U.S. patent application number 10/655571 was filed with the patent office on 2004-07-22 for intervertebral cage and method of use.
This patent application is currently assigned to DePuy AcroMed, Inc.. Invention is credited to Sazy, John A..
Application Number | 20040143330 10/655571 |
Document ID | / |
Family ID | 23871125 |
Filed Date | 2004-07-22 |
United States Patent
Application |
20040143330 |
Kind Code |
A1 |
Sazy, John A. |
July 22, 2004 |
Intervertebral cage and method of use
Abstract
An intervertebral prosthesis for implantation between adjacent
vertebrae of the human spine is shown. The prosthesis is formed as
a unitary cage body configured and sized to be inserted between
adjacent vertebrae in a single step implantation procedure. The
cage body is banana shaped as viewed from above, the body having an
exterior surface and an interior surface, the interior surface
defining an internal recess for receiving cancellous bone material
during an implantation procedure. The cage body can be formed as an
interlinked mesh.
Inventors: |
Sazy, John A.; (Arlington,
TX) |
Correspondence
Address: |
HAMILTON, BROOK, SMITH & REYNOLDS, P.C.
530 VIRGINIA ROAD
P.O. BOX 9133
CONCORD
MA
01742-9133
US
|
Assignee: |
DePuy AcroMed, Inc.
|
Family ID: |
23871125 |
Appl. No.: |
10/655571 |
Filed: |
September 4, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10655571 |
Sep 4, 2003 |
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09471312 |
Dec 23, 1999 |
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6648915 |
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Current U.S.
Class: |
623/17.11 ;
606/247; 606/264; 606/907; 606/908; 606/910 |
Current CPC
Class: |
Y10S 623/902 20130101;
A61B 17/7032 20130101; A61F 2230/0015 20130101; A61F 2002/30308
20130101; A61F 2002/30787 20130101; A61F 2002/30593 20130101; A61F
2002/30616 20130101; A61F 2/30965 20130101; A61F 2002/30133
20130101; A61F 2/442 20130101; A61F 2/4465 20130101; A61F 2002/2835
20130101; A61B 17/701 20130101; A61F 2310/00017 20130101; A61F
2230/0063 20130101; A61F 2310/00023 20130101 |
Class at
Publication: |
623/017.11 ;
606/061 |
International
Class: |
A61F 002/44 |
Claims
What is claimed is:
1. An intervertebral prosthesis for implantation between adjacent
vertebrae of the human spine, comprising: a unitary body that is
banana-shaped as viewed from above, the body having an exterior
surface and an interior surface, the interior surface defining an
interior recess; and wherein the unitary body includes upper and
lower edges that each form smoothly-sloping surfaces.
2. The intervertebral prosthesis of claim 1, wherein the banana
shape of the unitary body includes a front arc that has a first
radius of curvature and a back arc that includes a second radius of
curvature.
3. The intervertebral prosthesis of claim 2, wherein the first
radius of curvature is equal to or less than the second radius of
curvature.
4. The intervertebral prosthesis of claim 3, wherein the first
radius of curvature is equal to the second radius of curvature.
5. The intervertebral prosthesis of claim 3, wherein the first
radius of curvature is less than the second radius of
curvature.
6. The intervertebral prosthesis of claim 5, wherein the first and
the second radii of curvature extend from a single point of
rotation.
7. The intervertebral prosthesis of claim 2, wherein the unitary
body defines openings about a circumference of the body.
8. The intervertebral prosthesis of claim 7, wherein the openings
are evenly spaced about the circumference of the body.
9. The intervertebral prosthesis of claim 8, wherein the upper and
lower edges include bands that form a serpentine arrangement of an
interlinked mesh.
10. The intervertebral prosthesis of claim 8, wherein the defined
openings are quadrilaterals.
11. The intervertebral prosthesis of claim 8, wherein the
quadrilaterals are parallelograms.
12. The intervertebral prosthesis of claim 8, wherein the
parallelograms are rhombuses.
13. The intervertebral prosthesis of claim 8, wherein the
intervertebral prosthesis includes at least one material selected
from the group consisting of a metal, a carbon fiber, and a
polymer.
14. The intervertebral prosthesis of claim 13, wherein the
intervertebral prosthesis includes a metal.
15. The intervertebral prosthesis of claim 14, wherein the metal
includes at least one member selected from the group consisting of
titanium and metal alloy.
16. The intervertebral prosthesis of claim 15, wherein the metal
includes a metal alloy.
17. The intervertebral prosthesis of claim 16, wherein the metal
alloy is a stainless steel.
18. The intervertebral prosthesis of claim 13, wherein the
intervertebral prosthesis includes a carbon fiber.
19. The intervertebral prosthesis of claim 13, wherein the
intervertebral prosthesis includes a polymer.
20. The intervertebral prosthesis of claim 19, wherein the polymer
is a bioreabsorbable polymer.
21. The intervertebral prosthesis of claim 20, wherein the
bioreabsorbable polymer includes at least one member selected from
the group consisting of polyglycotic acid and polylactic acid.
22. The intervertebral prosthesis of claim 19, wherein the polymer
includes polymethylmethacylates.
23. The intervertebral prosthesis of claim 22, wherein the
polymethylmethacylate is blended with an antibiotic.
24. The intervertebral prosthesis of claim 13, wherein the
intervertebral prosthesis has a width in a range of between about
24 mm and about 28 mm.
25. The intervertebral prosthesis of claim 24, wherein the
intervertebral prosthesis has a length in a range of between about
8 mm and about 10 mm.
26. The intervertebral prosthesis of claim 25, wherein the
intervertebral prosthesis has a height in a range of between about
10 mm and about 16 mm.
27. The intervertebral prosthesis of claim 26, wherein the front
arc of the prosthesis has a thickness in a range of between about
1.5 mm and about 2 mm.
28. The intervertebral prosthesis of claim 2, wherein the front arc
and the back arc are continuous.
Description
RELATED APPLICATION
[0001] This application is a continuation of U.S. application Ser.
No. 09/471,312, filed Dec. 23, 1999.
[0002] The entire teachings of the above application are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present invention relates generally to a human spinal
implant device for implantation into intervertebral space between
adjacent vertebral bones and to a surgical method for installing
such a spinal implant assembly.
[0005] 2. Description of the Prior Art
[0006] Genetic or developmental irregularities, trauma, chronic
stress, tumors, and degenerative wear are typical causes which can
result in spinal pathologies for which surgical intervention is
necessary. Various devices and techniques are disclosed in the
prior art for immobilizing and/or fusing adjacent bones by
implanting artificial devices in or on the spinal column. The
region of the back which needs to be immobilized, as well as the
individual variations in anatomy, determine the appropriate
surgical protocol and implantation device which is best suited for
the case at hand. Where a failure of the intervertebral disc is
concerned, the inter-body fusion implant is often chosen.
[0007] An inter-body fusion maintains disc height, helps to protect
the nerve root and restores weight-bearing ability to anterior
structures. The fusion also restores the annular region of the
spine to tension and immobilizes the unstable, degenerated
intervertebral disc. Anterior approaches and fusion in the cervical
region have gained wide acceptance by both neurosurgeons and
orthopedic surgeons as treatment for herniated discs, trauma and
related degenerative conditions. In the case of lower lumbar spine
problems, such techniques have had more sporadic success. Recently,
pedicel screws and rods have allowed surgeons to reduce
degenerative conditions and immobilize the motion segment, but have
not eliminated the need for weight-bearing support for the anterior
spinal column.
[0008] The prior art implant techniques have generally involved two
component implant assemblies. The surgical procedures for
installing such devices can be complicated and traumatic to the
patient. Although X-ray imaging can be used to determine the
approximate location of the respective two component assemblies,
alignment of the prostheses can obviously be of major concern.
[0009] Accordingly, it is an object of the present invention to
provide a new and improved single component inter-body fusion cage
which overcomes known deficiencies of the prior art while providing
improved overall results.
SUMMARY OF THE INVENTION
[0010] The apparatus of the invention is an intervertebral
prosthesis for implantation between adjacent vertebrae of the human
spinal column. The prosthesis comprises a unitary body configured
and sized to be inserted between adjacent vertebrae in a single
step implantation procedure. The body is banana-shaped as viewed
from above and has an exterior surface and an interior surface, the
interior surface defining an internal recess for receiving
cancellous bone material during an implantation procedure.
Preferably, the unitary body is a cage which is formed as
interlinked mesh. Most preferably, the banana-shaped cage body is a
ring of metal having evenly spaced openings about a circumference
of the body. The preferred cage body is formed of a hard metal
alloy, such as a titanium alloy. The intervertebral prosthesis is
selectively sized to fit within a vertebral disk space of a human
anatomy allowing adequate space for additional cancellous bone
anterior to the cage body within the disk space.
[0011] The method of the invention facilitates inter-body fusion in
the vertebral column by providing an improved prosthesis and method
of installation. A space is first prepared for receiving a
prosthetic device between two vertebrae. The banana-shaped spinal
cage body is then surgically inserted into the space between two
vertebrae. The banana-shaped cage body has an exterior surface and
an interior surface, the interior surface defining an internal
recess for receiving cancellous bone material during an
implantation procedure. Preferably, the cage body is a ring of
metal having evenly spaced openings about a circumference of the
body. The cage body forms an interlinked mesh. The preferred cage
body is formed of a hard metal alloy. Preferably, the cage body is
formed of a titanium alloy.
[0012] Additional objects, features and advantages will be apparent
in the written description as follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The foregoing and other objects, features and advantages of
the invention will be apparent from the following more particular
description of preferred embodiments of the invention, as
illustrated in the accompanying drawings in which like reference
characters refer to the same parts throughout the different views.
The drawings are not necessarily to scale, emphasis instead being
placed upon illustrating the principles of the invention.
[0014] FIG. 1 is a simplified side view of the human anatomy,
showing the spinal process;
[0015] FIG. 2 is a close up, perspective view of the spinal implant
of the invention;
[0016] FIG. 3 is a cross sectional view of the spinal implant of
FIG. 2, taken along line II-II, and illustrating the
cross-sectional thickness of the device of the invention;
[0017] FIG. 4 is a top view of the banana-shaped device of the
invention showing certain of the dimensions thereof;
[0018] FIG. 5 is a perspective view of two of the prior art devices
used as spinal prostheses;
[0019] FIG. 6 is a top, simplified view of the banana-shaped cage
of the invention in place upon the lumbar vertebrae of the human
anatomy;
[0020] FIG. 7 is a similar view showing the placement of cancellous
material within and anterior to the banana-shaped implant of the
invention;
[0021] FIG. 8 shows the placement of prior art devices within the
vertebral region;
[0022] FIG. 9 illustrates the possible misalignment of the prior
art devices in the vertebral space and schematically illustrating
the possibility of asymmetric forces acting upon the device:
[0023] FIG. 10 is an isolated view of the intervertebral cage of
the invention in place within the vertebral space;
[0024] FIG. 11 is a simplified side view showing the placement of
the cage of the invention within the vertebral space;
[0025] FIG. 12 is a posterior view of the human spinal column
showing placement screws which are used during the discectomy
process;
[0026] FIG. 13 is a side, partial perspective view of the human
spinal column showing the use of an expansion tool to spread the
L-4 and L-5 vertebrae;
[0027] FIG. 14 is a side, partial cross-sectional view of the human
spine, showing the removal of tissue to prepare the disc space for
receiving the prosthesis of the invention;
[0028] FIG. 15 is a posterior view of the spinal region showing the
installation of the banana-shaped prosthesis of the invention;
[0029] FIG. 16 is a view similar to FIG. 15 but showing the
insertion of additional cancellous bone material within the disc
space anterior to the cage implant;
[0030] FIG. 17 is a view similar to FIG. 13 but showing the use of
the compression tool to compress the installed prosthesis and
associated vertebrae;
[0031] FIG. 18 is a simplified detail view of the insertion of the
cage of the invention, illustrating the curved disc space and
removed tissue;
[0032] FIG. 19 is a detail side view illustrating the placement of
the cage of the invention within the intervertebral space; and
[0033] FIG. 20 is a back view showing the placement of the cage
within the disc space.
DETAILED DESCRIPTION OF THE INVENTION
[0034] A description of preferred embodiments of the invention
follows.
[0035] The bones and connective tissue of an adult human spinal
column consists of more than 20 discrete bones coupled sequentially
to one another by a tri-joint complex which consists of an anterior
disc and the two posterior facet joints, the anterior discs of
adjacent bones being cushioned by cartilage spacers referred to as
intervertebral discs.
[0036] These more than 20 bones are anatomically referred to as
being members of one of four classifications: cervical, thoracic,
lumbar, or sacral. The cervical portion of the spine, which
comprises the top of the spine, up to the base of the skull,
includes the first 7 vertebrae. The intermediate 12 bones are the
thoracic vertebrae and connect to the lower spine comprising the 5
lumbar vertebrae. The base of the spine is the sacral bones. The
component bones of the cervical spine are generally smaller than
those of the thoracic spine, which are in turn smaller than those
of the lumbar region. The sacral region connects laterally to the
pelvis. FIG. 1 is a simplified schematic of the human anatomy
showing the spinal column 11 and intervertebral disc space 13
which, in this case, is at approximately the L4-L5 location.
[0037] The spinal column of bones is highly complex, serving to
house and protect critical elements of the nervous system having
countless peripheral nerves and circulatory bodies in close
proximity. Surgical procedures are therefore delicate and demanding
by their very nature. In the case of spinal pathologies for which
surgical intervention is necessary, particularly with respect to
failure of the intervertebral disc, the interbody fusion implant
has found acceptance in the field because such devices can be
implanted into the anterior of the spine and maintain disc height,
protect the nerve root and restore weight bearing ability to the
anterior structures. Typically a pair of elements were implanted.
The elements themselves were sometimes cylindrical or tubular
bodies, solid plugs or cage designs, to mention a few. The present
invention is directed to an improved unitary cage and method for
its installation.
[0038] FIG. 2 shows the implant device of the invention, designated
generally as 15. In the preferred embodiment illustrated, the
unitary body 15 is a cage configured and sized to be inserted
between adjacent vertebrae in a single step implantation procedure.
As shown in FIGS. 2 and 4, the cage 15 is "banana-shaped" as view
from above. The body has an exterior surface 17 and an interior
surface 19. The interior surface 19 defines an internal recess or
enclosure for receiving cancellous bone material during an
implantation procedure. The preferred cage body, as best seen in
FIG. 2, is a ring having evenly spaced openings 21 about a
circumference of the body. The double bands from a serpentine
arrangement which comprises an interlinked mesh in the preferred
embodiment shown in FIG. 2.
[0039] A preferred material for the cage body 15 is a hard metal
alloy, preferably titanium or stainless steel. Other preferred
materials include carbon fiber, bioreabsorbable materials such as
polyglycotic acid, polylactic acid and other synthetic materials
such as polymethylmethacrylate PMMA blended with various antibiotic
admixtures fo the treatment of discitis and vertebral
osteomyelitis.
[0040] The cage body is selectively sized to fit within a vertebral
disc space of a human anatomy allowing adequate space for
additional cancellous bone anterior to the cage body within the
disc space. Referring to FIGS. 3 and 4, the cage 15 is typically
provided in a range of widths "w" of 24 mm, 26 mm and 28 mm. The
lengths "1" are typically 8 mm, 9 mm and 10 mm. The heights are 10
mm, 12 mm, 14 mm and 16 mm. The thickness of the titanium "t1" is
approximately 1.5 mm. The thickness of the mesh material "t2" is
approximately 2 mm. The radius of curvature "R1" of the front arc
of the cage is approximately 1.55 mm. The radius of curvature "R2"
of the posterior or back arc of the cage is approximately 1.5
mm.
[0041] The unitary cage 15 can be placed from an anterior position
(anterior interbody fusion or ALIF), or posteriorly (posterior
lumbar interbody fusion or PLIF, tranforaminal interbody fusion or
TLIF). The cage is curved so that it mirrors the natural radius or
curvature of the anterior and posterior curves of the vertebral
bodies. It can be placed from an anterior position or
posterolateral position after standard discectomy.
[0042] FIG. 5 shows a prior art pair of bone implants. In the
discussion which follows, the advantages of the unitary cage of the
invention will be apparent with respect to the prior art rings 23,
25. FIG. 6 shows the banana-shaped cage of the invention 15 within
the disc space, as view from above. Note that the cage 15 is curved
so that it mirrors the natural radius of curvature of the anterior
and posterior curves of the vertebral bodies. FIG. 7 is merely
intended to illustrate with placement of cancellous bone material
27, 29 both within the cage 15 and anterior thereto. FIG. 8
illustrates the proper placement of the prior art bone rings 23,
25, as viewed from above. FIG. 9 illustrates the possible
misalignment of the prior art rings 23, 25 due to the two component
nature of the procedure as well as the possibility of asymmetric
forces acting upon the rings. FIG. 10 is an illustration of the
cage prosthesis 15 of the invention inserted within the
intervertebral disc space 31. FIG. 11 is a side view of the disc
space 31 showing the proper placement of the cage of the
invention.
[0043] The steps in a standard discectomy will be familiar to those
skilled in the art. However, the steps will be briefly summarized
below with respect to FIGS. 12-17. In the case of a tranforminal
lumber interbody fusion and spondylosis thesis at L5 S1, the
patient's left and right side are first detached parallel to the
muscles in prone position. A wide exposure is carried out to the
tips of the transverse processes. Resection of the facet joints L5
S1 on both sides is then performed. The pedicle is opened, as by
means of an awl and the pedicle channel is probed. The pedicle is
then tapped and screws are inserted. FIGS. 12 and 13 shows the
screws 33, 35, 37 in place. The screws 33, 35, 37 in the L4, L5 and
S1 positions are aligned by means of a head adjuster so that the
screws are aligned in one plane. Rods 39, 41 are then placed (see
FIG. 12). The rods 39, 42, in the particular procedure illustrated
are fixed by means of inner screws 43 and outer nuts 45.
[0044] As illustrated schematically in FIG. 13, segmental
distraction is then applied between S1 and L5 while a simultaneous
posteriorly directed force at the cephalad end of the rod is
carried out. The same procedure s then performed on the opposite
side of the body. Resection and removal of the facet is the first
step to achieve access to disk L5 S1 via the transforminal
approach. This may be carried out with the use of a high speed bur
or a pituitary ronjour. The medial portion of the facet joint can
be resected by chisel and removed. Removal of the cephalad section
of the S1 facet is accomplished, allowing enough space for the
later placement of the implant prosthesis. Removal to the plane of
the S1 pedicle but not into the pedicle may be carried out. By
doing this, additional widening of the transforminal approach is
established. Removable of the disk itself may be accomplished by
means of straight and angled pituitary ronjours.
[0045] Proper resection of the postural lips of the L5 S1 implants
should be carried out. Additional spreading of the disk space is
achieved by use of a wedge shaped impactor and specifically
designed dilators. Further reduction of deformity is achieved by
means of segmental distraction forces on both sides.
[0046] Disc space preparation is next carried out with the use of
the cup curet with teeth (43 in FIG. 14) for cartilage removal and
preservation of the implants. Further removal of any disk fragments
is also carried out in this step of the procedure. Spongiosa and
any additional morcilized graft can now be inserted to the anterior
longitudinal ligament and anterior third of the disk space L5 S1.
The spongiosa is condensed by the use of specially designed
impactors.
[0047] The properly sized cage implant of the invention can now be
selected as determined by the height of the disk space after
reduction. FIG. 15 illustrated the insertion of the banana-shaped
cage 15 of the invention within the disc space 31, the cancellous
bone material 29 also being visible. FIG. 16 shows the placement of
additional cancellous bone material in the region surrounding the
cage implant 15.
[0048] The nuts at L5 are now untightened. The conversion of the
previously applied distractive forces are converted to compression
forces by means of a compressor (45 in FIG. 17). This procedure is
repeated alternatively on both sides. A final tightening sequence
is then performed on the screws for rod-stabilization and
maintenance of the desired correction. Additional application of
bone for posterior lateral fusion may be accomplished as shown with
respect to FIG. 16. The conversion of distraction forces to
compression forces after positioning of the implant 15 allows
restoration of both the tension band principle and load-sharing
principle within the fused segment.
[0049] FIG. 18 is an additional view of the insertion of the cage
15 of the invention within the disc space showing the curved nature
of the disc space. FIGS. 19 and 20 are side and back views,
respectively, of the properly placed cage.
[0050] An invention has been provided with several advantages. The
unitary banana-shaped cage of the invention is easier and safer to
place within the prepared disc space and is mechanically more
stable than the previous two component systems currently in use.
The curvature of the cage of the invention mirrors the natural
curvature of the anterior and posterior curves of the vertebral
bodies. It can be placed from either the anterior position or
posterolateral position after standard discectomy. The implant of
the invention can be manufactured from a variety of materials
including both metals, metal alloys and synthetic, bioreabsorbable
materials.
[0051] While the invention has been shown in only one of its forms,
it is not thus limited but is susceptible to various changes and
modifications without departing from the spirit thereof.
[0052] While this invention has been particularly shown and
described with references to preferred embodiments thereof, it will
be understood by those skilled in the art that various changes in
form and details may be made therein without departing from the
scope of the invention encompassed by the appended claims.
* * * * *