U.S. patent application number 10/160667 was filed with the patent office on 2003-03-20 for methods and compositions for articular resurfacing.
Invention is credited to Lang, Philipp, Linder, Barry, Steines, Daniel.
Application Number | 20030055502 10/160667 |
Document ID | / |
Family ID | 27501594 |
Filed Date | 2003-03-20 |
United States Patent
Application |
20030055502 |
Kind Code |
A1 |
Lang, Philipp ; et
al. |
March 20, 2003 |
Methods and compositions for articular resurfacing
Abstract
Disclosed herein are methods and compositions for producing
articular repair materials and for repairing an articular surface.
In particular, methods for providing articular replacement
material, the method comprising the step of producing articular
replacement material of selected size, curvature and/or thickness
are provided. Also provided are articular surface repair systems
designed to replace a selected area cartilage, for example, a
system comprising at least one solid, non-pliable component and an
external surface having near anatomic alignment to the surrounding
structures.
Inventors: |
Lang, Philipp; (Lexington,
MA) ; Linder, Barry; (Danville, CA) ; Steines,
Daniel; (Palo Alto, CA) |
Correspondence
Address: |
COOLEY GODWARD LLP (R&P)
FIVE PALO ALTO SQUARE
3000 EL CAMINO REAL
PALO ALTO
CA
94306-0663
US
|
Family ID: |
27501594 |
Appl. No.: |
10/160667 |
Filed: |
May 28, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60293488 |
May 25, 2001 |
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60363527 |
Mar 12, 2002 |
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60380695 |
May 14, 2002 |
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60380692 |
May 14, 2002 |
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Current U.S.
Class: |
623/16.11 |
Current CPC
Class: |
A61B 5/4528 20130101;
A61F 2002/30677 20130101; A61F 2310/00011 20130101; A61F 2310/00395
20130101; A61F 2210/0004 20130101; A61F 2310/00077 20130101; A61F
2310/00083 20130101; G06F 30/00 20200101; A61F 2/389 20130101; A61F
2002/3097 20130101; A61F 2310/00023 20130101; A61F 2310/00592
20130101; A61B 17/1662 20130101; A61F 2002/4631 20130101; B33Y
70/00 20141201; A61F 2310/00383 20130101; A61F 2310/00065 20130101;
A61F 2310/00071 20130101; A61F 2310/00047 20130101; A61F 2310/00131
20130101; G06K 9/00 20130101; A61F 2002/30948 20130101; A61F
2310/00155 20130101; A61F 2310/00107 20130101; A61F 2310/00119
20130101; A61F 2310/00293 20130101; A61F 2/30767 20130101; A61F
2002/30957 20130101; A61F 2/30756 20130101; A61F 2310/00113
20130101; A61F 2002/30787 20130101; A61F 2002/30062 20130101; A61F
2310/00017 20130101; A61F 2310/00029 20130101; A61F 2310/00149
20130101; A61B 17/8805 20130101; A61B 5/4504 20130101; Y10T 29/49
20150115; B33Y 80/00 20141201; A61F 2/3859 20130101; A61F 2/30942
20130101; A61B 5/4514 20130101 |
Class at
Publication: |
623/16.11 |
International
Class: |
A61F 002/28 |
Claims
What is claimed is:
1. A method for providing articular replacement material, the
method comprising the step of producing articular replacement
material of selected dimensions.
2. The method of claim 1, wherein the dimensions comprise thickness
and curvature.
3. The method of claim 1, wherein the dimensions comprise size and
curvature.
4. The method of claim 1, wherein the dimensions comprise size,
thickness and curvature.
5. The method of claim 1, wherein the articular replacement
material replaces cartilage and wherein said material is
non-pliable.
6. The method of claim 1, wherein the dimensions of the articular
replacement material are selected following intraoperative
measurements.
7. The method of claim 6, wherein said measurements are made using
imaging techniques.
8. The method of claim 7, wherein said imaging techniques are
selected from the group consisting of ultrasound, MRI, CT scan,
x-ray imaging obtained with x-ray dye and fluoroscopic imaging.
9. The method of claim 6, wherein said measurements are made using
a mechanical probe.
10. The method of claim 9, wherein said measurements are made using
an ultrasound probe, a laser, an optical probe and a deformable
material.
11. The method of claim 1, wherein said producing step comprises
growing or hardening the articular replacement material.
12. The method of claim 1, wherein said producing step comprises
shaping the articular replacement material to the selected
dimensions.
13. The method of claim 12, wherein said shaping is selected from
the group consisting of mechanical abrasion, laser ablation,
radiofrequency ablation, cryoablation and enzymatic digestion.
14. The method of claim 12, wherein said shaping is performed
manually.
15. The method of claim 12, wherein said shaping is performed by
machine.
16. The method of claim 15, wherein said shaping is automated.
17. The method of claim 1, wherein said articular replacement
material is produced postoperatively.
18. The method of claim 1, wherein said articular replacement
material is selected from a library of pre-existing repair
systems.
19. The method of claim 1, wherein said articular replacement
material comprises synthetic materials.
20. The method of claim 19, wherein the synthetic materials
comprise metals, polymers or combinations thereof.
21. The method of claim 5, wherein said cartilage replacement
material comprises biological materials.
22. The method of claim 21, wherein said biological materials
comprise cells.
23. The method of claim 22, wherein said cells are stem cells,
fetal cells or chondrocyte cells.
24. A method of making cartilage repair material, the method
comprising the steps of (a) measuring the dimensions of the
intended implantation site or the dimensions of the area
surrounding the intended implantation site; and (b) providing
cartilage replacement material that conforms to the measurements
obtained in step (a).
25. The method of claim 24, wherein the step (a) comprises
measuring the thickness of the cartilage surrounding the intended
implantation site and measuring the curvature of the cartilage
surrounding the intended implantation site.
26. The method of claim 24, wherein the step (a) comprises
measuring the size of the intended implantation site and measuring
the curvature of the cartilage surrounding the intended
implantation site.
27. The method of claim 24, wherein the step (a) comprises
measuring the thickness of the cartilage surrounding the intended
implantation site, measuring the size of the intended implantation
site, and measuring the curvature of the cartilage surrounding the
intended implantation site.
28. The method of claim 24, wherein step (a) comprises obtaining
and analyzing an image of the cartilage.
29. The method of claim 28, wherein said image is obtained
intraoperatively.
30. The method of claim 24, wherein step (a) comprises using a
mechanical probe intraoperatively to measure the dimensions.
31. The method of claim 30, wherein the mechanical probe comprises
a deformable material.
32. The method of claim 24, wherein step (b) comprises selecting
the cartilage replacement material from a library of pre-existing
repair systems.
33. The method of claim 24, wherein step (b) comprises growing the
cartilage replacement material.
34. The method of claim 24, further comprising shaping the
cartilage material.
35. The method of claim 34, wherein said shaping is by machine.
36. The method of claim 34, wherein said shaping is automated.
37. The method of claim 34, wherein said shaping is selected from
the group consisting of mechanical abrasion, laser ablation,
radiofrequency ablation, cryoablation and enzymatic digestion.
38. The method of claim 24, wherein step (b) comprises growing
cartilage replacement material comprising biological substances ex
vivo.
39. A method of repairing a cartilage in a subject, the method of
comprising the step of implantating cartilage repair material
prepared according to the method of claim 1, into the subject.
40. A method of determining the curvature of an articular surface,
the method comprising the step of (a) intraoperatively measuring
the curvature of the articular surface using a mechanical
probe.
41. The method of claim 40, wherein the articular surface comprises
cartilage.
42. The method of claim 40, wherein the articular surface comprises
subchondral bone.
43. The method of claim 40, wherein the mechanical probe is
selected from the group consisting of an ultrasound probe, a laser,
an optical probe and a deformable material.
44. A method of producing an articular replacement material
comprising the step of providing an articular replacement material
that conforms to the measurements obtained by the method of claim
40.
45. A method of repairing an articular surface in a subject, the
method of comprising the step of implanting articular repair
material prepared according to the method of claim 40 into the
subject.
46. A partial articular prosthesis comprising a first component
comprising a cartilage replacement material; and a second component
comprising one or more metals, wherein said second component has a
curvature similar to subchondral bone, wherein said prosthesis
comprises less than about 80% of the articular surface.
47. The prosthesis of claim 46, wherein said first or second
components comprise a non-pliable material.
48. The prosthesis of claim 46, wherein said first or second
components further comprises a polymeric material.
49. The prosthesis of claim 46, wherein said first component
comprises biological materials.
50. The prosthesis of claim 46, wherein said first component
exhibits biomechanical properties similar to articular
cartilage.
51. The prosthesis of claim 50, wherein said biomechanical
properties are elasticity, resistance to axial loading or shear
forces.
52. The prosthesis of claim 46, wherein the first and second
components comprise two or more metals.
53. The prosthesis of claim 46, wherein the first or second
components are bioresorbable.
54. The prosthesis of claim 46, wherein the first or second
components are porous or porous coated.
55. The prosthesis of claim 46, wherein the first or second
components are smooth.
56. The prosthesis of claim 46, wherein the first or second
components are adapted to receive injections.
57. A partial articular prosthesis for use in a human with
cartilage disease comprising an external surface located in the
load bearing area of an articular surface, wherein the dimensions
of said external surface achieve a near anatomic fit with the
adjacent cartilage.
58. The prosthesis of claim 57, further comprising one or more
metals or metal alloys.
59. An articular surface repair system comprising (a) cartilage
replacement material, wherein said cartilage replacement material
has a curvature similar to surrounding or adjacent cartilage; and
(b) at least one non-biologic material, wherein said articular
surface repair system comprises a portion of the articular surface
equal to or smaller than the weight-bearing surface.
60. The articular surface repair system of claim 59, wherein said
cartilage replacement material is non-pliable.
61. The articular surface repair system of claim 59, wherein said
cartilage replacement material has biomechanical properties similar
to that of normal human cartilage.
62. The articular surface repair system of claim 59, wherein said
cartilage replacement material has a biochemical composition
similar to that of normal human cartilage.
63. An articular surface repair system comprising a first component
comprising a cartilage replacement material, wherein said first
component has dimensions similar to that of adjacent or surrounding
cartilage; and a second component, wherein said second component
has a curvature similar to subchondral bone, wherein said articular
surface repair system comprises less than about 80% of the
articular surface.
64. The repair system of claim 63, wherein said first or said
second component comprises a non-pliable material.
65. The articular surface repair system of claim 63, wherein the
first component has a curvature and thickness similar to that of
adjacent or surrounding cartilage.
66. The articular surface repair system of claim 63, wherein said
thickness of said first component is not uniform.
67. A partial articular prosthesis comprising (a) a metal or metal
alloy; and (b) an external surface located in the load bearing area
of an articular surface, wherein the external surface designed to
achieve a near anatomic fit with the adjacent cartilage.
68. The partial articular prosthesis of claim 67, wherein said
external surface is comprises a polymeric material attached to said
metal or metal alloy.
69. An articular surface repair system comprising a cartilage
replacement material, wherein said cartilage replacement material
has a curvature similar to surrounding or adjacent cartilage,
wherein said articular surface repair system is adapted to receive
injections.
70. The articular surface repair system of claim 69, wherein said
injections are made through an opening in the external surface of
said cartilage replacement material.
71. The articular surface repair system of claims 69, wherein said
opening in the external surface terminates in a plurality of
openings on the bone surface.
72. The articular surface repair system of claim 69, wherein bone
cement is injected through said opening.
73. The articular surface repair system of claim 72, wherein said
bone cement is injected under pressure in order to achieve
permeation of portions of the marrow space with bone cement.
74. The articular surface repair system of claim 72, wherein said
bone cement is combined with a therapeutic drug.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Ser. No.
60/293,488 entitled "METHODS TO IMPROVE CARTILAGE REPAIR SYSTEMS",
filed May 25, 2001, U.S. Ser. No. 60/363,527, entitled "NOVEL
DEVICES FOR CARTILAGE REPAIR, filed Mar. 12, 2002 and U.S. Ser. No.
60/380,695 and Unassigned, entitled "METHODS AND COMPOSITIONS FOR
CARTILAGE REPAIR," (Attorney Docket Number 6750-0005p2) and
"METHODS AND COMPOSITIONS FOR JOINT REPAIR," (Attorney Docket
Number 67500005p3), filed May 14, 2002, all of which applications
are hereby incorporated by reference in their entireties.
TECHNICAL FIELD
[0002] The present invention relates to orthopedic methods, systems
and prosthetic devices and more particularly relates to methods,
systems and devices for articular resurfacing.
BACKGROUND
[0003] There are various types of cartilage, e.g., hyaline
cartilage and fibrocartilage. Hyaline cartilage is found at the
articular surfaces of bones, e.g., in the joints, and is
responsible for providing the smooth gliding motion characteristic
of moveable joints. Articular cartilage is firmly attached to the
underlying bones and measures typically less than 5 mm in thickness
in human joints, with considerable variation depending on joint and
site within the joint. In addition, articular cartilage is aneural,
avascular, and alymphatic. In adult humans, this cartilage derives
its nutrition by a double diffusion system through the synovial
membrane and through the dense matrix of the cartilage to reach the
chondrocyte, the cells that are found in the connective tissue of
cartilage.
[0004] Adult cartilage has a limited ability of repair; thus,
damage to cartilage produced by disease, such as rheumatoid and/or
osteoarthritis, or trauma can lead to serious physical deformity
and debilitation. Furthermore, as human articular cartilage ages,
its tensile properties change. The superficial zone of the knee
articular cartilage exhibits an increase in tensile strength up to
the third decade of life, after which it decreases markedly with
age as detectable damage to type II collagen occurs at the
articular surface. The deep zone cartilage also exhibits a
progressive decrease in tensile strength with increasing age,
although collagen content does not appear to decrease. These
observations indicate that there are changes in mechanical and,
hence, structural organization of cartilage with aging that, if
sufficiently developed, can predispose cartilage to traumatic
damage.
[0005] Usually, severe damage or loss of cartilage is treated by
replacement of the joint with a prosthetic material, for example,
silicone, e.g. for cosmetic repairs, or metal alloys. See, e.g.,
U.S. Pat. No. 6,383,228, issued May 7, 2002; U.S. Pat. No.
6,203,576, issued Mar. 20, 2001; U.S. Pat. No. 6,126,690, issued
Oct. 3, 2000. Implantation of prosthetic devices is usually
associated with loss of underlying tissue and bone without recovery
of the full function allowed by the original cartilage. Serious
long-term complications associated with the presence of a permanent
foreign body can include infection, osteolysis and also loosening
of the implant.
[0006] Further, joint arthroplasties are highly invasive and
require surgical resection of the entire or the majority of the
articular surface of one or more bones. With these procedures, the
marrow space is reamed in order to fit the stem of the prosthesis.
The reaming results in a loss of the patient's bone stock.
[0007] Osteolysis will frequently lead to loosening of the
prosthesis. The prosthesis will subsequently have to be replaced.
Since the patient's bone stock is limited, the number of possible
replacement surgeries is also limited for joint arthroplasty. In
short, over the course of 15 to 20 years, and in some cases shorter
time periods, the patients may run out of therapeutic options
resulting in a very painful, non-functional joint.
[0008] The use of matrices, tissue scaffolds or other carriers
implanted with cells (e.g., chrondrocytes, chondrocyte progenitors,
stromal cells, mesenchymal stem cells, etc.) has also been
described as a potential treatment for cartilage repair. See, also,
International Publications WO; 99/51719; WO 01/91672 and WO
01/17463;U.S. Pat. No. 5,283,980 B1, issued Sep. 4, 2001; U.S. Pat.
No. 5,842,477, issued Dec. 1, 1998; U.S. Pat. No. 5,769,899, issued
Jun. 23, 1998; U.S. Pat. No. 4,609,551, issued Sep. 2, 1986; U.S.
Pat. No. 5,041,138, issued Aug. 20, 199; U.S. Pat. No. 5,197,985,
issued Mar. 30, 1993; U.S. Pat. No. 5,226,914, issued Jul. 13,
1993; U.S. Pat. No. 6,328,765, issued Dec. 11, 2001; U.S. Pat. No.
6,281,195, issued Aug. 28, 2001; and U.S. Pat. No. 4,846,835,
issued Jul. 11, 1989. However, clinical outcomes with biologic
replacement materials such as allograft and autograft systems and
tissue scaffolds have been uncertain since most of these materials
cannot achieve a morphologic arrangement or structure similar to or
identical to that of normal, disease-free human tissue. Moreover,
the mechanical durability of these biologic replacement materials
is not certain.
[0009] Despite the large number of studies in the area of cartilage
repair, the integration of the cartilage replacement material with
the surrounding cartilage of the patient has proven difficult. In
particular, integration can be extremely difficult due to
differences in thickness and curvature between the surrounding
cartilage and/or the underlying subchondral bone and the cartilage
replacement material.
[0010] Thus, there remains a need for methods and compositions for
joint repair, including methods and compositions that facilitate
the integration between the cartilage replacement system and the
surrounding cartilage.
SUMMARY
[0011] The present invention provides novel devices and methods for
replacing a portion (e.g., diseased area and/or area slightly
larger than the diseased area) of a joint (e.g., cartilage and/or
bone) with a non-pliable, non-liquid (e.g., hard) implant material,
where the implant achieves a near anatomic fit with the surrounding
structures and tissues. In cases where the devices and/or methods
include an element associated with the underlying articular bone,
the invention also provides that the bone-associated element
achieves a near anatomic alignment with the subchondral bone. The
invention also provides for the preparation of an implantation site
a single cut.
[0012] In one aspect, the invention includes a method for providing
articular replacement material, the method comprising the step of
producing articular replacement (e.g., cartilage replacement
material) of selected dimensions (e.g., size, thickness and/or
curvature).
[0013] In another aspect, the invention includes a method of making
cartilage repair material, the method comprising the steps of (a)
measuring the dimensions (e.g., thickness, curvature and/or size)
of the intended implantation site or the dimensions of the area
surrounding the intended implantation site; and (b) providing
cartilage replacement material that conforms to the measurements
obtained in step (a). In certain aspects, step (b) comprises
measuring the thickness of the cartilage surrounding the intended
implantation site and measuring the curvature of the cartilage
surrounding the intended implantation site. In other embodiments,
step (a) comprises measuring the size of the intended implantation
site and measuring the curvature of the cartilage surrounding the
intended implantation site. In other embodiments, step (a)
comprises measuring the thickness of the cartilage surrounding the
intended implantation site, measuring the size of the intended
implantation site, and measuring the curvature of the cartilage
surrounding the intended implantation site.
[0014] In any of the methods described herein, or more components
of the articular replacement material (e.g., the cartilage
replacement material) is non-pliable, non-liquid, solid or hard.
The dimensions of the replacement material may be selected
following intraoperative measurements, for example measurements
made using imaging techniques such as ultrasound, MRI, CT scan,
x-ray imaging obtained with x-ray dye and fluoroscopic imaging. A
mechanical probe (with or without imaging capabilities) may also be
used to selected dimensions, for example an ultrasound probe, a
laser, an optical probe and a deformable material.
[0015] In any of the methods described herein, the replacement
material may be selected (for example, from a pre-existing library
of repair systems), grown from cells and/or hardened from various
materials. Thus, the material can be produced pre- or
postoperatively. Furthermore, in any of the methods described
herein the repair material may also be shaped (e.g., manually,
automatically or by machine), for example using mechanical
abrasion, laser ablation, radiofrequency ablation, cryoablation
and/or enzymatic digestion.
[0016] In any of the methods described herein, the articular
replacement material may comprise synthetic materials (e.g.,
metals, polymers, alloys or combinations thereof) or biological
materials such as stem cells, fetal cells or chondrocyte cells.
[0017] In another aspect, the invention includes a method of
repairing a cartilage in a subject, the method of comprising the
step of implantating cartilage repair material prepared according
to any of the methods described herein.
[0018] In yet another aspect, the invention provides a method of
determining the curvature of an articular surface, the method
comprising the step of (a) intraoperatively measuring the curvature
of the articular surface using a mechanical probe. The articular
surface may comprise cartilage and/or subchondral bone. The
mechanical probe (with or without imaging capabilities) may
include, for example an ultrasound probe, a laser, an optical probe
and/or a deformable material.
[0019] In a still further aspect, the invention provides a method
of producing an articular replacement material comprising the step
of providing an articular replacement material that conforms to the
measurements obtained by any of the methods of described
herein.
[0020] In a still further aspect, the invention includes a partial
articular prosthesis comprising a first component comprising a
cartilage replacement material; and a second component comprising
one or more metals, wherein said second component has a curvature
similar to subchondral bone, wherein said prosthesis comprises less
than about 80% of the articular surface. In certain embodiments,
the first and/or second component comprises a non-pliable material
(e.g., a metal, a polymer, a metal allow, a solid biological
material). Other materials that may be included in the first and/or
second components include polymers, biological materials, metals,
metal alloys or combinations thereof. Furthermore, one or both
components may be smooth or porous (or porous coated). In certain
embodiments, the first component exhibits biomechanical properties
(e.g., elasticity, resistance to axial loading or shear forces)
similar to articular cartilage. The first and/or second component
can be bioresorbable and, in addition, the first or second
components may be adapted to receive injections.
[0021] In another aspect, a partial articular prosthesis comprising
an external surface located in the load bearing area of an
articular surface, wherein the dimensions of said external surface
achieve a near anatomic fit with the adjacent cartilage is
provided. The prosthesis of may further comprise one or more metals
or metal alloys.
[0022] In yet another aspect, an articular repair system comprising
(a) cartilage replacement material, wherein said cartilage
replacement material has a curvature similar to surrounding or
adjacent cartilage; and (b) at least one non-biologic material,
wherein said articular surface repair system comprises a portion of
the articular surface equal to or smaller than the weight-bearing
surface is provided. In certain embodiments, the cartilage
replacement material is non-pliable (e.g., hard hydroxyapatite,
etc.). In certain embodiments, the system exhibits biomechanical
(e.g., elasticity, resistance to axial loading or shear forces)
and/or biochemical properties similar to articular cartilage. The
first and/or second component can be bioresorbable and, in
addition, the first or second components may be adapted to receive
injections.
[0023] In a still further aspect of the invention, an articular
surface repair system comprising a first component comprising a
cartilage replacement material, wherein said first component has
dimensions similar to that of adjacent or surrounding cartilage;
and a second component, wherein said second component has a
curvature similar to subchondral bone, wherein said articular
surface repair system comprises less than about 80% of the
articular surface (e.g., a single femoral condyle, tibia, etc.) is
provided. In certain embodiments, the first component is
non-pliable (e.g., hard hydroxyapatite, etc.). In certain
embodiments, the system exhibits biomechanical (e.g., elasticity,
resistance to axial loading or shear forces) and/or biochemical
properties similar to articular cartilage. The first and/or second
component can be bioresorbable and, in addition, the first or
second components may be adapted to receive injections. In certain
embodiments, the first component has a curvature and thickness
similar to that of adjacent or surrounding cartilage. The thickness
and/or curvature may vary across the implant material.
[0024] In a still further embodiment, a partial articular
prosthesis comprising (a) a metal or metal alloy; and (b) an
external surface located in the load bearing area of an articular
surface, wherein the external surface designed to achieve a near
anatomic fit with the adjacent cartilage is provided.
[0025] Any of the repair systems or prostheses described herein
(e.g., the external surface) may comprise a polymeric material, for
example attached to said metal or metal alloy. Further, any of the
systems or prostheses described herein can be adapted to receive
injections, for example, through an opening in the external surface
of said cartilage replacement material (e.g., an opening in the
external surface terminates in a plurality of openings on the bone
surface). Bone cement, therapeutics, and/or other bioactive
substances may be injected through the opening(s). In certain
embodiments, bone cement is injected under pressure in order to
achieve permeation of portions of the marrow space with bone
cement.
[0026] These and other embodiments of the subject invention will
readily occur to those of skill in the art in light of the
disclosure herein.
BRIEF DESCRIPTION OF THE FIGURES
[0027] The file of this patent contains at least one drawing
executed in color. Copies of this patent with color drawing(s) will
be provided by the Patent and Trademark Office upon request and
payment of the necessary fee.
[0028] FIG. 1 is a flowchart depicting various methods of the
present invention including, measuring the size of an area of
diseased cartilage or cartilage loss, measuring the thickness of
the adjacent cartilage, and measuring the curvature of the
articular surface and/or subchondral bone. Based on this
information, a best fitting implant can be selected from a library
of implants or a patient specific custom implant can be generated.
The implantation site is subsequently prepared and the implantation
is performed.
[0029] FIG. 2 is a color reproduction of a three-dimensional
thickness map of the articular cartilage of the distal femur.
Three-dimensional thickness maps can be generated, for example,
from ultrasound, CT or MRI data. Dark holes within the substances
of the cartilage indicate areas of full thickness cartilage
loss.
[0030] FIG. 3 shows an example of a Placido disc of concentrically
arranged circles of light.
[0031] FIG. 4 shows an example of a projected Placido disc on a
surface of fixed curvature.
[0032] FIG. 5 shows an example of a 2D color-coded topographical
map of an irregularly curved surface.
[0033] FIG. 6 shows an example of a 3D color-coded topographical
map of an irregularly curved surface.
[0034] FIG. 7 shows a reflection resulting from a projection of
concentric circles of light (Placido Disk) on each femoral condyle,
demonstrating the effect of variation in surface contour on the
reflected circles.
[0035] FIGS. 8A-H are schematics of various stages of knee
resurfacing. FIG. 8A shows an example of normal thickness cartilage
in the anterior, central and posterior portion of a femoral condyle
800 and a cartilage defect 805 in the posterior portion of the
femoral condyle. FIG. 8B shows an imaging technique or a
mechanical, optical, laser or ultrasound device measuring the
thickness and detecting a sudden change in thickness indicating the
margins of a cartilage defect 810. FIG. 8C shows a weight-bearing
surface 815 mapped onto the articular cartilage. Cartilage defect
805 is located within the weight-bearing surface 815. FIG. 8D shows
an intended implantation site (stippled line) 820 and cartilage
defect 805. The implantation site 820 is slightly larger than the
area of diseased cartilage 805. FIG. 8E depicts placement of a
single component articular surface repair system 825. The external
surface of the articular surface repair system 826 has a curvature
similar to that of the surrounding cartilage 800 resulting in good
postoperative alignment between the surrounding normal cartilage
800 and the articular surface repair system 825. FIG. 8F shows an
exemplary multi-component articular surface repair system 830. The
distal surface of the deep component 832 has a curvature similar to
that of the adjacent subchondral bone 835. The external surface of
the superficial component 837 has a thickness and curvature similar
to that of the surrounding normal cartilage 800. FIG. 8G shows an
exemplary single component articular surface repair system 840 with
a peripheral margin 845 substantially non-perpendicular to the
surrounding or adjacent normal cartilage 800. FIG. 8H shows an
exemplary multi-component articular surface repair system 850 with
a peripheral margin 845 substantially non-perpendicular to the
surrounding or adjacent normal cartilage 800.
[0036] FIG. 9, A through E, are schematics depicting exemplary knee
imaging and resurfacing. FIG. 9A is a schematic depicting a
magnified view of an area of diseased cartilage 905 demonstrating
decreased cartilage thickness when compared to the surrounding
normal cartilage 900. The margins 910 of the defect have been
determined. FIG. 9B is a schematic depicting measurement of
cartilage thickness 915 adjacent to the defect 905. FIG. 9C is a
schematic depicting placement of a multi-component mini-prosthesis
915 for articular resurfacing. The thickness 920 of the superficial
component 923 closely approximates that of the adjacent normal
cartilage 900 and varies in different regions of the prosthesis.
The curvature of the distal portion of the deep component 925 is
similar to that of the adjacent subchondral bone 930. FIG. 9D is a
schematic depicting placement of a single component mini-prosthesis
940 utilizing fixturing stems 945. FIG. 9E depicts placement of a
single component mini-prosthesis 940 utilizing fixturing stems 945
and an opening 950 for injection of bone cement 955. The
mini-prosthesis has an opening at the external surface 950 for
injecting bone cement 955 or other liquids. The bone cement 955 can
freely extravasate into the adjacent bone and marrow space from
several openings at the undersurface of the mini-prosthesis 960
thereby anchoring the mini-prosthesis.
[0037] FIGS. 10A to C, are schematics depicting other exemplary
knee resurfacing devices and methods. FIG. 10A is a schematic
depicting normal thickness cartilage in the anterior and central
and posterior portion of a femoral condyle 1000 and a large area of
diseased cartilage 1005 in the posterior portion of the femoral
condyle. FIG. 10B depicts placement of a single component articular
surface repair system 1010. The implantation site has been prepared
with a single cut. The articular surface repair system is not
perpendicular to the adjacent normal cartilage 1000. FIG. 10C
depicts a multi-component articular surface repair system 1020. The
implantation site has been prepared with a single cut. The deep
component 1030 has a curvature similar to that of the adjacent
subchondral bone 1035. The superficial component 1040 has a
curvature similar to that of the adjacent cartilage 1000.
[0038] FIGS. 11A and B show exemplary single and multiple component
devices. FIG. 11A shows an exemplary a single component articular
surface repair system 1100 with varying curvature and radii. In
this case, the articular surface repair system is chosen to include
convex and concave portions. Such devices can be preferable in a
lateral femoral condyle or small joints such as the elbow joint.
FIG. 11B depicts a multi-component articular surface repair system
with a deep component 1110 that mirrors the shape of the
subchondral bone and a superficial component 1105 closely matching
the shape and curvature of the surrounding normal cartilage 1115.
The deep component 1110 and the superficial component 1105
demonstrate varying curvatures and radii with convex and concave
portions.
DETAILED DESCRIPTION OF THE INVENTION
[0039] The current invention provides for methods and devices for
integration of cartilage replacement or regenerating materials.
[0040] Before describing the present invention in detail, it is to
be understood that this invention is not limited to particular
formulations or process parameters as such may, of course, vary. It
is also to be understood that the terminology used herein is for
the purpose of describing particular embodiments of the invention
only, and is not intended to be limiting.
[0041] The practice of the present invention employs, unless
otherwise indicated, conventional methods of x-ray imaging and
processing, x-ray tomosynthesis, ultrasound including A-scan,
B-scan and C-scan, computed tomography (CT scan), magnetic
resonance imaging (MRI), optical coherence tomography, single
photon emission tomography (SPECT) and positron emission tomography
(PET) within the skill of the art. Such techniques are explained
fully in the literature. See, e.g., X-Ray Structure Determination:
A Practical Guide, 2nd Edition, editors Stout and Jensen, 1989,
John Wiley & Sons, publisher; Body CT: A Practical Approach,
editor Slone, 1999, McGraw-Hill publisher; X-ray Diagnosis: A
Physician's Approach, editor Lam, 1998 Springer-Verlag, publisher;
and Dental Radiology: Understanding the X-Ray Image, editor
Laetitia Brocklebank 1997, Oxford University Press publisher.
[0042] All publications, patents and patent applications cited
herein, whether above or below, are hereby incorporated by
reference in their entirety.
[0043] It must be noted that, as used in this specification and the
appended claims, the singular forms "a", "an", and "the" include
plural references unless the content clearly dictates otherwise.
Thus, for example, reference to "an implantation site" includes a
one or more such sites.
[0044] Definitions
[0045] Unless defined otherwise, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which the invention pertains. Although
any methods and materials similar or equivalent to those described
herein can be used in the practice for testing of the present
invention, the preferred materials and methods are described
herein.
[0046] The term "arthritis" refers to a group of conditions
characterized by progressive deterioration of joints. Thus, the
term encompasses a group of different diseases including, but not
limited to, osteoarthritis (OA), rheumatoid arthritis, seronegative
spondyloarthropathies and posttraumatic joint deformity.
[0047] The term "articular" refers to any joint. Thus, "articular
cartilage" refers to cartilage in a joint such as a knee, ankle,
hip, etc. The term "articular surface" refers to a surface of an
articulating bone that is covered by cartilage. For example, in a
knee joint several different articular surfaces are present, e.g.
in the patella, the medial femoral condyle, the lateral femoral
condyle, the medial tibial plateau and the lateral tibial
plateau.
[0048] The term "weight-bearing surface" refers to the contact area
between two opposing articular surfaces during activities of normal
daily living.
[0049] The term "cartilage" or "cartilage tissue" as used herein is
generally recognized in the art, and refers to a specialized type
of dense connective tissue comprising cells embedded in an
extracellular matrix (ECM) (see, for example, Cormack, 1987, Ham's
Histology, 9th Ed., J. B. Lippincott Co., pp. 266-272). The
biochemical composition of cartilage differs according to type
Several types of cartilage are recognized in the art, including,
for example, hyaline cartilage such as that found within the
joints, fibrous cartilage such as that found within the meniscus
and costal regions, and elastic cartilage. Hyaline cartilage, for
example, comprises chondrocytes surrounded by a dense ECM
consisting of collagen, proteoglycans and water. Fibrocartilage can
form in areas of hyaline cartilage, for example after an injury or,
more typically, after certain types of surgery. The production of
any type of cartilage is intended to fall within the scope of the
invention.
[0050] Furthermore, although described primarily in relation to
methods for use in humans, the invention may also be practiced so
as repair cartilage tissue in any mammal in need thereof, including
horses, dogs, cats, sheep, pigs, among others. The treatment of
such animals is intended to fall within the scope of the
invention.
[0051] The terms "articular repair system" and "articular surface
repair system" include any system (including, for example,
compositions, devices and techniques) to repair, to replace or to
regenerate a portion of a joint or an entire joint. The term
encompasses systems that repair articular cartilage, articular bone
or both bone and cartilage. Articular surface repair systems may
also include a meniscal repair system (e.g., meniscal repair system
can be composed of a biologic or non-biologic material), for
example a meniscal repair system having biomechanical and/or
biochemical properties similar to that of healthy menisci. See, for
example, U.S. Patent Publication No. US 2002/00228841A1. The
meniscal repair system can be surgically or arthroscopically
attached to the joint capsule or one or more ligaments.
Non-limiting examples of repair systems include autologous
chondrocyte transplantation, osteochondral allografting,
osteochondral autografting, tibial corticotomy, femoral and/or
tibial osteotomy. Repair systems also include treatment with
cartilage or bone tissue grown ex vivo, stem cells, cartilage
material grown with use of stem cells, fetal cells or immature or
mature cartilage cells, an artificial non-human material, an agent
that stimulates repair of diseased cartilage tissue, an agent that
stimulates growth of cells, an agent that protects diseased
cartilage tissue and that protects adjacent normal cartilage
tissue. Articular repair systems include also treatment with a
cartilage tissue transplant, a cartilage tissue graft, a cartilage
tissue implant, a cartilage tissue scaffold, or any other cartilage
tissue replacement or regenerating material. Articular repair
systems include also surgical tools that facilitate the surgical
procedure required for articular repair, for example tools that
prepare the area of diseased cartilage tissue and/or subchondral
bone for receiving, for example, a cartilage tissue replacement or
regenerating material. The term "non-pliable" refers to material
that cannot be significantly bent but may retain elasticity.
[0052] The terms "replacement material" or "regenerating material"
include a broad range of natural and/or synthetic materials used in
the methods described herein, for example, cartilage or bone tissue
grown ex vivo, stem cells, cartilage material grown from stem
cells, stem cells, fetal cell, immature or mature cartilage cells,
an agent that stimulates growth of cells, an artificial non-human
material, a cartilage tissue transplant, a cartilage tissue graft,
a cartilage tissue implant, a cartilage tissue scaffold, or a
cartilage tissue regenerating material. The term includes
biological materials isolated from various sources (e.g., cells) as
well as modified (e.g., genetically modified) materials and/or
combinations of isolated and modified materials.
[0053] The term "imaging test" includes, but is not limited to,
x-ray based techniques (such as conventional film based x-ray
films, digital x-ray images, single and dual x-ray absorptiometry,
radiographic absorptiometry); digital x-ray tomosynthesis, x-ray
imaging including digital x-ray tomosynthesis with use of x-ray
contrast agents, for example after intra-articular injection,
ultrasound including broadband ultrasound attenuation measurement
and speed of sound measurements, A-scan, B-scan and C-scan;
computed tomography; nuclear scintigraphy; SPECT; positron emission
tomography, optical coherence tomography and MRI. One or more of
these imaging tests may be used in the methods described herein,
for example in order to obtain certain morphological information
about one or several tissues such as bone including bone mineral
density and curvature of the subchondral bone, cartilage including
biochemical composition of cartilage, cartilage thickness,
cartilage volume, cartilage curvature, size of an area of diseased
cartilage, severity of cartilage disease or cartilage loss, marrow
including marrow composition, synovium including synovial
inflammation, lean and fatty tissue, and thickness, dimensions and
volume of soft and hard tissues. The imaging test can be performed
with use of a contrast agent, such as Gd-DTPA in the case of MRI.
The term "A-scan" refers to an ultrasonic technique where an
ultrasonic source transmits an ultrasonic wave into an object, such
as patient's body, and the amplitude of the returning echoes
(signals) are recorded as a function of time. Only structures that
lie along the direction of propagation are interrogated. As echoes
return from interfaces within the object or tissue, the transducer
crystal produces a voltage that is proportional to the echo
intensity. The sequence of signal acquisition and processing of the
A-scan data in a modem ultrasonic instrument usually occurs in six
major steps:
[0054] (1) Detection of the echo (signal) occurs via mechanical
deformation of the piezoelectric crystal and is converted to an
electric signal having a small voltage.
[0055] (2) Preamplification of the electronic signal from the
crystal, into a more useful range of voltages is usually necessary
to ensure appropriate signal processing.
[0056] (3) Time Gain Compensation compensates for the attenuation
of the ultrasonic signal with time, which arises from travel
distance. Time gain compensation may be user-adjustable and may be
changed to meet the needs of the specific application. Usually, the
ideal time gain compensation curve corrects the signal for the
depth of the reflective boundary. Time gain compensation works by
increasing the amplification factor of the signal as a function of
time after the ultrasonic pulse has been emitted. Thus, reflective
boundaries having equal abilities to reflect ultrasonic waves will
have equal ultrasonic signals, regardless of the depth of the
boundary.
[0057] (4) Compression of the time compensated signal can be
accomplished using logarithmic amplification to reduce the large
dynamic range (range of smallest to largest signals) of the echo
amplitudes. Small signals are made larger and large signals are
made smaller. This step provides a convenient scale for display of
the amplitude variations on the limited gray scale range of a
monitor.
[0058] (5) Rectification, demodulation and envelope detection of
the high frequency electronic signal permits the sampling and
digitization of the echo amplitude free of variations induced by
the sinusoidal nature of the waveform.
[0059] (6) Rejection level adjustment sets the threshold of signal
amplitudes that are permitted to enter a data storage, processing
or display system. Rejection of lower signal amplitudes reduces
noise levels from scattered ultrasonic signals.
[0060] The term "B-scan" refers to an ultrasonic technique where
the amplitude of the detected returning echo is recorded as a
function of the transmission time, the relative location of the
detector in the probe and the signal amplitude. This is often
represented by the brightness of a visual element, such as a pixel,
in a two-dimensional image. The position of the pixel along the
y-axis represents the depth, i.e. half the time for the echo to
return to the transducer (for one half of the distance traveled).
The position along the x-axis represents the location of the
returning echoes relative to the long axis of the transducer, i.e.
the location of the pixel either in a superoinferior or
mediolateral direction or a combination of both. The display of
multiple adjacent scan lines creates a composite two-dimensional
image that portrays the general contour of internal organs.
[0061] The term "C-scan" refers to an ultrasonic technique where
additional gating electronics are incorporated into a B-scan to
eliminate interference from underlying or overlying structures by
scanning at a constant-depth. An interface reflects part of the
ultrasonic beam energy. All interfaces along the scan line may
contribute to the measurement. The gating electronics of the C-mode
rejects all returning echoes except those received during a
specified time interval. Thus, only scan data obtained from a
specific depth range are recorded. Induced signals outside the
allowed period are not amplified and, thus, are not processed and
displayed. C-mode-like methods are also described herein for A-scan
techniques and devices in order to reduce the probe/skin interface
reflection. The term "repair" is used in a broad sense to refer to
one or more repairs to damaged joints (e.g., cartilage or bone) or
to replacement of one or more components or regions of the joint.
Thus, the term encompasses both repair (e.g., one or more portions
of a cartilage and/or layers of cartilage or bone) and replacement
(e.g., of an entire cartilage).
[0062] General Overview
[0063] The present invention provides methods and compositions for
repairing joints, particularly for repairing articular cartilage
and for facilitating the integration of a wide variety of cartilage
repair materials into a subject. Among other things, the techniques
described herein allow for the customization of cartilage repair
material to suit a particular subject, for example in terms of
size, cartilage thickness and/or curvature. When the shape (e.g.,
size, thickness and/or curvature) of the articular cartilage
surface is an exact or near anatomic fit with the non-damaged
cartilage or with the subjects original cartilage, the success of
repair is enhanced. The repair material may be shaped prior to
implantation and such shaping can be based, for example, on
electronic images that provide information regarding curvature or
thickness of any "normal" cartilage surrounding the defect and/or
on curvature of the bone underlying the defect. Thus, the current
invention provides, among other things, for minimally invasive
methods for partial joint replacement. The methods will require
only minimal or, in some instances, no loss in bone stock.
Additionally, unlike with current techniques, the methods described
herein will help to restore the integrity of the articular surface
by achieving an exact or near anatomic match between the implant
and the surrounding or adjacent cartilage and/or subchondral
bone.
[0064] Advantages of the present invention can include, but are not
limited to, (i) customization of joint repair, thereby enhancing
the efficacy and comfort level for the patient following the repair
procedure; (ii) eliminating the need for a surgeon to measure the
defect to be repaired intraoperatively in some embodiments; (iii)
eliminating the need for a surgeon to shape the material during the
implantation procedure; (iv) providing methods of evaluating
curvature of the repair material based on bone or tissue images or
based on intraoperative probing techniques; (v) providing methods
of repairing joints with only minimal or, in some instances, no
loss in bone stock; and (vi) improving postoperative joint
congruity.
[0065] Thus, the methods described herein allow for the design and
use of joint repair material that more precisely fits the defect
(e.g., site of implantation) and, accordingly, provides improved
repair of the joint.
[0066] 1.0. Assessment of Defects
[0067] The methods and compositions described herein may be used to
treat defects resulting from disease of the cartilage (e.g.,
osteoarthritis), bone damage, cartilage damage, trauma, and/or
degeneration due to overuse or age. The invention allows, among
other things, a health practitioner to evaluate and treat such
defects. The size, volume and shape of the area of interest may
include only the region of cartilage that has the defect, but
preferably will also include contiguous parts of the cartilage
surrounding the cartilage defect.
[0068] Size, curvature and/or thickness measurements can be
obtained using any suitable techniques, for example in one
direction, two directions, and/or in three dimensions for example,
using suitable mechanical means, laser devices, molds, materials
applied to the articular surface that harden and "memorize the
surface contour," and/or one or more imaging techniques.
Measurements may be obtained non-invasively and/or intraoperatively
(e.g., using a probe or other surgical device).
[0069] 1.1. Imaging Techniques
[0070] Non-limiting examples of imaging techniques suitable for
measuring thickness and/or curvature (e.g., of cartilage and/or
bone) or size of areas of diseased cartilage or cartilage loss
include the use of x-rays, magnetic resonance imaging (MRI),
computed tomography scanning (CT, also known as computerized axial
tomography or CAT), optical coherence tomography, SPECT, PET,
ultrasound imaging techniques, and optical imaging techniques.
(See, also, International Patent Publication WO 02/22014; U.S. Pat.
No. 6,373,250 and Vandeberg et al. (2002) Radiology
222:430-436).
[0071] In certain embodiments, CT or MRI is used to assess tissue,
bone, cartilage and any defects therein, for example cartilage
lesions or areas of diseased cartilage, to obtain information on
subchondral bone or cartilage degeneration and to provide
morphologic or biochemical or biomechanical information about the
area of damage. Specifically, changes such as fissuring, partial or
full thickness cartilage loss, and signal changes within residual
cartilage can be detected using one or more of these methods. For
discussions of the basic NMR principles and techniques, see MRI
Basic Principles and Applications, Second Edition, Mark A. Brown
and Richard C. Semelka, Wiley-Liss, Inc. (1999). For a discussion
of MRI including conventional T1 and T2-weighted spin-echo imaging,
gradient recalled echo (GRE) imaging, magnetization transfer
contrast (MTC) imaging, fast spin-echo (FSE) imaging, contrast
enhanced imaging, rapid acquisition relaxation enhancement, (RARE)
imaging, gradient echo acquisition in the steady state, (GRASS),
and driven equilibrium Fourier transform (DEFT) imaging, to obtain
information on cartilage, see WO 02/22014. Thus, in preferred
embodiments, the measurements are three-dimensional images obtained
as described in WO 02/22014. Three-dimensional internal images, or
maps, of the cartilage alone or in combination with a movement
pattern of the joint can be obtained. Three-dimensional internal
images can include information on biochemical composition of the
articular cartilage. In addition, imaging techniques can be
compared over time, for example to provide up to date information
on the size and type of repair material needed.
[0072] Any of the imaging devices described herein may also be used
intra-operatively (see, also below), for example using a hand-held
ultrasound and/or optical probe to image the articular surface
intra-operatively.
[0073] 1.2. Intra-operative Measurements
[0074] Alternatively, or in addition to, non-invasive imaging
techniques, measurements of the size of an area of diseased
cartilage or an area of cartilage loss, measurements of cartilage
thickness and/or curvature of cartilage or bone can be obtained
intraoperatively during arthroscopy or open arthrotomy.
Intraoperative measurements may or may not involve actual contact
with one or more areas of the articular surfaces.
[0075] Devices to obtain intraoperative measurements of cartilage,
and to generate a topographical map of the surface include but are
not limited to, Placido disks and laser interferometers, and/or
deformable materials. (See, for example, U.S. Pat. Nos. 6,382,028;
6,057,927; 5,523,843; 5,847,804; and 5,684,562). For example, a
Placido disk (a concentric array that projects well-defined circles
of light of varying radii, generated either with laser or white
light transported via optical fiber) can be attached to the end of
an endoscopic device (or to any probe, for example a hand-held
probe) so that the circles of light are projected onto the
cartilage surface. One or more imaging cameras can be used (e.g.,
attached to the device) to capture the reflection of the circles.
Mathematical analysis is used to determine the surface curvature.
The curvature can then be visualized on a monitor as a color-coded,
topographical map of the cartilage surface. Additionally, a
mathematical model of the topographical map can be used to
determine the ideal surface topography to replace any cartilage
defects in the area analyzed. This computed, ideal surface can then
also be visualized on the monitor, and is used to select the
curvature of the replacement material or regenerating material.
[0076] Similarly a laser interferometer can also be attached to the
end of an endoscopic device. In addition, a small sensor may be
attached to the device in order to determine the cartilage surface
curvature using phase shift interferometry, producing a fringe
pattern analysis phase map (wave front) visualization of the
cartilage surface. The curvature can then be visualized on a
monitor as a color coded, topographical map of the cartilage
surface. Additionally, a mathematical model of the topographical
map can be used to determine the ideal surface topography to
replace any cartilage defects in the area analyzed. This computed,
ideal surface can then also visualized on the monitor, and can be
used to select the curvature of the replacement cartilage.
[0077] One skilled in the art will readily recognize other
techniques for optical measurements of the cartilage surface
curvature.
[0078] Mechanical devices (e.g., probes) may also be used for
intraoperative measurements, for example, deformable materials such
as gels, molds, any hardening materials (e.g., materials that
remain deformable until they are heated, cooled, or otherwise
manipulated). See, e.g., WO 02/34310. For example, a deformable gel
can be applied to a femoral condyle. The side of the gel pointing
towards the condyle will yield a negative impression of the surface
contour of the condyle. Said negative impression can be used to
determine the size of a defect, the depth of a defect and the
curvature of the articular surface in and adjacent to a defect.
This information can be used to select a therapy, e.g. an articular
surface repair system. In another example, a hardening material can
be applied to an articular surface, e.g. a femoral condyle or a
tibial plateau. Said hardening material will remain on the
articular surface until hardening has occurred. The hardening
material will then be removed from the articular surface. The side
of the hardening material pointing towards the articular surface
will yield a negative impression of the articular surface. The
negative impression can be used to determine the size of a defect,
the depth of a defect and the curvature of the articular surface in
and adjacent to a defect. This information can be used to select a
therapy, e.g. an articular surface repair system.
[0079] In certain embodiments, the deformable material comprises a
plurality of individually moveable mechanical elements. When
pressed against the surface of interest, each element may be pushed
in the opposing direction and the extent to which it is pushed
(deformed) will correspond to the curvature of the surface of
interest. The device may include a brake mechanism so that the
elements are maintained in the position that mirrors the surface of
the cartilage and/or bone. The device can then be removed from the
patient and analyzed for curvature. Alternatively, each individual
moveable element may include markers indicating the amount and/or
degree they are deformed at a given spot. A camera can be used to
intra-operatively image the device and the image can be saved and
analyzed for curvature information. Suitable markers include, but
are not limited to, actual linear measurements (metric or
imperial), different colors corresponding to different amounts of
deformation and/or different shades or hues of the same
color(s).
[0080] Other devices to measure cartilage and subchondral bone
intraoperatively include, for example, ultrasound probes. An
ultrasound probe, preferably handheld, can be applied to the
cartilage and the curvature of the cartilage and/or the subchondral
bone can be measured. Moreover, the size of a cartilage defect can
be assessed and the thickness of the articular cartilage can be
determined. Such ultrasound measurements can be obtained in A-mode,
B-mode, or C-mode. If A-mode measurements are obtained, an operator
will typically repeat the measurements with several different probe
orientations, e.g. mediolateral and anteroposterior, in order to
derive a three-dimensional assessment of size, curvature and
thickness.
[0081] One skilled in the art will easily recognize that different
probe designs are possible using said optical, laser
interferometry, mechanical and ultrasound probes. The probes are
preferably handheld. In certain embodiments, the probes or at least
a portion of the probe, typically the portion that is in contact
with the tissue, will be sterile. Sterility can be achieved with
use of sterile covers, for example similar to those disclosed in
WO9908598A1.
[0082] Analysis on the curvature of the articular cartilage or
subchondral bone using imaging tests and/or intraoperative
measurements can be used to determine the size of an area of
diseased cartilage or cartilage loss. For example, the curvature
can change abruptly in areas of cartilage loss. Such abrupt or
sudden changes in curvature can be used to detect the boundaries of
diseased cartilage or cartilage defects.
[0083] 1.3. Models
[0084] Using information on thickness and curvature of the
cartilage, a physical model of the surfaces of the articular
cartilage and of the underlying bone can be created. This physical
model can be representative of a limited area within the joint or
it can encompass the entire joint. For example, in the knee joint,
the physical model can encompass only the medial or lateral femoral
condyle, both femoral condyles and the notch region, the medial
tibial plateau, the lateral tibial plateau, the entire tibial
plateau, the medial patella, the lateral patella, the entire
patella or the entire joint. The location of a diseased area of
cartilage can be determined, for example using a 3D coordinate
system or a 3D Euclidian distance as described in WO 02/22014.
[0085] In this way, the size of the defect to be repaired can be
determined. As will be apparent, some, but not all, defects will
include less than the entire cartilage. Thus, in one embodiment of
the invention, the thickness of the normal or only mildly diseased
cartilage surrounding one or more cartilage defects is measured.
This thickness measurement can be obtained at a single point or,
preferably, at multiple points, for example 2 point, 4-6 points,
7-10 points, more than 10 points or over the length of the entire
remaining cartilage. Furthermore, once the size of the defect is
determined, an appropriate therapy (e.g., articular repair system)
can be selected such that as much as possible of the healthy,
surrounding tissue is preserved.
[0086] In other embodiments, the curvature of the articular surface
can be measured to design and/or shape the repair material.
Further, both the thickness of the remaining cartilage and the
curvature of the articular surface can be measured to design and/or
shape the repair material. Alternatively, the curvature of the
subchondral bone can be measured and the resultant measurement(s)
can be used to either select or shape a cartilage replacement
material.
[0087] 2.0. Repair Materials
[0088] A wide variety of materials find use in the practice of the
present invention, including, but not limited to, plastics, metals,
ceramics, biological materials (e.g., collagen or other
extracellular matrix materials), hydroxyapatite, cells (e.g., stem
cells, chondrocyte cells or the like), or combinations thereof.
Based on the information (e.g., measurements) obtained regarding
the defect and the articular surface and/or the subchondral bone, a
repair material can be formed or selected. Further, using one or
more of these techniques described herein, a cartilage replacement
or regenerating material having a curvature that will fit into a
particular cartilage defect, will follow the contour and shape of
the articular surface, and will match the thickness of the
surrounding cartilage can be made. The repair material may include
any combination of materials, and preferably includes at least one
non-pliable (hard) material.
[0089] 2.1. Metal and Polymeric Repair Materials
[0090] Currently, joint repair systems often employ metal and/or
polymeric materials including, for example, prosthesis which are
anchored into the underlying bone (e.g., a femur in the case of a
knee prosthesis). See, e.g., U.S. Pat. Nos. 6,203,576 and 6,322,588
and references cited therein. A wide-variety of metals may find use
in the practice of the present invention, and may be selected based
on any criteria, for example, based on resiliency to impart a
desired degree of rigidity. Non-limiting examples of suitable
metals include silver, gold, platinum, palladium, iridium, copper,
tin, lead, antimony, bismuth, zinc, titanium, cobalt, stainless
steel, nickel, iron alloys, cobalt alloys, such as Elgiloy.RTM., a
cobalt-chromium-nickel alloy, and MP35N, a
nickel-cobaltchromium-molybdenum alloy, and Nitinol.TM., a
nickel-titanium alloy, aluminum, manganese, iron, tantalum, other
metals that can slowly form polyvalent metal ions, for example to
inhibit calcification of implanted substrates in contact with a
patient's bodily fluids or tissues, and combinations thereof.
[0091] Suitable synthetic polymers include, without limitation,
polyamides (e.g., nylon), polyesters, polystyrenes, polyacrylates,
vinyl polymers (e.g., polyethylene, polytetrafluoroethylene,
polypropylene and polyvinyl chloride), polycarbonates,
polyurethanes, poly dimethyl siloxanes, cellulose acetates,
polymethyl methacrylates, polyether ether ketones, ethylene vinyl
acetates, polysulfones, nitrocelluloses, similar copolymers and
mixtures thereof. Bioresorbable synthetic polymers can also be used
such as dextran, hydroxyethyl starch, derivatives of gelatin,
polyvinylpyrrolidone, polyvinyl alcohol, poly[N-(2-hydroxypropyl- )
methacrylamide], poly(hydroxy acids), poly(epsilon-caprolactone),
polylactic acid, polyglycolic acid, poly(dimethyl glycolic acid),
poly(hydroxy butyrate), and similar copolymers may also be
used.
[0092] The polymers can be prepared by any of a variety of
approaches including conventional polymer processing methods.
Preferred approaches include, for example, injection molding, which
is suitable for the production of polymer components with
significant structural features, and rapid prototyping approaches,
such as reaction injection molding and stereo-lithography. The
substrate can be textured or made porous by either physical
abrasion or chemical alteration to facilitate incorporation of the
metal coating.
[0093] More than one metal and/or polymer may be used in
combination with each other. For example, one or more
metal-containing substrates may be coated with polymers in one or
more regions or, alternatively, one or more polymer-containing
substrate may be coated in one or more regions with one or more
metals.
[0094] The system or prosthesis can be porous or porous coated. The
porous surface components can be made of various materials
including metals, ceramics, and polymers. These surface components
can, in turn, be secured by various means to a multitude of
structural cores formed of various metals. Suitable porous coatings
include, but are not limited to, metal, ceramic, polymeric (e.g.,
biologically neutral elastomers such as silicone rubber,
polyethylene terephthalate and/or combinations thereof) or
combinations thereof. See, e.g., Hahn U.S. Pat. No. 3,605,123.
Tronzo U.S. Pat. No. 3,808,606 and Tronzo U.S. Pat. No. 3,843,975;
Smith U.S. Pat. No. 3,314,420; Scharbach U.S. Pat. No. 3,987,499;
and German Offenlegungsschrift 2,306,552. There may be more than
one coating layer and the layers may have the same or different
porosities. See, e.g., U.S. Pat. No. 3,938,198.
[0095] The coating may be applied by surrounding a core with
powdered polymer and heating until cured to form a coating with an
internal network of interconnected pores. The tortuosity of the
pores (e.g., a measure of length to diameter of the paths through
the pores) may be important in evaluating the probable success of
such a coating in use on a prosthetic device. See, also, Morris
U.S. Pat. No. 4,213,816. The porous coating may be applied in the
form of a powder and the article as a whole subjected to an
elevated temperature that bonds the powder to the substrate.
Selection of suitable polymers and/or powder coatings may be
determined in view of the teachings and references cited herein,
for example based on the melt index of each.
[0096] 2.2. Biological Repair Materials
[0097] Repair materials may also include one or more biological
material either alone or in combination with non-biological
materials. For example, any base material can be designed or shaped
and suitable cartilage replacement or regenerating material(s) such
as fetal cartilage cells can be applied to be the base. The cells
can be then be grown in conjunction with the base until the
thickness (and/or curvature) of the cartilage surrounding the
cartilage defect has been reached. Conditions for growing cells
(e.g., chondrocytes) on various substrates in culture, ex vivo and
in vivo are described, for example, in U.S. Pat. Nos. 5,478,739;
5,842,477; 6,283,980 and 6,365,405. Nonlimiting examples of
suitable substrates include plastic, tissue scaffold, a bone
replacement material (e.g., a hydroxyapatite, a bioresorbable
material), or any other material suitable for growing a cartilage
replacement or regenerating material on it.
[0098] Biological polymers can be naturally occurring or produced
in vitro by fermentation and the like. Suitable biological polymers
include, without limitation, collagen, elastin, silk, keratin,
gelatin, polyamino acids, cat gut sutures, polysaccharides (e.g.,
cellulose and starch) and mixtures thereof. Biological polymers may
be bioresorbable.
[0099] Biological materials used in the methods described herein
can be autografts (from the same subject); allografts (from another
individual of the same species) and/or xenografts (from another
species). See, also, International Patent Publications WO 02/22014
and WO 97/27885. In certain embodiments autologous materials are
preferred, as they may carry a reduced risk of immunological
complications to the host, including re-absorption of the
materials, inflammation and/or scarring of the tissues surrounding
the implant site.
[0100] In one embodiment of the invention, a probe is used to
harvest tissue from a donor site and to prepare a recipient site.
The donor site can be located in a xenograft, an allograft or an
autograft. The probe is used to achieve a good anatomic match
between the donor tissue sample and the recipient site. The probe
is specifically designed to achieve a seamless or near seamless
match between the donor tissue sample and the recipient site. The
probe can, for example, be cylindrical. The distal end of the probe
is typically sharp in order to facilitate tissue penetration.
Additionally, the distal end of the probe is typically hollow in
order to accept the tissue. The probe can have an edge at a defined
distance from its distal end, e.g. at 1 cm distance from the distal
end and the edge can be used to achieve a defined depth of tissue
penetration for harvesting. The edge can be external or can be
inside the hollow portion of the probe. For example, an orthopedic
surgeon can take the probe and advance it with physical pressure
into the cartilage, the subchondral bone and the underlying marrow
in the case of a joint such as a knee joint. The surgeon can
advance the probe until the external or internal edge reaches the
cartilage surface. At that point, the edge will prevent further
tissue penetration thereby achieving a constant and reproducible
tissue penetration. The distal end of the probe can include a blade
or saw-like structure or tissue cutting mechanism. For example, the
distal end of the probe can include an iris-like mechanism
consisting of several small blades. The at least one or more blades
can be moved using a manual, motorized or electrical mechanism
thereby cutting through the tissue and separating the tissue sample
from the underlying tissue. Typically, this will be repeated in the
donor and the recipient. In the case of an iris-shaped blade
mechanism, the individual blades can be moved so as to close the
iris thereby separating the tissue sample from the donor site.
[0101] In another embodiment of the invention, a laser device or a
radiofrequency device can be integrated inside the distal end of
the probe. The laser device or the radiofrequency device can be
used to cut through the tissue and to separate the tissue sample
from the underlying tissue.
[0102] In one embodiment of the invention, the same probe can be
used in the donor and in the recipient. In another embodiment,
similarly shaped probes of slightly different physical dimensions
can be used. For example, the probe used in the recipient can be
slightly smaller than that used in the donor thereby achieving a
tight fit between the tissue sample or tissue transplant and the
recipient site. The probe used in the recipient can also be
slightly shorter than that used in the donor thereby correcting for
any tissue lost during the separation or cutting of the tissue
sample from the underlying tissue in the donor material.
[0103] Any biological repair material may be sterilized to
inactivate biological contaminants such as bacteria, viruses,
yeasts, molds, mycoplasmas and parasites. Sterilization may be
performed using any suitable technique, for example radiation, such
as gamma radiation.
[0104] Any of the biological material described herein may be
harvested with use of a robotic device. The robotic device can use
information from an electronic image for tissue harvesting.
[0105] In certain embodiments, the cartilage replacement material
has a particular biochemical composition. For instance, the
biochemical composition of the cartilage surrounding a defect can
be assessed by taking tissue samples and chemical analysis or by
imaging techniques. For example, WO 02/22014 describes the use of
gadolinium for imaging of articular cartilage to monitor
glycosaminoglycan content within the cartilage. The cartilage
replacement or regenerating material can then be made or cultured
in a manner, to achieve a biochemical composition similar to that
of the cartilage surrounding the implantation site. The culture
conditions used to achieve the desired biochemical compositions can
include, for example, varying concentrations biochemical
composition of said cartilage replacement or regenerating material
can, for example, be influenced by controlling concentrations and
exposure times of certain nutrients and growth factors.
[0106] 2.3. Multiple-Component Repair Materials
[0107] The articular surface repair system may include one or more
components. Nonlimiting examples of one-component systems include a
plastic, a metal, a metal alloy or a biologic material. In certain
embodiments, the surface of the repair system facing the underlying
bone is smooth. In other embodiments, the surface of the repair
system facing the underlying bone is porous or porous-coated.
[0108] Non-limiting examples of multiple-component systems include
combinations of metal, plastic, metal alloys and one or more
biological materials. One or more components of the articular
surface repair system can be composed of a biologic material (e.g.
a tissue scaffold with cells such as cartilage cells or stem cells
alone or seeded within a substrate such as a bioresorable material
or a tissue scaffold, allograft, autograft or combinations thereof)
and/or a non-biological material (e.g., polyethylene or a chromium
alloy such as chromium cobalt).
[0109] Thus, the repair system can include one or more areas of a
single material or a combination of materials, for example, the
articular surface repair system can have a superficial and a deep
component. The superficial component is typically designed to have
size, thickness and curvature similar to that of the cartilage
tissue lost while the deep component is typically designed to have
a curvature similar to the subchondral bone. In addition, the
superficial component can have biomechanical properties similar to
articular cartilage, including but not limited to similar
elasticity and resistance to axial loading or shear forces. The
superficial and the deep component can consist of two different
metals or metal alloys. One or more components of the system (e.g.,
the deep portion) can be composed of a biologic material including,
but not limited to bone, or a non-biologic material including, but
not limited to hydroxyapatite, tantalum, a chromium alloy, chromium
cobalt or other metal alloys.
[0110] One or more regions of the articular surface repair system
(e.g., the outer margin of the superficial portion and/or the deep
portion) can be bioresorbable, for example to allow the interface
between the articular surface repair system and the patient's
normal cartilage, over time, to be filled in with hyaline or
fibrocartilage. Similarly, one or more regions (e.g., the outer
margin of the superficial portion of the articular surface repair
system and/or the deep portion) can be porous. The degree of
porosity can change throughout the porous region, linearly or
non-linearly, for where the degree of porosity will typically
decrease towards the center of the articular surface repair system.
The pores can be designed for in-growth of cartilage cells,
cartilage matrix, and connective tissue thereby achieving a smooth
interface between the articular surface repair system and the
surrounding cartilage.
[0111] The repair system (e.g., the deep component in multiple
component systems) can be attached to the patient's bone with use
of a cement-like material such as methylmethacrylate, injectable
hydroxy- or calcium-apatite materials and the like.
[0112] In certain embodiments, one or more portions of the
articular surface repair system can be pliable or liquid or
deformable at the time of implantation and can harden later.
Hardening can occur within 1 second to 2 hours (or any time period
therebetween), preferably with in 1 second to 30 minutes (or any
time period therebetween), more preferably between 1 second and 10
minutes (or any time period therebetween).
[0113] One or more components of the articular surface repair
system can be adapted to receive injections. For example, the
external surface of the articular surface repair system can have
one or more openings therein. The openings can be sized so as to
receive screws, tubing, needles or other devices which can be
inserted and advanced to the desired depth, for example through the
articular surface repair system into the marrow space. Injectables
such as methylmethacrylate and injectable hydroxy- or
calcium-apatite materials can then be introduced through the
opening (or tubing inserted therethrough) into the marrow space
thereby bonding the articular surface repair system with the marrow
space. Similarly, screws or pins can be inserted into the openings
and advanced to the underlying subchondral bone and the bone marrow
or epiphysis to achieve fixation of the articular surface repair
system to the bone. Portions or all components of the screw or pin
can be bioresorbable, for example, the distal portion of a screw
that protrudes into the marrow space can be bioresorbable. During
the initial period after the surgery, the screw can provide the
primary fixation of the articular surface repair system.
Subsequently, ingrowth of bone into a porous coated area along the
undersurface of the articular cartilage repair system can take over
as the primary stabilizer of the articular surface repair system
against the bone.
[0114] The articular surface repair system can be anchored to the
patient's bone with use of a pin or screw or other attachment
mechanism. The attachment mechanism can be bioresorbable. The screw
or pin or attachment mechanism can be inserted and advanced towards
the articular surface repair system from a non-cartilage covered
portion of the bone or from a non-weight-bearing surface of the
joint.
[0115] The interface between the articular surface repair system
and the surrounding normal cartilage can be at an angle, for
example oriented at an angle of 90 degrees relative to the
underlying subchondral bone. Suitable angles can be determined in
view of the teachings herein, and in certain cases, non-90 degree
angles may have advantages with regard to load distribution along
the interface between the articular surface repair system and the
surrounding normal cartilage.
[0116] The interface between the articular surface repair system
and the surrounding normal cartilage may be covered with a
pharmaceutical or bioactive agent, for example a material that
stimulates the biological integration of the repair system into the
normal cartilage. The surface area of the interface can be
irregular, for example, to increase exposure of the interface to
pharmaceutical or bioactive agents.
[0117] 2.4. Customized Containers
[0118] In another embodiment of the invention, a container or well
can be formed to the selected specifications, for example to match
the material needed for a particular subject or to create a stock
of repair materials in a variety of sizes. The size and shape of
the contained may be designed using the thickness and curvature
information obtained from the joint and from the cartilage defect.
More specifically, the inside of the container can be shaped to
follow any selected measurements, for example as obtained from the
cartilage defect(s) of a particular subject. The container can be
filled with a cartilage replacement or regenerating material, for
example, collagen-containing materials, plastics, bioresorbable
materials and/or any suitable tissue scaffold. The cartilage
regenerating or replacement material can also consist of a
suspension of stem cells or fetal or immature or mature cartilage
cells that subsequently develop to more mature cartilage inside the
container. Further, development and/or differentiation can be
enhanced with use of certain tissue nutrients and growth
factors.
[0119] The material is allowed to harden and/or grow inside the
container until the material has the desired traits, for example,
thickness, elasticity, hardness, biochemical composition, etc.
Molds can be generated using any suitable technique, for example
computer devices and automation, e.g. computer assisted design
(CAD) and, for example, computer assisted modeling (CAM). Because
the resulting material generally follows the contour of the inside
of the container it will better fit the defect itself and
facilitate integration.
[0120] 2.5. Shaping
[0121] In certain instances shaping of the repair material will be
required before or after formation (e.g., growth to desired
thickness), for example where the thickness of the required
cartilage material is not uniform (e.g., where different sections
of the cartilage replacement or regenerating material require
different thicknesses).
[0122] The replacement material can be shaped by any suitable
technique including, but not limited to, mechanical abrasion, laser
abrasion or ablation, radiofrequency treatment, cryoablation,
variations in exposure time and concentration of nutrients, enzymes
or growth factors and any other means suitable for influencing or
changing cartilage thickness. See, e.g., WO 00/15153; If enzymatic
digestion is used, certain sections of the cartilage replacement or
regenerating material can be exposed to higher doses of the enzyme
or can be exposed longer as a means of achieving different
thicknesses and curvatures of the cartilage replacement or
regenerating material in different sections of said material.
[0123] The material can be shaped manually and/or automatically,
for example using a device into which a pre-selected thickness
and/or curvature has been inputted and programming the device to
achieve the desired shape.
[0124] In addition to, or instead of, shaping the cartilage repair
material, the site of implantation (e.g., bone surface, any
cartilage material remaining, etc.) can also be shaped by any
suitable technique in order to enhanced integration of the repair
material.
[0125] 2.6. Pre-Existing Repair Systems
[0126] As described herein, repair systems of various sizes,
curvatures and thicknesses can be obtained. These repair systems
can be catalogued and stored to create a library of systems from
which an appropriate system can then be selected. In other words, a
defect is assessed in a particular subject and a pre-existing
repair system having the closest shape and size is selected from
the library for further manipulation (e.g., shaping) and
implantation.
[0127] 2.7. Mini-Prosthesis
[0128] As noted above, the methods and compositions described
herein can be used to replace only a portion of the articular
surface, for example, an area of diseased cartilage or lost
cartilage on the articular surface. In these systems, the articular
surface repair system may be designed to replace only the area of
diseased or lost cartilage or it can extend beyond the area of
diseased or lost cartilage, e.g., 3 or 5 mm into normal adjacent
cartilage. In certain embodiments, the prosthesis replaces less
than about 70% to 80% (or any value therebetween) of the articular
surface (e.g., any given articular surface such as a single femoral
condyle, etc.), preferably, less than about 50% to 70% (or any
value therebetween), more preferably, less than about 30% to 50%
(or any value therebetween), more preferably less than about 20% to
30% (or any value therebetween), even more preferably less than
about 20% of the articular surface.
[0129] As noted above, the prosthesis may include multiple
components, for example a component that is implanted into the bone
(e.g., a metallic device) attached to a component that is shaped to
cover the defect of the cartilage overlaying the bone. Additional
components, for example intermediate plates, meniscus repairs
systems and the like may also be included. It is contemplated that
each component replaces less than all of the corresponding
articular surface. However, each component need not replace the
same portion of the articular surface. In other words, the
prosthesis may have a bone-implanted component that replaces less
than 30% of the bone and a cartilage component that replaces 60% of
the cartilage. The prosthesis may include any combination, so long
as each component replaces less than the entire articular
surface.
[0130] The articular surface repair system may be formed or
selected so that it will achieve a near anatomic fit or match with
the surrounding or adjacent cartilage. Typically, the articular
surface repair system is formed and/or selected so that its outer
margin located at the external surface will be aligned with the
surrounding or adjacent cartilage.
[0131] Thus, the articular surface repair system can be designed to
replace only the weight-bearing portion of an articular surface,
for example in a femoral condyle. The weight-bearing surface refers
to the contact area between two opposing articular surfaces during
activities of normal daily living. At least one or more
weight-bearing portions can be replaced in this manner, e.g., on a
femoral condyle and on a tibia.
[0132] In other embodiments, an area of diseased cartilage or
cartilage loss can be identified in a weight-bearing area and only
a portion of said weight-bearing area, specifically the portion
containing said diseased cartilage or area of cartilage loss, can
be replaced with an articular surface repair system.
[0133] In certain aspects, the defect to be repaired is located
only on one articular surface, typically the most diseased surface.
For example, in a patient with severe cartilage loss in the medial
femoral condyle but less severe disease in the tibia, the articular
surface repair system can only be applied to the medial femoral
condyle. Preferably, in any methods described herein, the articular
surface repair system is designed to achieve an exact or a near
anatomic fit with the adjacent normal cartilage.
[0134] In other embodiments, more than one articular surface can be
repaired.
[0135] The area(s) of repair will be typically limited to areas of
diseased cartilage or cartilage loss or areas slightly greater than
the area of diseased cartilage or cartilage loss within the
weight-bearing surface(s).
[0136] The implant and/or the implant site can be sculpted to
achieve a near anatomic alignment between the implant and the
implant site. In another embodiment of the invention, an electronic
image is used to measure the thickness, curvature, or shape of the
articular cartilage or the subchondral bone, and/or the size of a
defect, and an articular surface repair system is selected using
this information. The articular surface repair system can be
inserted arthroscopically. The articular surface repair system can
have a single radius. More typically, however, the articular
surface repair system 1100 can have varying curvatures and radii
within the same plane, e.g. anteroposterior or mediolateral or
superoinferior or oblique planes, or within multiple planes. In
this manner, the articular surface repair system can be shaped to
achieve a near anatomic alignment between the implant and the
implant site. This design allows not even for different degrees of
convexity or concavity, but also for concave portions within a
predominantly convex shape or vice versa 1100.
[0137] If a multiple component repair material has been selected,
for example with a superficial component 1105 consisting of a
polymeric material and a deep component 1110 consisting of a metal
alloy, the superficial component can be designed so that its
thickness and curvature will closely match that of the surrounding
cartilage 1115. Thus, the superficial component can have more than
one thickness in different portions of the articular repair system.
Moreover, the superficial component can have varying curvatures and
radii within the same plane, e.g. anteroposterior or mediolateral
or superoinferior or oblique planes, or within multiple planes.
Similarly, the deep component can have varying curvatures and radii
within the same plane, e.g. anteroposterior or mediolateral or
superoinferior or oblique planes, or within multiple planes.
Typically, the curvature of the deep component will be designed to
follow that of the subchondral bone.
[0138] In another embodiment the articular surface repair system
has a fixturing stem, for example, as described in the Background
of U.S. Pat. No. 6,224,632. The fixturing stem can have different
shapes including conical, rectangular, fin among others. The mating
bone cavity is typically similarly shaped as the corresponding
stem.
[0139] In another embodiment, the articular surface repair system
can be attached to the underlying bone or bone marrow using bone
cement. Bone cement is typically made from an acrylic polymeric
material. Typically, the bone cement is comprised of two
components: a dry power component and a liquid component, which are
subsequently mixed together. The dry component generally includes
an acrylic polymer, such as polymethylmethacrylate (PMMA). The dry
component can also contain a polymerization initiator such as
benzoylperoxide, which initiates the free-radical polymerization
process that occurs when the bone cement is formed. The liquid
component, on the other hand, generally contains a liquid monomer
such as methyl methacrylate (MMA). The liquid component can also
contain an accelerator such as an amine (e.g.,
N,N-dimethyl-p-toluidine). A stabilizer, such as hydroquinone, can
also be added to the liquid component to prevent premature
polymerization of the liquid monomer. When the liquid component is
mixed with the dry component, the dry component begins to dissolve
or swell in the liquid monomer. The amine accelerator reacts with
the initiator to form free radicals that begin to link monomer
units to form polymer chains. In the next two to four minutes, the
polymerization process proceeds changing the viscosity of the
mixture from a syrup-like consistency (low viscosity) into a
dough-like consistency (high viscosity). Ultimately, further
polymerization and curing occur, causing the cement to harden and
affix a prosthesis to a bone.
[0140] In certain aspects of the invention, bone cement 955 or
another liquid attachment material such as injectable
calciumhydroxyapatite can be injected into the marrow cavity
through one or more openings 950 in the prosthesis. These openings
in the prosthesis can extend from the articular surface to the
undersurface of the prosthesis 960. After injection, the openings
can be closed with a polymer, silicon, metal, metal alloy or
bioresorbable plug.
[0141] In another embodiment, one or more components of the
articular surface repair (e.g., the surface of the system that is
pointing towards the underlying bone or bone marrow) can be porous
or porous coated. A variety of different porous metal coatings have
been proposed for enhancing fixation of a metallic prosthesis by
bone tissue ingrowth. Thus, for example, U.S. Pat. No. 3,855,638
discloses a surgical prosthetic device, which may be used as a bone
prosthesis, comprising a composite structure consisting of a solid
metallic material substrate and a porous coating of the same solid
metallic material adhered to and extending over at least a portion
of the surface of the substrate. The porous coating consists of a
plurality of small discrete particles of metallic material bonded
together at their points of contact with each other to define a
plurality of connected interstitial pores in the coating. The size
and spacing of the particles, which can be distributed in a
plurality of monolayers, can be such that the average interstitial
pore size is not more than about 200 microns. Additionally, the
pore size distribution can be substantially uniform from the
substrate-coating interface to the surface of the coating.
[0142] In another embodiment, the articular surface repair system
can contain one or more polymeric materials that can be loaded with
and release therapeutic agents including drugs or other
pharmacological treatments that can be used for drug delivery. The
polymeric materials can, for example, be placed inside areas of
porous coating. The polymeric materials can be used to release
therapeutic drugs, e.g. bone or cartilage growth stimulating drugs.
This embodiment can be combined with other embodiments, wherein
portions of the articular surface repair system can be
bioresorbable. For example, the superficial layer of an articular
surface repair system or portions of its superficial layer can be
bioresorbable. As the superficial layer gets increasingly resorbed,
local release of a cartilage growth-stimulating drug can facilitate
ingrowth of cartilage cells and matrix formation.
[0143] In any of the methods or compositions described herein, the
articular surface repair system can be pre-manufactured with a
range of sizes, curvatures and thicknesses. Alternatively, the
articular surface repair system can be custom-made for an
individual patient.
[0144] 3. Implantation
[0145] Following one or more manipulations (e.g., shaping, growth,
development, etc), the cartilage replacement or regenerating
material can then be implanted into the area of the defect.
Implantation can be performed with the cartilage replacement or
regenerating material still attached to the base material or
removed from the base material. Any suitable methods and devices
may be used for implantation, for example, devices as described in
U.S. Pat. Nos. 6,375,658; 6,358,253; 6,328,765; and International
Publication WO 01/19254.
[0146] In selected cartilage defects, the implantation site can be
prepared with a single cut across the articular surface (FIG. 10).
In this case, single 1010 and multi-component 1020 prostheses can
be utilized.
[0147] Further, implantation can be facilitated by using a device
applied to the outer surface of the articular cartilage in order to
match the alignment of the donor tissue and the recipient site. The
device can be round, circular, oval, ellipsoid, curved or irregular
in shape. The shape is typically selected or adjusted to match or
enclose an area of diseased cartilage or an area slightly larger
than the area of diseased cartilage. The inner aspect of the
circle, oval, ellipse, curved or irregular shape can be open or
hollow. Thus, a rounded or curved joint surface such as a femoral
condyle, a femoral head or a humeral head can protrude through the
opening or the hollow portion. The device can include a slit
through which a blade can be introduced. Alternatively, the device
can include a blade holding mechanism or the blade can be
integrated in the device. A variety of materials can be employed,
for example plastic (e.g., disposable, re-usable and/or
sterilizable) devices. In addition, translucent materials may be
used, for example in order to achieve an improved match between the
donor tissue and the recipient site.
[0148] The device can be used to remove an area of diseased
cartilage and underlying bone or an area slightly larger than the
diseased cartilage and underlying bone. In addition, the device can
be used on a "donor", e.g. a cadaveric specimen to obtain
implantable repair material. The device is typically positioned in
the same general anatomic area in which the tissue was removed in
the recipient. The shape of the device is then used to identify a
donor site providing a seamless or near seamless match between the
donor tissue sample and the recipient site. This is achieved by
identifying the position of the device in which the articular
surface in the donor, e.g. a cadaveric specimen has a seamless or
near seamless contact with the inner surface when applied to the
cartilage.
[0149] The device can be molded, machined or formed based on the
size of the area of diseased cartilage and based on the curvature
of the cartilage or the underlying subchondral bone or a
combination of both. The device can then be applied to the donor,
(e.g., a cadaveric specimen) and the donor tissue can be obtained
with use of a blade or saw or other tissue cutting device. The
device can then be applied to the recipient in the area of the
diseased cartilage and the diseased cartilage and underlying bone
can be removed with use of a blade or saw or other tissue cutting
device whereby the size and shape of the removed tissue containing
the diseased cartilage will closely resemble the size and shape of
the donor tissue. The donor tissue can then be attached to the
recipient site. For example, said attachment can be achieved with
use of screws or pins (e.g., metallic, non-metallic or
bioresorable) or other fixation means including but not limited to
a tissue adhesive. Attachment can be through the cartilage surface
or alternatively, through the marrow space.
[0150] The implant site can be prepared with use of a robotic
device. The robotic device can use information from an electronic
image for preparing the recipient site.
* * * * *