many cases, the exact design, shape
and/or size of the failed implant will be unknown, either because
surgical records are unavailable, are disorganized or are
incorrect, and the use of proper implant information may be
important to the evaluation and assessment of various patient
information. In various embodiments, the system is desirably
capable of evaluation the condition of various implants and/or
implant components, facilitating identification of failed or
fractured components that may require replacement, while the
remaining components may remain in situ, as desired. Once
identified, information and/or data regarding the various implant
components can be included in the various image/data groups for
assessment and/or evaluation and preparation of the revision
implant and/or tools. Of course, if information regarding the
"failed implant" is already known or is available, such implant
information (possibly available based on patient history, surgical
reports and/or manufacturer's records) may be included, utilized
and/or verified by the evaluation system.
[0168] Once the processing, assessment, evaluation and/or
cross-referencing/correcting of patient and "failed implant"
information has been accomplished to a desired degree, the
resulting image and/or data information may be utilized to plan the
revision surgery, which can include the creation of revision
implants, implant components and surgical tools for preparation of
anatomical surfaces and implantation of the revision implant.
Revision surgery is particularly well suited to the systems and
methods described herein, as the disclosed methods are capable of
determining and/or estimating the patient's anatomical structure
underlying the "failed implant" to a degree significantly greater
than that allowed by current practice. For example, in a typical
knee revision procedure, a physician is often unaware of the actual
structure and/or condition of the underling margins of the
anatomical support structure (i.e., bone and any remaining
articular surfaces that may have supported the "failed implant")
until the failed implant has been removed in surgery. Because of
this, revision implants typically plan and are designed for
significant bone removal (to accommodate a "worst case" scenario
where most supporting bone has degraded), and often also require an
intramedullary stem that serves as an alignment structure for
aligning the joint implant, as well as a support structure for
securing the implant to the surrounding bone. With the disclosed
system, however, a more accurate estimate of the underlying bony
support structure can be determined, and thus less bone and other
support structures need be removed in preparing for the revision
implant, as well as allowing for a revision implant or implant
components to be constructed appropriate to the existing support
structure. In addition, the identification of existing support
structures, in combination with the use of the failed implant as an
anatomical reference point, allows positioning of the revision
implant without necessarily resorting to intramedullary or other
highly-invasive reference points or methods. Moreover, the present
method enables a surgeon to determine, prior to surgery, whether
sufficient anatomical support structures remain to support the
revision implant without need for an intramedullary stem or other
such support structure.
[0169] If desired, an appropriate revision implant can be selected
from a library or a revision implant can be generated based on the
patient specific parameters obtained in the measurements and
evaluation. If desired, surgical tools such as custom jigs to
assist in the preparation of the anatomical surface can be
constructed using information regarding the implant as well as the
generated image data. Prior to installing the implant in the joint,
the implantation site is prepared and then the implant is
installed. One or more of these steps can be repeated as necessary
or desired as shown by the optional repeat steps. In various
embodiments, the surgical tools of this disclosure can be
particularized for use in a patient, for the implantation of a
standard joint replacement implant (i.e., a standard or
non-patient-specific implant), as desired.
[0170] In various embodiments, the resulting image and/or data
information may be utilized to create a "custom" revision implant
well suited to match and/or conform to the most accurate anatomical
data. In various additional embodiments, the resulting data and/or
image information may be utilized in combination with "confidence"
or "statistical accuracy" data derived by the evaluation software
to a degree defined by the user. For example, an implant and/or
surgical tool may be specifically designed to have a "95%"
confidence that the implant/surgical tool will fit the derived
anatomical structure, and would thus be designed such that the
internal structural surfaces would accommodate, encompass and/or
conform to an anatomical model that follows the estimated contours
of the underlying anatomical structures to at least a 95%
confidence level. If desired, multiple implants of various
confidence levels may be produced for use in a single surgery, with
an implant of relatively "lower" confidence value being designed
for a patient-specific application for use in a manner similar to a
"rescue" revision implant where actual bone conditions
significantly different from those estimated, or if the primary
revision implant will not accommodate or properly fit the actual
anatomical surfaces.
A. Imaging Techniques
I. Thickness and Curvature
[0171] As will be appreciated by those of skill in the art, imaging
techniques suitable for measuring thickness and/or curvature (e.g.,
of cartilage and/or bone) or size of areas of diseased cartilage or
cartilage loss include the use of x-rays, magnetic resonance
imaging (MRI), computed tomography scanning (CT, also known as
computerized axial tomography or CAT), optical coherence
tomography, ultrasound imaging techniques, optical imaging
techniques, and others disclosed herein and/or are well known in
the art. (See, also, International Patent Publication WO 02/22014
to Alexander, et al., published Mar. 21, 2002; U.S. Pat. No.
6,373,250 to Tsoref et al., issued Apr. 16, 2002; and Vandeberg et
al. (2002) Radiology 222:430-436). Contrast or other enhancing
agents can be employed using any route of administration, e.g.
intravenous, intra-articular, etc.
[0172] Based on the imaging performed, and any assessment,
evaluation, correction and/or cross-referencing performed as
previously described, the software may evaluate the fit of
different implants and/or surgical guide templates with regard to
dimensions, overall size and shape. The dimensions, overall size
and shape may be optimized with regard to cortical bone shape and
dimensions, cortical bone thickness, endosteal bone shape, size of
marrow cavity, articular surface shape and dimensions, subchondral
bone shape and dimensions, or subchondral bone thickness. Thus, for
example, an implant may either be custom made or selected from a
number of pre-manufactured implants that is optimized with regard
to any of the following or combinations thereof: AP dimensions and
shape, mediolateral dimensions and shape, superoinferior dimensions
and shape, shape of the articulating surface, shape and dimensions
of the interface in contact with cortical bone, shape and
dimensions of intramedullary portions or components. These
parameters may also be optimized for implant function, e.g. for
different degrees of joint flexion or extension or abduction or
adduction or internal or external rotation.
[0173] In certain embodiments, CT or MRI is used to assess tissue,
bone, cartilage and any defects therein, for example cartilage
lesions or areas of diseased cartilage, to obtain information on
subchondral bone or cartilage degeneration and to provide
morphologic or biochemical or biomechanical information about the
area of damage. Specifically, changes such as fissuring, partial or
full thickness cartilage loss, and signal changes within residual
cartilage can be detected using one or more of these methods. For
discussions of the basic NMR principles and techniques, see MRI
Basic Principles and Applications, Second Edition, Mark A. Brown
and Richard C. Semelka, Wiley-Liss, Inc. (1999). For a discussion
of MRI including conventional T1 and T2-weighted spin-echo imaging,
gradient recalled echo (GRE) imaging, magnetization transfer
contrast (MTC) imaging, fast spin-echo (FSE) imaging, contrast
enhanced imaging, rapid acquisition relaxation enhancement (RARE)
imaging, gradient echo acquisition in the steady state (GRASS), and
driven equilibrium Fourier transform (DEFT) imaging, to obtain
information on cartilage, see Alexander, et al., WO 02/22014. Other
techniques include steady state free precision, flexible
equilibrium MRI and DESS. Thus, in preferred embodiments, the
measurements produced are based on three-dimensional images of the
joint obtained as described in Alexander, et al., WO 02/22014 or
sets of two-dimensional images ultimately yielding 3D information.
Two-dimensional, and three-dimensional images, or maps, of the
cartilage alone or in combination with a movement pattern of the
joint, e.g. flexion-extension, translation and/or rotation, can be
obtained. Three-dimensional images can include information on
movement patterns, contact points, contact zone of two or more
opposing articular surfaces, and movement of the contact point or
zone during joint motion. Two- and three-dimensional images can
include information on biochemical composition of the articular
cartilage. In addition, imaging techniques can be compared over
time, for example to provide up-to-date information on the shape
and type of repair material needed.
[0174] Traditional CT and MRI scans utilize two dimensional
cross-sectional images acquired in different imaging planes to
visualize complex three-dimensional articular anatomy. With
computed tomography, these slices are typically acquired in the
axial plane. The in-plane resolution is typically on the order of
0.25.times.0.25 millimeters. The slice thickness may vary from one
to five millimeters. Thus, the resolution obtained with these
imaging studies is not isotropic. Moreover, the CT slices and,
similarly with MRI, may be separated by one or more millimeters.
This means that the resolution of the images is excellent within
the imaging plane. However, two to ten-fold loss in image
resolution can be encountered in a plane perpendicular to the
slices acquired by the CT or MRI scanner. This limitation in
resolution perpendicular to the imaging plane can result in
inaccuracies in deriving the three-dimensional shape of, without
limitation, an implant and/or a 3-D guidance template, described in
more detail below.
[0175] In accordance with one embodiment, spiral CT imaging is
utilized to acquire the images rather than standard CT technology.
With recent CT technology, slip ring technology is incorporated in
the scanner. A slip ring is a circular contact with sliding brushes
that allows the gantry to rotate continuously, untethered by
electrical wires. The use of slip ring technology eliminates the
initial limitations at the end of each slice acquisition. Thus, the
rotating gantry is free to rotate continuously throughout the
examination of a joint. A slip ring CT scanner design allows
greater rotational velocities, thereby shortening scan times. With
a spiral CT scan data is acquired while the table is moving. As a
result, the x-ray source moves in a spiral or helical rather than a
circular pattern around the patient. The speed of the table motion
relative to the rotation of the CT gantry is a very important
consideration for image quality in helical or spiral CT scanning.
This parameter is call pitch. In a preferred embodiment, spiral CT
scans will be acquired through the joint wherein these spiral CT
scans afford a resolution that is isotropic, for example 1
millimeter by 1 millimeter by 1 millimeter in x, y and z direction,
or, more preferred, 0.75.times.0.75.times.0.75 millimeters in x, y
and z direction, or, more preferred, 0.5.times.0.5.times.0.5
millimeters in x, y and z direction, or, more preferred
0.25.times.0.25.times.0.25 millimeters in x, y and z direction.
Near isotropic data sets are also acceptable particularly if the
maximum resolution in any one of the three special orientations
does not exceed 1.5 millimeters, or, more preferred 1.0
millimeters, or, more preferred 0.75 millimeters, or, more
preferred 0.5 millimeters. Thus, this disclosure recognizes that
the accuracy in placing a 3-D guidance template on an articular
surface, or shaping an implant, can be greatly improved with
isotropic or near isotropic data sets as compared to traditional
2-D slice based data sets derived from either CT or MRI or other
imaging technologies. For example, a knee joint scan data acquired
with near isotropic resolution of 0.4.times.0.4.times.0.7
millimeters (e.g. a resolution ratio of less than 2:1 between the
different dimensions and resolution in all three dimensions
preferably better than 1 mm) will yield greater positional accuracy
in placing a 3-D guidance template on the articular surface than
scan data acquired using traditional CT scans, for example, with a
scan resolution of 0.4.times.0.4.times.1.2 millimeters.
[0176] With MRI, standard acquisition call sequences also result in
two dimensional slices for displaying complex three dimensional
articular anatomy. The two dimensional slices can be acquired using
2-D or 3-D Fourier transformation. After the 2-D or 3-D transform,
2-D slices are available for image viewing and image processing. Of
note, typically the image resolution in the imaging plane will be
two or more fold greater than the image resolution perpendicular to
the primary imaging plane. Similar to CT, this limitation in
spatial resolution in the plane perpendicular to the imaging plane
can result in inaccuracies in deriving and subsequently placing 3-D
guidance molds. In a preferred embodiment, MRI data is acquired or
processed so that the data used for generating the 3-D guidance
mold or implant has isotropic or near isotropic resolution. For
example, isotropic or near isotropic resolution may be achieved by
fusing two non-parallel imaging planes acquired using standard 2-D
or 3-D Fourier transform images, registering them relative to each
other and performing an image fusion (see U.S. patent application
Ser. No. 10/728,731, entitled "FUSION OF MULTIPLE IMAGING PLANES
FOR ISOTROPIC IMAGING IN MRI AND QUANTITATIVE IMAGE ANALYSIS USING
ISOTROPIC OR NEAR-ISOTROPIC IMAGING," hereby incorporated by
reference in its entirety). Alternatively, using latest generation
scan technology, for example, with 3-D FSE, 3-D DESS, 3-D MENSA,
3-D PAVA, 3-D LAVA, 3-D MERGE, 3-D MEDIC imaging sequences,
multi-channel coils, high field magnets, advanced gradient
technology, isotropic or near isotropic acquisition using 3-D
Fourier transform can be obtained. Using such advanced imaging
technology, image resolution of 0.5 by 0.5 by 0.8 millimeters or
greater may be obtained, achieving near isotropic and even
isotropic resolution, with preferably resolution in all three
dimensions of less than 1 mm.
[0177] As will be appreciated by those of skill in the art, imaging
techniques can be combined, if desired. For example, C-arm imaging
or x-ray fluoroscopy can be used for motion imaging, while MRI can
yield high resolution cartilage information. C-arm imaging can be
combined with intra-articular contrast to visualize the
cartilage.
[0178] Any of the imaging devices described herein can also be used
intra-operatively (see, also below), for example using a hand-held
ultrasound and/or optical probe to image the articular surface
intra-operatively. FIG. 2 illustrates a color reproduction of a
three-dimensional thickness map of the articular surface on the
distal femur. The dark holes within the cartilage indicate areas of
full cartilage loss.
ii. Anatomical and Mechanical Axes, Virtual Ligament Balancing
[0179] Imaging can be used to determine the anatomical and
biomechanical axes of an extremity associated with a joint, which
can then be used in creating an implant or surgical guide template
or mold. Suitable tests include, for example, an x-ray, or an x-ray
combined with an MRI. Typically, anatomical landmarks are
identified on the imaging test results (e.g., the x-ray film) and
those landmarks are then utilized to directly or indirectly
determine the desired axes. Thus, for example, if surgery is
contemplated in a hip joint, knee joint, or ankle joint, an x-ray
can be obtained. This x-ray can be a weight-bearing film of the
extremity, for example, a full-length leg film taken while the
patient is standing. This film can be used to determine the femoral
and tibial anatomical axes and to estimate the biomechanical axes.
As will be appreciated by those of skill in the art, these
processes for identifying, e.g., anatomical and mechanical axis of
the joint can be applied to other joints without departing from the
scope of the invention. Similarly, the use of processed and/or
evaluated images or image groups, as described in various locations
herein, can be utilized as an exemplary "imaging" source in for
further use in designing, manufacturing and/or choosing appropriate
implants, as described in the various embodiments disclosed and
discussed herein.
[0180] Anatomical and biomechanical axes can also be determined
using other imaging modalities, including but not limited to,
computed tomography and MRI. For example, a CT scan can be obtained
through the hip joint, the knee joint, and the ankle joint.
Optionally, the scan can be reformatted in the sagittal, coronal,
or other planes. The CT images can then be utilized to identify
anatomical landmarks and to determine the anatomical and
biomechanical axes of the hip joint, knee joint, and/or ankle
joint.
[0181] Similarly, an MRI scan can be obtained for this purpose. For
example, an MRI scan of the thigh and pelvic region can be obtained
using a body coil or a torso phased array coil. A high resolution
scan of the knee joint can be obtained using a dedicated extremity
coil. A scan of the calf/tibia region and the ankle joint can be
obtained again using a body coil or a torso phased array coil.
Anatomical landmarks can be identified in each joint on these scans
and the anatomical and biomechanical axes can be estimated using
this information.
[0182] In various embodiments, the imaging scan can be extended for
5 cm, more preferably 10 cm, or more preferably 15 cm above and/or
below the joint thereby deriving anatomic information that can be
used to derive the anatomic and mechanical axis. For example, an
MRI or CT scan can be obtained through a knee joint. The scan can
extend 15 cm above and below the joint. The mid-femoral line and
mid-tibial line as well as other anatomic landmarks such as the
femoral transepicondylar line or Whiteside line or posterior
condylar line can be determined and can be used to estimate the
anatomic and biomechanical axes. Thus, in the example of a knee
joint, no additional scanning through the hip joint and ankle
joints will be needed.
[0183] With, for example, MRI, even larger coverage may be
obtained, for example with a series of axial, sagittal or coronal
slices obtained with a large field of view, e.g. 20 cm or more
preferably 25 cm, or more preferably 30 cm, or more preferably 35
cm. These large field of view scans can be utilized to estimate the
anatomic and biomechanical axes as described above. They lack,
however, information on the surface detail of the joint due to
limitations in spatial resolution. A second or additional scan can
be performed with high resolution, e.g. with spatial resolution and
x and y axis of less than 1.0 mm, or, more preferably, less than
0.8 mm, or, more preferably, less than 0.6 mm. The additional high
resolution scan may be utilized to derive the articular surface
detail needed for a good and accurate fit between the guidance
template or implant, and the articular surface or adjacent
structures.
[0184] A mechanical axis and, in some instances, an anatomical axis
may advantageously be defined by imaging the entire extremity in
question, or through imaging combinations and/or assessment, as
disclosed herein. Such imaging may include cross-sectional, spiral
or volumetric imaging via a CT or MRI scan or optical imaging
through the entire extremity, or acquisition of select images or
slices or volumes through an area of interest such as a hip joint,
a knee joint or ankle joint.
[0185] In an illustrative embodiment, scans through the entire or
portions of an entire extremity covering multiple joints may be
replaced with an extended scan through a single joint such as a
knee joint. For example, it may not be sufficient to estimate a
mechanical axis or an anatomical access with a standard knee scan
such as a CT scan or MRI scan that includes, for example, only ten
centimeter of the area or volume of interest above, or ten
centimeters of area or volume of interest below the tibiofemoral
joints space. With an extended scan, a larger area adjacent to the
target joint can be included in the scan, e.g. fifteen centimeters
above and below the medial tibia femoral joint space, twenty
centimeters above and below the medial tibia femoral joint space,
fifteen centimeters above and twenty centimeters below the medial
tibiofemoral joint space, twenty centimeters above and twenty-five
centimeters below the medial tibiofemoral joint space. While the
extended scan is less involved on the operative side than the scan
involving the neighboring joints, it can, optionally be used to
provide an estimate of the anatomical axis, mechanical axis, and/or
an implant axes or related planes. Thus, better ease of use is
provided at the expense of, possibly, more radiation and possibly,
less accuracy.
[0186] In another embodiment, cross-sectional or volumetric images
such as CT scans or MRI scans may be acquired through more than one
joint, typically one or more joints neighboring the one
contemplated for surgery. For example, CT or MRI slices, CT
spirals, CT or MRI volumes, MRI two plane acquisitions with
optional image fusion, or other tomographic acquisitions are
acquired through the hip joint, knee joint and ankle joint in a
patient scheduled for total knee replacement surgery. The 3D
surgical guidance templates may be optimized by using anatomic
and/or biomechanical information obtained in the adjacent
neighboring joints, for example, resulting in an improved anatomic
or functional result. By using cross-sectional or volumetric
imaging information, more accurate identification of anatomic
landmarks for identifying relevant anatomical and/or mechanical
axis, relevant planes including surgical planes and implant planes,
as well as implant axes can be achieved when compared to x-rays or
CT scout scans, in particular when the cross-sectional or
volumetric data are acquired through neighboring joints. The
accuracy of the position, orientation, shape or combinations
thereof, of a 3D guide template can thus be improved with resulting
improvement in accuracy of the surgical correction of underlying
deformities such as varus, valgus, abduction, adduction, or
rotation deformities.
[0187] An imaging test obtained during weight-bearing conditions
has some inherent advantages, in that it demonstrates normal as
well as pathological loading and load distribution. A
cross-sectional imaging study such as a CT scan or MRI scan has
some advantages because it allows one to visualize and demonstrate
the anatomical landmarks in three, rather than two, dimensions,
thereby adding accuracy. Moreover, measurements can be performed in
other planes, such as the sagittal or oblique planes, that may not
be easily accessible in certain anatomical regions using
conventional radiography. In principle, any imaging test can be
utilized for this purpose.
[0188] The mechanical axis can be defined as the axis going from
the center of the femoral head, between the condylar surfaces and
through the ankle joint
[0189] The software may automatically, semi-automatically or
manually assisted find or identify the relevant anatomic points to
calculate the anatomic and biomechanical axes, in accordance with
various embodiments of the invention. For example, the software or
the user can find the center of the femoral head. Optionally, this
can be done in 3D rather than only in 2D. Thus, for example, in the
femoral head, the software can find the center of the femoral head
relative to its x, y, and z-dimensions. Alternatively, the relevant
anatomic points can be selected manually and the axes can be
calculated.
[0190] In another embodiment the software can compute methods of
adjusting varus or valgus or ante- or retroversion deformity or
rotational deformity based on such anatomic and mechanical axis
measurements. For example, the surface of a surgical guide template
can be adapted so that surgical cuts performed for a total knee
implant can be placed to correct an underlying varus or valgus
deformity or, for example, ante- or retroversion. Alternatively,
the openings/cut planes of a surgical guide template used for
drilling, cutting and the like can be adjusted to achieve a varus
or valgus correction to a near anatomic or physiologic range. These
adjustments can be optimized for the implants of different
manufacturers, e.g. Johnson & Johnson, Stryker, Smith &
Nephew, Biomet and Zimmer.
[0191] In various embodiments, gait, loading and other physical
activities of a joint as well as static joint positions may be
simulated using a computer workstation. The template and its
apertures and the resultant surgical templates and/or procedures,
e.g. cuts, drilling, rasping, may be optimized using this
information to achieve an optimal functional result. For example,
the template and its apertures and the resultant implant position
may be optimized for different degrees of flexion and extension,
internal or external rotation, abduction or adduction, and ante or
retroversion. Thus, the templates may be used to achieve motion
that is optimized in one, two or more directions. Not only
anatomic, but also functional optimization is possible in this
manner.
[0192] The origin and insertion of ligaments, e.g. the anterior and
posterior cruciate ligaments and the medial and lateral collateral
ligaments in the case of a knee, can be visualized on the scan.
With MRI, the ligaments are directly visible. If the ligament is
torn, the location of the residual fibers at the origin or
attachment can be visualized. Different joint positions can then be
simulated and changes in ligament length can be determined for
different angles of flexion and extension, internal or external
rotation, abduction or adduction, and ante or retroversion. These
simulations can be performed without but also with the implant in
place. Thus, ligament length--and through this presumed
tension--can be estimated virtually with any given implant and
implant size. Different implants or component(s) can be tested
preoperatively on the computer workstation and the implant or
component(s) yielding the optimal ligament performance, e.g.
minimal change in ligament length, for different joint positions
can be determined pre-operatively. Thus, this disclosure provides
among others for pre-operative ligament balancing, including but
not limited to by directly visualizing the ligaments or fiber
remnants.
[0193] For example, in one embodiment a loading apparatus may be
applied to the patient to simulate weight-bearing while acquiring
the CT scan. A non-limiting example of such a loading apparatus has
been described by Dynamed with the Dynawell device. Any loading
apparatus that can apply axial or other physiologic or near
physiologic loading forces on the hip, knee or ankle joints or two
or three of them may be used. Other more sophisticated scanning
procedures can be used to derive this information without departing
from the scope of the invention.
[0194] In a preferred embodiment, when imaging a joint of the lower
extremity, a standing, weight-bearing x-ray can be obtained to
determine the mechanical axis. In the case of a knee or hip joint,
for example, a standing, weight-bearing x-ray of the hip joint or
the knee joint can be obtained. Alternatively, standing,
weight-bearing x-rays can be obtained spanning the entire leg from
the hip to the foot. The x-ray can be obtained in the
anteroposterior or posterior-anterior projection but also in a
lateral projection or principally any other projection that is
desired. The user can measure the mechanical axis, for example, by
finding the centroid of the femoral head and the centroid of the
ankle joint and by connecting these. This measurement can be
performed manually, for example, on a x-ray film or electronically,
for example, on a digitized or digital image, including with
software assistance. The axis measured on the standing,
weight-bearing x-ray can be cross referenced with another imaging
modality such a CT or MRI scan. For example, a mechanical axis can
be determined on a standing x-ray of the leg. The result and data
can be cross referenced, for example, by identifying corresponding
bony anatomical landmarks to a CT scan or MRI scan. The result and
information can then be utilized to determine the optimal shape of
a 3-D guidance template. Specifically, the orientation, position,
or shape of the template can be influenced based on the measurement
of the mechanical axis. Moreover, the position or shape of any
blocks attached to said templates or linkages or the position or
shape instruments attached to the mold, block or linkages can be
influenced by this measurement. Combining the standing,
weight-bearing imaging modality with CT scanning or MRI scanning
has the principle advantage that the joint is evaluated during
physiological loading. CT or MRI alone, typically do not afford
assessment in loaded, weight-bearing condition. If desired, other
embodiments can use unloaded image data to simulate loaded,
weight-bearing conditions of such joint.
[0195] As described above, the mechanical axis can be evaluated in
different planes or in three dimensions. For example, the actual
mechanical axis can be assessed in the AP plane and a desired
mechanical axis can be determined in this plane. In addition, the
actual mechanical axis can be determined in the lateral plane, for
example, in the lateral projection radiograph, and the desired
mechanical axis can be determined in the lateral plane. By
measuring the relevant biomechanical and anatomical axis in two or
more planes, the shape of a 3-D guidance template and/or implant
can be further refined and optimized with result in improvements in
clinical and patient function.
[0196] The biomechanical or anatomical axis may also be measured
using other approaches including a non-weight bearing position. For
example, anatomical landmarks can be identified on a CT scout scan
and cross referenced to a joint such as a knee joint or a hip joint
for which surgery is contemplated. Thus, for example, the user can
measure and determine the centroid of the ankle joint and the
centroid of the hip joint for knee surgery using the CT scout
scan.
[0197] In a preferred embodiment, the anatomical landmarks are
determined using CT slices or MRI slices rather than a scout scan.
A CT scout scan or MRI scout scan can have inherent limitations in
spatial resolution. A CT scout scan is typically a single, 2-D
radiographic image of the extremity lacking 3-D anatomical
information and lacking high spatial resolution. An MRI scout scan
is typically composed of multiple 2-D MRI slices, possibly acquired
in one, two, or three planes. However, the resolution of the MRI
scout scan is typically also limited. By acquiring selective slices
and even isotropic or near isotropic data sets through neighboring
joints, anatomical landmarks can be identified in a more reliable
manner thereby improving the accuracy of anatomical and mechanical
axis determination. This improvement in accuracy translates into an
improvement in accuracy in the resultant 3-D guidance mold, for
example, a knee or hip joint, including improved accuracy of its
shape, orientation, or position.
[0198] Computed Tomography imaging has been shown to be highly
accurate for the determination of the relative anatomical and
biomechanical axes of the leg (Testi Debora, Zannoni Cinzia,
Cappello Angelo and Viceconti Marco. "Border tracing algorithm
implementation for the femoral geometry reconstruction." Comp.
Meth. and Programs in Biomed., Feb. 14, 2000; Farrar M J, Newman R
J, Mawhinney R R, King R. "Computed tomography scan scout film for
measurement of femoral axis in knee arthroplasty." J. Arthroplasty.
1999 December; 14(8): 1030-1; Kim J S, Park T S, Park S B, Kim J S,
Kim I Y, Kim S I. "Measurement of femoral neck anteversion in 3D.
Part 1: 3D imaging method." Med. and Biol. Eng. and Computing.
38(6): 603-609, November 2000; Akagi M, Yamashita E, Nakagawa T,
Asano T, Nakamura T. "Relationship between frontal knee alignment
and reference axis in the distal femur." Clin. Ortho. and Related
Res. No. 388, 147-156, 2001; Mahaisavariya B, Sitthiseripratip K,
Tongdee T, Bohez E, Sloten J V, Oris P. "Morphological study of the
proximal femur: a new method of geometrical assessment using 3
dimensional reverse engineering." Med. Eng. and Phys. 24 (2002)
617-622; Lam Li On, Shakespeare D. "Varus/Valgus alignment of the
femoral component in total knee arthroplasty." The Knee, 10 (2003)
237-241).
[0199] The angles of the anatomical structures of the proximal and
distal femur also show a certain variability level (i.e. standard
deviation) comparable with the varus or valgus angle or the angle
between the anatomical femoral axis and the mechanical axis
(Mahaisavariya B, Sitthiseripratip K, Tongdee T, Bohez E, Sloten J
V, Oris P. "Morphological study of the proximal femur: a new method
of geometrical assessment using 3 dimensional reverse engineering."
Med. Eng. and Phys. 24 (2002) 617-622). Thus, a preferred approach
for assessing the axes is based on CT scans of the hip, knee and
ankle joint or femur rather than only of the knee region.
[0200] CT has been shown to be efficient in terms of the contrast
of the bone tissue with respect to surrounding anatomical tissue so
the bone structures corresponding to the femur and tibia can be
extracted very accurately with semi automated computerized systems
(Mahaisavariya B, Sitthiseripratip K, Tongdee T, Bohez E, Sloten J
V, Oris P. "Morphological study of the proximal femur: a new method
of geometrical assessment using 3 dimensional reverse engineering."
Med. Eng. and Phys. 24 (2002) 617-622; Testi Debora, Zannoni
Cinzia, Cappello Angelo and Viceconti Marco. "Border tracing
algorithm implementation for the femoral geometry reconstruction."
Comp. Meth. and Programs in Biomed., Feb. 14, 2000).
[0201] While 2-D CT has been shown to be accurate in the estimation
of the mechanical axis (Mahaisavariya B, Sitthiseripratip K,
Tongdee T, Bohez E, Sloten J V, Oris P. "Morphological study of the
proximal femur: a new method of geometrical assessment using 3
dimensional reverse engineering." Med. Eng. and Phys. 24 (2002)
617-622; Testi Debora, supra.; Lam Li On, Supra, 3-D CT has been
shown to be more accurate for the estimation of the femoral
anteversion angle (Kim J S, Park T S, Park S B, Kim J S, Kim I Y,
Kim S I. Measurement of femoral neck anteversion in 3D. Part 1: 3D
imaging method. Medical and Biological engineering and computing.
38(6): 603-609, November 2000; Kim J S, Park T S, Park S B, Kim J
S, Kim I Y, Kim S I. Measurement of femoral neck anteversion in 3D.
Part 1: 3D modeling method. Medical and Biological engineering and
computing. 38(6): 610-616, November 2000). Farrar used simple CT
2-D scout views to estimate the femoral axis (Farrar M J, Newman R
J, Mawhinney R R, King R. Computed tomography scan scout film for
measurement of femoral axis in knee arthroplasty. J. Arthroplasty.
1999 December; 14(8): 1030-1).
[0202] In one embodiment, 2-D sagittal and coronal reconstructions
of CT slice images are used to manually estimate the mechanical
axis. One skilled in the art can easily recognize many different
ways to automate this process. For example, a CT scan covering at
least the hip, knee and ankle region is acquired. This results in
image slices (axial) which can be interpolated to generate the
sagittal and coronal views.
[0203] In addition to the various comparison, evaluation steps
disclosed herein, preprocessing (filtering) of the slice images can
be used to improve the contrast of the bone regions so that they
can be extracted accurately using simple thresholding or a more
involved image segmentation tool like LiveWire or active contour
models.
[0204] Identification of landmarks of interest like the centroid of
the tibial shaft, the ankle joint, the intercondylar notch and the
centroid of the femoral head can be performed. The mechanical axis
can be defined as the line connecting the proximal and the distal
centroids, i.e. the femoral head centroid, the tibial or ankle
joint centroid. The position of the intercondylar notch can be used
for evaluation of possible deviations, errors or deformations
including varus and valgus deformity.
[0205] In various embodiments, multiple imaging tests can be
combined. For example, the anatomical and biomechanical axes can be
estimated using a weight-bearing x-ray of the extremity or portions
of the extremity. The anatomical information derived in this
fashion can then be combined with a CT or MRI scan of one or more
joints, such as a hip, knee, or ankle joint. Landmarks seen on
radiography can then, for example, be cross-referenced on the CT or
MRI scan. Axis measurements performed on radiography can be
subsequently applied to the CT or MRI scans or other imaging
modalities. Similarly, the information obtained from a CT scan can
be compared with that obtained with an MRI or ultrasound scan. In
one embodiment, image fusion of different imaging modalities can be
performed. For example, if surgery is contemplated in a knee joint,
a full-length weight-bearing x-ray of the lower extremity can be
obtained. This can be supplemented by a spiral CT scan, optionally
with intra-articular contrast of the knee joint providing high
resolution three-dimensional anatomical characterization of the
knee anatomy even including the menisci and cartilage. This
information, along with the axis information provided by the
radiograph can be utilized to select or derive therapies, such as
implants or surgical instruments.
[0206] In certain embodiments, it may be desirable to characterize
the shape and dimension of intra-articular structures, including
subchondral bone or the cartilage. This may be done, for example,
by using a CT scan, preferably a spiral CT scan of one or more
joints. The spiral CT scan can optionally be performed using
intra-articular contrast. Alternatively, an MRI scan can be
performed. If CT is utilized, a full spiral scan, or a few selected
slices, can be obtained through neighboring joints. Typically, a
full spiral scan providing full three-dimensional characterization
would be obtained in the joint for which therapy is contemplated.
If implants, or templates, for surgical instruments are selected or
shaped, using this scan, the subchondral bone shape can be
accurately determined from the resultant image data. A standard
cartilage thickness and, similarly, a standard cartilage loss can
be assumed in certain regions of the articular surface. For
example, a standard thickness of 2 mm of the articular cartilage
can be applied to the subchondral bone in the anterior third of the
medial and lateral femoral condyles. Similarly, a standard
thickness of 2 mm of the articular cartilage can be applied to the
subchondral bone in the posterior third of the medial and lateral
femoral condyles. A standard thickness of 0 mm of the articular
cartilage can be applied in the central weight-bearing zone of the
medial condyle, and a different value can be applied to the lateral
condyle. The transition between these zones can be gradual, for
example, from 2 mm to 0 mm. These standard values of estimated
cartilage thickness and cartilage loss in different regions of the
joint can optionally be derived from a reference database. The
reference database can include categories such as age, body mass
index ("BMI"), severity of disease, pain, severity of varus
deformity, severity of valgus deformity, Kellgren-Lawrence score,
along with other parameters that are determined to be relative and
useful. Use of a standard thickness for the articular cartilage can
facilitate the imaging protocols required for pre-operative
planning.
[0207] Alternatively, however, the articular cartilage can be fully
characterized by performing a spiral CT scan of the joint in the
presence of intra-articular contrast or by performing an MRI scan
using cartilage sensitive pulse sequences.
[0208] The techniques described herein can be used to obtain an
image of a joint that is stationary, either weight bearing or not,
or in motion or combinations thereof. Imaging studies that are
obtained during joint motion can be useful for assessing the load
bearing surface. This can be advantageous for designing or
selecting implants, e.g. for selecting reinforcements in high load
areas, for surgical tools and for implant placement, e.g. for
optimizing implant alignment relative to high load areas.
iii. Joint Space
[0209] In accordance with other embodiments, a method and system
for determining joint space width is provided. Without limitation,
a CT scan, MRI scan, optical scan, and/or ultrasound imaging is
performed. The medial and lateral joint space width in a knee
joint, the joint space in a hip joint, ankle joint or other joint
is evaluated. This evaluation may be performed in two dimensions,
using a single scan plane orientation, such as sagittal or coronal
plane, or it may be performed in three dimensions. The evaluation
of joint space width may include measuring the distance from the
subchondral bone plate of one articular surface to the subchondral
bone plate of the opposing articular surface. Alternatively, the
cartilage thickness may be measured directly on one or more
articular surfaces. Joint space width or cartilage thickness may be
measured for different regions of the joint and joint space width
and cartilage loss can be evaluated in anterior, posterior, medial,
lateral, superior and/or inferior positions. The measurements may
be performed for different positions of the joint such as a neutral
position, 45 degrees of flexion, 90 degrees of flexion, 5 degrees
of abduction, 5 degrees of internal rotation and so forth. For
example, in a knee joint, the joint space width may be evaluated in
extension and at 25 degrees of knee flexion and 90 degrees of knee
flexion. The medial and lateral joint space width may be compared
and differences in medial and lateral joint space width can be
utilized to optimize the desired postoperative correction in
anatomical or mechanical axis alignment based on this information.
The shape, orientation, or position of a 3D guided template may be
adjusted using this information, for example, in knee or hip
implant placement or other surgeries.
[0210] For example, the measurement may show reduced joint space
width or cartilage thickness in the medial compartment when
compared to a normal anatomic reference standard, e.g. from age or
sex or gender matched controls, and/or lateral compartment. This
can coincide with valgus alignment of the knee joint, measured, for
example, on the scout scan of a CT-scan or the localizer scan of an
MRI scan including multiple localizer scans through the hip, knee
and ankle joints.
[0211] If the mechanical axis estimated on the comparison of the
medial and lateral joint space width coincides with the mechanical
axis of the extremity measured on the scout scan, no further
adjustment may be necessary. If the mechanical axis estimated on
the comparison of the medial and lateral joint space width does not
coincide with the mechanical axis of the extremity measured on the
CT or MRI scout scan, additional correction of the valgus deformity
(or in other embodiments, varus or other deformities) can be
achieved.
[0212] This additional correction may be determined, for example,
by adding the difference in axis correction desired based on
mechanical axis measured by comparison of the medial lateral joint
space width and axis correction desired based on measurement of the
mechanical axis of the extremity measured on the scout or localizer
scan to axis correction desired based on measurement of the
mechanical axis of the extremity measured on the scout or localizer
scan alone. By combining the information from both, measurement of
joint space width of the median and lateral compartment and
measurement of the mechanical axis using the scout scan or
localizer scan or, for example, a weight bearing x-ray, an improved
assessment of axis alignment during load bearing conditions can be
obtained with resultant improvements in the shape, orientation or
position of the 3D guidance template and related attachments or
linkages.
[0213] Optionally, the extremity can be loaded while in the
scanner, for example, using a compression harness. Examples for
compression harnesses have been published, for example, by
Dynawell.
iv. Estimation of Cartilage Loss
[0214] In another embodiment, an imaging modality such as spiral
CT, spiral CT arthography, MRI, optical imaging, optical coherence
tomography, ultrasound and others may be used to estimate cartilage
loss in one, two or three dimensions. The information can be used
to determine a desired correction of a measured biomechanical or
anatomical axis. The correction can be in the anterior-posterior,
medio-lateral, and/or super-inferior direction, or any other
direction applicable or desirable, or combinations thereof. The
information can be combined with other data e.g., from a standing,
weight bearing x-ray or CT scout scan, or an MRI localizer scan or
a CT scan or MRI scan that includes axial/spiral or other images
through the hip, knee and ankle joints. The information can be used
to refine the axis correction desired based on, for example,
standing x-rays, non-weight bearing x-rays, CT scout scans, MRI
localizer scans and the like.
[0215] In another embodiment, any axis correction can be performed
in a single plane (e.g., the medial-lateral plane), in two planes
(e.g., the medial lateral and anterior-posterior planes), or
multiple planes, including oblique planes that are biomechanically
or anatomically relevant or desirable.
v. High Resolution Imaging
[0216] Additional improvements in accuracy of the 3D guide template
and/or implants surfaces may be obtained with use of imaging
technology that yields high spatial resolution, not only within the
imaging plane, but along all three planes, specifically the X, Y
and Z axis. With CT scanning, this can be achieved with the advent
of spiral CT Scanning techniques. With MRI, dual or more plane
scanning or volumetric acquisition can be performed. If dual or
more plane MRI scanning is performed, these multiple scan planes
can be fused, for example by cross-registration and resampling
along the X, Y and Z axis. The resultant effective resolution in X,
Y and Z direction is greatly improved as compared to standard CT
scanning or standard MRI scanning. Improvements in resolution have
the advantage that the resultant 3D guide templates can be
substantially more accurate, for example with regard to their
position, shape or orientation.
vi. Phantom Scans
[0217] Imaging modalities are subject to scan to scan variations,
for example, including spatial distortion. In one embodiment,
phantom scans may be performed in order to optimize the scan
quality, specifically spatial resolution and spatial distortion. A
phantom scan can be performed prior to a patient scan,
simultaneously with a patient scan or after a patient scan. Using
the phantom scan data, it is possible to make adjustments and
optimizations of the scanner and, moreover, to perform image post
processing to perform corrections, for example, correction of
geometric distortions. Thus, if a phantom scan detects certain
geometric distortion in the X, Y or Z axis and the amount of
distortion is measured on the phantom scan, a correction factor can
be included in the data prior to generating a 3D guide template.
The resulting 3D guide template is thus more accurate with
resulting improvement in intra-operative cross-reference to the
anatomic surface and resultant improved accuracy in any surgical
intervention such as drilling or cutting.
[0218] In another embodiment, a smoothing operation, e.g. using low
frequency filtering, can be performed in order to remove any image
related artifacts, such as stepping artifacts between adjacent CT
or MRI slices. In some applications, the smoothing operation can be
helpful in improving the fit between the joint and the
template.
B. Intraoperative Measurements
[0219] Alternatively, or in addition to, non-invasive imaging
techniques described above, measurements of the size of an area of
diseased cartilage or an area of cartilage loss, measurements of
cartilage thickness and/or curvature of cartilage or bone can be
obtained intraoperatively during arthroscopy or open arthrotomy.
Intraoperative measurements can, but need not, involve actual
contact with one or more areas of the articular surfaces.
[0220] Devices suitable for obtaining intraoperative measurements
of cartilage or bone or other articular structures, and to generate
a topographical map of the surface include but are not limited to,
Placido disks, optical measurements tools and device, optical
imaging tools and devices, and laser interferometers, and/or
deformable materials or devices. (See, for example, U.S. Pat. No.
6,382,028 to Wooh et al., issued May 7, 2002; U.S. Pat. No.
6,057,927 to Levesque et al., issued May 2, 2000; U.S. Pat. No.
5,523,843 to Yamane et al. issued Jun. 4, 1996; U.S. Pat. No.
5,847,804 to Sarver et al. issued Dec. 8, 1998; and U.S. Pat. No.
5,684,562 to Fujieda, issued Nov. 4, 1997).
[0221] Other devices to measure cartilage and subchondral bone
intraoperatively include, for example, ultrasound probes. An
ultrasound probe, preferably handheld, can be applied to the
cartilage and the curvature of the cartilage and/or the subchondral
bone can be measured. Moreover, the size of a cartilage defect can
be assessed and the thickness of the articular cartilage can be
determined. Such ultrasound measurements can be obtained in A-mode,
B-mode, or C-mode. If A-mode measurements are obtained, an operator
can typically repeat the measurements with several different probe
orientations, e.g. mediolateral and anteroposterior, in order to
derive a three-dimensional assessment of size, curvature and
thickness.
[0222] One skilled in the art will easily recognize that different
probe designs are possible using the optical, laser interferometry,
mechanical and ultrasound probes. The probes are preferably
handheld. In certain embodiments, the probes or at least a portion
of the probe, typically the portion that is in contact with the
tissue, can be sterile. Sterility can be achieved with use of
sterile covers, for example similar to those disclosed in WO
99/08598A1 to Lang, published Feb. 25, 1999.
[0223] Analysis on the curvature of the articular cartilage or
subchondral bone using imaging tests and/or intraoperative
measurements can be used to determine the size of an area of
diseased cartilage or cartilage loss. For example, the curvature
can change abruptly in areas of cartilage loss. Such abrupt or
sudden changes in curvature can be used to detect the boundaries of
diseased cartilage or cartilage defects.
[0224] As described above, measurements can be made while the joint
is stationary, either weight bearing or not, or in motion.
II. Repair Materials
[0225] A wide variety of materials find use in the practice of the
present invention, including, but not limited to, plastics, metals,
crystal free metals, ceramics, biological materials (e.g., collagen
or other extracellular matrix materials), hydroxyapatite, cells
(e.g., stem cells, chondrocyte cells or the like), or combinations
thereof. Based on the information (e.g., measurements) obtained
regarding the defect and the articular surface and/or the
subchondral bone, a repair material can be formed or selected.
Further, using one or more of these techniques described herein, a
cartilage replacement or regenerating material having a curvature
that will fit into a particular cartilage defect, will follow the
contour and shape of the articular surface, and will match the
thickness of the surrounding cartilage. The repair material can
include any combination of materials, and typically include at
least one non-pliable material, for example materials that are not
easily bent or changed.
A. Metal and Polymeric Repair Materials
[0226] Currently, joint repair systems often employ metal and/or
polymeric materials including, for example, prostheses which are
anchored into the underlying bone (e.g., a femur in the case of a
knee prosthesis). See, e.g., U.S. Pat. No. 6,203,576 to Afriat, et
al. issued Mar. 20, 2001 and U.S. Pat. No. 6,322,588 to Ogle, et
al. issued Nov. 27, 2001, and references cited therein. A
wide-variety of metals are useful in the practice of the present
invention, and can be selected based on any criteria. For example,
material selection can be based on resiliency to impart a desired
degree of rigidity. Non-limiting examples of suitable metals
include silver, gold, platinum, palladium, iridium, copper, tin,
lead, antimony, bismuth, zinc, titanium, cobalt, stainless steel,
nickel, iron alloys, cobalt alloys, such as Elgiloy.RTM., a
cobalt-chromium-nickel alloy, and MP35N, a
nickel-cobalt-chromium-molybdenum alloy, and Nitinol.TM., a
nickel-titanium alloy, aluminum, manganese, iron, tantalum, crystal
free metals, such as Liquidmetal.RTM. alloys (available from
LiquidMetal Technologies, www.liquidmetal.com), other metals that
can slowly form polyvalent metal ions, for example to inhibit
calcification of implanted substrates in contact with a patient's
bodily fluids or tissues, and combinations thereof.
[0227] Suitable synthetic polymers include, without limitation,
polyamides (e.g., nylon), polyesters, polystyrenes, polyacrylates,
vinyl polymers (e.g., polyethylene, polytetrafluoroethylene,
polypropylene and polyvinyl chloride), polycarbonates,
polyurethanes, poly dimethyl siloxanes, cellulose acetates,
polymethyl methacrylates, polyether ether ketones, ethylene vinyl
acetates, polysulfones, nitrocelluloses, similar copolymers and
mixtures thereof. Bioresorbable synthetic polymers can also be used
such as dextran, hydroxyethyl starch, derivatives of gelatin,
polyvinylpyrrolidone, polyvinyl alcohol, poly[N-(2-hydroxypropyl)
methacrylamide], poly(hydroxy acids), poly(epsilon-caprolactone),
polylactic acid, polyglycolic acid, poly(dimethyl glycolic acid),
poly(hydroxy butyrate), and similar copolymers can also be
used.
[0228] Other materials would also be appropriate, for example, the
polyketone known as polyetheretherketone (PEEK.TM.). This includes
the material PEEK 450G, which is an unfilled PEEK approved for
medical implantation available from Victrex of Lancashire, Great
Britain. (Victrex is located at www.matweb.com or see Boedeker
www.boedeker.com). Other sources of this material include Gharda
located in Panoli, India (www.ghardapolymers.com).
[0229] It should be noted that the material selected can also be
filled. For example, other grades of PEEK are also available and
contemplated, such as 30% glass-filled or 30% carbon filled,
provided such materials are cleared for use in implantable devices
by the FDA, or other regulatory body. Glass filled PEEK reduces the
expansion rate and increases the flexural modulus of PEEK relative
to that portion which is unfilled. The resulting product is known
to be ideal for improved strength, stiffness, or stability. Carbon
filled PEEK is known to enhance the compressive strength and
stiffness of PEEK and lower its expansion rate. Carbon filled PEEK
offers wear resistance and load carrying capability.
[0230] As will be appreciated, other suitable similarly
biocompatible thermoplastic or thermoplastic polycondensate
materials that resist fatigue, have good memory, are flexible,
and/or deflectable have very low moisture absorption, and good wear
and/or abrasion resistance, can be used without departing from the
scope of the invention. The implant can also be comprised of
polyetherketoneketone (PEKK).
[0231] Other materials that can be used include polyetherketone
(PEK), polyetherketoneetherketoneketone (PEKEKK), and
polyetheretherketoneketone (PEEKK), and generally a
polyaryletheretherketone. Further other polyketones can be used as
well as other thermoplastics.
[0232] Reference to appropriate polymers that can be used for the
implant can be made to the following documents, all of which are
incorporated herein by reference. These documents include: PCT
Publication WO 02/02158 A1, dated Jan. 10, 2002 and entitled
Bio-Compatible Polymeric Materials; PCT Publication WO 02/00275 A1,
dated Jan. 3, 2002 and entitled Bio-Compatible Polymeric Materials;
and PCT Publication WO 02/00270 A1, dated Jan. 3, 2002 and entitled
Bio-Compatible Polymeric Materials.
[0233] The polymers can be prepared by any of a variety of
approaches including conventional polymer processing methods.
Preferred approaches include, for example, injection molding, which
is suitable for the production of polymer components with
significant structural features, and rapid prototyping approaches,
such as reaction injection molding and stereolithography. The
substrate can be textured or made porous by either physical
abrasion or chemical alteration to facilitate incorporation of the
metal coating. Other processes are also appropriate, such as
extrusion, injection, compression molding and/or machining
techniques. Typically, the polymer is chosen for its physical and
mechanical properties and is suitable for carrying and spreading
the physical load between the joint surfaces.
[0234] More than one metal and/or polymer can be used in
combination with each other. For example, one or more
metal-containing substrates can be coated with polymers in one or
more regions or, alternatively, one or more polymer-containing
substrate can be coated in one or more regions with one or more
metals.
[0235] The system or prosthesis can be porous or porous coated. The
porous surface components can be made of various materials
including metals, ceramics, and polymers. These surface components
can, in turn, be secured by various means to a multitude of
structural cores formed of various metals. Suitable porous coatings
include, but are not limited to, metal, ceramic, polymeric (e.g.,
biologically neutral elastomers such as silicone rubber,
polyethylene terephthalate and/or combinations thereof) or
combinations thereof. See, e.g., U.S. Pat. No. 3,605,123 to Hahn,
issued Sep. 20, 1971. U.S. Pat. No. 3,808,606 to Tronzo issued May
7, 1974 and U.S. Pat. No. 3,843,975 to Tronzo issued Oct. 29, 1974;
U.S. Pat. No. 3,314,420 to Smith issued Apr. 18, 1967; U.S. Pat.
No. 3,987,499 to Scharbach issued Oct. 26, 1976; and German
Offenlegungsschrift 2,306,552. There can be more than one coating
layer and the layers can have the same or different porosities.
See, e.g., U.S. Pat. No. 3,938,198 to Kahn, et al., issued Feb. 17,
1976.
[0236] The coating can be applied by surrounding a core with
powdered polymer and heating until cured to form a coating with an
internal network of interconnected pores. The tortuosity of the
pores (e.g., a measure of length to diameter of the paths through
the pores) can be important in evaluating the probable success of
such a coating in use on a prosthetic device. See, also, U.S. Pat.
No. 4,213,816 to Morris issued Jul. 22, 1980. The porous coating
can be applied in the form of a powder and the article as a whole
subjected to an elevated temperature that bonds the powder to the
substrate. Selection of suitable polymers and/or powder coatings
can be determined in view of the teachings and references cited
herein, for example based on the melt index of each.
B. Biological Repair Material
[0237] Repair materials can also include one or more biological
material either alone or in combination with non-biological
materials. For example, any base material can be designed or shaped
and suitable cartilage replacement or regenerating material(s) such
as fetal cartilage cells can be applied to be the base. The cells
can be then be grown in conjunction with the base until the
thickness (and/or curvature) of the cartilage surrounding the
cartilage defect has been reached. Conditions for growing cells
(e.g., chondrocytes) on various substrates in culture, ex vivo and
in vivo are described, for example, in U.S. Pat. No. 5,478,739 to
Slivka et al. issued Dec. 26, 1995; U.S. Pat. No. 5,842,477 to
Naughton et al. issued Dec. 1, 1998; U.S. Pat. No. 6,283,980 to
Vibe-Hansen et al., issued Sep. 4, 2001, and U.S. Pat. No.
6,365,405 to Salzmann et al. issued Apr. 2, 2002. Non-limiting
examples of suitable substrates include plastic, tissue scaffold, a
bone replacement material (e.g., a hydroxyapatite, a bioresorbable
material), or any other material suitable for growing a cartilage
replacement or regenerating material on it.
[0238] Biological polymers can be naturally occurring or produced
in vitro by fermentation and the like. Suitable biological polymers
include, without limitation, collagen, elastin, silk, keratin,
gelatin, polyamino acids, cat gut sutures, polysaccharides (e.g.,
cellulose and starch) and mixtures thereof. Biological polymers can
be bioresorbable.
[0239] Biological materials used in the methods described herein
can be autografts (from the same subject); allografts (from another
individual of the same species) and/or xenografts (from another
species). See, also, International Patent Publications WO 02/22014
to Alexander et al. published Mar. 21, 2002 and WO 97/27885 to Lee
published Aug. 7, 1997. In certain embodiments autologous materials
are preferred, as they can carry a reduced risk of immunological
complications to the host, including re-absorption of the
materials, inflammation and/or scarring of the tissues surrounding
the implant site.
[0240] In one embodiment, a probe is used to harvest tissue from a
donor site and to prepare a recipient site. The donor site can be
located in a xenograft, an allograft or an autograft. The probe is
used to achieve a good anatomic match between the donor tissue
sample and the recipient site. The probe is specifically designed
to achieve a seamless or near seamless match between the donor
tissue sample and the recipient site. The probe can, for example,
be cylindrical. The distal end of the probe is typically sharp in
order to facilitate tissue penetration. Additionally, the distal
end of the probe is typically hollow in order to accept the tissue.
The probe can have an edge at a defined distance from its distal
end, e.g. at 1 cm distance from the distal end and the edge can be
used to achieve a defined depth of tissue penetration for
harvesting. The edge can be external or can be inside the hollow
portion of the probe. For example, an orthopedic surgeon can take
the probe and advance it with physical pressure into the cartilage,
the subchondral bone and the underlying marrow in the case of a
joint such as a knee joint. The surgeon can advance the probe until
the external or internal edge reaches the cartilage surface. At
that point, the edge will prevent further tissue penetration
thereby achieving a constant and reproducible tissue penetration.
The distal end of the probe can include one or more blades,
saw-like structures, or tissue cutting mechanism. For example, the
distal end of the probe can include an iris-like mechanism
consisting of several small blades. The blade or blades can be
moved using a manual, motorized or electrical mechanism thereby
cutting through the tissue and separating the tissue sample from
the underlying tissue. Typically, this will be repeated in the
donor and the recipient. In the case of an iris-shaped blade
mechanism, the individual blades can be moved so as to close the
iris thereby separating the tissue sample from the donor site.
[0241] In another embodiment, a laser device or a radiofrequency
device can be integrated inside the distal end of the probe. The
laser device or the radiofrequency device can be used to cut
through the tissue and to separate the tissue sample from the
underlying tissue.
[0242] In one embodiment, the same probe can be used in the donor
and in the recipient. In another embodiment, similarly shaped
probes of slightly different physical dimensions can be used. For
example, the probe used in the recipient can be slightly smaller
than that used in the donor thereby achieving a tight fit between
the tissue sample or tissue transplant and the recipient site. The
probe used in the recipient can also be slightly shorter than that
used in the donor thereby correcting for any tissue lost during the
separation or cutting of the tissue sample from the underlying
tissue in the donor material.
[0243] Any biological repair material can be sterilized to
inactivate biological contaminants such as bacteria, viruses,
yeasts, molds, mycoplasmas and parasites. Sterilization can be
performed using any suitable technique, for example radiation, such
as gamma radiation.
[0244] Any of the biological materials described herein can be
harvested with use of a robotic device. The robotic device can use
information from an electronic image for tissue harvesting.
[0245] In certain embodiments, the cartilage replacement material
has a particular biochemical composition. For instance, the
biochemical composition of the cartilage surrounding a defect can
be assessed by taking tissue samples and chemical analysis or by
imaging techniques. For example, WO 02/22014 to Alexander describes
the use of gadolinium for imaging of articular cartilage to monitor
glycosaminoglycan content within the cartilage. The cartilage
replacement or regenerating material can then be made or cultured
in a manner, to achieve a biochemical composition similar to that
of the cartilage surrounding the implantation site. The culture
conditions used to achieve the desired biochemical compositions can
include, for example, varying concentrations. Biochemical
composition of the cartilage replacement or regenerating material
can, for example, be influenced by controlling concentrations and
exposure times of certain nutrients and growth factors.
III. Devices Design
A. Cartilage Models
[0246] Using information on thickness and curvature of the
cartilage, a physical model of the surfaces of the articular
cartilage and of the underlying bone can be created. This physical
model can be representative of a limited area within the joint or
it can encompass the entire joint. For example, in the knee joint,
the physical model can encompass only the medial or lateral femoral
condyle, both femoral condyles and the notch region, the medial
tibial plateau, the lateral tibial plateau, the entire tibial
plateau, the medial patella, the lateral patella, the entire
patella or the entire joint. The location of a diseased area of
cartilage can be determined, for example using a 3D coordinate
system or a 3D Euclidian distance as described in WO 02/22014.
[0247] In this way, the size of the defect to be repaired can be
determined. As will be apparent, some, but not all, defects will
include less than the entire cartilage. Thus, in one embodiment,
the thickness of the normal or only mildly diseased cartilage
surrounding one or more cartilage defects is measured. This
thickness measurement can be obtained at a single point or,
preferably, at multiple points, for example 2 point, 4-6 points,
7-10 points, more than 10 points or over the length of the entire
remaining cartilage. Furthermore, once the size of the defect is
determined, an appropriate therapy (e.g., articular repair system)
can be selected such that as much as possible of the healthy,
surrounding tissue is preserved.
[0248] In other embodiments, the curvature of the articular surface
can be measured to design and/or shape the repair material.
Further, both the thickness of the remaining cartilage and the
curvature of the articular surface can be measured to design and/or
shape the repair material. Alternatively, the curvature of the
subchondral bone can be measured and the resultant measurement(s)
can be used to either select or shape a cartilage replacement
material. For example, the contour of the subchondral bone can be
used to re-create a virtual cartilage surface: the margins of an
area of diseased cartilage can be identified. The subchondral bone
shape in the diseased areas can be measured. A virtual contour can
then be created by copying the subchondral bone surface into the
cartilage surface, whereby the copy of the subchondral bone surface
connects the margins of the area of diseased cartilage.
[0249] Turning now to FIGS. 2A-H, various stages of knee
resurfacing steps are shown. FIG. 2A illustrates an example of
normal thickness cartilage 700 in the anterior, central and
posterior portion of a femoral condyle 702 with a cartilage defect
705 in the posterior portion of the femoral condyle. FIG. 2B shows
the detection of a sudden change in thickness indicating the
margins of a cartilage defect 710 that would be observed using the
imaging techniques or the mechanical, optical, laser or ultrasound
techniques described above. FIG. 2C shows the margins of a
weight-bearing surface 715 mapped onto the articular cartilage 700.
Cartilage defect 705 is located within the weight-bearing surface
715.
[0250] FIG. 2D shows an intended implantation site (stippled line)
720 and cartilage defect 705. In this depiction, the implantation
site 720 is slightly larger than the area of diseased cartilage
705. FIG. 2E depicts placement of a single component articular
surface repair system 725. The external surface of the articular
surface repair system 726 has a curvature that seamlessly extends
from the surrounding cartilage 700 resulting in good postoperative
alignment between the surrounding normal cartilage 700 and the
articular surface repair system 725.
[0251] FIG. 2F shows an exemplary multi-component articular surface
repair system 730. The distal surface 733 of the second component
732 has a curvature that extends from that of the adjacent
subchondral bone 735. The first component 736 has a thickness t and
surface curvature 738 that extends from the surrounding normal
cartilage 700. In this embodiment, the second component 732 could
be formed from a material with a Shore or Rockwell hardness that is
greater than the material forming the first component 736, if
desired. Thus it is contemplated that the second component 732
having at least portion of the component in communication with the
bone of the joint is harder than the first component 736 which
extends from the typically naturally softer cartilage material.
Other configurations, of course, are possible without departing
from the scope of the invention.
[0252] By providing a softer first component 736 and a firmer
second component 732, the overall implant can be configured so that
its relative hardness is analogous to that of the bone-cartilage or
bone-meniscus area that it abuts. Thus, the softer material first
component 736, being formed of a softer material, could perform the
cushioning function of the nearby meniscus or cartilage.
[0253] FIG. 2G shows another single component articular surface
repair system 740 with a peripheral margin 745 which is configured
so that it is substantially non-perpendicular to the surrounding or
adjacent normal cartilage 700. FIG. 2H shows a multi-component
articular surface repair system 750 with a first component 751 and
a second component 752 similar to that shown in FIG. 2G with a
peripheral margin 745 of the second component 745 substantially
non-perpendicular to the surrounding or adjacent normal cartilage
700.
[0254] Now turning to FIGS. 3A-E, these figures depict exemplary
knee imaging and resurfacing processes. FIG. 3A depicts a magnified
view of an area of diseased cartilage 805 demonstrating decreased
cartilage thickness when compared to the surrounding normal
cartilage 800. The margins 810 of the defect have been determined.
FIG. 3B depicts the measurement of cartilage thickness 815 adjacent
to the defect 805. FIG. 3C depicts the placement of a
multi-component mini-prosthesis 824 for articular resurfacing. The
thickness 820 of the first component 823 closely approximates that
of the adjacent normal cartilage 800. The thickness can vary in
different regions of the prosthesis. The curvature of the distal
portion 824 of the first component 823 closely approximates an
extension of the normal cartilage 800 surrounding the defect. The
curvature of the distal portion 826 of the second component 825 is
a projection of the surface 827 of the adjacent subchondral bone
830 and can have a curvature that is the same, or substantially
similar, to all or part of the surrounding subchondral bone.
[0255] FIG. 3D is a schematic depicting placement of a single
component mini-prosthesis 840 utilizing anchoring stems 845. As
will be appreciated by those of skill in the art, a variety of
configurations, including stems, posts, and nubs can be employed.
Additionally, the component is depicted such that its internal
surface 829 is located within the subchondral bone 830. In an
alternative construction, the interior surface 829 conforms to the
surface of the subchondral bone 831.
[0256] FIG. 3E depicts placement of a single component
mini-prosthesis 840 utilizing anchoring stems 845 and an opening at
the external surface 850 for injection of bone cement 855 or other
suitable material. The injection material 855 can freely
extravasate into the adjacent bone and marrow space from several
openings at the undersurface of the mini-prosthesis 860 thereby
anchoring the mini-prosthesis.
[0257] FIGS. 4A-C, depict an alternative knee resurfacing device.
FIG. 4A depicts a normal thickness cartilage in the anterior,
central and posterior portion of a femoral condyle 900 and a large
area of diseased cartilage 905 toward the posterior portion of the
femoral condyle. FIG. 4B depicts placement of a single component
articular surface repair system 910. Again, the implantation site
has been prepared with a single cut 921, as illustrated. However,
as will be appreciated by those of skill in the art, the repair
system can be perpendicular to the adjacent normal cartilage 900
without departing from the scope of the invention. The articular
surface repair system is not perpendicular to the adjacent normal
cartilage 900. FIG. 4C depicts a multi-component articular surface
repair system 920. Again, the implantation site has been prepared
with a single cut (cut line shown as 921). The second component 930
has a curvature similar to the extended surface 930 adjacent
subchondral bone 935. The first component 940 has a curvature that
extends from the adjacent cartilage 900.
C. Customized Containers
[0258] In another embodiment, a container or well can be formed to
the selected specifications, for example to match the material
needed for a particular subject or to create a stock of repair
materials in a variety of sizes. The size and shape of the
container can be designed using the thickness and curvature
information obtained from the joint and from the cartilage defect.
More specifically, the inside of the container can be shaped to
follow any selected measurements, for example as obtained from the
cartilage defect(s) of a particular subject. The container can be
filled with a cartilage replacement or regenerating material, for
example, collagen-containing materials, plastics, bioresorbable
materials and/or any suitable tissue scaffold. The cartilage
regenerating or replacement material can also consist of a
suspension of stem cells or fetal or immature or mature cartilage
cells that subsequently develop to more mature cartilage inside the
container. Further, development and/or differentiation can be
enhanced with use of certain tissue nutrients and growth
factors.
[0259] The material is allowed to harden and/or grow inside the
container until the material has the desired traits, for example,
thickness, elasticity, hardness, biochemical composition, etc.
Molds can be generated using any suitable technique, for example
computer devices and automation, e.g. computer assisted design
(CAD) and, for example, computer assisted modeling (CAM). Because
the resulting material generally follows the contour of the inside
of the container it will better fit the defect itself and
facilitate integration.
D. Designs Encompassing Multiple Component Repair Materials
[0260] The articular repair system or implants described herein can
include one or more components.
[0261] FIGS. 5A-B shows single and multiple component devices. FIG.
5A illustrates an example of a single component articular surface
repair system 1400 with varying curvature and radii that fits
within the subchondral bone 1420 such that the interior surface
1402 of the system 1400 does not form an extension of the surface
of the subchondral bone 1422. The articular surface repair system
is chosen to include convex 1402 and concave 1404 portions. Such
devices can be preferable in a lateral femoral condyle or small
joints such as the elbow joint. FIG. 5B depicts a multi-component
articular surface repair system with a second component 1410 with a
surface 1412 that forms an extension of the surface 1422 of the
subchondral bone 1420 and a first component 1405 with an interior
surface 1406 that forms an extension of the curvature and shape of
the surrounding normal cartilage 1415. The second component 1410
and the first component 1405 demonstrate varying curvatures and
radii with convex and concave portions that correspond to the
curvature of the subchondral bone 1420 and/or the normal cartilage
1415. As will be appreciated by those of skill in the art, these
two components can be formed such that the parts are integrally
formed with each other, or can be formed such that each part abuts
the other. Additionally, the relationship between the parts can be
by any suitable mechanism including adhesives and mechanical
means.
[0262] FIGS. 6A-B show articular repair systems 100 having an outer
contour 102 forming an extension of the surrounding normal
cartilage 200. The systems are implanted into the underlying bone
300 using one or more pegs 150, 175. The pegs, pins, or screws can
be porous-coated and can have flanges 125 as shown in FIG. 5B.
[0263] FIG. 7 shows an exemplary articular repair device 500
including a flat surface 510 to control depth and prevent toggle;
an exterior surface 515 having the contour of normal cartilage;
flanges 517 to prevent rotation and control toggle; a groove 520 to
facilitate tissue in-growth.
[0264] FIGS. 8A-D depict, in cross-section, another example of an
implant 640 with multiple anchoring pegs, stems, or screws 645.
FIG. 8B-D show various cross-sectional representations of various
possible embodiments of the pegs, or anchoring stems. FIG. 8B shows
a peg 645 having a notch 646 or groove around its circumference;
FIG. 8C shows a peg 645 with radially-extending arms 647 that help
anchor the device in the underlying bone; and FIG. 8D shows a peg
645 with multiple grooves or flanges 648.
[0265] FIGS. 9A-B depict an overhead view of an exemplary implant
650 with multiple anchoring pegs 655 which illustrates that the
pegs are not necessarily linearly aligned along the longitudinal
axis of the device.
[0266] FIG. 10A depicts an implant 660 with a peg 661 having
radially extending arms 665. FIGS. 10B-E are top views of the
implant pegs illustrating a variety of suitable alternative
shapes.
[0267] Examples of one-component systems include, but are not
limited to, a plastic, a polymer, a metal, a metal alloy, crystal
free metals, a biologic material or combinations thereof. In
certain embodiments, the surface of the repair system facing the
underlying bone can be smooth. In other embodiments, the surface of
the repair system facing the underlying bone can be porous or
porous-coated. In another aspect, the surface of the repair system
facing the underlying bone is designed with one or more grooves,
for example to facilitate the in-growth of the surrounding tissue.
The external surface of the device can have a step-like design,
which can be advantageous for altering biomechanical stresses.
Optionally, flanges can also be added at one or more positions on
the device (e.g., to prevent the repair system from rotating, to
control toggle and/or prevent settling into the marrow cavity). The
flanges can be part of a conical or a cylindrical design. A portion
or all of the repair system facing the underlying bone can also be
flat which can help to control depth of the implant and to prevent
toggle.
[0268] Non-limiting examples of multiple-component systems include
combinations of metal, plastic, metal alloys, crystal free metals,
and one or more biological materials. One or more components of the
articular surface repair system can be composed of a biologic
material (e.g. a tissue scaffold with cells such as cartilage cells
or stem cells alone or seeded within a substrate such as a
bioresorable material or a tissue scaffold, allograft, autograft or
combinations thereof) and/or a non-biological material (e.g.,
polyethylene or a chromium alloy such as chromium cobalt).
[0269] One or more regions of the articular surface repair system
(e.g., the outer margin of the first portion and/or the second
portion) can be bioresorbable, for example to allow the interface
between the articular surface repair system and the patient's
normal cartilage, over time, to be filled in with hyaline or
fibrocartilage. Similarly, one or more regions (e.g., the outer
margin of the first portion of the articular surface repair system
and/or the second portion) can be porous. The degree of porosity
can change throughout the porous region, linearly or non-linearly,
for where the degree of porosity will typically decrease towards
the center of the articular surface repair system. The pores can be
designed for in-growth of cartilage cells, cartilage matrix, and
connective tissue thereby achieving a smooth interface between the
articular surface repair system and the surrounding cartilage.
[0270] The repair system (e.g., the second component in multiple
component systems) can be attached to the patient's bone with use
of a cement-like material such as methylmethacrylate, injectable
hydroxy- or calcium-apatite materials and the like.
[0271] In certain embodiments, one or more portions of the
articular surface repair system can be pliable or liquid or
deformable at the time of implantation and can harden later.
Hardening can occur, for example, within 1 second to 2 hours (or
any time period therebetween), preferably with in 1 second to 30
minutes (or any time period therebetween), more preferably between
1 second and 10 minutes (or any time period therebetween).
[0272] One or more components of the articular surface repair
system can be adapted to receive injections. For example, the
external surface of the articular surface repair system can have
one or more openings therein. The openings can be sized to receive
screws, tubing, needles or other devices which can be inserted and
advanced to the desired depth, for example, through the articular
surface repair system into the marrow space. Injectables such as
methylmethacrylate and injectable hydroxy- or calcium-apatite
materials can then be introduced through the opening (or tubing
inserted therethrough) into the marrow space thereby bonding the
articular surface repair system with the marrow space. Similarly,
screws or pins, or other anchoring mechanisms, can be inserted into
the openings and advanced to the underlying subchondral bone and
the bone marrow or epiphysis to achieve fixation of the articular
surface repair system to the bone. Portions or all components of
the screw or pin can be bioresorbable, for example, the distal
portion of a screw that protrudes into the marrow space can be
bioresorbable. During the initial period after the surgery, the
screw can provide the primary fixation of the articular surface
repair system. Subsequently, ingrowth of bone into a porous coated
area along the undersurface of the articular cartilage repair
system can take over as the primary stabilizer of the articular
surface repair system against the bone.
[0273] The articular surface repair system can be anchored to the
patient's bone with use of a pin or screw or other attachment
mechanism. The attachment mechanism can be bioresorbable. The screw
or pin or attachment mechanism can be inserted and advanced towards
the articular surface repair system from a non-cartilage covered
portion of the bone or from a non-weight-bearing surface of the
joint. The anchoring component (e.g., pegs, pins) can have a porous
structure or porous coating to facilitate bone in-growth. For
example, a peg or pin can have a porous structure through its
cross-sectional diameter, such that it can be readily sawed through
when desired, e.g., removing an existing implant in a patient to
prepare for a revision surgery.
[0274] The interface between the articular surface repair system
and the surrounding normal cartilage can be at an angle, for
example oriented at an angle of 90 degrees relative to the
underlying subchondral bone. Suitable angles can be determined in
view of the teachings herein, and in certain cases, non-90 degree
angles can have advantages with regard to load distribution along
the interface between the articular surface repair system and the
surrounding normal cartilage.
[0275] The interface between the articular surface repair system
and the surrounding normal cartilage and/or bone can be covered
with a pharmaceutical or bioactive agent, for example a material
that stimulates the biological integration of the repair system
into the normal cartilage and/or bone. The surface area of the
interface can be irregular, for example, to increase exposure of
the interface to pharmaceutical or bioactive agents.
E. Pre-Existing Repair Systems
[0276] As described herein, repair systems, including surgical
instruments, templates, guides and/or molds, of various sizes,
curvatures and thicknesses can be derived, designed or otherwise
obtained. These repair systems, including surgical instruments,
guides, templates and/or molds, can be catalogued and stored to
create a library of systems from which an appropriate system for an
individual patient can then be selected. In other words, a defect,
or an articular surface, is assessed in a particular subject and a
pre-existing repair system, including surgical instruments,
templates, guides and/or molds, having a suitable shape and size is
selected from the library for further manipulation (e.g., shaping)
and implantation.
F. Mini-Prosthesis
[0277] As noted above, the methods and compositions described
herein can be used to replace only a portion of the articular
surface, for example, an area of diseased cartilage or lost
cartilage on the articular surface. In these systems, the articular
surface repair system can be designed to replace only the area of
diseased or lost cartilage or it can extend beyond the area of
diseased or lost cartilage, e.g., 3 or 5 mm into normal adjacent
cartilage. In certain embodiments, the prosthesis replaces less
than about 70% to 80% (or any value therebetween) of the articular
surface (e.g., any given articular surface such as a single femoral
condyle, etc.), preferably, less than about 50% to 70% (or any
value therebetween), more preferably, less than about 30% to 50%
(or any value therebetween), more preferably less than about 20% to
30% (or any value therebetween), even more preferably less than
about 20% of the articular surface.
[0278] The prosthesis can include multiple components, for example
a component that is implanted into the bone (e.g., a metallic
device) attached to a component that is shaped to cover the defect
of the cartilage overlaying the bone. Additional components, for
example intermediate plates, meniscal repair systems and the like
can also be included. It is contemplated that each component
replaces less than all of the corresponding articular surface.
However, each component need not replace the same portion of the
articular surface. In other words, the prosthesis can have a
bone-implanted component that replaces less than 30% of the bone
and a cartilage component that replaces 60% of the cartilage. The
prosthesis can include any combination, provided each component
replaces less than the entire articular surface.
[0279] The articular surface repair system can be formed or
selected so that it will achieve a near anatomic fit or match with
the surrounding or adjacent cartilage. Typically, the articular
surface repair system is formed and/or selected so that its outer
margin located at the external surface will be aligned with the
surrounding or adjacent cartilage.
[0280] Thus, the articular repair system can be designed to replace
the weight-bearing portion (or more or less than the weight bearing
portion) of an articular surface, for example in a femoral condyle.
The weight-bearing surface refers to the contact area between two
opposing articular surfaces during activities of normal daily
living (e.g., normal gait). At least one or more weight-bearing
portions can be replaced in this manner, e.g., on a femoral condyle
and on a tibia.
[0281] In other embodiments, an area of diseased cartilage or
cartilage loss can be identified in a weight-bearing area and only
a portion of the weight-bearing area, specifically the portion
containing the diseased cartilage or area of cartilage loss, can be
replaced with an articular surface repair system.
[0282] In another embodiment, the articular repair system can be
designed or selected to replace substantially all of the articular
surface, e.g. a condyle.
[0283] In another embodiment, for example, in patients with diffuse
cartilage loss, the articular repair system can be designed to
replace an area slightly larger than the weight-bearing
surface.
[0284] In certain aspects, the defect to be repaired is located
only on one articular surface, typically the most diseased surface.
For example, in a patient with severe cartilage loss in the medial
femoral condyle but less severe disease in the tibia, the articular
surface repair system can only be applied to the medial femoral
condyle. Preferably, in any methods described herein, the articular
surface repair system is designed to achieve an exact or a near
anatomic fit with the adjacent normal cartilage.
[0285] In other embodiments, more than one articular surface can be
repaired. The area(s) of repair will be typically limited to areas
of diseased cartilage or cartilage loss or areas slightly greater
than the area of diseased cartilage or cartilage loss within the
weight-bearing surface(s).
[0286] The implant and/or the implant site can be sculpted to
achieve a near anatomic alignment between the implant and the
implant site. In another embodiment, an electronic image is used to
measure the thickness, curvature, or shape of the articular
cartilage or the subchondral bone, and/or the size of a defect, and
an articular surface repair system is selected using this
information. The articular surface repair system can be inserted
arthroscopically. The articular surface repair system can have a
single radius. More typically, however, the articular surface
repair system has varying curvatures and radii within the same
plane, e.g. anteroposterior or mediolateral or superoinferior or
oblique planes, or within multiple planes. In this manner, the
articular surface repair system can be shaped to achieve a near
anatomic alignment between the implant and the implant site. This
design allows not only allows for different degrees of convexity or
concavity, but also for concave portions within a predominantly
convex shape or vice versa.
[0287] In another embodiment the articular surface repair system
has an anchoring stem, used to anchor the device, for example, as
described in U.S. Pat. No. 6,224,632 to Pappas et al issued May 1,
2001. The stem, or peg, can have different shapes including
conical, rectangular, fin among others. The mating bone cavity is
typically similarly shaped as the corresponding stem.
[0288] As shown in FIG. 6, discussed above, the articular surface
repair system 100 can be affixed to the subchondral bone 300, with
one or more stems, or pegs, 150 extending through the subchondral
plate into the marrow space. In certain instances, this design can
reduce the likelihood that the implant will settle deeper into the
joint over time by resting portions of the implant against the
subchondral bone. The stems, or pegs, can be of any shape suitable
to perform the function of anchoring the device to the bone. For
example, the pegs can be cylindrical or conical. Optionally, the
stems, or pegs, can further include notches or openings or other
porous structures to allow bone in-growth. In addition, the stems
can be porous coated for bone in-growth. The anchoring mechanisms
such as stems or pegs with porous structures can be readily sawed
through when desired, e.g., removing an existing implant in a
patient to prepare for a revision surgery.
[0289] The anchoring stems or pegs can be affixed to the bone using
bone cement. An additional anchoring device can also be affixed to
the stem or peg. The anchoring device can have an umbrella shape
(e.g., radially expanding elements) with the wider portion pointing
towards the subchondral bone and away from the peg. The anchoring
device can be advantageous for providing immediate fixation of the
implant. The undersurface of the articular repair system facing the
subchondral bone can be textured or rough thereby increasing the
contact surface between the articular repair system and the
subchondral bone. Alternatively, the undersurface of the articular
repair system can be porous coated thereby allowing in-growth. The
surgeon can support the in-growth of bone by treating the
subchondral bone with a rasp, typically to create a larger surface
area and/or until bleeding from the subchondral bone occurs.
[0290] In another embodiment, the articular surface repair system
can be attached to the underlying bone or bone marrow using bone
cement. Bone cement is typically made from an acrylic polymeric
material. Typically, the bone cement is comprised of two
components: a dry powder component and a liquid component, which
are subsequently mixed together. The dry component generally
includes an acrylic polymer, such as polymethylmethacrylate (PMMA).
The dry component can also contain a polymerization initiator such
as benzoylperoxide, which initiates the free-radical polymerization
process that occurs when the bone cement is formed. The liquid
component, on the other hand, generally contains a liquid monomer
such as methyl methacrylate (MMA). The liquid component can also
contain an accelerator such as an amine (e.g.,
N,N-dimethyl-p-toluidine). A stabilizer, such as hydroquinone, can
also be added to the liquid component to prevent premature
polymerization of the liquid monomer. When the liquid component is
mixed with the dry component, the dry component begins to dissolve
or swell in the liquid monomer. The amine accelerator reacts with
the initiator to form free radicals that begin to link monomer
units to form polymer chains. In the next two to four minutes, the
polymerization process proceeds changing the viscosity of the
mixture from a syrup-like consistency (low viscosity) into a
dough-like consistency (high viscosity). Ultimately, further
polymerization and curing occur, causing the cement to harden and
affix a prosthesis to a bone.
[0291] In certain aspects, bone cement or another liquid attachment
material such as injectable calciumhydroxyapatite can be injected
into the marrow cavity through one or more openings in the
prosthesis. These openings in the prosthesis can extend from the
articular surface to the undersurface of the prosthesis. After
injection, the openings can be closed with a polymer, silicon,
metal, metal alloy or bioresorbable plug.
[0292] In another embodiment, one or more components of the
articular surface repair (e.g., the surface of the system that is
pointing towards the underlying bone or bone marrow) can be porous
or porous coated. A variety of different porous metal coatings have
been proposed for enhancing fixation of a metallic prosthesis by
bone tissue in-growth. Thus, for example, U.S. Pat. No. 3,855,638
to Pilliar issued Dec. 24, 2974, discloses a surgical prosthetic
device, which can be used as a bone prosthesis, comprising a
composite structure consisting of a solid metallic material
substrate and a porous coating of the same solid metallic material
adhered to and extending over at least a portion of the surface of
the substrate. The porous coating consists of a plurality of small
discrete particles of metallic material bonded together at their
points of contact with each other to define a plurality of
connected interstitial pores in the coating. The size and spacing
of the particles, which can be distributed in a plurality of
monolayers, can be such that the average interstitial pore size is
not more than about 200 microns. Additionally, the pore size
distribution can be substantially uniform from the
substrate-coating interface to the surface of the coating. In
another embodiment, the articular surface repair system can contain
one or more polymeric materials that can be loaded with and release
therapeutic agents including drugs or other pharmacological
treatments that can be used for drug delivery. The polymeric
materials can, for example, be placed inside areas of porous
coating. The polymeric materials can be used to release therapeutic
drugs, e.g. bone or cartilage growth stimulating drugs. This
embodiment can be combined with other embodiments, wherein portions
of the articular surface repair system can be bioresorbable. For
example, the first layer of an articular surface repair system or
portions of its first layer can be bioresorbable. As the first
layer gets increasingly resorbed, local release of a cartilage
growth-stimulating drug can facilitate in-growth of cartilage cells
and matrix formation.
[0293] In any of the methods or compositions described herein, the
articular surface repair system can be pre-manufactured with a
range of sizes, curvatures and thicknesses. Alternatively, the
articular surface repair system can be custom-made for an
individual patient.
IV. Manufacturing
A. Shaping
[0294] In certain instances shaping of the repair material will be
required before or after formation (e.g., growth to desired
thickness), for example where the thickness of the required
cartilage material is not uniform (e.g., where different sections
of the cartilage replacement or regenerating material require
different thicknesses).
[0295] The replacement material can be shaped by any suitable
technique including, but not limited to, mechanical abrasion, laser
abrasion or ablation, radiofrequency treatment, cryoablation,
variations in exposure time and concentration of nutrients, enzymes
or growth factors and any other means suitable for influencing or
changing cartilage thickness. See, e.g., WO 00/15153 to Mansmann
published Mar. 23, 2000; If enzymatic digestion is used, certain
sections of the cartilage replacement or regenerating material can
be exposed to higher doses of the enzyme or can be exposed longer
as a means of achieving different thicknesses and curvatures of the
cartilage replacement or regenerating material in different
sections of said material.
[0296] The material can be shaped manually and/or automatically,
for example using a device into which a pre-selected thickness
and/or curvature has been input and then programming the device
using the input information to achieve the desired shape.
[0297] In addition to, or instead of, shaping the cartilage repair
material, the site of implantation (e.g., bone surface, any
cartilage material remaining, etc.) can also be shaped by any
suitable technique in order to enhance integration of the repair
material.
B. Sizing
[0298] The articular repair system can be formed or selected so
that it will achieve a near anatomic fit or match with the
surrounding or adjacent cartilage or subchondral bone or menisci
and other tissue. The shape of the repair system can be based on
the analysis of an electronic image (e.g. MRI, CT, digital
tomosynthesis, optical coherence tomography or the like). If the
articular repair system is intended to replace an area of diseased
cartilage or lost cartilage, the near anatomic fit can be achieved
using a method that provides a virtual reconstruction of the shape
of healthy cartilage in an electronic image or, alternatively, the
shape of the "failed implant" it replaces.
[0299] In one embodiment, a near normal cartilage surface at the
position of the cartilage defect can be reconstructed by
interpolating the healthy cartilage surface across the cartilage
defect or area of diseased cartilage. This can, for example, be
achieved by describing the healthy cartilage by means of a
parametric surface (e.g. a B-spline surface), for which the control
points are placed such that the parametric surface follows the
contour of the healthy cartilage and bridges the cartilage defect
or area of diseased cartilage. The continuity properties of the
parametric surface will provide a smooth integration of the part
that bridges the cartilage defect or area of diseased cartilage
with the contour of the surrounding healthy cartilage. The part of
the parametric surface over the area of the cartilage defect or
area of diseased cartilage can be used to determine the shape or
part of the shape of the articular repair system to match with the
surrounding cartilage.
[0300] In another embodiment, a near normal cartilage surface at
the position of the cartilage defect or area of diseased cartilage
can be reconstructed using morphological image processing. In a
first step, the cartilage can be extracted from the electronic
image using manual, semi-automated and/or automated segmentation
techniques (e.g., manual tracing, region growing, live wire,
model-based segmentation), resulting in a binary image. Defects in
the cartilage appear as indentations that can be filled with a
morphological closing operation performed in 2-D or 3-D with an
appropriately selected structuring element. The closing operation
is typically defined as a dilation followed by an erosion. A
dilation operator sets the current pixel in the output image to 1
if at least one pixel of the structuring element lies inside a
region in the source image. An erosion operator sets the current
pixel in the output image to 1 if the whole structuring element
lies inside a region in the source image. The filling of the
cartilage defect or area of diseased cartilage creates a new
surface over the area of the cartilage defect or area of diseased
cartilage that can be used to determine the shape or part of the
shape of the articular repair system to match with the surrounding
cartilage or subchondral bone.
[0301] As described above, the articular repair system, including
surgical tools and instruments, molds, in situ repair systems, etc.
can be formed or selected from a library or database of systems of
various sizes, curvatures and thicknesses so that it will achieve a
near anatomic fit or match with the surrounding or adjacent
cartilage and/or subchondral bone. These systems can be pre-made or
made to order for an individual patient. In order to control the
fit or match of the articular repair system with the surrounding or
adjacent cartilage or subchondral bone or menisci and other tissues
preoperatively, a software program can be used that projects the
articular repair system over the anatomic position where it will be
implanted. Suitable software is commercially available and/or
readily modified or designed by a skilled programmer.
[0302] In yet another embodiment, the articular repair system
including unicompartmental and total knee implants as well as hip
devices can be projected over the implantation site using one or
more 2-D or 3-D images. The cartilage and/or subchondral bone and
other anatomic structures can be optionally extracted from a 2-D or
3-D electronic image such as an MRI or a CT using manual,
semi-automated and/or automated segmentation techniques. A 2-D or
3-D representation of the cartilage and/or bone and other anatomic
structures as well as the articular repair system can be generated,
for example using a polygon or NURBS surface or other parametric
surface representation. Ligaments, menisci and other articular
structures can be displayed in 2-D and 3-D. For a description of
various parametric surface representations see, for example Foley,
J. D. et al., Computer Graphics: Principles and Practice in C;
Addison-Wesley, 2.sup.nd edition, 1995).
[0303] The 2-D or 3-D representations of the cartilage and/or
subchondral bone and other anatomic structures and the articular
repair system can be merged into a common coordinate system. The
articular repair system, including surgical tools and instruments,
molds, in situ repair systems, etc. can then be placed at the
desired implantation site. The representations of the cartilage,
subchondral bone, ligaments, menisci and other anatomic structures
and the articular repair system are rendered into a 2-D or 3-D
image, for example application programming interfaces (APIs)
OpenGL.RTM. (standard library of advanced 3-D graphics functions
developed by SGI, Inc.; available as part of the drivers for
PC-based video cards, for example from www.nvidia.com for NVIDIA
video cards or www.3dlabs.com for 3Dlabs products, or as part of
the system software for Unix workstations) or DirectX.RTM.
(multimedia API for Microsoft Windows.RTM. based PC systems;
available from www.microsoft.com). The 2-D or 3-D image can be
rendered or displayed showing the cartilage, subchondral bone,
ligaments, menisci or other anatomic objects, and the articular
repair system from varying angles, e.g. by rotating or moving them
interactively or non-interactively, in real-time or
non-real-time.
[0304] In another embodiment, the implantation site may be
visualized using one or more cross-sectional 2-D images, as
described in U.S. Ser. No. 10/305,652, entitled "Methods and
Compositions for Articular Repair," filed Nov. 27, 2002, which is
hereby incorporated by reference in its entirety. Typically, a
series of 2-D cross-sectional images will be used. The 2-D images
can be generated with imaging tests such as CT, MRI, digital
tomosynthesis, ultrasound, optical imaging, optical coherence
tomography, other imaging modalities using methods and tools known
to those of skill in the art. The articular repair system or
implant can then be superimposed onto one or more of these 2-D
images. The 2-D cross-sectional images may be reconstructed in
other planes, e.g. from sagittal to coronal, etc. Isotropic data
sets (e.g., data sets where the slice thickness is the same or
nearly the same as the in-plane resolution) or near isotropic data
sets can also be used. Multiple planes may be displayed
simultaneously, for example using a split screen display. The
operator may also scroll through the 2-D images in any desired
orientation in real time or near real time; the operator can rotate
the imaged tissue volume while doing this. The articular repair
system or implant may be displayed in cross-section utilizing
different display planes, e.g. sagittal, coronal or axial,
typically matching those of the 2-D images demonstrating the
cartilage, subchondral bone, ligaments, menisci or other tissue.
Alternatively, a three-dimensional display may be used for the
articular repair system. The 2-D electronic image and the 2-D or
3-D representation of the articular repair system or implant may be
merged into a common coordinate system. The cartilage repair system
or implant can then be placed at the desired implantation site. The
series of 2-D cross-sections of the anatomic structures, the
implantation site and the articular repair system or implant may be
displayed interactively (e.g. the operator can scroll through a
series of slices) or non-interactively (e.g. as an animation that
moves through the series of slices), in real-time or
non-real-time.
[0305] The software can be designed so that the articular repair
system, including surgical tools and instruments, molds, in situ
repair systems, etc. with the best fit relative to the cartilage
and/or subchondral bone is automatically selected, for example
using one or more of the techniques described above. Alternatively,
the operator can select an articular repair system, including
surgical tools and instruments, molds, in situ repair systems, etc.
and project it or drag it onto the implantation site displayed on
the cross-sectional 2-D or the 3-D images. The operator can then
move and rotate the articular repair system relative to the
implantation site and scroll through a cross-sectional 2-D or 3-D
display of the articular repair system and of the anatomic
structures. The operator can perform a visual and/or
computer-assisted inspection of the fit between the articular
repair system and the implantation site. This can be performed for
different positions of the joint, e.g. extension, 45, 90 degrees of
flexion, adduction, abduction, internal or external rotation. The
procedure can be repeated until a satisfactory fit has been
achieved. The procedure can be entirely manual by the operator; it
can, however, also be computer-assisted. For example, the software
can select a first trial implant that the operator can test (e.g.,
evaluate the fit). Software that highlights areas of poor alignment
between the implant and the surrounding cartilage or subchondral
bone or menisci or other tissues can also be designed and used.
Based on this information, the software or the operator can select
another implant and test its alignment.
[0306] In all of the above embodiments, the mechanical axis and
relevant anatomical axes or planes can be displayed simultaneous
with the joint and/or articular repair device in the 2-D or 3-D
display. Simultaneous display of at least one or more biomechanical
axes or anatomical axes or planes can help improve the assessment
of fit of the articular repair system. Biomechanical axis or
relevant anatomical axes or planes can also be displayed for
different positions of the joint.
C. Rapid Prototyping, Other Manufacturing Techniques
[0307] Rapid protyping is a technique for fabricating a
three-dimensional object from a computer model of the object. A
special printer is used to fabricate the prototype from a plurality
of two-dimensional layers. Computer software sections the
representations of the object into a plurality of distinct
two-dimensional layers and then a three-dimensional printer
fabricates a layer of material for each layer sectioned by the
software. Together the various fabricated layers form the desired
prototype. More information about rapid prototyping techniques is
available in US Patent Publication No 2002/0079601A1 to Russell et
al., published Jun. 27, 2002. An advantage to using rapid
prototyping is that it enables the use of free form fabrication
techniques that use toxic or potent compounds safely. These
compounds can be safely incorporated in an excipient envelope,
which reduces worker exposure
[0308] A powder piston and build bed are provided. Powder includes
any material (metal, plastic, etc.) that can be made into a powder
or bonded with a liquid. The power is rolled from a feeder source
with a spreader onto a surface of a bed. The thickness of the layer
is controlled by the computer. The print head then deposits a
binder fluid onto the powder layer at a location where it is
desired that the powder bind. Powder is again rolled into the build
bed and the process is repeated, with the binding fluid deposition
being controlled at each layer to correspond to the
three-dimensional location of the device formation. For a further
discussion of this process see, for example, US Patent Publication
No 2003/017365A1 to Monkhouse et al. published Sep. 18, 2003.
[0309] The rapid prototyping can use the two dimensional images
obtained, as described above in Section I, to determine each of the
two-dimensional shapes for each of the layers of the prototyping
machine. In this scenario, each two dimensional image slice would
correspond to a two dimensional prototype slide. Alternatively, the
three-dimensional shape of the defect can be determined, as
described above, and then broken down into two dimensional slices
for the rapid prototyping process. The advantage of using the
three-dimensional model is that the two-dimensional slices used for
the rapid prototyping machine can be along the same plane as the
two-dimensional images taken or along a different plane
altogether.
[0310] Rapid prototyping can be combined or used in conjunction
with casting techniques. For example, a shell or container with
inner dimensions corresponding to an articular repair system
including surgical instruments, molds, alignment guides or surgical
guides, can be made using rapid prototyping. Plastic or wax-like
materials are typically used for this purpose. The inside of the
container can subsequently be coated, for example with a ceramic,
for subsequent casting. Using this process, personalized casts can
be generated.
[0311] Rapid prototyping can be used for producing articular repair
systems including surgical tools, molds, alignment guides, cut
guides etc. Rapid prototyping can be performed at a manufacturing
facility. Alternatively, it may be performed in the operating room
after an intraoperative measurement has been performed.
[0312] Alternatively, milling techniques can be utilized for
producing articular repair systems including surgical tools, molds,
alignment guides, cut guides etc.
[0313] Alternatively, laser based techniques can be utilized for
producing articular repair systems including surgical tools, molds,
alignment guides, cut guides etc.
V. Implantation
[0314] Following one or more manipulations (e.g., shaping, growth,
development, etc), the cartilage replacement, implant or
regenerating material can then be implanted into the area of the
defect. Implantation can be performed with the cartilage
replacement or regenerating material still attached to the base
material or removed from the base material. Any suitable methods
and devices can be used for implantation, for example, devices as
described in U.S. Pat. No. 6,375,658 to Hangody et al. issued Apr.
23, 2002; U.S. Pat. No. 6,358,253 to Torrie et al. issued Mar. 19,
2002; U.S. Pat. No. 6,328,765 to Hardwick et al. issued Dec. 11,
2001; and International Publication WO 01/19254 to Cummings et al.
published Mar. 22, 2001.
[0315] In selected cartilage defects, the implantation site can be
prepared with a single cut across the articular surface, for
example. If desired, single and multi-component prostheses can be
utilized.
V. Revision Implants, Systems and Methods
[0316] The various system and methods described herein may also be
utilized to repair, revise or otherwise correct a
previously-treated implant that has failed in some manner.
Typically, joint replacement candidates, and the surgeries they
experience, follow a "cascade" process, where less-invasive
solutions and joint treatments are initially attempted and are
eventually followed by more-invasive surgical procedures as the
patient's joints and/or any implanted joint resurfacing and/or
replacement components continue to degenerate. In the case of the
knee joint, a patient can be diagnosed with a degenerative knee
condition, and is preferably treated in a non-surgical manner until
the joint has degenerated sufficiently to mandate surgical
intervention. Minimally invasive repair techniques and/or partial
knee replacement implants may be surgically implanted, but in most
cases the degenerative process will continue, eventually requiring
the implantation of a total knee replacement. As the degenerative
cascade continues, total knee implants that require revision are
typically assumed to involve significant bone loss, and often a
lack of normal bony reference points or landmarks for properly
aligning the implant. In these cases, surgeons often default to the
use of the intramedullary canals of the femur and/or tibia as
landmarks and/or anchoring points for positioning the various
components of the revision prosthesis. Once such intramedullary
stems are in place, further implant revision may be difficult or
impossible, and may involve significantly more invasive procedures
to anchor and/or position the prosthetic components. Alternatively,
joint fusion may eventually be necessary.
[0317] Similar degenerative cascades are faced during virtually all
joint replacement procedures, with each level of surgery typically
involving more invasive surgical procedures, and often requiring
removal of additional joint structure to accommodate the
increasingly invasive revision prosthesis. As with virtually all
types of joints, joint fusion is often the eventual "last
resort."
[0318] One objective of this disclosure is to allow for accurate
pre-operative assessment and modeling of the failed implant and
associated anatomical structures, desirably to facilitate selection
or design and manufacture of a revision implant and associated
surgical tools that facilitate removal of the failed implant,
preparation of the anatomical support structure, and implantation
of the revision implant with preservation of a maximum of the
existing anatomical support structure (i.e., underlying structures
such as cortical and cancellous bone) while ensuring good support
for the revision implant. Moreover, such objectives will desirably
reduce or delay the need for anchoring support from intramedullary
rods, which will desirably be reserved for a "last step" in
revision implant replacement for treating the degenerative
cascade.
[0319] FIG. 1A depicts various exemplary embodiments of a revision
assessment and planning procedure. Initially, an image or images of
the current failed implant and surrounding joint structure will be
taken 10. If available, additional historical image sets will
desirably be obtained 20, and these additional images may be
cross-referenced against the "failed implant" set, as well as
against each other, and evaluated and/or corrected 30. In a related
optional step, some or all of the images and/or processed/evaluated
images will be further evaluated for artifact distortion, and
corrected/evaluated as necessary 40. Eventually, this process will
desirably create a useful set of generated or "final" images for
use in the preparation and planning phase of the implant revision
process.
[0320] The evaluated and/or corrected final image set may then be
used to select and/or create a revision implant, as well as to plan
the surgical procedure and the surgical instruments used therein.
In some embodiments, the revision implant will be chosen from a
pre-formed library of implants 32, or the revision implant may be
created from a pre-existing electronic data file or may be custom
designed as known in the art 34. If an implant is selected from a
pre-formed library, it can, optionally be adapted for the patient's
anatomic or pathological conditions, for example using a CNC or
other abrasion or additive process. Similarly, the final image set
may be utilized to create custom surgical tools 36 for use in
preparation of the anatomical support structures, either before 52
or after 54 removal of some or all of the failed implant components
(or, in certain embodiments, some or all of the implant components
may remain in situ). Once the site has been prepared, and any
failed implant components removed (if desired), the revision
implant is implanted.
i. Jigs and Surgical Alignment Tools
[0321] The various embodiments of this disclosure contemplate the
design and manufacture of numerous surgical tools and jigs useful
for preparing the anatomical structures for the revision implant.
Desirably, the various surgical tools and jigs described herein
will incorporate various patient-specific and/or implant specific
features, including "failed" and revision implant features or
dimensions, which facilitate their use during the preparation of
anatomical structures and implantation of the revision implant
components.
[0322] Aside from patient-specific anatomical features, the various
embodiments contemplate the use of various features of the failed
implant to assist in alignment and/or positioning of the various
surgical tools and/or jigs. For example, it may be desirous to
design and manufacture an alignment jig having one or more surfaces
that fit over and/or abut against a portion of the failed implant
(prior to removal of the failed implant from the patient's
anatomy), optionally with one or more alignment guides for
placement of alignment pins or other indicia (i.e., marker pins for
cutting plane jigs, etc). After placement of such indicia, and
removal of the jig and subsequently the failed implant, the
preparation of the underlying anatomical support structure (for the
revision implant) may proceed as known in the art. In this way, the
use of intramedullary rods and other such alignment guides may be
rendered superfluous and/or obviated, facilitating the preparation
of appropriate bone structures without the sacrifice of unnecessary
additional anatomical structures as is current practice in the
art.
[0323] Table 3 provides a non-exhaustive list of various "failed
implant" features that could be used as anatomical reference points
from alignment and/or placement of surgical tools as described
herein:
TABLE-US-00003 TABLE 3 Useful "Failed Implant" Features for
Alignment Misc Dimensions A/P M/L S/I Combinations thereof Width
Height Length Surfaces Exterior Interior Periphery Mobile features
including dimensions of mobile bearing components Cut Plane
Features Location, dimensions of chamfer and other cuts
Interlocking features (i.e., modular components) Misc. features
Pegs Stems Cavities (Created by Primary Stem)
[0324] In a similar manner, the various embodiments of surgical
tools and/or jigs described herein could include various
combinations of "failed implant" surfaces or features,
patient-specific anatomical features and/or combinations thereof.
For example, a jig could include surfaces that only interact and
align with external surface(s) or other features of the "failed
implant." Alternatively, the jig could include surfaces that only
interact and align with external anatomical features of the patient
(either those accessible with the "failed implant" in position
within the anatomy, or those revealed after removal of some or all
of the "failed implant" components. As another alternative, the jig
could include surfaces that interact and align with both some
external surface feature(s) of the "failed implant" as well as some
accessible anatomical features. In various other embodiments, the
jig may incorporate combinations of the above-listed
interacting/alignment surfaces in concert with other surfaces that
do not interact or align with either "failed implant" or accessible
anatomical surfaces (i.e., surfaces that avoid contact or
alignment, including "anatomical relief" surfaces disclosed in
copending U.S. patent application Ser. No. 13/207,396). In
addition, the jig could include surfaces that interact and align
with the "failed implant" on one articular surface and an
accessible anatomic surface or an anatomic surface revealed after
removal of an implant component on the opposite articular
surface.
[0325] The various jigs and other surgical tools disclosed herein
could have numerous uses during the surgical preparation and
implantation procedure, including (1) as guides for removal of
cement or other biologic and non-biologic material(s), (2) as
alignment and/or depth guides for creating/reaming an
intramedullary canal, (3) as alignment or depth guides for creation
of desirable anatomical features and/or cut planes, (4) as
alignment guides for removal of osteophytes and/or other
undesirable bone features, (5) as guides and/or molds for cement or
other biologic/non-biologic placement, (6) as measuring or
alignment guide for determining size and location of spacers,
wedges, etc., (7) as guides to set a femoral, tibial, humeral,
glenoid or other implant rotation (internal or external),
orientation and/or anteversion or retroversion, flexion or
extension (for the implant and/or a revision implant), (8) as jigs
for ligament balancing, measuring or simulating flexion and
extension gaps, (9) as jigs for placement of augments (spacers,
wedges, etc., including non-patient specific and patient-specific
augments, modular or non-modular components) or having openings or
voids for accommodating augments, (10) as jigs for controlling
component rotation or flexion/extension or ante- or retroversion,
A/P cutting guides (optionally referencing medullary canal or peg
holes from primary implant or from revision implant and/or
anatomical features), (11) as jigs for augment cuts, and/or (12) as
jigs for controlling the alignment of constraining features or
mating components of revision implants. The various jig features
can interact with anatomical and/or "failed implant" features (or
combinations thereof) to align the implant along multiple planes,
displacements and/or at one or more orientations to provide desired
alignment data and/or provide one or more guides for preparation of
the anatomical support structure for the revision implant. These
features can be helpful in implanting devices that have
constraining, mating or interlocking features.
[0326] Table 4 provides an non-exhaustive, exemplary list of
proposed functions for surgical tools and jigs of the present
invention:
TABLE-US-00004 TABLE 4 Surgical Tool and Jig Functions jig for
cement removal femoral shaft hip humerus (patient specific on
cortex, select burr, reamer, etc. on image) burr/ream cement for
removal alignment guides for cutting/reaming/drilling tools patient
specific jig (anterior cortex) setting resection at defined height
(e.g., below tibial plateau, based on information about residual
bone/area of osteolysis, e.g. immediately inferior to or adjacent
to areas of osteolysis) jig for preparing femoral canal for
revision implant/stem facilitates/directs removal of material from
canal cement removal cancellous bone removal existing anchor
removal sets alignment prior to removal of primary stem sets
alignment relative to opposing joint surface or opposing implant
surface after primary stem has been pulled off references off
anterior, posterior or other cortex or resected bone (w/ or w/o
bony defects, osteolysis) references off resected femur (also
tibia, humerus, other bones) references off residual bone cement
surfaces still integrated with bone guides used with "failed
implant" still in position guides used after "failed implant"
removed from joint, mating with bone surfaces (including, for
example osteophytes or osteolytic areas, defects) exposed after
removal of component or after removal of cement Guide facilitates
placement of marker(s) prior to removal of failed implant defect
correction jig to assist in determination/correction of defects,
osteolysis accounts for use of wedges/spacers jigs for setting
anatomical features of implant femoral or tibial rotation, flexion,
extension humeral or glenoid rotation, flexion, extension jigs for
placing markers having known or desirable alignment features
relative to anatomic axis relative to mechanical axis of joint or
limb relative to intramedullary shaft relative to endosteal bone
relative to cortical bone relative to residual cement relative to
exposed bone surface after removal of implant and cement relative
to opposing surfaces of implant relative to articulating surfaces
of existing or "failed implant" relative to constraining,
interlocking or mating implant components relative to bearing
surfaces relative to damaged polyethylene surfaces relative to
undamaged polyethylene surfaces
[0327] The following list provides various combinations of
implants, jigs and support/alignment surfaces using tibia as an
example contemplated by the present embodiments: [0328] Tibia:
[0329] Implant removal tool [0330] Cement removal tools [0331]
Burrs [0332] Drills [0333] Canal Preparation Tools (Reamers) [0334]
Provisional canal stem [0335] Tibial boom (on top of stem) [0336]
Cutting guides (slots) on boom [0337] Extramedullary arch (external
guide rod holder) [0338] Alignment rod (to arch) to determine
mechanical axis [0339] Tibial depth resection guage (for lateral
saw cut) [0340] Tibial cutting head (pinned to tibia) [0341] Stem
provisional adapter (stabilizes the cutting saw) [0342] Make cut
(flat tibial plane now created) [0343] Choose proper sizing plates
by comparing them on resected tibial surface Use alignment rod to
verify vagus/varus alignment [0344] Reinsert last intramedullary
reamer or stem provisional assembly [0345] Slide sizing plate over
reamer/stem and seat (to align relative to stem) [0346] Confirm use
of proper wedges (if needed) and sizing plate [0347] Pin the plate
[0348] Remove reamer/stem (use offset stem if necessary--or tibial
augmentation) Drill stem base for cemented stem [0349] Use broach
impactor [0350] Remove broach impactor and sizing plate [0351]
Trial the tibial plate/stem
A. The Joint Replacement Procedure
[0352] i. Knee Joint
[0353] Performing a total knee arthroplasty (primary or revision
procedure) is a complicated procedure. In replacing the knee with
an artificial knee (or revising a failed or failing knee implant),
it is important to get the anatomical and mechanical axes of the
lower extremity aligned correctly to ensure optimal functioning of
the implanted knee.
[0354] As shown in FIG. 11A, the center of the hip 1902 (located at
the head 1930 of the femur 1932), the center of the knee 1904
(located at the notch where the intercondular tubercle 1934 of the
tibia 1936 meet the femur) and ankle 1906 lie approximately in a
straight line 1910 which defines the mechanical axis of the lower
extremity. The anatomic axis 1920 aligns 5-7.degree. offset .theta.
from the mechanical axis in the valgus, or outward, direction.
[0355] The long axis of the tibia 1936 is collinear with the
mechanical axis of the lower extremity 1910. From a
three-dimensional perspective, the lower extremity of the body
ideally functions within a single plane known as the median
anterior-posterior plane (MAP-plane) throughout the
flexion-extension arc. In order to accomplish this, the femoral
head 1930, the mechanical axis of the femur, the patellar groove,
the intercondylar notch, the patellar articular crest, the tibia
and the ankle remain within the MAP-plane during the
flexion-extension movement. During movement, the tibia rotates as
the knee flexes and extends in the epicondylar axis which is
perpendicular to the MAP-plane.
[0356] A variety of image slices can be taken at each individual
joint, e.g., the knee joint 1950-1950, and the hip joint 1952-1950,
These image slices can be used as described above in Section I
along with an image of the full leg to ascertain the axis.
[0357] With disease and malfunction of the knee, alignment of the
anatomic axis is altered. Performing a total knee arthroplasty is
one solution for correcting a diseased knee. Implanting a total
knee joint, such as the PFC Sigma RP Knee System by Johnson &
Johnson, requires that a series of resections be made to the
surfaces forming the knee joint in order to facilitate installation
of the artificial knee. The resections should be made to enable the
installed artificial knee to achieve flexion-extension movement
within the MAP-plane and to optimize the patient's anatomical and
mechanical axis of the lower extremity.
[0358] First, the tibia 1930 is resected to create a flat surface
to accept the tibial component of the implant. In most cases, the
tibial surface is resected perpendicular to the long axis of the
tibia in the coronal plane, but is typically sloped 4-7.degree.
posteriorly in the sagittal plane to match the normal slope of the
tibia. As will be appreciated by those of skill in the art, the
sagittal slope can be 0.degree. where the device to be implanted
does not require a sloped tibial cut. The resection line 1958 is
perpendicular to the mechanical axis 1910, but the angle between
the resection line and the surface plane of the plateau 1960 varies
depending on the amount of damage to the knee.
[0359] FIGS. 11B-D illustrate an anterior view of a resection of an
anatomically normal tibial component, a tibial component in a varus
knee, and a tibial component in a valgus knee, respectively. In
each figure, the mechanical axis 1910 extends vertically through
the bone and the resection line 1958 is perpendicular to the
mechanical axis 1910 in the coronal plane, varying from the surface
line formed by the joint depending on the amount of damage to the
joint. FIG. 11B illustrates a normal knee wherein the line
corresponding to the surface of the joint 1960 is parallel to the
resection line 1958. FIG. 11C illustrates a varus knee wherein the
line corresponding to the surface of the joint 1960 is not parallel
to the resection line 1958. FIG. 11D illustrates a valgus knee
wherein the line corresponding to the surface of the joint 1960 is
not parallel to the resection line 1958.
[0360] Once the tibial surface has been prepared, the surgeon turns
to preparing the femoral condyle.
[0361] The plateau of the femur 1970 is resected to provide flat
surfaces that communicate with the interior of the femoral
prosthesis. The cuts made to the femur are based on the overall
height of the gap to be created between the tibia and the femur.
Typically, a 20 mm gap is desirable to provide the implanted
prosthesis adequate room to achieve full range of motion. The bone
is resected at a 5-7.degree. angle valgus to the mechanical axis of
the femur. Resected surface 1972 forms a flat plane with an angular
relationship to adjoining surfaces 1974, 1976. The angle .theta.',
.theta.'' between the surfaces 1972-1974, and 1972-1976 varies
according to the design of the implant.
ii. Hip Joint
[0362] As illustrated in FIG. 11F, the external geometry of the
proximal femur includes the head 1980, the neck 1982, the lesser
trochanter 1984, the greater trochanter 1986 and the proximal
femoral diaphysis. The relative positions of the trochanters 1984,
1986, the femoral head center 1902 and the femoral shaft 1988 are
correlated with the inclination of the neck-shaft angle. The
mechanical axis 1910 and anatomic axis 1920 are also shown.
Assessment of these relationships can change the reaming direction
to achieve neutral alignment of the prosthesis with the femoral
canal.
[0363] Using anteroposterior and lateral radiographs, measurements
are made of the proximal and distal geometry to determine the size
and optimal design of the implant.
[0364] Typically, after obtaining surgical access to the hip joint,
the femoral neck 1982 is resected, e.g. along the line 1990. Once
the neck is resected, the medullary canal is reamed. Reaming can be
accomplished, for example, with a conical or straight reamer, or a
flexible reamer. The depth of reaming is dictated by the specific
design of the implant. Once the canal has been reamed, the proximal
reamer is prepared by serial rasping, with the rasp directed down
into the canal.
B. Surgical Tools
[0365] Further, surgical assistance can be provided by using a
device applied to the outer surface of the articular cartilage, the
bone, including the subchondral bone, in order to match the
alignment of the articular repair system and the recipient site or
the joint. The device can be round, circular, oval, ellipsoid,
curved or irregular in shape. The shape can be selected or adjusted
to match or enclose an area of diseased cartilage or an area
slightly larger than the area of diseased cartilage or
substantially larger than the diseased cartilage. The area can
encompass the entire articular surface or the weight bearing
surface. Such devices are typically preferred when replacement of a
majority or an entire articular surface is contemplated.
[0366] Mechanical devices can be used for surgical assistance
(e.g., surgical tools), for example using gels, molds, plastics or
metal. One or more electronic images or intraoperative measurements
can be obtained providing object coordinates that define the
articular and/or bone surface and shape. These objects' coordinates
can be utilized to either shape the device, e.g. using a CAD/CAM
technique, to be adapted to a patient's articular anatomy or,
alternatively, to select a typically pre-made device that has a
good fit with a patient's articular anatomy. The device can have a
surface and shape that will substantially match or conform to all
or portions of the articular cartilage, subchondral bone and/or
other bone surface and shape, e.g., similar to a "negative." The
device can include, without limitation, one or more cut planes,
apertures, slots and/or holes to accommodate surgical instruments
such as drills, reamers, curettes, k-wires, screws and saws.
[0367] The device may have a single component or multiple
components. The components may be attached to the unoperated and
operated portions of the intra- or extra-articular anatomy. For
example, one component may be attached to the femoral neck, while
another component may be in contact with the greater or lesser
trochanter. Typically, the different components can be used to
assist with different parts of the surgical procedure. When
multiple components are used, one or more components may also be
attached to a different component rather than the articular
cartilage, subchondral bone or other areas of osseous or
non-osseous anatomy. For example, a tibial mold may be attached to
a femoral mold and tibial cuts can be performed in reference to
femoral cuts.
[0368] Components may also be designed to fit to the joint after an
operative step has been performed. For example, in a knee, one
component may be designed to fit all or portions of a distal femur
before any cuts have been made, while another component may be
designed to fit on a cut that has been made with the previously
used mold or component. In a hip, one component may be used to
perform an initial cut, for example through the femoral neck, while
another subsequently used component may be designed to fit on the
femoral neck after the cut, for example covering the area of the
cut with a central opening for insertion of a reamer. Using this
approach, subsequent surgical steps may also be performed with high
accuracy, e.g. reaming of the marrow cavity.
[0369] In another embodiment, a guide may be attached to a mold to
control the direction and orientation of surgical instruments. For
example, after the femoral neck has been cut, a mold may be
attached to the area of the cut, whereby it fits portions or all of
the exposed bone surface. The mold may have an opening adapted for
a reamer. Before the reamer is introduced a femoral reamer guide
may be inserted into the mold and advanced into the marrow cavity.
The position and orientation of the reamer guide may be determined
by the femoral mold. The reamer can then be advanced over the
reamer guide and the marrow cavity can be reamed with improved
accuracy. Similar approaches are feasible in the knee and other
joints.
[0370] All mold components may be disposable. Alternatively, some
molds components may be re-usable. Typically, mold components
applied after a surgical step such as a cut as been performed can
be reuseable, since a reproducible anatomic interface will have
been established.
[0371] Interconnecting or bridging components may be used. For
example, such interconnecting or bridging components may couple the
mold attached to the joint with a standard, preferably unmodified
or only minimally modified cut block used during knee or hip
surgery. Interconnecting or bridging components may be made of
plastic or metal. When made of metal or other hard material, they
can help protect the joint from plastic debris, for example when a
reamer or saw would otherwise get into contact with the mold.
[0372] The accuracy of the attachment between the component or mold
and the cartilage or subchondral bone or other osseous structures
is typically better than 2 mm, more preferred better than 1 mm,
more preferred better than 0.7 mm, more preferred better than 0.5
mm, or even more preferred better than 0.5 mm. The accuracy of the
attachment between different components or between one or more
molds and one or more surgical instruments is typically better than
2 mm, more preferred better than 1 mm, more preferred better than
0.7 mm, more preferred better than 0.5 mm, or even more preferred
better than 0.5 mm.
[0373] The angular error of any attachments or between any
components or between components, molds, instruments and/or the
anatomic or biomechanical axes is preferably less than 2 degrees,
more preferably less than 1.5 degrees, more preferably less than 1
degree, and even more preferably less than 0.5 degrees. The total
angular error is preferably less than 2 degrees, more preferably
less than 1.5 degrees, more preferably less than 1 degree, and even
more preferably less than 0.5 degrees.
[0374] Typically, a position will be chosen that will result in an
anatomically desirable cut plane, drill hole, or general instrument
orientation for subsequent placement of an articular repair system
or for facilitating placement of the articular repair system.
Moreover, the device can be designed so that the depth of the
drill, reamer or other surgical instrument can be controlled, e.g.,
the drill cannot go any deeper into the tissue than defined by the
device, and the size of the hole in the block can be designed to
essentially match the size of the implant. Information about other
joints or axis and alignment information of a joint or extremity
can be included when selecting the position of these slots or
holes. Alternatively, the openings in the device can be made larger
than needed to accommodate these instruments. The device can also
be configured to conform to the articular shape. The apertures, or
openings, provided can be wide enough to allow for varying the
position or angle of the surgical instrument, e.g., reamers, saws,
drills, curettes and other surgical instruments. An instrument
guide, typically comprised of a relatively hard material, can then
be applied to the device. The device helps orient the instrument
guide relative to the three-dimensional anatomy of the joint.
[0375] The mold may contact the entire articular surface. In
various embodiments, the mold can be in contact with only a portion
of the articular surface. Thus, the mold can be in contact, without
limitation, with: 100% of the articular surface; 80% of the
articular surface; 50% of the articular surface; 30% of the
articular surface; 30% of the articular surface; 20% of the
articular surface; or 10% or less of the articular surface. An
advantage of a smaller surface contact area is a reduction in size
of the mold thereby enabling cost efficient manufacturing and, more
important, minimally invasive surgical techniques. The size of the
mold and its surface contact areas have to be sufficient, however,
to ensure accurate placement so that subsequent drilling and
cutting can be performed with sufficient accuracy.
[0376] In various embodiments, the maximum diameter of the mold is
less than 10 cm. In other embodiments, the maximum diameter of the
mold may be less than: 8 cm; 5 cm; 4 cm; 3 cm; or even less than 2
cm.
[0377] The mold may be in contact with three or more surface points
rather than an entire surface. These surface points may be on the
articular surface or external to the articular surface. By using
contact points rather than an entire surface or portions of the
surface, the size of the mold may be reduced.
[0378] Reductions in the size of the mold can be used to enable
minimally invasive surgery (MIS) in the hip, the knee, the shoulder
and other joints. MIS technique with small molds will help to
reduce intraoperative blood loss, preserve tissue including
possibly bone, enable muscle sparing techniques and reduce
postoperative pain and enable faster recovery. Thus, in one
embodiment of this disclosure the mold is used in conjunction with
a muscle sparing technique. In another embodiment, the mold may be
used with a bone sparing technique. In another embodiment, the mold
is shaped to enable MIS technique with an incision size of less
than 15 cm, or, more preferred, less than 13 cm, or, more
preferred, less than 10 cm, or, more preferred, less than 8 cm, or,
more preferred, less than 6 cm.
[0379] The mold may be placed in contact with points or surfaces
outside of the articular surface. For example, the mold can rest on
bone in the intercondylar notch or the anterior or other aspects of
the tibia or the acetabular rim or the lesser or greater
trochanter. Optionally, the mold may only rest on points or
surfaces that are external to the articular surface. Furthermore,
the mold may rest on points or surfaces within the weight-bearing
surface, or on points or surfaces external to the weight-bearing
surface.
[0380] The mold may be designed to rest on bone or cartilage
outside the area to be worked on, e.g. cut, drilled etc. In this
manner, multiple surgical steps can be performed using the same
mold. For example, in the knee, the mold may be stabilized against
portions of the intercondylar notch, which can be selected external
to areas to be removed for total knee arthroplasty or other
procedures. In the hip, the mold may be attached external to the
acetabular fossa, providing a reproducible reference that is
maintained during a procedure, for example total hip arthroplasty.
The mold may be affixed to the underlying bone, for example with
pins or drills etc.
[0381] In additional embodiments, the mold may rest on the
articular cartilage. The mold may rest on the subchondral bone or
on structures external to the articular surface that are within the
joint space or on structures external to the joint space. If the
mold is designed to rest on the cartilage, an imaging test
demonstrating the articular cartilage can be used in one
embodiment. This can, for example, include ultrasound, spiral CT
arthrography, MRI using, for example, cartilage displaying pulse
sequences, or MRI arthrography. In another embodiment, an imaging
test demonstrating the subchondral bone, e.g. CT or spiral CT, can
be used and a standard cartilage thickness can be added to the
scan. The standard cartilage thickness can be derived, for example,
using an anatomic reference database, age, gender, and race
matching, age adjustments and any method known in the art or
developed in the future for deriving estimates of cartilage
thickness. The standard cartilage thickness may, in some
embodiments, be uniform across one or more articular surfaces or it
can change across the articular surface.
[0382] The mold may be adapted to rest substantially on subchondral
bone. In this case, residual cartilage can create some offset and
inaccurate result with resultant inaccuracy in surgical cuts,
drilling and the like. In one embodiment, the residual cartilage is
removed in a first step in areas where the mold is designed to
contact the bone and the subchondral bone is exposed. In a second
step, the mold is then placed on the subchondral bone.
[0383] In various alternative embodiments, the mold may include one
or more surfaces that contact or interact with (i.e., match or
substantially conform to) surfaces of a "failed implant".
[0384] With advanced osteoarthritis, significant articular
deformity can result. The articular surface(s) can become
flattened. There can be cyst formation or osteophyte formation.
"Tram track" like structures can form on the articular surface. In
one embodiment, osteophytes or other deformities may be removed by
the computer software prior to generation of the mold. The software
can automatically, semi-automatically or manually with input from
the user simulate surgical removal of the osteophytes or other
deformities, and predict the resulting shape of the joint and the
associated surfaces. The mold can then be designed based on the
predicted shape. Intraoperatively, these osteophytes or other
deformities can then also optionally be removed prior to placing
the mold and performing the procedure. Alternatively, the mold can
be designed to avoid such deformities. For example, the mold may
only be in contact with points on the articular surface or external
to the articular surface that are not affected or involved by
osteophytes. The mold can rest on the articular surface or external
to the articular surface on three or more points or small surfaces
with the body of the mold elevated or detached from the articular
surface so that the accuracy of its position cannot be affected by
osteophytes or other articular deformities. The mold can rest on
one or more tibial spines or portions of the tibial spines.
Alternatively, all or portions of the mold may be designed to rest
on osteophytes or other excrescences or pathological changes.
[0385] The surgeon can, optionally, make fine adjustments between
the alignment device and the instrument guide. In this manner, an
optimal compromise can be found, for example, between biomechanical
alignment and joint laxity or biomechanical alignment and joint
function, e.g. in a knee joint flexion gap and extension gap. By
oversizing the openings in the alignment guide, the surgeon can
utilize the instruments and insert them in the instrument guide
without damaging the alignment guide. Thus, in particular if the
alignment guide is made of plastic, debris will not be introduced
into the joint. The position and orientation between the alignment
guide and the instrument guide can be also be optimized with the
use of, for example, interposed spacers, wedges, screws and other
mechanical or electrical methods known in the art.
[0386] A surgeon may desire to influence joint laxity as well as
joint alignment. This can be optimized for different flexion and
extension, abduction, or adduction, internal and external rotation
angles. For this purpose, for example, spacers can be introduced
that are attached or that are in contact with one or more molds.
The surgeon can intraoperatively evaluate the laxity or tightness
of a joint using spacers with different thickness or one or more
spacers with the same thickness. For example, spacers can be
applied in a knee joint in the presence of one or more molds and
the flexion gap can be evaluated with the knee joint in flexion.
The knee joint can then be extended and the extension gap can be
evaluated. Ultimately, the surgeon will select an optimal
combination of spacers for a given joint and mold. A surgical cut
guide can be applied to the mold with the spacers optionally
interposed between the mold and the cut guide. In this manner, the
exact position of the surgical cuts can be influenced and can be
adjusted to achieve an optimal result. Thus, the position of a mold
can be optimized relative to the joint, bone or cartilage for
soft-tissue tension, ligament balancing or for flexion, extension,
rotation, abduction, adduction, anteversion, retroversion and other
joint or bone positions and motion. The position of a cut block or
other surgical instrument may be optimized relative to the mold for
soft-tissue tension or for ligament balancing or for flexion,
extension, rotation, abduction, adduction, anteversion,
retroversion and other joint or bone positions and motion. Both the
position of the mold and the position of other components including
cut blocks and surgical instruments may be optimized for
soft-tissue tension or for ligament balancing or for flexion,
extension, rotation, abduction, adduction, anteversion,
retroversion and other joint or bone positions and motion.
[0387] Someone skilled in the art will recognize other means for
optimizing the position of the surgical cuts or other
interventions. As stated above, expandable or ratchet-like devices
may be utilized that can be inserted into the joint or that can be
attached or that can touch the mold (see also FIG. 27D). Such
devices can extend from a cutting block or other devices attached
to the mold, optimizing the position of drill holes or cuts for
different joint positions or they can be integrated inside the
mold. Integration in the cutting block or other devices attached to
the mold is preferable, since the expandable or ratchet-like
mechanisms can be sterilized and re-used during other surgeries,
for example in other patients. Optionally, the expandable or
ratchet-like devices may be disposable. The expandable or ratchet
like devices may extend to the joint without engaging or contacting
the mold; alternatively, these devices may engage or contact the
mold. Hinge-like mechanisms are applicable. Similarly, jack-like
mechanisms are useful. In principal, any mechanical or electrical
device useful for fine-tuning the position of the cut guide
relative to the molds may be used. These embodiments are helpful
for soft-tissue tension optimization and ligament balancing in
different joints for different static positions and during joint
motion.
[0388] A surgeon may desire to influence joint laxity as well as
joint alignment. This can be optimized for different flexion and
extension, abduction, or adduction, internal and external rotation
angles. For this purpose, for example, spacers or expandable or
ratchet-like can be utilized that can be attached or that can be in
contact with one or more molds. The surgeon can intraoperatively
evaluate the laxity or tightness of a joint using spacers with
different thickness or one or more spacers with the same thickness
or using such expandable or ratchet like devices. For example,
spacers or a ratchet like device can be applied in a knee joint in
the presence of one or more molds and the flexion gap can be
evaluated with the knee joint in flexion. The knee joint can then
be extended and the extension gap can be evaluated. Ultimately, the
surgeon will select an optimal combination of spacers or an optimal
position for an expandable or ratchet-like device for a given joint
and mold. A surgical cut guide can be applied to the mold with the
spacers or the expandable or ratchet-like device optionally
interposed between the mold and the cut guide or, in select
embodiments, between the mold and the joint or the mold and an
opposite articular surface. In this manner, the exact position of
the surgical cuts can be influenced and can be adjusted to achieve
an optimal result. Someone skilled in the art will recognize other
means for optimizing the position of the surgical cuts or drill
holes. For example, expandable or ratchet-like devices can be
utilized that can be inserted into the joint or that can be
attached or that can touch the mold. Hinge-like mechanisms are
applicable. Similarly, jack-like mechanisms are useful. In
principal, any mechanical or electrical device useful for
fine-tuning the position of the cut guide relative to the molds can
be used.
[0389] The template and any related instrumentation such as spacers
or ratchets can be combined with a tensiometer to provide a better
intraoperative assessment of the joint. The tensiometer can be
utilized to further optimize the anatomic alignment and tightness
of the joint and to improve post-operative function and outcomes.
Optionally, local contact pressures may be evaluated
intraoperatively, for example using a sensor like the ones
manufactured by Tekscan, South Boston, Mass. The contact pressures
can be measured between the mold and the joint or between the mold
and any attached devices such as a surgical cut block.
[0390] The template may be a mold that can be made of a plastic or
polymer. The mold may be produced by rapid prototyping technology,
in which successive layers of plastic are laid down, as know in the
art. In other embodiments, the template or portions of the template
can be made of metal. The mold can be milled or made using laser
based manufacturing techniques.
[0391] The template may be casted using rapid prototyping and, for
example, lost wax technique. It may also be milled. For example, a
preformed mold with a generic shape can be used at the outset,
which can then be milled to the patient specific dimensions. The
milling may only occur on one surface of the mold, preferably the
surface that faces the articular surface. Milling and rapid
prototyping techniques may be combined.
[0392] Curable materials may be used which can be poured into forms
that are, for example, generated using rapid prototyping. For
example, liquid metal may be used. Cured materials may optionally
be milled or the surface can be further refined using other
techniques.
[0393] Metal inserts may be applied to plastic components. For
example, a plastic mold may have at least one guide aperture to
accept a reaming device or a saw. A metal insert may be used to
provide a hard wall to accept the reamer or saw. Using this or
similar designs can be useful to avoid the accumulation of plastic
or other debris in the joint when the saw or other surgical
instruments may get in contact with the mold. Other hard materials
can be used to serve as inserts. These can also include, for
example, hard plastics or ceramics.
[0394] In another embodiment, the mold does not have metallic
inserts to accept a reaming device or saw. The metal inserts or
guides may be part of an attached device that is typically in
contact with the mold. A metallic drill guide or a metallic saw
guide may thus, for example, have metallic or hard extenders that
reach through the mold thereby, for example, also stabilizing any
devices applied to the mold against the physical body of the
mold.
[0395] The template may not only be used for assisting the surgical
technique and guiding the placement and direction of surgical
instruments. In addition, the templates can be utilized for guiding
the placement of the implant or implant components. For example, in
the hip joint, tilting of the acetabular component is a frequent
problem with total hip arthroplasty. A template can be applied to
the acetabular wall with an opening in the center large enough to
accommodate the acetabular component that the surgeon intends to
place. The template can have receptacles or notches that match the
shape of small extensions that can be part of the implant or that
can be applied to the implant. For example, the implant can have
small members or extensions applied to the twelve o'clock and six
o'clock positions. See, for example, FIG. 9A-D, discussed below. By
aligning these members with notches or receptacles in the mold, the
surgeon can ensure that the implant is inserted without tilting or
rotation. These notches or receptacles can also be helpful to hold
the implant in place while bone cement is hardening in cemented
designs.
[0396] One or more templates can be used during the surgery. For
example, in the hip, a template can be initially applied to the
proximal femur that closely approximates the 3D anatomy prior to
the resection of the femoral head. The template can include an
opening to accommodate a saw (see FIGS. 8-9). The opening is
positioned to achieve an optimally placed surgical cut for
subsequent reaming and placement of the prosthesis. A second
template can then be applied to the proximal femur after the
surgical cut has been made. The second template can be useful for
guiding the direction of a reamer prior to placement of the
prosthesis. As can be seen in this, as well as in other examples,
templates can be made for joints prior to any surgical
intervention. However, it is also possible to make templates that
are designed to fit to a bone, portions of a joint and/or surface
of a "failed implant" after the surgeon has already performed
selected surgical procedures, such as cutting, reaming, drilling,
etc. The template can account for the shape of the bone or the
joint resulting from these procedures.
[0397] In certain embodiments, the surgical assistance device
comprises an array of adjustable, closely spaced pins (e.g.,
plurality of individually moveable mechanical elements). One or
more electronic images or intraoperative measurements can be
obtained providing object coordinates that define the articular
and/or bone surface and shape. These objects' coordinates can be
entered or transferred into the device, for example manually or
electronically, and the information can be used to create a surface
and shape that will match all or portions of the articular and/or
bone surface and shape by moving one or more of the elements, e.g.
similar to an "image." The device can include slots and holes to
accommodate surgical instruments such as drills, curettes, k-wires,
screws and saws. The position of these slots and holes may be
adjusted by moving one or more of the mechanical elements.
Typically, a position will be chosen that will result in an
anatomically desirable cut plane, reaming direction, or drill hole
or instrument orientation for subsequent placement of an articular
repair system or for facilitating the placement of an articular
repair system.
[0398] Information about other joints or axis and alignment
information of a joint or extremity can be included when selecting
the position of the, without limitation, cut planes, apertures,
slots or holes on the template, in accordance with an embodiment of
the invention. The biomechanical and/or anatomic axes may be
derived using above-described imaging techniques including, without
limitation, a standard radiograph, including a load bearing
radiograph, for example an upright knee x-ray or a whole leg length
film (e.g., hip to foot) These radiographs may be acquired in
different projections, for example anteroposterior,
posteroanterior, lateral, oblique etc. The biomechanical and
anatomic axes may also be derived using other imaging modalities
such as CT scan or MRI scan, a CT scout scan or MRI localized scans
through portions or all of the extremity, either alone or in
combination, as described in above embodiments. For example, when
total or partial knee arthroplasty is contemplated, a spiral CT
scan may be obtained through the knee joint. The spiral CT scan
through the knee joint serves as the basis for generating the
negative contour template(s)/mold(s) that will be affixed to
portions or all of the knee joint. Additional CT or MRI scans may
be obtained through the hip and ankle joint. These may be used to
define the centroids or centerpoints in each joint or other
anatomic landmarks, for example, and then to derive the
biomechanical and other axes.
[0399] In another embodiment, the mechanical axis may be
established using non-image based approaches including traditional
surgical instruments and measurement tools such as intramedullary
rods, alignment guides and also surgical navigation. For example,
in a knee joint, optical or radiofrequency markers can be attached
to the extremity. The lower limb may then be rotated around the hip
joint and the position of the markers can be recorded for different
limb positions. The center of the rotation will determine the
center of the femoral head. Similar reference points may be
determined in the ankle joint etc. The position of the templates
or, more typically, the position of surgical instruments relative
to the templates may then be optimized for a given biomechanical
load pattern, for example in varus or valgus alignment. Thus, by
performing these measurements pre- or intraoperatively, the
position of the surgical instruments may be optimized relative to
the molds and the cuts can be placed to correct underlying axis
errors such as varus or valgus malalignment or ante- or
retroversion.
[0400] Upon imaging, a physical template of a joint, such as a knee
joint, or hip joint, or ankle joint or shoulder joint is generated,
in accordance with an embodiment of the invention. The template can
be modified or analyzed using additional image groups, as
previously described, and can be used to perform image guided
surgical procedures such as partial or complete joint replacement,
articular resurfacing, or ligament repair. The template may include
reference points or opening or apertures for surgical instruments
such as drills, saws, burrs and the like.
[0401] In order to derive the preferred orientation of drill holes,
cut planes, saw planes and the like, openings or receptacles in
said template or attachments will be adjusted to account for at
least one axis (e.g., mechanical or anatomical). The axis can be
anatomic or mechanical, for example, for a knee joint, a hip joint,
an ankle joint, a shoulder joint or an elbow joint.
[0402] In one embodiment, only a single axis (e.g., mechanical or
anatomical) is used for placing and optimizing such drill holes,
saw planes, cut planes, and or other surgical interventions. This
axis may be, for example, an anatomical or mechanical axis. In a
preferred embodiment, a combination of axis and/or planes can be
used for optimizing the placement of the drill holes, saw planes,
cut planes or other surgical interventions. For example, two axes
(e.g., one anatomical and one biomechanical) can be factored into
the position, shape or orientation of the 3D guided template and
related attachments or linkages. For example, two axes, (e.g., one
anatomical and biomechanical) and one plane (e.g., the top plane
defined by the tibial plateau), can be used. Alternatively, two or
more planes can be used (e.g., a coronal and a sagittal plane), as
defined by the image or by the patients anatomy.
[0403] Angle and distance measurements and surface topography
measurements may be performed in these one or more, preferably two
or more, preferably three or more multiple planes, as necessary.
These angle measurements can, for example, yield information on
varus or valgus deformity, flexion or extension deficit, hyper or
hypo-flexion or hyper- or hypo-extension, abduction, adduction,
internal or external rotation deficit, or hyper- or hypo-abduction,
hyper- or hypo-adduction, hyper- or hypo-internal or external
rotation.
[0404] Single or multi-axis line or plane measurements can then be
utilized to determine preferred angles of correction, e.g., by
adjusting surgical cut or saw planes or other surgical
interventions. Typically, two axis corrections will be preferred
over a single axis correction, a two plane correction will be
preferred over a single plane correction and so forth.
[0405] In accordance with another embodiment, more than one
drilling, cut, boring and/or reaming or other surgical intervention
is performed for a particular treatment such as the placement of a
joint resurfacing or replacing implant, or components thereof.
These two or more surgical interventions (e.g., drilling, cutting,
reaming, sawing) are made in relationship to a mechanical axis,
and/or an anatomical axis and/or an implant axis. The 3D guidance
template or attachments or linkages thereto include two or more
openings, guides, apertures or reference planes to make at least
two or more drillings, reamings, borings, sawings or cuts in
relationship to a mechanical axis, an anatomical axis, an implant
axis or other axis derived therefrom or related thereto.
[0406] While in simple embodiments it is possible that only a
single cut or drilling will be made in relationship to a mechanical
axis, an anatomical axis, an implant axis and/or an axis related
thereto, in most meaningful implementations, two or more drillings,
borings, reamings, cuttings and/or sawings will be performed or
combinations thereof in relationship to a biomechanical, anatomical
and/or implant axis.
[0407] For example, an initial cut may be placed in relationship to
a mechanical axis of particular joint. A subsequent drilling, cut
or other intervention can be performed in relation to an anatomical
axis. Both can be designed to achieve a correction in a mechanical
axis and/or anatomical axis. In another example, an initial cut can
be performed in relationship to a mechanical axis, while a
subsequent cut is performed in relationship to an implant axis or
an implant plane. Any combination in surgical interventions and in
relating them to any combination of biomechanical, anatomical,
implant axis or planes related thereto is possible. In many
embodiments, it is desirable that a single cut or drilling be made
in relationship to a biomechanical or anatomical axis. Subsequent
cuts or drillings or other surgical interventions can then be made
in reference to said first intervention. These subsequent
interventions can be performed directly off the same 3D guidance
template or they can be performed by attaching surgical instruments
or linkages or reference frames or secondary or other templates to
the first template or the cut plane or hole and the like created
with the first template.
[0408] FIG. 12 shows an example of a surgical tool 410 having one
surface 400 matching the geometry of an articular surface of the
joint. Also shown is an aperture 415 in the tool 410 capable of
controlling drill depth and width of the hole and allowing
implantation or insertion of implant 420 having a press-fit
design.
[0409] In another embodiment, a frame can be applied to the bone or
the cartilage in areas other than the diseased bone or cartilage.
The frame can include holders and guides for surgical instruments.
The frame can be attached to one or preferably more previously
defined anatomic reference points. Alternatively, the position of
the frame can be cross-registered relative to one, or more,
anatomic landmarks, using an imaging test or intraoperative
measurement, for example one or more fluoroscopic images acquired
intraoperatively. One or more electronic images or intraoperative
measurements including using mechanical devices can be obtained
providing object coordinates that define the articular and/or bone
surface and shape. These objects' coordinates can be entered or
transferred into the device, for example manually or
electronically, and the information can be used to move one or more
of the holders or guides for surgical instruments. Typically, a
position will be chosen that will result in a surgically or
anatomically desirable cut plane or drill hole orientation for
subsequent placement of an articular repair system. Information
about other joints or axis and alignment information of a joint or
extremity can be included when selecting the position of these
slots or holes.
[0410] Furthermore, re-useable tools (e.g., templates or molds) can
be also be created and employed. Non-limiting examples of
re-useable materials include putties and other deformable materials
(e.g., an array of adjustable closely spaced pins that can be
configured to match the topography of a joint surface).
[0411] In various embodiments, the template may include a reference
element, such as a pin, that upon positioning of the template on
the articular surface, establishes a reference plane relative to a
mechanical axis or an anatomical axis or plane of a limb. For
example, in a knee surgery the reference element may establish a
reference plane from the center of the hip to the center of the
ankle. In other embodiments, the reference element may establish an
axis that subsequently be used a surgical tool to correct an axis
deformity.
[0412] In these embodiments, the template can be created directly
from the joint during surgery or, alternatively, created from an
image of the joint, for example, using one or more computer
programs to determine object coordinates defining the surface
contour of the joint and transferring (e.g., dialing-in) these
co-ordinates to the tool. Subsequently, the tool can be aligned
accurately over the joint and/or existing implant component and,
accordingly, the surgical instrument guide or the implant will be
more accurately placed in or over the articular surface.
[0413] In both single-use and re-useable embodiments, the tool can
be designed so that the instrument controls the depth and/or
direction of the drill, i.e., the drill cannot go any deeper into
the tissue than the instrument allows, and the size of the hole or
aperture in the instrument can be designed to essentially match the
size of the implant. The tool can be used for general prosthesis
implantation, including, but not limited to, the articular repair
implants described herein and for reaming the marrow in the case of
a total arthroplasty.
[0414] These surgical tools (devices) can also be used to remove an
area of diseased cartilage and underlying bone or an area slightly
larger than the diseased cartilage and underlying bone. In
addition, the device can be used on a "donor," e.g., a cadaveric
specimen, to obtain implantable repair material. The device is
typically positioned in the same general anatomic area in which the
tissue was removed in the recipient. The shape of the device is
then used to identify a donor site providing a seamless or near
seamless match between the donor tissue sample and the recipient
site. This can be achieved by identifying the position of the
device in which the articular surface in the donor, e.g. a
cadaveric specimen, has a seamless or near seamless contact with
the inner surface when applied to the cartilage.
[0415] The device can be molded, rapid prototyped, machine and/or
formed based on the size of the area of diseased cartilage and
based on the curvature of the cartilage or the underlying
subchondral bone or a combination of both or using adjacent
structures inside or external to the joint space. The device can
take into consideration surgical removal of, for example, the
meniscus, in arriving at a joint surface configuration.
[0416] In one embodiment, the device can then be applied to the
donor, (e.g., a cadaveric specimen) and the donor tissue can be
obtained with use of a blade or saw or other tissue removing
device. The device can then be applied to the recipient in the area
of the joint and the diseased cartilage, where applicable, and
underlying bone can be removed with use of a blade or saw or other
tissue cutting device whereby the size and shape of the removed
tissue containing the diseased cartilage will closely resemble the
size and shape of the donor tissue. The donor tissue can then be
attached to the recipient site. For example, said attachment can be
achieved with use of screws or pins (e.g., metallic, non-metallic
or bioresorable) or other fixation means including but not limited
to a tissue adhesive. Attachment can be through the cartilage
surface or alternatively, through the marrow space.
[0417] The implant site can be prepared with use of a robotic
device. The robotic device can use information from an electronic
image for preparing the recipient site.
[0418] Identification and preparation of the implant site and
insertion of the implant can be supported by a surgical navigation
system. In such a system, the position or orientation of a surgical
instrument with respect to the patient's anatomy can be tracked in
real-time in one or more 2D or 3D images. These 2D or 3D images can
be calculated from images that were acquired preoperatively, such
as MR or CT images. Non-image based surgical navigation systems
that find axes or anatomical structures, for example with use of
joint motion, can also be used. The position and orientation of the
surgical instrument as well as the mold including alignment guides,
surgical instrument guides, reaming guides, drill guides, saw
guides, etc. can be determined from markers attached to these
devices. These markers can be located by a detector using, for
example, optical, acoustical or electromagnetic signals.
[0419] Identification and preparation of the implant site and
insertion of the implant can also be supported with use of a C-arm
system. The C-arm system can afford imaging of the joint in one or,
preferably, multiple planes. The multiplanar imaging capability can
aid in defining the shape of an articular surface. This information
can be used to selected an implant with a good fit to the articular
surface. Currently available C-arm systems also afford
cross-sectional imaging capability, for example for identification
and preparation of the implant site and insertion of the implant.
C-arm imaging can be combined with administration of radiographic
contrast.
[0420] In various embodiments, the surgical devices described
herein can include one or more materials that harden to form a mold
of the articular surface. In preferred embodiments, the materials
used are biocompatible, such as, without limitation, acylonitrile
butadiene styrene, polyphenylsulfone and polycarbonate. As used
herein "biocompatible" shall mean any material that is not toxic to
the body (e.g., produces a negative reaction under ISO 10993
standards, incorporated herein by reference). In various
embodiments, these biocompatible materials may be compatible with
rapid prototyping techniques.
[0421] In further embodiments, the mold material is capable of heat
sterilization without deformation. An exemplary mold material is
polyphenylsulfone, which does not deform up to a temperature of
207.degree. C. Alternatively, the mold may be capable of
sterilization using gases, e.g. ethyleneoxide. The mold may be
capable of sterilization using radiation, e.g. .gamma.-radiation.
The mold may be capable of sterilization using hydrogen peroxide or
other chemical means. The mold may be capable of sterilization
using any one or more methods of sterilization known in the art or
developed in the future.
[0422] A wide-variety of materials capable of hardening in situ
include polymers that can be triggered to undergo a phase change,
for example polymers that are liquid or semi-liquid and harden to
solids or gels upon exposure to air, application of ultraviolet
light, visible light, exposure to blood, water or other ionic
changes. Any biocompatible material that is sufficiently flowable
to permit it to be delivered to the joint and there undergo
complete cure in situ under physiologically acceptable conditions
can be used. The material can also be biodegradable.
[0423] The curable materials can be used in conjunction with a
surgical tool as described herein. For example, the surgical tool
can be a template that includes one or more apertures therein
adapted to receive injections and the curable materials can be
injected through the apertures. Prior to solidifying in situ the
materials will conform to the articular surface (subchondral bone
and/or articular cartilage) facing the surgical tool and,
accordingly, will form a negative impression of the surface upon
hardening, thereby recreating a normal or near normal articular
surface.
[0424] In addition, curable materials or surgical tools can also be
used in conjunction with any of the imaging tests and analysis
described herein, for example by molding these materials or
surgical tools based on an image of a joint. For example, rapid
prototyping may be used to perform automated construction of the
template. The rapid prototyping may include the use of, without
limitation, 3D printers, stereolithography machines or selective
laser sintering systems. Rapid prototyping is a typically based on
computer-aided manufacturing (CAM). Although rapid prototyping
traditionally has been used to produce prototypes, they are now
increasingly being employed to produce tools or even to manufacture
production quality parts. In an exemplary rapid prototyping method,
a machine reads in data from a CAD drawing, and lays down
successive millimeter-thick layers of plastic or other engineering
material, and in this way the template can be built from a long
series of cross sections. These layers are glued together or fused
(often using a laser) to create the cross section described in the
CAD drawing.
[0425] FIG. 13 is a flow chart illustrating the steps involved in
designing a mold for use in preparing a joint surface. Optionally,
the first step can be to measure the size of the area of the
diseased cartilage or cartilage loss 2100, Once the size of the
cartilage loss has been measured, the user can measure the
thickness of the adjacent cartilage 2120, prior to measuring the
curvature of the articular surface and/or the subchondral bone
2130. Alternatively, the user can skip the step of measuring the
thickness of the adjacent cartilage 2102. Once an understanding and
determination of the shape of the subchondral bone is determined,
either a mold can be selected from a library of molds 3132 or a
patient specific mold can be generated 2134. In either event, the
implantation site is then prepared 2140 and implantation is
performed 2142. Any of these steps can be repeated by the optional
repeat steps 2101, 2121, 2131, 2133, 2135, 2141.
[0426] A variety of techniques can be used to derive the shape of
the template, as described above. For example, a few selected CT
slices through the hip joint, along with a full spiral CT through
the knee joint and a few selected slices through the ankle joint
can be used to help define the axes if surgery is contemplated of
the knee joint. Once the axes are defined, the shape of the
subchondral bone can be derived, followed by applying standardized
cartilage loss.
[0427] Methodologies for stabilizing the 3D guidance templates will
now be described. The 3D guide template may be stabilized using
multiple surgical tools such as, without limitation: K-wires, a
drill bit anchored into the bone and left within the template to
stabilize it against the bone; one or more convexities or cavities
on the surface facing the cartilage; bone stabilization against
intra/extra articular surfaces, optionally with extenders, for
example, from an articular surface onto an extra-articular surface;
and/or stabilization against newly placed cuts or other surgical
interventions.
[0428] Specific anatomic landmarks (including landmarks from one or
more surfaces of a "failed implant") may be selected in the design
and make of the 3D guide template in order to further optimize the
anatomic stabilization. For example, a 3D guidance template may be
designed to cover portions or all off an osteophyte or bone spur in
order to enhance anchoring of the 3D guide template against the
underlying articular anatomy. The 3D guidance template may be
designed to the shape of a trochlear or intercondylar notch and can
encompass multiple anatomic areas such as a trochlea, a medial and
a lateral femoral condyle at the same time. In the tibia, a 3D
guide template may be designed to encompass a medial and lateral
tibial plateau at the same time and it can optionally include the
tibial spine for optimized stabilization and cross-referencing. In
a hip, the fovea capitis may be utilized in order to stabilize a 3D
guide template. Optionally, the surgeon may elect to resect the
ligamentum capitis femoris in order to improve the stabilization.
Also in the hip, an acetabular mold can be designed to extend into
the region of the tri-radiate cartilage, the medial, lateral,
superior, inferior, anterior and posterior acetabular wall or ring.
By having these extensions and additional features for
stabilization, a more reproducible position of the 3D template can
be achieved with resulted improvement in accuracy of the surgical
procedure. Typically, a template with more than one convexity or
concavity or multiple convexities or concavities will provide
better cross-referencing in the anatomic surface and higher
accuracy and higher stabilization than compared to a mold that has
only few surface features such as a singular convexity. Thus, in
order to improve the implementation and intraoperative accuracy,
careful surgical planning and preoperative planning is desired,
that encompasses preferably more than one convexity, more preferred
more than two convexities and even more preferred more than three
convexities, or that encompasses more than one concavity, more
preferred more than two concavities or even more preferred more
than three concavities on an articular surface or adjoined surface,
including bone and cartilage outside the weight-bearing
surface.
[0429] In an even more preferred embodiment, more than one
convexity and concavity, more preferred more than two convexities
and concavities and even more preferred more then three convexities
and concavities are included in the surface of the mold in order to
optimize the interoperative cross-referencing and in order to
stabilize the mold prior to any surgical intervention.
[0430] Turning now to particular 3D surgical template
configurations and to templates for specific joint applications
which are intended to teach the concept of the design as it would
then apply to other joints in the body:
i. 3D Guidance Template Configurations/Positioning
[0431] The 3D guidance template may include a surface that
duplicates the inner surface of an implant, an implant component, a
"failed implant" surface, a "revision implant" surface and/or that
conforms to an articular surface, at least partially, in accordance
with an embodiment of the invention. More than one of the surfaces
of the template may match or conform to one or more of the surfaces
or portions of one or more of these surfaces of an implant, implant
component, and/or articular surface.
[0432] FIG. 20 shows an example of a 3D guidance template 3000 in a
hip joint, in accordance with one embodiment, wherein the template
has extenders 3010 extending beyond the margin of the joint to
provide for additional stability and to fix the template in place.
The surface of the template facing the joint 3020 includes a
portion that substantially conforms to a portion of the joint that
is not affected by the arthritic process 3030. By designing the
template to have a surface portion that substantially conforms to
at least a portion of the joint that is not affected by the
arthritic process, greater reproducibility in placing the template
can be achieved. In this design, the template spares the arthritic
portions 3040 of the joint and does not include them in its joint
facing surface. The template can optionally have metal sleeves 3050
to accommodate a reamer or other surgical instruments, to protect a
plastic. The metal sleeves or, optionally, the template can also
include stops 3060 to limit the advancement of a surgical
instrument once a predefined depth has been reached.
[0433] FIG. 21 shows another embodiment of a 3D guidance template
3100 for an acetabulum, in accordance with an embodiment of the
invention. The articular surface is roughened 3110 in some sections
by the arthritic process. At least a portion of the template 3120
is made to be a portion that substantially conforms to of the
articular surface altered by the arthritic process 3110. By
matching the template to the joint in areas where it is altered by
the arthritic process improved intraoperative localization and
improved fixation can be achieved. In other section, the template
can be matched to portions of the joint that are not altered by the
arthritic process 3130.
[0434] FIG. 22 shows another embodiment of a 3D guidance template
3200 designed to guide a posterior cut 3210 using a posterior
reference plane 3220. The joint facing surface of the template 3230
includes a portion that substantially conforms to one or more
portions of the joint that are not altered by the arthritic
process. The arthritic process includes an osteophyte 3240. The
template includes a recess 3250 that helps avoid the osteophyte
3240. The template is at least in part substantially matched to
portions of the joint that are not involved by the arthritic
process.
[0435] FIG. 23 shows another embodiment of a 3D guidance template
3300 designed to guide an anterior cut 3310 using an anterior
reference plane 3320. The joint facing surface of the template 3230
includes a portion that substantially conforms to one or more
portions of the joint that are altered by the arthritic process.
The arthritic process includes an osteophyte 3240. The joint facing
surface of the template 3230 includes a portion that substantially
conforms to the arthritic process, at least in part, including the
osteophyte 3240. The template is at least in part substantially
matched to portions of the joint that are involved by the arthritic
process.
[0436] FIG. 24 shows another embodiment of a 3D guidance template
3400 for guiding a tibial cut (not shown), wherein the tibia 3410
includes an arthritic portion 3420, in this example a subchondral
cyst 3430. The template is designed to avoid the arthritic process
by spanning across 3440 the defect or cyst.
[0437] FIG. 25 shows another embodiment of a 3D guidance template
3500 for guiding a tibial cut (not shown), wherein the tibia 3510
includes an arthritic portion 3520, in this example a subchondral
cyst 3530. The template is designed to include the arthritic
process 3520 by extending into 3540 the defect or cyst 3530. The
surface of the template facing the joint 3550 includes a portion
that substantially conforms to one or more portions of normal joint
3560 and portions of the joint that are altered by the arthritic
process 3530. The interface between normal and arthritic tissue is
included in the shape of the template 3520.
[0438] FIGS. 26A-D show a knee joint with a femoral condyle 3600
including a normal 3610 and arthritic 3620 region, in accordance
with various embodiments of the invention. The interface 3630
between normal 3610 and arthritic 3620 tissue is shown. The
template is designed to guide a posterior cut 3640 using a guide
plane 3650 or guide aperture 3660.
[0439] In one embodiment shown in FIG. 26A the surface of the
template facing the joint 3670 includes a portion that
substantially conforms to at least portions of the surface of the
joint that is healthy or substantially unaffected by the arthritic
process. A recessed area 3670 can be present to avoid contact with
the diseased joint region. This design can be favorable when an
imaging test is used that does not provide sufficient detail about
the diseased region of the joint to accurately generate a template,
or where information about the anatomical margins of the underlying
anatomical support structure are of insufficient "confidence" as
desired by the user/operator.
[0440] In a similar embodiment shown in FIG. 26B the surface of the
template facing the joint 3670 includes a portion that
substantially conforms to at least portions of the surface of the
joint that is healthy or substantially unaffected by the arthritic
process. The diseased area 3620 is covered by the template, but the
template is not substantially in contact with it.
[0441] In another embodiment shown in FIG. 26C the surface of the
template facing the joint 3670 includes a portion that
substantially conforms to at least portions of the surface of the
joint that are arthritic. The diseased area 3620 is covered by the
template, and the template is in close contact with it. This design
can be advantageous to obtain greater accuracy in positioning the
template if the arthritic area is well defined on the imaging test,
e.g. with high resolution spiral CT or near isotropic MRI
acquisitions or MRI with image fusion. This design can also provide
enhanced stability during surgical interventions by more firmly
fixing the template against the irregular underlying surface.
[0442] In another embodiment shown in FIG. 26D the surface of the
template facing the joint 3670 includes a portion that
substantially conforms to at least portions of the surface of the
joint that are arthritic. The diseased area 3620 is covered by the
template, and the template is in close contact with it. Moreover,
healthy or substantially normal regions 3610 are covered by the
template and the template is in close contact with them. The
template is also closely mirroring the shape of the interface
between substantially normal or near normal and diseased joint
tissue 3630. This design can be advantageous to obtain even greater
accuracy in positioning the template due to the change in surface
profile or contour at the interface and resultant improved
placement of the template on the joint surface. This design can
also provide enhanced stability during surgical interventions by
more firmly fixing and anchoring the template against the
underlying surface and the interface 3630.
[0443] The template may include guide apertures or reference points
for two or more planes, or at least one of a cut plane and one of a
drill hole or reaming opening for a peg or implant stem, in
accordance with an embodiment of the invention.
[0444] The distance between two opposing, articulating implant
components may be optimized intraoperatively for different pose
angles of the joint or joint positions, such as different degrees
of section, extension, abduction, adduction, internal and external
rotation. For example, spacers, typically at least partially
conforming to the template, may be placed between the template of
the opposite surface, where the opposite surface can be the native,
uncut joint, the cut joint, the surgically prepared joint, the
trial implant, the failed implant, the revision implant and/or any
other implant component for that articular surface. Alternatively,
spacers may be placed between the template and the articular
surface for which it will enable subsequent surgical interventions.
For example, by placing spacers between a tibial template and the
tibia, the tibial cut height can be optimized. The thicker the
spacer, or the more spacers interposed between the tibial template
and the tibial plateau, the less deep the cut will be, i.e. the
less bone will be removed from the top of the tibia.
[0445] The spacers may be non-conforming to the template, e.g. they
may be of a flat nature. The spacers may be convex or concave or
include multiple convexities or concavities. The spacers may be
partially conforming to the template. For example, in one
embodiment, the surface of the spacer optionally facing the
articular surface can be molded and individualized to the articular
surface, thereby forming a template/mold, while the opposite
surface of the spacer can be flat or curved or have any other
non-patient specific design. The opposite surface may allow for
placement of blocks or other surgical instruments or for linkages
to other surgical instruments and measurement devices.
[0446] In another embodiment, the template may include multiple
slots spaced at equal distance or at variable distances wherein
these slots allow to perform cuts at multiple cut heights or cut
depths that can be decided on intraoperatively. In another
embodiment, the template may include a ratchet-like mechanism
wherein the ratchet can be placed between the articular surface and
the template or between the template and the opposite surface
wherein the opposite surface may include the native, uncut opposite
surface, the cut opposite surface, an opposite surface template, a
trial implant or the implant component designed for the opposite
surface. By using a ratchet-like device, soft tissue tension can be
optimized, for example, for different pose angles of the joint or
joint positions such as flexion, extension, abduction, adduction,
internal rotation and external rotation at one or more degrees for
each direction.
[0447] Optimizing soft tissue tension will improve joint function
that advantageously enhances postoperative performance. Soft tissue
tension may, for example, be optimized with regard to ligament
tension or muscle tension but also capsular tension. In the knee
joint, soft tissue tension optimization includes typically ligament
balancing, e.g. the cruciate ligaments and/or the collateral
ligaments, for different degrees of knee flexion and knee
extension.
[0448] In a preferred embodiment, a 3D guidance template may attach
to two or more points on the joint and/or implant component. In an
even more preferred embodiment, a template may attach to three or
more points, even more preferred four or more points, even more
preferred five or more points, even more preferred six or more
points, even more preferred seven or more points, even more
preferred ten or more points, even more preferred portions for the
entire surface to be replaced.
[0449] In another embodiment, the template may include one or more
linkages for surgical instruments. The linkages may also be
utilized for attaching other measurement devices such as alignment
guides, intramedullary guides, laser pointing devices, laser
measurement devices, optical measurement devices, radio frequency
measurement devices, surgical navigation and the like. Someone
skilled in the art will recognize many surgical instruments and
measurement in alignment devices may be attached to the template.
Alternatively, these surgical instruments or alignment devices may
be included within the template.
[0450] In another embodiment, a link or a linkage may be attached
or may be incorporated or may be part of a template that rests on a
first articular or implant surface. Said link or linkage may
further extend to a second articular or implant surface which is
typically an opposing articular surface. Said link or linkage can
thus help cross-reference the first surface with the second
surface, ultimately assisting the performance of surgical
interventions on the second surface using the cross reference to
the first surface. The second surface may optionally be cut with a
second template. Alternatively, the second surface may be cut using
a standard surgical instrument, non-individualized, that is cross
referenced via the link to the surgical mold placed on the first
surface. The link or linkage may include adjustment means, such as
ratchets, telescoping devices and the like to optimize the spatial
relationship between the first surface and the second, opposing
articular surface. This optimization may be performed for different
degrees of joint flexion, extension, abduction, adduction and
rotation.
[0451] In another embodiment, the linkage may be made to the cut
articular surface or, more general, an articular surface that has
been altered using a template and related surgical intervention.
Thus, cross reference can be made from the first articular surface
from a mold attached to said first articular surface, the mold
attached to a surgically altered, for example, cut articular
surface, the surgical instrument attached to said articular surface
altered using the mold, e.g. cut or drilled, and the like. Someone
skilled in the art will easily recognize multiple different
variations of this approach. Irrespective of the various
variations, in a first step the articular surface is surgically
altered, for example, via cutting, drilling or reaming using a mold
while in the second step cross reference is established with a
second articular surface.
[0452] By establishing cross reference between said first and said
second articular surface either via the template and/or prior to or
after a surgical intervention, the surgical intervention performed
on the second articular surface can be performed using greater
accuracy and improved usability in relation to said articulating,
opposing first articular surface.
[0453] FIGS. 27A-D show multiple templates with linkages on the
same articular surface (A-C) and to an opposing articular surface
(D), in accordance with various embodiments of the invention. The
mechanical axis is denoted as 3700. A horizontal femoral cut 3701,
an anterior femoral cut 3702, a posterior femoral cut 3703, an
anterior chamfer cut 3704 and a posterior chamfer cut 3705 are
planned in this example. A first template 3705 is applied in order
to determine the horizontal cut plane and to perform the cut. The
cut is perpendicular to the mechanical axis 3700. The first
template 3705 has linkages or extenders 3710 for connecting a
second template 3715 for the anterior cut 3702 and for connecting a
third template 3720 for the posterior cut 3703. The linkages 3710
connecting the first template 3705 with the second 3715 and third
template 3720 help in achieving a reproducible position of the
templates relative to each other. At least one of the templates,
preferably the first template 3705, will have a surface 3706 that
includes a portion that substantially conforms to at least a
portion of the articular surface 3708. In this example, all three
templates have surfaces facing the joint that includes one or more
portions that substantially conform to one or more portions of the
joint, although one template having a surface conforming to the
joint suffices in many applications as described herein.
[0454] A fourth template 3725 may optionally be used in order to
perform an anterior chamfer cut 3704. The fourth template may have
a guide aperture or reference plane 3730 that can determine the
anterior chamfer cut 3704. The fourth template can, but must not
have at least one surface 3735 matching one or more cut articular
surfaces 3740. The fourth template may have one or more outriggers
or extenders 3745 stabilizing the template against the cut or uncut
articular surface.
[0455] A fifth template 3750 may optionally be used to perform a
anterior chamfer cut 3705. The fifth template may have a guide
aperture or reference plane 3755 that can determine the posterior
chamfer cut 3705. The fifth template may have at least one surface
3735 matching one or more cut articular surfaces 3740. Oblique
planes 3760 may help to further stabilize the template during the
procedure. The fifth template may have one or more outriggers or
extenders 3745 stabilizing the template against the cut or uncut
articular surface.
[0456] In another embodiment, an opposite articular side 3765 may
be cut in reference to a first articular side 3766. Any order or
sequence of cutting is possible: femur first then tibia, tibia
first then femur, patella first, and so forth. A template 3770 may
be shaped to the uncut or, in this example, cut first articular
side. The template may have stabilizers against the first articular
surface, for example with extenders 3772 into a previously created
peg hole 3773 for an implant. The template may have a linkage or an
extender 3775 to a second articular surface 3765. Surgical
instruments may be attached to the linkage or extender 3775. In
this example, a tibial cut guide 3778 with multiple apertures or
reference planes 3779 for a horizontal tibial cut is attached. The
tibial cut guide may but may not have a surface matching the tibial
surface.
[0457] By referencing a first, e.g. femoral, to a second, e.g.
tibial cut greater accuracy can be achieved in the alignment of
these cuts, which will result in improved implant component
alignment and less wear. Ratchet like devices 3785 or hinge like
devices or spacers may be inserted into the space between the first
and the second articular surface and soft-tissue tension and
ligament balancing can be evaluated for different distances
achieved between the first 3766 and second 3765 articular surface,
with one or more of them being cut or uncut. In this manner,
soft-tissue tension and ligament balancing can be tested during
different pose angles, e.g. degrees of flexion or extension.
Optionally, tensiometers can be used. Once an ideal soft-tissue
tension and/or ligament balancing has been achieved, the tibial cut
may be performed through one of the guide apertures 3779 in
reference to the femoral cut.
[0458] FIG. 28 is an example demonstrating a deviation in the AP
plane of the femoral 3801 and tibial 3803 axes in a patient. Axis
deviations can be determined in any desired plane including the AP
plane, not only the ML plane. The axis deviation can be measured.
The desired correction can be determined and the position,
orientation and shape of a 3D guidance template can be adjusted in
order to achieve the necessary correction. The correction may, for
example, be designed to achieve a result wherein the femoral 3801
and tibial 3803 axes will coincide with the mechanical axis
3805.
[0459] This disclosure optionally provides for trial implants and
trial devices that help test intraoperatively the result of the
surgical intervention achieved using the 3D guidance mold. Trial
implants or devices can be particularly useful for subsequent
adjustments and fine-tuning of the surgical intervention, for
example, optimizing soft tissue tension in different articular pose
angles.
[0460] In another embodiment, the templates may also allow for
intraoperative adjustments. For example, the template may include
an opening for a pin. The pin can be placed in the bone and the
template can be rotated around the pin thereby optimizing, for
example, medial and lateral ligament tension in a knee joint or
thereby optimizing the cut orientation and resultant rotation and
alignment of an implant relative to the anatomic or mechanical
axis.
[0461] In another embodiment, standard tools including alignment
guides may be attached to the mold, via linkages, for example, and
the attachment can allow for additional adjustments in mold and
subsequently implant alignment and rotation.
[0462] The above-described embodiments can be particularly useful
for optimization of soft tissue tension including ligament
balancing, for example, in a knee joint. Optimization of soft
tissue tension can advantageously improve post-operative function
and range of motion.
[0463] Linkages may also be utilized to stabilize and fix
additional molds or surgical instruments on the articular
surface.
[0464] Moreover, linkages can allow separation of one large mold
into multiple smaller molds. The use of multiple smaller, linked
molds advantageously enable smaller surgical axis with the
potential to enhance muscle sparing and to reduce the size of the
skin cut.
[0465] In another embodiment, all or portions of the template may
be made of metal, metal-alloys, teflon, ceramics. In a more
preferred embodiment, metal, metal-alloys, teflon, ceramics and
other hard materials, typically materials that offer a hardness of,
without limitation, greater than shore 60D, is placed in areas
where the surgical instruments will be in contact with the
template.
iii. Impingement Syndromes, Removal of Exophytic Bone Growth
Including Osteophytes
[0466] 3D guidance templates may also be utilized to treat
impingement syndromes, for example, by template guided removal of
osteophytes or exophytic bone growth. In one embodiment, an imaging
test such as a CT scan or an MRI scan is obtained through the area
of concern. If a joint is imaged, the images can demonstrate an
osteophyte or, more generally, exophytic bone growth in intra and
extra-articular locations. The scan data may then be utilized to
design a template that matches the surface adjacent to the
exophytic bone growth or osteophyte, the surface overlying the
exophytic bone growth or osteophyte or both or portions of one or
both. The template may have openings or apertures or linkages that
allow placement of surgical tools for removal of the exophytic bone
growth or the osteophyte, such as reamers, drills, rotating blades
and the like. Someone skilled in the art will recognize many
different surgical instruments that can be utilized in this
manner.
[0467] Two representative examples where a 3D guidance template can
be applied to treat local impingement syndromes are the pincer and
Cam impingement syndromes in the hip joint. Pincer and Cam
impingement represent femoro-acetabular impingement syndromes
caused by an abutment between the proximal femur and the acetabular
rim during the end range of motion. Untreated femoral-acetabular
impingement can cause osteoarthritis of the hip.
[0468] In Cam impingement, a non-spherical portion of the femoral
head, typically located near the head-neck junction, is jammed into
the acetabulum during hip joint motion. The Cam impingement can
lead to considerable shear forces and subsequently chondral
erosion.
[0469] In one embodiment, an imaging test, such as a CT scan or MRI
scan may be performed pre-operatively. The imaging test may be used
to identify the non-spherical portion of the femoral head at the
head-neck junction that is responsible for the impingement. A 3D
guidance template may be designed that can be applied
intraoperatively to this region. The template is designed to
fulfill three principle functions:
[0470] 1. Intraoperative highly accurate identification of the
non-spherical portion of the femoral head by placement of the
individualized portion of the 3D template onto the area or
immediately adjacent to the area.
[0471] 2. Guidance of surgical instrumentation to remove the
non-spherical portion and to re-establish a spherical or
essentially spherical shape.
[0472] 3. Control of the depth of the bone removal and the shape of
the bone removal. For this purpose, a stop may be incorporated into
the design of the 3D guidance template. Of note, the stop may be
asymmetrical and can even be designed to have a shape that is
substantially a negative of the desired articular contour.
[0473] FIG. 31 shows an example of treatment of CAM impingement
using a 3D guidance template 4100. The impinging area 4105 may be
removed with a saw (not shown) inserted into the guide aperture
4110. The guide aperture may be designed and placed so that only
the impinging portion of the joint is removed.
[0474] In Pincer impingement, linear bony contact occurs between
the normal femoral head-neck junction and enlarged or hypertrophied
portion of the acetabulum. Pre-operatively an imaging test may be
performed in order to identify the abnormal, over covered or
enlarged area of the acetabulum. The amount of bone removal may be
determined on the imaging study, e.g. a CT scan or MRI scan. A 3D
guidance template may then be designed that will achieve the
identical three functions described above in Cam impingement.
[0475] FIG. 32 shows an example of treatment of Pincer impingement
using a 3D guidance template 4200. The impinging area 4205 may be
removed with a saw (not shown) inserted into the guide aperture
4210. The guide aperture may be designed and placed so that only
the impinging portion of the joint is removed.
[0476] Accurate and reproducible identification of the abnormal
bony surface causing the impingement is critical in any form of
musculoskeletal impingement syndrome. 3D guidance template systems
are ideally suited to achieve this purpose and to guide the
surgical instrumentation for removal of the source of impingement.
Moreover, since the localization of the impinging area is performed
pre-operatively during the imaging test, and intra-operatively
using the 3D guidance template, this approach allows for minimally
invasive, tissue, specifically muscle sparing approaches.
iv. Surgical Navigation and 3D Guidance Templates
[0477] 3D guidance template technology as described herein may be
combined with surgical navigation techniques. Surgical navigation
techniques may be image guided or non-image guided for this
purpose. Passive or active surgical navigation systems may be
employed. Surgical navigation systems that use optical or
radiofrequency transmission or registration may be used. A
representative example is the Vector Vision navigation system
manufactured by Brain Lab, Germany. This is a passive infrared
navigation system. Once the patient is positioned appropriately in
the operating room, retro-reflective markers can be applied to the
extremity near the area of intended surgery. With image guided
navigation, an imaging study such as a CT scan or MRI scan, can be
transferred into the workstation of the navigation system. For
registration purposes, the surgeon can, for example, utilize a
pointer navigation tool to touch four or more reference points that
are simultaneously co-identified and cross registered on the CT or
MRI scan on the workstation. In the knee joint, reference points
may include the trochlear groove, the most lateral point of the
lateral condyle, the most medial femoral condyle, the tip of the
tibial spines and so forth. Using image guided navigation,
anatomical and mechanical axis of the joint can be determined
reliably.
[0478] Alternatively, non-image guided navigation may be utilized.
In this case, retro-reflective markers or small radio frequency
transmitters are positioned on the extremity. Movement of the
extremity and of the joints is utilized, for example, to identify
the center of rotation. If surgery of the knee joint is
contemplated, the knee joint may be rotated around the femur. The
marker or radiofrequency transmitter motion may be utilized to
identify the center of the rotation, which will coincide with the
center of the femoral head. In this manner, the mechanical axis may
be determined non-invasively.
[0479] The information resulting in imaging guided navigation,
pertaining to either anatomical or mechanical axis can be may be
utilized to optimize the position of any molds, blocks, linkages or
surgical instruments attached to or guided through the 3D guidance
molds.
[0480] In one embodiment, the joint or more specifically the
articular surface, may be scanned intra-operatively, for example,
using ultrasound or optical imaging methods. The optical imaging
methods may include stereographic or stereographic like imaging
approaches, for example, multiple light path stereographic imaging
of the joint and the articular surface or even single light path 3D
optical imaging. Other scan technologies that are applicable are,
for example, C-arm mounted fluoroscopic imaging systems that can
optionally also be utilized to generate cross-sectional images such
as a CT scan. Intraoperative CT scanners are also applicable.
Utilizing the intraoperative scan, a point cloud of the joint or
the articular surface or a 3D reconstruction or a 3D visualization
and other 3D representations may be generated that can be utilized
to generate an individualized template wherein at least a portion
of said template includes a surface that includes a portion that
substantially conforms to the joint (e.g., including non-articular
surface portions) or the articular surface. A rapid prototyping or
a milling or other manufacturing machine can be available in or
near the operating room and the 3D guidance template may be
generated intraoperatively.
[0481] The intraoperative scan in conjunction with the rapid
production of an individualized 3D guidance template matching the
joint or the articular surface, in whole or at least in part, has
the advantage to generate rapidly a tool for rapid intraoperative
localization of anatomical landmarks, including articular
landmarks. A 3D guidance template may then optionally be
cross-registered, for example, using optical markers or
radiofrequency transmitters attached to the template with the
surgical navigation system. By cross-referencing the 3D guidance
template with the surgical navigation system, surgical instruments
can now be reproducibly positioned in relationship to the 3D
guidance template to perform subsequent procedures in alignment
with or in a defined relationship to at least one or more
anatomical axis and/or at least one or more mechanical axis or
planes.
[0482] v. Stereoscopy, Stereoscopic Imaging:
[0483] In addition to cross-sectional or volumetric imaging
technologies including CT, spiral CT, and MRI, stereoscopic imaging
modalities may be utilized. Stereoscopic imaging is any technique
capable of recording three-dimensional information from two
two-dimensional, projectional imaging. Traditional stereoscopic
imaging includes creating a 3D visualization or representation
starting from a pair of 2D images. The projection path of the 2D
images is offset. The offset is, for example, designed to create an
impression of object depth for the eyes of the viewer. The offset
or minor deviation between the two images is similar to the
prospectors that both eyes naturally receive inbinocular vision.
Using two or more images with an offset or minor deviation in
perspective, it is possible to generate a point cloud or 3D surface
or 3D visualization of a joint or an articular surface, which can
then be input into a manufacturing system such as a rapid
prototyping or milling machine. Dual or more light path, as well as
single light path, systems can be employed
vi. Knee Joint
[0484] When a revision procedure for a total knee arthroplasty (or
repair of a less-than-total knee implant device) is contemplated,
the patient can undergo an imaging test, as discussed in more
detail above, that will demonstrate the articular anatomy of the
knee joint as well as the condition and image of the existing
"failed implant," e.g. width of the femoral condyles, the tibial
plateau, artifact images, etc. Additionally, other joints can be
included in the imaging test thereby yielding information on
femoral and tibial axes, deformities such as varus and valgus and
other articular alignment. The imaging test can be an x-ray image,
preferably in standing, load-bearing position, a CT or spiral CT
scan or an MRI scan or combinations thereof. A spiral CT scan may
be advantageous over a standard CT scan due to its improved spatial
resolution in z-direction in addition to x and y resolution. The
articular surface and shape as well as alignment information
generated with the imaging test, along with any additional image
groups and/or image assessment, evaluation, comparison and/or
corrections, can be used to shape the surgical assistance device,
to select the surgical assistance device from a library of
different devices with pre-made shapes and sizes, or can be entered
into the surgical assistance device and can be used to define the
preferred location and orientation of saw guides or drill holes or
guides for reaming devices or other surgical instruments.
Intraoperatively, the surgical assistance device is applied to the
tibial plateau and subsequently the femoral condyle(s) by matching
its surface with the articular surface and/or any remaining failed
implant components, or by attaching it to anatomic reference points
on the bone or cartilage. The surgeon can then introduce a reamer
or saw through the guides and prepare the joint for the
implantation. By cutting the cartilage and bone along anatomically
defined planes, a more reproducible placement of the implant can be
achieved. This can ultimately result in improved postoperative
results by optimizing biomechanical stresses applied to the implant
and surrounding bone for the patient's anatomy and by minimizing
axis mal-alignment of the implant. In addition, the surgical
assistance device can greatly reduce the number of surgical
instruments needed for total or unicompartmental knee arthroplasty.
Thus, the use of one or more surgical assistance devices can help
make joint arthroplasty more accurate, improve postoperative
results, improve long-term implant survival, reduce cost by
reducing the number of surgical instruments used. Moreover, the use
of one or more surgical assistance device can help lower the
technical difficulty of the procedure and can help decrease
operating room ("OR") times.
[0485] Thus, surgical tools described herein can also be designed
and used to control drill alignment, depth and width, for example
when preparing a site to receive an implant. For example, the tools
described herein, which typically conform to the joint surface
and/or surfaces of the "failed implant," can provide for improved
drill alignment and more accurate placement of any implant. An
anatomically correct tool can be constructed by a number of methods
and can be made of any material, preferably a substantially
translucent and/or transparent material such as plastic, Lucite,
silastic, SLA or the like, and typically is a block-like shape
prior to molding.
[0486] FIG. 14A depicts, in cross-section, an example of a mold 600
for use on the tibial surface having an upper surface 620. The mold
600 contains an aperture 625 through which a surgical drill or saw
can fit. The aperture guides the drill or saw to make the proper
hole or cut in the underlying bone 610 as illustrated in FIGS.
11B-D. Dotted lines 632 illustrate where the cut corresponding to
the aperture will be made in bone.
[0487] FIG. 14B depicts, a mold 608 suitable for use on the femur.
As can be appreciated from this perspective, additional apertures
are provided to enable additional cuts to the bone surface. The
apertures 605 enable cuts 606 to the surface of the femur. The
resulting shape of the femur corresponds to the shape of the
interior surface of the femoral implant, typically as shown in FIG.
11E. Additional shapes can be achieved, if desired, by changing the
size, orientation and placement of the apertures. Such changes
would be desired where, for example, the interior shape of the
femoral component of the implant requires a different shape of the
prepared femur surface.
[0488] Turning now to FIG. 15, a variety of illustrations are
provided showing a tibial cutting block and mold system. FIG. 15A
illustrates the tibial cutting block 2300 in conjunction with a
tibia 2302 that has not been resected. In this depiction, the
cutting block 2300 consists of at least two pieces. The first piece
is a patient specific interior piece 2310 or mold that is designed
on its inferior surface 2312 to mate, or substantially mate, with
the existing geography of the patient's tibia 2302. The superior
surface 2314 and side surfaces 2316 of the first piece 2310 are
configured to mate within the interior of an exterior piece 2320.
The reusable exterior piece 2320 fits over the interior piece 2310.
The system can be configured to hold the mold onto the bone.
[0489] The reusable exterior piece has a superior surface 2322 and
an inferior surface 2324 that mates with the first piece 2310. The
reusable exterior piece 2320 includes cutting guides 2328, to
assist the surgeon in performing the tibial surface cut described
above. As shown herein a plurality of cutting guides can be
provided to provide the surgeon a variety of locations to choose
from in making the tibial cut. If necessary, additional spacers can
be provided that fit between the first patient configured, or
molded, piece 2310 and the second reusable exterior piece, or
cutting block, 2320.
[0490] Clearly, the mold may be a single component or multiple
components. In a preferred embodiment, one or more components are
patient specific while other components such as spacers or
connectors to surgical instruments are generic. In one embodiment,
the mold can rest on portions of the joint on the articular surface
or external to the articular surface (as well as on one or more
surfaces or other features of the "failed implant"). Other surgical
tools then may connect to the mold. For example, a standard
surgical cut block as described for standard implants, for example
in the knee the J&J PFC Sigma system, the Zimmer Nexgen system
or the Stryker Duracon system, can be connected or placed on the
mold. In this manner, the patient specific component can be
minimized and can be made compatible with standard surgical
instruments.
[0491] The mold may include receptacles for standard surgical
instruments including alignment tools or guides. For example, a
tibial mold for use in knee surgery may have an extender or a
receptacle or an opening to receive a tibial alignment rod. In this
manner, the position of the mold can be checked against the
standard alignment tools and methods. Moreover, the combined use of
molds and standard alignment tools including also surgical
navigation techniques can help improve the accuracy of or optimize
component placement in joint arthroplasty, such as hip or knee
arthroplasty. For example, the mold can help define the depth of a
horizontal tibial cut for placement of a tibial component. A tibial
alignment guide, for example an extramedullary or intramedullary
alignment guide, used in conjunction with a tibial mold can help
find the optimal anteroposterior angulation, posterior slope,
tibial slant, or varus-valgus angle of the tibial cut. The mold may
be designed to work in conjuction with traditional alignment tools
known in the art.
[0492] The mold may include markers, e.g. optoelectronic or
radiofrequency, for surgical navigation. The mold may have
receptacles to which such markers can be attached, either directly
or via a linking member.
[0493] The molds can be used in combination with a surgical
navigation system. They can be used to register the bones
associated with a joint into the coordinate system of the surgical
navigation system. For example, if a mold for a joint surface
includes tracking markers for surgical navigation, the exact
position and orientation of the bone can be detected by the
surgical navigation system after placement of the mold in its
unique position. This helps to avoid the time-consuming need to
acquire the coordinates of tens to hundreds of points on the joint
surface for registration.
[0494] Referring back to FIG. 15A, the variable nature of the
interior piece facilitates obtaining the most accurate cut despite
the level of disease of the joint because it positions the exterior
piece 2320 such that it can achieve a cut that is perpendicular to
the mechanical axis. Either the interior piece 2310 or the exterior
piece 2320 can be formed out of any of the materials discussed
above in Section II, or any other suitable material. Additionally,
a person of skill in the art will appreciate that this disclosure
is not limited to the two piece configuration described herein. The
reusable exterior piece 2320 and the patient specific interior
piece 2310 can be a single piece that is either patient specific
(where manufacturing costs of materials support such a product) or
is reusable based on a library of substantially defect conforming
shapes developed in response to known or common tibial surface
sizes and defects.
[0495] The interior piece 2310 is typically molded to the tibia
including the subchondral bone and/or the cartilage. The surgeon
will typically remove any residual meniscal tissue prior to
applying the mold. Optionally, the interior surface 2312 of the
mold can include shape information of portions or all of the
menisci.
[0496] Turning now to FIG. 15B-D, a variety of views of the
removable exterior piece 2320. The top surface 2322 of the exterior
piece can be relatively flat. The lower surface 2324 which abuts
the interior piece conforms to the shape of the upper surface of
the interior piece. In this illustration the upper surface of the
interior piece is flat, therefore the lower surface 2324 of the
reusable exterior surface is also flat to provide an optimal mating
surface.
[0497] A guide plate 2326 is provided that extends along the side
of at least a portion of the exterior piece 2320. The guide plate
2326 provides one or more slots or guides 2328 through which a saw
blade can be inserted to achieve the cut desired of the tibial
surface. Additionally, the slot, or guide, can be configured so
that the saw blade cuts at a line perpendicular to the mechanical
axis, or so that it cuts at a line that is perpendicular to the
mechanical axis, but has a 4-7.degree. slope in the sagittal plane
to match the normal slope of the tibia.
[0498] Optionally, a central bore 2330 can be provided that, for
example, enables a drill to ream a hole into the bone for the stem
of the tibial component of the knee implant.
[0499] FIGS. 15E-H illustrate the interior, patient specific, piece
2310 from a variety of perspectives. FIG. 15E shows a side view of
the piece showing the uniform superior surface 2314 and the uniform
side surfaces 2316 along with the irregular inferior surface 2316.
The inferior surface mates with the irregular surface of the tibia
2302. FIG. 15F illustrates a superior view of the interior,
patient, specific piece of the mold 2310. Optionally having an
aperture 2330. FIG. 15G illustrates an inferior view of the
interior patient specific mold piece 2310 further illustrating the
irregular surface which includes convex and concave portions to the
surface, as necessary to achieve optimal mating with the surface of
the tibia. FIG. 15H illustrates cross-sectional views of the
interior patient specific mold piece 2310. As can be seen in the
cross-sections, the surface of the interior surface changes along
its length.
[0500] As is evident from the views shown in FIGS. 15B and D, the
length of the guide plate 2326 can be such that it extends along
all or part of the tibial plateau, e.g. where the guide plate 2326
is asymmetrically positioned as shown in FIG. 15B or symmetrical as
in FIG. 15D. If total knee arthroplasty is contemplated, the length
of the guide plate 2326 typically extends along all of the tibial
plateau. If unicompartmental arthroplasty is contemplated, the
length of the guide plate typically extends along the length of the
compartment that the surgeon will operate on. Similarly, if total
knee arthroplasty is contemplated, the length of the molded,
interior piece 2310 typically extends along all of the tibial
plateau; it can include one or both tibial spines. If
unicompartmental arthroplasty is contemplated, the length of the
molded interior piece typically extends along the length of the
compartment that the surgeon will operate on; it can optionally
include a tibial spine.
[0501] Turning now to FIG. 15I, an alternative embodiment is
depicted of the aperture 2330. In this embodiment, the aperture
features lateral protrusions to accommodate using a reamer or punch
to create an opening in the bone that accepts a stem having
flanges.
[0502] FIGS. 15J and M depict alternative embodiments of this
disclosure designed to control the movement and rotation of the
cutting block 2320 relative to the mold 2310. As shown in FIG. 15J
a series of protrusions, illustrated as pegs 2340, are provided
that extend from the superior surface of the mold. As will be
appreciated by those of skill in the art, one or more pegs or
protrusions can be used without departing from the scope of the
invention. For purposes of illustration, two pegs have been shown
in FIG. 15J. Depending on the control desired, the pegs 2340 are
configured to fit within, for example, a curved slot 2342 that
enables rotational adjustment as illustrated in FIG. 13K or within
a recess 2344 that conforms in shape to the peg 2340 as shown in
FIG. 15L. As will be appreciated by those of skill in the art, the
recess 2344 can be sized to snugly encompass the peg or can be
sized larger than the peg to allow limited lateral and rotational
movement. The recess can be composed of a metal or other hard
insert 544.
[0503] As illustrated in FIG. 15M the surface of the mold 2310 can
be configured such that the upper surface forms a convex dome 2350
that fits within a concave well 2352 provided on the interior
surface of the cutting block 2320. This configuration enables
greater rotational movement about the mechanical axis while
limiting lateral movement or translation.
[0504] Other embodiments and configurations could be used to
achieve these results without departing from the scope of the
invention.
[0505] As will be appreciated by those of skill in the art, more
than two pieces can be used, where appropriate, to comprise the
system. For example, the patient specific interior piece 2310 can
be two pieces that are configured to form a single piece when
placed on the tibia. Additionally, the exterior piece 2320 can be
two components. The first component can have, for example, the
cutting guide apertures 2328. After the resection using the cutting
guide aperture 2328 is made, the exterior piece 2320 can be removed
and a secondary exterior piece 2320' can be used which does not
have the guide plate 2326 with the cutting guide apertures 2328,
but has the aperture 2330 which facilitates boring into the tibial
surface an aperture to receive a stem of the tibial component of
the knee implant. Any of these designs could also feature the
surface configurations shown in FIGS. 15J-M, if desired.
[0506] FIG. 15N illustrates an alternative design of the cutting
block 2320 that provides additional structures 2360 to protect, for
example, the cruciate ligaments, from being cut during the
preparation of the tibial plateau. These additional structures can
be in the form of indented guides 2360, as shown in FIG. 15N or
other suitable structures.
[0507] FIG. 15O illustrates a cross-section of a system having
anchoring pegs 2362 on the surface of the interior piece 2310 that
anchor the interior piece 2310 into the cartilage or meniscal
area.
[0508] FIGS. 15P AND Q illustrate a device 2300 configured to cover
half of a tibial plateau such that it is unicompartmental.
[0509] FIG. 15R illustrates an interior piece 2310 that has
multiple contact surfaces 2312 with the tibia 2302, in accordance
with one embodiment of the invention. As opposed to one large
contact surface, the interior piece 2310 includes a plurality of
smaller contact surfaces 2312. In various embodiments, the multiple
contact surfaces 2312 are not on the sample plane and are at angles
relative to each other to ensure proper positioning on the tibia
2302. Two or three contact surfaces 2312 may be required to ensure
proper positioning. In various embodiments, only the contact
surfaces 2312 of the interior piece may be molded, the molds
attached to the rest of the template using methodologies known in
the art, such as adhesives. The molds may be removably attached to
the template. It is to be understood that multiple contact surfaces
2312 may be utilized in template embodiments that include one or a
plurality of pieces.
[0510] Turning now to FIG. 16, a femoral mold system is depicted
that facilitates preparing the surface of the femur such that the
finally implanted femoral implant will achieve optimal mechanical
and anatomical axis alignment.
[0511] FIG. 16A illustrates the femur 2400 with a first portion
2410 of the mold placed thereon. In this depiction, the top surface
of the mold 2412 is provided with a plurality of apertures. In this
instance the apertures consist of a pair of rectangular apertures
2414, a pair of square apertures 2416, a central bore aperture 2418
and a long rectangular aperture 2420. The side surface 2422 of the
first portion 2410 also has a rectangular aperture 2424. Each of
the apertures is larger than the eventual cuts to be made on the
femur so that, in the event the material the first portion of the
mold is manufactured from a soft material, such as plastic, it will
not be inadvertently cut during the joint surface preparation
process. Additionally, the shapes can be adjusted, e.g.,
rectangular shapes made trapezoidal, to give a greater flexibility
to the cut length along one area, without increasing flexibility in
another area. As will be appreciated by those of skill in the art,
other shapes for the apertures, or orifices, can be changed without
departing from the scope of the invention.
[0512] FIG. 16B illustrates a side view of the first portion 2410
from the perspective of the side surface 2422 illustrating the
aperture 2424. As illustrated, the exterior surface 2411 has a
uniform surface which is flat, or relatively flat configuration
while the interior surface 2413 has an irregular surface that
conforms, or substantially conforms, with the surface of the
femur.
[0513] FIG. 16C illustrates another side view of the first, patient
specific molded, portion 2410, more particularly illustrating the
irregular surface 2413 of the interior. FIG. 26D illustrates the
first portion 2410 from a top view. The center bore aperture 2418
is optionally provided to facilitate positioning the first piece
and to prevent central rotation.
[0514] FIG. 16D illustrates a top view of the first portion 2410.
The bottom of the illustration corresponds to an anterior location
relative to the knee joint. From the top view, each of the
apertures is illustrated as described above. As will be appreciated
by those of skill in the art, the apertures can be shaped
differently without departing from the scope of the invention.
[0515] Turning now to FIG. 16E, the femur 2400 with a first portion
2410 of the cutting block placed on the femur and a second,
exterior, portion 2440 placed over the first portion 2410 is
illustrated. The second, exterior, portion 2440 features a series
of rectangular grooves (2442-2450) that facilitate inserting a saw
blade therethrough to make the cuts necessary to achieve the femur
shape illustrated in FIG. 11E. These grooves can enable the blade
to access at a 90.degree. angle to the surface of the exterior
portion, or, for example, at a 45.degree. angle. Other angles are
also possible without departing from the scope of the
invention.
[0516] As shown by the dashed lines, the grooves (2442-2450) of the
second portion 2440, overlay the apertures of the first layer.
[0517] FIG. 16F illustrates a side view of the second, exterior,
cutting block portion 2440. From the side view a single aperture
2450 is provided to access the femur cut. FIG. 16G is another side
view of the second, exterior, portion 2440 showing the location and
relative angles of the rectangular grooves. As evidenced from this
view, the orientation of the grooves 2442, 2448 and 2450 is
perpendicular to at least one surface of the second, exterior,
portion 2440. The orientation of the grooves 2444, 2446 is at an
angle that is not perpendicular to at least one surface of the
second, exterior portion 2440. These grooves (2444, 2446)
facilitate making the angled chamfer cuts to the femur. FIG. 16H is
a top view of the second, exterior portion 2440. As will be
appreciated by those of skill in the art, the location and
orientation of the grooves will change depending upon the design of
the femoral implant and the shape required of the femur to
communicate with the implant.
[0518] FIG. 16I illustrates a spacer 2401 for use between the first
portion 2410 and the second portion 2440. The spacer 2401 raises
the second portion relative to the first portion, thus raising the
area at which the cut through groove 2424 is made relative to the
surface of the femur. As will be appreciated by those of skill in
the art, more than one spacer can be employed without departing
from the scope of the invention. Spacers can also be used for
making the tibial cuts. Optional grooves or channels 2403 can be
provided to accommodate, for example, pins 2460 shown in FIG.
16J.
[0519] Similar to the designs discussed above with respect to FIG.
15, alternative designs can be used to control the movement and
rotation of the cutting block 2440 relative to the mold 2410. As
shown in FIG. 16J a series of protrusions, illustrated as pegs
2460, are provided that extend from the superior surface of the
mold. These pegs or protrusions can be telescoping to facilitate
the use of molds if necessary. As will be appreciated by those of
skill in the art, one or more pegs or protrusions can be used
without departing from the scope of the invention. For purposes of
illustration, two pegs have been shown in FIG. 16J. Depending on
the control desired, the pegs 2460 are configured to fit within,
for example, a curved slot that enables rotational adjustment
similar to the slots illustrated in FIG. 15K or within a recess
that conforms in shape to the peg, similar to that shown in FIG.
15L and described with respect to the tibial cutting system. As
will be appreciated by those of skill in the art, the recess 2462
can be sized to snugly encompass the peg or can be sized larger
than the peg to allow limited lateral and rotational movement.
[0520] As illustrated in FIG. 16K the surface of the mold 2410 can
be configured such that the upper surface forms a convex dome 2464
that fits within a concave well 2466 provided on the interior
surface of the cutting block 2440. This configuration enables
greater rotational movement about the mechanical axis while
limiting lateral movement or translation.
[0521] In installing an implant, first the tibial surface is cut
using a tibial block, such as those shown in FIG. 21. The patient
specific mold is placed on the femur. The knee is then placed in
extension and spacers 2401, such as those shown in FIG. 16M, or
shims are used, if required, until the joint optimal function is
achieved in both extension and flexion. The spacers, or shims, are
typically of an incremental size, e.g., 5 mm thick to provide
increasing distance as the leg is placed in extension and flexion.
A tensiometer can be used to assist in this determination or can be
incorporated into the mold or spacers in order to provide optimal
results. The design of tensiometers are known in the art and are
not included herein to avoid obscuring the invention. Suitable
designs include, for example, those described in U.S. Pat. No.
5,630,820 to Todd issued May 20, 1997.
[0522] As illustrated in FIG. 16N (sagittal view) and 16O (coronal
view), the interior surface 2413 of the mold 2410 can include small
teeth 2465 or extensions that can help stabilize the mold against
the cartilage 2466 or subchondral bone 2467.
[0523] 3D guidance templates may be used to create more that one
cut on the same and/or on the opposite articular surface or
opposite articular bone, in accordance with an embodiment of the
invention. These cuts may be cross-referenced with other cuts using
one or more guidance template(s).
[0524] In accordance with one embodiment, the 3D guidance
template(s) are utilized to perform more than one cut on the same
articular side such as the femoral side of a knee joint. In another
embodiment, a 3D guidance template may be utilized to cross
reference surgical interventions on an opposing articular surface.
In a knee, for example, the first articular surface can be the
femoral surface. The opposing articular surface can be the tibial
surface or the patella surface. In a hip, the first articular
surface can be the acetabulum. The opposing articular surface or
the opposing bone can be the proximal femur.
[0525] Thus, in a knee, a horizontal femur cut can be
cross-referenced with an anterior or posterior femur cut or
optionally also chamfer, oblique cuts. Similarly, a tibial
horizontal cut can be cross-referenced with any tibial oblique or
vertical cuts on the same articular side or surface.
[0526] In accordance with another embodiment, one or more femur
cuts can be crossed-referenced with one or more tibial cuts. Or, in
a hip, one or more acetabular cuts or surgical interventions can be
cross-referenced with one or more femoral cuts or surgical
interventions such as drilling, reaming or boring. Similarly, in a
knee again, one or more femur cuts can be cross-referenced with one
or more patella cuts. Any combination and order is possible.
[0527] The cross-referencing can occur via attachments or linkages
including spacers or hinge or ratchet like devices from a first
articular, bone, cartilage and/or implant surface, to a second
articular, bone and/or cartilage surface. The resulting positioning
of the cut on the opposing articular, bone or cartilage surface can
be optimized by testing the cut for multiple pose angles or joint
positions such as flexion, extension, internal or external
rotation, abduction or adduction. Thus, for example, in a knee a
distal femur cut can be performed with a mold. Via a linkage or an
attachment, a tibial template may be attached thereto or to the cut
or other surgical intervention, thus a cross-reference can be
related from the femoral cut to a tibial cut or other surgical
intervention. Cross-referencing from a first articular surface to a
second articular surface via, without limitation, attachments or
linkages to a template has the advantage of insuring an optimal
alignment between the implant or other therapeutic device
components of the first articular surface to that on a second
articular surface. Moreover, by cross-referencing surgical
interventions on a first surface to a second articular surface,
improved efficiencies and time savings can be obtained with the
resulted surgical procedure.
[0528] Cross-referencing the first, the second and, optionally a
third or more articular surface, such as in a knee joint, may be
performed with a single linkage or attachment or multiple linkages
or attachments. A single pose angle or position of a joint or
multiple pose angles or positions of a joint may be tested and
optimized during the entire surgical intervention. Moreover, any
resulting surgical interventions on the opposite, second articular
surface, bone or cartilage may be further optimized by optionally
cross-referencing to additional measurement tools such as standard
alignment guides.
[0529] For example, in a knee joint, a 3D template may be utilized
to perform one or more surgical interventions on the femoral side,
such as a femoral cut. This can then be utilized via a linkage, an
attachment or via indirect cross-referencing directly onto the site
of surgical intervention, to guide a surgical intervention such as
a cut of the tibial side. Prior to performing the surgical
intervention on the tibial side, a traditional tibial alignment
guide with cross-reference to the medial and lateral malleolus of
the ankle turn may be used to optimize the position, orientation
and/or depth and extent of the planned surgical intervention such
as the cut. For example, cross-referencing to the femoral cut can
aid in defining the relative superior inferior height of the tibial
cut, while cross-referencing a tibial alignment guide can
optionally be utilized to determine the slant of the cut in the
interior posterior direction.
[0530] An exemplary system and methodology is now described in
which a femoral template is used to make a cut on the femur, which
is then cross-referenced to properly align a tibial template for
making a cut on the tibial plateau. Initially, an electronic
image(s) of the leg is obtained using imaging techniques elaborated
in above-described embodiments. For example, a pre-operative CT
scan of a patient's leg may be obtained to obtain electronic image
data.
[0531] Image processing is then applied to the image data to
derive, without limitation, relevant joint surfaces, axis, and/or
cut planes. Image processing techniques may include, without
limitation, segmentation and propagation of point clouds.
[0532] Relevant biomechanical and/or anatomical axis data may be
obtained by identifying, for example, the central femoral head,
central knee joint and center of the distal tibia. The cutting
planes may then be defined based on at least one of these axis. For
example, the tibial implant bearing surface may be defined as being
perpendicular to the axis defined by the center of the tibial
plateau 2496 and the center of the distal tibia 2497, as
illustrated in FIG. 16P; the tibial implant's medial margin may
project towards the femoral head, as illustrated in FIG. 16Q; and
the anterior to posterior slope of the tibia may be approximated by
the natural anatomical slope (alternatively, excessive tibial slope
may be corrected).
[0533] The tibial and femoral templates and implants may be
designed based, at least in part, on the derived joint surfaces,
axis and/or cut planes. FIGS. 16R and 16S show isometric views of a
femoral template 2470 and a tibial template 2480, respectively, in
accordance with an embodiment of the invention. The femoral
template 2470 has an interior surface that, in various embodiments,
conforms, or substantially conforms, with the anatomic surface
(bone and/or cartilage) of the femur 2475. Furthermore, the
interior surface of the femoral template may extend a desired
amount around the anatomical boney surfaces of the condyle to
further ensure proper fixation. The interior surface of the tibial
cutting block 2480 may conform, or substantially conform to the
surface (bone and/or cartilage) of the tibia 2481.
[0534] In an exemplary use, the femoral template 2470 is placed on
the femoral condyle 2475, for example, when the knee is flexed. The
femoral template 2470 may be fixed to the femoral condyle 2475
using, without limitation, anchoring screws/drill pins inserted
through drill bushing holes 2471 and 2472. The position of holes
2471 and 2472 on the condyle may be the same used to anchor the
final implant to the femur. In various embodiments, the holes 2471
and 2472 may include metal inserts/bushings to prevent degradation
when drilling. Fixing the template 2470 to the femoral condyle 2475
advantageously prevents movement of the template during subsequent
cutting or other surgical interventions thereby ensuring the
accuracy of the resultant surgical cuts.
[0535] To assist in accurately positioning the femoral template
2470, a femoral guide reference tool 2473 may be attached to the
femoral template 2470, as shown in FIG. 16T. The femoral guide
reference tool 2473 may, without limitation, attach to one of holes
2471 and 2472. The femoral guide reference tool 2473 may reference
off the tangential margin of the posterior condyle, and aid, for
example, in correct anterior-posterior positioning of the femoral
template 2470.
[0536] Upon proper fixation of the femoral template 2470 to the
femoral condyle 2475, a cut to the femoral condyle is made using
cut guide surface or element 2474. The cut guide surface or element
2474 may be integral to the femoral template 2470, or may be an
attachment to the femoral template 2470, with the attachment made
of a harder material than the femoral template 2470. For example,
the cut guide surface or element 2474 may be a metal tab that
slides onto the femoral template 2470, which may be made, without
limitation, of a softer, plastic material.
[0537] Upon making the femoral cut and removing the femoral
template 2475, a sample implant template 2476 (not the final
implant) is optionally positioned on the condyle, as shown in FIG.
16U, in accordance with an embodiment of the invention. The sample
implant template 2474 may be attached to the condyle by using
without limitation, anchoring screws/drill pins inserted through
the same holes used to anchor the final implant to the femur.
[0538] The sample implant template 2476 includes an attachment
mechanism 2494 for attaching the tibial template 2480, thereby
cross-referencing the placement of the distal tibial cut with
respect to the femoral cut/implant's placement. The attachment
mechanism 2494 may be, without limitation, a boss, as shown in FIG.
16U, or other attachment mechanism known in the art, such as a
snap-fit mechanism. Note that in alternative embodiments, a sample
implant template 2476 is not required. For example, the tibial
template 2480 may attach directly to the femoral template 2470.
However, in the subject embodiment, the drill bushing features of
the femoral template 2475 will interfere with the knee going into
extension, preventing the tibial cut.
[0539] In illustrative embodiments, the thickness of the sample
implant template 2476 may not only include the thickness of the
final femoral implant, but may include an additional thickness that
corresponds to a preferred joint space between tibial and femoral
implants. For example, the additional thickness may advantageously
provide a desired joint space identified for proper ligament
balancing or for flexion, extension, rotation, abduction,
adduction, anteversion, retroversion and other joint or bone
positions and motion.
[0540] FIG. 16V is an isometric view of the interior surface of the
sample implant template 2476, in accordance with an embodiment of
the invention. In various embodiments, the femoral implant often
rests on subchondral bone, with the cartilage being excised. In
embodiments where the sample implant template 2474 extends beyond
the dimensions of the femoral implant such that portions of the
sample implant template 2476 rests on cartilage, an offset 2477 in
the interior surface of the sample implant template 2476 may be
provided.
[0541] FIG. 16W is an isometric view of the tibial template 2480
attached to the sample implant 2476 when the knee is in extension,
in accordance with an embodiment of the invention. A crosspin 2478
inserted through boss 2494 fixes the tibial template 2480 to the
sample implant template 2474. Of course, other attachment
mechanisms may be used, as described above. In preferred
embodiments, the tibial template 2480 may also be fixed to the
tibia 2481 using, without limitation, anchoring screws/drill pins
inserted through drill bushing hole 2479. In various embodiments,
the holes 2479 include metal inserts (or other hard material) to
prevent degradation when drilling. As with the femoral template
2475, the cut guide surface or element of the tibial template 2480
may be integral to the tibial template 2475, or may be an
attachment to the tibial template 2480, the attachment made of a
harder material than the tibial template 2480. Upon fixing the
position of the tibial template 2480, the cut guide of the tibial
template 2475 assists in guiding the desired cut on the tibia.
[0542] FIG. 16X shows a tibial template 2490 that may be used,
after the tibial cut has been made, to further guide surgical tools
in forming anchoring apertures in the tibia for utilization by the
tibial implant (e.g., the tibial implant may include pegs and/or
keels that are used to anchor the tibial implant into the tibia),
in accordance with an embodiment of the invention. The outer
perimeter of a portion of the tibial template 2490 may mimic the
perimeter of the tibial implant. Guide apertures in the tibial
template 2490 correspond to the tibial implants fixation features.
A portion of the tibial template 2490 conforms to, without
limitation, the anterior surface of the tibia to facilitate
positioning and anchoring of the template 2490.
[0543] FIG. 16Y shows a tibial implant 2425 and femoral implant
2426 inserted onto the tibia and femur, respectively, after the
above-described cuts have been made, in accordance with an
embodiment of the invention.
[0544] Thus, the tibial template 2480 used on the tibia can be
cross-referenced to the femoral template 2476, femoral cut and/or
sample implant 2474. Similarly, in the hip, femoral templates can
be placed in reference to an acetabular mold or vice versa. In
general, when two or more articular surfaces will be repaired or
replaced, a template can be placed on one or more of them and
surgical procedures including cutting, drilling, sawing or rasping
can be performed on the other surface or other surfaces in
reference to said first surface(s).
[0545] In illustrative embodiments, three-dimensional guidance
templates may be utilized to determine an optimized implant
rotation. Examples are provided below with reference to the knee,
however it is to be understood that optimizing implant rotation may
be applied other joints as well.
Femoral Rotation:
[0546] The optimal rotation of a femoral component or femoral
implant for a uni-compartmental, patello femoral replacement or
total knee replacement may be ascertained in a number of different
ways. Implant rotation is typically defined using various anatomic
axes or planes. These anatomic axes may include, without
limitation, the transepicondylar axis; the Whiteside line, i.e. the
trochlea anteroposterior axis, which is typically perpendicular to
at least one of the cuts; and/or the posterior condylar axis.
Another approach for optimizing femoral component rotation is a
so-called balancing gap technique. With the balancing gap
technique, a femoral cut is made parallel to the tibia, i.e. the
tibia is cut first typically. Prior to performing the femoral cut,
the femoral cut plate is optimized so that the medial and lateral
ligament and soft tissue tension are approximately equal.
[0547] By measuring the relevant anatomic axis or planes, the
optimal implant rotation may be determined. The measurement may be
factored into the shape, position or orientation of the 3D guidance
template, in accordance with an embodiment of the invention. Any
resultant surgical interventions including cuts, drilling, or
sawings are then made incorporating this measurement, thereby
achieving an optimal femoral component rotation.
[0548] Moreover in order to achieve an optimal balancing, the
rotation of the template may be changed so that the cuts are
parallel to the tibial cut with substantially equal tension
medially and laterally applied.
Tibial Rotation:
[0549] A 3D guidance template may also be utilized to optimize
tibial component rotation for uni-compartmental or total knee
replacements, in accordance with an embodiment of the invention.
Tibial component rotation may be measured using a number of
different approaches known in the art. In one example of a tibial
component rotation measurement, the anteroposterior axis of the
tibia is determined. For a total knee replacement, the tibial
component can be placed so that the axis of the implant coincides
with the medial one-third of the tibial tuberosity. This approach
works well when the tibia is symmetrical.
[0550] In another embodiment, the symmetrical tibial component is
placed as far as possible posterolateral and externally rotated so
that the posteromedial corner of the tibial plateau is uncovered to
an extent of between three (3) and five (5) millimeters.
[0551] The above examples are only representative of the different
approaches that have been developed in the literature. Clearly,
other various anatomic axis, plane and area measurements may be
performed in order to optimize implant rotation.
[0552] In illustrative embodiments, these measurements may be
factored into the design of a 3D guidance template and the
position, shape or orientation of the 3D guidance template may be
optimized utilizing this information. Thus, any subsequent surgical
intervention such as cutting, sawing and/or drilling will result in
an optimized implant rotation, for example, in the horizontal or in
a near horizontal plane.
[0553] Turning now to FIG. 17, a variety of illustrations are
provided showing a patellar cutting block and mold system. FIGS.
17A-C illustrates the patellar cutting block 2700 in conjunction
with a patella 2702 that has not been resected. In this depiction,
the cutting block 2700 can consist of only one piece or a plurality
of pieces, if desired. The inner surface 2703 is patient specific
and designed to mate, or substantially mate, with the existing
geography of the patient's patella 2702. Small openings are present
2707 to accept the saw. The mold or block can have only one or
multiple openings. The openings can be larger than the saw in order
to allow for some rotation or other fine adjustments. FIG. 17A is a
view in the sagittal plane S. The quadriceps tendon 2704 and
patellar tendon 2705 are shown.
[0554] FIG. 17B is a view in the axial plane A. The cartilage 2706
is shown. The mold can be molded to the cartilage or the
subchondral bone or combinations thereof. FIG. 17C is a frontal
view F of the mold demonstrating the opening for the saw 2707. The
dashed line indicates the relative position of the patella
2702.
[0555] FIG. 17D (sagittal view) and E (axial view) illustrate a
patellar cutting block 2708 in conjunction with a patella 2702 that
has not been resected. In this depiction, the cutting block 2708
consists of at least two pieces. The first piece is a patient
specific interior piece 2710 or mold that is designed on its
inferior surface 2712 to mate, or substantially mate, with the
existing geography of the patient's patella 2702. The posterior
surface 2714 and side surfaces 2716 of the first piece 2710 are
configured to mate within the interior of an exterior piece 2720.
The reusable exterior piece 2720 fits over the interior piece 2710
and holds it onto the patella. The reusable exterior piece has an
interior surface 2724 that mates with the first piece 2710. The
reusable exterior piece 2720 includes cutting guides 2707, to
assist the surgeon in performing the patellar surface cut. A
plurality of cutting guides can be provided to provide the surgeon
a variety of locations to choose from in making the patellar cut.
If necessary, additional spacers can be provided that fit between
the first patient configured, or molded, piece 2710 and the second
reusable exterior piece, or cutting block, 2720.
[0556] The second reusable exterior piece, or cutting block, 2720,
can have grooves 2722 and extensions 2725 designed to mate with
surgical instruments such as a patellar clamp 2726. The patellar
clamp 2726 can have ring shaped graspers 2728 and locking
mechanisms, for example ratchet-like 2730. The opening 2732 in the
grasper fits onto the extension 2725 of the second reusable
exterior piece 2720. Portions of a first portion of the handle of
the grasper can be at an oblique angle 2734 relative to the second
portion of the handle, or curved (not shown), in order to
facilitate insertion. Typically the portion of the grasper that
will be facing towards the intra-articular side will have an
oblique or curved shaped thereby allowing a slightly smaller
incision.
[0557] The variable nature of the interior piece facilitates
obtaining the most accurate cut despite the level of disease of the
joint because it positions the exterior piece 2720 in the desired
plane. Either the interior piece 2710 or the exterior piece 2720
can be formed out of any of the materials discussed above in
Section II, or any other suitable material. Additionally, a person
of skill in the art will appreciate that this disclosure is not
limited to the two piece configuration described herein. The
reusable exterior piece 2720 and the patient specific interior
piece 2710 can be a single piece that is either patient specific
(where manufacturing costs of materials support such a product) or
is reusable based on a library of substantially defect conforming
shapes developed in response to known or common tibial surface
sizes and defects.
[0558] The interior piece 2710 is typically molded to the patella
including the subchondral bone and/or the cartilage.
[0559] From this determination, an understanding of the amount of
space needed to balance the knee is determined and an appropriate
number of spacers is then used in conjunction with the cutting
block and mold to achieve the cutting surfaces and to prevent
removal of too much bone. Where the cutting block has a thickness
of, for example, 10 mm, and each spacer has a thickness of 5 mm, in
preparing the knee for cuts, two of the spacers would be removed
when applying the cutting block to achieve the cutting planes
identified as optimal during flexion and extension. Similar results
can be achieved with ratchet or jack like designs interposed
between the mold and the cut guide.
[0560] vii. Hip Joint
[0561] Turning now to FIG. 18, a variety of views showing sample
mold and cutting block systems for use in the hip joint are shown.
FIG. 18A illustrates femur 2510 with a mold and cutting block
system 2520 placed to provide a cutting plane 2530 across the
femoral neck 2512 to facilitate removal of the head 2514 of the
femur and creation of a surface 2516 for the hip ball
prosthesis.
[0562] FIG. 18B illustrates a top view of the cutting block system
2520. The cutting block system 2520 includes an interior, patient
specific, molded section 2524 and an exterior cutting block surface
2522. The interior, patient specific, molded section 2524 can
include a canal 2526 to facilitate placing the interior section
2524 over the neck of the femur. As will be appreciated by those of
skill in the art, the width of the canal will vary depending upon
the rigidity of the material used to make the interior molded
section. The exterior cutting block surface 2522 is configured to
fit snugly around the interior section. Additional structures can
be provided, similar to those described above with respect to the
knee cutting block system, that control movement of the exterior
cutting block 2524 relative to interior mold section 2522, as will
be appreciated by those of skill in the art. Where the interior
section 2524 encompasses all or part of the femoral neck, the
cutting block system can be configured such that it aids in removal
of the femoral head once the cut has been made by, for example,
providing a handle 2501.
[0563] FIG. 18C illustrates a second cutting block system 2550 that
can be placed over the cut femur to provide a guide for reaming
after the femoral head has been removed using the cutting block
shown in FIG. 18A. FIG. 18D is a top view of the cutting block
shown in FIG. 18C. As will be appreciated by those of skill in the
art, the cutting block shown in FIG. 18C-D, can be one or more
pieces. As shown in FIG. 18E, the aperture 2552 can be configured
such that it enables the reaming for the post of the implant to be
at a 90.degree. angle relative to the surface of femur.
Alternatively, as shown in FIG. 18F, the aperture 2552 can be
configured to provide an angle other than 90.degree. for reaming,
if desired.
[0564] FIG. 19A (sagittal view) and 29B (frontal view, down onto
mold) illustrates a mold system 2955 for the acetabulum 2957. The
mold can have grooves 2959 that stabilize it against the acetabular
rim 2960. Surgical instruments, e.g. reamers, can be passed through
an opening in the mold 2956. The side wall of the opening 2962 can
guide the direction of the reamer or other surgical instruments.
Metal sleeves 2964 can be inserted into the side wall 2962 thereby
protecting the side wall of the mold from damage. The metal sleeves
2964 can have lips 2966 or overhanging edges that secure the sleeve
against the mold and help avoid movement of the sleeve against the
articular surface.
[0565] FIG. 19C is a frontal view of the same mold system shown in
FIGS. 19A and 19B. A groove 2970 has been added at the 6 and 12
o'clock positions. The groove can be used for accurate positioning
or placement of surgical instruments. Moreover, the groove can be
useful for accurate placement of the acetabular component without
rotational error. Someone skilled in the art will recognize that
more than one groove or internal guide can be used in order to not
only reduce rotational error but also error related to tilting of
the implant. As seen FIG. 19D, the implant 2975 can have little
extensions 2977 matching the grooves thereby guiding the implant
placement. The extensions 2977 can be a permanent part of the
implant design or they can be detachable. Note metal rim 2979 and
inner polyethylene cup 2980 of the acetabular component.
[0566] FIG. 19D illustrates a cross-section of a system where the
interior surface 2960 of the molded section 2924 has teeth 2962 or
grooves to facilitate grasping the neck of the femur.
[0567] Various steps may be performed in order to design and make
3D guidance templates for hip implants, in accordance with an
embodiment of the invention.
[0568] For example, in an initial step, a discrepancy in the length
of the left leg and right leg may be determined, for example, in
millimeters. Leg length discrepancy may be determined, for example,
using standing x-rays, typically including the entire leg but also
cross-sectional imaging modalities such as CT or MRI.
[0569] A CT scout scan may be utilized to estimate leg length.
Alternatively, select image slices through the hip and ankle joint
may be utilized to estimate leg length either using CT or MRI.
[0570] Pre-operative planning is then performed using the image
data (including final image data assessed, evaluated,
cross-referenced, derived and/or corrected from image groups as
previously described). A first 3D guidance template is designed to
rest on the femoral neck. FIG. 33 shows an example of an intended
site 4300 for placement of a femoral neck mold for total hip
arthroplasty. (In a similar manner, an existing "failed implant"
component may be utilized as an alignment surface or surfaces,
alone or in combination with anatomical surfaces, for preparation
of the joint to receive a "revision implant.") A cut or saw plane
integrated into this template can be derived. The position, shape
and orientation of the 3D guidance mold or jig or template may be
determined on the basis of anatomical axis such as the femoral neck
axis, the mechanical axis and/or also any underlying leg length
discrepancy (FIG. 29). Specifically, the superoinferior cut or saw
guide height can be adapted to account for leg length discrepancy.
For example, if the left leg is five (5) millimeters shorter than
the right leg, then the cut height can be moved by five (5)
millimeters to account for this difference. The femoral neck cut
height ultimately determines the position of the femoral stem.
Thus, in this manner, using this type of pre-operative planning,
the femoral neck cut height can be optimized using a 3D guidance
template.
[0571] FIG. 29 is a flow diagram of a method wherein measurement of
leg length discrepancy can be utilized to determine the optimal cut
height of the femoral neck cut for total hip arthroplasty.
Initially, imaging is performed, e.g. CT and/or MRI, through,
without limitation, the hip, knee and ankle joint, step 3902. Leg
length discrepancy is determined, using the imaging data obtained,
step 3904. The preferred implant size may then be optionally
determined, step 3906. The preferred femoral neck cut position is
determined based, at least in part, on correcting the leg length
discrepancy for optimal femoral component placement.
[0572] FIG. 34 shows another example of a femoral neck mold 4400
with handle 4410 and optional slot 4420.
Acetabulum:
[0573] In the acetabulum, the position and orientation of the
acetabular component or acetabular cup is also critical for the
success of hip surgery. For example, the lowest portion of the
acetabular cup may be placed so that it is five (5) millimeters
lateral to an anatomic landmark on a pelvic x-ray coinciding with
the inferior border of the radiographic tear drop. If the
acetabular component is, for example, placed too far superiorly,
significant bone may be lost.
[0574] Placing the acetabular component using the 3D guidance
template may include, for example, the following steps:
[0575] Step One: Imaging, e.g. using optical imaging methods, CT or
MRI.
[0576] Step Two: Determining the anterior rotation of the
acetabulum and the desired rotation of the acetabular cup.
[0577] Step Three: Find best fitting cup size.
[0578] Step Four: Determine optimal shape, orientation and/or
position of 3D guidance template.
[0579] The template may be optionally designed to rest primarily on
the margin of the acetabular fossa. In this manner, it is possible
to ream through the template.
[0580] FIG. 35 shows an example of a posterior acetabular approach
for total hip replacement. Tissue retractors 4510 are in place. The
acetabular fossa is visible 4520.
[0581] FIG. 36 shows an example of a guidance mold used for reaming
the site for an acetabular cup. The mold 4600 can be optionally
attached to a generic frame 4610. A guide for the reamer is shown
4620. The reamer 4630 or the mold can have optional stops 4640. In
this example, the stops 4640 are attached to the reamer 4630 and
engage the guide 4620 for the reamer.
[0582] For purposes of reaming, the template may be fixed to the
pelvis, for example, using metal spikes or K-wires. The template
may also have a grip for fixing it to the bone. Thus, a surgeon may
optionally press the template against the bone while a second
surgeon will perform the reaming through the opening in the
template. The grip or any stabilizers can extend laterally, and
optionally serve as tissue retractors, keeping any potentially
interfering soft tissue out of the surgical field. The template may
also include stoppers 4640 to avoid over penetration of the reamer.
These stoppers may be designed in the form of metal stops defining
the deepest penetration area for the peripheral portion or other
portions of the reamer. Optionally, the template may also taper and
decrease in inner radius thereby creating a stop once the reamer
once the reaches the innermost portion of the template. Any stop
known in the art can be used. The imaging test can be used to
design or shape the mold in a manner that will help achieve the
optimal reaming depth. The stops can be placed on the mold or
reamer in reference to the imaging test in order to achieve the
optional reaming depth.
[0583] A 3D guidance template may be utilized to optimize the
anteversion of the acetabular cup. For example, with the
posteriolateral approach, typically an anteversion of forty to
forty-five degrees is desired in both males and females. With an
anterolateral approach, zero degrees anteversion may be desired.
Irrespective of the desired degree of anti-version, the shape,
orientation and/or position of the template may be optimized to
include the desired degree of anteversion.
[0584] Similarly, on the femoral side, the 3D guidance template may
be optimized with regard to its shape, orientation and position in
order to account for neutral, varus or valgus position of the
femoral shaft. A 3D guidance template may also be utilized to
optimize femoral shaft anteversion.
[0585] Thus, after a first template has been utilized for
performing the femoral neck cut and a second template has been
utilized for performing the surgical intervention on the acetabular
side, a third template may optionally be utilized to be placed onto
the femoral cut.
[0586] Optionally, modular hip implant components may be utilized
such as a modular stem. Such modular designs can be helpful in
further optimizing the resultant femoral anteversion by selecting,
for example, different stem shapes.
[0587] In another embodiment, the surgeon may perform a femur first
technique wherein a first cut is applied to the femur using a first
3D guidance mold. Optionally, the broach in the cut femoral shaft
may be left in place. Optionally, a trial implant head may be
applied to the broach. The trial implant head may be variable in
radius and superoinferior diameter and may be utilized to determine
the optimal soft tissue tension. Optionally, the trial head may
also be utilized to determine the acetabular cup position wherein
said acetabular cup position is derived on the basis of the femoral
cut. Thus, the acetabular position can be optionally derived using
the opposite articular surface. In a reverse acetabulum first
technique, the acetabulum can be prepared first and, using soft
tissue balancing techniques, the femoral component can be placed in
reference to the acetabular component. Optionally, the femoral cut
may even be placed intentionally too proximal and is subsequently
optimized by measuring soft tissue tension utilizing various trial
heads with the option to then change the height of the optimal
femoral cut.
Positioning of Template
[0588] In an illustrative embodiment, in order to make a guidance
template reliably and reproducibly, a portion of the joint is
identified in a first step wherein said portion of the joint has
not been altered by the arthritic process. In a second step, the
surface or a point cloud of said portion of the joint is derived,
and may, optionally, be used to derive a virtual 3D model and, in a
third step, to generate a physical model as part of the guidance
template. Using a portion of the joint that has not been altered by
the arthritic process can advantageously improve the
reproducibility and the accuracy of the resultant mold or jig or
template. In a similar manner, the use of existing feature(s) of a
"failed implant" may be useful for alignment of the template as
described herein.
[0589] The step of identifying said portion of the joint may be
visual, semiautomatic or fully automatic. Anatomic models may
assist in the process. Anatomic reference standards may be
utilized.
[0590] As known in the art, various methods for image segmentation
may be used to derive the point cloud or the surface. Suitable
algorithms include, for example, but are not limited to snakes,
live wire, thresholding, active contours, deformable models and the
like. Artificial neural networks may be employed to improve the
accuracy of the molds.
[0591] In another embodiment, the current mechanical axis may
determined or estimated in a first step. In a second step, the
desired mechanical axis is determined. In a third step adjustments,
for example via change in slot position or position for openings
for saws and drills and the like, may be made to alter the cut or
drill position in order to correct the mechanical axis in a fourth
step. In a fifth step, the position of the slot or openings for
saws and drills and the like may be adjusted for ligament balancing
and/or for optimizing flexion and extension gap. This adjustment
may be performed in the 3D model prior to the manufacturing
process. Alternatively, adjustments may be made intraoperatively,
for example via spacers or ratchet like devices or pins to allow
for some degree of rotation.
[0592] In another embodiment, at least a portion of the surface of
the mold or jig or template is derived from a portion of the joint
and/or implant that is affected by the arthritic process.
Optionally, adjustment means can be performed, for example via the
software, to simulate a normal shape. The difference between the
actual shape and the adjusted shape can be utilized to optimize the
position of the slots or openings in the mold or template or
jig.
[0593] In a preferred embodiment, at least a portion of the surface
of the mold or jig or template that is in contact with the joint
may be derived from a portion of the joint that is affected by the
arthritic process and a portion of the joint that has not been
altered by the arthritic process. By spanning both normal and
diseased portions of the joint, the interface between normal and
diseased portions of the joint is included in the surface of the
mold. The interface between normal and diseased portions of the
joint is typically characterized by a sudden change in contour or
shape, e.g. a reduction in cartilage thickness, a change in
subchondral bone contour, a cyst or a bone spur. This change in
joint contour or shape provides additional reference points for
accurately placing the mold or jig or template. In addition, this
change in joint contour or shape provides also additional
stabilization or fixation of the mold or jig or template on the
surface of the joint, in particular while performing surgical
interventions such as cutting, drilling or sawing.
[0594] The design is proposed such that the guide is molded to
precisely fit the anatomy of the articular surface of the patella
for each patient, thus providing precise location of the patella
planing needed. As will be appreciated by those of skill in the
art, while an exact or precise fit is desired, deviations from a
precise fit can occur without departing from the scope of the
invention. Thus, it is anticipated that a certain amount of error
in the design can be tolerated.
B. Small, Focal Cartilage Defect
[0595] After identification of the cartilage defect and marking of
the skin surface using the proprietary U-shaped cartilage defect
locator device as described herein, a 3 cm incision is placed and
the tissue retractors are inserted. The cartilage defect is
visualized.
[0596] A first Lucite block matching the 3D surface of the femoral
condyle is placed over the cartilage defect. The central portion of
the Lucite block contains a drill hole with an inner diameter of,
for example, 1.5 cm, corresponding to the diameter of the base
plate of the implant. A standard surgical drill with a drill guide
for depth control is inserted through the Lucite block, and the
recipient site is prepared for the base component of the implant.
The drill and the Lucite block are then removed.
[0597] A second Lucite block of identical outer dimensions is then
placed over the implant recipient site. The second Lucite block has
a rounded, cylindrical extension matching the size of the first
drill hole (and matching the shape of the base component of the
implant), with a diameter 0.1 mm smaller than the first drill hole
and 0.2 mm smaller than that of the base of the implant. The
cylindrical extension is placed inside the first drill hole.
[0598] The second Lucite block contains a drill hole extending from
the external surface of the block to the cylindrical extension. The
inner diameter of the second drill hole matches the diameter of the
distal portion of the fin-shaped stabilizer strut of the implant,
e.g. 3 mm. A drill, e.g. with 3 mm diameter, with a drill guide for
depth control is inserted into the second hole and the recipient
site is prepared for the stabilizer strut with a four fin and step
design. The drill and the Lucite block are then removed.
[0599] A plastic model/trial implant matching the 3-D shape of the
final implant with a diameter of the base component of 0.2 mm less
than that of the final implant and a cylindrical rather than
tapered strut stabilizer with a diameter of 0.1 mm less than the
distal portion of the final implant is then placed inside the
cartilage defect. The plastic model/trial implant is used to
confirm alignment of the implant surface with the surrounding
cartilage. The surgeon then performs final adjustments.
[0600] The implant is subsequently placed inside the recipient
site. The anterior fin of the implant is marked with red color and
labeled "A." The posterior fin is marked green with a label "P" and
the medial fin is color coded yellow with a label "M." The Lucite
block is then placed over the implant. A plastic hammer is utilized
to advance the implant slowly into the recipient site. A press fit
is achieved with help of the tapered and four fin design of the
strut, as well as the slightly greater diameter (0.1 mm) of the
base component relative to the drill hole. The Lucite block is
removed. The tissue retractors are then removed. Standard surgical
technique is used to close the 3 cm incision. The same procedure
described above for the medial femoral condyle can also be applied
to the lateral femoral condyle, the medial tibial plateau, the
lateral tibial plateau and the patella. Immediate stabilization of
the device can be achieved by combining it with bone cement if
desired.
[0601] IV. Kits
[0602] Also described herein are kits comprising one or more of the
methods, systems and/or compositions described herein. In
particular, a kit can include one or more of the following:
instructions (methods) of obtaining electronic images; systems or
instructions for evaluating electronic images; one or more computer
means capable of analyzing or processing the electronic images;
and/or one or more surgical tools for implanting an articular
repair system. For example, a kit may include an articular repair
system (e.g., one or more implant components) designed, made,
selected, engineered or adapted for a patient, and one or more
single-use surgical tools that facilitate placement of the
articular repair system into the patient.
[0603] The following examples are included to more fully illustrate
the present invention. Additionally, these examples provide
preferred embodiments of this disclosure and are not meant to limit
the scope thereof.
Example 1
Design and Construction of a Three-Dimensional Articular Repair
System
[0604] Areas of cartilage are imaged as described herein to detect
areas of cartilage loss and/or diseased cartilage. The margins and
shape of the cartilage and subchondral bone adjacent to the
diseased areas are determined. The thickness of the cartilage is
determined. The size of the articular repair system is determined
based on the above measurements. In particular, the repair system
is either selected (based on best fit) from a catalogue of
existing, pre-made implants with a range of different sizes and
curvatures or custom-designed using CAD/CAM technology. The library
of existing shapes is typically on the order of about 30 sizes.
[0605] The implant is a chromium cobalt implant. The articular
surface is polished and the external dimensions slightly greater
than the area of diseased cartilage. The shape is adapted to
achieve perfect or near perfect joint congruity utilizing shape
information of surrounding cartilage and underlying subchondral
bone. Other design features of the implant can include: a slanted
(60- to 70-degree angle) interface to adjacent cartilage; a
broad-based base component for depth control; a press fit design of
base component; a porous coating of base component for ingrowth of
bone and rigid stabilization; a dual peg design for large defects
implant stabilization, also porous coated; a single stabilizer
strut with tapered, four fin and step design for small, focal
defects, also porous coated; and a design applicable to femoral
resurfacing (convex external surface) and tibial resurfacing
(concave external surface).
Example 2
Minimally Invasive, Arthroscopically Assisted Surgical
Technique
[0606] The articular repair systems are inserted using arthroscopic
assistance. The device does not require the 15 to 30 cm incision
utilized in unicompartmental and total knee arthroplasties. The
procedure is performed under regional anesthesia, typically
epidural anesthesia. The surgeon can apply a tourniquet on the
upper thigh of the patient to restrict the blood flow to the knee
during the procedure. The leg is prepped and draped in sterile
technique. A stylette is used to create two small 2 mm ports at the
anteromedial and the anterolateral aspect of the joint using
classical arthroscopic technique. The arthroscope is inserted via
the lateral port. The arthroscopic instruments are inserted via the
medial port. The cartilage defect is visualized using the
arthroscope. A cartilage defect locator device is placed inside the
diseased cartilage. The probe has a U-shape, with the first arm
touching the center of the area of diseased cartilage inside the
joint and the second arm of the U remaining outside the joint. The
second arm of the U indicates the position of the cartilage
relative to the skin. The surgeon marks the position of the
cartilage defect on the skin. A 3 cm incision is created over the
defect. Tissue retractors are inserted and the defect is
visualized.
[0607] A translucent Lucite block matching the 3D shape of the
adjacent cartilage and the cartilage defect is placed over the
cartilage defect. For larger defects, the Lucite block includes a
lateral slot for insertion of a saw. The saw is inserted and a
straight cut is made across the articular surface, removing an area
slightly larger than the diseased cartilage. The center of the
Lucite block contains two drill holes with a 7.2 mm diameter. A 7.1
mm drill with drill guide controlling the depth of tissue
penetration is inserted via the drill hole. Holes for the
cylindrical pegs of the implant are created. The drill and the
Lucite block are subsequently removed.
[0608] A plastic model/trial implant of the mini-repair system
matching the outer dimensions of the implant is then inserted. The
trial implant is utilized to confirm anatomic placement of the
actual implant. If indicated, the surgeon can make smaller
adjustments at this point to improve the match, e.g. slight
expansion of the drill holes or adjustment of the cut plane.
[0609] The implant is then inserted with the pegs pointing into the
drill holes. Anterior and posterior positions of the implant are
color-coded; specifically the anterior peg is marked with a red
color and a small letter "A", while the posterior peg has a green
color and a small letter "P". Similarly, the medial aspect of the
implant is color-coded yellow and marked with a small letter "M"
and the lateral aspect of the implant is marked with a small letter
"L". The Lucite block is then placed on the external surface of the
implant and a plastic hammer is used to gently advance the pegs
into the drill holes. The pegs are designed to achieve a press
fit.
[0610] The same technique can be applied in the tibia. The implant
has a concave articular surface matching the 3D shape of the tibial
plateau. Immediate stabilization of the device can be achieved by
combining it with bone cement if desired.
Example 3
"Failed Implant" Assisted Knee Technique
[0611] Example 3 depicts one embodiment of a revision system,
method and devices contemplated by the present invention. In this
embodiment, a total knee implant is experiencing failure or
impending failure for any number of reasons, and requires surgical
removal and revision to a replacement total knee implant. While the
current embodiment contemplates removal and replacement of all
implant components, it should be understood that a partial
component replacement and/or implantation, either of one side
(i.e., all of the tibial components) of an implant, as well as
replacement and/or implantation of individual failed or failing
components of the implant, are contemplated by the present
invention.
[0612] Initially, the "failed implant" will be assessed and
diagnosed. This process typically includes non-invasive imaging of
the implant and the patient's anatomy, usually in an attempt to
determine the condition of the implant and/or joint as well as to
identify any discernable failure mode (i.e., did the implant break,
did cement loosen, or has the underlying anatomical structure
degraded and the implant has loosened). The non-invasive imaging
will desirably create 2 or 3 dimensional images and/or image
databases of the joint and the failed implant components (the
"failed implant" images).
[0613] In addition to the "failed implant" images, it is desirable,
but not absolutely necessary in all embodiments, to obtain
additional image sets from the patient's history (see Table 1 for
various exemplary image types). If desired, the images can be
normalized, assessed, evaluated, cross-referenced and/or corrected,
or any combination thereof, as previous described. It should be
understood that such manipulation of the images may be conducted in
virtually any order, with various steps following other steps
(i.e., images may be cross-referenced and then corrected, or may be
corrected and then cross-referenced, etc.). Similarly, the various
image processing steps may be repeated as necessary or desired,
such as normalizing an image, then cross-referencing and/or
correcting an image, and then normalizing the processed image,
etc.
[0614] Once an acceptable and/or accurate view of the "failed
implant" and the underlying joint anatomy have been ascertained
and/or modeled as described, the resulting implant and joint image
information (the "generated image information") may be used to plan
the revision surgery. This generated information may be utilized to
create a patient-specific revision implant and/or components,
and/or may be used to choose a "best fit" revision implant from a
series of pre-manufactured and/or pre-designed implant components
as described herein.
[0615] The generated Information may also be highly useful in
assessing the failure and/or success potential of the revision
implant, especially where such information reflects joint condition
over the course of the treatment over time. Specifically, the
generated information may identify areas of insufficient support
structure and/or areas of high wear and/or stress that may lead to
premature failure or other undesirable wear of the revision
implant. If desired, this information may be utilized to modify the
implant in some manner (i.e., reinforce areas of higher stress
and/or wear or reduce the size/thickness of areas that experience
lower stresses or wear), or may be utilized to modify the
implantation procedure and/or implant components.
[0616] In a similar manner, the generated information may be
utilized to determine if augments or other accessory structures
(which may or may not be secured to the revision implant and/or the
underlying anatomical support structure) are necessary or needed
for placement of surgical tool s and the revision implant. For
example, the various imaging and processing techniques may reveal
significant osteolysis of the anatomical support structure.
Desirably, this osteolysis will be accounted for during the design
and/or selection of revision components, allowing the determination
of augments (i.e., blocks and/or wedges, etc.) require for proper
implant placement. If desired, additional augments of differing
sizes and/or shapes may also be provided to account for any
inaccuracies or unanticipated "real world" conditions experienced
(i.e., significantly less bone support than anticipated, extremely
poor bone quality precluding use as support structure, localized
bone disease or infection, fracture or "bonding" of support
structures to the failed implant during removal, etc.) when the
"failed implant" is removed and the actual anatomical support
structure is revealed. Similar augments may be provided for use
with the various surgical tools and molds of the present invention,
assisting tint the proper alignment and placement of bone cuts,
burring, reaming, drilling, etc.
[0617] Once a desired revision implant has been chosen or designed,
the various generated information may be utilized to create
surgical tools and/or molds for assisting with the preparation of
the revision implant site. Desirably, these tools will incorporate
readily accessible anatomical and/or "failed implant" landmarks to
assist with the alignment and placement of the subsequent revision
implant. In at least one embodiment, the tool includes at least one
surface that matches or substantially conforms to an anatomical
surface (i.e., a cortical bone surface, a subchondral bone surface,
a cartilage surface, an osteophyte, a bone void, a bone defect,
etc.) and at least a second surface matching or substantially
conforming to (and/or resting against and/or abutting in some
manner) one or more surfaces of the implant or implant components
requiring revision (which may be a component to be revised, or a
component that is not revised but which is adjacent to another
component to be revised). If desired, the tools may also assist
with the removal of the failed implant (i.e., locking onto the
failed implant and incorporating a "slap hammer" connection,
providing a cut plane for severing portions of the failed implant,
sections of bone cement and/or interfering anatomical structures,
etc.) or other alignment method to assist with removal of the
"failed implant." In various embodiments, the surgical tool and/or
mold will also provide an alignment guide or marker that can be
utilized to place one or more (preferably two or more) alignment
pins or wires which can provide one or more reference points for
subsequent surgical steps (including the placement of subsequent
surgical tools) after removal of the "failed implant" has been
accomplished. Desirably, the tool will allow the alignment
marker(s) to be placed, and then the tool (and failed implant) can
be separated from the joint, leaving the alignment marker(s)
undisturbed in their desired location(s) for use in further steps
of the surgical procedure.
[0618] Once the failed implant has been removed (or while the
failed implant is still attached to the joint, if the relevant
anatomy is accessible), one or more surgical tools can be
introduced along the designated alignment guides to prepare the
joint for implantation of the revision implant. If desired, some
preparation steps may be performed before removal of the failed
implant, and some afterwards. In addition, it is contemplated that
preparation of various anatomical surfaces will allow placement of
subsequent alignment tools (using the newly prepared surface(s))
for guiding further surgical tools.
[0619] Once the underlying anatomical support structure has been
prepared (and any augments deemed necessary have been positioned
and/or secured to the support structure and/or to the implant
surface(s), if necessary), the revision implant may be placed into
the joint, and the surgery completed.
Example 4
"Failed Implant" Assisted Hip Technique
[0620] Various embodiments of this disclosure can be used for
facilitate treatment of a wide variety of joints, including
revisions of hip joint implants. This disclosure can assist a
surgeon in designing a revision implant for a failed hip joint, as
well as be used to assist the surgeon in selecting pre-manufactured
implants and/or modular implant components, including head and neck
components for revision hip implants based on independent variables
associated with physical characteristics of the implant, including
leg length, offset, and anteversion. Desirably, the steps described
herein can help a surgeon properly plan the revision surgery and
reduce or eliminate a need to change a preoperatively-chosen
implant or modular component (i.e., modular stem, neck or other
feature of the implant).
[0621] Once a set of generated data (as previously described) is
constructed using various image sources (including typical images
for a hip replacement procedure which can be taken along two
different directions, for example, anterior/posterior (NP) and
lateral pelvic images may be taken of the hip joint) and
appropriate image processing and evaluation steps, the information
may utilized to design a patient-specific implant or implant
components, and/or to select an implant and/or modular components.
For example, the surgeon may desire a change in at least one of the
variables, e.g., leg length, offset, and/or anteversion. The
present method allows the surgeon to quickly and easily select a
different modular neck based on an evaluation of one of the
variables without requiring reevaluation of the other variables.
The method can further include preoperative planning of the
surgical procedure, which advantageously provides an intuitive
system for the surgeon both preoperatively and during surgery.
[0622] A computer system with optional user input (including
various criteria entered by a surgeon and/or implant
designer/manufacturer) may be used to design/choose an appropriate
revision implant based on anatomical constraints, or a dimensional
template or other implant information may be used in conjunction
with the generated image(s) to design/choose the implant and/or to
preoperatively plan the surgical joint revision procedure. In
various embodiments, the image of the "failed implant" may be
subtracted, allowing the template to be utilized directly with the
generated image. In other embodiments, the "failed implant" may
remain on the image. If desired, the "failed implant" may be
identified by a color code or shading that differentiates it from
the remaining anatomy. Similarly, anatomical areas may be shaded,
color coded or otherwise identified to reflect an anticipated
"confidence" of the accuracy of the individual anatomical features
of the generated image. For example, the estimated anatomical
margins of the femoral canal may be shown on the image as "contour
lines" or differing shapes or colors, corresponding to confidences
of 100&, 99%, 95%, 90%, 85% and so on. A surgeon can use this
information to design/choose an implant sized to fit within an
anticipate confidence region or regions, as desired by the surgeon
or user. In a similar manner, the use can utilize the contour lines
to estimate the chances of each of a given set of implants to fit
the anatomy of the generated image.
[0623] The dimensional template may be constructed of a piece of
transparent plastic or other suitable material which may be
overlaid on the image of the hip portion of the patient, or may be
an electronic image or data set that is virtually overlaid or
otherwise manipulated relative to the generated image data. The
dimensional template/data set may include a plurality of reference
points forming a grid coordinate system, for example, a Cartesian
coordinate system, including a pattern of intersecting horizontal
and vertical indicators or lines that provide coordinates for
locating points. A plurality or system of dimensional templates may
be provided corresponding to each available size or type of hip
implant and/or implant component of a given hip implant system or
systems.
[0624] Using generated image date of the patient's anatomical
structure (optionally with the "failed implant components
subtracted from the image), the data can be utilized to select
appropriate implant components (and/or design an appropriate
implant), which can include appropriate combinations of acetabular
shells, liners (of varying materials, including plastics and
polymers such as polyethylene, ceramics, metals or composites),
femoral head size, diameter and shape, neck length, thickness,
shape, length, size and angle (i.e., anteverted neck, a straight
neck, or a retroverted neck) and femoral stem axis, length,
thickness, width, shape, curvature, variation and/or angulation, or
a single or multi-piece implant can be designed, selected and/or
manufactured.
[0625] The femoral stem may be chosen in a conventional manner such
that the representation of the stem on a dimensional template
substantially fills the intramedullary canal of the femoral shaft
of the generated image data, such that the actual femoral stem
component of the hip implant will correctly fit the intramedullary
canal of the actual femur. If desired, a non-uniform stem and/or
non-cylindrical and/or other support/anchoring structure can be
designed and/or selected based upon the generated image data.
Provision is thus made for cross-sections of the stem shaft to be
rectangular or trapezoidal with pronounced longitudinal edges which
can establish contact with the cortex to improve anchoring and
long-term implant performance. Provision could also be made for an
arcuate shape of the stem base body to be selected in particular
with respect to curvature and length in relation to two oppositely
disposed edges (i.e., a lateral edge and a medial edge) such that
an end position or other portion of the stem base body has a
plurality of contact positions to the cortex or other cortical bone
within the femoral canal (i.e., three or more contact positions
along the stem body). In this manner, the curvature of the base
body and the length of the base body and/or of the shaft could be
particularly matched pre-operatively to one another and the
surrounding anatomy.
[0626] The various features of the revision implant need not
necessarily match those of the primary implant, or even those of
the original femur, femoral head or acetabular cup. For example,
the revision femoral head location of center may not necessarily
coincide with the original center of femoral head prior to revision
surgery because the condition of the revision femoral head or other
portions of the joint may dictate a different center for the head
of the revision implant component. For example, if the original
femoral head is severely deteriorated or is badly misshapen, the
surgeon may desire a different center for the head of the revision
implant than the current center for the original femoral head.
Also, the surgeon may wish to correct some problem, e.g., laxity
correction or bone alignment correction, which may cause the center
for the head of the revision implant to be different than the
center of femoral head. The pre-operative planning and evaluation
phase permits the surgeon to obtain the preoperatively-planned
values for the offset and the leg length for the modular or
patient-designed components, including the neck component of the
hip implant.
[0627] During various embodiments of the surgical planning phase,
the surgeon (or implant/tool designer or automatic program) chooses
a desired anteversion component from various planes of reference
points and/or other image data. The representation of the femoral
stem may be oriented relative to the image data to align with the
intramedullary canal of the image of the femoral shaft. The surgeon
may then use various planes of reference points to determine a
desired anteversion component for the modular neck of the hip
implant. In one exemplary procedure, the surgeon can determine the
anteversion component first, and then determine the necessary leg
length and offset values for the preoperative plan of the
procedure. Additional planning steps can include deciding where the
center of the head of the neck should be located and/or what
anteversion component is necessary, as well as selecting/designing
a neck corresponding to the assessed variables of leg length,
offset, and anteversion. Desirably, the system will simplify the
surgeon's ability to determine the optimal position of the center
of the head of the neck 44. In various embodiments, the system may
utilize both A/P and lateral views simultaneously, or may utilize a
three-dimensional data image, with the chose/designed implants
superimposed thereon to allow the surgeon/designer to
simultaneously assess all three variables, i.e., anteversion, leg
length, and offset.
[0628] Similar patient-specific and anatomy-specific designs can be
selected/manufactured using the generated image data. For example,
areas of particular weakness (i.e., thin bone sections or areas of
limited cortical bone) can be accounted for in the design/selection
of implant components. Alternatively, areas of greater strength
and/or bone concentration (i.e., a thicker-than-expected pelvic
bone capable of accommodating a larger than normal acetabular cup)
can lead to differences in selection and/or design of the various
implant components. In addition, unique anatomy (i.e., a pelvic
bone that will require an acetabular cup of unusual or
non-spherical outer surface characteristics) can be accounted for
pre-operatively in the implant design. Similarly, surgical tools
and jigs can be designed that match or otherwise conform to (1)
anatomical structures only, (2) "failed implant" structures only
and/or combinations thereof. These surgical tools can assist with
alignment and placement of cutting/drill instruments to prepare the
anatomical support structures (i.e., femur and/or pelvis) for
implantation of revision implants. The tools/jigs can also be used
to align and/or guide tools to assist in separating the failed
implant components (i.e., failed acetabular cup and/or femoral
stems or other components) and/or adhesive materials (i.e., bone
cement and/or osteo-integrated surfaces) from the underlying
anatomical support structures.
[0629] If desired, the surgical jigs and tools described herein
(and the implants selected/designed as well) can be used to perform
hemi-arthroplasty as well as facilitate total hip joint
replacement. Such procedures could include the use of surgical
tools and/or jigs that utilize alignment surfaces from only half of
a joint (i.e., the femoral side of a hip joint) to align tools and
implant components for use on the other side of the joint (i.e.,
the pelvis). Such alignment surfaces could match or otherwise
substantially conform to anatomical and/or implant structures as
previously described. In other embodiments, the surgical tools
and/or jigs could utilize alignment surfaces from the same half of
a joint as treated/implanted. In other alternative embodiments, the
surgical tools and/or jigs could utilize alignment surfaces from
both halves of the joint to align tools and implant components for
use on one half and/or both sides of the joint.
[0630] Once the failed implant has been removed (or while the
failed implant is still attached to the joint, if the relevant
anatomy is accessible), one or more surgical tools can be
introduced along the designated alignment guides to prepare the
joint for implantation of the revision implant. If desired, some
preparation steps may be performed before removal of the failed
implant, and some afterwards. In addition, it is contemplated that
preparation of various anatomical surfaces will allow placement of
subsequent alignment tools (using the newly prepared surface(s) for
guiding further surgical tools.
[0631] Once the underlying anatomical support structure has been
prepared (and any augments deemed necessary have been positioned
and/or secured to the support structure and/or to the implant
surface(s), if necessary), the revision implant may be placed into
the joint, and the surgery completed. If desired, the surgical
procedure may involve replacement of only a single component or
components, with other components remaining intact in the joint.
For example, where an acetabular cup and/or femoral head has
significantly degraded, but the femoral stem is well secured, the
femoral stem may be allowed to remain in place, with the femoral
head removed (if modular or otherwise removable in some manner) and
replaced, and/or the acetabular cup replaced. Tools for use with
such procedures could include jigs having combinations of
patient-specific anatomic surfaces and/or implant-specific
anatomical surfaces to assist in alignment and/or preparation of
the underlying anatomical surfaces.
[0632] Aside from facilitating the creation/selection of implants
particularized for a specific patient and/or surgical procedure and
selecting/designing jigs for that procedure that utilize
combinations of anatomy/implant features for alignment, the various
embodiments described herein reduce and/or eliminate the need for a
surgeon to trial or otherwise test the size and/or suitability of
the implants and implant components in the targeted joint. The use
of patient-specific implants, in combination with tools that
utilize patient and implant specific alignment surfaces, greatly
reduces and/or eliminates the uncertainly associated with the
implantation of joint implants, including revision implants.
[0633] Although described throughout with respect to a hip implant,
the method could be utilized in any procedure which uses modular
components, for example, but not limited to, shoulder implant
procedures, knee implant procedures, etc.
Example 5
"Failed Implant" Assisted Shoulder Technique
[0634] In a healthy shoulder, the proximal humerus is generally
ball-shaped, and articulates within a socket formed by the scapula,
called the glenoid, to form the shoulder joint. Conventional
implant systems for the total replacement of the shoulder joint due
to disease or trauma, i.e., a total shoulder arthroplasty,
generally replicate the natural anatomy of the shoulder, and
typically include a humeral component having a stem which fits
within the humeral canal, and an articulating head which
articulates within the socket of a glenoid component implanted
within the glenoid of the scapula. An implant system for the
replacement of only the humeral component of the shoulder joint,
i.e., a hemi shoulder arthroplasty, typically includes only a
humeral component which articulates within the natural glenoid
socket of the scapula.
[0635] More recently, "reverse" type implant systems have been
developed in which the conventional ball-and-socket configuration
that replicates the natural anatomy of the shoulder is reversed,
such that a concave recessed articulating component is provided at
the proximal end of the humeral component that articulates against
a convex portion of the glenoid component. Such reverse shoulder
implant systems are thought to provide an increased range of motion
for treatment of glenohumeral arthritis associated with irreparable
rotator cuff damage, for example, by moving the center of rotation
between the humeral component and the glenoid component to allow
the deltoid muscles to exert a greater lever arm on the
humerus.
[0636] Various embodiments of this disclosure are particularly well
suited for treating and/or replacing failed or failing shoulder
implants, as well as for converting "reverse" type implant systems
to "normal" shoulder systems, and vica versa. By utilizing
generated image data, the current condition of the failed/failing
implant and the surrounding anatomical support structure can be
determined with significant accuracy, and an appropriate revision
implant (or implant components) can be selected and/or designed for
the patient's needs. In addition, the creation of surgical tool
and/or jigs that match or otherwise conform to (1) anatomical
structures only, (2) "failed implant" structures only and/or any
combinations thereof significantly facilitate the alignment and
placement of cutting/drill instruments to prepare the anatomical
support structures (i.e., glenoid and/or humerus) for implantation
of revision implants. The tools/jigs can also be used to align
and/or guide tools to assist in separating the failed implant
components (i.e., failed glenoid cup or other components and/or
humeral stems or other components) and/or adhesive materials (i.e.,
bone cement and/or osteo-integrated surfaces) from the underlying
anatomical support structures.
[0637] In general, standard implant systems for total shoulder
arthroplasties and hemi shoulder arthroplasties including a humeral
stem having an enlarged head portion with interfaces adapted to
removably receive various modular interchangeable components, such
as articulating liners, spacers, and adapter inserts. The humeral
stem typically functions as a universal platform that may be used
in either conventional or "reverse" total shoulder arthroplasties,
as well as hemi shoulder arthroplasties, and may remain implanted
in place during a revision in which the implant system is converted
between the foregoing configurations. Where failure of the implant
is not attributable to failure of the humeral stem, it is desirable
to retain the stem, as removal and replacement of the stem can
often be a difficult procedure. An articulating liner on the stem
generally articulates against a glenoid component, and may be
angled to change the neck angle of the humeral stem from an angle
suited for a conventional total arthroplasty or a hemi arthroplasty
to an angle suited for a "reverse" total arthroplasty. The spacer
may optionally be used to fit between the humeral stem and the
articulating liner to provide increased joint tension when needed.
An adapter insert can be used to provide an interface with a convex
articulating component in a hemi arthroplasty application. A
glenoid component is also typically provided that is mountable to
the glenoid by a plurality of polyaxial locking screws or other
devices or adhesives, and which receives a glenosphere having a
smooth, convex and uninterrupted articulating surface against which
the articulating liner of the humeral component may articulate.
[0638] In many occasions, failure of a primary shoulder joint
implant occurs as a result of displacement or rotation of the
glenoid component, especially where the anatomical supporting
structures of the glenoid/scapula have further degraded since the
initial surgery, if the initial glenoid component was oversized or
otherwise suitable for the patient's anatomy, where the patient has
failed to allow sufficient time for the components to integrate or
secure to the underlying structure, and/or where trauma has
occurred. Regardless of the underlying reason(s) for implant
failure, however, the various embodiments of this disclosure can be
used for facilitate treatment of a wide variety of joints,
including revisions of shoulder joint implants. This disclosure can
assist a surgeon in designing a revision implant for a failed
shoulder joint, as well as be used to assist the surgeon in
selecting pre-manufactured implants and/or modular implant
components, including stem and cup components for revision shoulder
implants. Desirably, the steps described herein can help a surgeon
properly plan the revision surgery and reduce or eliminate a need
to change a preoperatively-chosen implant or modular component.
[0639] Once a set of generated data (as previously described) is
constructed using various image sources (including typical images
for a shoulder replacement procedure which can be taken along
different directions) and appropriate image processing and
evaluation steps (including the use of prior patient images, if
available), the information may utilized to design a
patient-specific implant or implant components, and/or to select an
implant and/or modular components. The present method allows the
surgeon to quickly and easily select/design implant components
based on an evaluation of many variables without requiring
reevaluation of the other variables of the joint. The method can
further include preoperative planning of the surgical procedure,
which advantageously provides an intuitive system for the surgeon
both preoperatively and during surgery.
[0640] A computer system with optional user input (including
various criteria entered by a surgeon and/or implant
designer/manufacturer) may be used to design/choose an appropriate
revision implant based on anatomical constraints, or a template or
other implant information may be used in conjunction with the
generated image(s) to design/choose the implant and/or to
preoperatively plan the surgical joint revision procedure. In
various embodiments, the image of the "failed implant" may be
subtracted, allowing the template to be utilized directly with the
generated image. In other embodiments, the "failed implant" may
remain on the image. If desired, the "failed implant" may be
identified by a color code or shading that differentiates it from
the remaining anatomy. Similarly, anatomical areas may be shaded,
color coded or otherwise identified to reflect an anticipated
"confidence" of the accuracy of the individual anatomical features
of the generated image. For example, the estimated anatomical
margins of the humeral canal or the margins of the glenoid bone may
be shown on the image as "contour lines" or differing shapes or
colors, corresponding to confidences of 100&, 99%, 95%, 90%,
85% and so on. A surgeon can use this information to design/choose
an implant sized to fit within an anticipate confidence region or
regions, as desired by the surgeon or user. In a similar manner,
the use can utilize the contour lines to estimate the chances of
each of a given set of implants to fit the anatomy of the generated
image.
[0641] The template may be constructed of a piece of transparent
plastic or other suitable material which may be overlaid on the
image of the shoulder of the patient, or may be an electronic image
or data set that is virtually overlaid or otherwise manipulated
relative to the generated image data. The template/data set may
include a plurality of reference points forming a grid coordinate
system, for example, a Cartesian coordinate system, including a
pattern of intersecting horizontal and vertical indicators or lines
that provide coordinates for locating points. A plurality or system
of templates may be provided corresponding to each available size
or type of shoulder implant and/or implant component of a given
shoulder implant system or systems.
[0642] Using generated image date of the patient's anatomical
structure (optionally with the "failed implant components
subtracted from the image), the data can be utilized to select
appropriate implant components (and/or design an appropriate
implant), which can include appropriate combinations of glenoid
cups, humeral components (i.e., stems of differing length,
thickness, shape, length, size and angle, heads of different size,
diameter and shape, liners of varying materials, including plastics
and polymers such as polyethylene, ceramics, metals or composites,
etc.) and or sleeves or spacers, etc., or a single or multi-piece
implant can be designed, selected and/or manufactured.
[0643] The various features of the revision implant need not
necessarily match those of the primary implant. For example, the
revision shoulder components could be a "reverse" shoulder, where
the original failed should was a "standard" implant set. As another
alternative, the revision glenoid cup may include one or more
additional anchoring components, including a "glenoid or scapular
stem" that extends from the glenoid fossa into the scapula. If
desired, the generated image data can be utilized to design a
glenoid cup component having an attached (or attachable) stem that
follows a medullary canal of the scapula, which would permit
replacement of a failed glenoid cup, even where significant damage
to the glenoid bone obviates replacement with a standard cup.
[0644] As with other joint designs, the revision shoulder system
need not be of the same design from the patient's original anatomy
(although it could be designed the same, if desired), possibly
because the condition of the revision humeral head or other
portions of the joint may dictate a different center for the head
of the revision implant component. For example, if the original
humeral head is severely deteriorated or is badly misshapen, the
surgeon may desire a different center for the head of the revision
implant than the current center for the original humeral head.
Also, the surgeon may wish to correct some problem, e.g., laxity
correction or bone alignment correction, which may cause the center
for the head of the revision implant to be different than the
center of humeral head. The pre-operative planning and evaluation
phase permits the surgeon to obtain the preoperatively-planned
values for the offset and the leg length for the modular or
patient-designed components, including the neck component of the
shoulder implant.
[0645] In various embodiments, patient-specific and
anatomy-specific designs for implants and/or tools can be
selected/manufactured using the generated image data. For example,
areas of particular weakness (i.e., thin bone sections or areas of
limited cortical bone) can be accounted for in the design/selection
of implant components. Alternatively, areas of greater strength
and/or bone concentration (i.e., a thicker-than-expected scapular
bone capable of accommodating a larger than normal glenoid cup) can
lead to differences in selection and/or design of the various
implant components. In addition, unique anatomy (i.e., a scapular
bone that will require an glenoid cup of unusual or non-spherical
outer surface characteristics, or one that requires additional
support from a scapular stem) can be accounted for pre-operatively
in the implant design. Similarly, surgical tools and jigs can be
designed that match or otherwise conform to (1) anatomical
structures only, (2) "failed implant" structures only and/or
combinations thereof. These surgical tools can assist with
alignment and placement of cutting/drill instruments to prepare the
anatomical support structures (i.e., humerus and/or
scapula/glenoid) for implantation of revision implants. The
tools/jigs can also be used to align and/or guide tools to assist
in separating the failed implant components (i.e., failed glenoid
cup and/or humeral stems or other components) and/or adhesive
materials (i.e., bone cement and/or osteo-integrated surfaces) from
the underlying anatomical support structures.
[0646] If desired, the surgical jigs and tools described herein
(and the implants selected/designed as well) can be used to perform
hemi-arthroplasty as well as facilitate total shoulder joint
replacement. Such procedures could include the use of surgical
tools and/or jigs that utilize alignment surfaces from only half of
a joint (i.e., the humeral side of a hip joint) to align tools and
implant components for use on the other side of the joint (i.e.,
the scapula/glenoid). Such alignment surfaces could match or
otherwise substantially conform to anatomical and/or implant
structures as previously described. In other embodiments, the
surgical tools and/or jigs could utilize alignment surfaces from
the same half of a joint as treated/implanted. In other alternative
embodiments, the surgical tools and/or jigs could utilize alignment
surfaces from both halves of the joint to align tools and implant
components for use on one half and/or both sides of the joint.
[0647] Once the failed implant has been removed (or while the
failed implant is still attached to the joint, if the relevant
anatomy is accessible), one or more surgical tools can be
introduced along the designated alignment guides to prepare the
joint for implantation of the revision implant. If desired, some
preparation steps may be performed before removal of the failed
implant, and some afterwards. In addition, it is contemplated that
preparation of various anatomical surfaces will allow placement of
subsequent alignment tools (using the newly prepared surface(s))
for guiding further surgical tools.
[0648] Once the underlying anatomical support structure has been
prepared (and any augments deemed necessary have been positioned
and/or secured to the support structure and/or to the implant
surface(s), if necessary), the revision implant may be placed into
the joint, and the surgery completed. If desired, the surgical
procedure may involve replacement of only a single component or
components, with other components remaining intact in the joint.
For example, where an glenoid cup and/or humeral head has
significantly degraded, but the humeral stem is well secured, the
humeral stem may be allowed to remain in place, with the humeral
head removed (if modular or otherwise removable in some manner) and
replaced, and/or the glenoid cup replaced. Tools for use with such
procedures could include jigs having combinations of
patient-specific anatomic surfaces and/or implant-specific
anatomical surfaces to assist in alignment and/or preparation of
the underlying anatomical surfaces.
[0649] Aside from facilitating the creation/selection of implants
particularized for a specific patient and/or surgical procedure and
selecting/designing jigs for that procedure that utilize
combinations of anatomy/implant features for alignment, the various
embodiments described herein reduce and/or eliminate the need for a
surgeon to trial or otherwise test the size and/or suitability of
the implants and implant components in the targeted joint. The use
of patient-specific implants, in combination with tools that
utilize patient and implant specific alignment surfaces, greatly
reduces and/or eliminates the uncertainly associated with the
implantation of joint implants, including revision implants.
Example 6
Improvement to Standard Revision Procedure
[0650] The various embodiments of this disclosure disclosed herein
can significantly reduce the complexity and/or significantly
improve the outcome of a surgical procedure for revising a failed
or failing joint implant. In the current practice, an example of
which is described in the Zimmer Nexgen LCCK TKA Surgical Technique
Guide (commercially available from Zimmer, Inc.), the access and
immediate removal of a failed or failing joint implant is generally
the initial step in a revision surgical procedure. Once implant
removal has been accomplished, a surgeon is required to utilize a
number of surgical tools and alignment guides, and generally
prepare and implant one or more anchoring/measurement devices
(i.e., intramedullary stems, etc.), in an initial effort to align
and position various tools for guiding the subsequent surgical cuts
and/or drill holes made into the anatomical support structure. In
the case of preparing a tibia for a Nexgen revision implant, the
surgeon is initially directed to remove the failed implant, and
then must drill/ream into the tibial canal and place a provisional
tibial stem or reamer within the canal. Numerous tools and/or
alignment guides are then attached to the stem/reamer, including
external alignment rods, cutting jigs and/or alignment/sizing
plates, in an effort to create a desired anatomical support surface
and choose the proper size/shape components to fit the created
support surface. The Nexgen technique guide identifies over nine
separate tools and attachments necessary to align and guide the
cutting tools for preparing just the tibial surface and canal.
[0651] In contrast, various embodiments of this disclosure can
accomplish the same alignment and surface preparation for the tibia
utilizing a bare handful of tools. In one embodiment, an alignment
jig can be created having an inner surface that matches and/or
substantially conforms to some or all of the existing "failed
implant" and/or the surrounding tibial bone surfaces (if desired).
This jig can include a pair of openings on a lateral side to
accommodate a plurality of alignment pins. The jig can further
incorporate one or more slots or cutting guides, if desired, to
facilitate the accurate and safe cutting of the tibial surface with
the failed implant still in position in the joint (if desired).
Alternatively, the jig can be removed after placement of the
markers and/or the jig can "dock" with the failed implant and
assist with implant removal. Once the jig and failed implant have
been removed, a second jig (or the same jig initially used, but
without any attached failed implant) can be positioned over the
alignment pins, and drill guides and/or cutting slots on the jig
can be accessed to prepare the tibial bone for the revision
implant. Additional openings in the jig can accommodate additional
surgical tools, if necessary, including saw blades for planar cuts
as well as reamer and/or drill openings for placement of anchoring
structures and/or support pins. The tibial surface is then prepared
and ready for implantation.
[0652] The use of assessment and planning software, in combination
with creation of jigs having anatomic-specific and/or
implant-specific conforming features allows the surgery to be
planned pre-operatively, allows the implant to be designed and/or
selected to match the anticipated support structure for the
revision implant, and allows the creation of jigs to be properly
aligned without requiring the surgeon to resort to aligning the
implant off an intramedullary canal or other anatomical features
remote or unaffected by the joint implant failure or joint
deterioration. In addition, the present embodiments significantly
reduce the need for the surgeon to measure, evaluate and calculate
alignment planes, cutting planes and reaming/drilling depths in a
"free-hand" or "gut feel" manner, which can lead to significant
mistakes and/or unintended consequences for the patient.
[0653] If desired, in addition to the tools and implants described
herein, various additional embodiments contemplate the creation of
a "backup" or "rescue" revision implant system and tools. It is
possible, but highly unlikely, that the various embodiments
described herein would recommend the creation of an implant and/or
surgical tools that would not properly engage or substantially
conform to the failed implant and/or the underlying anatomical
structure of the failed joint. In such a case, a set of surgical
tools can be created to accommodate a wide variety of variation in
the implant surface and/or anatomical structure surface, yet
provide sufficient alignment information to permit the surgical
creation of a desired anatomical support structure and implantation
of a replacement implant. In such cases, it may be desirable that
the tools and/or implant include one or more "anatomical reliefs"
to accommodate variations in the underlying structure(s). For
example, a jig could be designed and constructed with a relative
large internal cavity that accommodates a wide variety of implant
shapes and sizes, but that includes one or more features that
contact and/or otherwise interact with accessible known surfaces on
the patient's bone and/or failed implant. Such features could
include edges that conform to the outer cortical wall of the tibial
tuberosity, and/or the tibal neck, with additional features that
contact the upper surface of the failed tibial tray implant. Such a
design could potentially accommodate a variety of tray perimeter
sizes and/or thickness, while providing sufficient alignment and
positioning information to prepare the tibial surface for implant
placement. In various alternate embodiments, the tools and/or
implant could incorporate one or more inserts that comprise a
surface that matches or substantially conforms to an estimates
anatomical or implant surface, but that can be removed (if desired)
to reveal a different surface and/or anatomical relief surface for
accommodating the unexpected anatomy/implant features.
Example 7
Jigs for Creating Anatomical References
[0654] In various embodiments, the one or more jigs incorporating
patient-specific and/or failed implant specific conforming features
desirably provide "known" reference point(s) and/or reference
plane(s) for use by the surgeon during the surgical procedure. For
example, the jigs may conform to and interact with reference
features of the failed implant which are in a known relationship
(through the image assessment and evaluation process) to one or
more anatomical axis of the joint and/or limb. Placement of the jig
onto the failed implant or some portion thereof, and subsequent
placement of alignment markers through known jig alignment points
(or relative to known alignment from the jib) and into the bone or
relative to some other surface, allows the failed implant (and/or
jig) to subsequently be removed while retaining known alignment
position(s) relative to the joint. Subsequent tools can utilize the
alignment markers in a known manner to align surgical cutting tools
and create a desired anatomical support structure for the revision
implant.
[0655] In a similar manner, other embodiments of jigs may utilize
various combinations of failed implant surfaces and/or anatomical
surfaces (or combinations thereof) to align jig components. Such
tools could include implant only alignment, implant and anatomical
structure alignment and/or anatomical structure only alignment.
Such tools could also include various combinations of failed
implant/anatomical alignment structures that also permit jig
alignment using anatomy only, such as where the failed implant has
been removed and/or alignment of the failed implant is uncertain
(i.e., the implant shifts or rotates relatively freely or where it
has been displaced or otherwise moved in an undesirable manner at
some point during the surgical procedure).
[0656] Alternative embodiments of jigs may be utilized directly in
contact with a failed implant, with the failed implant still
attached and/or in position within the joint, and the jig could
incorporate alignment guides that allow cutting or other
preparation of the bone via unobstructed access around and/or
through the failed implant. For example, one exemplary jig could
include an inner surface that conforms in some manner to a failed
tibial tray implant (additional alignment features could include
the anterior cortex or other anatomical structures, including
residual bone information as well as information on osteophytes
and/or osteolysis). The jig could include a saw cut alignment guide
adjacent to the anterior portion of the tibial head, yet positioned
below the lower margin of the tibial tray (i.e., a set distance or
height below the tibial plateau or other tibial surface). One or
more cutting saws could be introduced through the alignment guide
and cut portions of a planar tibial surface with the failed implant
still in position. If desired, the alignment guide could
incorporate "cut outs" or other such barriers (which may be modular
and/or removable at the user's option) to prevent the saw blades
from encountering undesirable obstructions or other anatomical
areas, such as an intramedullary rod or tibial tray anchor
extending down into the tibial bone from the failed tibial tray.
Once sufficient surgical cutting has been accomplished, the jig may
be removed, and then the implant may be removed (or they may be
removed concurrently). Such steps may simplify the removal of
failed implant components, and could significantly reduce the
potential for additional anatomical damage caused when the implant
and/or support structure (i.e., anchors, cement, bone ingrowth
surfaces, etc.) is removed (possibly breaking additional anatomical
structures off the bone).
Example 8
Implants/Tools Accounting For Defects
[0657] Various embodiments of this disclosure contemplate the use
of the generated image information to account for and/or
accommodate defects and/or other undesirable anatomical features.
For example, the generated image information can be utilized to
determine areas of defects and/or osteolysis, as well as areas that
may have degraded in some other fashion, or have anatomical
structures that are desirably removed (i.e., osteophytes, etc.)
prior to implantation of a revision prosthesis. If desired, the
surgical tools and/or revision implant can be selected and/or
designed to have "protrusions," voids or other such features that
accommodate or otherwise fill or partially fill the defects and/or
removed structures. Other embodiments can include the use of
generated image information to select wedges, spacer blocks and/or
other structures for use with the surgical tools and/or revision
implant. These embodiments contemplate the use of surgical tools
that account for the use of such structures, including the use of
spacers or other structures that modularly "snap in" (or connect or
secure to the tool on other such fashion) and may optionally be
removable. Various modular pieces may include surfaces that conform
to underlying anatomical or implant structures, such that they can
be inserted and/or removed as needed during the surgical procedure
to replicate the underlying surface(s) with which they
interact.
Example 9
Jigs to Prepare Femoral Canal
[0658] If desired, the various embodiments described herein can be
utilized in conjunction with standard implants and/or surgical
tools, including partial joint replacement/resurfacing systems
and/or standard total joint (or partial joint) revision implant
systems. As previously noted, the present systems can replace
multiple tool sets used in standard systems to identify anatomical
landmarks, guide cutting and drilling/reaming tools, and assist
with removal of failed implant components as well as preparation of
the anatomical support system for a replacement implant. If
desired, various embodiments of this disclosure may also be used to
assist with balancing of soft tissues and articulating
surfaces.
[0659] One example of a jig to assist in preparation and/or
placement of a standard revision implant system could include a
patient-specific upper surface that substantially conforms to, or
otherwise references, anatomical or other structures of the
patient's femoral surfaces (i.e., anterior cortex, resected bone,
bony defects, osteolysis, resected femoral surfaces and/or residual
cement surfaces still integrated with the bone). An access or guide
path is provided through the jig for a reamer, drill or other
cutting instrument. Desirably, this guide path has been designed in
conjunction with generated image data to follow a "desired
trajectory" relative to an anatomical, mechanical or other axis
determined from the image data. In various embodiments, the guide
path is designed to avoid contact with the cortical wall of the
canal, although other embodiments may seek such to abut or
otherwise contact the cortical walls for potentially added
anchoring strength or other objective. The guide path may be
linear, cylindrical, tortuous, or any combination thereof.
[0660] A surgical cutting tool such as a drill or reamer may be
introduced down the guide path and create a canal channel for
accommodating a femoral stem or other anchoring device. The channel
may be formed into virtually any shape, but will desirably be
aligned by the guide path, and generally follow the contour of the
channel. If desired, the channel may be curved or follow other
shapes (i.e., may accommodate variations in the canal wall shape,
etc.), with the stem or other anchor designed in a similar shape to
fit or otherwise be accommodated by the channel.
Example 10
Optional Femoral Canal Tools
[0661] If desired, the surgical tool kit and implant system can
include "optional" components or features that facilitate the
surgeon's/implant's ability to accommodate unexpected anatomy
and/or correct surgical "mistakes" or other undesirable events
occurring during the surgical procedure. For example, the generated
image data may indicate that sufficient natural anatomy remains
(after removal of the failed implant) to support a revision implant
without need for a femoral stem or other auxiliary support
structure, but during the surgical procedure it becomes apparent
that insufficient support structure remains. Similarly, anatomical
support material that was intended to be used to support the
revision implant may adhere to the failed implant and/or "break
off" from the bone during implant removal or anatomical surface
cutting and preparation.
[0662] In one embodiment a tibial jig could include an optional
"plug" or other feature that, when removed, reveals a "guide path"
formed in the jig to accommodate a tibial canal cutting tool (i.e.,
drill or reamer) for creating a channel within the tibial medullary
canal for placement of a tibial stem or other auxiliary anchoring
device. A tibial stem or other anchoring device could be included
as part of the revision implant kit, to be utilized if necessary.
In a similar fashion, the revision tibial tray could include
optional connection devices (for securing to the tibial stem or
other anchoring device), or an alternate tibial tray suitable for
use with the anchoring device could be provided as well. If
desired, blocks, wedges and/or other spacers may be provided as
well.
[0663] Similar auxiliary anchoring devices could be provided for
use with other joints or other joint portions, including the
femoral side of the knee joint.
Example 11
Implant Reference iJig.RTM. Surgical Tool for Revision Surgery
[0664] An Implant Reference Surgical Tool (e.g., an iJig.RTM. tool)
can rest on an existing implant or implants, such as for example in
a knee replacement, on the tibial plateau or femoral condyle in
order to place a new, revision implant precisely on the tibial
plateau or the femoral condyle.
[0665] In a conventional revision surgery, once the existing
implant is removed, there is no clear useable references on the
implantation site from which to generate a new, revision implant
and related iJig.RTM. tools to place the new, revision implant.
[0666] In one aspect of this disclosure, original, electronically
maintained files of the existing implant (e.g., an iUni.RTM.
implant system) for a patient, if available, can be used as a
reference for the placement of a new, revision implant (e.g., an
iUni.RTM. implant system, iDuo.RTM. implant system, or iTotal.RTM.
implant system). Further, to adjust for any placement issues during
the original surgery, the electronic files can be compared to new
image data obtained from the patient. Adjustments can be made to
relocate the electronic implant such that it matches the location
of the implant in accordance with the new image data. In one
embodiment, the electronic files can be saved in a new location for
making new reference files of the original implant that is now
failing or otherwise in need of revision.
[0667] The original implant reference files (e.g., original
electronic files used for making the original implant that is now
failing and in need of revision) along with the patient's
information (e.g., information about various surfaces of the
patient's joint and/or the existing implant) from the new image
data can now be used to determine the placement of a new implant.
Accordingly, new surgical tools (e.g., iJig.RTM. tools) can be
designed and made according to the desired placement of the new
implant.
[0668] In certain embodiments, during the revision surgery, the
existing implant in the patient will not be removed until at least
one implant reference surgical tool have presented at least one
cutting or drilling location.
[0669] The foregoing description of embodiments of this disclosure
has been provided for the purposes of illustration and description.
It is not intended to be exhaustive or to limit this disclosure to
the precise forms disclosed. Many modifications and variations will
be apparent to the practitioner skilled in the art. The embodiments
were chosen and described in order to best explain the principles
of this disclosure and its practical application, thereby enabling
others skilled in the art to understand this disclosure and the
various embodiments and with various modifications that are suited
to the particular use contemplated. It is intended that the scope
of this disclosure be defined by the following claims equivalents
thereof.
* * * * *
References