U.S. patent application number 10/653540 was filed with the patent office on 2004-11-11 for artificial intervertebral disc.
Invention is credited to Richelsoph, Marc.
Application Number | 20040225363 10/653540 |
Document ID | / |
Family ID | 32990525 |
Filed Date | 2004-11-11 |
United States Patent
Application |
20040225363 |
Kind Code |
A1 |
Richelsoph, Marc |
November 11, 2004 |
Artificial intervertebral disc
Abstract
An artificial intervertebral disc including a housing having
spaced inner surfaces facing each other and oppositely facing outer
surfaces for engaging spaced apart intervertebral surfaces and a
self-adjusting bearing operatively disposed between the inner
surfaces of the housing for moving relative to the housing members
to adjust and compensate for vertebral disc motion. Also provided
is a mobile bearing including a self-adjusting bearing operatively
disposed between the inner surfaces of the housing for moving
relative to the housing members to adjust and compensate for
movement of the housing. A method for posteriorly inserting an
artificial disc assembly by inserting at least two artificial disc
assemblies around a spine and into an intervertebral space.
Inventors: |
Richelsoph, Marc; (Bartlett,
TN) |
Correspondence
Address: |
Kohn & Associates, PLLC
Suite 410
30500 Northwestern Highway
Farmington Hills
MI
48334
US
|
Family ID: |
32990525 |
Appl. No.: |
10/653540 |
Filed: |
September 2, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10653540 |
Sep 2, 2003 |
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10430861 |
May 6, 2003 |
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Current U.S.
Class: |
623/17.13 |
Current CPC
Class: |
A61F 2310/00796
20130101; A61F 2220/005 20130101; A61F 2310/00179 20130101; A61F
2220/0025 20130101; A61F 2002/2817 20130101; A61F 2002/30904
20130101; A61F 2002/305 20130101; A61F 2002/30578 20130101; A61F
2002/30604 20130101; A61F 2002/30616 20130101; A61F 2310/00029
20130101; A61F 2002/30014 20130101; A61F 2/4425 20130101; A61F
2002/30649 20130101; A61F 2310/00023 20130101; A61F 2002/30383
20130101; A61F 2002/30884 20130101; A61F 2002/30448 20130101; A61F
2002/30563 20130101; A61F 2220/0033 20130101; A61F 2250/0018
20130101; A61F 2002/30332 20130101; A61F 2002/30426 20130101; A61F
2002/30841 20130101; A61F 2/30767 20130101; A61F 2002/30662
20130101; A61F 2002/443 20130101; A61F 2002/30495 20130101 |
Class at
Publication: |
623/017.13 |
International
Class: |
A61F 002/44 |
Claims
What is claimed is:
1. An artificial intervertebral disc comprising: housing members
including spaced inner surfaces facing each other and oppositely
facing outer surfaces for engaging spaced apart intervertebral
surfaces; and self-adjusting bearing means operatively disposed
between said inner surfaces for moving relative to said housing
members to adjust and compensate for vertebral disc motion.
2. The disc according to claim 1, wherein said inner surfaces
include at least one slot within each of said inner surfaces for
seating said self-adjusting bearing means therein and allowing
movement of said self-adjusting bearing means.
3. The disc according to claim 2, wherein said slot includes outer
walls defining the size of said slot and receiving means inside
said slot, said receiving means for receiving and containing said
bearing means therein.
4. The disc according to claim 3, wherein said receiving means
includes a seat portion integral within said housing.
5. The disc according to claim 2, wherein said slot is in a shape
selected from the group consisting essentially of a circle, an
oval, and other round-sided shapes.
6. The disc according to claim 1, wherein said housing members are
constructed from a composition selected from the group consisting
essentially of metals, ceramics, and plastics.
7. The disc according to claim 6, wherein said housing members
include an outer surface having a surface texture for accepting
bone growth therein.
8. The disc according to claim 7, wherein said surface texture is
selected from the group consisting essentially of physically
roughened, porous coated, and plasma coated surfaces.
9. The disc according to claim 3, wherein said receiving means is a
removable insert.
10. The disc according to claim 9, wherein said insert includes
outer walls defining a size of said insert and a seat for receiving
and containing said bearing means therein.
11. The disc according to claim 10, wherein said insert is in a
shape selected from the group consisting essentially of a circle,
an oval, and other round-sided shapes.
12. The disc according to claim 9, wherein said insert is
constructed from a composition selected from the group consisting
essentially of metals, ceramics, and plastics.
13. The disc according to claim 1, wherein said bearing means is
constructed from a composition selected from the group consisting
essentially of metals, ceramics, and plastics.
14. The disc according to claim 1, further including load sharing
means disposed between said inner surfaces and about at least a
portion of said bearing means for sharing absorption of compressive
loads with said bearing means while limiting the relative movement
of said housing members.
15. The disc according to claim 14, wherein said load sharing means
includes at least one pad member disposed and retained between said
inner surfaces of said housing members and having cushioning and
elastic properties for countering and thereby self centering
against forces caused by relative movement of said housing member
while under compressive forces are applied to said outer surfaces
of said housing members.
16. The disc member according to claim 15, wherein said pad members
are made from a composition selected from the group consisting
essentially of polymers and elastomers.
17. The disc member according to claim 16, wherein said pad members
are made from a composition selected from the group consisting
essentially of silicone, polyurethane, urethane composites,
plastics, polymers, and elastomers.
18. The disc according to claim 15, wherein said housing members
includes seating means for seating said pad members between said
inner surfaces.
19. The disc according to claim 18, wherein said seating means
includes at least one pocket recessed into said inner surface of
said housing members for seating a portion of said pad member
therein.
20. The disc according to claim 19, further including adhering
means for fixedly adhering said pad member within said pocket.
21. A mobile bearing comprising self-adjusting bearing means
operatively disposed between inner surfaces of a housing for moving
relative to said housing to adjust and compensate for motion of the
housing.
22. The mobile bearing according to claim 21, wherein said inner
surfaces include at least one slot within each of said inner
surfaces for seating said self-adjusting bearing means therein and
allowing movement of said self-adjusting bearing means.
23. The mobile bearing according to claim 22, wherein said slot
includes outer walls defining a size of said slot and receiving
means inside said slot for receiving and containing said bearing
means therein.
24. The mobile bearing according to claim 23, wherein said
receiving means includes a seat portion integral with said
housing.
25. The mobile bearing according to claim 22, wherein said slot is
in a shape selected from the group consisting essentially of a
circle, an oval, and other round-sided shapes.
26. The mobile bearing according to claim 23, wherein said
receiving means is a removable insert.
27. The mobile bearing according to claim 26, wherein said insert
includes outer walls defining a size of said insert and a seat
portion integral with said insert for containing said bearing means
therein.
28. The mobile bearing according to claim 27, wherein said insert
is in a shape selected from the group consisting essentially of a
circle, an oval, and other round-sided shapes.
29. The mobile bearing according to claim 26, wherein said insert
is constructed from a composition selected from the group
consisting essentially of metals, ceramics, and plastics.
30. The mobile bearing according to claim 21, wherein said bearing
means is constructed from a composition selected from the group
consisting essentially of metals, ceramics, and plastics.
31. The mobile bearing according to claim 21, further including
load sharing means disposed between said inner surfaces and about
at least a portion of said bearing means for sharing absorption of
compressive loads with said bearing means while limiting the
relative movement of said housing.
32. A method of automatically adjusting support of a housing by
floating a mobile bearing within the housing for automatically
adjusting for motion of the housing and providing support relative
to the motion.
33. The method according to claim 32, wherein said floating step
includes moving the bearing into a slot within the housing.
34. The method according to claim 33, further including limiting
the motion of the bearing by altering the dimensions of the slot to
conform to the desired range of motion.
35. An artificial intervertebral disc comprising: housing members
including spaced inner surfaces facing each other and oppositely
facing outer surfaces for engaging spaced apart intervertebral
surfaces; self-adjusting bearing means operatively disposed between
said inner surfaces for moving relative to said housing members to
adjust and compensate for vertebral disc motion; self-centering
means for automatically centering said self-adjusting bearing means
within said housing members.
36. The disc according to claim 35, wherein said self-centering
means are load sharing means disposed between said inner surfaces
and about at least a portion of said bearing means for sharing
absorption of compressive loads with said bearing means while
limiting the relative movement of said housing members and
self-centering said bearing means.
37. A method of adjusting support of a housing by centering a
mobile bearing within the housing for automatically adjusting for
motion of the housing and providing support relative to the
motion.
38. An artificial joint comprising: housing members including
spaced inner surfaces facing each other and oppositely facing outer
surfaces for engaging spaced apart intervertebral surfaces;
self-adjusting bearing means operatively disposed between said
inner surfaces for moving relative to said housing members to
adjust and compensate for vertebral disc motion; and self-centering
means for automatically centering said self-adjusting bearing means
within said housing members.
39. The joint according to claim 38, wherein said self-centering
means are load sharing means disposed between said inner surfaces
and about at least a portion of said bearing means for sharing
absorption of compressive loads with said bearing means while
limiting the relative movement of said housing members and
self-centering said bearing means.
40. An artificial intervertebral disc comprising: housing members
including spaced inner surfaces facing each other and oppositely
facing outer surfaces for engaging spaced apart intervertebral
surfaces; self-adjusting bearing means operatively disposed between
said inner surfaces for moving relative to said housing members to
adjust and compensate for vertebral disc motion; and said inner
surfaces include at least one slot within each of said inner
surfaces for seating said self-adjusting bearing means therein and
allowing movement of said self-adjusting bearing means.
41. The disc according to claim 41, wherein said bearing includes a
convex surface.
42. The disc according to claim 41, wherein said bearing includes a
concave surface.
43. The disc according to claim 41, wherein said bearing includes a
spherical surface.
44. The disc according to claim 40, wherein said bearing means
includes arm means for maintaining said bearing within said
slot.
45. The disc according to claim 40, further including bumper means
for maintaining said bearing in alignment within said housing, said
bumper means in sliding engagement with said slot.
46. A method for posteriorly inserting an artificial disc assembly
by inserting at least two artificial disc assemblies around a spine
and into an intervertebral space.
47. The method according to claim 46, wherein said inserting step
includes inserting each of the assemblies about a side of the spine
into opposite sides of the intervertebral space.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This patent application is a Continuation-In-Part
application of U.S. patent application Ser. No. 10/430,861, filed
May 6, 2003, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] The present invention relates generally to a spinal implant
assembly for implantation into the intervertebral space between
adjacent vertebral bones to provide stabilization and continued
postoperative flexibility and proper anatomical motion. More
specifically, the present invention relates to an artificial
intervertebral disc, sometimes referred to as an intervertebral
spacer device, for functioning as a load sharing and bearing device
for replacement of the damaged, decayed, or otherwise
nonfunctioning intervertebral disc.
[0004] 2. Background of the Invention
[0005] The spine is a complex structure consisting of multiple
flexible levels. Each level consists of a system of joints defined
by adjacent vertebral bones. The system of joints includes
intervertebral discs, which are a two-part structure. The disc
consists of a nucleus and an annulus. The system allows motion
while the facet joints add posterior stabilization to the spinal
column. The disc allows motion and cushioning to the joint.
[0006] The complex system of the joint is subjected to varying
loads and problems over time, including disc degeneration due to a
variety of reasons. Disc degeneration can be attributed to aging,
damage due to excessive loading, trauma, and other anatomical
issues. Facet joints of the structure can be compromised due to the
same reasons, as well as due to arthritic changes. Severe joint
degeneration and failure can often cause sufficient pain to require
surgical intervention.
[0007] The current standard method of treatment for severe pain
caused by spine joint problems is fusion at the damaged level of
the spine. The treatment, when successful, fuses the damaged
section into a single mass of bone. The fusion of the joint
eliminates motion of the joint, thereby reducing or eliminating
pain at that level. Success rates for pain elimination are very
high for this method of treatment. However, since the entire spine
works as a system, fusion results in complications.
[0008] Elimination of motion at the spine alters the biomechanics
of the spine at every other level. If one level is fused, then
loads are absorbed by one less disc into a system not designed for
such change. Thus, the remaining discs must redistribute loads,
each disc absorbing a greater load. In addition, the spine flexes
to absorb loads. A fusion alters the means by which the spine
flexes, which also increases the loads on the remaining healthy
discs. In turn, it is well understood that a complication of fusion
is that additional fusions may be required in the future as the
other discs deteriorate due to the altered biomechanics of the
spine. In other words, short-term pain relief is exchanged for
long-term alterations of the spine, which, in turn, usually require
further surgery.
[0009] There are numerous prior art patents addressing the issue of
disc replacement. The U.S. Pat. Nos. 6,443,987 B1 and 6,001,130,
both to Bryan, disclose polymer composite structures for cushioning
intervertebral loads. The U.S. Pat. Nos. 5,258,031 to Salib, et al.
and U.S. Pat. No. 5,314,477 to Marnay disclose ball and socket type
implants addressing the issue of intervertebral mobility. These
patents are exemplary of a first approach using an elastomer as a
motion and dampening structure and a second approach utilizing a
ball and socket joint to create a moving pivot joint. There are
many variations on these concepts, which include mechanical springs
and more complex structural mechanisms. A significant portion of
the prior art addresses the issues of intervertebral motion but do
not address anatomical loading considerations.
[0010] The current state of prior art artificial intervertebral
discs are associated with various problems. For example, a number
of implants constructed from polymers are of insufficient strength
to work effectively in the higher loading areas, such as the lumbar
spine. Such polymers often take compressive sets so that the
original height of the implant decreases over time. A surgeon must
either compensate for the compression by initially using a larger
polymer prosthesis and estimate compression or use the
appropriately sized polymer prosthesis and later surgically replace
the same once the irreversible compression of the prosthesis is
unacceptable.
[0011] Implants constructed with ball and socket joints severely
restrict or eliminate shock cushioning effect of a normal disc.
This implant can provide motion, but biomechanically, the ball and
socket joint negatively affects other healthy discs of the spine.
The result can be long-term problems at other levels of the spine,
as seen with the current treatment of fusion.
[0012] Other implants, not discussed above, utilize bearing
surfaces usually having polyethylene bearing against metal
interfaces. Polyethylene as a bearing surface is problematic in
large joint replacement due to the wear properties of the material.
Since artificial discs are intended to be implanted over long
periods of time, such wear can be highly damaging to surrounding
tissue and bone.
[0013] In view of the above, it is desirable to provide a solution
to intervertebral disc replacement that restores motion to the
damaged natural disc area while allowing for motion as well as
cushioning and dampening, similar to the naturally occurring disc.
In addition, it is preferable to allow such motion, cushioning, and
dampening while preventing a polymer or elastomeric material from
experiencing the relatively high compressive loads seen in the
spine. It is also preferable to allow a bearing surface to share
the spinal loads with the polymer and elastomeric material.
Finally, it is preferable to control changes to the artificial
motion intraoperatively to adjust for anatomical conditions.
SUMMARY OF THE INVENTION
[0014] According to the present invention, there is provided an
artificial intervertebral disc including a housing having spaced
inner surfaces facing each other and oppositely facing outer
surfaces for engaging spaced apart intervertebral surfaces and a
self-adjusting bearing operatively disposed between the inner
surfaces of the housing for moving relative to the housing members
to adjust and compensate for vertebral disc motion. Also provided
is a mobile bearing including a self-adjusting bearing operatively
disposed between the inner surfaces of the housing for moving
relative to the housing members to adjust and compensate for
movement of the housing. A method for posteriorly inserting an
artificial disc assembly by inserting at least two artificial disc
assemblies around a spine and into an intervertebral space.
DESCRIPTION OF DRAWINGS
[0015] Other advantages of the present invention can be readily
appreciated as the same becomes better understood by reference to
the following detailed description when considered in connection
with the accompanying drawings wherein:
[0016] FIG. 1 is a side perspective view of a preferred embodiment
of the present invention;
[0017] FIG. 2 is a side exploded view of the embodiment shown in
FIG. 1;
[0018] FIG. 3 is a side perspective view of a second embodiment of
the present invention;
[0019] FIG. 4 is a perspective view of a lower disc constructed in
accordance with the present invention;
[0020] FIG. 5 is a side view of an upper disc constructed in
accordance with the present invention;
[0021] FIG. 6 is a top perspective view of an upper housing member
made in accordance with the present invention;
[0022] FIG. 7 is a top plan view of a lower housing member made in
accordance with the present invention;
[0023] FIG. 8 is a side perspective view of a third embodiment of
the present invention;
[0024] FIG. 9 is a perspective view of the present invention with
the top housing member removed;
[0025] FIG. 10 is a perspective view of an alternative pad
configuration of the present invention;
[0026] FIG. 11 is a perspective view of a further alternative
embodiment of the pad member;
[0027] FIG. 12 is a further alternative embodiment of the present
invention;
[0028] FIG. 13 is an exploded side perspective view of the
embodiment shown in FIG. 12;
[0029] FIG. 14 shows an alternative embodiment of the housing
members of the present invention;
[0030] FIG. 15 shows a further alternative embodiment of the
housing members of the present invention;
[0031] FIG. 16 is an exploded view of a further embodiment of the
present invention demonstrating a bayonet type locking of a disc
member to a housing member;
[0032] FIG. 17 is a perspective view of the disc member utilizing
the bayonet locking mechanism to lock the disc member within a
housing member;
[0033] FIG. 18 is an exploded view of a disc member and housing
member showing a further embodiment of a locking mechanism for
locking the disc member within the housing member;
[0034] FIG. 19 is a perspective view showing the disc member locked
within the housing member;
[0035] FIG. 20 is a perspective view of the a further embodiment of
the housing member;
[0036] FIG. 21 is a cross sectional view taken along line 21-21 in
FIG. 20;
[0037] FIG. 22 is a perspective view of a load sharing pad member
including flanges for locking engagement in the recesses of the
housing member shown in FIGS. 20 and 21;
[0038] FIG. 23 shows a further embodiment of a locking mechanism
made in accordance with the present invention;
[0039] FIG. 24 is a top view of the mobile bearing of the present
invention;
[0040] FIG. 25 is a top view of the artificial disc including a
mobile bearing with no load sharing pads;
[0041] FIG. 26 is a top view of the multidirectional mobile bearing
of the present invention;
[0042] FIGS. 27A and B are side views of the mobile bearing of the
present invention;
[0043] FIG. 28 is a side perspective view of the mobile bearing of
the present invention resting in a seat;
[0044] FIG. 29 is a top perspective view of the seat and bearing
combination in a housing having recesses for load sharing pads;
[0045] FIG. 30 is a side perspective view of a third embodiment of
the present invention;
[0046] FIG. 31 is a perspective view of the base plate of a third
embodiment of the present invention;
[0047] FIG. 32 is a side view of a third embodiment of the lower
housing of the present invention;
[0048] FIG. 33 is a perspective view of the third embodiment of the
present invention wherein a spherical surface is incorporated on
the bearing;
[0049] FIG. 34 is a perspective view of the third embodiment of the
present invention wherein a spherical surface is incorporated on
the bearing;
[0050] FIG. 35 is a side view of the third embodiment of the
present invention;
[0051] FIG. 36 is a side view of the third embodiment of the
present invention;
[0052] FIG. 37 is a side perspective view of an alternative
embodiment of the present invention;
[0053] FIG. 38 is a perspective view of the base plate of the third
embodiment of the present invention wherein the bearing is either
convex or concave;
[0054] FIG. 39 is a perspective view of the base plate of the third
embodiment of the present invention wherein the bearing is either
convex or concave; and
[0055] FIG. 40 is a top perspective view of the bumpers of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0056] An artificial intervertebral disc constructed in accordance
with the present invention is generally shown at 10 in the Figures.
Like structures of various embodiments are indicated by primed
numerals in the Figures. The invention is an artificial
intervertebral disc, sometimes referred to by other terminology in
the prior art such as intervertebral spacer device, or spinal disc
for replacement of a damaged disc in the spine. The invention
restores motion to the damaged natural disc that allows for motion
as well as cushioning and dampening. As described below in more
detail, the present invention also allows changes to the artificial
disc motion intraoperatively to adjust for specific anatomical
conditions.
[0057] Referring to the Figures, the disc 10 includes an upper
housing member generally shown at 12 and a lower housing member
generally shown at 14. The housing members 12, 14 include spaced
inner surfaces 16 and 18 facing each other and oppositely facing
outer surfaces 20, 22 for engaging spaced apart vertebral surfaces.
A pair of bearing surfaces 24, 26 extend from each of the inner
surfaces 16, 18 for engaging each other while allowing for low
friction and compression resistant movement of the housing members
12, 14 relative to each other while under compression. As shown in
the various Figures, the bearing surfaces are integral with disc
members 28, 30. The housing members 12, 14 can be made from various
materials including metals, such as titanium, as well as ceramics,
and plastics. If integral with the bearing surfaces 24, 26, the
housing members 12, 14 can be made from the preferred material for
the bearing discs 28, 30 as discussed above. Based on this
teaching, various other configurations can be made by those skilled
in the art incorporating the present invention.
[0058] The upper and lower bearing surfaces 24, 26 engage each
other when disposed correctly opposite each other. The
configuration creates a three-dimensional bearing surface. As
discussed below, the bearing surfaces 24, 26 are disposed on
non-compressible discs or the like, thereby providing structure for
absorbing compressive loads placed on the outer surfaces 20, 22 of
the housing members 12,14.
[0059] The bearing surfaces 24, 26 preferably form a mobile bearing
23 that is capable of automatically adjusting the position of the
bearing 23 within a housing 14 as needed. The mobile bearing 23 is
shown in FIGS. 24 through 29. The bearing 23 is preferably made of
any material that slides along the surface of the housing 14 in
which it is placed, with minimal to no wear, on either the bearing
23 or the housing 14. Examples of such materials include ceramic,
metal, or other suitable materials that do not negatively react
with the housing 14.
[0060] The bearing 23 of the present invention is disposed within a
slot 35 of a housing 14. The bearing 23 is able to freely move or
float within the slot 35 in response to movement of the housing 14.
The bearing 23 is designed to provide proper cushioning and support
of the housing 14 as is required by the specific system in which
the bearing 23 is placed. The bearing can be used in any joint for
providing proper support of the joint. For example, if the bearing
23 is used in an artificial intervertebral disc assembly, the
bearing 23 provides cushioning so as to prevent the plates that are
housing the disc from touching and wearing on one another. When the
bearing 23 is utilized within the knee, the bearing also provides
cushioning for the housing 14 during movement of the housing
14.
[0061] The bearing 23 disclosed herein can move freely under load
conditions while maximizing the contact area of the upper and lower
bearing surfaces 20, 24. In other words, within the slot 35 that
the bearing 23 is disposed, the bearing 23 can move in any
direction necessary to provide the proper support for the housing
14. The bearing 23 is able to move in this manner because the
bearing 23 is a floating bearing, thus it is not attached or
affixed to the housing 14 in which it is placed. Instead the
bearing 23 "floats" within the housing 14, thus enabling the
bearing 23 to be mobile and free to move in any direction necessary
to provide proper support.
[0062] The housing 14 limits the "floating" motion of the bearing
23. In other words the movement of the bearing 23 can be limited
based upon the size of the housing 14 and more specifically the
slot 35 in which the bearing 23 is disposed. The slot 35 in which
the bearing 23 is disposed dictates the range of movement of the
bearing 23, i.e. movement can be constrained such that the bearing
23 can only move from an anterior to a posterior position. More
specifically, the slot includes side walls 37, which define the
size and shape of the slot 35, and a seat 39 on which the bearing
is disposed. The movement of the bearing 23 is restricted based
upon the shape of the walls 35 of the slot 35 in which the bearing
23 sits. For example, the slot 35 can be in the shape of a circle,
an oval, or any other round-sided shape. The slot 35 must be shaped
to have rounded sides so as to prevent the bearing 23 from lodging
in a corner of the slot 35. The slot 35 can be formed such that the
seat 39 does not have a uniform depth, such that there are peaks or
angles within the slot 35, as shown in FIG. 27. The lack of
uniformity restricts movement of the bearing 23 within the slot 35
because the bearing 23 would require additional force in order to
slide in the direction of the peak or angle.
[0063] A removable insert 33, as shown in FIGS. 28 and 29, can also
be disposed within the housing 14 for holding the bearing 23 in
place. The insert 33 includes an upper surface 29 for engaging the
bearing surfaces 24, 26. The insert 33, can be made of any material
that enables the bearing 23 to functionally "float" across the
insert 33 without excessive friction. The benefit of including the
insert 33 in a housing 14 is that the insert 33 can be made of a
different material than that of the housing 14. Accordingly, the
housing 14 can be made from a first composition that is
advantageous for the functionality of the housing and provides
other strength characteristics while the insert 33 can be made from
a more lubricious material to allow for more efficient
friction-free movement of the bearing 23 thereon.
[0064] The movement of the bearing 23 is restricted based upon the
shape of the insert 33 into which the bearing 23 is placed. The
insert 33 includes side walls 41, which define the size and shape
of the insert 33, and an insert seat 29 on which the bearing is
disposed. The movement of the bearing 23 is restricted based upon
the shape of the walls 41 of the insert 33 in which the bearing 23
sits. For example, the insert 33 can be in the shape of a circle,
an oval, or any other round-sided shape. The insert 33 must be
shaped to have rounded sides so as to prevent the bearing 23 from
lodging in a corner of the insert 33. The insert 33 can be formed
such that the insert seat 29 does not have a uniform depth, such
that there are peaks or angles within the insert 33, as shown in
FIG. 27. The lack of uniformity restricts movement of the bearing
23 within the insert 33 because the bearing 23 would require
additional force in order to slide in the direction of the peak or
angle.
[0065] The housing 14 can also include load distributing dampening
and cushioning pad recesses 32, 58. Load sharing pads 32, 34
generally shown at 31 and specifically indicated as pads 32 and 34
in FIGS. 1 and 2 are disposed between the inner surfaces 16, 18 and
about at least a portion of the bearing surfaces 24, 26 for sharing
absorption of compressive loads with the bearing surfaces 24, 26
while limiting relative movement of the housing members 12, 14.
More specifically, under in vivo loading conditions, the
centralized bearing surfaces 24, 26 and the floating bearing
surfaces not only provide for three-dimensional movement relatively
between the housing members 12, 14, but also share with the load
sharing pads 32, 34 the function of distributing compressive loads
on the device 10 to provide a system for motion and effective load
distribution. The centralized low friction and compression
resistant bearing surfaces 24, 26 allow full motion in multiple
planes of the spine while the load distributing damper and
cushioning pads 32, 34 simultaneously share the load. Critical is
the function of the pads 32, 34 sharing the load with the bearing
surfaces 24, 26. Although the pads 32, 34 can be compressible, the
compression is limited by the noncompressibility of the bearing
surfaces 24, 26. Likewise, although the bearing surfaces allow for
motion in multiple planes, the pads 32, 34 are fixedly secured to
the housing members 12, 14, thereby allowing for a degree of
flexibility and therefore movement of the housing members 12, 14
relative to each other, yet limiting such movement. In total, each
element, the bearing surfaces 24, 26, and pads 32, 34, allow for
movement, yet limit such movement, whether it is the sliding
movement of the bearing surfaces 24, 26 or the cushioning movement
allowed by the pads 32, 34. Each element allows for relative
movement, yet each element limits the movement of the other element
of the system.
[0066] In view of the above, the system allows restoration of
normal motion while maintaining load cushioning capabilities of a
healthy disc. This is particularly apparent with motion of the
spine. Any rotation of the upper and lower housing members 12, 14
causes the load distributing dampening and cushioning pads 32, 34
to absorb some of the load.
[0067] As shown in the various Figures, the bearing surfaces 24, 26
can include a concave surface portion on one of the upper or lower
disc members 28, 30, and a convex surface portion on the other. The
concave surface is seated within the convex surface for sliding
movement relative thereto effectively resulting in relative
pivoting motion of the housing members 12, 14, which compresses at
least a portion of the load sharing pads 32, 34 while extending at
least a portion of the oppositely disposed load bearing pad 32, 34.
Alternatively, either one of the top and bottom disc members 28, 30
can have either of the convex or concave surfaces.
[0068] The disc members 28, 30 can be made from a composition that
is noncompressible. Such compositions can be selected from the
group including ceramics, plastics, and metal bearing materials,
such as cobalt and chrome. Alternatively, the housing members 12,
14 can include projections wherein the disc members 28, 30 are
effectively integral with the housing members 12, 14. In this
situation, the entire housing, including the projections having the
bearing surfaces 24, 26 thereon, can be made from the
noncompressible material, preferably a ceramic. As stated above,
alternative configurations can be made by those skilled in the art
once understanding the present invention.
[0069] The load sharing pads 32, 34 can be in various
configurations shown in the Figures, such as paired pads 32, 34
shown in FIGS. 1-3. Alternatively, the device 10 can include four
oppositely disposed pads 38, 40, 42, 44 as shown in FIG. 10. A
further embodiment of the invention is shown in FIG. 11, wherein a
single pad 46 substantially covers the surface 18'"" of the housing
member 14'"". The pads can contour to the shape of the housing
members such as shown in FIGS. 12, 13, wherein the pad member 48 is
an annular pad member disposed with a annular housing 12'"", 14'"".
The selection of such housing members 12, 14 and pad members 31 can
be determined based on the location of the placement of the device
10 as well as the spacing conditions between the vertebrae and load
bearing necessities depending on the level of the spine being
addressed. In other words, different shaped devices, such as the
round shaped housing members shown in FIG. 12 can be used for
placement between smaller discs, such as cervical spines whereas
more rectangular shapes, such as the housing members shown in FIGS.
1-11 can be used in between lumbar vertebrae.
[0070] The load sharing pads 31, in which ever shape they are
configured, are elastic for allowing relative twisting movement
between the housing members 12, 14 effecting relative
three-dimensional movement between the housing members 12, 14,
while limiting the movement and preventing contact between the
housing members 12, 14 except for the contact between the bearing
surfaces 24, 26. By elastic, it is meant that the pad members 31
are compressible and stretchable, yet provide a self-centering
effect on the assembly with specific regard to the housing members
12, 14, as well as the bearing surfaces 24, 26. Deflection or
rotation of the forces created due to relative movement of the
bearing surfaces 24, 26, and likewise the housing members 12, 14,
forces the pads 31 to act in such a way to counter the force, thus
allowing a unique self-centering capability to the assembly 10.
While in an ideal situation, wherein the patient's facets are
uncompromised and ligamental balances are intact, this
self-centering aspect may not be completely necessary. In other
words, the patient's anatomy may still provide stabilization and
specifically, ligaments may provide self-centering. However,
ligamental imbalance, and damaged facets would normally make an
artificial disc questionable, at best, with use of the current
technology that is available. In such cases, having the ability to
self-center and restrict motion (the pads 31 of the present
invention are elastic and thus restrict motion by stretching and
returning to rest), the possibility of extending indications to
patients currently considered outside of the scope of artificial
disc technology will be highly advantageous.
[0071] The pads 31 of the present invention provide further
advantages to the invention. A key advantage is the ability to
adjust the pads 31 to patient and surgeon requirements. In such
cases wherein range of motion needs to be restricted due to
compromised facets, a harder, less elastic pad can be inserted
between the housing members 12, 14. Since this less elastic pad
would move and stretch less, the disc would be automatically
restricted in motion. This method of adjusting pads can be done
intraoperatively to compensate for surgical and patient conditions.
To one skilled in the art, one can fine-tune the assembly 10 to a
patient and surgeon's needs with multiple pads of different
properties or materials.
[0072] The pads 31 are made from a polymer or elastomer that allows
deflection under load. Examples of such polymers and elastomers are
silicone, polyurethane, and urethane composites. As discussed above
with regard to flexibility or elasticity, the content and
composition of the pads 31 are adjustable. A highly dense material
creates a very rigid disc, while a very soft material creates a
very free moving disc. The motion would be restricted in all planes
of the pad depending upon these factors. Rotation is also
restricted, as well as flexion or movement of the disc. The amount
of compression possible is restricted or allowed according to the
pads material properties. This is true of motion towards the back
or side-to-side motion. Thus, the pads 31 are always in contact and
always share the load, under any adjustment of relative positioning
of the housing members 12, 14. Since motion forces the pads to be
in contact, the pads 31 automatically damper loads imposed by the
artificial disc construct 10.
[0073] With specific regard to the flexibility or elasticity of the
polymer or elastomer composition of the pads 31, the pads can be
selected from a composition having a durometer from 20 to 98 on the
Shore OO Scale. Alternatively, the pads 31 can be selected from a
composition having a durometer from 10 to 100 on the Shore A Scale.
A further alternative is for the pads 31 to be selected from a
composition having a durometer from 22 to 75 on the Shore D Scale.
In any event, the pad members 31 can be selected during the
operation and procedure by the clinician to suit a specific
situation. Although the pad members 31 can be pre-inserted between
the housing members 12, 14 prior to insertion of the device 10 in
situ, the various configurations of the present invention can allow
for in situ replacement of the pad members 31 so as to custom
select the flexibility or elasticity of the members. In this
manner, the pad members 31 are custom designed for the individual
environment of the intervertebral space into which the device is
being disposed.
[0074] The disc members 28 and 30, and pads 31 can be contained or
locked in position in between the housing members 12, 14 by various
means. The disc 28, 30 can be locked to the housing members 12, 14
by a press fit taper, retaining ring, or other means. The key
aspect of such locking mechanisms is to prevent the disc members
28, 30 from moving against the upper or lower housing members 12,
14 once installed in order to prevent additional wear.
[0075] FIGS. 1 and 2 show disc members 28, 30 disposed in recesses
(only the lower recess 50 is shown in FIG. 2 in an exploded view)
in each of the inner surfaces 16, 18 of the housing members 12, 14.
FIGS. 6 and 7 show plan views of a second embodiment of the housing
member 12', 14', wherein each recess 50', 52 includes a ramped
surface 54, 56 leading from an outer edge to the inwardly tapered
recess portion 50', 52. The ramping 54, 56 allows access of the
disc members 28,30 in between the housing members 12', 14' after
placement of the housing members 12', 14' in the intervertebral
space. This intraoperative access of the disc members 28, 30 allows
the surgeon to test different size disc members under load
conditions to perfectly fit the disc members in place. Such an
advantage is not obtainable with any prior art device.
[0076] An alternative mechanical mechanism for locking the disc
members within the housing members are shown in FIG. 16. The
representative housing member 12"' includes recess 52'. The recess
52' includes a substantially arcuate peripheral undergroove 70. The
groove is defined by a lip portion 72 including at least one and
preferably at least two openings 74, 76. The disc member 28'"
includes bayonet style flanges 78, 80 extended radially outwardly
therefrom, the flanges 78, 80 being shaped so as to be received
through recess 74, 76. In operation the disc member 28'" can be
disposed within the recess 52' such that the flanges 78, 80 align
with recesses 74, 76. Once the disc member 28'" can be rotated
thereby providing a bayonet style locking mechanism of the disc
member 28'" within the housing 12'" as shown in FIG. 17.
[0077] A further alternative embodiment of the locking mechanism is
shown in FIGS. 18 and 19. The housing member 12'" includes a
substantially arcuate recess 52" having an open end portion 82
extending to an edge 84 of the housing member 12'". The recess 52"
includes a lip portion 86 extending about a substantial portion
thereof defining an inner groove 88 between the seating surface 90
of the recess 52" and the lip portion 86. Arm portions 92, 94 are
extensions of the lip portion 86 but extend from and are separate
from peripheral ends 96, 98 of the housing member 12'". The arm
portions 92, 94 have a spring-like quality such that they can be
deflected outwardly from the arcuate circle defined by the recess
52". Each of the arms 92, 94 has an elbow portion 100, 102
extending from each arm portion 92, 94 towards the seating surface
90, respectively. The disc member 28'" includes a substantially
arcuate peripheral, radially outwardly extending flange portion
104. The flange portion 104 includes two abutment edges 106, 108.
In operation, the flange 104 and disc member 28'" are disposed
within the annular recess or groove 88, deflecting outwardly the
arms 92, 94. Once disposed in the recess 52", as shown in FIG. 19,
the elbows 100, 102 engage the abutment surfaces 106, 108 of the
disc member 28'" thereby locking the disc member 28'" in place.
Outward deflection of the arms 92, 94 can selectively release the
disc member 28'" from locked engagement to provide for further
adjustment of the selection of the disc member during an operation
procedure.
[0078] Also, as best shown in FIGS. 6 and 7, the pads members 31
can be disposed in recesses 58, 60 in the lower and upper housing
members 12', 14' respectively. It is preferable to permanently
adhere the pad members 31 to the housing members 12', 14' by use of
mechanical mechanisms and/or various adhesives, such as
cyanoarylates, urethanes, and other medical grade adhesives. This
list of adhesives, as with other listings of ingredients in the
present application, is merely exemplary and not meant to be
exhaustive.
[0079] Examples of mechanical mechanisms for locking the pad
members 31 into recesses in the housing members are shown in FIGS.
20-23. One such mechanism is an undercut locking mechanism shown in
FIGS. 20-22. Housing member 12"" includes a central recess 52 such
as shown in FIG. 6 having a ramp portion 56. The ramp portion 56
includes a centrally located tongue groove 57 allowing for the
insertion of a spatula type device under a disc member disposed
within the recess 52 for releasing the disc member from the recess,
similar to the use of a shoehorn type mechanism. Recesses 60'
include undercut recesses 110, 112 for locking engagement with a
peripheral flange portion 114 extending from an edge 116 of a pad
member 31'. Since the pad member is made from a deflectable
material, the flange portion 114 can be force-fit into and seated
within the undercut 110, 112. The undercut locking mechanism
effectively prevents the pad member 31' from disengagement with the
housing member 12"" in situ. Of course, the upper flange 118 would
be locked within a similar undercut locking detail of recesses
within the opposing housing member (not shown).
[0080] An alternative locking mechanism between the pad member and
housing member can be a tongue-and-groove relationship as shown in
FIG. 23. Either the pad or the housing can include the tongue
portion 122 and the other pad and housing members can include the
groove 124. In other words, either of the locking members can
include the tongue 122 and the other of the members being locked
would include the groove 124. An alternative of this or the other
locking mechanism shown is that the recess and/or pad can include
multiple grooves or slots as well as multiple tongues.
[0081] The various recesses or pockets 50', 52, 58, 60 can be of
different relative sizes and shapes. For example, the upper housing
member 12' may have a larger recess or pocket for seating a
relatively larger one of said discs 28 and the lower housing member
14' may be include a smaller (larger and smaller referring to
diameter of the annular recess) of the recesses or pockets for
seating a relatively smaller one of the lower disc 30, thereby
providing for an increased range of motion at the bearing surface
interface.
[0082] The various Figures show that the outer surfaces 20, 22 of
the various embodiments of the housing members 12, 14 can include
flanges generally indicated at 60. The flanges 60 or fins, as they
are sometimes referred to in the art, provide a mechanism for
fixation to the intervertebral surfaces. Various embodiments, such
as those shown in FIGS. 1 and 2 are dual fin constructs. Other
embodiments, such as those shown in FIGS. 8, 12, and 13 are single
fin or single flange constructs. Depending upon the nature of the
surfaces to which the outer surfaces 20, 22 are to abut, the
surgeon can select various flange or fin configurations.
Additionally, the fins 60 can be located in alternative positions,
either centrally as shown in many of the Figures, or peripherally,
as shown in FIG. 14, for a specific use with anterior extension
plates, as with screw fixations. The flanges, such as flange 60'"""
can include a bore 62 therethrough, which can be either a smooth
surface or threaded depending on its intended use.
[0083] The outer surfaces 20, 22 can be smooth, which allows for
easier revision as it allows for minimal to no ingrowth or they can
be textured. Texturing of the outer surfaces 20, 22 allows ingrowth
for long-term fixation of the assembly 10. Porous coatings, plasma
spray, grit blasting, machining, chemical etching, or milling are
examples of techniques for creating ingrowth capable surfaces.
Coatings that enhance bone growth can also be applied. Examples of
such coatings are hyroxyapatite and bone morphogenic proteins.
[0084] FIGS. 20 and 21 provide structure for further rotational
stability of the device in situ. The housing member 12"" includes
pointed portions 126, 128 extending from the outer surface 20'
thereof. The point members 126, 128 function in conjunction with
the flange portion 61' to engage an opposing vertebral surface. The
point portions 126, 128 being disposed radially peripherally from
the centrally disposed flange 61' provide at least a three-point
engagement of the vertebral surface thereby preventing rotation of
the housing member 12"" relative thereto. Of course, the point
portions 126, 128 can be in made in various configurations and
extend various amounts from the outer surface 20' to be custom
suited to a specific vertebrae surface shape.
[0085] Alternatively, as shown in FIGS. 30-40, the disc 10"""" can
be formed as two separate pieces that are inserted into an
intervertebral space, generally shown as 146 in FIG. 30. The
benefit of this formation of the disc 10"""" is that the discs
10"""" can be inserted during a posterior insertion. The two discs
10"""" function so that the units work in tandem and effectively
become one artificial disc assembly. The arrangement of the two
discs 10"""" enables each disc 10"""" to be inserted on either side
of the spinal column into the intervertebral space 146 and work in
conjunction as a single artificial disc assembly 10"""". The two
discs 10"""" are angled toward the mid-line of the vertebral body
146. While two disc assemblies 10""" are described herein, more
than two discs 10"""" can also be utilized without departing from
the spirit of the present invention.
[0086] Each of the discs 10"""" include an upper housing member
12"""" and a lower housing member 14"""". The housing members
12"""", 14"""" each include a slot 35' within the housing member
12"""", 14"""". The slot 35' enables the bearing 23 to move freely
or "float" within the slot 35' in response to movement of the
housing 14. As shown in FIGS. 31, 33-34, and 38-39, the slot 35'
can be formed in any shape that enables proper movement of the
bearing 23, however, preferably the slot 35' is an open-ended
u-shaped slot with a seat 39' and side walls 37'. The side walls
37' maintain the bearing 23 in proper alignment within the housing
12"""", 14"""". As disclosed above, the bearing 23 is capable of
floating within the slot 35', thus enabling the bearing 23 to be
mobile and free to move in any direction necessary to provide
proper support for the housing 12"""", 14"""". The housing 12"""",
14"""" limits the motion of the bearing 23. The size of the housing
12"""", 14"""" and, more specifically, the slot 35' in which the
bearing 23 is disposed limits the motion of the bearing 23.
Further, bumpers 130, 132 can also be included in the slot 35' to
further limit the motion of the bearing 23, provide dampening of
the motion of the bearing 23 and prevent the bearing from being
displaced from the housing 12"""", 14"""". The bumpers 130, 132 can
be of any size sufficient to provide the necessary limitations on
the bearing 23. For example, a single bumper can be used for both
housings 12"""", 14"""". Alternatively, each housing 12"""", 14""""
can incorporate separate bumpers 130, 132. The bumpers 130, 132 are
also useful for load sharing and thereby preventing the housing
members 12"""", 14"""" from contacting one another. The bumpers of
the present invention 130, 132 are shaped to conform to the shape
of the slot 35'. In other words, the bumpers 130, 132 are shaped to
precisely fit the slot 35' in which the bumpers 103, 132 are
displaced. Preferably, the bumpers 130, 132 do not extend beyond
the length of the housing 12"""", 14"""". The bumpers 130, 132 have
walls 134, 136 respectively that engage the wall 37' of the slot
35'. This enables the bumpers 130, 132 to be maintained in
alignment and prevents the bumpers 130, 132 from moving.
[0087] The upper housing 12"""" can either include a slot 35'
identical to that of the lower housing 14"""" or can include a
single piece having a matching bearing that complements that of the
bearing 23. In other words, the upper housing 12"""" can either
have a slot 35' that is identical to the shape of the slot 35' of
the lower housing 14"""", such that the bearing 23 moves both in
both housings 12"""", 14"""" equally or the upper housing 12""""
can be formed such that only a single piece is utilized and there
is no movement within the top plate of the bearing 23.
[0088] The bearing 23' includes side arms 138, 140 that slidably
engaged the wall 37' of the slot 35'. The bearing 23' is therefore
held in position within the slot 35' via the side arms 138, 140 and
the bumpers 130, 132.
[0089] The bearing 23 of the present invention can also have
incorporated on the bearing surface 24 various shapes as shown in
the figures. Specifically, FIG. 32 shows the bearing surface
24'wherein the surface 24' is a spherical surface. The spherical
surface 24' enables the center of rotation of the bearing 23' to
exist at the center of the sphere. Therefore, the pair of discs
10"""" functions as a single artificial disc with one center of
rotation. Alternatively, the bearing 23 can have a surface that is
either convex 24" or concave 24'". This embodiment is specifically
shown in FIGS. 9 and 10 wherein the center portion of the bearing
23' is either convex or concave and there is a flat portion 29 of
the bearing 23'. When a convex or concave surface 24", 24'"
respectively, is utilized, the rotation center is not in the center
for side-to-side rotation. Thus, the assembly is somewhat resistant
to side-to-side bending but is more easily aligned.
[0090] The housings 12"""", 14"""" can be inserted simultaneously
without incorporating the floating bearing 23 initially. This
enables the disc 10"""" to be inserted into the intervertebral
space and once the disc 10"""" has been inserted, the bumpers 130,
132 and the bearing 23 can be slid into place within the slot
35'.
[0091] Various methods can be utilized for insertion of the present
invention in situ. For example, an assembled device 10 as shown in
FIG. 1, can be disposed between the intervertebral spaces during
surgery, after calculation of space, depth, and height.
Alternatively, opposing housing members 12, 14 can be disposed
between the intervertebral spaces and pads 31 and disc members 24,
26 can be tested in situ prior to fixation thereof to allow for
custom sizing. Accordingly, the present invention broadly provides
a method of assembling an artificial intervertebral disc 10 in vivo
by inserting upper and lower housing members 12, 14 into an
intervertebral space and disposing cushioning pads 31 between the
inner surfaces 16, 18 of the housing members 12, 14, thereby
placing the pads in compression. The pair of disc members 28, 30
are inserted between the inner surfaces of the plates 16, 18. The
disc members 28, 30 have abutting low friction surfaces 24, 26
therebetween. The disc members 28, 30 are surrounded by the pads
31, whereby the disc members 28, 30 and pads 31 are under
compressive forces and share such compressive forces. This step of
the bearing surfaces 24, 26 and shock absorbing pads 31 sharing
absorption of the compressive forces and limiting the relative
movement of the housing members 12, 14 is an advantage not found in
the prior art.
[0092] One use of the bearing of the present invention is in an
artificial intervertebral disc for replacement of a damaged disc in
the spine. The artificial disc 10 of the present application
includes a mobile bearing 23 that allows for the bearing 23 to move
to adjust and compensate for vertebral disc motion. By permitting
the bearing to self-adjust, the bearing 23 can more freely move
under translation loading conditions while maximizing the contact
area of the upper and lower bearing surfaces 20, 24.
[0093] In applications such as the lumbar spine, the disc upper
member and lower member are angled relative to each other to
maintain spinal curvature. The load distributing damper and
cushioning pads are always under some load when the spine is
moving, although they can be adjusted for a neutral no load
situation when the spine is not moving.
[0094] The load distributing damper and cushioning pads also create
an elastic means of self-centering the disc construct. Deflection
of rotation of the disc forces the pads to act in such a way as to
counter the force, thus allowing a unique self-centering
capability. In an ideal situation where the patient's facets are
uncompromised and ligamental balance is intact, this is not
necessary. However, ligamental balance and damaged facets would
normally make an artificial disc questionable at best with the
current art. In such cases, having the ability to self-center and
restrict motion (the pads are elastic and thus restrict motion by
stretching and returning to rest), the possibilities of extending
indications to patients currently considered outside the scope of
artificial disc technology is highly advantageous. In a floating
bearing design, the ability to self-center mixed with the dampening
abilities of the pads creates an ideal system for an artificial
disc.
[0095] The pads can also be adjusted according to patient and
surgeon requirements. In such cases where range of motion needs to
be restricted due to compromised facets, a harder, less elastic pad
can be inserted. Since a less elastic pad moves and stretches less,
the disc is automatically restricted in motion. This method of
adjusting pads can be done interoperatively to compensate for
surgical and patient conditions.
[0096] Throughout this application, various publications, including
United States patents, are referenced by author and year and
patents by number. Full citations for the publications are listed
below. The disclosures of these publications and patents in their
entireties are hereby incorporated by reference into this
application in order to more fully describe the state of the art to
which this invention pertains.
[0097] The invention has been described in an illustrative manner,
and it is to be understood that the terminology that has been used
is intended to be in the nature of words of description rather than
of limitation.
[0098] Obviously, many modifications and variations of the present
invention are possible in light of the above teachings. It is,
therefore, to be understood that within the scope of the appended
claims, the invention can be practiced otherwise than as
specifically described.
* * * * *