U.S. patent application number 16/695988 was filed with the patent office on 2020-04-02 for solid freeform fabrication of implant components.
The applicant listed for this patent is ConforMIS, Inc.. Invention is credited to Philipp Lang, John Slamin.
Application Number | 20200100909 16/695988 |
Document ID | / |
Family ID | 1000004500544 |
Filed Date | 2020-04-02 |
View All Diagrams
United States Patent
Application |
20200100909 |
Kind Code |
A1 |
Lang; Philipp ; et
al. |
April 2, 2020 |
Solid Freeform Fabrication of Implant Components
Abstract
Disclosed are designs, methods and systems for manufacturing
implants, implant components, features of implant components,
and/or related tools using solid freeform fabrication or additive
metals technologies.
Inventors: |
Lang; Philipp; (Lexington,
MA) ; Slamin; John; (Wrentham, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ConforMIS, Inc. |
Billerica |
MA |
US |
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|
Family ID: |
1000004500544 |
Appl. No.: |
16/695988 |
Filed: |
November 26, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15582994 |
May 1, 2017 |
10485676 |
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16695988 |
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14033095 |
Sep 20, 2013 |
9636229 |
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15582994 |
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61703768 |
Sep 20, 2012 |
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61801992 |
Mar 15, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22F 3/1055 20130101;
A61F 2002/4619 20130101; A61F 2/389 20130101; A61F 2002/30985
20130101; Y10T 29/49 20150115; A61F 2002/30878 20130101; B33Y 10/00
20141201; A61F 2/461 20130101; B33Y 50/00 20141201; A61B 2034/102
20160201; B23K 26/342 20151001; A61F 2002/30962 20130101; A61B
17/1764 20130101; B33Y 50/02 20141201; B23K 15/0086 20130101; B22F
2998/10 20130101; B33Y 80/00 20141201; A61F 2002/30561 20130101;
A61F 2002/4495 20130101 |
International
Class: |
A61F 2/46 20060101
A61F002/46; A61F 2/38 20060101 A61F002/38; B33Y 80/00 20060101
B33Y080/00; B33Y 10/00 20060101 B33Y010/00; B33Y 50/02 20060101
B33Y050/02; B23K 26/342 20060101 B23K026/342; B22F 3/105 20060101
B22F003/105; B23K 15/00 20060101 B23K015/00 |
Claims
1. A tibial implant component, the tibial implant component
comprising: a tibial tray; and at least one anchoring structure
extending distally from a bone-facing surface of the tibial tray,
the anchoring structure having a proximal end and a distal end
separated by a first length, wherein the tibial tray is configured
to include a substantially solid structure, wherein the bone-facing
surface of the tibial tray further includes porous surface features
configured to promote bone ingrowth, wherein a proximal portion of
the anchoring structure consists of two or more cavities adjacent
to the bone facing surface of the tibial tray, and wherein the
tibial tray and the anchoring structure are integral and formed of
a single material.
2. The tibial implant component of claim 1, wherein the anchoring
structure comprises an anchoring peg.
3. The tibial implant component of claim 2, wherein the anchoring
structure further comprises one or more wings configured to provide
rotational stability to the tibial tray.
4. The tibial implant component of claim 3, further comprising two
or more peripheral anchoring pegs extending distally from the
bone-facing surface of the tibial tray, the peripheral anchoring
pegs each having a proximal end and a distal end separated by a
second length, wherein the second length is smaller than the first
length.
5. An implant component comprising: a first implant portion having
a substantially solid structure, the first implant portion having a
bone-facing surface; an anchoring structure extending distally from
the bone-facing surface of the first implant portion; and a second
implant portion having a substantially porous structure, the second
implant portion distal to the first implant portion, wherein a
proximal portion of the anchoring structure consists of two or more
cavities adjacent to the second implant portion, and wherein the
first implant portion and the anchoring peg are integral and formed
of a single material.
6. The implant component of claim 5, wherein the anchoring
structure comprises an anchoring peg.
7. The implant component of claim 6, wherein the anchoring
structure further comprises one or more wings configured to provide
rotational stability to the implant component.
8. The implant component of claim 5, wherein at least one dimension
of the implant component is based on patient-specific
information.
9. The implant component of claim 5, wherein at least one dimension
of the anchoring peg is based on patient-specific information.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 15/582,994, entitled "Solid Freeform Fabrication of Adaptable
Implant Components," filed May 1, 2017, which in turn is a
divisional of U.S. application Ser. No. 14/033,095, entitled "Solid
Freeform Fabrication of Adaptable Implant Components," filed Sep.
20, 2013, which in turn claims the benefit of U.S. Provisional
Application No. 61/703,768, entitled "Solid Freeform Fabrication of
Adaptable Implant Components" filed Sep. 20, 2012, and U.S.
Provisional Application No. 61/801,992, entitled "Solid Freeform
Fabrication of Adaptable Implant Components" filed Mar. 15, 2013.
Each of the above-described applications is hereby incorporated
herein by reference in its entirety.
TECHNICAL FIELD
[0002] The embodiments described herein relate to methods and
systems for manufacturing implants, implant components and/or
related tools using solid freeform fabrication or additive metals
technologies, including SLM (selective laser melting). More
specifically, embodiments described herein include implants
incorporating porous features.
BACKGROUND
[0003] Recently, the joint replacement field has come to embrace
the concept of "patient-specific" and "patient-engineered" implant
systems. With such systems, the surgical implants, associated
surgical tools and procedures are designed or otherwise modified to
account for and accommodate the individual anatomy of the patient
undergoing the surgical procedure. Such systems typically utilize
non-invasive imaging data, taken of the individual pre-operatively,
to guide the design and/or selection of the implant, surgical
tools, and the planning of the surgical procedure itself. Because
"patient-specific" and "patient-engineered" implant systems are
created using anatomical information from a particular patient,
such systems are generally created after the patient has been
designated a "surgical candidate" and undergone non-invasive
imaging.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 depicts a schematic view of equipment and the process
used in a typical SLM manufacturing process;
[0005] FIG. 2A depicts a perspective view of a frangible portion or
link to facilitate separation of an implant component portion at a
predetermined location;
[0006] FIG. 2B depicts a side plan view of the frangible link of
FIG. 2A;
[0007] FIG. 3A depicts a partial view of a frangible portion formed
internally within an implant body;
[0008] FIG. 3B depicts the frangible portion of FIG. 3A
separated;
[0009] FIG. 4 depicts a side plan view of one exemplary embodiment
of tibial tray implant;
[0010] FIGS. 5A through 5E depict exemplary surgical steps for
removing the implant of FIG. 4 from a patient's anatomy;
[0011] FIG. 6 depicts a side plan view of an alternative embodiment
of a tibial tray implant;
[0012] FIG. 7 depicts a side plan view of another alternative
embodiment of a tibial tray implant;
[0013] FIGS. 8A through 8C depict exemplary surgical steps for
removing the implant of FIG. 7 from a patient's anatomy;
[0014] FIGS. 9A and 9B depict one embodiment of a guide tool for
use in removing the implant of FIG. 7 from a patient's anatomy;
[0015] FIGS. 10A through 10C depict exemplary surgical steps for
removing an implant without a frangible portion or other revision
feature; and
[0016] FIG. 11 depicts a side plan view of an exemplary embodiment
of tibial tray including a peg comprising a mesh structure.
DETAILED DESCRIPTION
[0017] Solid Freeform Fabrication (SFF) includes a group of
emerging technologies that have revolutionized product development
and manufacturing. The common feature shared by these technologies
is the ability to produce freeform, complex geometry components
directly from a computer generated model. SFF processes generally
rely on the concept of layerwise material addition in selected
regions. A computer generated model serves as the basis for making
a replica. The model is mathematically sliced and each slice is
recreated in the material of choice to build a complete object. A
typical SFF machine can be likened to a miniaturized "manufacturing
plant" representing the convergence of mechanical, chemical,
electrical, materials and computer engineering sciences.
[0018] Various of the embodiments described herein include
advancements and improvements in or related to the use of SFF and
Rapid Prototyping (RP) or "additive" manufacturing processes,
including Selective Laser Sintering (SLS), Direct Metal Laser
Sintering (DMLS), Electron Beam Melting (EBM) and Selective Laser
Melting (SLM) techniques, in the design, selection, development,
manufacturing and/or finishing of patient-specific and/or
patient-engineered implant components.
[0019] While SFF can be used to manufacture a wide variety of
object shapes, there are a host of perceived disadvantages and/or
limitations associated with various of these techniques that have
served to limit their widespread adoption. In the case of such
additive manufacturing, these disadvantages can include implant
components and/or tools that (1) can be limited in the range of
potential implant materials, (2) often have a rough grainy and
porous surface finish, (3) often experience high temperature
gradients that can result in a build-up of thermal stresses, (4)
typically experience a relatively large shrink rate that can cause
the part (or portions thereof) to warp, bow or curl, (5) undergo a
rapid solidification, often leading to the occurrence of
segregation phenomena and the presence of non-equilibrium phases,
(6) have a surface feature detail that is relatively coarse, and
the object can have a surface roughness created by the layer-wise
building techniques (e.g., the "staircase effect"), (7) are to some
extent dependent upon the stability, dimensions and behavior of the
particle "melt pool," which can determine to a great extent the
porosity and surface roughness, and (8) require specialized and
relatively expensive equipment (e.g., the laser printing machinery
and specially processed raw materials) for manufacture, as well as
highly trained operators.
[0020] Typically, SFF manufacturing processes and techniques seek
to minimize and/or eliminate the various inherent deficiencies or
weaknesses, especially when final functional parts are being
manufactured. However, in various embodiments disclosed herein, the
controlled inclusion of manufacturing artifacts, such as various
combinations of the "disadvantages" previously discussed, can
facilitate the creation and/or manufacture of implant components
that are particularly well suited for use in accommodating
unanticipated intraoperative modifications. In many cases, SFF
manufacturing processes can be employed to create patient-specific
implants that are adaptable to a variety of surgical "options"
presented to a surgeon, with one or more user-executed
modifications to the implant component desirably altering the
implant shape and/or performance to match the chosen surgical
outcome.
[0021] Various embodiments, and the various SFF manufacturing
techniques described herein, including SLS, DMLS, EBM or SLM
manufacturing, may be utilized to create complex geometries and/or
surfaces that can be employed for a variety of functions, which
could include the creation of textured and/or porous-walled
surfaces, including cement pockets and/or bony ingrowth surfaces,
for securing the implant to the patient's underlying bone. Various
shapes could include defined micro-cavities and/or
micro-protrusions on and/or within the implant surface.
[0022] While patient-specific and/or patient-adapted/engineered
implants have seen significantly increased adoption rates over the
past decade, there are many situations where an implant created
using patient-specific anatomical information may not be an optimal
solution for the patient's surgical needs. While modular and
one-size-fits all implants typically require significantly more
bone and tissue removal than their patient-specific counterparts,
the ability to stock and inventory a wide variety of such implant
components and surgical tools in a modular system can provide a
surgical flexibility that patient-specific implants may find
difficult to match in a cost-effective manner. For example, if
direct visualization of a patient's anatomy impels a surgeon to
resect significantly more anatomical structure than was originally
intended (based on earlier non-invasive imaging studies), a
commensurate change to the desired implant shape and/or size
necessitated by the altered resection might be fulfilled by
choosing a different sized modular implant component from
inventory. In a similar manner, if the local bone conditions are
better than the surgeon originally anticipated from pre-operative
images, the surgeon might choose to resect significantly less of
the anatomical structures, and/or possibly opt for an alternative
implant system (and/or component thereof) that utilizes
bony-ingrowth surfaces, rather than relying on securement based on
bone cement and/or other surgical materials.
[0023] Moreover, because a patient's anatomy is constantly
remodeling and changing, as well as the ever-present potential for
infection, dislocation, excessive wear and/or failure of implant
components, many patients are forced to eventually undergo one or
more revision surgeries to repair and/or replace a joint implant
(and/or component thereof) that has become damaged, malfunctions
and/or is unacceptably painful. In many cases, portions of the
implant that are removed may still be securely attached to the
underlying anatomy, and the removal of such components can involve
unnecessary damage to the patient's anatomy that can further
complicate the revision and/or healing process.
[0024] To alleviate, address and/or accommodate such concerns,
various embodiments described herein include implant components
that incorporate frangible links, deformable regions, surface
textures and/or other features that facilitate and/or enable the
intraoperative modification of patient-specific and/or
patient-adapted implant components by surgical personnel. Features
described herein, which can be specifically tailored to an
individual anatomy, can facilitate the use of standard and/or
readily available surgical tools to alter various implant features
to accommodate modifications that may occur during the surgical
procedure. Moreover, the various features can be manufactured as
part of the initial manufacturing process, which may include
creation of one or more implant components using Solid Freeform
Fabrication methods, including via SLM.
Manufacturing Technologies
[0025] Various technologies appropriate for manufacturing implants
and tools are known in the art, for example, as described in
Wohlers Report 2009, State of the Industry Annual Worldwide
Progress Report on Additive Manufacturing, Wohlers Associates, 2009
(ISBN 0-9754429-5-3), available from the web
www.wohlersassociates.com; Pham and Dimov, Rapid manufacturing,
Springer-Verlag, 2001 (ISBN 1-85233-360-X); Grenda, Printing the
Future, The 3D Printing and Rapid Prototyping Source Book, Castle
Island Co., 2009; Virtual Prototyping & Bio Manufacturing in
Medical Applications, Bidanda and Bartolo (Eds.), Springer, Dec.
17, 2007 (ISBN: 10: 0387334297; 13: 978-0387334295); Bio-Materials
and Prototyping Applications in Medicine, Bartolo and Bidanda
(Eds.), Springer, Dec. 10, 2007 (ISBN: 10: 0387476822; 13:
978-0387476827); Liou, Rapid Prototyping and Engineering
Applications: A Toolbox for Prototype Development, CRC, Sep. 26,
2007 (ISBN: 10: 0849334098; 13: 978-0849334092); Advanced
Manufacturing Technology for Medical Applications: Reverse
Engineering, Software Conversion and Rapid Prototyping, Gibson
(Ed.), Wiley, January 2006 (ISBN: 10: 0470016884; 13:
978-0470016886); and Branner et al., "Coupled Field Simulation in
Additive Layer Manufacturing," 3rd International Conference PMI,
2008.
Exemplary Techniques for Forming or Altering a Patient-Specific
and/or Patient-Engineered Implant Component for a Patient's
Anatomy
TABLE-US-00001 Technique Brief description of technique and related
notes CNC CNC refers to computer numerically controlled (CNC)
machine tools, a computer-driven technique, e.g., computer-code
instructions, in which machine tools are driven by one or more
computers. Embodiments of this method can interface with CAD
software to streamline the automated design and manufacturing
process. CAM CAM refers to computer-aided manufacturing (CAM) and
can be used to describe the use of software programming tools to
efficiently manage manufacturing and production of products and
prototypes. CAM can be used with CAD to generate CNC code for
manufacturing three- dimensional objects. Casting, Casting is a
manufacturing technique that employs a including mold. Typically, a
mold includes the negative of the casting desired shape of a
product. A liquid material is poured using into the mold and
allowed to cure, for example, with time, rapid cooling, and/or with
the addition of a solidifying agent. prototyped The resulting solid
material or casting can be worked casting subsequently, for
example, by sanding or bonding to patterns another casting to
generate a final product. Welding Welding is a manufacturing
technique in which two components are fused together at one or more
locations. In certain embodiments, the component joining surfaces
include metal or thermoplastic and heat is administered as part of
the fusion technique. Forging Forging is a manufacturing technique
in which a product or component, typically a metal, is shaped,
typically by heating and applying force. Rapid Rapid prototyping
refers generally to automated prototyping construction of a
prototype or product, typically using an additive manufacturing
technology, such as EBM, SLS, SLM, SLA, DMLS, 3DP, FDM and other
technologies EBM .RTM. EBM .RTM. refers to electron beam melting
(EBM .RTM.), which is a powder-based additive manufacturing
technology. Typically, successive layers of metal powder are
deposited and melted with an electron beam in a vacuum. SLS SLS
refers to selective laser sintering (SLS), which is a powder-based
additive manufacturing technology. Typically, successive layers of
a powder (e.g., polymer, metal, sand, or other material) are
deposited and melted with a scanning laser, for example, a carbon
dioxide laser. SLM SLM refers to selective laser melting .TM.
(SLM), which is a technology similar to SLS; however, with SLM the
powder material is fully melted to form a fully-dense product. SLA
or SL SLA or SL refers to stereolithography (SLA or SL), which is a
liquid-based additive manufacturing technology. Typically,
successive layers of a liquid resin are exposed to a curing, for
example, with UV laser light, to solidify each layer and bond it to
the layer below. This technology typically requires the additional
and removal of support structures when creating particular
geometries. DMLS DMLS refers to direct metal laser sintering
(DMLS), which is a powder-based additive manufacturing technology.
Typically, metal powder is deposited and melted locally using a
fiber optic laser. Complex and highly accurate geometries can be
produced with this technology. This technology supports
net-shaping, which means that the product generated from the
technology requires little or no subsequent surface finishing. LC
LC refers to LaserCusing .RTM.(LC), which is a powder-based
additive manufacturing technology. LC is similar to DMLS; however,
with LC a high-energy laser is used to completely melt the powder,
thereby creating a fully- dense product. 3DP 3DP refers to
three-dimensional printing (3DP), which is a high-speed additive
manufacturing technology that can deposit various types of
materials in powder, liquid, or granular form in a printer-like
fashion. Deposited layers can be cured layer by layer or,
alternatively, for granular deposition, an intervening adhesive
step can be used to secure layered granules together in bed of
granules and the multiple layers subsequently can be cured
together, for example, with laser or light curing. LENS LENS .RTM.
refers to Laser Engineered Net Shaping .TM. (LENS .RTM.), which is
a powder-based additive manufacturing technology. Typically, a
metal powder is supplied to the focus of the laser beam at a
deposition head. The laser beam melts the powder as it is applied,
in raster fashion. The process continues layer by and layer and
requires no subsequent curing. This technology supports
net-shaping, which means that the product generated from the
technology requires little or no subsequent surface finishing. FDM
FDM refers to fused deposition modeling .TM. (FDM) is an
extrusion-based additive manufacturing technology. Typically, beads
of heated extruded polymers are deposited row by row and layer by
layer. The beads harden as the extruded polymer cools.
[0026] Patient-specific and/or patient-engineered implants can be
produced using 3-dimensional printing technology (also known as
Solid Freeform Fabrication or "SFF") to create solid, physical
implant components from an electronic or computerized data file
(e.g., a CAD file). 3D printing techniques such as Selective Laser
Sintering (SLS), EBM (Electron Beam Melting) and Selective Laser
Melting (SLM--also known as Direct Metal Laser Sintering--DMLS--or
LaserCusing) can allow the creation of durable metallic objects
that are biocompatible and can directly serve as implant
components.
[0027] In certain embodiments, an implant can include components
and/or implant component parts produced via various methods. For
example, in certain embodiments for a knee implant, the knee
implant can include a metal femoral implant component produced by
casting or by an additive manufacturing technique and having a
patient-specific femoral intercondylar distance; a tibial component
cut from a blank and machined to be patient-specific for the
perimeter of the patient's cut tibia; and a tibial insert having a
standard lock and a top surface that is patient-specific for at
least the patient's intercondylar distance between the tibial
insert dishes to accommodate the patient-specific femoral
intercondylar distance of the femoral implant.
[0028] As another example, in certain embodiments a knee implant
can include a metal femoral implant component produced by casting
or by an additive manufacturing technique that is patient-specific
with respect to a particular patient's M-L dimension and standard
with respect to the patient's femoral intercondylar distance; a
tibial component cut from a blank and machined to be
patient-specific for the perimeter of the patient's cut tibia; and
a tibial insert having a standard lock and a top surface that
includes a standard intercondylar distance between the tibial
insert dishes to accommodate the standard femoral intercondylar
distance of the femoral implant.
[0029] The steps of designing an implant component and associated
methods of SFF manufacturing such objects using additive material
technologies such as SLS, SLM, EBM and/or SLS, as described herein,
can include both configuring one or more features, measurements,
and/or dimensions of the implant (e.g., derived from
patient-specific data from a particular patient and adapted for the
particular patient), manufacturing and finishing the implant. In
certain embodiments, manufacturing can include making the implant
component from starting materials, for example, metals and/or
polymers or other materials in solid (e.g., powders or blocks) or
liquid form
[0030] In various embodiments, the design of an implant component
or other manufactured object may be altered or modified to
accommodate advantages and/or limitations of a specific
manufacturing process, such as DMLS or SLM, which may result in
differing designs for a single anatomical situation (i.e., for a
single patient anatomy) based on differing manufacturing methods.
The various design changes, which can (but not necessarily must)
have varying degrees of impact on the ultimate performance and/or
reliability of the implant, can be incorporated to accommodate a
wide variety of considerations, including tolerancing and
dimensioning limitations of specific manufacturing methodologies
and/or equipment, design limitations and/or object feature (e.g.,
surface and/or subsurface feature) orientation and/or shape
requirements.
SLM Manufacturing
[0031] FIG. 1 depicts a schematic view of equipment and the process
used in a typical SLM manufacturing process. SLM is a powder bed 8
process that begins with the deposition of a thin layer of powder
onto a substrate 30, which can be disposed on a processing table
11. A high power laser 6 scans the surface of the powder,
generating heat that causes the powder particles to melt (see
melted powder 7) and form a melt pool which solidifies as a
consolidated layer of material. Once the layer has been scanned and
relevant portions melted/solidified, another layer of powder is
deposited, which is then subsequently scanned and melted/solidified
to form the next layer of the part. This process continues with
multiple layers 13 until enough layers of material have been
deposited/melted/solidified to create a desired object 9. Powder
particles that are not melted remain loose and are removed (and can
typically be reused) once the component is complete.
[0032] In various additional embodiments, SLM manufacturing
processes can be employed in the design and/or manufacture of
implant components having intentional "defects" or frangible
features, deformable regions and/or other planned internal/external
attributes that facilitate the revision and/or removal of implant
components and/or portions thereof during primary and/or revision
surgical procedures. Such implants can include planned areas of
increased porosity and/or localized lines of weakness that present
reduced resistance to surgical cutting, drilling, impaction and/or
other tools, as well as implant portions that facilitate
modification, deformation, bending and/or work-hardening (and
subsequent fracture, if desired) of various component features
and/or portions thereof. In various embodiments, the planned
features may facilitate the complete and/or partial removal of
implant components, with the partial removal of implant portions
potentially facilitating surgical access to implant pieces still
remaining in contact with and/or secured to the patient's anatomy.
In alternative embodiments, various portions of implant components
may remain permanently anchored and/or otherwise connected to the
patient's anatomy, and may be ignored and/or utilized for
securement of revision implant components.
Creation of Pre-Defined Weakness Regions
[0033] Unlike traditional manufacturing methods such as casting
and/or machining, SFF layer-wise manufacturing techniques provide
an exceptional level of design and manufacturing access to the
internal structure(s) of a manufactured part. Because SFF provides
a significant level of control or "tailoring" of the micro and
macroscopic internal and external structures of manufactured
objects, the techniques of laser track scanning and melt pool
layering can be particularly useful in the manufacture of adaptable
orthopedic implant components. In various embodiments, implant
components manufactured using SFF techniques can include a variety
of internal and external structures, which can be formed in a
single manufacturing operation, if desired. For example, some
portion of an implant component formed using SFF technology could
have a relatively smooth, uniform and continuous external layer,
while incorporating a less continuous or "disrupted" internal
region in selected areas. Depending upon the design of implant
features as well as the location and distribution of disrupted
regions, various portions of the implant may be sensitive or
otherwise susceptible to specific and/or unusual loading
modalities, which could be employed to selectively separate, flex,
bend, fracture and/or otherwise modify portions of the implant.
[0034] The use of rapid prototyping techniques to fabricate both
the implant and disrupted region(s) is advantageous because it
provides the ability to modify internal structural features of the
implant in a desired manner while retaining a smooth, continuous
external surface (where such a surface is desired). Other known
fabrication methods, such as casting, machining and/or
thermoforming, fully surround the implant with a matrix material to
form the shape of the implant, and thus internal structural
features of the implant are generally uniform to the surface of the
implant. The present disclosure provides a designer with the
ability to provide a high level of mechanical support for component
retention (e.g., functional anchor pegs) where peg removal is not
desired, as well as rapid and easy disengagement of the peg from
the implant body if such removal is warranted.
Frangible Links and Removable Guides
[0035] In various embodiments, an adaptable feature could include a
frangible portion or link that facilitates separation of an implant
component portion at a predetermined location. One embodiment of
such a frangible link is shown in FIGS. 2A and 2B, which are
perspective and side plan views, respectively, of a frangible
portion 50 formed in an anchor peg body 60 to allow the peg to be
frangibly separated from the implant body (not shown). The
frangible portion 50 can be formed at various locations along the
peg and/or within the body, but in the embodiment shown the
frangible portion 50 can be located adjacent where the anchor peg
meets the implant body. The frangible portion 50 can include a
central section 70 and an outer wall section 80, which as shown
surrounds the central section 70 and forms a continuous outer
surface with the remainder of the peg body 60. The central section
70 is formed during the SFF manufacturing processes to have a
significantly weaker structure than the surrounding peg material,
including the outer wall section. This central structure, which in
various embodiments could comprise a void, a highly porous
structure, a loosely interconnected structure and/or a cavity
partially or completely filled with virgin powder material (i.e.,
unheated powder material), all of which can be created as a portion
of the peg and/or implant during the SFF manufacturing process. In
one exemplary embodiment, the central structure could be formed
using a SLM layering technique, with the melt pool creating the
outer wall section 80 in a typical manner, and the design plan
causing the control apparatus to avoid laser contact with the
powder in the central structure. In one alternative embodiment, the
outer wall section could the formed using a SLM layering technique
with the laser, and then using significantly less or more laser
energy impacting on the material in the central section, which
could weakly bond the material (less energy) and/or vaporize and
"bubble" the material (more energy), creating a highly porous and
significantly weaker central section.
[0036] Depending upon the material strength as well as the
thickness of the outer wall portion (and somewhat dependent upon
the strength of the central layer), the frangible portion 50 can be
designed and adapted to break when a predetermined force and/or
force vector(s) is/are applied to the peg, thereby allowing at
least a portion of the peg to be separated from the implant body.
In this manner, a portion of the implant can be designed to
fracture and/or bend at a known location and/or under a known force
without requiring alteration of the surface characteristics of the
implant.
[0037] In addition to the various methods of controlling internal
implant structures using SFF techniques described herein, a variety
of physical design techniques could be used to augment the
frangible portion, which could include a reduced diameter region or
thinned region of material formed between the peg and the implant
body. Other configurations for the frangible portion could include
webbing, forming of an annular grooved in an outer surface of the
peg, or other techniques known in the art. In various alternative
embodiments, internal geometric features could be designed into the
central cavity, such as geometry that limits and/or increases notch
sensitivity or weakness/strength of the material, depending upon
the desired outcome.
[0038] A variety of materials, including both plastics and metals,
could be used for the implant and/or the post and/or the frangible
portion, although the frangible portion in various embodiments will
preferably be formed of the same material as the implant body. In
use, the frangible portion can be designed to provide a weak spot
in the anchor peg that allows the anchor peg to be easily separated
from the implant body when a predetermined force is applied
thereto.
[0039] In various alternative embodiments, the frangible portion
could be formed internally within the implant body. For example, in
the embodiment of FIG. 3A, an implant body 100 has been formed
using SFF manufacturing techniques with a frangible portion 110
including a void 115 or other manufactured artifact positioned
adjacent an anchoring peg 120. If removal of the peg 120 is desired
by operating room personnel, the peg 120 can be separated from the
implant body 100 by the application of sufficient force (see FIG.
3B). In various embodiments, the removal of the peg can leave a
relatively smooth implant surface and/or a small depression, with
little or no material projection out of the implant surface to
impede implantation of the non-modified implant (without the peg).
If desired, the void 115 could comprise a porous or other material
that is exposed to the surface of the implant when the peg is
removed. This material could facilitate bony ingrowth or adhesion
of bone cement, if desired. In alternative embodiments, the void
could be used for attachment to the anatomical structures (e.g., as
a securement hole for orthopedic screws, etc.) or as a connection
point for additional implant components.
[0040] In various embodiments, an anchoring peg for a femoral
implant component (or other implant feature) could include a
frangible feature proximate an implant attachment location. The
anchor could comprise a cylindrical protrusion extending from a
bone-facing portion of the implant, which desirably secures within
a bore formed in the underlying anatomical structure, thereby
securing the implant to the bone. Structurally, the anchor could
comprise a cylindrical body, the majority of which comprises a
solid, essentially uniform CrCo formed by a SLM manufacturing
process. However, at a location proximate the implant, at least one
or more layers of the anchor could comprise a generally cylindrical
exterior of relatively solid CrCo encasing a cylindrical internal
portion comprising a generally disrupted material, with the
interior forming a preferred fracture zone. In use, if detachment
of the anchor from the implant is desired for any reason, a
surgical wrench or other device could be used to grasp and rotate
the anchor in a clockwise or counterclockwise direction. The
rotational motion would desirably impart sufficient stress on the
thin cylindrical base region proximate the disrupted interior
portion (with the interior portion desirably providing little or no
resistance to the rotation), thereby allowing the thin outer wall
to fracture and the anchor to detach from the implant. The implant
could then be utilized in the standard manner without the
cylindrical anchor attached.
[0041] In contrast, if use of the implant with the attached anchor
was desired, the combination of the thin cylindrical wall
surrounding the disrupted interior region would desirably provide
sufficient support to withstand any expected flexion and/or
tension/compression forces experience during normal anatomical
loading conditions. By creating a detachable portion that remains
attached during expected loading conditions, but that can be
fractured, removed and/or otherwise modified by application of
unexpected forces at a surgeon's option, various embodiments
described herein grant the surgeon with an unusual degree of
flexibility in accommodating intraoperative modifications to the
surgical procedure and/or implant components.
[0042] In another exemplary embodiment, an implant could include a
removable portion that can be removed and/or otherwise altered to
change the shape and/or size of the implant. For example, a femoral
implant component could include a trochlear plate that extends the
trochlear groove a desired distance towards and/or into the
intercondylar notch. Such a plate structure might be desired to
prevent the natural patella from dislocating and/or dropping into
the intercondylar notch after replacement of one or more femoral
surfaces. However, if intraoperative conditions dictate an
unexpected repair to the patient's patella, an artificial patellar
implant portion may not require and/or desire the presence of the
trochlear plate. In such a case, the plate could be removed by
grasping the plate portion with surgical pliers and rotating the
plate relative to the implant, which desirably fractures and/or
otherwise removes the plate structure without damaging or affecting
any of the external articulating structures of the femoral
implant.
Removable/Bendable Mating Features
[0043] Various embodiments of patient-specific implants described
herein can include adaptable mating features for integrating with
other orthopedic implant components. The adaptable mating features
could include protrusions, flanges, blades, hooks, plates,
openings, depressions and/or other attachment sites that can be
selectively modified and/or removed by a user. In various
embodiments, such features could be integrated into knee and/or hip
implant components, including an acetabular shell for a hip
implant, that could be configured to couple with an augment, flange
cup, mounting member and/or any other suitable orthopedic
attachment, as well as various combinations thereof.
[0044] For example, various embodiments of an adaptable feature
could comprise one or more flanges or mounting members designed and
manufactured via SFF techniques to be permanently fixed to an
implant component. Desirably, the flanges could include "disrupted"
regions comprising frangible portions that allow for selective
detachment between the implant body and a connection region, such
as screw holes or other structures for receiving fasteners. In
various embodiments, the frangible portions could incorporate
reduced cross-sectional areas (in addition to or in place of
deliberate disrupted regions, as described herein) that allow
bending or breaking or cutting of the flange without disturbing the
geometry of the implant body. If desired, selective portions of a
given flange could be similarly designed, to allow removal of a
portion of the flange while leaving a remaining portion of the
flange connected to the implant body. Further, there may be more
than one level of frangibility on a given flange (and/or between
flanges) to compensate for different surgical appliances and
vertical, horizontal and/or radial adjustability of the placement,
as well as to reduce inadvertent fracture of the wrong frangible
link when multiple such links are present. In various embodiments,
the frangible portions could include physical pre-stressing or
otherwise be pretreated to make the frangible portions weaker than
other areas of the mounting members.
[0045] Depending upon the intended application, one or more porous
pieces or surfaces could be designed for a patient-specific implant
and provided on adaptable or bendable mounting members such as
bendable flanges or plates, or any other mounting arrangement. The
mounting arrangement could be modular, attachable, or
integrally-provided. The bendable region(s) could include
"disrupted" regions, as described herein, specifically designed and
structured during SFF formation to allow deformation of the
mounting arrangement. Such bendable regions could include porous or
bony ingrowth surfaces, the locations of which could be modified by
the surgeon in-situ to be positioned proximate to bleeding bone or
other anatomy.
[0046] In various alternative embodiments, adaptable and/or porous
features may be incorporated into an implant to reduce, by a
certain degree, the stiffness and/or rigidity of an implant or
anchoring component while maintaining a desired degree of strength.
Such features may facilitate the intra-operative modification of
implant features (e.g., bending of an anchoring peg in a desired
manner by operating room personnel) as well as potentially reduce
the opportunity for fatigue or "work-hardening" fracture of implant
components or support structures thereof.
Manufacturing Biofunctional and/or Porous Regions
[0047] In various embodiments, SFF manufacture of implant
components (e.g., SLM, SLS, DMLS techniques) can be used to create
biofunctional implant structures and/or surfaces (and/or securement
features), which may be particularized for an individual patient
and/or surgical procedure. Such surfaces can be designed and
utilized to achieve a wide variety of functional objectives, from
creating osteo-inductive and/or osteo-conductive surfaces that
desirably promote bony ingrowth to porous surfaces to promote bone
cement adhesion (as well as relatively smooth surfaces that
desirably inhibit bony and/or soft tissue adhesion). Utilizing SFF
manufacturing to form implant structures with selectively varying
bone ingrowth and/or fixation properties can permit manufacturing
implant features with highly individualized and optimized,
patient-adapted fixation characteristics.
[0048] In various embodiments, exemplary porous coating parameters
that can be varied based on patient-specific information can
include, for example, the locations on/in implant components where
porous coating is used and/or features specific to the coating
itself. For example, in some embodiments, SLM manufacturing can be
used to create an implant feature with a uniform internal
microstructure (to desirably promote implant strength and/or
durability) in combination with a roughened and/or porous surface
structure that, depending upon a variety of manufacturing
parameters, can be particularized for a wide variety of surgical
objectives. For example, an outer implant surface can be created
having an optimal and/or designed pore size for promoting bone
ingrowth in a certain patient population. As another example, an
implant outer surface can be created having a designed pore size
and/or surface roughness for promoting bone cement attachment
and/or adhesion. Where patient-specific information indicates a
preferred microstructure and/or macrostructure for the implant or
portions thereof, implant modeling and SFF fabrication techniques
can be employed to create a unique implant.
[0049] In various embodiments, structures and/or surfaces of an
implant can selectively be porous, roughened, smooth and/or
hardened. As used herein, "porous" can generally be used to
describe any portion of structure having a plurality of holes,
spaces, gaps, channels, etc. therein. In some instances, a porous
portion can consist of a plurality of small discrete particles of
material (e.g., metal) that were bonded together at their points of
contact with each other to define a plurality of connected
interstitial pores. In other embodiments, a porous portion can
consist of an organized lattice, mesh, and/or grid of material
having multiple channels, spaces, and/or pores therein. The
structural nature of a porous portion can be controlled by the
design and/or manufacturing parameters provided to, as well the
capabilities of, the SFF manufacturing equipment and process(es).
In addition to altering physical characteristics by modifying the
structural design and/or process parameters such as scanning speed,
temperature, atmosphere and/or laser power, the various surface
features created by the SLM manufacturing process could be
dependent upon a wide variety of variables, including the grain
size, shape and/or distribution (e.g., uniformity and/or
nonuniformity) of the raw material, which may be particularized for
a specific application and/or implant feature desired.
[0050] In various embodiments, various of the surface features of a
patient-specific implant could be particularized to accommodate a
variety of objectives, including various combinations of the
following: (1) Smooth surfaces; (2) hardened surfaces; (3) porous
surfaces for promoting bone infiltration and/or ingrowth; (4)
roughened and/or porous surfaces for promoting material adhesion
such as bone cement securement; and/or (5) porous surfaces for
containing osteo-inductive agents and/or medicaments.
[0051] In various exemplary embodiments, a tibial implant could
include one or more bone-facing surfaces that include specifically
designed and manufactured porous surface features that promoted
bone in-growth. Such porous features can be created in bone-facing
portions of the implant (e.g., on one or more inner, bone facing
surfaces and/or on the surface of impaction pegs, stems, pins
and/or anchors, etc.) at locations where the intended surgical
procedure is expected to create bleeding bone. At other locations
on the implant, non-porous surface features may be created, such as
along articulating and/or peripheral edge surfaces that are not
expected to encounter bleeding bone and/or where bone ingrowth is
not desired. In still other portions of the implant, if desired,
other surface features may be incorporated, such as smooth and/or
thickened surfaces where FEA or other analysis indicates the
implant may experience increased and/or excessive stresses (e.g.,
thinned implant sections and/or notch sensitive locations, etc.).
Still other portions of the implant may incorporate roughened
and/or porous surfaces to accommodate bone cement and/or
medications, if desired.
[0052] In at least one exemplary embodiment, one or more porous
surfaces or other surface features can be designed into certain
subregions of an implant component that interface with bone. In
various alternative embodiments, such an implant can include some
bone-interfacing subregions, with other subregions designed to mate
with cement or other securement materials, thereby creating a
patient-specific hybrid cemented/porous-coated implant.
[0053] In one alternative embodiment, a patient-specific implant
component could include porous coatings on pegs or other anchor
regions of the implant, with non-porous coatings (and/or coatings
to facilitate securement by bone cement) on other bone-facing
surfaces of the implant. Alternatively, a patient-specific implant
component could include non-porous peg and/or anchor surface, with
porous coatings on other bone-facing surfaces of the implant.
[0054] If desired, an implant can be designed and/or manufactured
to include one or more porous regions that partially and/or
completely extend through portions of the implant body. For
example, a tibial tray may include one or more porous regions of
the implant that extend completely through the tray body (from
caudal to cephalad surfaces of the implant, for example), thereby
allowing bone to grow completely through the implant, if desired.
Such porous regions could be surrounded partially and/or completely
by non-porous regions, such as a non-porous periphery of a tibial
tray surrounding one or more porous regions formed centrally or in
medial and lateral compartments of the tibial tray. If desired,
such embodiments could allow for bone ingrowth completely through
the metallic tray and into contact with a polymer, ceramic and/or
metallic tray insert. In a similar manner, tibial alignment and/or
securement fins could be partially and/or completely porous.
[0055] The inclusion of porous features is similarly contemplated
with other joint implant components. For example, a central pin for
securing a hip resurfacing implant could include one or more porous
sections (or be completely porous), if desired.
[0056] If desired, an articular surface repair system can be
affixed to subchondral bone, with one or more stems, or pegs,
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 to allow bone in-growth. In addition,
the stems can be porous coated for bone in-growth.
[0057] In various embodiments, the adaptive features described
herein can be applied to implant components for use with any joint
including, without limitation, a spine, spinal articulations, an
intervertebral disk, a facet joint, a shoulder, an elbow, a wrist,
a hand, a finger, a hip, a knee, an ankle, a foot, or a toe joint.
Furthermore, various embodiments described herein can encompass
and/or apply to the design, selection and/or manufacture of
standard and/or modular implants and/or implant components, if such
are appropriate to a given patient's anatomy, as well as associated
guide tools.
Improved Revisability
[0058] In various alternative embodiments, SLM manufacturing
techniques can be employed to design and manufacture implant
components having adaptable features that desirably improve and/or
simplify a surgeon's ability to perform a subsequent revision
surgery. Revision of an implant component may be indicated for a
host of reasons, including implant fracture and/or failure,
excessive wear, infection and/or excessive pain. In many revision
cases, however, portions of an implant requiring revision may still
remain anchored or otherwise secured to underlying portions of the
patient's anatomy. In extreme cases, the removal of an implant
component may necessitate significant resection of the patient's
anatomy, which leaves significantly less of the native anatomical
structures remaining for fixation of the revision component(s).
[0059] Traditionally, an implant component that was partially
and/or fully-secured to the underlying anatomy (but which needed to
be removed for some reason) could be difficult to separate from the
patient's anatomy. In the case of a tibial tray implant having a
centrally secured post, it might be necessary for a surgeon to cut
around the existing implant or otherwise position instrumentation
around the implant to loosen it from the surrounding bone and/or
other anatomy prior to removal. In some instances, especially where
the tray included a tibial keel or other rotation-resistant
structures, it could be difficult to cut around the keel or
otherwise access various areas of the bone-implant interface to
loosen the implant. It might be particularly difficult to access
certain areas of the implant depending upon the chosen access type
and/or path(s). For example, if a medial/lateral surgical access
path were chosen, the keel structure could impede access to
posterior/lateral portions of the bone-implant interface.
Accordingly, a surgeon might need to remove a significant amount of
bone to separate the implant from the tibia, as well as remove
significant bone to facilitate access to inner portions of the
implant and/or surrounding the central post (see FIGS. 10A through
10C, for example). These difficulties would be exacerbated by the
lack of access to such support structures, which necessitated
significant bone removal for access to underlying structures,
especially where the implant attachment was well secured. Moreover,
where complete separation between the implant and the underlying
bone was unsuccessful, subsequent removal of the implant could
involve considerable force and/or inadvertently and undesirably
fracture additional portions of the remaining anatomy.
[0060] To address various concerns, including those previously
described, in various embodiments implant components can be
designed and manufactured with features that facilitate revision of
the component(s), should a subsequent revision of the implant
become necessary. In various embodiments, implant features can
include frangible and/or deformable sections that desirably
withstand normal loading, but which are especially susceptible to
specific loading modalities and/or modification by surgical tools,
allowing portions and/or the entirety of the implant to be
"released" and/or removed with little or no need for resection,
modification and/or damage to the patient's underlying native
anatomy. In various embodiments, the implant component can be
provided with guiding features that facilitate the use of surgical
tools to release portions of the implant, including the use of
guide tools or jigs that incorporate implant-specific and/or
anatomy-specific surfaces (of combinations thereof) to guide
surgical tools.
[0061] In one exemplary embodiment shown in FIG. 4, a tibial
implant component 150 can include a centrally-located anchoring peg
160a secured to a bone-facing side 170 of the implant. The peg
could comprise a generally cylindrical body made of powdered and
laser-melted CrCo, which can be produced using a SLM manufacturing
method as previously described (e.g., as part of the implant
manufacturing process via SLM). All or at least a portion of the
peg can comprise a porous structure, as discussed herein, to
facilitation bone ingrowth and fixation. Additionally or
alternatively, a base portion 175 of the anchoring peg proximate
the implant surface can include an adaptable feature that may
include a region of significantly increased porosity (which may or
may not extend to the surface of the peg, at the designer's option)
and/or a significantly reduced material strength. Desirably, the
base portion 175 does not appreciably affect the strength or
durability of the peg as an anchoring feature (or at least does not
reduce peg strength below an acceptable minimal functional level to
properly function as an implant anchor), but the porous region will
significantly reduce the resistance of the peg base to cutting
tools such as vibratory saws and/or drills.
[0062] Similarly, in some embodiments, a tibial implant component
150 can be manufactured with a peg 160b formed, at least in part,
of a lattice structure, as shown in FIG. 11. The lattice structure
can comprise a plurality of organized individual filaments with
openings between parallel filaments. The lattice structure can form
a general outer periphery configured in, for example, a cylindrical
shape, similar to that of peg 160a. As with other porous structures
described herein, the openings in the lattice structure can provide
for bone ingrowth. Furthermore, in some embodiments, the structure
of the lattice (including, e.g., the filament width, spacing
between filaments, angle of filaments, interconnections between
filaments) can be designed, engineered, and/or otherwise optimized
to patient-specific and/or design parameters. In some embodiments,
a lattice structure, as opposed to other porous structures, may be
advantageous for providing a desired strength or durability of the
peg as an anchoring feature (or at least does not reduce peg
strength below an acceptable minimal functional level to properly
function as an implant anchor), while utilizing individual
filaments of relatively small diameter. Such a configuration, with
small diameter filament may permit a substantial amount of bone
ingrowth between individual filaments, thereby enhancing fixation.
And furthermore, the small diameter of individual filaments may
particularly facilitate detachment of the tibial tray from the peg
during a revision surgery. For example, at a time when the peg must
be cut from the tray, a saw or other cutting tool may be applied
with, e.g., only the force needed to cut a single filament at a
time, in order to cut through the lattice structure of the peg.
This amount of force to cut through a single filament may be
substantially smaller than, for example, the amount of force
required to cut through a peg of comparable diameter that is formed
of a solid (or possibly other porous) structure.
[0063] In various embodiments, pegs 160a,b can easily be separated
from the tibial implant by advancing a saw or drill along the
bone-facing surface of the implant (in a region between the native
bone and the bone-facing side of the implant) and cutting the base
of the peg at the porous region (see FIG. 5A). Once the peg has
been severed, the implant can be removed from the femur (see FIG.
5B). Depending upon the surgical objectives as well as the revision
implant components to be used, the pegs may be removed (e.g., using
a coring drill 180 or other surgical tools well known in the
art--see FIGS. 5C through 5E), or the peg can remain within the
anatomy, with a subsequent revision implant covering, "capping" or
otherwise reattaching to some or all of the peg, if desired.
[0064] In various alternative embodiments, a plurality of pegs
could be used to anchor an implant to a targeted anatomical region,
with one or more of the anchoring pegs including a weakened section
that facilitates removal of the implant from bone, as previously
described. For example, FIG. 6 depicts a tibial tray implant 200
having a plurality of anchoring pegs extending from a lower,
bone-facing surface for securement to a tibial surface (not shown).
The anchoring pegs can include a centrally-located porous peg 210
that provides for bony ingrowth and/or cement fixation, and
peripherally placed pegs 220 which can comprise press-fit or other
attachment arrangements. This arrangement will desirably provide
significantly more short-term and long-term fixation for the
implant as compared to an implant having only a single anchoring
peg and/or single type of fixation (i.e., only one of press-fit,
cement fixation and/or bone ingrowth, for example). To separate
this implant from the surrounding anatomy, the surgeon may elect to
tunnel under the implant (as previously described) and avoid and/or
sever the peripheral pegs (at the surgeon's option), and
subsequently sever or fracture the centrally-located peg 210.
Desirably, the central peg 210 can be easily fractured and/or cut,
as it desirably comprises a porous and/or weakened structure, as
previously described. The peripheral pegs may be of a smaller size
and thus more easily broken or severed, or if not severed, the
peripheral pegs may be easily withdrawn from the tibia if natural
tissues and/or cement have not adhered to these relatively smoother
peripheral pegs. Once the implant has been removed, the central peg
210 may remain within the tibia, or it may be removed as previously
described.
[0065] FIG. 7 depicts an alternative embodiment which includes a
tibial tray 250 having a composite anchoring peg 260 that
incorporates a solid proximal portion 265 and a porous distal
portion 270. Also includes are one or more wings 275 that can
desirably provide rotational stability to the tray 250, as known in
the art. In use, the composite anchoring peg 260 can be inserted in
a known manner, with the proximal portion 265 of the peg providing
a press-fit securement, and the distal portion 270 desirably
allowing for bony ingrowth. If revision of the tray 250 is desired,
a surgical tool can be inserted into and through a patient's soft
tissues 280 and tibial bone 285 from a lateral aspect, and the
anchoring peg 260 can be severed at a location proximate a boundary
between the proximal portion 265 and the distal portion 270 (see
FIG. 8A). This desirably will release the tray 250 from the
securely anchored porous distal portion 270, and allow the tray 250
to be withdrawn from the tibia (see FIG. 8B). If desired, the
distal portion may remain permanently within the bone, or if may be
removed using a coring drill or other tool (see FIG. 8C).
[0066] By facilitating the severing and/or fracture of anchoring
elements in a less-invasive manner, the disclosed embodiments
provide for removal of relevant implant components and/or anchor
portions in a least-invasive manner, thereby preserving
significantly more bone and/or other anatomical support structures
for the subsequent revision procedure. Moreover, depending upon the
chosen revision implant components and procedure, one or more
residual anchoring components still secured to the bone may be used
to provide additional fixation for the revision components.
[0067] In various embodiments, the implant component can include
guiding features that facilitate the use of surgical tools in
accessing various adaptable features. For example, a bone facing
and/or peripheral edge of the implant could include markings and/or
protrusions/indentations that facilitate and/or guide the
advancement of a surgical cutting tool. Because the anchoring pegs
can be located in various locations, and because such implants are
often difficult and/or impossible to accurately visualize using
x-rays or other non-invasive methods, the inclusion of such
markings and/or guiding features can significantly improve the
ability of the surgeon to accurately access the pegs, as well as
significantly reduce unnecessary damage to the surrounding
anatomy.
[0068] In various alternative embodiments, a guide tool or jig may
be provided that includes guiding features and/or implant-specific
surfaces that conform to various implant surfaces (and/or
protrusions/indentations on the implant surface) and/or native
anatomical features that desirably guide surgical tools into
contact with the relevant adaptable structures. Such guiding
features and implant-specific surfaces may be designed using
implant data saved from a prior surgery, or such data may be
constructed using patient-specific image data, if available.
[0069] For example, a guide tool 300 as depicted in FIG. 9A can
include a patient-specific surface 310 that desirably conforms to
one or more exposed surfaces 315 of an implant 320. The guide tool
300 can include one or more alignment apertures 330 which provide
for the controlled insertion and advancement on one or more cutting
tools along a specific trajectory, which in this embodiment
intersects an implant anchoring post 340 at a location proximate a
solid/porous interface 350 (see FIG. 9B).
Internal Voids
[0070] In various alternative embodiments, an implant component can
include features such as internal voids and/or cavities that
facilitate surgical removal and/or subsequent use. For example, SLM
manufacturing techniques can be utilized to create an implant
component with anchoring pegs having internal voids or other
features that facilitate their subsequent removal if necessary.
Such features can include a central bore region formed in a
cylindrical anchoring peg that, when the peg is separated from the
implant (such as, for example, as previously described herein), the
resected surface of the peg exposes a central bore which can be
utilized to remove the peg from the surrounding bony anatomy. If
desired, a drill or other surgical tool can be advanced into the
bore, and attached to a slap hammer or other device which is
employed in a known manner to remove the peg. In various
alternative embodiments, the exposed central bore of the peg could
be utilized to anchor a subsequent implant, if desired.
Improved Visualization
[0071] In various embodiments, adaptable features such as SFF
manufactured voids and/or porous areas of lower material density
can be employed to improve and/or facilitate non-invasive
visualization (e.g., x-ray imaging or other techniques) of implant
structures and/or bone interface regions (e.g., lucent lines, bone
ingrowth, etc.) for a variety of reasons, including the detection
of implant fatigue, fracture and/or loosening of implant components
from the underlying bony anatomy. In various embodiments, the
features may act as "windows" to facilitate the visualization of
lucent lines or other anatomical/implant features.
FEA Analysis
[0072] Various embodiments disclosed herein will desirably include
a FEA or other analysis of relevant implant datasets, which
optionally may include analyses of material property information
particular to the type of manufacturing processes as well as the
design and/or orientation of the implant (as oriented and
positioned in the intended build plan). Such an analysis can occur
immediately prior to SLM manufacture (e.g., FEA analysis of each
object in the build plan, with relevant manufacturing and
orientation data, can be evaluated) or the analysis may be
conducted on some subset thereof at any point in the evaluation and
virtual packing process. The FEA analysis will desirably identify
and/or highlight one or more locations of high stress and/or areas
of localized implant weakness, including those that may be
particular to the type of manufacturing processes as well as the
design and orientation of the implant. Where FEA analysis of a part
design and/or orientation identifies one or more undesired regions
of potential weakness and/or failure, it may be desirous to
reposition and/or reorient the object in the build plan (and/or may
necessitate modifying the implant design and/or build plan in some
manner). Moreover, FEA analysis may be employed to ensure that one
or more adaptable features (such as those described herein) have
been properly designed to accommodate implant modification (e.g.,
fracture and/or bending) by surgical personnel.
[0073] The maximum principal stress observed in FEA analysis can be
used to establish an acceptable minimum implant thickness for an
implant component having a particular size and, optionally, for a
particular patient (e.g., having a particular weight, age, activity
level, etc). In certain embodiments, an implant component design or
selection can depend, at least in part, on a threshold minimum
implant component thickness. In turn, the threshold minimum implant
component thickness can depend, at least in part, on
patient-specific data, such as condylar width, femoral
transepicondylar axis length, and/or the patient's specific weight.
In this way, the threshold implant thickness, and/or any implant
component feature, can be adapted to a particular patient based on
a combination of patient-specific geometric data and on
patient-specific anthropometric data. This approach can apply to
any implant component feature for any joint, for example, the knee,
the hip, or the shoulder.
[0074] In various embodiments, the design of a given implant
component and/or various features therein can be further assessed
and/or modified by including FEA modeling and/analysis, either
alone or in combination with information relating to the specific
manufacturing method chosen for creating the implant. For example,
the creation of an implant using SLM manufacturing methods may
produce an implant having differing density, porosity, durability,
fatigue strength and/or other material properties than those of an
implant created through traditional casting techniques. A finite
element analysis (FEA) of an SLM implant and/or intended implant
design may identify areas of the implant/design prone to increased
and/or excessive loads, which may induce the designer to modify the
design to better accommodate the anticipated loading (e.g.,
increase the local or global implant thickness and/or alter implant
geometry or location of planar surfaces). If desired, such an FEA
analysis may identify areas of concern that may impel a redesign of
the implant to alleviate strength, durability and/or adaptability
concerns.
[0075] In a similar manner, an FEA analysis may identify areas of
one or more build objects that could benefit from some modification
of the intended manufacturing process at one or more times part-way
through the manufacturing process (e.g., "cross-hatching" or
remelting an individual portion of a melt layer to reduce/avoid the
formation of interconnected porosity and/or buckling deformation in
a localized manner), and then continuing the layer deposition and
laser melting process to complete the implant manufacture. If
desired, the material properties (and/or potentially one or more
component materials) of an implant can be varied to accommodate
unique or localized requirements. For example, it may be desirable
for the porosity and/or tensile strength/elasticity of a material
in a femoral implant component to vary along the surface or
cross-sectional profile of the implant. In a similar manner, it may
be desirous for a surface of such an implant to possess differing
mechanical properties than subsurface portions of the implant.
Likewise, it may be desirous for a periphery of such an implant to
possess differing mechanical properties than central portions of
the implant. In such a case, it may be advantageous to alter the
material properties of such an implant in some manner, such as by
altering the laser speed, power, duration and/or remelting one or
melt layers (or portions thereof such as, for example, implant
surfaces portions only) to accommodate the varying demands placed
upon the implant. Alternatively, the implant may comprise various
materials that are adhered, layered or otherwise arranged in some
fashion, including the use of multiple types of materials and/or
material properties in non-aligned layers (e.g., a composite-like
layering materials), to accomplish various objectives of various
embodiments disclosed herein.
[0076] In a similar manner, implants comprising metals, plastics
and/or ceramic constituents may be formed of two or more materials,
or may comprise a single material with sections or portions having
varying material characteristics (e.g., by radiation, heating,
cooling, hipping, annealing, chemical action, work hardening,
peening, carburizing, hardening, surface treating, oxidation, etc.)
For example, the medial and/or lateral and/or superior and/or
inferior portions of a tibial tray inset may be formed from two or
more materials adhered or otherwise connected in some manner, each
material having a unique material property, resulting in an implant
with differing mechanical properties on its medial and/or lateral
and/or superior and/or inferior sides. Such an implant could
alternatively comprise a multi-layered material, with different
materials and/or material properties exposed on the surface during
a subsequent machining process (with the processing tools extending
to differing depths), thereby resulting in a generally uniform
layered material with different surface properties on the surface
of its medial and lateral sides.
Materials
[0077] Any material known in the art can be used for any of the
implant systems and component described in the foregoing
embodiments, for example including, but not limited to metal,
metallic powders, metal alloys, combinations of metals, ceramics,
plastic, polyethylene, cross-linked polyethylene's or polymers or
plastics, pyrolytic carbon, nanotubes and carbons, as well as
biologic materials.
[0078] In various exemplary embodiments, the DMLS/SLM raw material
can comprise a CrCo powder having an average particle size of
between 34 and 54 microns, although larger and/or smaller particles
may be used with varying degrees of utility (as well as the use of
differing size particles in creating a single implant component).
In various embodiments, the deposed particle layer may be
approximately 60 microns thick which, when melted, consolidated and
cooled, can create a solid structural layer of approximately 20
microns thickness.
[0079] Any fixation techniques and combinations thereof known in
the art can be used for any of the implant systems and component
described in the foregoing embodiments, for example including, but
not limited to cementing techniques, porous coating of at least
portions of an implant component, press fit techniques of at least
a portion of an implant, ingrowth techniques, etc.
INCORPORATION BY REFERENCE
[0080] The entire disclosure of each of the publications, patent
documents, and other references referred to herein is incorporated
herein by reference in its entirety for all purposes to the same
extent as if each individual source were individually denoted as
being incorporated by reference.
* * * * *
References