U.S. patent application number 10/752724 was filed with the patent office on 2004-08-12 for instrument and method for milling a path into bone.
This patent application is currently assigned to SDGI Holdings, Inc.. Invention is credited to Eisermann, Lukas.
Application Number | 20040158254 10/752724 |
Document ID | / |
Family ID | 32869579 |
Filed Date | 2004-08-12 |
United States Patent
Application |
20040158254 |
Kind Code |
A1 |
Eisermann, Lukas |
August 12, 2004 |
Instrument and method for milling a path into bone
Abstract
An instrument and method for cutting a path in bone are
provided. The instrument includes a curved guide member defining a
curved opening extending therein, and a bit member positioned
within the opening of the guide member. The bit member is adapted
to move within the opening of the guide member to cut a path in
bone.
Inventors: |
Eisermann, Lukas; (Memphis,
TN) |
Correspondence
Address: |
HAYNES AND BOONE, LLP
901 MAIN STREET, SUITE 3100
DALLAS
TX
75202
US
|
Assignee: |
SDGI Holdings, Inc.
Wilmington
DE
|
Family ID: |
32869579 |
Appl. No.: |
10/752724 |
Filed: |
January 7, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60446963 |
Feb 12, 2003 |
|
|
|
Current U.S.
Class: |
606/79 |
Current CPC
Class: |
A61F 2002/30156
20130101; A61F 2002/30401 20130101; A61F 2/4684 20130101; A61F
2002/30166 20130101; A61F 2002/30925 20130101; A61F 2002/4627
20130101; A61B 17/1637 20130101; A61F 2002/30884 20130101; A61F
2002/2835 20130101; A61F 2/4425 20130101; A61B 17/1624 20130101;
A61F 2002/30387 20130101; A61F 2/30767 20130101; A61F 2230/0013
20130101; A61F 2/4611 20130101; A61F 2002/30507 20130101; A61F
2002/30649 20130101; A61F 2002/30769 20130101; A61F 2002/30845
20130101; A61F 2250/0098 20130101; A61F 2/08 20130101; A61F
2002/30593 20130101; A61F 2002/30172 20130101; A61F 2230/0028
20130101; A61F 2230/0015 20130101; A61F 2230/0052 20130101; A61B
17/1615 20130101; A61B 17/1642 20130101; A61F 2002/30131 20130101;
A61F 2220/0033 20130101; A61B 17/1757 20130101; A61F 2310/00796
20130101; A61F 2220/0025 20130101; A61F 2002/30836 20130101; A61F
2002/3008 20130101; A61F 2230/0023 20130101; A61F 2310/00023
20130101; A61F 2/447 20130101; A61F 2002/30785 20130101; A61B
17/1671 20130101; A61F 2002/30133 20130101; A61F 2002/30373
20130101; A61F 2002/30686 20130101; A61F 2310/00017 20130101; A61B
2017/1602 20130101 |
Class at
Publication: |
606/079 |
International
Class: |
A61B 017/16 |
Claims
What is claimed is:
1. A system for simultaneously removing portions of proximate
endplates of adjacent vertebral bodies, the system comprising: a
guide member defining an extended opening extending therein, the
guide member being configured to fit in a disc space between the
two vertebral bodies; a bit member positioned within the opening of
the guide member, the bit member including a superior cutting
portion for cutting the end plate of a superior vertebral body, and
an inferior cutting portion for cutting the end plate of an
inferior vertebral body; a rotatable element operatively connected
to the bit member to impart rotational movement to the superior and
inferior cutting portions, and operatively connected to the guide
member for moving the bit member along at least a portion of the
extended opening.
2. An instrument for cutting a path in bone, comprising a
non-linear guide member defining a non-linear opening extending
therein, and a bit member positioned within the opening of the
guide member, the bit member being adapted to move within the
opening of the guide member to cut a path in bone.
3. The instrument of claim 2 wherein the bit member comprises at
least one bearing assembly disposed adjacent to the guide member to
accommodate positioning of the bit member within the opening of the
guide member.
4. The instrument of claim 2 further comprising at least one
rotatable element to accommodate rotational movement of the bit
member within the opening of the guide member.
5. The instrument of claim 4 wherein the rotatable element is a
gear assembly.
6. The instrument of claim 2 wherein the bit member extends from a
first vertebra to an adjacent second vertebra.
7. The instrument of claim 4 further comprising a power source
operatively connected to the rotatable element of the bit member
for imparting rotational movement to the bit member.
8. The instrument of claim 7 further comprising a conduit extending
from the guide member for housing a shaft associated with the power
source and the rotatable element.
9. The instrument of claim 8 wherein the conduit is operatively
connected to the bit member and is adapted to impart translational
movement to the bit member.
10. The instrument of claim 2 wherein the non-linear guide member
provides a relatively smooth curvature and a degree of curvature of
the curved guide member corresponds to a predetermined cutting
path.
11. The instrument of claim 10 wherein the predetermined cutting
path accommodates a transforaminal approach for cutting vertebral
bone.
12. The instrument of claim 2 wherein non-linear guide member
provides a relatively smooth curvature and a degree of curvature of
the guide member is variable.
13. The instrument of claim 8 further comprising a handle connected
to the guide member.
14. The instrument of claim 13 wherein the handle is disposed
concentrically about the conduit.
15. An instrument for cutting a path in bone, comprising a curved
guide member defining a curved opening extending therein, a bit
member positioned within the opening of the guide member, a
rotatable element operatively connected to the bit member to impart
rotational movement to the bit member, a handle operatively
connected to the bit member to impart translational movement to the
bit member, wherein the bit member is adapted to cut a curved path
into bone via rotational movement in and translational movement
through the guide member.
16. The instrument of claim 15 wherein the curved path cut into
bone corresponds to a transforaminal approach to the bone.
17. The instrument of claim 15 further comprising at least one
bearing assembly to accommodate positioning of the bit member
within the curved opening of the guide member.
18. The instrument of claim 15 wherein the degree of curvature of
the guide member is variable to correspond to a predetermined
cutting path.
19. A method for cutting a curved path into bone, comprising
providing an instrument having a curved guide member, the curved
guide member defining a curved opening therein, positioning a bit
member within the opening of the guide member, actuating the
instrument to impart rotational movement to the bit member,
engaging the bit member with bone, and imparting a translational
force to the bit member to cut a curved path in bone.
20. The method of claim 19 wherein the curved cutting path is
variable.
21. The method of claim 18 wherein actuating the instrument imparts
rotational movement to the bit member via a gear assembly.
22. The method of claim 18 wherein actuating the instrument imparts
rotational movement to the bit member via a pneumatic system.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/446,963 filed on Feb. 12, 2003. U.S. Provisional
Application No. 60/446,963 is herein incorporated by reference for
all legitimate purposes.
BACKGROUND
[0002] The present disclosure relates generally to the field of
orthopedics and spinal surgery, and in some embodiments, the
present disclosure relates to intervertebral prosthetic joints for
use in the total or partial replacement of a natural intervertebral
disc, and methods and tools for use therewith.
[0003] In the treatment of diseases, injuries or malformations
affecting spinal motion segments, and especially those affecting
disc tissue, it has long been known to remove some or all of a
degenerated, ruptured or otherwise failing disc. In cases involving
intervertebral disc tissue that has been removed or is otherwise
absent from a spinal motion segment, corrective measures are taken
to ensure the proper spacing of the vertebrae formerly separated by
the removed disc tissue.
[0004] In some instances, the two adjacent vertebrae are fused
together using transplanted bone tissue, an artificial fusion
component, or other compositions or devices. Spinal fusion
procedures, however, have raised concerns in the medical community
that the bio-mechanical rigidity of intervertebral fusion may
predispose neighboring spinal motion segments to rapid
deterioration. More specifically, unlike a natural intervertebral
disc, spinal fusion prevents the fused vertebrae from pivoting and
rotating with respect to one another. Such lack of mobility tends
to increase stresses on adjacent spinal motion segments.
[0005] Additionally, several conditions may develop within adjacent
spinal motion segments, including disc degeneration, disc
herniation, instability, spinal stenosis, spondylosis and facet
joint arthritis. Consequently, many patients may require additional
disc removal and/or another type of surgical procedure as a result
of spinal fusion. Alternatives to spinal fusion are therefore
desirable.
[0006] In particular, this disclosure relates to an instrument that
aids in the insertion of alternatives to spinal fusion.
SUMMARY
[0007] An instrument for cutting a path in bone is provided. The
instrument includes a curved guide member defining a curved opening
extending therein, and a bit member positioned within the opening
of the guide member. The bit member is adapted to move within the
opening of the guide member to cut a path in bone.
[0008] In another embodiment, an instrument for cutting a path in
bone is provided. The instrument includes a curved guide member
defining a curved opening extending therein, a bit member
positioned within the opening of the guide member, a rotatable
element operatively connected to the bit member to impart
rotational movement to the bit member, and a handle operatively
connected to the bit member to impart translational movement to the
bit member. The bit member is adapted to cut a curved path into
bone via rotational movement in and translational movement through
the guide member.
[0009] In yet another embodiment, a method for cutting a curved
path into bone is provided. The method includes providing an
instrument having a curved guide member, the curved guide member
defining a curved opening therein, positioning a bit member within
the opening of the guide member, actuating the instrument to impart
rotational movement to the bit member, engaging the bit member with
bone, and imparting a translational force to the bit member to cut
a curved path in bone.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a lateral view of a portion of a spondylosed
vertebral column.
[0011] FIG. 2 is a lateral view of a pair of adjacent vertebral
endplates of FIG. 1.
[0012] FIG. 3a is a lateral view of the pair of adjacent vertebral
endplates of FIG. 2 with a rod and screw arrangement.
[0013] FIG. 3b is a longitudinal, partial sectional view of the
pair of adjacent vertebral bodies of FIG. 3a.
[0014] FIG. 4a is an isometric view of an articulating prosthetic
joint for lateral insertion according to one embodiment of the
present disclosure.
[0015] FIG. 4b is an isometric view of an articulating prosthetic
joint for lateral insertion according to another embodiment of the
present disclosure.
[0016] FIG. 4c is a front view of the articulating prosthetic joint
for lateral insertion of FIG. 4b.
[0017] FIG. 5 is a longitudinal view of the prosthetic joint of
FIG. 4a.
[0018] FIG. 6 is a lateral view of the prosthetic joint of FIG.
4a.
[0019] FIG. 7 is a lateral, partial sectional view of the
prosthetic joint of FIG. 4a disposed between a pair of spondylosed
vertebral endplates.
[0020] FIG. 8 is a lateral, partial sectional view of an
alternative articulating prosthetic joint disposed between a pair
of vertebral endplates.
[0021] FIG. 9 is an isometric view of an alternative articulating
prosthetic joint according to another embodiment of the present
disclosure.
[0022] FIG. 10 is a lateral, partial sectional view of the
prosthetic joint of FIG. 9 disposed between a pair of spondylosed
vertebral endplates.
[0023] FIG. 1I is a lateral, partial sectional view of an
alternative articulating prosthetic joint disposed between a pair
of vertebral endplates.
[0024] FIG. 12 is an isometric view of a disc prosthesis according
to another embodiment of the present disclosure.
[0025] FIG. 13 is an isometric view of an alternative disc
prosthesis according to another embodiment of the present
disclosure.
[0026] FIG. 14 is an isometric view of an alternative articulating
prosthetic joint for anterior insertion according to another
embodiment of the present disclosure.
[0027] FIG. 15 is a longitudinal view of the prosthetic joint of
FIG. 14.
[0028] FIG. 16 is a lateral view of the prosthetic joint of FIG.
14.
[0029] FIG. 17 is a lateral view of the prosthetic joint of FIG. 14
disposed between a pair of spondylosed vertebral endplates.
[0030] FIG. 18 is a longitudinal view of an alternative
articulating prosthetic joint for anterior insertion according to
another embodiment of the present disclosure.
[0031] FIG. 19 is a longitudinal view of an alternative
articulating prosthetic joint for anterior insertion according to
yet another embodiment of the present disclosure.
[0032] FIG. 20 is a longitudinal view of an alternative
articulating prosthetic joint for anterior insertion according to
yet another embodiment of the present disclosure.
[0033] FIG. 21 is a longitudinal view of a pair of verterbral
endplates having slots for receiving the prosthetic joint of FIG.
18.
[0034] FIG. 22 is a longitudinal view of a pair of verterbral
endplates having slots for receiving the prosthetic joint of FIG.
19.
[0035] FIG. 23 is a longitudinal view of a pair of verterbral
endplates having slots for receiving the prosthetic joint of FIG.
20.
[0036] FIG. 24 is a lateral, partial sectional view of the
prosthetic joint of FIG. 14 disposed between a pair of spondylosed
vertebral endplates and an orthopedic implant.
[0037] FIG. 25 is a lateral, partial sectional view of the
prosthetic joint of FIG. 14 disposed between a pair of spondylosed
vertebral endplates and a lag screw.
[0038] FIG. 26 is a schematic top view of the arrangement depicted
in FIG. 25.
[0039] FIG. 27 is a schematic top view of a vertebral body
depicting a path for transforaminal insertion.
[0040] FIG. 28 is an isometric view of an alternative articulating
prosthetic joint for transforaminal insertion according to another
embodiment of the present disclosure.
[0041] FIG. 29 is a lateral view of the prosthetic joint of FIG.
28.
[0042] FIG. 30 is a longitudinal view of the prosthetic joint of
FIG. 28.
[0043] FIG. 31a is a lateral, partial sectional view of the
prosthetic joint of FIG. 28 disposed between a pair of vertebral
endplates.
[0044] FIG. 31b is a longitudinal, partial sectional view of the
prosthetic joint of FIG. 28 disposed between a pair of vertebral
endplates.
[0045] FIG. 32 is a schematic top view depicting a transforaminal
slot formed in a vertebral endplate.
[0046] FIG. 33 is a schematic top view depicting a milling
apparatus shown inserted above a vertebral endplate.
[0047] FIG. 34a is a lateral view of the milling apparatus of FIG.
33 shown disposed between a pair of adjacent vertebral
endplates.
[0048] FIG. 34b is a detailed view of a milling tool of the milling
apparatus of FIG. 34a.
[0049] FIG. 34c is a detailed view of an alternative milling
tool.
[0050] FIG. 35 is a schematic view of the milling apparatus of FIG.
33.
[0051] FIG. 36 is an isometric view of an alternative articulating
prosthetic joint for transforaminal insertion according to another
embodiment of the present disclosure.
[0052] FIG. 37 is a lateral view of the prosthetic joint of FIG.
36.
[0053] FIG. 38 is a longitudinal view of the prosthetic joint FIG.
36.
[0054] FIG. 39 is an isometric view of an alternative articulating
prosthetic joint for anterior-oblique insertion according to
another embodiment of the present disclosure.
[0055] FIG. 40 is a longitudinal view of the prosthetic joint of
FIG. 39.
[0056] FIG. 41 is a lateral view of the prosthetic joint of FIG.
39.
[0057] FIG. 42 is lateral, partial sectional view of the prosthetic
joint of FIG. 39 disposed between a pair of vertebral
endplates.
[0058] FIG. 43 is a longitudinal, partial sectional view of the
prosthetic joint of FIG. 39 disposed between a pair of vertebral
endplates.
[0059] FIG. 44a is a top, schematic view depicting a slot formed in
a vertebral endplate for receiving the prosthetic joint of FIG.
39.
[0060] FIG. 44b is a schematic view depicting an alignment process
associated with the insertion of the prosthetic joint of FIG.
39.
[0061] FIG. 45 is an exploded view an alternative prosthetic joint
according to yet another embodiment of the present disclosure.
[0062] FIG. 46 is an isometric view of the prosthetic joint of FIG.
45.
[0063] FIG. 47 is a longitudinal view of the prosthetic joint of
FIG. 46.
[0064] FIG. 48 is a longitudinal view of a pair of adjacent
vertebral endplates.
[0065] FIG. 49a is a plan view of an articular component of the
prosthetic joint of FIG. 45.
[0066] FIG. 49b is a sectional view of the articular component of
FIG. 49a taken along the line 49b-49b.
[0067] FIG. 50a is a plan view of a modular projection member of
the prosthetic joint of FIG. 45.
[0068] FIG. 50b is a sectional view of the modular projection
member of FIG. 50a taken along the line 50b-50b.
[0069] FIG. 51 is a plan view of the modular projection member of
FIG. 50a inserted into the articular component of FIG. 49a.
[0070] FIG. 52 is a plan view of the modular projection member of
FIG. 50a inserted into the articular component of FIG. 49a
depicting the modular projection member in a different position
relative to FIG. 51.
DESCRIPTION
[0071] For the purposes of promoting an understanding of the
principles of the invention, reference will now be made to the
embodiments, or examples, illustrated in the drawings and specific
language will be used to describe the same. It will nevertheless be
understood that no limitation of the scope of the invention is
thereby intended. Any alterations and further modifications in the
described embodiments, and any further applications of the
principles of the invention as described herein are contemplated as
would normally occur to one skilled in the art to which the
invention relates. As such, individual features of separately
described embodiments can be combined to form additional
embodiments. In addition, examples of deformities such as
spondylolisthesis are discussed; however, it is understood that the
various prosthetic devices described herein can be adapted for use
between not only spondylosed vertebrae, but substantially aligned
vertebrae as well.
[0072] I. Lateral Correction
[0073] In many cases of deformity, such as spondylolisthesis, one
or more vertebral bodies can be displaced with respect to other
vertebrae or the sacrum. In such a deformity, it is desirable to
reduce the extent of displacement, by re-positioning the displaced
bodies from their previous position. A spondylolisthesis reduction
can be a technically demanding procedure requiring great care to
prevent neurological impairment and damage to surrounding soft
tissue.
[0074] Referring now to FIG. 1, shown therein is a lateral view of
a portion of a spinal column 10, illustrating a group of adjacent
upper and lower vertebrae V1, V2, V3, V4 separated by natural
intervertebral discs D1, D2, D3. The illustration of four vertebrae
is only intended as an example. Another example would be a sacrum
and one vertebrae.
[0075] As shown in the drawing, the vertebrae V2 is dislocated from
the vertebrae V1 in a direction shown by arrow 22. Likewise,
vertebrae V3 is dislocated in a direction shown by arrow 23 and
vertebrae V4 is dislocated in a direction shown by arrow direction
24. It is desired that the position of vertebrae V2, V3, V4 be
corrected by moving them in a direction opposite to the arrows 22,
23, 24, respectively.
[0076] Referring now to FIG. 2, for the sake of further example,
two of the displaced vertebrae will be discussed, designated as the
lower vertebrae V.sub.L and the upper vertebrae V.sub.U. In one
embodiment, some or all of the natural disc that would have been
positioned between the two vertebrae V.sub.L, V.sub.U is typically
removed via a discectomy or a similar surgical procedure, the
details of which would be known to one of ordinary skill in the
art. Removal of the diseased or degenerated disc results in the
formation of an intervertebral space S between the upper and lower
vertebrae V.sub.U, V.sub.L.
[0077] In the present embodiment, it is desired to insert a
prosthetic joint into the intervertebral space S, similar to the
prosthetic joint disclosed in U.S. Ser. No. 10/042,589 filed Jan.
9, 2002, which is incorporated by reference. However, certain
changes are required of the above-referenced prosthetic joint. For
the following description, the prosthetic joints discussed and
described can be identical to those disclosed in the
above-referenced patent application, with the exceptions discussed
and suggested below.
[0078] Spondylolisthesis has not heretofore been corrected from the
lateral surgical approach. However, in some instances, correction
of spondylolisthesis may be desirable from a lateral approach due
to the presence of vessels and/or the nervous plexus. In some
embodiments, the lateral approach may be particularly pertinent
when correcting spondylolisthesis in the lumbar region of the
spine, although it will be understood that other regions of the
spine are also contemplated.
[0079] Referring to FIGS. 3a and 3b, correction of
spondylolisthesis can be addressed from a lateral approach by, for
example, providing a pair of bone screws 30, 32 for insertion into
the vertebrae V.sub.U, V.sub.L, respectively. In one embodiment,
the bone screws 30, 32 are bi-cortical. However, it is understood
that the bone screws may alternatively be uni-cortical. Moreover,
the bone screws 30, 32 may be formed of a variety of materials such
as any resorbable material, titanium, and PEEK. The PEEK embodiment
is advantageous due to the radiotranslucent properties resulting
from the use of PEEK material. It is further understood that the
bone screws 30, 32 may alternatively be of any other mechanical
structure, and as such, may take the form of pins or rivets, for
example. Moreover, the bone screws 30, 32 are not limited to having
threaded portions to engage the vertebrae V.sub.U, V.sub.L.
[0080] The bone screws 30, 32 may be linked to one another via a
rod 34, which is configured to rotate about both of the bone
screws. It is understood that a variety of connecting members may
be used other than the rod 34. For example, a non-uniform linkage
member may be used to link the bone screws 30, 32. A non-uniform
linkage member may provide a plurality of slots and/or grooves that
can be engaged in order to aid in its rotation about the bone
screws. The rod 34 may be connected prior to insertion of the bone
screws 30, 32 into the vertebrae V.sub.U, V.sub.L, or
alternatively, may be subsequently connected after placement of the
screws. By applying a rotating force to the rod 34 in the direction
of arrow 36, the upper vertebra V.sub.U is encouraged back into a
desired position relative to the lower vertebra V.sub.L. The
rotating force can be applied, for example, by a rotatable wrench
(not shown) that can be used by a surgeon. It is understood that
the upper vertebra V.sub.U may not reach entirely to a fully
corrected position in relation to the lower vertebra V.sub.L, but
the displacement can at least be reduced.
[0081] Although not depicted, in another embodiment, it is
contemplated that the spondylosed vertebrae V.sub.U, V.sub.L can be
addressed from both lateral directions. Thus, a pair of bone screws
substantially identical to the bone screws 30, 32 may be inserted
into the vertebrae V.sub.U, V.sub.L on the opposite side from and
in the opposite direction to the bone screws 30, 32. In such an
arrangement, the rod 34 can be replaced with a ratcheting system
that engages each of the bone screw pairs, and as such, the
vertebrae V.sub.U, V.sub.L can be rotated relative to one another
to encourage the vertebrae into a desired position relative to one
another.
[0082] Still further, the rod 34 may include any number and type of
engagement means to receive any number and type of rotating tools
used by a surgeon; For example, a keyed connection may provide more
stability when engaging the rod 34 with a corresponding rotating
tool. In other examples, a clamping tool may be used and
corresponding clamping notches may be formed in the rod 34 to
receive the clamping tool. Such an arrangement may aid in achieving
the force necessary for rotation.
[0083] Moreover, additional rods 34 and bone screws 30, 32 are
contemplated for use in rotating the spondylosed vertebrae V.sub.U,
V.sub.L back into a desired position relative to one another.
Additional rods 34 and bone screws 30, 32 may provide additional
stability during the procedure.
[0084] Furthermore, although depicted as a substantially lateral
insertion, the insertion of the bone screws 30, 32 into the
vertebrae V.sub.U, V.sub.L can be slightly angled relative to the
lateral direction. Such angling of the bone screws 30, 32 during
insertion may provide a preferred gripping angle from which the
surgeon can begin rotation of the vertebrae V.sub.U, V.sub.L
relative to one another.
[0085] Referring to FIGS. 4a, 5, and 6, shown therein is one
embodiment of an offset intervertebral articulating prosthetic
joint 40 for insertion into the intervertebral space S (FIG. 2) to
aid in the correction of spondylolisthesis. The articulating
prosthetic joint 40 extends generally along a longitudinal axis L
and includes a first articular component 42 and a second articular
component 44. The articular components 42, 44 cooperate to form the
prosthetic joint 40 which is sized and configured for disposition
within the intervertebral space S (FIG. 2) between adjacent
vertebral bodies V.sub.U, V.sub.L (FIG. 2).
[0086] The prosthetic joint 40 provides relative pivotal and
rotational movement between the adjacent vertebral bodies to
maintain or restore motion substantially similar to the normal
bio-mechanical motion provided by a natural intervertebral disc.
More specifically, the articular components 42, 44 are permitted to
pivot relative to one another about a number of axes, including
lateral or side-to-side pivotal movement about longitudinal axis L
and anterior-posterior pivotal movement about a transverse axis T.
It should be understood that in one embodiment of the disclosure,
the articular components 42, 44 are permitted to pivot relative to
one another about any axes that lies in a plane that intersects
longitudinal axis L and transverse axis T.
[0087] Furthermore, the articular components 42, 44 are permitted
to rotate relative to one another about a rotational axis R.
Although the prosthetic joint 40 has been illustrated and described
as providing a specific combination of articulating motion, it
should be understood that other combinations of articulating
movement are also possible, such as, for example, relative
translational or linear motion, and such movement is contemplated
as falling within the scope of the present disclosure.
[0088] Although the articular components 42, 44 of prosthetic joint
40 may be formed from a wide variety of materials, in one
embodiment of the disclosure, the articular components 42, 44 are
formed of a cobalt-chrome-molybdenum metallic alloy (ASTM F-799 or
F-75). However, in alternative embodiments of the disclosure, the
articular components 42, 44 may be formed of other materials such
as titanium or stainless steel, a polymeric material such as
polyethylene, or any other biocompatible material that would be
apparent to one of ordinary skill in the art.
[0089] The articular components 42, 44 each include a bearing
surface 46, 48, respectively, that may be positioned in direct
contact with vertebral bone and is preferably coated with a
bone-growth promoting substance, such as, for example, a
hydroxyapatite coating formed of calcium phosphate. Additionally,
the bearing surfaces 46, 48 of the articular components 42, 44,
respectively, may be roughened prior to being coated with the
bone-growth promoting substance to further enhance bone on-growth.
Such surface roughening may be accomplished by way of, for example,
acid etching, knurling, application of a bead coating, or other
methods of roughening that would occur to one of ordinary skill in
the art.
[0090] Articular component 42 includes a support plate 50 having an
articular surface 52 and the opposite bearing surface 46. Support
plate 50 is sized and shaped to substantially correspond to the
size and shape of a vertebral endplate of the adjacent vertebral
body V.sub.L (FIG. 2). The support plate 50 may include one or more
notches 54 or other types of indicia for receiving or engaging with
a corresponding portion of a surgical instrument (not shown) to aid
in the manipulation and insertion of the prosthetic joint 40 within
the intervertebral space S (FIG. 2) between the adjacent vertebral
bodies V.sub.U, V.sub.L (FIG. 2). The surgical instrument (not
shown) is preferably configured to hold the articular components
42, 44 at a predetermined orientation and spatial relationship
relative to one another during manipulation and insertion of the
prosthetic joint 40, and to release the articular components 42, 44
once properly positioned between the adjacent vertebrae.
[0091] In one embodiment of the disclosure, the articular component
42 includes a projection 56 having a convex shape, which may be
configured as a spherical-shaped ball (half of which is shown). It
should-be understood that other configurations of the projection 56
are also contemplated, such as, for example, cylindrical,
elliptical or other arcuate configurations or possibly non-arcuate
configurations. It should also be understood that the remaining
portion of articular component 42 may take on planar or non-planar
configurations, such as, for example, an angular or conical
configuration extending about the projection 56.
[0092] A flange member or keel 58 extends from the bearing surface
46 and is configured for disposition within a preformed opening in
the adjacent vertebral endplate. As with the bearing surface 46,
the keel 58 may be coated with a bone-growth promoting substance,
such as, for example, a hydroxyapatite coating formed of calcium
phosphate. Additionally, the keel 58 may be roughened prior to
being coated with the bone-growth promoting substance to further
enhance bone on-growth. In one embodiment, the keel 58 extends
along the transverse axis T and is substantially centered along the
bearing surface 46. However, it should be understood that other
positions and orientations of the keel 58 are also
contemplated.
[0093] In one embodiment, the keel 58 transversely extends along a
substantial portion of the articular component 42. Such an
embodiment would accommodate insertion of the prosthetic joint 40
using a lateral approach as opposed to, for example, an anterior
approach. In a further embodiment, the keel 58 may be angled,
tapered, or configured in some other shape to facilitate the
functional demands of the keel. In still another embodiment, the
keel 58 may be configured as a winged keel, including a lateral
portion (not shown) extending across the main body portion of keel
58.
[0094] In one embodiment, the keel 58 includes three openings 60
extending therethrough to facilitate bone through-growth to enhance
fixation to the adjacent vertebral bodies V.sub.U, V.sub.L (FIG.
2). However, it should be understood that any number of openings 60
may be defined through the keel 58, including a single opening or
two or more openings. It should also be understood that the
openings 60 need not necessarily extend entirely through the keel
58, but may alternatively extend partially therethrough. It should
further be understood that the keel 58 need not necessarily define
any openings 60 extending either partially or entirely
therethrough. Additionally, although the openings 60 are
illustrated as having a circular configuration, it should be
understood that other sizes and configurations of openings 60 are
also contemplated.
[0095] In one embodiment, the articular component 44 includes a
support plate 70 having an articular surface 72 and the opposite
bearing surface 48. Support plate 70 may be sized and shaped to
substantially correspond to the size and shape of a vertebral
endplate of the adjacent vertebral body V.sub.U. The support plate
70 may include one or more notches 74 or other types of indicia for
receiving and engaging with a corresponding portion of a surgical
instrument, such as discussed above with reference to articular
component 42.
[0096] In one embodiment, the articular surface 72 includes a
recess 76. In one embodiment, the recess 76 has a concave shape,
and is configured as a spherical-shaped socket. However, it should
be understood that other configurations of the recess 76 are also
contemplated, such as, for example, cylindrical, elliptical or
other arcuate configurations or possibly non-arcuate
configurations. The remaining portion of the articular surface 72
can be angled or otherwise configured to facilitate the insertion
and/or use of the prosthesis.
[0097] Although the concave recess 76 is illustrated as having a
generally smooth, uninterrupted articular surface, it should be
understood that a surface depression or cavity may be defined along
a portion of the recess 76 to provide a means for clearing out
matter, such as particulate debris, that is disposed between the
abutting articular components 42, 44. In such case, the convex
articular surface of the projection 56 may alternatively define a
generally smooth, uninterrupted articular surface. In another
embodiment, each of the convex projection 56 and the concave recess
76 may define a surface depression to facilitate removal of
particulate matter disposed between the abutting articular
components 42, 44.
[0098] A flange member or keel 68, configured similar to the keel
58 of articular component 42, extends from the bearing surface 48.
In one embodiment, the keel 68 extends along the transverse axis T
and is offset from the center of the bearing surface 48. Such an
embodiment would accommodate insertion of the prosthetic joint 40
using a lateral approach. However, it should be understood that
other shapes, positions and orientations of the keel 68 are also
contemplated. For example, in FIGS. 4b and 4c, the keels 58 and 68
may be angled relative to the transverse axis T to aid in the
circumvention of veins, arteries, bony portions, or other obstacles
that may be in place during insertion of the prosthetic joint 40.
Also, the keel 68 may be angled, tapered, or configured in some
other shape to facilitate the functional demands of the keel. In
still another embodiment, the keel 68 may be configured as a winged
keel, including a transverse portion extending across the main body
portion of the keel 68.
[0099] In one embodiment, and referring to FIG. 5, the keel 68 also
includes three openings 70 extending therethrough to facilitate
bone through-growth to enhance fixation to the adjacent vertebra.
However, it should be understood that any number of openings 70 may
be defined through keel 70, including a single opening or two or
more openings. It should also be understood that the openings 70
need not necessarily extend entirely through the keel 68, but may
alternatively extend partially therethrough. It should further be
understood that the keel 68 need not necessarily define any
openings 70 extending either partially or entirely therethrough.
Additionally, although the openings 70 are illustrated as having a
circular configuration, it should be understood that other sizes
and configurations of openings 70 are also contemplated. As
discussed above, the bearing surfaces 46, 48 that are in direct
contact with vertebral bone are preferably coated with a
bone-growth promoting substance. Specifically, the bearing surface
48 and the surface of the keel 68 can be coated with hydroxyapatite
to promote bony engagement with the adjacent vertebral body
V.sub.U. As also discussed above, the bearing surface 48 and the
surface of keel 68 can be roughened prior to application of the
hydroxyapatite coating.
[0100] In some embodiments, one or both of the keels 58, 68 may
include a sharp forward edge, illustrated by edge 68a of FIG. 4. By
having such an edge, insertion of the keel into the associated
vertebral body is facilitated. Also, the edge 68a can be of
sufficient sharpness that the adjacent vertebral bodies do not
require a slot for receiving the keel 68, discussed in greater
detail below.
[0101] Referring to FIG. 7, to accommodate insertion of the offset
prosthetic joint 40 within a spondylosed intervertebral space, the
partially corrected upper and lower vertebrae V.sub.U, V.sub.L can
be prepared to accept the prosthetic joint 40 (shown in section in
FIG. 7a) therebetween. Specifically, elongate openings or slots 80,
82 may be formed along the vertebral endplates of the upper and
lower vertebrae V.sub.L, V.sub.U, respectively, at a predetermined
width and to a predetermined depth. The slots 80, 82 can be
laterally offset from each other to accommodate the displaced
vertebrae V.sub.L and/or V.sub.U. In one embodiment, the elongate
slots 80, 82 are rectangular-shaped and extend laterally through
the vertebrae V.sub.L, V.sub.U, respectively. In a specific
embodiment, the slots 80, 82 are formed by chiseling or curetting.
However, other methods of forming slots 80, 82 are also
contemplated as would occur to one of ordinary skill in the art,
such as, for example, by drilling or reaming. Furthermore, for some
embodiments of the prosthetic joint 40, the keels 58 and/or 68 can
form their own corresponding slots 80, 82, respectively.
[0102] Referring to FIG. 8, in one embodiment, the upper and lower
vertebrae V.sub.U, V.sub.L may be fully corrected, and thus, an
alternative articulating prosthetic joint 90 may be used in
correcting spondylolisthesis. The articulating joint 90 may be
substantially similar to the prosthetic joint 40 with the exception
of the orientation of various elements of the articulating joint
90. For example, to accommodate insertion into fully corrected
upper and lower vertebrae V.sub.U, V.sub.L, the articulating joint
90 may include a laterally-extending keel 92 that is substantially
centered on an upper articulating component 94 of the articulating
joint and a laterally-extending keel 96 that is substantially
centered on a lower articulating component 98. Furthermore, the
upper articulating component 94 may include a recess 100 that is
substantially centered to correspond to a substantially centered
projection 102 extending from the lower articulating component 98.
In one embodiment, the upper and lower articulating components 94,
98 are substantially flush with one another when disposed between
fully corrected upper and lower vertebrae V.sub.U, V.sub.L.
[0103] To accommodate insertion of the offset prosthetic joint 90,
the fully corrected upper and lower vertebrae V.sub.U, V.sub.L can
be prepared to accept the prosthetic joint 90 therebetween.
Specifically, elongate openings or slots 104, 106 may be formed
along the vertebral endplates of the upper and lower vertebrae
V.sub.U, V.sub.L, respectively, at a predetermined width and to a
predetermined depth. The slots 104, 106 can be substantially
aligned with each other to accommodate the fully corrected upper
and lower vertebrae V.sub.U, V.sub.L. In one embodiment, the
elongate slots 104, 106 are rectangular-shaped and extend laterally
through the vertebrae V.sub.U, V.sub.L, respectively. In a specific
embodiment, the slots 104, 106 are formed by chiseling or
curetting. However, other methods of forming slots 104, 106 are
also contemplated as would occur to one of ordinary skill in the
art, such as, for example, by drilling or reaming. Furthermore, for
some embodiments of the prosthetic joint, the keels 92 and/or 96
can form their own corresponding slots 104, 106, respectively.
[0104] Referring to FIG. 9, in an alternative embodiment, a
slidable prosthetic joint 110 can be used to help with the lateral
approach for treating spondylolisthesis. The sliding joint 110
extends generally along the longitudinal axis L and includes a
first slidable component 112 and a second slidable component 114.
The slidable components 112, 114 cooperate to form the sliding
joint 110 which is sized and configured for disposition within an
intervertebral space between adjacent vertebral bodies.
[0105] The sliding joint 110 provides movement between the adjacent
vertebral bodies to maintain or restore some of the motion similar
to the normal bio-mechanical motion provided by a natural
intervertebral disc. More specifically, the slidable components
112, 114 are permitted to translate relative to one another in the
axial plane.
[0106] Although the slidable components 112, 114 of prosthetic
joint 110 may be formed from a wide variety of materials, in one
embodiment, the slidable components 112, 114 are formed of a
cobalt-chrome-molybdenum metallic alloy (ASTM F-799 or F-75).
However, in alternative embodiments, the slidable components 112,
114 may be formed of other materials such as titanium or stainless
steel, a polymeric material such as polyethylene, or any other
biocompatible material that would be apparent to one of ordinary
skill in the art. The surfaces of the slidable components 112, 114
that are positioned in direct contact with vertebral bone are
preferably coated with a bone-growth promoting substance, such as,
for example, a hydroxyapatite coating formed of calcium phosphate.
Additionally, the surface of the slidable components 112, 114 that
are positioned in direct contact with vertebral bone are preferably
roughened prior to being coated with the bone-growth promoting
substance to further enhance bone on-growth. Such surface
roughening may be accomplished by way of, for example, acid
etching, knurling, application of a bead coating, or other methods
of roughening that would occur to one of ordinary skill in the
art.
[0107] Slidable component 112 includes a support plate 116 having a
slidable surface 118 and an opposite bearing surface 120. Support
plate 116 is preferably sized and shaped to substantially
correspond to the size and shape of the vertebral endplate of an
adjacent vertebra. The support plate 116 can include one or more
notches 122 or other types of indicia for receiving and engaging
with a corresponding portion of a surgical instrument (not shown)
to aid in the manipulation and insertion of the prosthetic joint
110 within an intervertebral space between adjacent vertebrae. The
surgical instrument (not shown) is preferably configured to hold
the slidable components 112, 114 at a predetermined orientation and
spatial relationship relative to one another during manipulation
and insertion of the prosthetic joint 110, and to release the
slidable components 112, 114 once properly positioned between the
adjacent vertebrae.
[0108] A flange member or keel 124 extends from the bearing surface
120 and is configured for disposition within a preformed opening in
the adjacent vertebral endplate. In one embodiment, the keel 124
extends perpendicularly from the bearing surface 120 and is
approximately centrally located along the bearing surface 120.
However, it should be understood that other positions and
orientations of the keel 124 ate also contemplated.
[0109] In one embodiment, the keel 124 transversely extends along a
substantial portion of the support plate 114. Such an embodiment
would accommodate insertion of the prosthetic joint 110 using a
lateral approach. In a further embodiment, the keel 124 may be
angled, tapered, or configured in some other shape to facilitate
the functional demands of the keel. In still another embodiment,
the keel 124 may be configured as a winged keel, including a
transverse portion extending across the main body portion of keel
124.
[0110] The keel 124 also includes openings 126 extending
therethrough to facilitate bone through-growth to enhance fixation
to the adjacent vertebra. However, it should be understood that any
number of openings 126 may be defined through keel 124, including a
single opening or three or more openings. It should also be
understood that the openings 104 need not necessarily extend
entirely through the keel 124, but may alternatively extend
partially therethrough. It should further be understood that the
keel 124 need not necessarily define any openings 126 extending
either partially or entirely therethrough. Additionally, although
the openings 126 are illustrated as having a circular
configuration, it should be understood that other sizes and
configurations of openings 126 are also contemplated. As discussed
above, the surfaces of the slidable component 112 that are in
direct contact with vertebral bone are preferably coated with a
bone-growth promoting substance. Specifically, the bearing surface
120 and the surfaces of the keel 124 can be coated with
hydroxyapatite to promote bony engagement with the adjacent
vertebrae. As also discussed above, the bearing surface 120 and the
surfaces of keel 124 can be roughened prior to application of the
hydroxyapatite coating.
[0111] In one embodiment, the slidable component 114 includes a
support plate 128 having a slidable surface 130 and an opposite
bearing surface 132. Support plate 128 is preferably sized and
shaped to substantially correspond to the size and shape of the
vertebral endplate of an adjacent vertebra. The support plate 128
can include one or more notches 134 or other types of indicia for
receiving and engaging with a corresponding portion of a surgical
instrument, such as discussed above with reference to slidable
element 112.
[0112] A flange member or keel 136, configured similar to the keel
124 of slidable component 112, extends from the bearing surface
132. In one embodiment, the keel 136 extends perpendicularly from
the bearing surface 132 and is offset along the bearing surface 132
to accommodate spondylosed displacements of the vertebrae. Also,
the offset position of the keel 136 helps in the circumvention of
veins, arteries, bony portions, or other obstacles that may be in
place during the insertion of the joint 110. It should be further
understood that other positions, shapes, orientations, and
quantities of the keel 136 are also contemplated. It should also be
understood that the keel 136 may also be differently positioned,
shaped or oriented, or more keels 136 can be used, for similar or
additional reasons.
[0113] In one embodiment, the keel 136 transversely extends along a
substantial portion of the support plate 128. Such an embodiment
would accommodate insertion of the prosthetic joint 110 using a
lateral approach as opposed to another approach such as an anterior
approach. In a further embodiment, the keel 136 may be angled,
tapered, or configured in some other shape to facilitate the
functional demands of the keel. In still another embodiment, the
keel 136 may be configured as a winged keel, including a transverse
portion extending across the main body portion of keel 136.
[0114] The keel 136 also includes three openings 138 extending
therethrough to facilitate bone through-growth to enhance fixation
to the adjacent vertebra. However, it should be understood that any
number of openings 138 may be defined through keel 136, including a
single opening or three or more openings. It should also be
understood that the openings 138 need not necessarily extend
entirely through the keel 136, but may alternatively extend
partially therethrough. It should further be understood that the
keel 136 need not necessarily define any openings 138 extending
either partially or entirely therethrough. Additionally, although
the openings 138 are illustrated as having a circular
configuration, it should be understood that other sizes and
configurations of openings 138 are also contemplated. As discussed
above, the surfaces of the slidable component 114 that are in
direct contact with vertebral bone are preferably coated with a
bone-growth promoting substance. Specifically, the bearing surface
132 and the surfaces of the keel 136 can be coated with
hydroxyapatite to promote bony engagement with the adjacent
vertebrae. As also discussed above, the bearing surface 132 and the
surfaces of keel 136 can be roughened prior to application of the
hydroxyapatite coating.
[0115] In some embodiments, one or both of the keels 124, 136 may
include a sharp forward edge, illustrated by edges 124a, 136a. By
having such an edge, insertion of the keels 124, 136 into the
associated vertebral body is facilitated. Also, the edges 124a,
136a can be of sufficient sharpness that the vertebral body does
not require a slot for receiving the keels 124, 136, respectively,
discussed in greater detail below.
[0116] Referring to FIG. 10, to accommodate insertion of the
prosthetic joint 110 within a spondylosed intervertebral space, the
lower and upper vertebrae V.sub.L, V.sub.U can be prepared to
accept the prosthetic joint 110 therebetween. Specifically,
elongate openings or slots 142, 144, may be formed along the
vertebral endplates of the lower and upper vertebrae V.sub.L,
V.sub.U, respectively, at a predetermined width and to a
predetermined depth. The slots 142, 144 can be laterally offset
from each other to accommodate the displaced vertebrae V.sub.L
and/or V.sub.U. In one embodiment of the disclosure, the elongate
slots 142, 144 are rectangular-shaped and extend laterally through
the vertebrae V.sub.L, V.sub.U. In a specific embodiment, the slots
142, 144 are formed by chiseling or curetting. However, other
methods of forming slots 142, 144 are also contemplated as would
occur to one of ordinary skill in the art, such as, for example, by
drilling or reaming. Furthermore, for some embodiments of the
prosthetic joint, the keels 124 and/or 136 can form their own
corresponding slots.
[0117] Referring to FIG. 11, in one embodiment, the upper and lower
vertebrae V.sub.U, V.sub.L may be fully corrected, and thus, an
alternative articulating joint 150 may be used in correcting
spondylolisthesis. The articulating joint 150 may be substantially
similar to the articulating joint 110 with the exception of the
orientation of the keel. For example, to accommodate insertion into
fully corrected upper and lower vertebrae V.sub.U, V.sub.L, the
articulating joint 150 may include a keel 152 that is substantially
centered on an upper articulating component 154 of the articulating
joint and a keel 156 that is substantially centered on a lower
articulating component 158. In one embodiment, the upper and lower
articulating components 154, 158 are substantially flush with one
another when disposed between fully corrected upper and lower
vertebrae V.sub.U, V.sub.L.
[0118] To accommodate insertion of the offset prosthetic joint 150,
the fully corrected upper and lower vertebrae V.sub.U, V.sub.L can
be prepared to accept the prosthetic joint 150 therebetween.
Specifically, elongate openings or slots 160, 162 are formed along
the vertebral endplates of the upper and lower vertebrae V.sub.U,
V.sub.L, at a predetermined width and to a predetermined depth. The
slots 160, 162 can be substantially aligned with each other to
accommodate the fully corrected upper and lower vertebrae V.sub.U,
V.sub.L. In one embodiment, the elongate slots 160, 162 are
rectangular-shaped and extend laterally through the vertebrae
V.sub.U, V.sub.L, respectively. In a specific embodiment, the slots
160, 162 are formed by chiseling or curetting. However, other
methods of forming slots 160, 162 are also contemplated as would
occur to one of ordinary skill in the art, such as, for example, by
drilling or reaming. Furthermore, for some embodiments of the
prosthetic joint, the keels 152 and/or 156 can form their own
corresponding slots 160, 162, respectively.
[0119] Referring to FIGS. 12 and 13, fusion plates and cages can
also be outfitted with one or more keels and laterally inserted, in
a manner consistent with the motion-preserving embodiments
discussed above and superior to conventional fusion arrangements.
Referring specifically to FIG. 12, a lateral prosthesis 170
includes a cage 172, an upper keel 174, and a lower keel 176. The
cage 172 connects to the upper and lower keels 174, 176 through
support plates 178, 180, respectively. The cage 172 can include
many features of the LT-CAGE.TM. lumbar tapered fusion device
provided by Medtronic Sofamor Danek of Memphis, Tenn., and can be
used to contain biological material and/or other bone growth
promoting materials. Also, the lateral keels 174, 176 can help to
maintain the corrected vertebrae displacement while fusion is
occurring.
[0120] Referring to FIG. 13, a prosthesis 190 includes a plate 192,
an upper keel 194, a lower keel 196, an upper support plate 198,
and a lower support plate 200. The plate 192 can be used to
maintain a desired distance between the two support plates 198, 200
and promote fusion. Since the plate 192 can be relatively thin, the
remainder of the disc space can be filled with biological material,
bone material, and or other bone growth promoting materials.
[0121] II. Anterior Correction
[0122] In some instances, correction of spondylolisthesis may be
desirable from the anterior approach. Referring to FIGS. 14-16,
shown therein is an intervertebral articulating prosthetic joint
210 according to an alternative embodiment of the present
disclosure. The prosthetic joint 210 extends generally along a
longitudinal axis L and includes a first articular component 212
and a second articular component 214. The articular components 212,
214 cooperate to form the articulating joint 210 which is sized and
configured for disposition within an intervertebral space between a
pair of vertebral bodies, such as the intervertebral space S
between the adjacent vertebral bodies V.sub.U, V.sub.L.
[0123] The prosthetic joint 210 provides relative pivotal and
rotational movement between the adjacent vertebral bodies V.sub.U,
V.sub.L to maintain or restore motion substantially similar to the
normal bio-mechanical motion provided by a natural intervertebral
disc. More specifically, the articular components 212, 214 are
permitted to pivot relative to one another about a number of axes,
including lateral or side-to-side pivotal movement about
longitudinal axis L and anterior-posterior pivotal movement about a
transverse axis T. It should be understood that in one embodiment,
the articular components 212, 214 are permitted to pivot relative
to one another about any axes that lies in a plane that intersects
longitudinal axis L and transverse axis T. Additionally, the
articular components 212, 214 are permitted to rotate relative to
one another about a rotational axis R. Although the prosthetic
joint 210 has been illustrated and described as providing a
specific combination of articulating motion, it should be
understood that other combinations of articulating movement are
also possible, such as, for example, relative translational or
linear motion, and are contemplated as falling within the scope of
the present disclosure.
[0124] Although the articular components 212, 214 of prosthetic
joint 210 may be formed from a wide variety of materials, in one
embodiment, the articular components 212, 214 are formed of a
cobalt-chrome-molybdenum metallic alloy (ASTM F-799 or F-75).
However, in alternative embodiments, the articular components 212,
214 may be formed of other materials such as titanium or stainless
steel, a polymeric material such as polyethylene, or any other
biocompatible material that would be apparent to one of ordinary
skill in the art. The surfaces of the articular components 212, 214
that are positioned in direct contact with vertebral bone may be
coated with a bone-growth promoting substance, such as, for
example, a hydroxyapatite coating formed of calcium phosphate.
Additionally, the surface of the articular components 212, 214 that
are positioned in direct contact with vertebral bone may be
roughened prior to being coated with the bone-growth promoting
substance to further enhance bone on-growth. Such surface
roughening may be accomplished by way of, for example, acid
etching, knurling, application of a bead coating, or other methods
of roughening that would occur to one of ordinary skill in the
art.
[0125] Articular component 212 includes a support plate 216 having
an articular surface 218 and an opposite bearing surface 220.
Support plate 216 may be sized and shaped to substantially
correspond to the size and shape of the vertebral endplate of an
adjacent vertebra. The support plate 216 can include one or more
notches 222 or other types of indicia for receiving and engaging
with a corresponding portion of a surgical instrument (not shown)
to aid in the manipulation and insertion of the articulating joint
210 within an intervertebral space between adjacent vertebrae. The
surgical instrument (not shown) is preferably configured to hold
the articular components 212, 214 at a predetermined orientation
and spatial relationship relative to one another during
manipulation and insertion of the articulating joint 210, and to
release the articular components 212, 214 once properly positioned
between the adjacent vertebrae.
[0126] In one embodiment, the articular surface 218 includes a
projection 224 having a convex shape, which may be configured as a
spherical-shaped ball (half of which is shown). It should be
understood that other configurations of the projection 224 are also
contemplated, such as, for example, cylindrical, elliptical or
other arcuate configurations or possibly non-arcuate
configurations. It should also be understood that the remaining
portion of articular surface 218 may take on planar or non-planar
configurations, such as, for example, an angular or conical
configuration extending about the projection 224.
[0127] In one embodiment, the convex articular surface of the
projection 224 is interrupted by a surface depression or cavity 226
extending along the projection 224. In one embodiment, the surface
depression 226 is configured as a groove. However, it should be
understood that other types of surface depressions are also
contemplated, including no depression at all. One purpose of the
groove 226 is to facilitate the removal of matter disposed between
abutting portions of the articular components 212, 214. More
specifically, the groove 226 may aid in clearing out matter such
as, for example, particulate material, that is disposed between the
abutting articular surfaces of components 212, 214.
[0128] A flange member or keel 230 extends from the bearing surface
220 and is configured for disposition within a preformed opening in
the adjacent vertebral endplate. In one embodiment, the keel 230
extends perpendicularly from the bearing surface 220 and is
approximately centrally located along the bearing surface 220.
However, it should be understood that other positions and
orientations of the keel 230 are also contemplated.
[0129] In one embodiment, the keel 230 extends along substantially
the entire length of the support plate 216. Such an embodiment
would accommodate insertion of the articulating joint 210 using an
anterior approach. In a further embodiment, the keel 230 may be
angled, tapered, or configured in some other shape to facilitate
the functional demands of the keel. In still another embodiment,
the keel 230 may be configured as a winged keel, including a
transverse portion (not shown) extending across the main body
portion of keel 230.
[0130] The keel 230 also includes a pair of openings 232 extending
therethrough to facilitate bone through-growth to enhance fixation
to the adjacent vertebra. However, it should be understood that any
number of openings 232 may be defined through keel 230, including a
single opening or three or more openings. It should also be
understood that the openings 232 need not necessarily extend
entirely through the keel 230, but may alternatively extend
partially therethrough. It should further be understood that the
keel 230 need not necessarily define any openings 232 extending
either partially or entirely therethrough. Additionally, although
the openings 232 are illustrated as having a circular
configuration, it should be understood that other sizes and
configurations of the openings 232 are also contemplated. As
discussed above, the surfaces of the articular component 212 that
are in direct contact with vertebral bone are preferably coated
with a bone-growth promoting substance. Specifically, the bearing
surface 220 and the surfaces of the keel 230 can be coated with
hydroxyapatite to promote bony engagement with the adjacent
vertebrae. As also discussed above, the bearing surface 220 and the
surfaces of keel 230 can be roughened prior to application of the
hydroxyapatite coating.
[0131] In one embodiment, the articular component 214 includes a
support plate 240 having an articular surface 242 and an opposite
bearing surface 244. Support plate 240 may be sized and shaped to
substantially correspond to the size and shape of the vertebral
endplate of an adjacent vertebra. The support plate 240 can include
one or more notches 246 or other types of indicia for receiving and
engaging with a corresponding portion of a surgical instrument,
such as discussed above with reference to articular component
212.
[0132] In one embodiment, the articular surface 242 includes a
recess 250, which has a convex shape, such as that of a
spherical-shaped socket. However, it should be understood that
other configurations of the recess 250 are also contemplated, such
as, for example, cylindrical, elliptical or other arcuate
configurations or possibly non-arcuate configurations. The
remaining portion of the articular surface 242 can be angled or
otherwise configured to facilitate the insertion and/or use of the
articulating joint 210.
[0133] Although the concave recess 250 is illustrated as having a
generally smooth, uninterrupted articular surface, it should be
understood that a surface depression or cavity may be defined along
a portion of the recess 250 to aid in clearing out matter, such as
particulate debris, that is disposed between the abutting articular
surfaces of articular components 212, 214. In such case, the convex
articular surface of the ball 224 may alternatively define a
generally smooth, uninterrupted articular surface. In another
embodiment, each of the convex projection 224 and the concave
recess 250 may define a surface depression to facilitate removal of
particulate matter disposed between the abutting articular
surfaces.
[0134] A flange member or keel 260, configured similar to the keel
230 of articular component 212, extends from the bearing surface
244. In one embodiment, the keel 260 extends perpendicularly from
the bearing surface 244 and is approximately centrally located
along bearing surface 244. However, it should be understood that
other positions and orientations of the keel 260 are also
contemplated. It should also be understood that the articular
component 214 may include two or more keels 260 extending from the
bearing surface 244.
[0135] In one embodiment, the keel 260 extends along substantially
the entire length of the support plate 240. Such an embodiment
would accommodate insertion of the prosthetic joint 210 using an
anterior approach. In a further embodiment, the keel 260 may be
angled, tapered, or configured in some other shape to facilitate
the functional demands of the keel. In still another embodiment,
the keel 260 may be configured as a winged keel, including a
transverse portion (not shown) extending across the main body
portion of keel 260.
[0136] The keel 260 also includes a pair of openings 262 extending
therethrough to facilitate bone through-growth to enhance fixation
to the adjacent vertebra. However, it should be understood that any
number of openings 262 may be defined through keel 260, including a
single opening or three or more openings. It should also be
understood that the openings 262 need not necessarily extend
entirely through the keel 260, but may alternatively extend
partially therethrough. It should further be understood that the
keel 260 need not necessarily define any openings 262 extending
either partially or entirely therethrough. Additionally, although
the openings 262 are illustrated as having a circular
configuration, it should be understood that other sizes and
configurations of openings 262 are also contemplated. As discussed
above, the surfaces of the articular component 214 that are in
direct contact with vertebral bone are preferably coated with a
bone-growth promoting substance. Specifically, the bearing surface
244 and the surfaces of the keel 260 can be coated with
hydroxyapatite to promote bony engagement with the adjacent
vertebrae. As also discussed above, the bearing surface 244 and the
surfaces of keel 260 can be roughened prior to application of the
hydroxyapatite coating.
[0137] In some embodiments, one or both of the keels 230, 260 may
include a sharp forward edge, illustrated by edge 260a of FIG. 14.
By having such an edge, insertion of the keel into the associated
vertebral body is facilitated. Also, the edge 260a can be of
sufficient sharpness that the vertebral body does not require a
slot for receiving the keel 260, discussed in greater detail
below.
[0138] To work with dislocated vertebrae, such as vertebrae V1-V5
of FIG. 1 associated with spondylolisthesis, it is recognized that
the task of fully correcting and aligning a spondylosed segment may
not be achievable or desirable by the surgeon. Therefore, the basic
articulation described in co-pending and presently incorporated
U.S. Ser. No. 10/042,589 now has an associated displacement to
correspond to the vertebrae displacement. That is, for the amount
of displacement between two adjacent spondylosed vertebrae, the
articulation of the prosthetic joint 210 is made to correspond
thereto. In some embodiments, such displacement can be effected by
positioning one or more of the projection 224 in an offset position
on the articular surface 218 of the articular component 212, and
positioning one or more of the recess 250 in an offset position on
the articular surface 242 of the articular component 214. This
allows an uncorrected or partially corrected displacement to be
mobilized.
[0139] More particularly, and referring to FIGS. 14 and 17, the
projection 224 is offset relative to the articular surface 218. For
example, when the lower vertebra (V.sub.L of FIG. 17) is offset in
the posterior direction (illustrated by arrow P in FIG. 17), the
articular component 212 may be configured such that the projection
224 is offset in the anterior direction relative to the articular
surface 218. Continuing this example, the upper vertebra V.sub.U is
therefore offset from the lower vertebra V.sub.L in the anterior
direction (illustrated by arrow A in FIG. 17), and thus, the
articular component 214 may be configured such that the recess 250
is offset in the posterior direction relative to the articular
surface 242. In this manner, the articular components 212, 214 can
be configured to engage one another via the projection 224 and the
recess 250, yet be offset from one another to accommodate the
spondylosed relationship of the upper and lower vertebrae V.sub.U,
V.sub.L of FIG. 17.
[0140] Referring now to FIG. 16, in another embodiment, the
articulating joint 210 may be modified such that the support plate
216 includes an extended section 270 to accommodate a more
pronounced displacement relative to FIG. 17 (illustrated by arrow
272) and/or provide additional stability against subluxation. The
projection 224 may be positioned on the extended section 270 to
provide for the more pronounced displacement between articular
components 212, 214.
[0141] Referring to FIGS. 2 and 17, to accommodate insertion of the
prosthetic joint 210 within the intervertebral space S, the upper
and lower vertebrae V.sub.U, V.sub.L can be prepared to accept the
prosthetic joint 210 therebetween. Specifically, elongate openings
or slots 280, 282 are formed along the vertebral endplates of the
upper and lower vertebrae V.sub.U, V.sub.L, respectively, at a
predetermined width and to a predetermined depth. In one
embodiment, the elongate slots 280, 282 are rectangular-shaped and
extend from an anterior side 284 of the vertebrae V.sub.U, V.sub.L
toward a posterior side. In a specific embodiment, the slots 280,
282 are formed by chiseling or curetting. However, other methods of
forming the slots 280, 282 are also contemplated as would occur to
one of ordinary skill in the art, such as, for example, by drilling
or reaming. Furthermore, for some embodiments of the prosthetic
joint 210, the keels 230 and/or 260 can form their own
corresponding slots 280, 282, respectively. The preparation and
example sizes of the slots 280, 282 are described in further detail
in co-pending and presently incorporated U.S. Ser. No.
10/042,589.
[0142] Referring now to FIGS. 18-20, in other embodiments, one or
both of the articular components 212, 214 may include different
numbers of keels and/or modified keels. Referring specifically to
FIG. 18, two keels, designated 290 and 292, extend from the bearing
surface 244 and are configured for disposition within preformed
openings in the adjacent vertebral endplate. In one embodiment,
both keels 290, 292 extend perpendicularly from the bearing surface
244 and are parallel and equally spaced along a central portion of
the bearing surface 244.
[0143] Referring specifically to FIG. 19, two keels, designated 294
and 296, extend from the bearing surface 224 and are configured for
disposition within preformed openings in the adjacent vertebral
endplate. In one embodiment, both keels 294, 296 extend
perpendicularly from the bearing surface 224 and are parallel and
equally spaced along a central portion of the bearing surface 224.
It should be understood that other positions and orientations of
the keels 290, 292, 294, and 296 are also contemplated.
[0144] Referring specifically to FIG. 20, a keel 298 extends from
the bearing surface 244 similar to the keel 260 of FIG. 14, except
that the keel 298 includes a laterally-extending or "winged"
portion 300 opposing the bearing surface 244. The winged portion
300 can provide several functions, including maintaining the
bearing surface 244 tightly against the body V.sub.U, and
substantially preventing any longitudinal movement of the articular
component 214. Similarly, a keel 302 extends from the bearing
surface 224 and includes a winged portion 304 opposing the bearing
surface 224. The winged portion 304 can provide several functions,
including maintaining the bearing surface 224 tightly against the
body V.sub.L, and substantially preventing any longitudinal
movement of the articular component 212.
[0145] Referring to FIGS. 21-23, to accommodate insertion of the
above-described alternative prosthetic joints 210 within the
intervertebral space S, the upper and lower vertebrae V.sub.U,
V.sub.L can be prepared to accept each of the articulating joints
210 therebetween. Referring specifically to FIG. 21, for the
configuration of the prosthetic joint 210 of FIG. 18, multiple
slots 310 and 312 are formed along the vertebral endplate of the
upper vertebrae V.sub.U, and a single slot 314 is formed along the
vertebral endplate of the lower vertebrae V.sub.L. Referring
specifically to FIG. 22, for the configuration of the prosthetic
joint 210 of FIG. 19, multiple slots 316, 318 and 320, 322 are
formed along the vertebral endplates of the upper vertebrae
V.sub.U, and lower vertebrae V.sub.L, respectively. Referring
specifically to FIG. 23, for the configuration of the prosthetic
joint 210 of FIG. 20, winged slots 324, 326 are formed along the
vertebral endplates of the upper vertebrae V.sub.U and the lower
vertebrae V.sub.L, respectively. The preparation of the slots 310,
312, 314, 316, 318, 320, 322, 324, 326 can be accomplished in a
similar manner to those discussed above with respect to FIG. 17.
For the winged slots 324, 326, a standard chisel can be used, or
alternatively, a unique wing-shaped chisel can be used.
[0146] Referring to FIG. 24, in addition to the prosthetic joint
210, a woven orthopedic implant 330 can be used to act as an
artificial ligament between the two vertebrae V.sub.U, V.sub.L. One
embodiment of the woven implant 330 is disclosed in U.S. Ser. No.
10/082,579, which is incorporated by reference. The implant 330
functions as a natural ligament would function, and helps to
stabilize and further secure the two vertebrae V.sub.U, V.sub.L
together, and helps to discourage further displacement (or prevent
the displacement from returning to the way it was pre-surgery).
[0147] Referring to FIGS. 25 and 26, it is contemplated that a pars
fracture, such as is illustrated by a fracture in a bony element
332 that connects a posterior element, such as an articular process
334 to the vertebra V.sub.L, may also be treated during correction
of spondylolisthesis from the anterior approach. It is understood
that the fractured bony element 332 is exaggerated in the FIG. 25
for the sake of improved clarity. The pars fracture can be repaired
by driving a lag screw 336 having a threaded portion 336a and a
non-threaded portion 336b into an opening 338 in the vertebral body
V.sub.L, through the bony element 332, and into the articular
process 334. In some embodiments, all or part of the opening 338
can be pre-drilled with a drill or chisel (not shown). The lag
screw 336 is inserted and accessed through the anterior direction,
and multiple screws can be used to repair multiple processes. By
capturing the fractured posterior element and tightening the lag
screw 336, the vertebrae V.sub.L is repaired.
[0148] III. Transforaminal Prosthetic Joint
[0149] In some instances, it is often difficult to approach and
clear 4 defective intervertebral disc space due to potential damage
to important anatomical structures such as nerve roots, dura,
ligamentum flavum and interspinous ligament. For example,
preservation of the ligamentous structures is of great importance
to restore biomechanical stability of the, segment and its adjacent
counterparts. In these situations, a transforaminal approach may
allow clearance of the entire intervertebral disc space by opening
the neuroforamen on one side. After appropriate clearance, it is
possible to achieve further enlargement of the cleared
intervertebral compartment by posterior trans-pedicle distraction.
While this approach has been used for fusion techniques, such as
Transforaminal Lumbar Interbody Fusion, or TLIF, it has not
heretofore been used with motion preserving implants.
[0150] Referring to FIG. 27, in a transforaminal approach, the disc
V is approached as shown by the arrow 400. The approach is between
a posterior approach and a lateral approach, and in some cases,
only one side of the disc needs to be exposed (right or left) in
order to perform the procedure.
[0151] Referring to FIGS. 28-30, shown therein is an intervertebral
articulating prosthetic joint 410 according to another form of the
present disclosure. The articulating joint 410 extends generally
along a longitudinal axis L and includes a first articular
component 412 and a second articular component 414. The articular
components 412, 414 cooperate to form the articulating joint 410
which is sized and configured for disposition within an
intervertebral space between adjacent vertebral bodies.
[0152] The prosthetic joint 410 provides relative pivotal and
rotational movement between the adjacent vertebral bodies to
maintain or restore motion substantially similar to the normal
bio-mechanical motion provided by a natural intervertebral disc.
More specifically, the articular components 412, 414 are permitted
to pivot relative to one another about a number of axes, including
lateral or side-to-side pivotal movement about longitudinal axis L
and anterior-posterior pivotal movement about a transverse axis T.
It should be understood that in one embodiment, the articular
components 412, 414 are permitted to pivot relative to one another
about any axes that lies in a plane that intersects longitudinal
axis L and transverse axis T. Additionally, the articular
components 412, 414 are preferably permitted to rotate relative to
one another about a rotational axis R. Although the articulating
joint 410 has been illustrated and described as providing a
specific combination of articulating motion, it should be
understood that other combinations of articulating movement are
also possible and are contemplated as falling within the scope of
the present disclosure. It should also be understood that other
types of articulating movement are also contemplated, such as, for
example, relative translational or linear motion.
[0153] Although the articular components 412, 414 of prosthetic
joint 410 may be formed from a wide variety of materials, in one
embodiment, the articular components 412, 414 are formed of a
cobalt-chrome-molybdenum metallic alloy (ASTM F-799 or F-75).
However, in alternative embodiments, the articular components 412,
414 may be formed of other materials such as titanium or stainless
steel, a polymeric material such as polyethylene, or any other
biocompatible material that would be apparent to one of ordinary
skill in the art.
[0154] The surfaces of the articular components 412, 414 that are
positioned in direct contact with vertebral bone are preferably
coated with a bone-growth promoting substance, such as, for
example, a hydroxyapatite coating formed of calcium phosphate.
Additionally, the surface of the articular components 412, 414 that
are positioned in direct contact with vertebral bone are preferably
roughened prior to being coated with the bone-growth promoting
substance to further enhance bone on-growth. Such surface
roughening may be accomplished by way of, for example, acid
etching, knurling, application of a bead coating, or other methods
of roughening that would occur to one of ordinary skill in the
art.
[0155] Articular component 412 includes a support plate 416 having
an articular surface 418 and an opposite bearing surface 420.
Support plate 416 may be sized and shaped to substantially
correspond to the size and shape of the vertebral endplate of an
adjacent vertebra. In one embodiment, the support plate 416 is
shaped to facilitate a transforaminal insertion approach. As such,
the support plate 416 includes curved side portions 422a, 422b,
which are defined as the generally elongated portions of the
support plate 416 extending between articular surface 418 and the
bearing surface 420. Although not shown, the support plate 416 can
include one or more notches or other types of indicia for receiving
and engaging with a corresponding portion of a surgical instrument
(also not shown) to aid in the manipulation and insertion of the
prosthetic joint 410 within an intervertebral space between
adjacent vertebrae. The surgical instrument (not shown) is
preferably configured to hold the articular components 412, 414 at
a predetermined orientation and spatial relationship relative to
one another during manipulation and insertion of the prosthetic
joint 410, and to release the articular components 412, 414 once
properly positioned between the adjacent vertebrae.
[0156] In one embodiment, the articular surface 418 includes a
projection 424 having a convex shape, which may be configured as a
spherical-shaped ball (half of which is shown). It should be
understood that other configurations of the projection 424 are also
contemplated, such as, for example, cylindrical, elliptical or
other arcuate configurations or possibly non-arcuate
configurations. It should also be understood that the remaining
portion of articular surface 418 may take on planar or non-planar
configurations, such as, for example, an angular or conical
configuration extending about the projection 424.
[0157] A flange member or keel 426 extends from the bearing surface
410 and is configured for disposition within a preformed opening in
the adjacent vertebral endplate. In one embodiment, the keel 426
extends perpendicularly from the bearing surface 420 and is
approximately centrally located along the bearing surface 420.
However, it should be understood that other positions and
orientations of the keel 426 are also contemplated.
[0158] In one embodiment, the keel 426 transversely extends along a
substantial portion of the support plate 416. The keel 426 is
curved, generally in a direction similar to the arrow 400 of FIG.
27. The degree of curvature of the keel 426 may be substantially
similar to and congruous with the degree of curvature of the side
portions 422a, 422b. Such an embodiment would accommodate insertion
of the prosthetic joint 410 using a transforaminal approach as
opposed to the anterior or lateral approaches discussed above. In a
further embodiment, the keel 426 may be angled, tapered, or
configured in some other shape to facilitate the functional demands
of the keel. In still another embodiment, the keel 426 may be
configured as a winged keel, including a transverse portion (not
shown) extending across the main body portion of keel 426.
[0159] The keel 426 also includes three openings 428 extending
therethrough to facilitate bone through-growth to enhance fixation
to the adjacent vertebra. However, it should be understood that any
number of openings 428 may be defined through keel 426, including a
single opening or three or more openings. It should also be
understood that the openings 428 need not necessarily extend
entirely through the keel 426, but may alternatively extend
partially therethrough. It should further be understood that the
keel 426 need not necessarily define any openings 428 extending
either partially or entirely therethrough. Additionally, although
the openings 428 are illustrated as having a circular
configuration, it should be understood that other sizes and
configurations of openings 428 are also contemplated. As discussed
above, the surfaces of the articular component 412 that are in
direct contact with vertebral bone are preferably coated with a
bone-growth promoting substance. Specifically, the bearing surface
420 and the surfaces of the keel 426 can be coated with
hydroxyapatite to promote bony engagement with the adjacent
vertebrae. As also discussed above, the bearing surface 420 and the
surfaces of keel 426 can be roughened prior to application of the
hydroxyapatite coating.
[0160] In one embodiment, the articular component 414 includes a
support plate 430 having an articular surface 432 and an opposite
bearing surface 434. Support plate 430 may be sized and shaped to
substantially correspond to the size and shape of the vertebral
endplate of an adjacent vertebra. In one embodiment, the support
plate 430 is shaped to facilitate a transforaminal insertion
approach. As such, the support plate 416 includes curved side
portions 436a, 436b, which are defined as the generally elongated
portions of the support plate 430 extending between articular
surface 432 and the bearing surface 434. Although not shown, the
support plate 430 can include one or more notches or other types of
indicia for receiving and engaging with a corresponding portion of
a surgical instrument, such as discussed above with reference to
articular element 412.
[0161] In one embodiment, the articular surface 432 includes a
recess 440 having a concave shape, which may be configured as a
spherical-shaped socket. However, it should be understood that
other configurations of the recess 440 are also contemplated, such
as, for example, cylindrical, elliptical or other arcuate
configurations or possibly non-arcuate configurations. The
remaining portion of the articular surface 432 can be angled or
otherwise configured to facilitate the insertion and/or use of the
prosthesis.
[0162] Although the concave recess 440 is illustrated as having a
generally smooth, uninterrupted articular surface, it should be
understood that a surface depression or cavity may be defined along
a portion of the recess 440 to provide a means for clearing out
matter, such as particulate debris, that is disposed between the
abutting articular surfaces of components 412, 414. In such case,
the convex articular surface of the ball 424 may alternatively
define a generally smooth, uninterrupted articular surface. In
another embodiment, each of the convex projection 424 and the
concave recess 440 may define a surface depression to facilitate
removal of particulate matter disposed between the abutting
articular surfaces.
[0163] A flange member or keel 450, configured similar to the keel
426 of articular component 412, extends from the bearing surface
434. In one embodiment, the keel 450 can be centrally located, and
is positioned directly or parallel in-line with the keel 450. The
keel 450 is curved, in a direction similar to the keel 426 and the
arrow 400 of FIG. 27. The degree of curvature of the keel 450 may
be substantially similar to and congruous with the degree of
curvature of the side portions 436a, 436b. Such an embodiment would
accommodate insertion of the prosthetic joint 410 using a
transforaminal approach as opposed to the anterior or lateral
approaches discussed above. In some embodiments, the position of
the keel 450 can be offset to help circumvent veins, arteries, bony
portions, or other obstacles that may be in place during the
insertion of the joint 410.
[0164] It should also be understood that the keel 450 may also be
differently positioned, shaped or oriented, or more keels 450 can
be used, for similar or additional reasons. Also, the keel 450 may
be angled, tapered, or configured in some other shape to facilitate
the functional demands of the keel. In still another embodiment,
the keel 450 may be configured as a winged keel, including a
transverse portion (not shown) extending across the main body
portion of keel 450.
[0165] In one embodiment, the keel 450 also includes three openings
452 extending therethrough to facilitate bone through-growth to
enhance fixation to the adjacent vertebra. However, it should be
understood that any number of openings 452 may be defined through
keel 450, including a single opening or three or more openings. It
should also be understood that the openings 452 need not
necessarily extend entirely through the keel 450, but may
alternatively extend partially therethrough. It should further be
understood that the keel 450 need not necessarily define any
openings 452 extending either partially or entirely therethrough.
Additionally, although the openings 452 are illustrated as having a
circular configuration, it should be understood that other sizes
and configurations of openings 452 are also contemplated. As
discussed above, the surfaces of the articular component 414 that
are in direct contact with vertebral bone are preferably coated
with a bone-growth promoting substance. Specifically, the bearing
surface 434 and the surfaces of the keel 450 can be coated with
hydroxyapatite to promote bony engagement with the adjacent
vertebrae. As also discussed above, the bearing surface 434 and the
surfaces of keel 450 can be roughened prior to application of the
hydroxyapatite coating.
[0166] In some embodiments, one or both of the keels 426, 450 may
include a sharp forward edge, illustrated by edges 460, 462,
respectively, of FIG. 28c. By having such an edge, insertion of the
keel into the associated vertebral body is facilitated. Also, the
edges 460, 462 can be of sufficient sharpness that the vertebral
bodies do not require a slot for receiving the keels 426, 450,
discussed in greater detail below.
[0167] Referring to FIGS. 31a and 31b, to accommodate insertion of
the prosthetic joint 410 within the intervertebral space, the upper
and lower vertebrae V.sub.U, V.sub.L can be prepared to accept the
prosthetic joint 410 therebetween. Referring specifically to FIG.
31a, for the configuration of the prosthetic joint 410 of FIGS.
28-30, multiple slots 470, 472 are formed along the vertebral
endplates of the upper vertebrae V.sub.U and the lower vertebrae
V.sub.L. The slots 470, 472 can be created by the keels 426, 450
themselves, or can be prepared beforehand.
[0168] Referring also to FIG. 32, it may be desirable to prepare
one or more of the slots 470, 472 before the prosthetic joint 410
is inserted between the upper and lower vertebrae V.sub.U, V.sub.L.
The slots 470, 472 can be curved, as illustrated by the slot 472,
in accordance with the curved keels 426, 450, to facilitate the
movement of the prosthetic joint 410 during insertion.
[0169] Referring to FIGS. 33-35, as an alternative to chiseling,
which provides only for the cutting of straight slots, a milling
guide 500 may be used in conjunction with a milling tool 502 to cut
the curved slots 470, 472 (represented by 472 in FIG. 32) in the
upper and lower vertebral bone V.sub.U, V.sub.L. The milling guide
500 and milling tool 502 may be formed of any material including
biocompatible materials such as titanium. The milling guide 500
includes an elongated curved member 503, which defines a curved
opening 504 to correspond to the shape of the desired curve for the
slots 470, 472. Of course, the degree of curvature of the milling
guide 500, and therefore the curved opening 504, may vary depending
on the desired curve of the slots 470, 472. In one embodiment, the
milling guide 500 is formed of a pliable material that retains a
rigid shape upon reforming such that the degree of curvature of the
curved opening 504 may be altered without having to swap out
milling guides. The milling guide 500, and therefore the curved
opening 504, is also of sufficient length so that if the slots 470,
472 need to be continued through any posterior elements of the
vertebrae, such extension of the slots can be accomplished at the
same time.
[0170] Referring specifically to FIGS. 34a and 34b, in one
embodiment, the milling tool 502 includes a milling bit 510 that is
positioned to be rotated and translated in the curved opening 504.
In one embodiment, the milling bit 510 is a double fluted routing
bit, that may extend simultaneously into the upper and lower
vertebrae V.sub.U, V.sub.L.
[0171] The milling bit 510 is also adapted to receive a
translational force such that the milling bit can be moved back and
forth in the curved opening 504. Referring to FIG. 34b, in one
embodiment, a milling bit handle 530 is connected in any
conventional manner to a housing 522 (a portion of which is shown).
The handle 530 extends from the housing 522 and through a slot 532
formed in a proximal end 534 of the milling guide 500 relative to a
surgeon (not depicted). As such, the handle 530 can be translated
by a surgeon, thereby translating the milling bit 510 through the
curved opening 504. In this manner, the handle 530 is adapted to
impart translational movement to the milling bit 510. To
accommodate movement of the milling bit 510 within the curved
opening 504, a pair of bearing assemblies 512, 514 may be
positioned adjacent to the housing 522 to guide the milling bit 510
along the curved opening.
[0172] The housing 522 houses a rotation assembly, which, in one
embodiment, is a gear assembly 524. The gear assembly 524 includes
a drive gear 526 connected to and extending annularly around a
rotatable shaft 528. The shaft 528 is rotatable via an external
source represented by power supply 516 (FIG. 35). In one
embodiment, the shaft 528 is housed within the handle 530.
[0173] The gear assembly 524 further includes a bit gear 531, which
is connected to and extends annularly around the milling bit 510.
The bit gear 531 is positioned on the milling bit 510 such that the
bit gear is orthogonal relative to and in contact with the drive
gear 526. Thus, rotation of the shaft 528 imparts rotation to the
milling bit 510 via the gear assembly 524. A pair of annular
shoulders 535, 536 are also connected to the milling bit 510 such
that the milling bit can easily move back and forth through the
curved opening 504 without slippage in the upper or lower
directions as viewed in FIG. 34b. It is understood that the gear
assembly 524 is merely exemplary of an assembly that may be used to
impart rotational motion to the milling bit 510. Other types of
rotation-imparting assemblies are contemplated as falling within
the present disclosure such as pneumatic-type systems.
[0174] Referring to FIG. 34c, in one such embodiment, a pneumatic
system 538 may be employed to impart rotation to the milling bit
510. In one embodiment, a Medtronic Midas Rex.RTM. Legend.TM. motor
is used to supply power (represented by P) to the pneumatic system.
A conventional valve 539 is used to control the air flow and
pressure supplied to rotate the milling bit 510. In still other
embodiments, manual or combination power supplies are contemplated
as being the preferred power supply 516 (FIG. 34b) and P (FIG.
34c).
[0175] Referring again to FIGS. 34a and 34b, a guide handle 540 is
further provided such that the milling guide 500 is independently
movable relative to the milling bit 510. Thus in one embodiment,
the milling guide 500 can be held via the guide handle 540 with one
hand while the milling bit 510 may be moved within the curved
opening 504 via the handle 530 with the other hand. In some
embodiments, the handle 530 may extend through the guide handle 540
as shown in FIG. 34b. As a result, and referring to FIG. 35, the
milling bit 510 is adapted to rotate in a direction indicated by
arrow R1, and is adapted to be translated through the curved
opening 504 in the directions indicated by arrow R2.
[0176] In operation, the milling guide 500 and the milling tool 502
can be used to cut a slot, such as the slot 472, to prepare the
vertebral body V.sub.L to receive the lower portion of the
prosthetic joint 410. The surgeon first selects the desired amount
of curvature to impart to the slot 472 and selects or configures
the corresponding milling guide 500. The surgeon then approaches
the vertebral body V.sub.L from the transforaminal approach to
position the milling guide 500 into the disc space between the
upper and lower vertebrae V.sub.U, V.sub.L and to abut the milling
bit 510 against the upper and lower vertebrae V.sub.U, V.sub.L.
Upon proper positioning, the surgeon may then actuate the milling
tool 502 via the power supply 516 to begin cutting into the upper
and lower vertebrae V.sub.U, V.sub.L with the milling bit 510.
[0177] The milling guide 500 may be held by the surgeon or via an
external instrument such that the milling guide is stationary
during translational movement of the milling bit 510 through the
milling guide. The curvature of the milling guide 500 guides the
milling bit 510 transforaminally through the upper and lower
vertebrae V.sub.U, V.sub.L to cut a transforaminal slot, such as
the slot 472 depicted in the lower vertebra V.sub.L FIG. 32, to
prepare the upper and lower vertebrae to receive the transforaminal
prosthetic joint 410.
[0178] In an alternative embodiment, the keels of the prosthetic
joint 410 may take alternative shapes and configurations to assist
in the curved, transforaminal approach used in inserting the joint.
Referring to FIGS. 36-38, the keels, designated 550 and 560, extend
from the bearing surfaces 434 and 420, respectively. The keels 550,
560 are relatively short and thus extend along a short portion of
the bearing surfaces 434, 420, respectively, in comparison to the
keels 450, 426 of FIGS. 28-30. The relative shortness of the keels
550, 560 may aid such keels in following the openings 470, 472,
respectively. In addition, the shortness of the keels 550, 560 and
the ease with which such keels follow the openings 470, 472,
respectively, allows the keels to be configured as either straight
or curved keels, which increases the design options of the
prosthetic joint 410. The keels 550, 560 may also be tapered to
assist in insertion of the keels into the upper and lower vertebrae
V.sub.U, V.sub.L.
[0179] IV. Anterior-Oblique Prosthetic Joint
[0180] Another approach that can be used to avoid potential damage
to important anatomical structures such as nerve roots, dura,
ligamentum flavum and interspinous ligament is the anterior oblique
approach. For example, the straight anterior approach to the disc
space between vertebra L4 and L5, as well as the superior disc
levels, can present high surgical risks during the insertion of a
total disc replacement implant because of the attachment of the
major vessels to the anterior aspect of the spine.
[0181] Referring to FIGS. 39-41, shown therein is an intervertebral
articulating prosthetic joint 600 according to another form of the
present disclosure. The prosthetic joint 600 extends generally
along a longitudinal axis L and includes a first articular
component 602 and a second articular component 604. The articular
components 602, 604 cooperate to form the prosthetic joint 600
which is sized and configured for disposition within an
intervertebral space between adjacent vertebral bodies.
[0182] The prosthetic joint 600 provides relative pivotal and
rotational movement between the adjacent vertebral bodies to
maintain or restore motion substantially similar to the normal
bio-mechanical motion provided by a natural intervertebral disc.
More specifically, the articular components 602, 604 are permitted
to pivot relative to one another about a number of axes, including
lateral or side-to-side pivotal movement about longitudinal axis L
and anterior-posterior pivotal movement about a transverse axis T.
It should be understood that in a preferred embodiment, the
articular components 602, 604 are permitted to pivot relative to
one another about any axes that lies in a plane that intersects
longitudinal axis L and transverse axis T. Additionally, the
articular components 602, 604 may be permitted to rotate relative
to one another about a rotational axis R. Although the articulating
joint 600 has been illustrated and described as providing a
specific combination of articulating motion, it should be
understood that other combinations of articulating movement are
also possible and are contemplated as falling within the scope of
the present disclosure. It should also be understood that other
types of articulating movement are also contemplated, such as, for
example, relative translational or linear motion.
[0183] Although the articular components 602, 604 of prosthetic
joint 600 may be formed from a wide variety of materials, in one
embodiment, the articular components 602, 604 are formed of a
cobalt-chrome-molybdenum metallic alloy (ASTM F-799 or F-75).
However, in alternative embodiments of the invention, the articular
components 602, 604 may be formed of other materials such as
titanium or stainless steel, a polymeric material such as
polyethylene, or any other biocompatible material that would be
apparent to one of ordinary skill in the art. The surfaces of the
articular components 602, 604 that are positioned in direct contact
with vertebral bone are preferably coated with a bone-growth
promoting substance, such as, for example, a hydroxyapatite coating
formed of calcium phosphate. Additionally, the surface of the
articular components 602, 604 that are positioned in direct contact
with vertebral bone are preferably roughened prior to being coated
with the bone-growth promoting substance to further enhance bone
on-growth. Such surface roughening may be accomplished by way of,
for example, acid etching, knurling, application of a bead coating,
or other methods of roughening that would occur to one of ordinary
skill in the art.
[0184] Articular component 602 includes a support plate 610 having
an articular surface 612 and an opposite bearing surface 614.
Support plate 610 may be sized and shaped to substantially
correspond to the size and shape of the vertebral endplate of an
adjacent vertebra. In one embodiment, the support plate 610 is
shaped in a triangular-like configuration to facilitate an oblique
insertion approach from either the left or right side of the spine,
and as such, includes side portions P1, P2 and P3. The side
portions P1, P2 and P3 may take a variety of configurations
including curved (illustrated by P2) or straight (illustrated by P1
and P3) configurations.
[0185] The support plate 610 can include one or more notches 616 or
other types of indicia for receiving and engaging with a
corresponding portion of a surgical instrument (also not shown) to
aid in the manipulation and insertion of the prosthetic joint 600
within an intervertebral space between adjacent vertebrae. The
surgical instrument (not shown) is preferably configured to hold
the articular components 602, 604 at a predetermined orientation
and spatial relationship relative to one another during
manipulation and insertion of the prosthetic joint 600, and to
release the articular components 602, 604 once properly positioned
between the adjacent vertebrae.
[0186] In one embodiment, the articular surface 612 includes a
projection 620 having a convex shape, which may be configured as a
spherical-shaped ball (half of which is shown). It should be
understood that other configurations of the projection 620 are also
contemplated, such as, for example, cylindrical, elliptical or
other arcuate configurations or possibly non-arcuate
configurations. It should also be understood that the remaining
portion of articular surface 612 may take on planar or non-planar
configurations, such as, for example, an angular or conical
configuration extending about the projection 620.
[0187] A flange member or keel 640 extends from the bearing surface
614 and is configured for disposition within a preformed opening in
the adjacent vertebral endplate. In one embodiment, the keel 640
extends perpendicularly from the bearing surface 614 and is
approximately centrally located along the bearing surface 614.
However, it should be understood that other positions and
orientations of the keel 640 are also contemplated. Furthermore,
more keels 640 can be used, for similar or additional reasons.
[0188] In one embodiment, the keel 640 extends along a substantial
portion of the support plate 610. The keel 640 is straight, but
extends along a direction towards the notches 616 and is parallel
with one of the side portions P1 of the support plate 610. In the
present example, the keel 640 is positioned between the transverse
axis T and lateral axis L. Such an embodiment accommodates
insertion of the prosthetic joint 600 using an oblique approach as
opposed to the anterior, lateral, or transforaminal approaches
discussed above. In a further embodiment, the keel 640 may be
angled, tapered, or configured in some other shape to facilitate
the functional demands of the keel. In still another embodiment,
the keel 640 may be configured as a winged keel, including a
transverse portion (not shown) extending across the main body
portion of keel 640.
[0189] The keel 640 also includes a pair of openings 646 extending
therethrough to facilitate bone through-growth to enhance fixation
to the adjacent vertebra. Additionally, a gap 648 may also be
formed in the keel 640 to further facilitate bone through-growth.
The gap 648 also provides a reference point such that an X-ray can
be used to evaluate the positioning and alignment of the support
plate 602 during insertion of the prosthetic joint 600. It should
be understood that any number of openings 646 or gaps 648 may be
defined through keel 640, including a single opening or gap or
several openings and gaps. It should also be understood that the
openings 646 and gap 648 need not necessarily extend entirely
through the keel 640, but may alternatively extend partially
therethrough. It should further be understood that the keel 640
need not necessarily define any openings 646 or gaps 648 extending
either partially or entirely therethrough. Additionally, although
the openings 646 are illustrated as having a circular
configuration, it should be understood that other sizes and
configurations of openings 646 are also contemplated. As discussed
above, the surfaces of the articular component 602 that are in
direct contact with vertebral bone may be coated with a bone-growth
promoting substance. Specifically, the bearing surface 614 and the
surfaces of the keel 640 can be coated with hydroxyapatite to
promote bony engagement with the adjacent vertebrae. As also
discussed above, the bearing surface 614 and the surfaces of keel
640 can be roughened prior to application of the hydroxyapatite
coating.
[0190] In one embodiment, the articular component 604 includes a
support plate 650 having an articular surface 652 and an opposite
bearing surface 654. Support plate 650 may be sized and shaped to
substantially correspond to the size and shape of the vertebral
endplate of an adjacent vertebra. In one embodiment, the support
plate 610 is shaped in a triangular-like configuration to
facilitate an oblique insertion approach from either the left or
right side of the spine, and as such, includes side portions P4, P5
and P6. The side portions P4, P5 and P6 may take a variety of
configurations including curved (illustrated by P5) or straight
(illustrated by P4 and P6) configurations. The support plate 650
can include one or more notches 656 or other types of indicia for
receiving and engaging with a corresponding portion of a surgical
instrument, such as discussed above with reference to articular
component 602.
[0191] In one embodiment, the articular surface 652 includes a
recess 660 having a convex shape, which may be configured as a
spherical-shaped socket. However, it should be understood that
other configurations of the recess 660 are also contemplated, such
as, for example, cylindrical, elliptical or other arcuate
configurations or possibly non-arcuate configurations. The
remaining portion of the articular surface 652 can be angled or
otherwise configured to facilitate the insertion and/or use of the
prosthesis.
[0192] Although the concave recess 660 is illustrated as having a
generally smooth, uninterrupted articular surface, it should be
understood that a surface depression or cavity may be defined along
a portion of the recess 660 to provide a means for clearing out
matter, such as particulate debris, that is disposed between the
abutting articular surfaces of components 602, 604. In such case,
the convex articular surface of the ball 620 may alternatively
define a generally smooth, uninterrupted articular surface. In
another embodiment of the invention, each of the convex projection
620 and the concave recess 660 may define a surface depression to
facilitate removal of particulate matter disposed between the
abutting articular surfaces.
[0193] A flange member or keel 670, configured similar to the keel
640 of articular component 602, extends from the bearing surface
654. In one embodiment, the keel 670 can be centrally located, and
is positioned directly or parallel in-line with the keel 640. The
keel 640 is straight, but extends along a direction towards the
notches 656 and is parallel with one of the side portions P4 of the
support plate 650. Such an embodiment accommodates insertion of the
prosthetic joint 600 using an oblique approach as opposed to the
anterior, lateral, or transforaminal approaches discussed above. In
some embodiments, the position of the keel 670 can be offset to
help circumvent veins, arteries, bony portions, or other obstacles
that may be in place during the insertion of the joint 600.
[0194] It should be further understood that other positions,
shapes, orientations, and quantities of the keel 670 are also
contemplated. It should also be understood that more keels 670 can
be used, for similar or additional reasons. Also, the keel 670 may
be angled, tapered, or configured in some other shape to facilitate
the functional demands of the keel. In still another embodiment,
the keel 670 may be configured as a winged keel, including a
transverse portion (not shown) extending across the main body
portion of keel 670.
[0195] In one embodiment, the keel 670 also includes a pair of
openings 676 extending therethrough to facilitate bone
through-growth to enhance fixation to the adjacent vertebra.
Additionally; a gap 678 may also be formed in the keel 670 to
further facilitate bone through-growth. The gap 678 also provides a
reference point such that an X-ray can be used to evaluate the
positioning and alignment of the support plate 604 during insertion
of the prosthetic joint 600. It should be understood that any
number of openings 676 or gaps 678 may be defined through keel 670,
including a single opening or gap or several openings or gaps. It
should also be understood that the openings 676 and gap 678 need
not necessarily extend entirely through the keel 670, but may
alternatively extend partially therethrough. It should further be
understood that the keel 670 need not necessarily define any
openings 676 or gaps 678 extending either partially or entirely
therethrough; Additionally, although the openings 676 are
illustrated as having a circular configuration, it should be
understood that other sizes and configurations of openings 676 are
also contemplated. As discussed above, the surfaces of the
articular component 602 that are in direct contact with vertebral
bone are preferably coated with a bone-growth promoting substance.
Specifically, the bearing surface 654 and the surfaces of the keel
670 can be coated with hydroxyapatite to promote bony engagement
with the adjacent vertebrae. As also discussed above, the bearing
surface 654 and the surfaces of keel 670 can be roughened prior to
application of the hydroxyapatite coating.
[0196] In some embodiments, one or both of the keels 640, 670 may
include a sharp forward edge, illustrated by edges 680, 682. By
having such an edge, insertion of the keels 640, 670 into the
associated vertebral body is facilitated. Also, the edges 680, 682
can be of sufficient sharpness that the vertebral body does not
require a slot for receiving the keel 640, 670, discussed in
greater detail below.
[0197] Referring to FIGS. 42-44a, to accommodate insertion of the
prosthetic joint 600 within the intervertebral space, the upper and
lower vertebrae V.sub.U, V.sub.L can be prepared to accept the
prosthetic joint 600 therebetween. Referring specifically to FIG.
43, for the configuration of the prosthetic joint 600 of FIGS.
38-40, multiple slots 690, 692 are formed along the vertebral
endplates of the lower vertebrae V.sub.L and the upper vertebrae
V.sub.U, respectively. The slots 690, 692 can be created by the
keels 640, 670 themselves, or can be prepared beforehand by one or
more of the methods discussed above. It can be seen from FIGS.
42-44, that if one or more vessels 694 are obstructing a straight
anterior approach, the oblique approach will allow for an
anterior/lateral insertion. The implant 600 design also ensures a
sufficient contact surface for contacting the bony endplates of the
vertebrae V.sub.U, V.sub.L.
[0198] Referring to FIG. 44b, in one embodiment, the prosthetic
joint 600 can be inserted into the intervertebral space via
instrumentation such as the 4-in-1 guide as disclosed in co-pending
application U.S. Ser. No. 10/430,473, which is herein incorporated
by reference. In one example of an insertion process for inserting
the prosthetic joint 600, the midline M of the vertebrae V.sub.U,
V.sub.L is located using imaging equipment and a pin 695 is
inserted into the upper vertebra V.sub.U along the midline. An
oblique guide member 696 is then connected to the pin 695 via a
flange 697 and a handle (not shown) associated with the oblique
guide member 696 is then adjusted to a proper position. An oblique
pin 698 of the oblique guide member 696 is then impacted into the
upper vertebra V.sub.U to fix the oblique guide member, thereby
indicating the entering reference point and the direction of
implant insertion for the prosthetic joint 600. The 4-in-1 guide
(not shown) can then be used to implant the prosthetic joint 600
into the intervertebral space from an anterior-oblique approach,
the details of which are more fully discussed in co-pending
application U.S. Ser. No. 10/430,473.
[0199] V. Mobile-Bearing Prosthetic Joint
[0200] In another embodiment, the above-described prosthetic joints
can be modified to provide for translational movement as well as
rotational movement. For example, referring to FIGS. 45-47, a
mobile-bearing prosthetic joint for anterior insertion is generally
referred to by reference numeral 700. It is understood that the
mobile-bearing prosthetic joint 700 is described with respect to
anterior insertion for the sake of clarity only, and therefore, a
variety of insertion directions are contemplated for the
mobile-bearing prosthetic joint.
[0201] The prosthetic joint 700 extends generally along a
longitudinal axis L and includes a first articular component 702
and a second articular component 704. The articular components 702,
704 cooperate to form the prosthetic joint 700 which is sized and
configured for disposition within an intervertebral space between a
pair of vertebral bodies, such as an intervertebral space S1
between adjacent vertebral bodies V.sub.S, V.sub.I (FIG. 48).
[0202] The prosthetic joint 700 provides relative pivotal and
rotational movement between the adjacent vertebral bodies V.sub.S,
V.sub.I to maintain or restore motion substantially similar to the
normal bio-mechanical motion provided by a natural intervertebral
disc but with the added element of translational motion. More
specifically, the articular components 702, 704 are permitted to
pivot relative to one another about a number of axes, including
lateral or side-to-side pivotal movement about a longitudinal axis
L and anterior-posterior pivotal movement about a transverse axis
T. It should be understood that in one embodiment, the articular
components 702, 704 are permitted to pivot relative to one another
about any axes that lies in a plane that intersects longitudinal
axis L and transverse axis T. Additionally, the articular
components 702, 704 are permitted to rotate relative to one another
about a rotational axis R. In addition, the articular components
702, 704 are permitted to translate relative to one another as will
be further described.
[0203] Although the articular components 702, 704 of prosthetic
joint 700 may be formed from a wide variety of materials, in one
embodiment, the articular components 702, 704 are formed of a
cobalt-chrome-molybdenum metallic alloy (ASTM F-799 or-F-75).
However, in alternative embodiments, the articular components 702,
704 may be formed of other materials such as titanium or stainless
steel, a polymeric material such as polyethylene, or any other
biocompatible material that would be apparent to one of ordinary
skill in the art. The surfaces of the articular components 702, 704
that are positioned in direct contact with vertebral bone may be
coated with a bone-growth promoting substance, such as, for
example, a hydroxyapatite coating formed of calcium phosphate.
Additionally, the surface of the articular components 702, 704 that
are positioned in direct contact with vertebral bone may be
roughened prior to being coated with the bone-growth promoting
substance to further enhance bone on-growth. Such surface
roughening may be accomplished by way of, for example, acid
etching, knurling, application of a bead coating, or other methods
of roughening that would occur to one of ordinary skill in the
art.
[0204] Articular component 702 includes a support plate 706 having
an articular surface 708 and an opposite bearing surface 710.
Support plate 706 may be sized and shaped to substantially
correspond to the size and shape of the vertebral endplate of an
adjacent vertebra. The support plate 706 can include one or more
notches 712 or other types of indicia for receiving and engaging
with a corresponding portion of a surgical instrument (not shown)
to aid in the manipulation and insertion of the articulating joint
700 within an intervertebral space between adjacent vertebrae. The
surgical instrument (not shown) is preferably configured to hold
the articular components 702, 704 at a predetermined orientation
and spatial relationship relative to one another during
manipulation and insertion of the articulating joint 700, and to
release the articular components 702, 704 once properly positioned
between the adjacent vertebrae.
[0205] In one embodiment, and referring to FIGS. 49a and 49b, a
recess 714 is formed in the articular surface 708. A
circumferential edge 716 defining the recess 714 along the
articular surface 708 is in a concentric relationship with a recess
surface 718, yet has a smaller diameter relative to the recess
surface due to a diverging circular side 720 (FIG. 48b) of the
recess 714. Although described with reference to having a circular
shape, it is understood-that the recess 714 may take any number of
shapes such as square, triangular, or rectangular shapes.
[0206] Referring to FIGS. 50a and 50b, the recess 714 (FIG. 49b) is
designed to receive a portion of a modular projection member 722.
The projection member 722 includes a flange portion 724, which is
shaped to correspond to the shape of the recess 714. As such, the
flange portion 724 includes a diverging circumferential side 726,
which terminates at a substantially planar engagement surface 728.
The engagement surface 728 is adapted to engage the substantially
planar recess surface 718 (FIG. 49b). It is understood, however,
that although depicted as being substantially planar, the
engagement surface 728 and the recess surface 718 may take any
number of corresponding shapes. The diameter of the engagement
surface 728 is smaller than the diameter of the recess surface 718,
thereby allowing translation of the modular projection member 722
relative to the articular component 702.
[0207] The remaining portion of the modular projection member 722
is defined by a projection 730 having a convex shape, which may be
configured as a spherical-shaped ball (half of which is shown). It
should be understood that other configurations of the projection
730 are also contemplated, such as, for example, cylindrical,
elliptical or other arcuate configurations or possibly non-arcuate
configurations. It should also be understood that the remaining
portion of articular surface 708 may take on planar or non-planar
configurations, such as, for example, an angular or conical
configuration extending about the projection 224.
[0208] In one embodiment, the convex articular surface of the
projection 730 is interrupted by a surface depression or cavity 732
extending along the projection 730. In one embodiment, the surface
depression 732 is configured as a groove. However, it should be
understood that other types of surface depressions are also
contemplated, including no depression at all. One purpose of the
groove 732 is to facilitate the removal of matter disposed between
abutting portions of the articular components 702, 704. More
specifically, the groove 732 may aid in clearing out matter such
as, for example, particulate material, that is disposed between the
abutting articular surfaces of components 702, 704.
[0209] Referring to FIGS. 45 and 49b, a flange member or keel 740
extends from the bearing surface 710 and is configured for
disposition within a preformed opening in the adjacent vertebral
endplate (such as V.sub.I in FIG. 47). In one embodiment, the keel
740 extends perpendicularly from the bearing surface 710 and is
approximately centrally located along the bearing surface 710.
However, it should be understood that other positions and
orientations of the keel 740 are also contemplated.
[0210] In one embodiment, the keel 740 extends along substantially
the entire length of the support plate 706. Such an embodiment
would accommodate insertion of the articulating joint 700 using an
anterior approach. However, as discussed above, other approaches
such as lateral, transforaminal, and anterior-oblique approaches
are also contemplated for insertion of the prosthetic joint 700. In
a further embodiment, the keel 740 may be angled, tapered, or
configured in some other shape to facilitate the functional demands
of the keel. In still another embodiment, the keel 740 may be
configured as a winged keel, including a transverse portion (not
shown) extending across the main body portion of keel 740.
[0211] The keel 740 also includes a pair of openings 742 extending
therethrough to facilitate bone through-growth to enhance fixation
to the adjacent vertebra. However, it should be understood that any
number of openings 742 may be defined through keel 740, including a
single opening or three or more openings. It should also be
understood that the openings 742 need not necessarily extend
entirely through the keel 740, but may alternatively extend
partially therethrough. It should further be understood that the
keel 740 need not necessarily define any openings 742 extending
either partially or entirely therethrough. Additionally, although
the openings 742 are illustrated as having a circular
configuration, it should be understood that other sizes and
configurations of the openings 742 are also contemplated. As
discussed above, the surfaces of the articular component 702 that
are in direct contact with vertebral bone are preferably coated
with a bone-growth promoting substance. Specifically, the bearing
surface 710 and the surfaces of the keel 740 can be coated with
hydroxyapatite to promote bony engagement with the adjacent
vertebrae. As also discussed above, the bearing surface 710 and the
surfaces of keel 740 can be roughened prior to application of the
hydroxyapatite coating.
[0212] Referring to FIGS. 45-47, in one embodiment, the articular
component 704 includes a support plate 750 having an articular
surface 752 and an opposite bearing surface 754. Support plate 750
may be sized and shaped to substantially correspond to the size and
shape of the vertebral endplate of an adjacent vertebra. The
support plate 750 can include one or more notches 756 or other
types of indicia for receiving and engaging with a corresponding
portion of a surgical instrument, such as discussed above with
reference to articular component 702.
[0213] In one embodiment, the articular surface 752 includes a
recess 758 (FIG. 47), which has a convex shape, such as that of a
spherical-shaped socket. However, it should be understood that
other configurations of the recess 758 are also contemplated, such
as, for example, cylindrical, elliptical or other arcuate
configurations or possibly non-arcuate configurations. The
remaining portion of the articular surface 752 can be angled or
otherwise configured to facilitate the insertion and/or use of the
articulating joint 700.
[0214] Although the concave recess 758 is illustrated as having a
generally smooth, uninterrupted articular surface, it should be
understood that a surface depression or cavity may be defined along
a portion of the recess 758 to aid in clearing out matter, such as
particulate debris, that is disposed between the abutting articular
surfaces of articular components 702, 704. In such case, the convex
articular surface of the projection 730 may alternatively define a
generally smooth, uninterrupted articular surface. In another
embodiment, each of the convex projection 730 and the concave
recess 758 may define a surface depression to facilitate removal of
particulate matter disposed between the abutting articular
surfaces.
[0215] A flange member or keel 760, configured similar to the keel
740 of articular component 702, extends from the bearing surface
754. In one embodiment, the keel 760 extends perpendicularly from
the bearing surface 754 and is approximately centrally located
along bearing surface 754. However, it should be understood that
other positions and orientations of the keel 760 are also
contemplated. It should also be understood that the articular
component 704 may include two or more keels 760 extending from the
bearing surface 754.
[0216] In one embodiment, the keel 760 extends along substantially
the entire length of the support plate 750. Such an embodiment
would accommodate insertion of the prosthetic joint 700 using an
anterior approach. However, as discussed above, other approaches
such as lateral, transforaminal, and anterior-oblique approaches
are also contemplated for insertion of the prosthetic joint 700. In
a further embodiment, the keel 760 may be angled, tapered, or
configured in some other shape to facilitate the functional demands
of the keel. In still another embodiment, the keel 760 may be
configured as a winged keel, including a transverse portion (not
shown) extending across the main body portion of keel 760.
[0217] The keel 760 also includes a pair of openings 762 extending
therethrough to facilitate bone through-growth to enhance fixation
to the adjacent vertebra. However, it should be understood that any
number of openings 762 may be defined through keel 760, including a
single opening or three or more openings. It should also be
understood that the openings 762 need not necessarily extend
entirely through the keel 760, but may alternatively extend
partially therethrough. It should further be understood that the
keel 760 need not necessarily define any openings 762 extending
either partially or entirely therethrough. Additionally, although
the openings 762 are illustrated as having a circular
configuration, it should be understood that other sizes and
configurations of openings 762 are also contemplated. As discussed
above, the surfaces of the articular component 704 that are in
direct contact with vertebral bone are preferably coated with a
bone-growth promoting substance. Specifically, the bearing surface
754 and the surfaces of the keel 760 can be coated with
hydroxyapatite to promote bony engagement with the adjacent
vertebrae. As also discussed above, the bearing surface 754 and the
surfaces of keel 760 can be roughened prior to application of the
hydroxyapatite coating.
[0218] In some embodiments, one or both of the keels 740, 760 may
include a sharp forward edge, illustrated by edge 760a of FIGS. 45
and 46. By having such an edge, insertion of the keel 740, 760 into
the associated vertebral body is facilitated. Also, the edge 760a
can be of sufficient sharpness that the vertebral body does not
require a slot for receiving the keel 760, discussed in greater
detail below.
[0219] Referring to FIG. 45, the mobile-bearing prosthetic joint
700 is assembled by inserting the modular projection 722 member
into the recess 714 formed in the articular surface 708 of
articular component 702. Upon assemblage, the prosthetic joint 700
is ready to be inserted into the disc space S1 between adjacent
vertebral bodies V.sub.S, V.sub.I (FIG. 48).
[0220] Referring to FIG. 48, to accommodate insertion of the
prosthetic joint 700 within the intervertebral space S1, the
adjacent vertebral bodies V.sub.S, V.sub.I can be prepared to
accept the prosthetic joint 700 therebetween. For the configuration
of the prosthetic joint 700 of FIGS. 45-47, slots 770, 772 are
formed along the vertebral endplates of the vertebrae V.sub.S and
the vertebrae V.sub.I, respectively. The slots 770, 772 can be
created by the keels 740, 760 themselves, or can be prepared
beforehand by one or more of the methods discussed above.
[0221] Upon insertion into the disc space S1, the prosthetic joint
700 allows translational movement of the articular component 704
relative to the articular component 702 due to the engagement of
the modular projection 722 with the concave recess 758 of articular
component 704. For example, in FIG. 51, the modular projection
member 722 is shown in a posterior position (which would result in
movement of the articular component 704 in the posterior direction
P), while in FIG. 52, the modular projection member 722 is shown in
an anterior position (which would result in movement of the
articular component 704 in the anterior direction A). FIGS. 51 and
52 are of course only exemplary of the translational movement
allowed by the implementation of modular projection member 722 and
the corresponding recess 714, and thus, the amount of translational
movement of the modular projection member 722, and therefore the
articular component 704, relative to the articular component 702
can vary, including in directions other than P and A.
[0222] Furthermore, the positioning of the modular projection
member 722 within the recess 714 of the articular component 702
allows the modular projection to spin relative to the articular
component 702. Thus, in such an embodiment, the modular projection
member 722 adds the benefit of being able to impart rotation to the
articular component 704 (via the engagement with the recess 758)
independent of translational movement imparted to the articular
component 704. Such independent relationship between translational
and rotational movement adds to the amount of mobility experienced
at the prosthetic joint 700 relative to prosthetic joints for which
translational movement is dependent upon rotational movement and
vice versa.
[0223] The present disclosure has been described relative to
several preferred embodiments. Improvements or modifications that
become apparent to persons of ordinary skill in the art after
reading this disclosure are deemed within the spirit and scope of
the application. For example, the articulating components of the
above-described articulating joints may be reversed without
departing from certain aspects of the disclosure. Accordingly, it
is understood that several modifications, changes and substitutions
are intended in the foregoing disclosure and, in some instances,
some features of the disclosure will be employed without a
corresponding use of other features. It is also understood that all
spatial references, such as "longitudinal" and "transverse," are
for illustrative purposes only and can be varied within the scope
of the disclosure. Accordingly, it is appropriate that the appended
claims be construed broadly and in a manner consistent with the
scope of the disclosure.
* * * * *