U.S. patent application number 12/620309 was filed with the patent office on 2010-03-18 for system and method for joint resurface repair.
This patent application is currently assigned to ARTHROSURFACE INCORPARATED. Invention is credited to Steven W. Ek.
Application Number | 20100070045 12/620309 |
Document ID | / |
Family ID | 33425681 |
Filed Date | 2010-03-18 |
United States Patent
Application |
20100070045 |
Kind Code |
A1 |
Ek; Steven W. |
March 18, 2010 |
System and Method for Joint Resurface Repair
Abstract
An implant for installation into a portion of an articular
surface includes a protrusion configured to cover an un-excised
portion of articular surface proximate to the implant. Another
implant may form a cavity to allow the un-excised portion of
articular surface to remodel over a perimeter edge of the implant.
The implant may also include indentations such as grooves to
promote articular cartilage remodeling over a portion of the load
bearing surface of the implant. An elongated or non-round implant
is also provided having two opposing concentric arcuate shaped
sides, as well as a method to seat such an implant in an articular
surface. A method for seating an implant without cutting articular
cartilage is also provided.
Inventors: |
Ek; Steven W.; (Bolton,
MA) |
Correspondence
Address: |
GROSSMAN, TUCKER, PERREAULT & PFLEGER, PLLC
55 SOUTH COMMERICAL STREET
MANCHESTER
NH
03101
US
|
Assignee: |
ARTHROSURFACE INCORPARATED
Franklin
MA
|
Family ID: |
33425681 |
Appl. No.: |
12/620309 |
Filed: |
November 17, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10760965 |
Jan 20, 2004 |
7618462 |
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12620309 |
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10162533 |
Jun 4, 2002 |
6679917 |
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10760965 |
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10024077 |
Dec 17, 2001 |
6610067 |
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10162533 |
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09846657 |
May 1, 2001 |
6520964 |
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10024077 |
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60201049 |
May 1, 2000 |
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Current U.S.
Class: |
623/20.14 ;
606/80 |
Current CPC
Class: |
A61B 2017/0445 20130101;
A61F 2002/30448 20130101; A61F 2002/30772 20130101; A61F 2/4618
20130101; A61F 2002/30433 20130101; A61B 2017/0404 20130101; A61B
17/0401 20130101; A61F 2/38 20130101; A61F 2220/005 20130101; A61B
17/7098 20130101; A61B 17/1615 20130101; A61F 2210/0071 20130101;
A61B 17/1675 20130101; A61F 2002/30354 20130101; A61F 2310/00029
20130101; A61B 2090/061 20160201; A61B 17/1637 20130101; A61F
2002/30451 20130101; A61F 2002/30719 20130101; A61F 2002/4661
20130101; A61F 2220/0041 20130101; A61F 2220/0058 20130101; A61F
2230/0017 20130101; A61B 2017/00464 20130101; A61B 5/4528 20130101;
A61F 2/3859 20130101; A61F 2002/30896 20130101; A61F 2310/00095
20130101; A61B 2017/045 20130101; A61F 2/4603 20130101; A61B 17/888
20130101; A61F 2002/30069 20130101; A61F 2002/30878 20130101; A61F
2002/30831 20130101; A61F 2002/30299 20130101; A61F 2002/30892
20130101; A61B 17/8695 20130101; A61B 2017/0409 20130101; A61F
2002/30113 20130101; A61B 17/1635 20130101; A61B 2017/044 20130101;
A61F 2002/30604 20130101; A61F 2002/4663 20130101; A61F 2310/00239
20130101; A61F 2002/30143 20130101; A61F 2230/0006 20130101; A61B
17/1642 20130101; A61F 2002/30858 20130101; A61B 90/06 20160201;
A61F 2002/4681 20130101; A61F 2310/00089 20130101; A61F 2310/00203
20130101; A61B 17/8894 20130101; A61F 2002/4635 20130101; A61F
2002/30563 20130101; A61F 2002/30871 20130101; A61F 2310/00059
20130101; A61F 2220/0033 20130101; A61F 2002/30873 20130101; A61F
2230/0093 20130101; A61F 2310/00023 20130101; A61B 2017/00238
20130101; A61B 17/1764 20130101; A61F 2002/30957 20130101; A61F
2002/4662 20130101; A61F 2002/30332 20130101; A61F 2/30756
20130101; A61F 2002/30948 20130101; A61B 17/863 20130101; A61F
2002/30225 20130101; A61F 2310/00796 20130101; A61F 2/30767
20130101; A61B 17/8625 20130101; A61F 2/4657 20130101; A61F
2002/30943 20130101; A61F 2/30942 20130101; A61B 17/0487 20130101;
A61B 17/8615 20130101; A61F 2310/00017 20130101; A61F 2250/0036
20130101; A61F 2002/30952 20130101; A61B 2017/0448 20130101; A61B
17/06166 20130101; A61F 2002/30324 20130101; A61F 2002/30065
20130101; A61F 2002/30879 20130101; A61F 2002/4658 20130101; A61F
2230/0069 20130101; A61F 2250/0092 20130101 |
Class at
Publication: |
623/20.14 ;
606/80 |
International
Class: |
A61F 2/38 20060101
A61F002/38; A61B 17/00 20060101 A61B017/00 |
Claims
1. An implant comprising: a bone-facing distal surface; and a
proximal surface; wherein said bone-facing distal surface and said
proximal surface define an outer perimeter comprising at least two
arcuate sections each having a concentric arcuate shape with a
common center and a first and a second generally opposing side
section extending generally along a length of said implant between
said at least two arcuate shaped sections, wherein said outer
perimeter has a truncated circular shape.
2. The implant of claim 1, wherein said truncated circular shape
comprises a circular shape truncated on two opposed sides.
3. The implant of claim 1, further comprising a protrusion
extending around at least a portion of said implant, said
protrusion configured to cover an un-excised portion of an
articular surface proximate said implant.
4. The implant of claim 1, wherein said implant further comprises:
a width extending between said two opposing side sections and
through said common center; and a length extending between said two
arcuate sections and through said common center; wherein said width
is less than said length.
5. The implant of claim 4, wherein said width extends along a
medial-lateral (ML) curvature of said implant and said length
extends along an anterior-posterior (AP) curvature of said
implant.
6. A system comprising: a reamer configured to remove a portion of
a patient's articular surface in an area proximate to a defect site
to form an excision site, said reamer comprising a blade portion
configured to create a circular cutting projection when rotated
about a longitudinal axis of said reamer, said circular cutting
projection having a diameter greater than a width of said patient's
articular surface in said portion to be removed; and an implant
comprising: a bone-facing distal surface; and a proximal surface;
wherein said bone-facing distal surface and said proximal surface
define an outer perimeter comprising at least two arcuate sections
each having a concentric arcuate shape with a common center and a
first and a second generally opposing side section extending
generally along a length of said implant between said at least two
arcuate shaped sections, wherein said outer perimeter has a
truncated circular shape.
7. The system of claim 6, wherein said bone-facing distal surface
is configured to match with said excision site.
8. The system of claim 7, wherein said outer perimeter of said
implant corresponds to a perimeter of said excision site.
9. The system of claim 6, further comprising a guide pin having a
length configured to extend generally perpendicular to said
articular surface proximate said defect site, said guide pin
defining a working axis along said length of said guide pin.
10. The system of claim 9, wherein said reamer is configured to
translate along working axis of said guide pin.
11. The system of claim 6, wherein said implant further comprises a
screw configured to engage bone beneath said removed articular
surface along said working axis.
12. The system of claim 6, wherein said reamer comprises a
generally circular blade portion.
13. The system of claim 12, wherein said reamer comprises a shaft
extending along said longitudinal axis of said reamer, wherein said
generally circular blade portion extends generally radially
outwardly from said shaft.
14. The system of claim 12, wherein said generally circular blade
portion is rotated about said shaft.
15. The system of claim 6, wherein said reamer comprises: a shaft
extending along said longitudinal axis of said reamer; and a
cutting blade extending generally radially outwardly from said
shaft arm.
16. The system of claim 15, wherein said cutting blade comprises an
offset
17. The system of claim 16, wherein said bone-facing distal surface
of said implant includes a non-planar contour and wherein said
offset arm of said cutting blade comprises a non-planar cutting
surface configured to create said excision site including a base
portion having a non-planar contour generally matching said
non-planar contour of bone-facing distal surface of said
implant.
18. An implant for installation into an excision site formed within
a patient's articular surface, said implant comprising: a
bone-facing distal surface having a non-planar contour configured
to match with a non-planar base portion of said excision site; a
screw extending generally outwardly from bone-facing distal
surface, said screw configured to secure said implant within said
excision site; a proximal surface having a contour based on an
original surface contour of said excised portion of said articular
surface; and an outer perimeter comprising at least two arcuate
sections each having a concentric arcuate shape with a common
center and a first and a second generally opposing side section
extending generally along a length of said implant between said at
least two arcuate shaped sections, wherein said outer perimeter has
a truncated circular shape.
19. The implant of claim 18, wherein said truncated circular shape
comprises a circular shape truncated on two opposed sides.
20. The implant of claim 18, wherein said implant further
comprises: a width extending between said two opposing side
sections and through said common center, said width extending along
a medial-lateral (ML) curvature of said implant; and a length
extending between said two arcuate sections and through said common
center, said length extending along a anterior-posterior (AP)
curvature of said implant; wherein said width is less than said
length.
Description
[0001] This application is a continuation application under 37 CFR
.sctn.1.53(b) of U.S. application Ser. No. 10/760,965 filed Jan.
20, 2004, now U.S. Pat. No. 7,618,462, which is a continuation of
U.S. application Ser. No. 10/162,533 filed Jun. 4, 2002, now U.S.
Pat. No. 6,679,917, which is a continuation-in-part application of
U.S. application Ser. No. 10/024,077, filed Dec. 17, 2001, now U.S.
Pat. No. 6,610,067 which is itself a CIP application of U.S.
application Ser. No. 09/846,657, filed May 1, 2001, now U.S. Pat.
No. 6,520,964 which claims the benefit of U.S. provisional
application Ser. No. 60/201,049, filed May 1, 2000, all of which
are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] This invention relates to devices and methods for the repair
of defects that occur in articular cartilage on the surface of
bones, particularly the knee.
BACKGROUND OF THE INVENTION
[0003] Articular cartilage, found at the ends of articulating bone
in the body, is typically composed of hyaline cartilage, which has
many unique properties that allow it to function effectively as a
smooth and lubricious load-bearing surface. However, when injured,
hyaline cartilage cells are not typically replaced by new hyaline
cartilage cells. Healing is dependent upon the occurrence of
bleeding from the underlying bone and formation of scar or
reparative cartilage called fibrocartilage. While similar,
fibrocartilage does not possess the same unique aspects of native
hyaline cartilage and tends to be far less durable.
[0004] Hyaline cartilage problems, particularly in knee and hip
joints, are generally caused by disease such as occurs with
rheumatoid arthritis or wear and tear (osteoarthritis), or
secondary to an injury, either acute (sudden), or recurrent and
chronic (ongoing). Such cartilage disease or deterioration can
compromise the articular surface causing pain and further
deterioration of joint function. As a result, various methods have
been developed to treat and repair damaged or destroyed articular
cartilage.
[0005] For smaller defects, traditional options for this type of
problem include non-operative therapies (e.g., oral medication or
medication by injection into the joint), or performing a surgical
procedure called abrasion arthroplasty or abrasion chondralplasty.
The principle behind this procedure is to attempt to stimulate
natural healing. At the defect site, the bone surface is abraded,
removing approximately 1 mm. or less using a high-speed rotary bun
or shaving device. This creates an exposed subchondral bone bed
that will bleed and will initiate a fibrocartilage healing
response. Although this procedure has been widely used over the
past two decades and can provide good short term results, (1-3
years), the resulting fibrocartilage surface is seldom able to
support long-term weight bearing, particularly in high-activity
patients, and is prone to wear.
[0006] Another procedure, referred to as the "microfracture"
technique, incorporates similar concepts of creating exposed
subchondral bone. During the procedure, the cartilage layer of the
chondral defect is removed. Several pathways or "microfractures"
are created to the subchondral bleeding bone bed by impacting a
metal pick or surgical awl at a minimum number of locations within
the lesion. By establishing bleeding in the lesion and by creating
a pathway to the subchondral bone, a fibrocartilage healing
response is initiated, forming a replacement surface. Results for
this technique are generally similar to abrasion
chondralplasty.
[0007] Another known option to treat damaged articular cartilage is
a cartilage transplant, referred to as a Mosaicplasty or
osteoarticular transfer system (OATS) technique. This involves
using a series of dowel cutting instruments to harvest a plug of
articular cartilage and subchondral bone from a donor site, which
can then be implanted into a core made into the defect site. By
repeating this process, transferring a series of plugs, and by
placing them in close proximity to one another, in mosaic-like
fashion, a new grafted hyaline cartilage surface can be
established. The result is a hyaline-like surface interposed with a
fibrocartilage healing response between each graft.
[0008] This procedure is technically difficult, as all grafts must
be taken with the axis of the harvesting coring drill being kept
perpendicular to the articular surface at the point of harvest.
Also, all graft placement sites must be drilled with the axis of a
similar coring tool being kept perpendicular to the articular
surface at the point of implantation. Further, all grafts must be
placed so that the articular surface portion of these cartilage and
bone plugs is delivered to the implantation site and seated at the
same level as the surrounding articular surface. If these plugs are
not properly placed in relation to the surrounding articular
surface, the procedure can have a very detrimental effect on the
mating articular surface. If the plugs are placed too far below the
level of the surrounding articular surface, no benefit from the
procedure will be gained. Further, based on the requirement of
perpendicularity on all harvesting and placement sites, the
procedure requires many access and approach angles that typically
require an open field surgical procedure. Finally, this procedure
requires a lengthy post-operative non-weight bearing course.
[0009] Transplantation of previously harvested hyaline cartilage
cells from the same patient has been utilized in recent years.
After the cartilage is removed or harvested, it is cultured in the
lab to obtain an increase in the number of cells. These cells are
later injected back into the focal defect site and retained by
sewing a patch of perio steal tissue over the top of the defect to
contain the cells while they heal and mature. The disadvantages of
this procedure are its enormous expense, technical complexity, and
the need for an open knee surgery. Further, this technique is still
considered somewhat experimental and long-term results are unknown.
Some early studies have concluded that this approach offers no
significant improvement in outcomes over traditional abrasion and
microfracture techniques.
[0010] U.S. Pat. No. 5,782,835 to Hart et al. discloses an
apparatus and method for repair of articular cartilage including a
bone plug removal tool, and a bone plug emplacement tool. The
method of repairing defective articular cartilage includes the
steps of removing the defective cartilage and forming a hole of
sufficient depth at the site. A bone plug comprising intact bone
and cartilage adhering thereto is removed from a bone lacking
defective cartilage is placed in the hole at the site of the
damage.
[0011] U.S. Pat. No. 5,413,608 to Keller discloses a knee joint
endoprosthesis for replacing the articular surfaces of the tibia
comprising a bearing part which is anchored on the bone having an
upper bearing surface and a rotatable plateau secured on the
bearing surface and forming a part of the articular surface to be
replaced. A journal rises from the bearing surface and cooperates
with a bore in the plateau to provide lateral support.
[0012] U.S. Pat. No. 5,632,745 to Schwartz describes a method of
surgically implanting into a site a bio-absorbable cartilage repair
assembly. The assembly includes a bio-absorbable polygonal T-shaped
delivery unit having radial ribs to be mounted in the removed area
and a porous bio-absorbable insert supported by and in the delivery
unit. The method comprises the steps of preparing the site to
receive the assembly by removing a portion of the damaged cartilage
and preparing the site to receive the assembly by drilling and
countersinking the bone. The assembly is inserted and seated using
an impactor in the drilled and countersunk hole in the bone until
the assembly is flush with the surrounding articular surface.
[0013] U.S. Pat. No. 5,683,466 to Vitale illustrates an articular
joint surface replacement system having two opposing components.
Each component has a tapered head piece for covering the end of a
bone and for acting as an articular surface, an integrally formed
screw stem of sufficient length to extend into the bone and
inwardly angled bone grips on the underside of the head piece to
allow fixation to the bone by compression fit. The partially
spherical convex shaped exterior of the first component complements
the partially spherical concave shaped exterior of the second
component.
[0014] U.S. Pat. No. 5,702,401 to Shaffer discloses an
intra-articular measuring device including a hollow handle defining
a first passageway and a hollow tube having a second passageway
extending from the handle, the hollow tube carrying a projection at
its distal end for seating on a fixed site and a probe disposed at
the distal end of the hollow tube which may be directed to a second
site, to enable measurement of the distance between the first and
second sites.
[0015] U.S. Pat. No. 5,771,310 to Vannah describes a method of
mapping the three-dimensional topography of the surface of an
object by generating digital data points at a plurality of sample
points on said surface, each digital data point including a
property value and a position value corresponding to a particular
point representing the properties of the surface of the object. A
3-D transducer probe (e.g., a digitizer) is moved on or over the
surface along a random path, and the sample points are digitized to
generate a real-time topography or map on a computer screen of
selected properties of the object, including without limitation,
surface elevation, indentation stiffness, elevation of sub-surface
layers and temperature.
[0016] Prosthetics for total knee replacement (TKR), whereby the
entire knee joint or a single compartment of the knee joint is
replaced can be a common eventuality for the patient with a large
focal defect. Although these patients are also managed with
anti-inflammatory medications, eventual erosion of the remaining
articular cartilage results in effusion, pain, and loss of mobility
and/or activity for the patient. Problems encountered after
implanting such prostheses are usually caused by the eventual
loosening of the prosthetic due to osteolysis, wear, or
deterioration of the cements used to attach the device to the host
bones. Further, some prostheses used are actually much larger than
the degenerated tissue that needs to be replaced, so that extensive
portions of healthy bone are typically removed to accommodate the
prostheses. Patients who undergo TKR often face a long and
difficult rehabilitation period, and the life span of the TKR is
accepted to be approximately 20 years. Accordingly, efforts are
made to forgo the TKR procedure for as long as possible.
[0017] Accordingly, there is a need for an improved joint surface
replacement system that would be effective in restoring a smooth
and continuous articular surface and that would also be as durable
as the former hyaline cartilage surface, within the context of a
minimally invasive procedure that allows for a nearly immediate
return to activity, restoration of lifestyle, and pain relief.
SUMMARY OF THE INVENTION
[0018] An implant consistent with the invention for installation
into a portion of an articular surface includes: a bone-facing
distal surface; a proximal surface; and a protrusion formed by an
extension of the bone-facing distal surface and the proximal
surface.
[0019] Another implant consistent with the invention for
installation into a portion of an articular surface includes: a
bone-facing distal surface configured to mate with an implant site
created by excising a portion of the articular surface; a proximal
surface having a contour based on an original surface contour of
the excised portion of the articular surface; and a cavity
configured to allow an un-excised portion of the articular surface
proximate to the implant to remodel over a perimeter edge of the
proximal surface.
[0020] Another implant consistent with the invention for
installation into a portion of an articular surface having an
anterior portion, a posterior portion, a medial portion and a
lateral portion includes: a bone-facing distal surface configured
to mate with an implant site created by excising a portion of the
articular surface; and a proximal surface having a contour based on
an original surface contour of the excised portion of the articular
surface, and at least two side surfaces each having a concentric
arcuate shape with a common center, wherein the implant has an
elongate arcuate geometric shape.
[0021] A method for replacing a portion of an articular surface of
bone consistent with the invention includes: establishing a working
axis substantially normal to an articular surface of bone; excising
a portion of the articular surface adjacent to the axis, thereby
creating an implant site, the implant site having a first and
second opposing arcuate shaped sides; and installing an implant to
the implant site.
[0022] Another method of replacing a portion of an articular
surface of bone consistent with the invention includes: locating an
existing defect in the articular surface; establishing a working
axis substantially normal to the articular surface and
substantially centered with the existing defect; excising a portion
of the articular surface adjacent to the axis, thereby creating an
implant site; and installing an implant in the implant site,
wherein at least a portion of the existing defect is exposed around
a perimeter of the implant.
[0023] Another implant for installation into a portion of an
articular surface consistent with the invention includes: a
bone-facing distal surface configured to mate with an implant site
created by excising a portion of the articular surface; a proximal
surface having a contour based on an original surface contour of
the excised portion of the articular surface; at least one arcuate
shaped side surface configured to abut an edge of the excised
portion of the articular surface, the arcuate shaped side surface
having a radial extension configured to cover an un-excised portion
of the articular surface proximate to the implant.
[0024] Another method for replacing a portion of an articular
surface of bone consistent with the invention includes:
establishing a working axis substantially normal to an articular
surface of bone, the articular surface having a medial side and
lateral side defining a width of the articular surface; excising a
portion of the articular surface adjacent to the axis, thereby
creating an implant site, wherein the excising is performed using a
cutting tool that rotates about the axis, the cutting tool having a
circular blade portion, the circular blade portion having a
diameter greater than the width of the articular surface; and
installing an implant to the implant site.
[0025] Another implant consistent with the invention for
installation into a portion of an articular surface includes: a
bone-facing distal surface configured to mate with an implant site
created by excising a portion of the articular surface; and a
proximal surface having a contour based on an original surface
contour of the excised portion of the articular surface, wherein
the proximal surface has at least one indentation formed in the
proximal surface configured to promote remodeling of articular
cartilage over a portion of the proximal surface of the implant
once seated.
DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a fragmentary side view of a knee having therein
an exemplary assembled fixation device and implant of the joint
surface repair system surgically implanted by the method in one
embodiment of the present invention;
[0027] FIG. 2a is an exploded side view of an exemplary fixation
screw and hex-shaped proximal extension in one embodiment of the
present invention;
[0028] FIG. 2b is an exploded perspective view of an exemplary
fixation screw and hex-shaped proximal extension in one embodiment
of the present invention;
[0029] FIG. 3a is a side view of an exemplary assembled fixation
screw and hex shaped extension in one embodiment of the present
invention;
[0030] FIG. 3b is an exploded perspective view of another exemplary
fixation screw and implant in one embodiment of the present
invention;
[0031] FIG. 4a is a perspective view of the upper surface of an
exemplary implant in one embodiment of the present invention;
[0032] FIG. 4b is a side view of an exemplary implant in one
embodiment of the present invention;
[0033] FIG. 4c is a perspective view of the lower surface of an
exemplary implant in one embodiment of the present invention;
[0034] FIG. 5a is a side view of an exemplary assembled fixation
device and implant in one embodiment of the present invention;
[0035] FIG. 5b is a perspective view of an assembled fixation
device and implant in one embodiment of the present invention;
[0036] FIG. 5c is a perspective view of the upper surface of an
exemplary implant, in one embodiment of the present invention;
[0037] FIG. 5d is a perspective view of the lower surface of an
exemplary implant, in one embodiment of the present invention;
[0038] FIG. 6a is a sectional view of a knee having damaged
articular cartilage, showing an exemplary guide pin drilled into
the central portion of the defect and an arthroscope being disposed
adjacent thereto, in a surgical procedure consistent with one
embodiment of the present invention;
[0039] FIG. 6b is a side view of the distal tip of an exemplary
drill device for boring a pilot hole to receive an exemplary
fixation screw, in one embodiment of the present invention;
[0040] FIG. 7a is a sectional view of a knee having damaged
articular cartilage, showing an exemplary fixation screw being
driven into the defect by an exemplary socket type driver arranged
on the guide pin, in a surgical procedure consistent with one
embodiment of the present invention;
[0041] FIG. 7b is a side view of the exemplary fixation screw,
socket type driver and guide pin of FIG. 7a, illustrating the hex
shaped proximal extension in a cross-sectional view, in a surgical
procedure consistent with one embodiment of the present
invention;
[0042] FIG. 8a is a perspective view of a knee having damaged
articular cartilage, showing an exemplary fixation screw and
hex-shaped proximal extension implanted in the defect after removal
of an exemplary socket type driver and guide pin, in a surgical
procedure consistent with one embodiment of the present
invention;
[0043] FIG. 8b is a sagital view of the exemplary fixation screw
and hex-shaped proximal extension of FIG. 8a implanted in the
defect after removal of an exemplary socket type driver and guide
pin, in a surgical procedure consistent with one embodiment of the
present invention;
[0044] FIG. 8c is a perspective view of an exemplary fixation
screw, proximal extension and cover, in one embodiment of the
present invention;
[0045] FIG. 9a is a sectional view of an exemplary fixation screw
and hex-shaped proximal extension implanted in the defect with the
exemplary guide pin replaced and an exemplary measuring tool
arranged thereon, in a surgical procedure consistent with one
embodiment of the present invention;
[0046] FIG. 9b is a side partial cross-sectional view of the
exemplary fixation screw and hex-shaped proximal extension of FIG.
9a implanted in the defect with the exemplary guide pin replaced
and an exemplary measuring tool arranged thereon, in a surgical
procedure consistent with one embodiment of the present
invention;
[0047] FIG. 9c is a perspective view of an exemplary fixation screw
and proximal extension, with the cover removed, in one embodiment
of the present invention;
[0048] FIG. 10a is a sectional view of an exemplary fixation screw
and hex-shaped proximal extension implanted in the defect, after
removal of the hex-shaped proximal extension, with an exemplary pin
and suture strands placed therethrough, in a surgical procedure
consistent with one embodiment of the present invention;
[0049] FIG. 10b is a side partial cross-sectional view of the
exemplary fixation screw and hex-shaped proximal extension of FIG.
10a, implanted in the defect, with an exemplary pin and suture
strands placed therethrough, in a surgical procedure consistent
with one embodiment of the present invention;
[0050] FIG. 11a is a sectional view of an exemplary fixation screw
implanted in the defect, with an exemplary pin and suture strands
placed therethrough, showing the implanted fixation screw with the
implant being tensioned on the suture strands, in a surgical
procedure consistent with one embodiment of the present
invention;
[0051] FIG. 11b is a partial cross-sectional view of the exemplary
fixation screw of FIG. 9a implanted in the defect, showing the
implant positioned in the interchondular notch, in a surgical
procedure consistent with one embodiment of the present
invention;
[0052] FIG. 12 is a sectional view of an exemplary fixation screw
implanted in the defect, wherein, after placement of the implant
and removal of the suture strands, the implant is driven into place
with an impactor and hammer, in a surgical procedure consistent
with one embodiment of the present invention;
[0053] FIG. 13 is a side cross-sectional view of an exemplary
fixation screw implanted in the defect, after placement of the
implant, wherein, after removal of the impactor and hammer, cement
is injected between the implant and the bone, in a surgical
procedure consistent with one embodiment of the present
invention;
[0054] FIG. 14a is a schematic representation of the two datum
curves used to define a patient-specific three-dimensional surface
for construction of the articular or lower surface of an implant in
one embodiment of the present invention;
[0055] FIG. 14b is a top view of an exemplary hex-shaped proximal
extension in one embodiment of the present invention;
[0056] FIG. 14c is a perspective view of the bone-contacting or
upper surface of an exemplary implant, in one embodiment of the
present invention;
[0057] FIG. 15a is a perspective view of an exemplary compass
instrument, in one embodiment of the present invention;
[0058] FIG. 15b is a perspective view of the distal offset arm of
an exemplary compass instrument and cutting blade to be mounted
thereon, in one embodiment of the present invention;
[0059] FIG. 15c is a perspective view of an exemplary driver,
showing an exemplary implant on an exemplary tether element, in one
embodiment of the present invention;
[0060] FIG. 15d is a perspective view of an exemplary driver,
showing an exemplary implant tensioned on an exemplary tether
element, in one embodiment of the present invention;
[0061] FIG. 16 is a perspective view of an exemplary compass
instrument and cutting blade mounted on an exemplary guide pin, in
one embodiment of the present invention;
[0062] FIG. 17a is a perspective view of another exemplary cutting
blade, in one embodiment of the present invention;
[0063] FIG. 17b is a perspective view of an exemplary measuring
probe, in one embodiment of the present invention;
[0064] FIG. 17c is a perspective view of an exemplary multi-faced
blade mounted in the distal offset arm of an exemplary compass
instrument, in one embodiment of the present invention;
[0065] FIG. 18a is a perspective view of an exemplary site
preparation and cutting device, in one embodiment of the present
invention;
[0066] FIG. 18b is a cross sectional view of the exemplary site
preparation and cutting device of FIG. 18a, in one embodiment of
the present invention;
[0067] FIG. 18c is a perspective view of another exemplary site
preparation and cutting device, in one embodiment of the present
invention;
[0068] FIG. 18d is a side view of another exemplary site
preparation and cutting device, in one embodiment of the present
invention;
[0069] FIG. 18e is a perspective view of another exemplary site
preparation and cutting device, in one embodiment of the present
invention;
[0070] FIG. 19a is a sectional view of the upper surface of an
exemplary implant, in one embodiment of the present invention;
[0071] FIG. 19b is a side view of a portion of the exemplary
implant of FIG. 19a, in one embodiment of the present
invention;
[0072] FIG. 19c is a perspective view of the upper surface of the
exemplary implant of FIG. 19a, in one embodiment of the present
invention;
[0073] FIG. 19d is an exploded perspective view of another
exemplary implant with taper lock ring, washer and suture, in one
embodiment of the present invention;
[0074] FIG. 19e is a top perspective view of the exemplary implant
of FIG. 19d seated in the taper lock ring, in one embodiment of the
present invention;
[0075] FIG. 19f is a bottom perspective view of the exemplary
implant of FIG. 19d seated in the taper lock ring, with washer and
suture, disposed within an incision near the defect site, in one
embodiment of the present invention;
[0076] FIG. 19g is a perspective view of the exemplary implant of
FIG. 19d seated in the taper lock ring, with washer and suture,
wherein the suture is threaded through an aperture at the distal
end of a seating tool, at a first point in time during the process
of seating the implant into the defect site, in one embodiment of
the present invention;
[0077] FIG. 19h is another perspective view of the exemplary
implant of FIG. 19d seated in the taper lock ring, with washer and
suture, wherein the suture is threaded through an aperture at the
distal end of a seating tool, at a second point in time during the
process of seating the implant into the defect site, in one
embodiment of the present invention;
[0078] FIG. 19i is another perspective view of the exemplary
implant of FIG. 19d seated in the taper lock ring, wherein the
distal end of a seating tool is disposed onto the implant, at a
third point in time during the process of seating the implant into
the defect site, in one embodiment of the present invention;
[0079] FIG. 20a is a perspective view of an exemplary inner
recording element of an exemplary measuring device, in one
embodiment of the present invention;
[0080] FIG. 20b is a perspective view of an exemplary outer marking
element of an exemplary measuring device, in one embodiment of the
present invention;
[0081] FIG. 20c is a cross-sectional perspective view of an
exemplary measuring device showing an exemplary inner recording
element and an exemplary outer marking element, in one embodiment
of the present invention;
[0082] FIG. 20d is an exploded perspective view of another
exemplary measuring device, in one embodiment of the present
invention;
[0083] FIG. 20e is a perspective view of the exemplary measuring
device of FIG. 20d, illustrating an exemplary scroll alignment
feature, in one embodiment of the present invention;
[0084] FIGS. 20f and 20g are side views of the exemplary measuring
device of FIG. 20d illustrating the translational motion of the
handle with respect to the tip of the device, in one embodiment of
the present invention;
[0085] FIG. 20h is a perspective view of the distal end of the
exemplary measuring device of
[0086] FIG. 20d, in one embodiment of the present invention;
[0087] FIG. 20i is a perspective view of the distal end of the
exemplary measuring device of FIG. 20d with outer element, disposed
upon the inner element engaging a mating feature of the screw, in
one embodiment of the present invention;
[0088] FIG. 21 is a perspective view of an exemplary unitary
implant, in one embodiment of the present invention;
[0089] FIG. 22 is a perspective view of a defect site with a keyed
aperture for receiving the exemplary unitary implant of FIG. 21, in
one embodiment of the present invention;
[0090] FIG. 23 is a perspective view of an exemplary composite
implant, in one embodiment of the present invention;
[0091] FIG. 24 is a perspective view of another exemplary composite
implant, in one embodiment of the present invention;
[0092] FIG. 25 is a perspective view of an exemplary implant
illustrating the geometry of said implant for use in an algorithm
for establishing minimum implant thickness, in one embodiment of
the invention;
[0093] FIG. 26 is a perspective view of an exemplary implant
illustrating the geometry of said implant for use in an algorithm
for establishing minimum implant thickness, in one embodiment of
the invention;
[0094] FIG. 27a is a perspective view of an exemplary drill guide
device in an exemplary generic bone implant embodiment of the
present invention;
[0095] FIG. 27b is a perspective view of another exemplary drill
guide device in an exemplary generic bone implant embodiment of the
present invention;
[0096] FIG. 28a is a top sectional view of the anterior-posterior
plane of an articulating surface in an exemplary generic bone
implant embodiment of the present invention;
[0097] FIG. 28b is a side sectional view of the medial-lateral
plane of an articulating surface in an exemplary generic bone
implant embodiment of the present invention;
[0098] FIG. 29 is a perspective view of the use of an exemplary
drill guide in an exemplary generic bone implant embodiment of the
present invention, as the drill guide is brought up to a lesion
site of the articulating surface;
[0099] FIG. 30 is a perspective view of the use of an exemplary
drill guide in an exemplary generic bone implant embodiment of the
present invention, as the drill guide is seated into position and a
guide pin is driven through the drill guide;
[0100] FIG. 31 is a perspective view of the articulating surface in
an exemplary generic bone implant embodiment of the present
invention, as a bone drill is passed over the guide pin to create a
pilot hole for the screw;
[0101] FIG. 32 is a cross-sectional view of the articulating
surface in an exemplary generic bone implant embodiment of the
present invention, as the screw is driven into the pilot hole with
a cap positioned into the screw;
[0102] FIG. 33 is a cross-sectional view of the articulating
surface in an exemplary generic bone implant embodiment of the
present invention, as the cap is removed and a rod is inserted into
the screw, and the guide is positioned back over the rod and
returned to its position in contact with the articular surface;
[0103] FIG. 34 is a side perspective view of the articulating
surface in an exemplary generic bone implant embodiment of the
present invention, as the guide is used to take a depth measurement
needed for implant geometry;
[0104] FIG. 35 is a top perspective view of the lower surface of an
exemplary implant in an exemplary generic bone implant embodiment
of the present invention;
[0105] FIG. 36 is a side perspective view of an exemplary implant
in an exemplary generic bone implant embodiment of the present
invention;
[0106] FIG. 37 is a side perspective view of another exemplary
implant in an exemplary generic bone implant embodiment of the
present invention;
[0107] FIG. 38 is a perspective view of the articulating surface in
an exemplary generic bone implant embodiment of the present
invention, as the implant site is reamed with a cutting/reaming
tool in preparation for receiving an implant;
[0108] FIG. 39 is a top perspective view of an alternative
exemplary cutting/reaming tool in an exemplary generic bone implant
embodiment of the present invention,
[0109] FIG. 40 is a side perspective view of an exemplary cleaning
tool for cleaning the female taper of the screw prior to delivery
of the implant, in an exemplary generic bone implant embodiment of
the present invention;
[0110] FIG. 41 is a side perspective view of an exemplary suction
tool for holding and delivering the implant, in an exemplary
generic bone implant embodiment of the present invention;
[0111] FIG. 42 is a side perspective view of an exemplary suction
tool holding an implant in place, in an exemplary generic bone
implant embodiment of the present invention;
[0112] FIG. 43 is a side cross-sectional view of an exemplary
suction tool holding an implant in place, with an implant in place,
in an exemplary generic bone implant embodiment of the present
invention;
[0113] FIG. 44 is a top perspective view of the articulating
surface in an exemplary generic bone implant embodiment of the
present invention, with the implant driven into its final
position;
[0114] FIG. 45 is a side perspective view of an exemplary
removal/revision tool in an exemplary generic bone implant
embodiment of the present invention;
[0115] FIG. 46 is a side perspective view of an exemplary
removal/revision tool, with an implant in place, in an exemplary
generic bone implant embodiment of the present invention;
[0116] FIG. 47 illustrates an exemplary alternatively-keyed
embodiment of the screw and the exemplary alternatively-keyed
implant to which it is adapted to mate, in an exemplary embodiment
of the present invention;
[0117] FIG. 48 illustrates a side cross-sectional view of an
exemplary alternatively-keyed embodiment of the screw, in an
exemplary embodiment of the present invention;
[0118] FIG. 49 illustrates a side perspective view of the articular
surface of a lesion site and an exemplary biaxial measuring tool
for developing an axis normal to the articular surface, in one
embodiment of the present invention
[0119] FIG. 50 illustrates another side perspective view of the
articular surface of a lesion site and an exemplary biaxial
measuring tool for developing an axis normal to the articular
surface, in one embodiment of the present invention;
[0120] FIG. 51 illustrates a side exploded view of an exemplary
biaxial measuring tool, in one embodiment of the present
invention;
[0121] FIG. 52 illustrates a top perspective view of the distal end
of an exemplary biaxial measuring tool in a first position, in one
embodiment of the present invention;
[0122] FIG. 53 illustrates a top perspective view of the distal end
of an exemplary biaxial measuring tool in a second position, in one
embodiment of the present invention;
[0123] FIG. 54 illustrates an exemplary digital measuring system in
one embodiment of the present invention;
[0124] FIG. 55 illustrates an exploded perspective view of an
exemplary handpiece in an exemplary digital measuring system in one
embodiment of the present invention;
[0125] FIG. 55a illustrates a top perspective cutaway view of an
exemplary printed linear index strip passing through an exemplary
linear head for reading, in an exemplary handpiece in an exemplary
digital measuring system in one embodiment of the present
invention;
[0126] FIG. 55b illustrates a top perspective cutaway view of an
exemplary printed rotary index strip passing through an exemplary
rotary head for reading, in an exemplary handpiece in an exemplary
digital measuring system in one embodiment of the present
invention;
[0127] FIG. 55c illustrates an exemplary linear index strip in an
exemplary handpiece in an exemplary digital measuring system in one
embodiment of the present invention;
[0128] FIG. 55d illustrates an exemplary rotary index strip in an
exemplary handpiece in an exemplary digital measuring system in one
embodiment of the present invention;
[0129] FIG. 56a illustrates a side perspective view of an exemplary
handpiece with the probe assembly removed, in an exemplary digital
measuring system in one embodiment of the present invention;
[0130] FIG. 56b illustrates a side perspective view of an exemplary
handpiece, including the probe assembly, in an exemplary digital
measuring system in one embodiment of the present invention;
[0131] FIG. 57 illustrates a top perspective view of an assembled
exemplary handpiece, in an exemplary digital measuring system in
one embodiment of the present invention;
[0132] FIG. 58 illustrates a side perspective view of an assembled
exemplary handpiece, in an exemplary digital measuring system in
one embodiment of the present invention;
[0133] FIG. 59 illustrates a top cross-sectional view of an
assembled exemplary handpiece, in an exemplary digital measuring
system in one embodiment of the present invention;
[0134] FIG. 60 illustrates a side cross-sectional view of an
assembled exemplary handpiece, in an exemplary digital measuring
system in one embodiment of the present invention;
[0135] FIG. 61 illustrates a side cutaway perspective view of an
exemplary base unit, in an exemplary digital measuring system in
one embodiment of the present invention;
[0136] FIG. 62A is a top perspective view an alternative exemplary
embodiment of a substantially round implant having a
protrusion;
[0137] FIG. 62B is a cross sectional view of the implant of FIG.
62A taken along the line B-B of FIG. 62A;
[0138] FIG. 62C is a side perspective view of the implant of FIG.
62A;
[0139] FIG. 63A is a side perspective view of another implant
embodiment consistent with the invention having protuberances;
[0140] FIG. 63B is a cross sectional view of the implant of FIG.
63A taken along the line B-B of FIG. 63A;
[0141] FIG. 64A is an alternative embodiment of an implant having a
cavity to allow an unexcised portion of articular surface proximate
to the implant to grow over the perimeter edge of the implant;
[0142] FIG. 64B is a cross sectional view of the implant of FIG.
64A taken along the line B-B of FIG. 64A;
[0143] FIG. 65A is another alterative embodiment of an elongated
implant consistent with the invention;
[0144] FIG. 65B is a perspective view of an implant site and a
reaming tool for preparing the implant site to accept the implant
of FIG. 65A;
[0145] FIG. 65C is a cross sectional view of the bottom surface of
the implant site of FIG. 65B;
[0146] FIG. 65D is a perspective view of the implant of FIG. 65A
being seated or placed into the implant site of FIG. 65B;
[0147] FIG. 66A is a top perspective view of alternative elongated
implant embodiment having protrusions for covering proximate
portions of un-excised articular surface when the implant is
seated;
[0148] FIG. 66B is a top perspective view of the implant of FIG.
66A being seated or placed into a matching implant site;
[0149] FIG. 67 is a perspective view of an implant being seated
into an existing defect without cutting the borders of the
defect;
[0150] FIG. 68A is a top perspective view of an implant having
grooves to promote remodeling of articular cartilage over a
proximal surface of the implant;
[0151] FIG. 68B is a cross sectional view of the implant of FIG.
68A;
[0152] FIG. 68C is a perspective view of a portion of the perimeter
edge of the implant of FIG. 68A illustrating particular edge
geometry to also promote remodeling of articular cartilage over a
proximal surface of the implant; and
[0153] FIG. 68D is a top perspective view of the implant of FIG.
68A seated in an articular surface illustrating the remodeling of
articular cartilage over a portion of the proximal surface of the
implant.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0154] As an overview, FIG. 1 shows a surgically implanted
articular joint surface repair system consistent with the present
invention. As shown, the assembled fixation device includes
fixation screw 10, implant 40, and anchoring pin 5, implanted in
the defect in the medial femoral chondral surface 55 of knee 50.
Implant 40 is configured so that bearing or bottom surface 41 of
the implant reproduces the anatomic contours of the surrounding
articular surface of the knee 50.
[0155] As illustrated in FIGS. 2a, 2b and 3a, fixation screw 10
comprises threads 12 running the length of the screw from tapered
distal tip 11 to hex-shaped drive 15. In the embodiment shown, the
screw includes a tapered distal end 11, and aggressive distal
threads 12, so that, as screw 10 is driven into the subchondral
bone 100 (as shown in FIG. 7a) the screw dilates open and radially
compress the subchondral bone, increasing its local density and
thereby increasing the fixation strength of the screw. The screw 10
may taper down to the distal end 11, and the diameter of the screw
may become greater and more uniform at the center thereof, so that
adjustment of the depth of the screw 10 with respect to the
subchondral bone 100 does not significantly further increase or
decrease the compression of the subchondral bone.
[0156] One or more milled slots 13 run the length of the uniform
diameter portion of the screw 10. Slots 13 ensure that as healing
or tissue in-growth begins, migrational or rotational movement of
the screw is inhibited. The screw 10 is configured to be driven by
a female or socket type driver 2 as shown in FIG. 7b, which engages
a hex-shaped drive 15 located toward the proximal end 17 of the
screw. A cylindrical proximal extension 14 (which may,
alternatively, be a recess 303 which mates with a plug or other
protrusion on the implant surface, as shown in FIG. 8c) extends
from hex-shaped drive 15, which eventually serves as a fixation
element for surface prosthetic implant 40. Through hole 16 runs
through the central axis of the screw. Hex-shaped cover 30 (which
may, alternatively, be a plug 301, for mating with a fixation
element 302 having a recess, as shown, e.g., in FIGS. 3b, 8c, and
9c, and described in the following paragraph) is configured to
engage the cylindrical proximal extension 14 of the screw 10 to
prevent exposure of the cylindrical extension from inadvertent
contact or damage. The hex-shaped cover 30 is finished with a
radiused proximal end 31 that assists in the visual determination
of the correct depth setting of the screw. Through hole 32 in the
hex-shaped cover 30 corresponds with through hole 16 in the
fixation screw 10.
[0157] Alternatively, as shown in FIGS. 3b, 8c, and 9c, the
female-shaped cover may instead be a plug 301 having a male-shaped
mating component 305, for mating with a fixation element 302 of a
screw 10' having a recess 303. Additionally, the shape of the cover
and plug, or other recessed, protruding, or mating components may
be other than hexagonal, and those in the art will recognize that
one of any number of shapes or configurations for such components
may be employed in a device or method consistent with the
invention.
[0158] Also, while many of the components described herein are
cannulated, having guide apertures, through holes, and/or central
lumina along their length, for disposing such components about a
guide rod for proper location of the components with respect to the
articular surface, it should be recognized that a suture 313 or
other flexible element, or other guide feature may be used in place
of a guide rod, or a guide rod or wire may be eliminated altogether
from one or more steps consistent with the invention described
herein. As shown in FIG. 8c, the suture 313 may be fixedly or
removably attached to the plug 301.
[0159] As shown in FIGS. 4a, 4b and 4c, implant 40 comprises lower
bearing surface 41, top surface 42 and protrusion 45 located
centrally on the bottom surface. As the top surface 42 of the
implant 40 is not a bearing surface, and instead is fixed into
subchondral bone 100, a series of stepped machine cuts 43 following
the contours of the defect are created. By creating stepped machine
cuts 43 a contoured contact surface matching the defect in the
subchondral bone 100 is created. This contact surface results in an
increased surface area that should enhance resistance to loosening
of the implant 40 via rotational or translational loading. In the
illustrated embodiment, the stepped cuts are shown as square
cross-section cuts, but the cuts may be circular, triangular, or
another configuration.
[0160] In order to secure the implant 40 to the fixation screw 10,
precision taper 44 is machined into or onto a protrusion 45 on the
top surface 42 of the implant. The precision taper 44 is configured
to engage the cylindrical proximal extension 14 of the screw 10,
once the hex-shaped cover 30 has been removed therefrom. Taper 44
may be mated with extension 14 so that a friction fit is provided
between these surfaces. The assembled fixation device is shown in
FIGS. 5a and 5b. Alternatively, other engagement mechanisms such as
snap-fits, press-fits, threads, or coupling elements, for example,
may also be used. In one embodiment, leading pin 47 arranged on the
protrusion 45 assists penetration into subchondral bone. Also, in
one embodiment, guide aperture 46 passes through the top 42 and
bottom 41 surfaces of the implant 40, just slightly off center of
the reference axis 20A. Alternatively, guide aperture 46 may be
located in the center of the implant 40 and corresponds to through
hole 16 running through the central lumen in the fixation screw 10.
Bone cement may be injected through guide aperture 46 on the
surface of the implant 40 and through hole 16 in the fixation screw
10, to enhance the contact surface between the device and the
subchondral bone. In one embodiment, the implant is constructed of
cobalt chromium, although other materials may be used, including
implantable plastics. Additionally, biologically active coatings or
surface treatments (e.g., to enhance bone ingrowth or improve wear
properties) may be utilized or combined as laminates, particularly
with respect to the bearing surfaces and bone contacting surfaces.
Further exemplary materials that may be used in fabricating an
implant consistent with the invention are described
hereinbelow.
[0161] As shown in FIG. 3b, it is noted that precision taper 44 may
be a male-shaped component 304 instead of the above-described
female component 44. In this configuration, the male-shaped
component 304 of the implant 40' is configured for mating with a
fixation element 302 of the screw 10' having a recess 303 adapted
to receive the male-shaped component 304.
[0162] By way of example, FIGS. 6a-13 depict one exemplary joint
surface methodology of the present invention. FIG. 6a shows a focal
defect 1 of the articular surface 55 of the femoral chondyle bone
of the knee 50. This defect is identified by arthroscope 25
inserted in the area of the defect 1 during a diagnostic
arthroscopy or surgical arthroscopy. The disclosed surgical
intervention begins by drilling a guide pin 20 defining reference
axis 20A into the central portion of the defect 1 via an incision
200 typical of arthroscopic procedures. Placement of this pin may
be done using visual, freehand techniques, or may be located
centrally by using outer element 71 of a measuring tool 70 (as
shown in FIGS. 9a and 9b), or other aiming device or technique, to
define a center. This reference axis 20A serves to establish a
working axis located central to the defect 1 for the procedures
that follow, and arthroscope 25 may be used to view the joint for
purposes of establishing a reference axis 20A generally
perpendicular to and bisecting the existing articular surface 55
defined by radii 60 and 61, as shown in FIG. 8b. Referring to FIGS.
7a, 7b, 8a and 8b, fixation screw 10 and hex-shaped cover 30 are
driven into the defect 1 in the subchondral bone 100 by socket-type
driver 2 mounted over (i.e., about) guide pin 20 located on
reference axis 20A. Under arthroscopic view, the depth of fixation
screw 10 may be adjusted by driver 2 so that the bottom of the
radiused surface 31 of the hex-shaped cover 30 is positioned
tangent to the radii 60 and 61 that define the existing articular
surface 55. The guide pin 20 is removed and the knee 50 is
articulated through its range of motion to ensure that the height
of the radiused surface 31 of the hex-shaped cover 30 is proper,
since the prosthetic surface 41 of the implant 40 is created also
to be tangent to this radiused surface 31. The depth positioning of
the radiused surface 31 of the hex-shaped cover 30 establishes a
point of origin or a reference point for all future measuring and
machining operations. Arthroscopic examination may be carried out
from multiple arthroscopic views to confirm positioning.
[0163] A drill mechanism 306, as illustrated in FIG. 6b, may be
used to bore a pilot hole for receiving a fixation screw 10 (as
shown, e.g., in FIGS. 2a, 2b and 3a). As shown, the drill may have
a shank portion 307 and a bit portion 308. The bit portion 308 may
include a spiral or parabolic fluted tip 309 having proximal 310,
medial 311, and distal 312 portions. The root diameter at the
medial portion 311 is substantially equal to the diameter of the
fixation screw 10, and the diameter decreases as the distal portion
312 tapers away from the shank 307. The proximal portion 310 of the
bit 308 may be used as a visual indicator during drilling, to
determine the point at which the proper bore depth has been
attained. The drill mechanism may have a central lumen (not shown)
having a diameter slightly greater than the diameter of the guide
pin 20 (as illustrated in FIG. 6a) running along its length, so
that, with the guide pin 20 in place, the drill 306 may be disposed
about the guide pin 20 during drilling to ensure proper location of
the pilot hole with respect to the articular surface 55.
Alternatively, a self-drilling or self-tapping screw, may be used,
as those skilled in the art will recognize.
[0164] For surface preparation and accurate measurement of the
implant site and the subsequent sizing of the implant, instrument
120 is provided. The compass instrument 120 may be configured to
serve as a mounting tool for a number of functional blades or tips
and when located about the axis 20A, via guide rod 20, may be used
for measuring and cutting operations. In the embodiment shown in
FIG. 15a, compass instrument 120 includes handle 110, a cannulated
shaft 111 that extends through the handle, and a cannulated distal
offset arm 112. The instrument may be rigid in construction and may
be a durable reusable and resterilizable instrument. The distal
offset arm 112 is configured so that it can be introduced into a
site through an incision 200 typical of an arthroscopic procedure.
Once the distal offset arm 112 has fully penetrated the incision
and enters the site, shaft 111 can be angularly repositioned so
that it becomes more coaxial to the reference axis 20A and advanced
in-line with the reference axis 20A towards the implant target
site. While performing this maneuver to position the compass
instrument 120, the guide pin 20 should be removed from its
position in the defect 1. When compass 120 is in its proper
position at or near the implant target site, the guide pin 20 is
delivered through the instrument cannulation 113, re-establishing
the working (reference) axis 20A used to define the implant
geometry.
[0165] Referring to FIG. 15b, within offset arm 112 is a slotted
surface 114 for engaging a series of cutting blades 121, boring
blades 124, or measuring probes 122. The slots 115 are configured
so that said series of cutting blades 121, boring blades 124 (FIG.
17c), measuring probes 122, 123 (FIGS. 17a, 17b), or like elements
may be partially constrained or fixed in position such that they
may be adjusted linearly along the length of the slotted surface
114 over a defined distance of travel. Intersecting the plane of
travel defined by slotted surface 114 and slots 115, is the
cannulation 113.
[0166] As illustrated in FIG. 16, when fitted with a cutting blade
121, and with the guide pin 20 advanced through the shaft 113 of
instrument 120, so that the guide pin passes through a closely
sized hole 116 in the cutting blade, the blade's position becomes
fully constrained. When constrained in this fashion, a fixed length
from the rotational or reference axis 20A to the cutting surface
117 of cutting blade 121 is established. This defines the radius
that is effected as the instrument 120 is rotated around the guide
pin 20, and corresponds to the overall diameter of the implant 40
that is delivered to the fully prepared site. The cutting blade 121
is used to circumscribe and cleanly cut the surrounding articular
cartilage.
[0167] In an alternative embodiment, as shown in FIGS. 17a and 17b,
blade 123 and measuring probe 122, respectively, may have multiple
holes 118 that defines that probe/blade's functional diameter. In
addition, the blades may be specifically configured so that staged
or sequential cuts of varying depths and diameters can be performed
within the procedure. Also, such a blade can be configured by
providing a readable scale 119 corresponding to the hole 118
pattern, so that the surgeon may determine and set the appropriate
diameter as needed by positioning the guide pin 20 in the
corresponding hole. As the readable scale 119 may be located on the
blade 123 with respect to the blade's cutting surface 117, a high
degree of positional accuracy may be achieved as the scale may be
defined specifically for each type of blade. This approach creates
an inexpensive means of providing sharp blades of varying diameters
and varying blade types without a large inventory of size- and
type-specific blades. Referring to FIG. 17b, rounded tip 109 of
measuring probe 122 can be used to determine the appropriate
diameter and can be similarly sized and secured in the compass
instrument 120. The tip 109 may be rounded to prevent marring of
the articular surface. FIG. 17c shows a boring bit or bone cutting
blade 124 with multiple cutting surfaces 107 and 108 configured in
this fashion.
[0168] Turning now to FIGS. 9a and 9b, with the guide pin 20
replaced, a measuring tool 70 is inserted so that the reference
axis 20A is utilized. A central element of the measuring tool 70 is
a post 75 that is static, establishes the axial location of the
point of origin 80, and mates with a rotational location feature
within the screw 14. By rotating the outer arm or outrigger 71 of
the measuring tool 70 relative to the static post 75 while also
maintaining contact with the articular surface 55, an axial
displacement or Z dimension can be established relative to the
point of origin 80 for any point along the sweep of the outrigger.
Each such Z dimension may be recorded in real time with
conventional dial gauge indicators 72 or with a digital recording
device, such as disclosed in U.S. Pat. No. 5,771,310 to Vannah, or
by using other known marking techniques. Although numerous points
may be taken, ideally a minimum number of points are taken to
define accurately the target articular surface. In other
embodiments, multiple outriggers that embody different diameters or
an adjustable outrigger may be used to map larger defects, and also
to determine the final diameter of the prosthetic surface that fits
within the defect. It is noted that the measuring tool may comprise
a spring or other tensioning device (not shown), for urging the
outrigger distally with respect to the handle of the tool. In this
aspect, the outrigger is manually pressed against the articular
cartilage, so as to maximally compress the articular cartilage upon
recording data points, so that the data points taken are of a
maximally "loaded" or "compressed" dimension.
[0169] FIGS. 20a, 20b and 20c show an alternative measuring and
mapping device 210 for obtaining the articular surface dimension,
comprising housing 217 and a recording element 218. As shown in
FIG. 20a, recording element 218 includes upper portion 219, flange
222 and calibrated lower portion 220. Key-shaped surface 221
located at distal end 225 of recording element 218 is configured to
engage a reciprocal key-shaped surface in the proximal extension 14
of fixation screw 10, or, for example, a key shaped cover arranged
on the proximal end of the screw (not shown). The upper portion 219
of recording element 218 may be constructed of a relatively soft or
other deformable material that can be marked with patient data.
Cannulated shaft 223 runs through the central lumen of the
recording element 218. As shown in FIG. 20b, housing 217 includes a
marking mechanism 224 located on the upper portion 226 of the
housing, at or within window or aperture 230. An indexing indicator
228 is located on the lower portion 227 of the housing 217, at
window or opening 229.
[0170] Turning to FIG. 20c, recording element 218 is inserted in
housing 217 of measuring and mapping device 210, so that the distal
end 225 of recording element 218 appears through opening 232.
Tensioning means (not shown) in the device 210, enables recording
element 218 to move longitudinally within housing 218. With the
guide pin 20 replaced, the measuring device 210 is inserted on the
guide pin on reference axis 20A so that key-shaped surface 221
engages the corresponding keyed surface of the screw and is
maintained in static position thereby. These key-shaped surfaces
establish the rotational position of the articular surface points
to be mapped relative to the screw. During the measuring and
mapping procedure, the surgeon rotates housing 217 and outer arm or
outrigger 231 located at the distal end 235 of housing. By
depressing marking mechanism 224, a series of depressions or marked
points 240 is established in the relatively soft surface of the
upper portion 219 of the recording element 218, which deforms at
these marked points so that they can be utilized as patient data.
Indexing indicator 228 and calibrated lower portion 220 of
recording element 217 allow for controlled rotational movement
between housing 217 and recording element 218. In this way, the
rotational position of the mapped articular surface points 235
relative to the screw 10 as appreciated by outer arm of outrigger
231, is translated to the implant geometry as a feature so that the
accurate rotational location of the implant 40 relative to the
screw 10 is maintained.
[0171] For example, as shown in FIGS. 8b and 9b, to accurately
reproduce the two radii 60 and 61 that locally define the articular
surface 55, four points, 81a and 81b, and 82a and 82b, and the
point of origin 80 are recorded. As any three points in a single
plane define a curve, by recording points 81a and 81b and the point
of origin 80, radius 60 defining the medial-lateral aspect 68 of
the chondyle can be determined. By recording points 82a and 82b and
the point of origin 80, the radius 61 defining the
anterior-posterior aspect 69 of the chondyle can be determined. In
the example provided, in order to maintain the relationship between
these two defined radii, 60 and 61, the measuring tool 70 is
constructed so that it can be accurately indexed from a fixed
starting point along 90 degree intervals to capture or map said
four points 81a, 81b, 82a and 82b, over the course of its
revolution.
[0172] Locating surfaces or features created on the radius cover
30, or along some length of the fixation screw 10, hex-shaped drive
surface of the screw 14 or on the cylindrical proximal extension
(or recess) of the screw 14, correlate to some surface or feature
on the measuring tool 70 and allow the measurement of the
rotational position of the four measured points 81a, 81b, 82 and
82b, about the reference axis 20A with respect to said locating
surfaces. This data becomes important in configuring the implant 40
with respect to the fixation screw 10 so that the proper
orientation of said measured points to fabricated geometry is
maintained. Of course, such measuring tool can be configured to
measure any number of points at any interval desired.
[0173] While the measurements are illustrated in FIGS. 9a and 9b as
being taken from the bottom of the radiused surface 31 of the
hex-shaped cover 30 of the screw, the measurements may
alternatively be taken from the top of the screw 10' itself, as
shown in FIG. 9b. As shown, in this embodiment, a key 315 or other
alignment feature may be provided, to indicate the starting point
for taking measurements. In this configuration, the measuring tool
used, as well as the implant manufactured, both have a mating
feature matching the key 315, for properly locating the starting
point of the measurements taken and thereby subsequently properly
aligning the implant with respect to the defect.
[0174] Other embodiments of measuring and recording tools are
possible. One such embodiment of a measuring and recording tool
210' is shown in FIGS. 20d-20i. As shown, measuring tool 210'
comprises a handle 316, outer shaft 333, inner shaft 330, scroll
317, a tactile feedback portion 318, ring 320 having a button 321
in communication with a sharp marking point 326 thereunder, a
rotating portion 322 having a rotational lock 323 which prevents
rotation of the rotating portion 322 when engaged, and an outrigger
portion 324. The handle 316 remains fixed during rotation and does
not move while the tool 210' is used for measuring. Instead, the
rotating portion 322 is rotated to a start position and the
rotational lock is engaged, securing the rotating portion 322 to
the tactile feedback portion 318 and thereby preventing its
rotation. The scroll 317 is configured with a notch 325 or similar
mating feature to align with a corresponding mating feature (not
shown) of the handle 316, such that the scroll can only align at
one rotational point, at 0 degrees, with respect to the handle 316
upon loading into the tool 210', e.g., by "snapping" into place.
The sharp marking point 326 located inside the ring 320 under the
sharp marking point 326, marks a point of depression into the
scroll 317 while first button 321 is being depressed. Instead of
marking by making depressions on a scroll or spool, marking could
alternatively be made upon nearly any surface, e.g., using ink to
record on a paper spool, or by digital means.
[0175] As shown in FIGS. 20f and 20g, outer shaft 333, which is
fixedly coupled to rotating portion 322, outrigger 324 and ring
320, is freely rotatably disposed about inner shaft 330 and
slidably disposed about inner shaft 330 within a range bounded by
points 334 and 337. In FIG. 20f, the outrigger 324 is retracted,
and outer shaft 333 is located at a position of origin along a
z-axis parallel to the inner 330 and outer 333 shafts, such that
the proximal end of the ring 320 is located at position 335. In
FIG. 20g, the outrigger 324 is extended, and outer shaft 333 is
located at a position 0.250 in. (0.64 cm.) from the origin of the
z-axis parallel to the inner 330 and outer 333 shafts, such that
the proximal end of the ring 320 is located at position 335'. The
motion of the sliding of the outer shaft 333 about inner shaft 330
during marking is translated via the outer shaft 333, rotating
portion 322 and ring 320 (including marking button 321 and marking
point 326) to a location along the scroll 317. Thus, as the user
rotates outrigger 324 by rotation of rotating portion 322, the
outrigger moves along the articular surface proximally or distally
with respect to the inner shaft, and the displacement of the
outrigger 324 along a z-axis parallel to the inner 330 and outer
333 shafts may be marked on the scroll 317 by depression of the
button 323 at various points along the rotation of the outrigger
324. The tactile feedback portion 318 has a series of depressions
319 or other tactile feedback means, e.g. spring ball plungers
which engage in indentations (not shown) in the inner shaft 330,
spaced at 90 degrees from one another, so that when the rotational
lock 323 is engaged as rotating portion 322 is being rotated, the
user feels a "click" or other tactile feedback to indicate to the
user the rotational location of the rotating portion 322 at 90
degree intervals with respect to the handle 316, i.e., at 90
degrees, 180 degrees, 270 degrees, and 0 (or 360) degrees, for
purposes of marking at those points. It is further noted that the
starting point for marking may or may not be selected independent
of the 90-degree rotational points, and that the rotating portion
322 may or may not be configured so that it is not tied to the
90-degree indexing until the scroll lock 323 is engaged.
[0176] As shown in FIGS. 20e, 20h and 20i, a keyed mating feature
331 may be disposed at the distal end of the inner shaft 330 with
respect to the outrigger portion, for mating with a key feature 315
on the screw 10' (as shown in FIGS. 9c and 20i), so as to locate
properly the starting point of the measurements taken with respect
to the screw, and the scroll 317. FIG. 20h illustrates a more
detailed view of the distal end of the marking tool 210', with
outer shaft 333, inner shaft 330 with keyed mating feature 331, and
outrigger 324 with rounded end 338, which travels along the path of
circle 339. FIG. 20i illustrates the measuring tool 210', with the
keyed mating feature 331 inserted into the recessed portion 303 of
the screw 10' at its fixation element 302.
[0177] Referring now to FIG. 14a, data recorded during the mapping
procedure described above can then be entered into a known
parametric engineering design software or similar algorithm, as
four values, 85a, 85b, 85c, and 85d, corresponding to the four
measured points, 81a, 81b, 82a and 82b, with the origin 80 defining
a reference plane. These four values 85a, 85b, 85c and 85d, are
represented by line elements that are geometrically constrained to
lie upon a circle 90, which represents the diameter of the
measuring tool 70. These line elements are also constrained to lie
within planes that are perpendicular to one another. Of course,
more than four points may be taken and used to map the articular
surface, e.g., 8 points; however, a minimum of four points should
be taken, so that two intersecting datum curves may be defined for
purposes of mapping.
[0178] Datum curves 86 and 87, representing the medial-lateral
("ML") and anterior-posterior ("AP") curves, are constructed by
connecting the end points of the line elements 81a and 81b, and 82a
and 82b and the point of origin 80, which is common to both curves.
These two datum curves 86 and 87 can be used to construct the
articular or bottom surface 41 of the prosthetic implant 40. By
sweeping datum curve 87 along a path defined by datum curve 86, a
three dimensional surface is now defined.
[0179] By constructing this series of geometric relationships in a
known parametric engineering model, patient-specific geometry can
be input as values and the model algorithm can be run to reproduce
the anatomic contours mapped in the patients within only a few
moments. As a process, this generic model is the starting point for
all patient treatments. Sterile pins, screws, and measuring devices
that are all non-patient-specific may be stocked in the hospital
and ready to use whenever an appropriate defect is diagnosed.
Patient-specific data may be transmitted from the surgeon to the
fabricating facility via an interface to the Internet or other
network. Data input into the interface may be read directly into
the generic parametric model to produce a viewable and even
mappable patient-specific parametric model within moments.
Confirmation by the surgeon could initiate a work order for the
production of the patient specific device. Existing technology
allows the parametric model to generate toolpaths and programming,
e.g., to a CAD/CAM system comprising appropriate hardware and/or
software coupled to appropriate data-driven tools, to fabricate the
implant.
[0180] Defining two additional datum curves 88 and 89, at offset
distances from datum curves 86 and 87, is performed to define the
top or non-bearing surface 42 of the implant 40. This top surface
42 should be closely matched to the bearing surface geometry to be
implanted without having to remove an excessive quantity of bone
from the chondral surface.
[0181] Referring to FIGS. 14c and 19c, implant geometry may be
defined whereby the top or bone contacting surface 42 of the
implant 40 exhibits an axial symmetry. The central axis AA passes
through the point of origin 80 of the implant 40 and when the
implant is positioned at the target site, aligns with the original
reference axis 20A as defined by the guide pin 20 and fixation
screw 10. The central axis AA can then be used to define the
preparation tools so that the bone contacting surfaces 42 of the
implant 40 and the preparation tools can be matched in both
configuration and dimension to create a mating fit between the
surface of the prepared target site and the bone contacting
surfaces 42 of the implant. For example, if the preparation tools
can be fabricated using some of the same dimensions obtained during
the articular surface mapping procedure, the implant geometry and
corresponding preparation tool geometry can be mated and optimized
so that a minimum vertical thickness of the implant as well as a
minimum depth of bone removal is required. This may be advantageous
in ensuring good long term clinical results with the implant, as
poor quality of fit between bone surfaces and bone-contacting
surfaces of traditional orthopedic prosthetic devices has been
noted to contribute to early clinical failures.
[0182] For example, as shown in FIGS. 14c and 19c the top or bone
contacting surface 42 of the implant 40, a series of radial cuts
198 may create surfaces that increase resistance of the implant to
rotational forces. These features may be located at the outer
diameter 190 of the implant 40 to increase their effectiveness.
Additional contact surfaces may also be created by one or more
protrusions 195 located on the bottom 42 of the implant. Similarly,
surface treatments known in the field of orthopedic devices, such
as porous and/or osteoconductive coatings, may be utilized on
surface 42.
[0183] As shown in FIG. 19b, outer diameter 190 may include a
slight outward taper or protrusion 197 along the diametrical
surface to enhance load bearing or load transfer properties of the
implant to surrounding bone. This feature may also increase the
fixation strength of the implant. A fillet 199 (as shown in FIG.
19a) that runs around the implant at the intersection of the
diametrical surface 190 and the bearing surface 41 is also useful
in providing a smooth transition between the host articular
cartilage and the implant surface.
[0184] However, if a greater depth of implant is needed as a result
of the defect appearance the offset curves 88 and 89 (as shown in
FIG. 14a) can be extended to increase the overall thickness of the
implant 40 or the offset curves may be eliminated entirely so that
the contoured surface is backed by a revolved geometry that is
symmetrical to reference axis 20A. Turning to FIG. 19c, where the
ML curve and AP curve (defined by the obtained measurements) are
not axially symmetrical, the thickness of the implant 40 requires
adjustment. At the same time, an unnecessarily thick implant
requires a greater amount of bone to be removed at the target site.
Therefore, the thickness of the implant may be determined by taking
the largest obtained measurement and adding a minimal offset amount
208. (The implant is thinnest at the highest point on the ML
curve.) This can be similarly accomplished by adjusting the angle A
(FIG. 19a) of the bone-contacting surface 42 of the implant 40 and
a corresponding angle of the preparation tool. This also allows for
a correction of the implant geometry, to compensate for any
non-perpendicular placement of the guide pin with respect to the
articular surface.
[0185] With reference now to FIGS. 25 and 26, an exemplary
algorithm consistent with the invention establishes the minimum
thickness of an implant necessary to include all patient data
points, receiving as input all of the points measured (typically,
four) and identifying the largest value. One such exemplary
algorithm is as follows (and as shown in FIGS. 25 and 26):
TABLE-US-00001 maxval= D6 if maxval < D11 maxval = D11 endif if
maxval < D14 maxval = D14 endif D684 = maxval + .045
In the foregoing exemplary algorithm, a first data point D6 is
initially assigned as the maximum value (maxval). If . . . then
type statements are used to compare other data points (D11 and D14)
to maxval. If other data points are greater than maxval, the
algorithm reassigns maxval to the new larger data point. LLMT
represents the height of the lower limit plane along the z-axis,
and ULMT represents the height of the upper limit plane along the
z-axis. D684 is a dimension that controls the ULMT plane, which is
established in the model as the upper surface of the implant. ULMT
is positioned as maxval plus an additional arbitrary and/or fixed
material offset (0.045 in this case).
[0186] FIGS. 5c and 5d illustrate an alternative embodiment of the
implant 40', having a ML curve between data points 340 and 341 and
an AP curve between data points 342 and 343, with male-shaped
mating component 304 and key-shaped portion 344 for engagement with
a reciprocal key-shaped surface in the proximal extension of a
fixation screw, protrusions 345 (creating contact surfaces on the
top 346 of the implant 40'), radial cuts 347 located at the outer
diameter 348 of the implant 40', and radius 349 (which may be
formed, e.g. using an abrasive wheel) around the intersection of
the outer diameter at point 341 and the surface comprising the
patient geometry.
[0187] Referring to FIGS. 18a and 18b, bone cutting or scoring
instrument 250 includes a handle (not shown), a cannulated shaft
111 that extends through the handle, and offset arm 140 housing
adjustable blades 141. In the embodiment shown, individual cutting
blades 141 are attached to offset arm 140 either fixedly or
removably, e.g. via threaded portions 142, into threaded recesses
342 of the offset arm 140, although other attachment means may be
used. With guide pin 20 advanced through shaft 113 positioned on
the reference axis 20A, a fixed distance from the rotational or
references axis 20A to each of the cutting or scoring blades 141 is
established. These lengths define the radii that are to be effected
in the articular surface, as the scoring instrument 250 is rotated
around the guide pin 20, corresponding to the protrusions 195 on
the bone contacting surface 42 of the implant 40 creating a
matching fit between the bone surfaces of the prepared target site
and the bone contacting surfaces of the implant.
[0188] In an alternative embodiment, as shown in FIG. 18c, cutting
blades are arranged on carrier 145, configured so that it can be
mounted within the slotted surface 114 of offset arm 112, depicted
in FIG. 17a. In another embodiment, as shown in FIG. 18d, cutting
blades 141 can be fixedly positioned on offset arm 140. Using the
same dimensions obtained during articular surface mapping
procedure, the cutting and scoring device 250 can be fabricated to
prepare the articular surface to correspond to the implant geometry
to optimize fit. In another alternative embodiment, as shown in
FIG. 18e, a bone cutting instrument 352 corresponds to the
alternative embodiment of the implant 40' illustrated in FIGS. 5c
and 5d. Instrument 352 has a handle (not shown), a cannulated shaft
353 that extends through the handle and through the cannulation
355, offset arm 354 with blades 350 and 351 corresponding to the
protrusions 345 on the bone contacting surface 42 of the implant 40
creating a matching fit between the bone surfaces of the prepared
target site and the bone contacting surfaces 346 of the implant
40'.
[0189] As shown in FIG. 14b, an angular dimension 95, relating some
locating surface or feature on the hex-shaped cover 30 or on the
fixation screw 10, to the four points 81a, 81b, 82a and 82b, may
also be captured at the time of the initial procedure to assist in
orientation of the implant 40 to the fixation screw 10. Guide
aperture 46 in implant 40 is located off the reference axis 20A and
may serve as the locating feature and/or as a suture passage way in
the implantation procedure. Alternatively, a surface or feature
created on the implant 40, may serve to reference or align to such
locating surface on the hex-shaped cover 30 or the fixation screw
10.
[0190] Additional data can be taken at the time of the initial
procedure, e.g., for fabricating a non-circular implant. Additional
data curves can also be defined by measuring the offsets from the
reference axis 20A and determining diameters at these offsets. The
final implant geometry, although measured using circular
techniques, need not be circular.
[0191] Referring to FIGS. 10a and 10b, following fabrication of the
implant 40, a second procedure is performed. If a cover 30 (or
plug) is in place, it is removed, exposing proximal extension 14
(or recess) or some other precision taper or engagement surface
located at the proximal end 17 of the fixation screw 10 to which
the implant 40 is to be affixed. A pin having a distally mounted
element or barb 5 is placed through through hole 16 running through
the central lumen of the fixation screw 10 so that the distally
mounted element 5 is secured into the screw. The distally mounted
element 5 carries one or more suture strands 85 that now trail from
the fixation screw 10. Alternatively, a pin, braided cable, or
flexible wire may also be used. However, sutures may make passing
the implant 40 through the incision 200 and subsequent handling
easier.
[0192] Turning to FIGS. 11a and 11b, the sutures 85 are then
threaded through guide aperture 46 of the implant 40 and a knot or
bead 49 may be created proximal to the implant, so that tensing one
of the free running sutures 85 helps to advance the implant 40
toward the proximal extension 14 (or recess) of the fixation screw
10. Alternatively, the suture strands 85 can be passed through the
central lumen or shaft of a driving rod or other instrument to aid
in seating the implant 40, and positioned in the fixation screw 10
thereafter.
[0193] If necessary, the arthroscopic wound 200 is expanded
slightly in either a vertical or horizontal direction, so that the
implant 40 may be passed through. A polymeric sleeve (not shown)
positioned over the implant may prove helpful in passing the
implant through the incision. As shown in FIG. 11b, based on the
size of the implant 40, anatomy of the knee 50, and retraction of
the knee, it may be necessary to position the implant in the
interchondular notch 77 as a staging area prior to final placement.
By continuing to manipulate and tension the suture strands 85, the
implant 40 can be brought coaxial to the proximal extension 14 of
the fixation screw 10.
[0194] As shown in FIGS. 15c and 15d, alternatively, driver 130
includes handle 110, a cannulated shaft 111 that extends through
the handle and a cannulated seat portion 131 attached to the end of
the shaft. Tether element 135, which may comprise sutures or wire,
is passed through driver 130 and is threaded through implant 40
through guide aperture 46, connecting the implant to the driver
toward seat portion 131. The implant 40 and the driver 130 are then
inserted arthroscopically through incision 200 to the target site.
By tensioning tether element 135 at the end 136 of handle 110, the
implant 40 is drawn back into seat portion 131 of driver 130. By
maintaining tension on tether element 135, the implant 40 can then
be controllably delivered to the prepared target site. At least the
inner surface of seat portion 131 comprises a material that can be
impacted to seat the implant 40 without damaging the implant
surface.
[0195] Referring to FIG. 12, once coaxial, the implant 40 can be
aligned via engagement of the proximal extension 14 on fixation
screw 10 and precisions taper 44 on the bottom surface 42 of the
implant and any locating feature, and driven into place with a
plastic driving rod 91 and mallet 95. A protrusion 92 of high
strength material mounted at the distal tip 93 of the driving rod
91 may be necessary to ensure that the rod stays centered on the
implant 40 during driving.
[0196] Finally, as shown in FIG. 13, through guide aperture 46 on
the upper surface 41 of the implant 40, bone cement 300 may be
injected to enhance the contact surface between the implant 40 and
the subchondral bone 100. Vents, such as milled slots 13 in the
fixation screw 10, and in the walls of the implant central
protrusion may be desirable to facilitate the flow of such
materials.
[0197] Alternatively, guide aperture 46 in the implant 40 may be
altogether eliminated by using an alternative implant delivery
system, as shown in FIGS. 19d through 19i, corresponding to an
implant similar to that shown in FIGS. 5c and 5d. The alternative
system comprises the implant 40'' and a washer 361 for holding a
suture 363, the washer 361 being adapted to fit into a taper lock
ring 360. The ring 360 has a taper lock portion 362 having a series
of notches 365 along its perimeter, creating flaps 372 that permit
the taper lock portion 362 to flex somewhat. The taper lock portion
362 has a diameter gradually tapering from the middle to the
proximal end 364 of the ring. The taper lock ring 360 may also have
an alignment notch 386 or similar feature for properly aligning the
taper lock ring 360 with respect to key-shaped portion 344 of the
implant 40'', which is to engage with a reciprocal key-shaped
surface in the proximal extension of a fixation screw, so as to
seat properly the implant rotationally with respect to the defect
site when it is later seated thereon. A washer 361 is disposed
between the ring 360 and the implant 40'' and has two apertures 366
disposed in a recessed area 367 in the center of the washer. The
suture 363 is threaded through the two apertures 366 to form a
suture loop 368, which remains in the recessed area when the ends
of the suture 363 are pulled, so as to keep the suture loop 368
below the top surface 369 of the washer 361. The implant 40'' has a
diameter at its center portion 370 that is approximately equal to
the inner diameter of the ring 360 at its taper lock portion 362.
Thus, when tension is applied to the ends of the suture 363, the
taper lock portion 362 of the ring 360 may flex outward to receive
slidably therein the implant 40'' and washer 361, which
subsequently lock into the taper lock portion 362 of the ring, once
the center portion 370 of the sides of the implant 40'' is seated
within the proximal end 364 of the ring by friction fit, as shown
in FIG. 19e. It is noted that the center portion 370 of the sides
of the implant 40'' to be of a width permitting the implant and
washer to travel slidably within the ring 360 to some degree.
[0198] As shown in FIG. 19f, a hex nut 373 may be integrally formed
in the center of the washer 361 on its bottom side 374, for mating
with an appropriately configured tool for seating the implant 40''.
As FIG. 19f illustrates, the implant 40'', along with washer 361,
ring 360, and sutures 363, is pushed through the incision 200 at
the defect site. Next, as shown in FIGS. 19g-19i, illustrative of
successive steps in the process of seating the implant, a seating
tool 380 may be used to seat the implant. Seating tool 380
comprises a shaft 385, a handle 381 (which may have a through hole
382, if the same handle and/or shaft is used with interchangeable
tips for performing various functions, although a through hole 382
is not integral to seating the implant), and tip 383 suitably
configured to drive hex nut 373 (or other mating feature) and
having an aperture 384 through which the ends of the suture 363 may
be threaded. Once the tip 383 of the tool 380 is introduced into
the incision 200, the sutures 363 may be used as a guide for
seating the tip 383 of the tool 380 onto the hex nut 373, which may
be accomplished by alternately pulling on each end of the suture
363 to toggle the tip 383 of the tool 380 back and forth. Once the
tip 383 of the tool 380 is seated onto the hex nut 373, the tool
380 may be rotated in either direction to seat the implant assembly
properly (comprising implant 40'', taper lock ring 360, and washer
361) at the defect site. This may be effected by rotating tool 380
until alignment notch 386 and corresponding key-shaped portion 344
of the implant 40'' are aligned with the corresponding reciprocal
key-shaped surface in the proximal extension of the fixation screw,
whereby the implant should slide into place, thereby properly
seating the implant rotationally with respect to the defect site.
As shown in FIG. 12 with respect to the prior described embodiment,
once properly seated, the implant 40'' can be driven into place
with a plastic driving rod 91 and mallet 95, and as shown in FIG.
13 with respect to the prior described embodiment, bone cement 300
may also be placed prior to the final seating of the implant 40''
to enhance the contact surface between the implant 40'' and the
subchondral bone 100. It should be understood that the taper lock
ring 360, washer 361, and sutures 363 described with respect to
this embodiment allow the implant to be noncannulated but still
easily handled. These elements are not required to be constructed
as illustrated herein, and may be replaced by adhesive components,
suction components, or other components serving the same
function.
[0199] As FIGS. 21 and 22 illustrate, a unitary (one-piece) implant
400 may also be constructed, thereby obviating the need for a
fixation screw, taper lock ring, washer, and suture. In this
embodiment, implant 400 has key-shaped portion 401 for engagement
with a reciprocal key-shaped surface 411 in an aperture 412 at the
defect site 410, a plurality of barbs 402 (or other mating
features, e.g., one or more threads, ribs, fins, milled slots,
tapered distal features, features to prevent rotational movement of
the implant, or features to increase friction between the implant
and the aperture at the defect site) for producing outward tension
within the aperture 412 at the defect site 410 and for increasing
the contact surface area of the implant 400 with respect to the
aperture 412 at the defect site 410. In this embodiment, an
aperture 412 having a key-shaped surface 411 or other feature for
mating with the implant is created directly in the defect site 410,
by boring, abrasion, or other techniques for forming an
appropriately shaped aperture in the chondral bone 410 for
receiving an implant 400 having a corresponding key-shaped or other
mating feature 401. It should also be recognized that, in this or
other embodiments, the fixation screw could be replaced with a
tensioned member attachment, e.g., anchored to the distal femoral
cortex. Alternatively, the fixation screw could be configured as a
guide wire, only to define the axis AA corresponding to an axis
about the point of origin in the implant to be used (as shown in
FIGS. 14c and 19c), but not to provide mechanical anchoring to or
for the implant.
[0200] FIG. 23 illustrates other alternative embodiments for an
implant consistent with the invention, showing a perspective view
of the components of an exemplary composite implant, in one
embodiment of the present invention. As shown, implant 500
comprises top 501 and bottom 502 portions. Top portion 501 has a
bottom surface 503 which may be glued, welded, bonded, or otherwise
attached to top surface 504 of bottom portion 502, while bottom
surface 505 of bottom portion 502 comprises the patient geometry
and is the load-bearing surface of the implant, as set forth
hereinabove. Top 504 and bottom 505 surfaces of the bottom portion
502 may comprise, in whole or in part, bioengineered material,
while top portion 501 may comprise a material such as titanium. In
such a configuration, top portion 501 may be fabricated and/or
manufactured (e.g. in large quantities) as a universal, generic,
standard supply item for medical practitioners, which merely needs
to be attached to a custom-machined bottom portion 502 comprising
the patient-specific geometry. Surfaces 503 and 504 may be flat or
may comprise other mating features, shapes or configurations.
[0201] Further composite implant embodiments are illustrated in
FIG. 24, wherein implant 600 comprises the patient-specific
geometry 603 and a uniform thickness material bottom portion 602
comprising the bottom or bearing surface 606. The bottom surface
603 of top portion 601 mates with the top surface 604 of bottom
portion 602, and surfaces 603 and 604 may be flat or may comprise
other mating features, shapes or configurations. Lip 605 of bottom
portion 602 has an inside diameter substantially the same as the
outside diameter of top portion 601, so that top portion 601 fits
slidably into bottom portion 602, whereby the two portions 601 and
602 may be glued, welded, bonded, or otherwise attached to one
another. Bottom surface 606, being of uniform thickness, reflects
the patient-specific geometry which surface 603 comprises and is
the load-bearing surface of the implant.
[0202] Other materials from which an implant consistent with the
invention may be constructed, in whole or in part, include ceramic,
e.g. aluminum oxide or zirconium oxide; metal and metal alloys,
e.g. Co--Cr--W--Ni, Co--Cr--M, CoCr alloys, CoCr Molybdenum alloys,
Cr--Ni--Mn alloys, powder metal alloys, 316L stainless steel, Ti
6Al-4V ELI; polymers, e.g., polyurethane, polyethylene (wear
resistant and cross-linked), thermoplastic elastomers;
biomaterials, e.g. polycaprolactone; and diffusion hardened
materials, e.g. Ti-13-13, Zirconium and Niobium. Coatings used may
include, e.g., porous coating systems on bone-contacting surfaces,
hydrophilic coatings on load-bearing surfaces, hydroxyapatite
coatings on bone-contacting surfaces, and tri-calcium phosphate on
bone-contacting surfaces. Additionally, components of the invention
may be molded or cast, hand-fabricated, or machined.
[0203] Alternatively, measurement methods may be utilized whereby
radius measurements are taken with respect to an axis AA
corresponding to an axis about the point of origin in the implant
to be used (as shown in FIGS. 14c and 19c). The technique is used
in reverse, whereby aiming devices are used to place axis AA with
respect to prefabricated generic-geometry implants.
[0204] It is noted that, although the invention is herein described
as utilizing a single reference axis, multiple reference axes may
be used for measuring, mapping, or cutting a single defect or an
articular surface having multiple defects, as well as for
fabricating a single implant, or multiple implants for a single
articular surface, consistent with the invention. In other
embodiments, methods for mapping the defect and/or articular
surface other than those described hereinabove are possible, e.g.,
MRI or CT scanning, fluoroscopy, ultrasound, bone density, other
stereotactic systems, nuclear medicine, or other sound or light
wave-based imaging methods.
[0205] It is further noted that, although the invention is
described herein as utilizing the specific geometry of a patient's
articular surface to fabricate an implant for that patient, it is
contemplated that data from a plurality of patients may be analyzed
statistically and utilized in fabricating and/or manufacturing
(e.g. in large quantities) one or more universal, generic, or
standard supply item type implants for medical practitioners to use
in a procedure consistent with the invention. For such implants, as
well as for patient-specific implants as described herein, pre- or
post-implantation trimming may be required to correct for minor
variations that may occur as between the implant and the
subchondral bone (or other articular surface).
[0206] It should be understood that, although the various tools
described hereinabove, e.g., for measuring, cutting, and seating,
are described as separate devices, a single handle, shaft and/or
instrument may be configured to serve as a universal mounting tool
for a series of devices for performing various functions consistent
with the invention.
Generic Bone Resurface Implant, Cutting Tool, and Procedure
[0207] FIGS. 27a-48 depict another exemplary embodiment of the
present invention. In this embodiment a generic bone implant (or
set of standardized implants) is created (or selected) based on
developing an axis normal to the surface and collecting only one
data point. In the above-described embodiments, a non-normal axis
was utilized, and four data points were required to develop ML and
AP curves. Further, a generic cutting tool is used to cut the bone
at this site to a point where a generic implant can be used.
Several improved tools relating to the procedure for using such an
implant (as well as for using implants as described hereinabove)
are further described in this section and illustrated in the
corresponding figures.
[0208] FIG. 27a depicts an exemplary drill guide device 700
according to this exemplary embodiment. The guide 700 includes a
contact surface 702 of known diameter d on the distal end 708 of
the guide, where diameter d is generally the width of the widest
portion of the site of the lesion. The distal end 708 of the guide
is generally a hollowed-out toroidal structure attached to a handle
706. A central lumen 704 runs the length of the guide from the
attachment point of the distal end 708 to the handle 706, and
through the handle 706. The guide device may be constructed in a
number of other ways, including, e.g., a distal end 708 comprising
a transparent material, e.g., polycarbonate or another clear
plastic. For example, as shown in FIG. 27b, a guide device 700' may
comprise a distal end 708' (which could comprise either an opaque
or a transparent material) having a plurality of cutaway areas 743
to improve visibility and the accuracy of drill location with
respect to the site of a lesion. The guide device may also comprise
a tripod-like construction, or other construction comprising fins,
or projections. It should be noted that, instead of a central lumen
being used to locate the working axis, a cylindrical bore located
at some distal location of the guide may serve to create a working
axis that is not necessarily coaxial to the handle or connecting
shaft of the instrument.
[0209] Referring now to FIGS. 28a and 28b, the present embodiment
operates on the assumption that to a first approximation an
anatomical model of some articular surfaces (e.g., knee, hip, etc.)
can be assumed to be locally spherical. In other words, as shown in
FIGS. 28a and 28b, the AP plane and ML plane, respectively, are
depicted, wherein each corresponds to a model of the articular
surface of a femoral region. These figures break up these
cross-sections into a plurality of radii of arcs defining the
articular surface, i.e., R.sub.1-R.sub.4 in the AP plane, and
R.sub.5-R.sub.7 in the ML plane. In this embodiment, the inventors
herein have found that surfaces in some regions can be assumed to
be substantially locally spherical. Thus, for example, the present
embodiment assumes that R.sub.3 approximately equals R.sub.6 (i.e.,
R.sub.3 is within 50% of R.sub.6). Under these assumptions, a
normal axis can easily be developed. Once developed, one data point
then needs to be defined to obtain the relevant geometry of an
implant, as will be described below. If R.sub.3 is not within 50%
of R.sub.6, an alternative method for developing an axis normal to
the surface of the lesion site, as described hereinbelow with
reference to FIGS. 49-53, may be used.
[0210] FIGS. 29-34 depict the use of the drill guide, the generic
implant, and procedures therefor, according to this exemplary
embodiment. In FIG. 29, the drill guide 700 is brought up to a
lesion site 712 of the articular surface 710. The guide 700 is
positioned so that the distal end 702 covers the lesion site 712,
such that the contact surface of the distal end 702 makes contact
at a plurality of points around the lesion site 712 on the
articular surface 710. As shown in FIG. 30, with slight pressure
the guide 700 becomes stable and fixed on the articular surface
710. Once seated in position, a guide pin 714 is driven through the
central lumen of the guide to create a working axis that is
generally normal to the articular surface 710 at the point of
contact of the guide pin. As FIG. 31 illustrates, a standard bore
drill (not shown) can be placed over the guide pin 714 to create a
pilot hole 716 for the screw (not shown).
[0211] With reference now to FIG. 32, as with the previous
embodiments described above, a screw 720 is driven into the pilot
hole 716. A cap 722 having a male component 719 adapted to mate
with the female taper 718 of the screw 720 is placed on the screw
720. The screw is driven to the appropriate depth, such that the
top surface of the cap 722 is substantially aligned with the
articular surface 710, within the lesion site 712, thereby ensuring
congruency of the implant to the joint. Turning now to FIG. 33, the
cap 722 is removed, and a rod 730 having a mating taper 731 on its
distal tip is inserted into the screw 720. The guide 700 is
positioned over the rod 730 so that the distal end 702 covers the
lesion once again. As illustrated in FIG. 34, since the length of
the rod 730 and the length of the guide 700 are known, a
measurement of the exposed end length of the rod (l) may be taken.
This will provide the information needed with respect to the
implant geometry, by indicating the distance between the seating
depth in the screw and the tangent point of the implant surface. As
shown in FIG. 35, since the axis, z, is defined (by the drill
guide) as normal to the surface of the implant at a plurality of
points, all dimensions defining the AP and ML curves may be assumed
to be equal, such that only one dimension, l, is left to define the
implant geometry. Variations from knee to knee and within a knee
may be reflected in changes in l. For example, the implant 736 of
FIG. 36 may be compared to the implant 737 of FIG. 37. For implant
736 of FIG. 36, the value of l.sub.1 represents a relatively "flat"
region on the articular cartilage, where the radius of the arc
R.sub.AC1 is a relatively large number. However, for implant 737 of
FIG. 37, the value of l.sub.2 represents a more curved region on
the articular cartilage, where the radius of the arc R.sub.AC2 is a
smaller number than R.sub.AC1. As indicated by clinical data, there
is a range of values for l that suggests 5 to 6 values of l that
will fit a majority of people. Thus, generic, off-the-shelf sized
implants may be made. A single procedure technique involving
establishing the normal axis, measuring l, and selecting the
appropriate size implant is therefore feasible.
[0212] As illustrated in FIG. 38, an exemplary cutting or reaming
tool 740 (e.g., as described hereinabove with respect to FIGS. 15b
and 16) is used to prepare the lesion site 712 to receive the
implant (not shown). The cutting or reaming tool 740 may be
configured so that, when coupled to the axis defined by the guide
pin, it can be used for cutting operations. The tool 740 may have a
cannulated shaft and a distal offset arm having a cutting or blade
surface (not shown) having a radius corresponding to the radius of
the implant to be used, such that the articular cartilage may be
circumscribed by rotation of the tool 740 for cleanly cutting the
surrounding articular cartilage in preparation for receiving the
implant. The tool 740 may be configured so that, when coupled to
the axis defined by the guide pin, it can be used for cutting
operations. The proximal face of the screw 720 may serve as a depth
stop for the proximal portion of the tool 740, thereby defining a
cutting/reaming depth corresponding to the thickness of the
implant, l.
[0213] Those skilled in the art will recognize that the cutting
tool may be motorized in certain embodiments, and/or alternatively,
as illustrated in FIG. 39, an exemplary cutting tool 744 may
comprise a cannulated shaft 749, a circular blade portion 745
having a leading edge 746 comprising a blade surface turned on the
distal-most portion. Such a tool 744 may further comprise a handle
portion 747 and may be adapted to be turned by hand by the operator
of the tool by means of rotating the handle 747, or alternatively,
may be motorized in certain embodiments.
[0214] FIG. 40 illustrates an exemplary cleaning tool 770 for
cleaning the female taper (not shown) of the screw 720 prior to
delivery of the implant. The distal end 771 of an exemplary
cleaning tool 770 comprises a semi-rigid material formed into a
shape adapted to enter into the female taper of the screw 720 and
be manipulated by the operator of the tool, to remove tissue or
other debris therefrom, thereby ensuring a good mate of the female
taper 720 of the screw and the male taper of the implant to be
delivered (not shown).
[0215] FIGS. 41-43 illustrate an exemplary suction tool 760 for
holding the implant by means of a suction force and delivering it
to the lesion site, as well as the steps of an exemplary procedure
for using the suction tool 760 to deliver an implant. As
illustrated in FIG. 41, an exemplary suction tool 760 comprises an
elastomeric suction tip 761 at its distal portion 767, a proximal
surface 768, an inlet 762 for mating with a suction tube 763
connected either to a hospital wall suction supply 764 or other
suction system, and a switch or valve 765 for controlling the
suction force. As FIG. 42 illustrates, when the suction force at
the elastomeric suction tip 761 is activated by the switch or valve
765, the implant 742 is held in place, and thus, the suction tool
760 may be used to hold the implant prior to, and during, the
delivery thereof. As shown in the cross-sectional view of FIG. 43,
the distal portion 767 of an exemplary suction tool 760 may
comprise a rigid tip 766 (which may comprise, e.g., plastic
material) disposed within the elastomeric suction tip 761. Force
may be applied to the rigid tip 766 (e.g., by striking or pressing
on the proximal surface 768 of the tool 760) in order to seat the
implant 742 within the lesion site, once the male taper 769 of the
implant 742 and its corresponding mating component(s) 778 are
properly aligned with the female taper of the screw (not shown) and
its corresponding mating component(s). Since the suction tip 761 is
elastomeric (e.g., rubber), upon application of such force, the
material will compress, allowing impact to be transferred to the
implant 742 for purposes of seating it. It is noted that, in
addition to its utility in delivering an implant, a suction tool
760 as described herein (or a suction tool similar thereto) might
also be used at some point during the process of removing an
implant (e.g., in the event the implant is not fully seated).
[0216] FIG. 44 illustrates an exemplary implant 742 driven into the
lesion site 712 of the articular surface 710 once the site 712 has
been sufficiently reamed or cut.
[0217] FIG. 45 illustrates an exemplary implant removal or revision
tool 750 comprising a shaft portion 751 and a distal portion 753,
and FIG. 46 is a cross-sectional view illustrating the exemplary
tool 750 with a removed implant 742 being held in place therein. As
shown, the distal portion 753 of the tool 750 may comprise an
approximately cylindrical structure with a circular blade portion
752 having a leading edge 758 comprising a blade surface turned on
the distal-most portion and a lip portion 755 disposed proximally
with respect to the leading edge 758. A plurality of slits 754
parallel to the longitudinal central axis of the distal portion 753
are disposed along the length of the cylindrical structure, so as
to permit sufficient outward expansion of the distal portion 753 to
accommodate the top edge of the implant 742 therein. Thus, when the
distal portion 753 of the tool 750 is forced onto an implant 742 to
be removed, and driven down over the implant 742, the distal
portion 753 will snap/lock into place once the lip portion 755 of
the distal portion 753 of the tool 750 passes the top edge of the
implant 742 being removed, thereby holding the implant 742 in place
within the distal portion 753 of the tool 750, as shown in FIG. 46.
At this point, a device such as a slap-hammer or slide hammer (not
shown) may be used to unseat the implant 742. An exemplary such
device may comprise a shaft having a weight slidably disposed
thereon, wherein one end of the shaft is connected to the proximal
end (not shown) of the tool 750 and the other end of the shaft
comprises a stop for preventing the weight from moving off the
shaft, and wherein the weight is propelled away from its connection
point with the proximal end of the tool 750, such that it stops
abruptly at the stop and exerts a pulling force on the implant.
Alternative Embodiment of Screw
[0218] FIGS. 47 and 48 illustrate an exemplary alternatively-keyed
embodiment of the screw 720' (c.f., key feature 315 of screw 10',
as shown in FIG. 9c) and the exemplary alternatively-keyed implant
742' to which it is adapted to mate. As shown, the male taper
769'of the implant 742' is coupled at its distal end to an offset
mating feature 778' for mating with a corresponding offset mating
feature 779 of the screw 720'. The mating feature 778' of the
implant 742' comprises a generally cylindrical structure (and may
further comprise a rounded or chamfered distal end portion 777'
and/or other geometric features, i.e., recesses and/or protrusions)
and is both offset from the central longitudinal axis of, and
diametrically smaller than, the male taper 769' of the implant
742'. As FIG. 48 illustrates, a generally cylindrical recessed
mating feature 779 (or similar mating recess(es) and/or
protrusion(s), e.g., a rounded or chamfered distal end portion 780)
corresponding to the offset distal mating feature 778' of the
implant 742' is disposed within the innermost portion of the female
taper 718' of the implant 742', and offset from the central
longitudinal axis of the female taper 718'. The female mating
feature 779 of the screw is provided to mate with the offset male
distal mating feature 778' of the implant 742', so as to seat the
taper 769' of the implant 742' at a fixed location within the screw
720', thereby preventing rotation of the implant 742' with respect
to the screw 720'. Along with the mating features 778', 779, the
taper structures provided may serve to prevent movement of the
implant 742' with respect to the screw 720'in all directions. A
screw 720' consistent with the present invention may comprise a
titanium alloy, e.g., a 316L stainless steel alloy or a
cobalt-chrome alloy.
Alternative Method for Developing Axis Normal to Lesion Site
Surface
[0219] FIGS. 49-53 illustrate an alternative method for developing
an axis normal to the surface of the lesion site using a biaxial
measuring tool. This method has particular utility for lesion sites
where the radii of arcs defining the articular surface, R.sub.ML
and R.sub.AP, are different, i.e., the region is not locally
spherical. (This would be the case, e.g., if R.sub.3 is not within
50% of R.sub.6, as illustrated in FIGS. 29a and 29b and described
hereinabove.) To develop an axis normal to the surface, a biaxial
measuring tool 800 is provided. The tool 800 comprises an outer
shaft 805 coupled fixedly to an outer component 801 having a set of
arms 803, and an inner shaft 806 slidably disposed within the outer
shaft 805, wherein the inner shaft is coupled fixedly to an inner
component 802 having a set of arms 804. The arms 803, 804 of the
outer 801 and inner 802 components may take several forms, and one
exemplary form for the arms 803, 804 is illustrated in FIGS. 49-53,
wherein the distal portion of each arm 803, 804 tapers outward and
connects to one of four contact portions 808. The contact portions
808 may be, e.g., as shown, one of four arcuate sections of a
generally toroidal member (which may be solid or hollow) having a
generally circular cross-section. (The lengths of the arcuate
sections do not necessarily need to be equal to one another, e.g.,
as illustrated in the exemplary contact portions 808 of FIGS.
49-53, the arcuate lengths of the contact portions 808
corresponding to the inner component 802 are shorter than those
contact portions 808 corresponding to the outer component 801.) The
inner shaft 806 may be biased forward so as to tend to extend from
the outer shaft 805, or may alternatively be advanced manually
without spring bias. The inner component 802 is slid proximally or
distally with respect to the outer component 801, until all of the
contact portions 808 make contact with the articular surface (not
shown). In this manner, the articular surface curvatures may be
separated into AP elements and ML elements, such that four separate
contact points may be extrapolated from the four contact portions
808, based on the relative positions of the inner 802 and outer 801
components, and an axis normal to the surface of the lesion site
may be defined. The shaft of the tool 800 may be cannulated (not
shown), so as to allow a guide pin or wire (or a boring tool) to
pass therethrough and into the articular surface, as described
hereinabove with respect to FIGS. 27a to 31. As shown in FIG. 53,
if the inner 802 and outer 801 components are aligned such that the
four contact portions 808 meet to form a complete toroidal member
or ring, the articular surface must be locally spherical, i.e.,
R.sub.ML and R.sub.AP (as shown in FIG. 49) are equal, and it is
therefore not necessary to use the biaxial tool 800.
[0220] It should be noted that, alternatively, contact surfaces may
be constructed of some pliable, or malleable material(s) so that
independently moving rigid mechanical members are not necessary. As
long as the contact surfaces provide a normalizing force to some
central shaft when the contact surfaces are applied to the
articular surface, a normal axis could be defined.
[0221] In another embodiment, this biaxial guide could be replaced
by a series of sized "trials" or gauges of predefined surfaces of
varying dimensions, which are simply pressed onto the articular
surface to visually determine an appropriate fit. These gauges may
resemble an implant, as described herein, without any features
(e.g., fixation element or screw) on the underside, and may contain
a handling tab or other element for holding the gauge. The contact
surfaces of these gauges may have a circular cross section, an
ovular cross section, or another cross-section comprising a
plurality of points to surround a defect in an articular surface,
and the plurality of points may or may not lie in the same plane.
Although they may be less precise or less accurate than other
measuring methods described herein, it is contemplated that implant
selection could be made directly from these gauges.
Digital Measuring System
[0222] FIGS. 54-61 illustrate an exemplary digital measuring system
consistent with the present invention. As shown, the system 810
comprises a base unit 811 coupled to the handpiece 812 via a cable
813. As described further hereinbelow, the base unit 811 may
comprise a tear strip 814 in or on the chassis for detaching a
printed paper tape comprising measurement data. Such a system may
reduce or eliminate potential for surgical or other human error
with respect to the implementation of the present invention.
[0223] FIG. 55 is an exploded view of an exemplary handpiece 812 in
a digital system consistent with the present invention. The linear
measuring elements of the handpiece 812 are nested concentrically
and coaxially to the rotary measuring elements, so that when the
probe assembly 818 is translated and rotated with respect to the
main body 822 of the handpiece, the .theta. and z dimensions are
simultaneously recorded. The handpiece 812 comprises a main body
822 containing a linear reading head 813 coupled to a linear reader
814, a linear index strip 815, a rotary reading head 821 coupled to
a rotary reader 816, and a rotary index strip 817. The probe
assembly 818 comprises a contact tip 819 coupled to an inner shaft
820 running along the length of the handpiece 813 disposed within
the main body 822. The shaft 820 comprises a mating feature 834 at
its distal end that is keyed to fit in the mating feature of an
implanted screw, such that the shaft 820 provides a rotational
axis. The shaft 820 is rigidly connected to the main body 822 of
the handpiece 812 via a nut 823 at its rear. The handpiece 813 is
coupled to, and transfers motion both rotationally and axially
from, the contact tip 819 via the shaft 820. In this manner, the
linear 815 and rotary 817 strips, which may comprise, e.g., mylar
polyester film having thereon a very fine printed pattern, pass
through the linear 813 and rotary 821 reading heads, respectively,
such that the heads 813, 821 read the pattern on the strips 815,
817 and output data representing the rotational and axial travel of
the contact tip 819.
[0224] Exemplary strips and heads may include those manufactured by
U.S. Digita.TM. Corporation of Vancouver, Wash., USA. FIG. 55a is a
cutaway view illustrating an exemplary printed linear index strip
815 passing through an exemplary linear head 813 for reading, and
FIG. 55b is a cutaway view illustrating two alternative exemplary
printed rotary index strips 817, 817' of varying sizes passing
through an exemplary rotary head 821 for reading. FIG. 55c
illustrates an exemplary linear index strip 815 comprising
concentric "bullseye" circles 830, reference lines 831, a text area
832, and a pattern area 833. FIG. 55d illustrates an exemplary
rotary index strip 817 comprising an opaque area 823, index areas
824, a pattern area 825, a text area 826, crosshairs 827,
concentric "bullseye" circles 828 and a central aperture 829.
[0225] Turning now to FIGS. 56a and 56b, a rotational groove 840
and a linear groove 841 are provided on the handpiece 812, such
that the probe assembly 818 may slide onto the shaft 820 of the
handpiece 812 and snap into the linear 841 and rotational 840
grooves.
[0226] FIGS. 57 and 58 illustrate top and side views, respectively,
of the assembled exemplary handpiece 812.
[0227] FIGS. 59 and 60 illustrate top and side cross-sectional
views, respectively, of the assembled exemplary handpiece 812.
[0228] FIG. 61 illustrates a cutaway view of an exemplary base unit
811 in an exemplary digital measuring system consistent with the
present invention. The base unit 811 comprises a power supply 850
(the system may be battery or AC-line powered), a paper roll 851, a
thermal printer 852, a feed loop dowel 853 for threading the paper
roll 851 into the thermal printer 852, a set of controls or buttons
854, and one or more displays 855 (e.g., LED/LCD). The base unit
811 further comprises appropriate hardware and/or software to
compare measured values to known values, as well as to compare
sweeps to one another to ensure procedural accuracy. Further, the
displays 855 and/or paper printouts from the thermal printer 852
may be adapted to display to the user, based on measured data, the
ideal size of the generic implant to use. If a custom implant is
required, a printout of the data set may be generated using the
printer 852. The base unit 811 may further comprise other means of
recording data (not shown), e.g., floppy disk, hard disk,
memory/flash card, etc., and may further comprise appropriate
hardware to provide output signals (e.g., via RS-232, USB, etc.) to
external hardware. Instead of the strips, heads, and other
recording elements described in the exemplary digital system
hereinabove, other digital measurement methods may be used,
including reflective light or sound methods, and percutaneous
methods (e.g., using a hypodermic needle in conjunction with an
MRI, CT, ultrasound, or other scanning method, wherein the needle
or other handheld device comprises sensing elements for mapping the
articular surface).
[0229] It should be noted that in the digital measuring system and
method described hereinabove (as well as any of the
mapping/measuring techniques herein), a second (or third, etc.) set
of data points may be taken, and the subsequent set(s) of data
points compared with the original data points taken, to reduce the
margin of error from taking only a single set of data points. Thus,
a software algorithm in a system or method consistent with the
invention may comprise appropriate routines to effect such
comparisons, for error reduction purposes.
[0230] Further Alternative Implant Structures
[0231] Turning to FIG. 62A, a top perspective view of an
alternative exemplary implant 6200 that includes a protrusion 6204
that extends at least partially around the periphery of the device.
In the exemplary embodiment, the protrusion 6204 is provided to
cover at least a portion of an un-excised portion of articular
surface, however, this is not a structural requirement of the
device of the present embodiment. With a substantially round
implant 6200 as illustrated in FIG. 62A, the protrusion 6204 may
surround the entire circumference of the implant 6200 and may
extend radially outward from the center point P of the implant
6200. Alternatively, with other round and non-round implants as
detailed further herein, the protrusion may be selectively placed
around portions of the perimeter of the implant.
[0232] The implant 6200 may include a radial ring 6220 formed on
the bone-facing distal surface of the implant 6200. The radial ring
may be dimensioned to the excised portion such that the arcuate
shaped outer side surface 6223 defines the size of the cut portion
in the articular surface. The radial ring 6220 may have a width r4
in a radial direction from the center point P of the implant 6200
and a height h1 in the z-axis direction. The arcuate shaped outer
side surface 6223 of the radial ring 6220 may be a radial distance
r1 from the center point P of the implant 6200. The radial ring
6220 may also include a plurality of radial slots 6224 spaced
evenly along the circumference of the ring in order to assist with
anchoring of the implant to the bone.
[0233] Turning the FIG. 62B, a cross-sectional view of the implant
6200 taken along the line B-B of FIG. 62A is illustrated. The
radial ring 6220 is positioned relative to the center point P as it
would be with other such implants earlier described, e.g., the
circular implant illustrated in FIGS. 25 and 26. The protrusion
6204 is formed by an extension 6206 from the radial ring and an
extension 6232 of the load bearing proximal surface. These
extensions join at 6214 to define the protrusion 6204.
[0234] The top or proximal surface 6232 of the protrusion 6204 may
simply be an extension of the proximal or load bearing surface 6205
of the implant 6200. As such, the protrusion 6204 extends beyond
the outside arcuate edge 6223 of the radial ring 6220. Accordingly,
the protrusion 6204 has a width r3 at any one point along the
perimeter of the implant 6200 equal to the difference between the
radial distance r2 from the center point P of the implant to the
exterior edge 6214 of the protrusion 6204 and the radial distance
r1 from the center point P of the implant to the outside arcuate
edge 6223 of the radial ring 6220. The width r3 of the protrusion
may be a consistent width around the entire perimeter of the
implant or may vary along the perimeter as conditions of the
proximate articular cartilage vary.
[0235] The protrusion 6204 is also defined by a bone-facing or
distal surface 6206 that may extend to cover a portion of the
un-excised articular surface 6218. The distal surface 6206 of the
protrusion 6204 may be shaped in any number of ways to match the
mating edge of the articular surface 6218 proximate to the distal
surface 6206 of the rim 6204. As illustrated in FIG. 62B, the
distal surface 6206 may have an arcuate shape for this purpose.
[0236] Turning to FIG. 62C, a side perspective view of the implant
6200 is illustrated. As illustrated, the protrusion 6204 may be
advantageously configured to follow the mapped contour of the
mating articular surface, e.g., articular cartilage. In other
words, the distal surface 6206 of the rim 6204 may vary along the
perimeter of the implant in order to match the edge of the
articular cartilage which it covers based on mapping configurations
as previously detailed herein.
[0237] Turning to FIG. 63A, a side perspective view of another
alternative embodiment of an implant 6300 is illustrated. In this
embodiment, the implant 6300 includes a protrusion 6304 with
protuberances 6312a, 6312b, 6312c, and 6312d formed at selected
locations along the periphery of the protrusion 6304, and may be
used, for example, to secure the target articular surface proximate
to the distal surface 6306 of the protrusion 6304. The
protuberances 6312a, 6312b, 6312c, and 6312d may be any variety of
shape or geometry and are preferably spaced equal distances around
the outside perimeter of the protrusion 6304. The protuberances may
also have barbs or teeth (not shown) to enhance grip to the
articular surface. In the embodiment of FIG. 63A, the interface
between the implant 6300 and a fixation device, e.g., a screw, may
need to be revised in order to allow more axial range of
forgiveness for interlock of the protuberances to the articular
cartilage.
[0238] Turning to FIG. 63B, a cross-sectional view of the implant
6300 taken along the line B-B of FIG. 63A is illustrated. As
illustrated, the protuberances 6312a, 6312d couple to the distal
portion 6306 of the rim 6304 in order to more securely couple the
protrusion 6304 to the un-excised portion of the articular surface
6318 proximate to the implant 6300.
[0239] Turning to FIG. 64A, another alternative embodiment of an
implant 6400 is illustrated. In the embodiment of FIG. 64A, the
proximal or load bearing surface 6405 has a perimeter edge 6406
that is configured to be separated a predetermined radial distance
r5 from a surrounding articular surface 6418 when the implant is
properly seated in a patient. As such, a cavity 6428 or trough
defined by a bottom cavity surface 6408, a side cavity surface
6406, and the cut side of articular surface 6418 is formed.
[0240] Turning to FIG. 64B, a cross sectional view of the implant
6400 of FIG. 64A taken along the line B-B is illustrated which
further shows the details of such a cavity 6428. The articular
cartilage 6418 may then settle or remodel into the cavity 6428. One
side 6406 of the cavity 6428 may be arcuate shaped and may be
depressed a predetermined distance relative to the load bearing
surface 6405. The dimensions of the cavity may be large enough to
permit sufficient space for the articular cartilage 6418 to remodel
or settle into such cavity, but small enough so that articular
cartilage 6418 may remodel into such space within a reasonable time
frame after seating of the implant 6400.
[0241] Turning to FIG. 65A, another alternative implant 6500
embodiment consistent with the invention is illustrated. This
implant 6500 has a non-round or elongated shape. The concept behind
this geometry of the implant is to provide extension of the implant
in the AP plane without being constricted by the width of the
condyle. In other words, the implant of this embodiment may be
derived from a circular implant that has a radius that extends
beyond the width of the condyle in the ML plane. The circular
implant structure may then be truncated along the "sides" that form
the edges of the condyle in the ML plane, thus forming the
elongated implant depicted in FIG. 65A. The implant 6500 has a
least two side surfaces 6517, 6519 each having a concentric arcuate
shape with a common center. As with implants described previously
herein, the implant 6500 has an arc Arc.sub.AP and an arc
Arc.sub.ML that represent the curvature of the proximal surface
6505 of the implant 6500.
[0242] The implant 6500 has a length from an anterior end of the
implant to a posterior end of the implant along a segment of the
arc Arc.sub.AP. The implant also had a width from the medial end of
the implant to the lateral end of the implant along a segment of
the arc Arc.sub.ML. Obviously, the arc segment in the ML plane is
less than the arc segment in the AP plane, for the non-round or
elongate shaped implant 6500.
[0243] The implant 6500 may also have one concentric arcuate shaped
side surface 6517 located opposite another concentric arcuate
shaped side surface 6519. Such side surfaces 6517, 6519 are
concentric with a common center. Such side surfaces 6517, 6519 are
also configured to mate with a cut or reamed edge of bone and/or
articular cartilage when seating the implant. The implant 6500 also
has a length 16500 in a plane defined by the maximum distance
between two points on the arcuate shaped side surfaces 6517,
6519.
[0244] The implant also may also have two other opposing side
surfaces 6521, 6523. Such surfaces 6521, 6523 are generally flat to
where the surface cutter "runs off" of the condyle. The distance in
a plane between the two side surfaces 6521, 6523 define the width
w6500 of the implant 6500. Having such an elongated or non-round
implant allows the treatment of a greater variety of articular
defects, and may also be effective in reducing fray between the
perimeter of the cut articular cartilage and the implant 6500.
[0245] When articular surface mapping is done using one axis normal
to the surface of the implant, two measuring probes may be
utilized. One measuring probe may be utilized to map the points for
the AP curve and another smaller diameter measuring probe may be
utilized to map the points for the ML curve so as it is revolved
its captures the data for points M and L. The implant 6500 may be
defined by the ML curve swept along the AP curve as previously
described herein. Alternatively, the implant may be a generic bone
surface implant as previously described with reference to FIGS.
27a-48 assuming a locally spherical articular surface site.
[0246] Turning to FIG. 65B, an implant site 6511 may be created by
excising a portion of the articular surface 6508 to match the
implant 6500 shape of FIG. 65A. As such the implant site 6511 may
have two arcuate shaped side surfaces 6531, 6533 located opposite
each other to receive the two arcuate shaped side surfaces 6517,
6519 of the implant 6500. Two other side surfaces 6535, 6537 of the
implant site are configured to mate with the side surfaces 6521,
6523 of the implant 6500.
[0247] The implant site 6511 may be generated a number of ways. In
one instance, a reaming or cutting tool 6524 having a circular
blade portion 6526 with a blade diameter dblade greater than the
width Wsurface of the articular surface 6608 to which the implant
will be affixed may be utilized. Another exemplary reaming tool 744
is discussed more fully with reference to FIG. 39. The circular
blade 6526 of the reaming tool 6524 is depressed into the articular
surface 6508 until it contacts the depth stops in the screw as
previously described herein. A straight line distance dAP is
created since the blade diameter dblade is greater than the width
Wsurface of the articular surface 6608.
[0248] This straight line distance dAP in an AP plane is dependent
on a number of factors including the depth of the cutout bottom
surface 6510 compared to the top or proximal surface 6505 of the
implant, and the shape of the surrounding articular surface 6508 to
which the implant will be applied. Once properly reamed, the
implant site 6511 of FIG. 65B should have a cross sectional view as
illustrated in FIG. 65C. As with prior cutouts, the cutout bottom
surface 6510 will match the undersurface of the implant 6500.
[0249] Turning to FIG. 65D, a perspective view of the elongated or
non-round implant 6500 being placed into the implant site 6511 of
the articular surface 6508 is illustrated. The implant 6500 may be
placed and set into the implant site 6511 using any variety of
tools and methods as previously discussed herein. The arcuate
shaped side surfaces 6517, 6519 mate with edges 6531, 6533 of the
implant site on the anterior and posterior side of the implant
respectively. The other side surfaces 6521, 6523 abut the edges
6535, 6537 of the implant site on the medial and lateral side of
the implant site. These side surfaces 6521, 6523 may be shaped to
match that excised portion of the articular surface on such medial
and lateral sides.
[0250] In one exemplary method of setting the non-round implant
6500, the diameter .phi.1 of one measuring probe may be used to
define the diameter dblade of a round blade 6526 from a reaming
tool 6524. As such, the diameter .phi.1 of such a measuring probe
may typically be equal to the diameter dblade of the round blade
6526 from a reaming tool 6524. The diameter .phi.2 from another
measuring probe may defines the ML curve and hence the arcuate
width of the implant along that curve.
[0251] Turning to FIG. 66A, a top perspective view of another
alternative exemplary elongated implant 6600 having two protrusions
6605, 6605 is illustrated. The protrusions 6605, 6606 may prevent
fraying of the articular cartilage that abuts the anterior and
posterior edge of the elongated implant 6600 when seated in an
excised portion of an articular surface.
[0252] Protrusion 6605 is generally similar to protrusion 6606 so
for clarity, description herein is made to protrusion 6606 only.
Protrusion 6606 may extend radially from the arcuate shaped side
surface 6623 to cover an un-excised portion 6634 of articular
surface 6608 (see FIG. 66B) proximate to the arcuate side surface
6623 of the implant 6600.
[0253] The protrusion 6606 has a width r3 at any one point along
the arc of the implant on the anterior side equal to the difference
between the radial distance r2 from the center point P of the
implant to the exterior edge 6640 of the protrusion 6606, and the
radial distance r1 from the center point P of the implant to the
outside arcuate side surface 6623. The width r3 of the rim may be a
consistent width around the perimeter of the arc or may vary as
conditions of the mating articular cartilage vary. Although not
illustrated, the protrusions 6605, 6606 of the elongated implant
6600 may also have protuberance to more securely affix the rim to
the articular cartilage as described and illustrated earlier with
reference to FIGS. 63A and 63B.
[0254] Turning to FIG. 66B, a top perspective view of the elongated
or non-round implant 6600 having protrusions 6605, 6606 being
placed into an implant site 6611 of the articular surface 6608 is
illustrated. The implant 6600 may be placed and set into the
implant site 6611 using any variety of tools and methods as
previously discussed herein. The protrusion 6606 may cover and
anchor a portion of the articular cartilage 6634 proximate to the
cut edge of the implant site 6611 at the anterior side, while the
protrusion 6605 may similarly cover and anchor a portion of the
articular cartilage proximate to the cut edge of the implant site
6611 at the posterior side of the implant.
[0255] Turning to FIG. 67, a top perspective view of an implant
6700 being placed into a section 6707 of an articular surface 6708
is illustrated. Alternatively, in another method consistent with
the present invention, the articular cartilage of the articular
surface 6708 is not cut. As such, fraying of the articular
cartilage at a cut edge may be avoided.
[0256] In other words, the implant 6700 is mapped and placed within
the borders of the existing defect. As such, the portion of the
articular surface excised for the implant site has a surface area
less than the surface area of the defect. Such an alternative
method may be accomplished by any of the variety of methods
discussed herein. For instance, one method may include locating the
defect in the articular surface, establishing a working axis
substantially normal to the articular surface and substantially
centered within the defect, excising a portion of the bone surface
adjacent to the axis thereby creating an implant site 6711, and
installing the implant in the implant site where a least a portion
6707, 6709 of the existing defect is exposed around a perimeter of
the defect. Such a method may require measuring down to the exposed
subchondral bone, or measuring the articular cartilage surface in
closes proximity to the implant site. Of course, a portion of the
defect 6707 proximate to the posterior side may, of course, have a
different shape or configuration as that portion of the defect 6709
proximate to the anterior side of the implant 6700 when seated.
[0257] Turning to FIGS. 68A-68D, an implant 6800 consistent with
the invention may be provided with a feature to promote and
encourage remodeling of the articular cartilage onto the proximal
surface 6806 of the implant 6800. Such a feature may be an
indentation in the proximal surface 6806 of the implant that may be
of continuous or noncontiguous shape. In one exemplary embodiment
as illustrated in FIGS. 68A and 68B, the indentations are
continuous grooves 6803, 6805, 6807 extending along the proximal
surface 6806 of the implant from one side to another. Such grooves
6803, 6805, 6807 may also be provided with thru holes 6809 to
communicate to the bone surface. FIG. 68B is a cross sectional view
of the implant 6800 taken along the line B-B of FIG. 68A
illustrating the square shaped cross sectional geometry of the
exemplary grooves 6803, 6805, 6807.
[0258] Turning to FIG. 68C, another indentation of the proximal
surface 6806 may be one or more spaces 6832, 6834 created at the
perimeter edge 6830 of the proximal surface 6806 by the particular
geometry of the implant's proximal surface 6806. Such edge spaces
6832, 6834 may also promote and encourage remodeling of the
articular cartilage onto the proximal surface 6806 of the implant
6800.
[0259] Turning to FIG. 68D, a top perspective view of the implant
6800 seated in an articular surface 6816 is illustrated. As
illustrated, indentations such as grooves 6803, 6805, 6807 and edge
spaces 6832, 6834 may promote remodeling of the articular cartilage
such that a portion 6818 of the articular cartilage has extended
over the proximal surface 6806 of the implant 6800. This portion
6818 of articular cartilage may only be a superficial layer of
cartilage, and may only extend over a portion of the proximal
surface 6806 of the implant. However, this remodeling may
facilitate load bearing across the transition between the implant
6800 and the surrounding articular cartilage.
[0260] Those skilled in the art will recognize that the present
invention is subject to other modifications and/or alterations, all
of which are deemed within the scope of the present invention, as
defined in the hereinafter appended claims.
* * * * *