U.S. patent application number 12/387963 was filed with the patent office on 2010-11-11 for stand alone anterior cage.
This patent application is currently assigned to Stryker Spine. Invention is credited to Alexandre B. de Moura, Thomas J. Errico, Christopher McDonnell, Rafail Zubok.
Application Number | 20100286777 12/387963 |
Document ID | / |
Family ID | 43062842 |
Filed Date | 2010-11-11 |
United States Patent
Application |
20100286777 |
Kind Code |
A1 |
Errico; Thomas J. ; et
al. |
November 11, 2010 |
Stand alone anterior cage
Abstract
The present invention teaches an improved spinal fusion implant
and method of implanting same. The implant includes a shell and an
insert, the insert capable of situating first and second plates of
the shell with respect to each other and of preventing unwanted
loosening of fasteners placed through the shell and into the
adjacent vertebral bodies. The method includes implanting a shell,
selecting an insert from a plurality of inserts, and placing an
insert between first and second plates of the shell.
Inventors: |
Errico; Thomas J.; (Summit,
NJ) ; de Moura; Alexandre B.; (Westbury, NY) ;
McDonnell; Christopher; (Sandy Hook, CT) ; Zubok;
Rafail; (Midland Park, NJ) |
Correspondence
Address: |
LERNER, DAVID, LITTENBERG,;KRUMHOLZ & MENTLIK
600 SOUTH AVENUE WEST
WESTFIELD
NJ
07090
US
|
Assignee: |
Stryker Spine
Cestas
FR
|
Family ID: |
43062842 |
Appl. No.: |
12/387963 |
Filed: |
May 8, 2009 |
Current U.S.
Class: |
623/17.11 ;
606/246; 606/279 |
Current CPC
Class: |
A61F 2/4455 20130101;
A61F 2002/30593 20130101; A61F 2220/0025 20130101; A61F 2310/00023
20130101; A61F 2002/30632 20130101; A61F 2002/305 20130101; A61F
2002/30594 20130101; A61F 2002/30616 20130101; A61F 2310/00017
20130101; A61F 2002/30845 20130101; A61B 17/8042 20130101; A61F
2002/30736 20130101; A61F 2002/30843 20130101; A61F 2002/30624
20130101; A61F 2002/30571 20130101; A61F 2/442 20130101; A61F
2002/30787 20130101; A61F 2002/4629 20130101 |
Class at
Publication: |
623/17.11 ;
606/246; 606/279 |
International
Class: |
A61F 2/44 20060101
A61F002/44; A61B 17/70 20060101 A61B017/70; A61B 17/88 20060101
A61B017/88 |
Claims
1. A spinal implant for fusing together first and second vertebral
bodies, the implant comprising: a first member having a first
surface for engaging the first vertebral body, a second surface,
and a first opening extending between the first and second
surfaces; a second member having a third surface for engaging the
second vertebral body, a fourth surface, and a second opening
extending between the third and fourth surfaces; a living hinge
connecting the first and second members and allowing for movement
of the first and second members with respect to one another; and an
insert disposed between the first and second members, the insert
covering the first and second openings about the second and fourth
surfaces.
2. The spinal implant of claim 1, wherein one of the second or
fourth surfaces includes a projection for retaining the insert
between the first and second members.
3. The spinal implant of claim 2, wherein each of the second and
fourth surfaces include projections.
4. The spinal implant of claim 1, wherein the insert is constructed
of bone.
5. The spinal implant of claim 1, wherein the insert is constructed
of a polymer.
6. The spinal implant of claim 1, wherein the insert is constructed
of a metal.
7. The spinal implant of claim 1, further comprising a first screw
disposed in the first opening and a second screw disposed in the
second opening.
8. The spinal implant of claim 7, wherein the insert includes a
portion for preventing back out of the first and second screws.
9. The spinal implant of claim 1, further comprising a third
opening extending between the first and second surfaces of the
first member, and a fourth opening extending between the third and
fourth surfaces of the second member.
10. The spinal implant of claim 9, wherein the insert includes a
main body, a first portion for covering the first and second
openings and a second portion for covering the third and fourth
openings.
11. The spinal implant of claim 10, wherein the main body of the
insert includes an aperture for engagement with a tool.
12. The spinal implant of claim 10, further comprising a first
screw disposed in the first opening, a second screw disposed in the
second opening, a third screw disposed in the third opening, and a
fourth screw disposed in the fourth opening.
13. The spinal implant of claim 12, wherein the insert includes a
first portion for preventing back out of the first and second
screws and second portion for preventing back out of the third and
fourth screws.
14. The spinal implant of claim 13, further comprising a bone
growth aperture extending through the first member, the insert, and
the second member.
15. The spinal implant of claim 1, wherein the first and second
surfaces are located in non-parallel planes.
16. The spinal implant of claim 15, wherein the insert forces
non-parallel relationship between the first and second
surfaces.
17. A spinal implant for implantation between first and second
vertebral bodies, the implant comprising: a shell including: a
first plate for engaging the first vertebral body, the first plate
including a first hole formed therethrough; a second plate for
engaging the second vertebral body, the second plate including a
second hole formed therethrough; and a resilient member connecting
the first and second plates; and an insert including: a main body;
and a portion capable of covering at least one of the first or
second holes when the insert is disposed between the first and
second plates.
18. The spinal implant of claim 17, further comprising a first
screw disposed in the first hole and second screw disposed in the
second hole.
19. The spinal implant of claim 18, wherein the portion is capable
of preventing back out of both of the first and second screws when
the insert is disposed between the first and second plates.
20. The spinal implant of claim 17, wherein the insert is
constructed at least partially from materials selected from the
group consisting of bone, polymer, and metal.
21. The spinal implant of claim 17, wherein one of the first or
second plates includes a projection for retaining the insert
between the first and second plates.
22. The spinal implant of claim 21, wherein each of the first and
second plates include projections.
23. The spinal implant of claim 17, further comprising a third hole
formed through the first plate and a fourth hole formed through the
second plate.
24. The spinal implant of claim 23, furthering comprising a first
screw disposed in the first hole, a second screw disposed in the
second hole, a third screw disposed in the third hole, and fourth
screw disposed in the fourth hole.
25. The spinal implant of claim 24, wherein the insert includes a
first portion for preventing back out of the first and second
screws and second portion for preventing back out of the third and
fourth screws.
26. The spinal implant of claim 17, further comprising a bone
growth aperture extending through the first member, the insert, and
the second member.
27. The spinal implant of claim 17, wherein the main body of the
insert includes an aperture for engagement with a tool.
28. The spinal implant of claim 17, wherein the first and second
plates are located in non-parallel planes.
29. The spinal implant of claim 28, wherein the insert forces
non-parallel relationship between the first and second plates.
30. A method of fusing together first and second vertebral bodies,
the method comprising: preparing a space between the first and
second vertebral bodies to accept a spinal implant; implanting a
shell, the shell including a first plate, and second plate, and a
living hinge connecting the first and second plates; placing a
first screw through the first plate and into the first vertebral
body; placing a second screw through the second plate and into the
second vertebral body; and inserting an insert between the first
and second plates, wherein the insert prevents back out of the
first and second screws.
31. The method of claim 30, wherein the inserting step causes the
first and second plates to move with respect to each other, wherein
the movement between the first and second plates is translated to
the first and second vertebral bodies.
32. The method of claim 30, further comprising the step of choosing
the insert from a plurality of inserts.
33. The method of claim 30, further comprising the steps of placing
a third screw through the first plate and into the first vertebral
body, and placing a fourth screw through the second plate and into
the second vertebral body.
34. The method of claim 33, wherein the insert prevents back out of
the first, second, third, and fourth screws.
35. The method of claim 30, further comprising the step of
retaining the insert between the first and second plates.
36. The method of claim 35, wherein the retaining step includes
engaging the insert with projections formed on the first and second
plates.
37. The method of claim 30, further comprising the step of allowing
bone growth through an aperture formed through the first plate, the
insert, and the second plate.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention is directed to spinal implants, and
more particularly, spinal fusion implants.
[0002] The deterioration of vertebral bodies and/or vertebral discs
is a major cause of back and neck pain in many patients. Through
the years, many different techniques for restoring the natural
anatomical spacing in the spine and thereby alleviating this pain
have been developed and practiced by surgeons. For instance,
implants and techniques for implanting such implants have been
designed to preserve motion between adjacent vertebral bodies.
These motion preserving implants are adapted to emulate a removed
spinal disc. Examples of such implants (and the methods of
implanting same) are disclosed in U.S. Pat. Nos. 6,989,032 ("the
'032 patent") and 7,169,182 ("the '182 patent"), the disclosures of
which are hereby incorporated by reference herein. Nonetheless,
even given the success of such motion preserving devices, it is
still sometimes necessary to fuse adjacent vertebral bodies so that
no movement is permitted therebetween.
[0003] Spinal fusion surgery typically involves removing the disc
material from between adjacent vertebral bodies, which thereby
creates an empty intervertebral space. In this space is implanted
an implant or cage that is then fixably mounted to the end plates
of the adjacent vertebral bodies. Bone growth is often permitted
through the implant, and is in fact sometimes provoked by the
placement of bone growth inducing substances within the cage.
However, even given this bone growth through the cage, it is
sometimes necessary to at least initially mount the cage to the
vertebral bodies through the use of fixation elements such as
screws. Furthermore, it has also determined that providing an
angled implant or cage can aid in returning the adjacent vertebral
bodies to their natural "lordotic" angle.
[0004] Even if a surgeon initially determines that he or she wishes
to perform a motion preserving surgery on a patient, sometimes it
becomes apparent during the procedure that a fusion procedure would
benefit the patient. Likewise, surgeons often recognize the need to
fuse vertebral bodies at levels adjacent to the initial one in
question. Thus, it is desirable to have a fusion implant that can
easily be implemented and implanted utilizing the tools and
procedure used in a motion preserving surgery. Moreover, it is also
desired to have such a fusion implant be easily implanted using
those tools, easily affixed to the intervertebral bodies, and
prevented from becoming dislodged even after just initially being
implanted.
[0005] Therefore, there exists a need for an improved spinal fusion
device.
SUMMARY OF THE INVENTION
[0006] A first aspect of the present invention is a spinal implant
for fusing together first and second vertebral bodies. In
accordance with one embodiment of this first aspect, the implant
includes a first member having a first surface for engaging the
first vertebral body, a second surface, and a first opening
extending between the first and second surfaces. The implant also
includes a second member having a third surface for engaging the
second vertebral body, a fourth surface, and a second opening
extending between the third and fourth surfaces. A living hinge
connecting the first and second members is also included and
preferably allows for movement of the first and second members with
respect to one another. Finally, an insert is disposed between the
first and second members, the insert covering the first and second
openings about the second and fourth surfaces.
[0007] In accordance with other embodiments of the first aspect,
the second and fourth surfaces may include a projection for
retaining the insert between the first and second members, and in
other embodiments each of the second and fourth surfaces include
these projections. The insert may be constructed of bone, polymer,
metal, or the like. Furthermore, the implant may include a first
screw disposed in a first opening and a second screw disposed in a
second opening, and the insert may include a portion for preventing
backout of the first and second screws. In still further
embodiments, the first member may include a third opening extending
between the first and second surfaces, and the second member may
include a fourth opening extending between the third and fourth
surfaces. In this embodiment, the insert may include a main body, a
first portion for covering the first and second openings, and a
second portion for covering the third and fourth openings. The
insert may also include an aperture for engagement with a tool. In
accordance with this further embodiment, a first screw may be
disposed in the first opening, a second screw may be disposed in a
second opening, a third screw may be disposed in the third opening,
and a fourth screw may be disposed in the fourth opening. The
insert includes a first portion for preventing backout of the first
and second screws and a second portion for preventing backout of
the third and fourth screws. Finally, in accordance with certain
embodiments, the implant may include a bone growth aperture
extending through the first member, the insert, and the second
member, and the implant may be designed to provide a nonparallel
relationship between the first and second surfaces, such that the
vertebral bodies exhibit a similar relationship.
[0008] The second aspect of the present invention is also directed
to a spinal implant for implantation between first and second
vertebral bodies. In accordance with one embodiment of this second
aspect, the implant includes a shell and an insert. The shell
preferably includes a first plate for engaging the first vertebral
body, the first plate including a first hole formed therethrough, a
second plate for engaging the second vertebral body, the second
plate including a second hole formed therethrough, and a resilient
member connecting the first and second plates. The insert on the
other hand may include a main body and a portion capable of
covering at least one of the first or second holes when the insert
is disposed between the first and second plates.
[0009] In accordance with other embodiments of the second aspect,
the implant may include a first screw disposed in the first hole,
and a second screw disposed in the second hole. A portion of the
insert is preferably capable of preventing backout of both of the
first and second screws when the insert is disposed between the
first and second plates. The insert may be constructed at least
partially from materials selected from the group consisting of
bone, polymer, and metal. At least one of the first and second
plates may include a projection for retaining the insert between
the first and second plates, but in certain embodiments both the
first and second plates may include such projections. The implant
may also include a third hole formed through the first plate and a
fourth formed through the second plate, and a first screw disposed
in the first hole, a second screw disposed in the second hole, a
third screw disposed in the third hole, and a fourth screw disposed
in the fourth hole. The insert may include a first portion for
preventing backout of the first and second screws and a second
portion for preventing backout of the third and fourth screws. A
bone growth aperture may extend through the first member, the
insert, and the second member. The insert may include an aperture
for engagement with the tool. Preferably, the first and second
plates are located in nonparallel planes, and such may be caused by
the insert being placed therebetween.
[0010] The third aspect of the present invention is a method of
fusing together first and second vertebral bodies. In accordance
with one embodiment of the present invention, the method includes
the steps of preparing a space between the first and second
vertebral bodies to a spinal implant, implanting a shell, the shell
including a first plate, a second plate, and a living hinge
connecting the first and second plates, placing a first screw
through the first plate and into the first vertebral body, placing
a second screw through the second plate and into the second
vertebral body, and inserting an insert between the first and
second plates, wherein the insert prevents backout of the first and
second screws.
[0011] In accordance with other embodiments of this third aspect,
the inserting step may cause the first and second plates to move
with respect to each other and such movement between the first and
second plates is preferably translated to the first and second
vertebral bodies. The method may also include the step of choosing
an insert from a plurality of inserts. Moreover, the method may
include the step of placing a third screw through the first plate
and into the first vertebral body, and the step of placing a fourth
screw through the second plate in the intervertebral body.
Preferably, the insert prevents backout of the first, second,
third, and fourth screws. The method may also include the step of
retaining the insert between the first and second plates, where
this retaining step may include engaging the insert with
projections formed on the first and second plates. Finally, the
method may also include the step of allowing bone growth through an
aperture formed through the first plate, the insert, and the second
plate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] A more complete appreciation of the subject matter of the
present invention and the various advantages thereof can be
realized by reference to the following detailed description with
reference to the accompanying drawings in which:
[0013] FIG. 1 is a perspective view of an intervertebral fusion
implant according to one embodiment of the present invention.
[0014] FIG. 2 is a front view of the implant shown in FIG. 1.
[0015] FIG. 3 is a rear view of the implant shown in FIG. 1.
[0016] FIG. 4 is a right side view of the implant shown in FIG.
1.
[0017] FIG. 5 is a top view of the implant shown in FIG. 1.
[0018] FIG. 6 is a cross-sectional view of the implant shown in
FIG. 1 taken along line A-A of FIG. 5.
[0019] FIG. 7 is a perspective view of a shell from the implant of
FIG. 1.
[0020] FIG. 8 is a front view of the shell shown in FIG. 7.
[0021] FIG. 9 is a right side view of the shell shown in FIG.
7.
[0022] FIG. 10 is a perspective view of an insert from the implant
shown in FIG. 1.
[0023] FIG. 11 is a front view of the insert shown in FIG. 10.
[0024] FIG. 12 is a rear view of the insert shown in FIG. 10.
[0025] FIG. 13 is a right side view of the insert shown in FIG.
10.
[0026] FIG. 14 is a top view of the insert shown in FIG. 10.
[0027] FIG. 15 is a prospective view of adjacent vertebral bodies
having been prepared to receive a fusion implant.
[0028] FIG. 16 is a prospective view of the vertebral bodies of
FIG. 15 having the shell shown in FIG. 7 implanted
therebetween.
[0029] FIG. 17 is a prospective view similar to the one shown in
FIG. 16 with screws implanted through the shell and into the
adjacent vertebral bodies.
[0030] FIG. 18 is a view similar to that of FIG. 17 with the insert
of FIG. 10 partially implanted.
[0031] FIG. 19 is a view similar to FIG. 18 with the insert
completely implanted.
DETAILED DESCRIPTION
[0032] Referring to the drawings, wherein like reference numerals
refer to like elements, FIGS. 1-6 depict a first embodiment
intervertebral fusion device or spinal implant for fusing together
first and second vertebral bodies, designated generally by
reference numeral 10. As is shown in the drawings, implant 10
includes a shell 12 and an insert 14. Moreover, implant 10 is also
provided with a plurality of fasteners (shown in the drawings as
screws 16a-d) for placement through portions of the shell and into
adjacent vertebral bodies. However, one of ordinary skill in the
art would readily recognize that other types of fasteners could be
utilized, e.g., pins or the like. The specifics of each of the
components of implant 10, as well as their operation and use will
be discussed more fully below.
[0033] As is shown in FIGS. 1-6 and even more specifically shown in
FIGS. 7-9, shell 12 includes a first plate or member 18, a second
plate or member 20, and a pair of resilient or living hinge members
22a and 22b. First member 18 includes a first surface 24 for
engaging an upper vertebral body, a second surface 26 for
engagement with insert 14, a plurality of bone growth apertures
collectively referred to by reference numeral 28, and two fastener
holes 30 and 32. First surface 18 is formed with a plurality of
vertebral body engaging members, including teeth 34 and surfaces
36. Second surface 26 is formed with countersunk surfaces 38 and 40
in the vicinity of fastener holes 30 and 32, respectively, and a
projection 42 extending toward second member 20. Similarly, second
member 20 includes a third surface 44 for engagement with the lower
vertebral body, a fourth surface 46 for engagement with insert 14,
a plurality of bone growth apertures collectively referred to with
reference numeral 48, and two fastener holes 50 and 52. Also in a
similar fashion to first member 18, third surface 44 is formed with
vertebral engaging elements including teeth 54 and surfaces 56,
while second surface 46 includes countersinks 58 and 60 in the
vicinity of fastener holes 50 and 52, respectively, and projection
62 extending toward first 18. Moreover, as is best shown in FIG. 8,
extending from second surface 26 of first member 18 are extensions
64 and 66, and extending from fourth surface 46 of second member 20
are extensions 68 and 70. These extensions create a substantially
rectangular space 72 for reception of insert 14, as will be
discussed more fully below. First plate 18 may also include
apertures 74 and second plate 20 may include apertures 76, which
are utilized in engaging an insertion tool.
[0034] Resilient members 22a and 22b are shown as living hinges.
Essentially, these elements are curved elements being made of a
material capable of bending upon an application of force to one of
or both of first and second members 18 and 20. For example, upon
placement of differently sized inserts 14 between the first and
second members, hinges 22a and 22b are capable of allowing for the
expansion or the contraction of the device. While shown in the
drawings as being composed of the same material as first and second
members 18 and 20, it is noted that members 22a and 22b can be
constructed of different materials. Likewise, the overall shape of
members 22a and 22b can vary from the rounded structures shown in
the drawings.
[0035] In the embodiment shown in the drawings, shell 12 is formed
of titanium, but it is noted that other materials such as stainless
steel, polymer, or the like can be utilized. It is also noted that
the specific configuration of shell 12 may widely vary in different
embodiments of the present invention. For example, the overall
shape of the shell which is shown as being similar in nature to the
implants shown and described in the '032 and '182 patents, but may
vary depending upon the different portion of the spine in which it
is to be implanted or the design of an implant of which it is to
emulate. The vertebral engaging surfaces may also vary, including
the specific vertebral engaging members disposed thereon.
Furthermore, the apertures extending through the first and second
members may vary, including the overall amount of bone growth
apertures and screw holes. While fastener holes 30, 32, 50, and 52
are shown as being angled, other angles and/or perpendicular
configurations are contemplated. Likewise, the configuration of
projections 42 and 62 may also vary as can the space 72 for
accepting insert 14.
[0036] Turning now to the configuration of insert 14, it is noted
that such is preferably of a unitary construction. However, in
other embodiments, different configurations are contemplated. With
specific reference to FIGS. 10-14, insert 14 includes a main body
80 having a front face 82, a rear face 84, a top surface 86, a
bottom surface 88, a left side surface 90, and a right side surface
92. Extending from the left and right are flanges 94 and 96, such
that they form a continuous surface with front face 82, flange 94
includes a rear face 95, and flange 96 includes a rear face 97. In
addition, as is shown in the drawings, formed through top surface
and bottom surface is an aperture 98, which generally cooperates
with apertures 28 and 48 of first and second members 18 and 20,
respectively, in order to provide for a bone growth channel between
adjacent vertebral bodies. Finally, front face includes an aperture
100, which is shown as being threaded for engagement with an
insertion tool (not shown).
[0037] It is to be understood that insert 14 may widely vary from
that which is shown in the drawings. For one, insert 14 may vary to
properly cooperate with variations of shell 12. Certain portions of
insert 14 may also vary and still be capable of cooperating with
shell 12 as shown. For instance, flanges 94 and 96 may simply be
extensions of front face 82 (i.e., rectangular) rather than the
rounded structures that are illustrated in the drawings. Moreover,
aperture 100 may be configured differently to engage an insertion
tool (not shown). For instance, insert 14 may include an aperture
100 which is meant to cooperate with a spring detent or the like.
Additionally, insert 14 may include a differently configured
aperture 98 (or multiple apertures) for cooperation with like
apertures formed in first and second members 18 and 20 of shell 12.
Finally, insert 14 may be constructed of many different types of
materials. For example, it is contemplated to form insert 14 of
PEEK.TM. or of a biological material such as bone. In the case of
the latter, the patient's own bone may be utilized to form insert
14 by any one of many known processes.
[0038] During a surgical procedure in which the above-discussed
implant 10 is implanted, the surgeon first sees to the preparation
of the intervertebral space between the adjacent vertebral bodies
in order to be capable of receiving shell 12. This is shown in FIG.
15 and may include the removal of disc material and/or the
preparation of the end plates of the vertebral bodies. Shell 12 is
then inserted in the prepared space (see FIG. 16). In this regard,
an insertion tool (not shown) may be engaged with apertures 74
and/or 76 of the first or second plates, or shell 12 may simply be
placed by hand into the space. The above-discussed features of
surfaces 24 and 44 (i.e., spikes 34 and surfaces 36) may aid in the
retainment of shell 12 between the adjacent vertebral bodies. Once
in place, fasteners (such as screws 16a-16d shown in FIGS. 1-6) may
be placed through fastener holes 30, 32, 50, and 52 and into the
adjacent vertebral bodies (see FIG. 17). Once again, it is noted
that fastener holes 30, 32, 50, and 52 may be angled in any fashion
to allow for specific placement of the fasteners through shell 12
and into the intervertebral bodies. It is noted that although the
fasteners are shown in FIGS. 1-6 as screws having specific
configurations, many different fastener configurations may be
employed in fixing shell 12 to adjacent vertebral bodies, including
differently configured screws.
[0039] With shell 12 in place, insert 14 may then be placed between
first and second plates 18 and 20, preferably into above-discussed
space 72. Insert 14 partially inserted into shell 12 is shown in
FIG. 18. In placing insert 14, a tool (not shown) may be engaged
with the threading of aperture 100, or, in the case of a
differently configured aperture, another type of connection. Prior
to engaging the insert with the tool, a surgeon may select one
insert 14 from a plurality of differently sized and/or shaped
inserts. These different inserts ultimately affects the disposition
of plates 18 and 20 of shell 12. For example, a larger sized insert
would increase the distance between plates 18 and 20, while
differently shaped inserts may affect the amount of angle between
the plates. Thus, depending upon the spacing or lordotic angle
desired between adjacent vertebral bodies, different inserts having
different sizes and/or differently angled upper and lower surfaces
may be selected.
[0040] Once the surgeon makes the proper determination of the
insert to utilize, it is coupled with a tool (not shown) or placed
by hand between plates 18 and 20 (see FIG. 18). This placement of
the insert preferably moves plates 18 and 20, and thusly the
adjacent vertebral bodies to the position desired. Living hinges
22a and 22b allow for this movement while at the same time forcing
plates 18 and 20 toward insert 14. At a certain point, front face
of insert 14 is pushed past projections 42 and 62 so that the
insert is forcibly maintained within space 72 of shell 12 (see FIG.
19). In this regard, it is noted that projections 42 and 62 are
designed as ramps, which preferably allow for the easy insertion of
insert 14 within space 72. However, once front face of insert 14
passes projections 42 and 62, the insert is thereby retained within
the space. It is noted that other configurations for projections 42
and 62 may be employed. Once in this position, flanges 94 and 96 of
insert 14 are disposed at least partially over a portion of the
fasteners placed within fastener holes 30, 32, 50, and 52. In the
preferred embodiment shown in the drawings, flanges 94 and 96 are
placed over the heads of screws 16a-16d (best shown in FIG. 2).
This final position for insert 14 and its projections preferably
prevents the loosening or backout of the screws that may occur. In
other words, flanges 94 and 96 prevent the screws from coming out
of the vertebral bodies.
[0041] As is mentioned above, insert 14 may be made of various
materials. For example, the insert may be constructed at least
partially of metal, polymer, and/or bone material. In the latter
case, insert 14 may encourage growth of bone through aperture 28,
aperture 98, and aperture 48 to thereby fuse the adjacent vertebral
bodies. Furthermore, it is contemplated that bone growth including
substances may be placed within these apertures (or one of the
apertures) in order to even further facilitate or, in the case of
inserts constructed of nonbone material, promote such growth. It is
contemplated that other embodiments of shell 12 and insert 14 may
include additional apertures which promote further grown from
adjacent vertebral bodies therethrough.
[0042] Although the invention herein has been described with
reference to particular embodiments, it is to be understood that
these embodiments are merely illustrative of the principles and
applications of the present invention. It is therefore to be
understood that numerous modifications may be made to the
illustrative embodiments and that other arrangements may be devised
without departing from the spirit and scope of the present
invention as defined by the appended claims.
* * * * *