U.S. patent application number 10/413028 was filed with the patent office on 2004-02-05 for spacerless artificial disc replacements.
Invention is credited to Ferree, Bret A., Thompkins, David.
Application Number | 20040024462 10/413028 |
Document ID | / |
Family ID | 38997908 |
Filed Date | 2004-02-05 |
United States Patent
Application |
20040024462 |
Kind Code |
A1 |
Ferree, Bret A. ; et
al. |
February 5, 2004 |
Spacerless artificial disc replacements
Abstract
Spacerless artificial disc replacements (ADRs) are disclosed.
One preferred embodiment includes two saddle-shaped components to
facilitate more normal spinal flexion, extension, and lateral
bending while limit axial rotation, thereby protecting the facet
joints and the annulus fibrosus (AF). Either or both the superior
and inferior components are made of a hard material such as chrome
cobalt, titanium, or a ceramic including alumina, zirconia, or
calcium phosphate. The articulating surfaces of the ADR are also
preferably highly polished to reduce friction between the
components. Metals, alloys or other materials with shape-memory
characteristics may also prove beneficial.
Inventors: |
Ferree, Bret A.;
(Cincinnati, OH) ; Thompkins, David; (Milford,
OH) |
Correspondence
Address: |
John G. Posa
Gifford, Krass, Groh, Sprinkle,
Anderson & Citkowski, P.C.
280 N. Old Woodward Ave., Suite 400
Birmingham
MI
48009-5394
US
|
Family ID: |
38997908 |
Appl. No.: |
10/413028 |
Filed: |
April 14, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60372520 |
Apr 12, 2002 |
|
|
|
Current U.S.
Class: |
623/17.14 ;
623/17.11 |
Current CPC
Class: |
A61F 2210/0014 20130101;
A61F 2002/30301 20130101; A61F 2002/30934 20130101; A61F 2002/30884
20130101; A61F 2310/00203 20130101; A61F 2/4425 20130101; A61F
2002/30092 20130101; A61F 2002/30528 20130101; A61L 2430/38
20130101; A61F 2/30767 20130101; A61F 2310/00239 20130101; A61F
2230/0095 20130101; A61F 2310/00023 20130101; A61F 2310/00029
20130101; A61F 2002/302 20130101; A61F 2310/00293 20130101; A61F
2/442 20130101; A61F 2002/30878 20130101; A61F 2220/0025 20130101;
A61F 2310/00011 20130101; A61L 27/10 20130101; A61F 2002/4631
20130101; A61L 27/04 20130101 |
Class at
Publication: |
623/17.14 ;
623/17.11 |
International
Class: |
A61F 002/44 |
Claims
We claim:
1. An artificial disc replacement (ADR), comprising: an inferior
component; a superior component; and a smooth, continuous interface
between the inferior component and superior components, the
interface including at least one convex surface articulating with
at a corresponding concave surface.
2. The ADR of claim 1, wherein both components are metallic or
ceramic.
3. The ADR of claim 1, wherein the components are physically
configured to facilitate flexion, extension, and lateral bending
while limiting axial rotation.
4. The ADR of claim 1, wherein the components are
saddle-shaped.
5. The ADR of claim 1, wherein the vertebral surfaces of one or
both of the components are treated to promote bone ingrowth.
6. The ADR of claim 1, wherein one or both of the components are
cemented to a respective vertebral endplate.
7. The ADR of claim 1, wherein one or both of the components
include projections adapted to fit into a respective vertebral
endplate.
8. The ADR of claim 1, wherein one the components is made of
polyethylene.
Description
REFERENCE TO RELATED APPLICATION
[0001] This application claims priority from U.S. Provisional
Patent Application Serial No. 60/372,520, filed Apr. 12, 2002, the
entire content of which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] This invention relates generally to artificial disc
replacements (ADRs) and, more particularly, to devices that operate
without softer spacer materials such as polyethylene.
BACKGROUND OF THE INVENTION
[0003] Polyethylene spacers are common in some artificial joint
situations, including total knee replacements (TKRs). Polyethylene
spacers are also used between metal plates in many artificial disc
replacement (ADR) designs.
[0004] Complications arising from poly debris are well documented,
however, including fracture of the spacer once it becomes too thin,
absorption and migration of poly particles throughout the body, and
loosening of the bone metal junction as a reaction of the poly
debris.
[0005] Metal-on-metal and ceramic-on-metal surfaces have much lower
wear characteristics. In fact, metal-on-metal surfaces demonstrate
400 times less wear than polyethylene on metal surfaces.
[0006] While there have been attempts to limit the use of poly in
ADR designs, all existing approaches constitute ball-and-socket
configurations which do not inherently limit axial rotation.
Instead, axial rotation is limited through the use of multiple
ball-and-socket joints or an elongated ball-and-socket joint, which
complicates the design.
SUMMARY OF THE INVENTION
[0007] The present invention replaces polyethylene artificial disc
replacement (ADR) spacers with harder, more wear-resistant
materials. In the preferred embodiments, an ADR according to the
invention includes opposing saddle-shaped components to facilitate
more normal spinal flexion, extension, and lateral bending.
Preferably, the ADR allows at least 10 degrees of movement in the
flexion to extension direction and at least 5 degrees of movement
in the lateral bending direction. The saddle-shaped articulating
surfaces also limit axial rotation, thereby protecting the facet
joints and the annulus fibrosus (AF).
[0008] According to the invention, either or both the superior and
inferior components are made of a hard material such as chrome
cobalt, titanium, or a ceramic including alumina, zirconia, or
calcium phosphate. The articulating surfaces of the ADR are also
preferably highly polished to reduce friction between the
components. Metals, alloys or other materials with shape-memory
characteristics may also prove beneficial.
[0009] The vertebral surfaces of the components may be treated to
promote bone ingrowth. For example, the vertebral surfaces of the
components may have plasma spray or beads. Alternatively, one or
both components may be cemented to the vertebrae. The
vertebra-facing surfaces may also include projections such as keels
that fit into the vertebrae. In embodiments adapted for
cementation, one of the components could be made of polyethylene or
other softer material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1A is an anterior view of an ADR according to the
invention;
[0011] FIG. 1B is a lateral view of the ADR of FIG. 1;
[0012] FIG. 1C is an oblique view of the ADR of FIG. 1;
[0013] FIG. 2A is a view of the anterior aspect of an alternative
embodiment of the ADR;
[0014] FIG. 2B is a view of the lateral aspect of an alternative
embodiment of the ADR shown in FIG. 2B;
[0015] FIG. 3A is a view of the anterior aspect of an alternative,
less constrained, embodiment of the saddle-shaped ADR shown in a
fully flexed position;
[0016] FIG. 3B is a view of the lateral aspect of the embodiment of
the ADR shown in FIG. 3A;
[0017] FIG. 4A is a view of the lateral aspect of another
embodiment of a saddle-shaped ADR;
[0018] FIG. 4B is a view of the anterior aspect of the embodiment
of the ADR shown in FIG. 4A in a fully flexed position;
[0019] FIG. 4C is a view of the anterior aspect of an alternative
embodiment;
[0020] FIG. 4D is a view of the anterior aspect of the ADR shown in
FIG. 4A; and
[0021] FIG. 4E is a view of the anterior aspect of the ADR shown in
FIG. 4A
DETAILED DESCRIPTION OF THE INVENTION
[0022] FIG. 1A is an anterior view of an ADR according to the
invention. FIG. 1B is a lateral view of the ADR of FIG. 1. FIG. 1C
is an oblique view of the ADR of FIG. 1.
[0023] FIG. 2A is a view of the anterior aspect of an alternative
embodiment of the ADR, wherein the articulating surfaces of both
components have a flat area centrally from the front to the back of
the ADR. FIG. 2B is a view of the lateral aspect of an alternative
embodiment of the ADR drawn in FIG. 2B. The flat area of the
articulating surfaces courses centrally from side of the ADR to the
other side. The flat area allows one component to translate
slightly on the other component. Alternatively, a curved area with
a large radius could replace the flat area.
[0024] FIG. 3A is a view of the anterior aspect of an alternative,
less constrained, embodiment of the saddle-shaped ADR drawn in a
fully flexed position. The less constrained embodiment facilitates
spinal flexion, extension, and lateral bending. FIG. 3B is a view
of the lateral aspect of the embodiment of the ADR drawn in FIG.
3A.
[0025] FIG. 4A is a view of the lateral aspect of another
embodiment of a saddle-shaped ADR. The center of rotation for
flexion and extension is not necessarily located in the center of
the ADR. For example, the center of rotation is preferably located
in the posterior half of the ADR. FIG. 4B is a view of the anterior
aspect of the embodiment of the ADR drawn in FIG. 4A, drawn in a
fully flexed position.
[0026] FIG. 4C is a view of the anterior aspect of an alternative
embodiment, showing how the radius of curvature of the articulation
for lateral bending may be different than the radius of curvature
for articulation for flexion and extension. For example, the radius
of curvature for the articulation for flexion and extension, as
seen in FIG. 4A, may be smaller than the radius of curvature for
the articulation for lateral bending, as seen in FIG. 4C.
Articulating surfaces with smaller radii, facilitate movement.
Thus, the embodiment of the ADR drawn in FIG. 4A flexes and extends
more easily than the embodiment of the ADR drawn in FIG. 3A. The
ADR is drawn in a fully flexed position.
[0027] FIG. 4D is a view of the anterior aspect of the ADR drawn in
FIG. 4A. The ADR is drawn in a neutral position. The area of the
drawing with diagonal lines represents the articulating surface of
the lower ADR component. FIG. 4E is a view of the anterior aspect
of the ADR drawn in FIG. 4A, also drawn in a fully extended
position.
* * * * *