U.S. patent application number 11/745293 was filed with the patent office on 2007-09-06 for intervertebral implant for transforminal posterior lumbar interbody fusion procedure.
Invention is credited to David Gerber, Kenneth Isamu Kobayashi, Dominique Messerli, David Paul.
Application Number | 20070208423 11/745293 |
Document ID | / |
Family ID | 32312158 |
Filed Date | 2007-09-06 |
United States Patent
Application |
20070208423 |
Kind Code |
A1 |
Messerli; Dominique ; et
al. |
September 6, 2007 |
Intervertebral Implant for Transforminal Posterior Lumbar Interbody
Fusion Procedure
Abstract
An intervertebral implant for fusing vertebrae is disclosed. The
implant may have a body with curved, posterior and anterior faces
separated by two narrow implant ends, superior and inferior faces
having a plurality of undulating surfaces for contacting vertebral
endplates, and at least one depression in the anterior or posterior
face for engagement by an insertion tool. The implant may also have
one or more vertical through-channels extending through the implant
from the superior face to the inferior face, a chamfer on the
superior and inferior surfaces at one of the narrow implant ends,
and/or a beveled edge along a perimeter of the superior and
inferior faces. The implant configuration facilitates
transforaminal insertion of the implant into a symmetric position
about the midline of the spine so that a single implant provides
balanced support to the spinal column. The implant may be formed of
a plurality of interconnecting bodies assembled to form a single
unit. An implantation kit and method are also disclosed.
Inventors: |
Messerli; Dominique; (West
Chester, PA) ; Gerber; David; (Exton, PA) ;
Paul; David; (Phoenixville, PA) ; Kobayashi; Kenneth
Isamu; (Exton, PA) |
Correspondence
Address: |
STROOCK & STROOCK & LAVAN, LLP
180 MAIDEN LANE
NEW YORK
NY
10038
US
|
Family ID: |
32312158 |
Appl. No.: |
11/745293 |
Filed: |
May 7, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11301759 |
Dec 12, 2005 |
7223292 |
|
|
11745293 |
May 7, 2007 |
|
|
|
10293997 |
Nov 13, 2002 |
6974480 |
|
|
11301759 |
Dec 12, 2005 |
|
|
|
09848178 |
May 3, 2001 |
6719794 |
|
|
10293997 |
Nov 13, 2002 |
|
|
|
Current U.S.
Class: |
623/17.11 |
Current CPC
Class: |
A61F 2/4465 20130101;
A61F 2220/0025 20130101; A61F 2002/30904 20130101; A61F 2002/30594
20130101; A61F 2/4684 20130101; A61F 2002/30383 20130101; A61F
2002/30604 20130101; A61F 2002/30492 20130101; A61F 2/446 20130101;
A61F 2002/30797 20130101; A61F 2250/0098 20130101; A61F 2250/0063
20130101; A61F 2002/30593 20130101; A61F 2002/30599 20130101; A61F
2310/00359 20130101; A61F 2002/4628 20130101; A61F 2002/30975
20130101; A61F 2002/30785 20130101; A61F 2002/2835 20130101; A61B
17/1671 20130101; A61F 2/4611 20130101; A61F 2310/00017 20130101;
A61B 17/1659 20130101; A61F 2230/0015 20130101; A61B 17/1604
20130101; A61F 2002/3008 20130101; A61F 2250/0006 20130101; A61F
2002/30133 20130101; A61F 2002/30787 20130101; A61F 2/28 20130101;
A61F 2002/30538 20130101; A61F 2002/30507 20130101; A61F 2002/30843
20130101 |
Class at
Publication: |
623/017.11 |
International
Class: |
A61F 2/44 20060101
A61F002/44 |
Claims
1. An intervertebral implant sized and configured for implantation
between a first and second vertebra via transforaminal lumbar
interbody fusion technique, the implant comprising: a body
substantially made of allograft, the body including a curved
posterior face, a curved anterior face, both curved posterior and
anterior faces extending along a longitudinal axis of the implant;
a pair of narrow ends separating the posterior and anterior faces
and superior and inferior surfaces for contacting at least a
portion of the first and second vertebral, the superior and
inferior surfaces include a plurality of teeth formed; and at least
one non-threaded, horizontal channel configured and adapted for
engagement by an implant insertion tool, the channel disposed along
at least a portion of the curved posterior face or disposed along
at least a portion of the curved anterior face.
2. The implant of claim 1, further comprising at least one vertical
through-channel extending from said superior surface to said
inferior surface.
3. The implant of claim 1, wherein at least one of the superior and
inferior surfaces includes a chamfer formed thereon.
4. The implant of claim 3, wherein the chamfer is devoid of any
teeth formed thereon.
5. The implant of claim 3, wherein the implant includes a pair of
non-threaded, horizontal channels, one of said non-threaded,
horizontal channel being formed on the curved posterior face, the
other of said non-threaded, horizontal channel being formed on the
curved anterior face, the pair of non-threaded, horizontal channels
extending from one of the arcuate ends.
6. The implant of claim 5, wherein the chamfer is formed on the
other of said arcuate ends.
7. The implant of claim 1, wherein the curved anterior and curved
posterior faces are substantially parallel.
8. The implant of claim 6, wherein the curved posterior face has a
radii of curvature R1 and the curved anterior face has a radii of
curvature R2, wherein R1 is between about 25 mm and 35 mm and R2 is
between about 15 mm and 25 mm.
9. The implant of claim 1, wherein the teeth have a pyramid shape
such that each tooth has four sides and forms an acute angle with
the superior or inferior faces.
10. The implant of claim 1, wherein a distance between the superior
and inferior surfaces define an implant height, the implant height
being greatest at a midsection between the pair of narrow ends, the
implant height tapering gradually along the longitudinal axis of
the implant so that the implant height is thinnest at the narrow
ends of the implant.
11. The implant of claim 10, wherein the tapering thickness is
defined by a radius of curvature R3, wherein R3 is between about 85
mm and 115 mm.
12. The implant of claim 10, wherein the implant height is
substantially constant for any given cross section taken
perpendicular to the longitudinal axis of the implant
13. The implant of claim 1, wherein the implant is formed of at
least two pieces of allograft assembled together to form the
implant.
14. The implant of claim 13, wherein the at least two pieces of
allograft are joined together by interlocking grooves and
pallets.
15. The implant of claim 13, wherein the at least two pieces of
allograft containing an opening formed therein, the opening being
sized and configured to receive at least one pin for holding the
pieces of allograft together as a single unit.
16. An intervertebral implant sized and configured for implantation
between a first and second vertebra via transforaminal lumbar
interbody fusion technique, the implant comprising: a body having a
curved posterior face, a curved anterior face, a pair of curved
ends separating the posterior and anterior faces and superior and
inferior faces for contacting at least a portion of the first and
second vertebra, the superior and inferior faces defining a
thickness of the implant; wherein the body includes at least one
vertical through-channel extending from the superior face to the
inferior face; and the anterior and posterior faces include at
least two non-threaded, horizontal channels configured and adapted
for engagement by an implant insertion tool, one of the channels
being disposed along at least a portion of the curved posterior
face, the other of said channels being disposed along at least a
portion of the curved anterior face, wherein the channels each
include at least two recesses for engaging a corresponding
projection formed on the insertion tool.
17. The implant of claim 16, wherein the at least one vertical
through-channel defines a first wall between the anterior face and
the vertical through-channel and a second wall between the
posterior face and the vertical through channel, the first and
second walls having a wall width, the vertical through channel
having a channel width, the wall width being greater than the
channel width.
18. The implant of claim 16, wherein the implant includes at least
two vertical through-channels extending from said superior surface
to said anterior surface.
19. The implant of claim 16, wherein the implant further includes
at least one horizontal through-channel extending through the
implant from the anterior face to the posterior face.
20. The implant of claim 16, wherein the implant further includes
at least one lateral through-channel extending from at least one of
the curved ends towards the vertical through channel.
21. The implant of claim 20, wherein the lateral through channel
extends from one curved end completely through the implant to the
other curved end.
22. The implant of claim 16, wherein the implant is formed from a
radiolucent material.
23. The implant of claim 20, wherein the implant includes at least
one radiopaque marker
24. The implant of claim 16, wherein the implant is formed from a
titanium alloy.
25. The implant of claim 16 wherein at least one of the superior
and inferior surfaces includes a chamfer formed thereon.
26. The implant of claim 25, wherein the chamfer is devoid of any
teeth formed thereon.
27. The implant of claim 16, wherein the implant further includes a
beveled edge along a perimeter of the superior and inferior
surfaces.
28. An intervertebral implant for posterior insertion via a
transforaminal window comprising: curved, substantially parallel
posterior and anterior faces, the posterior and anterior faces
extending along a longitudinal axis of the implant; a pair of
convex narrow ends separating the posterior and anterior faces;
superior and inferior faces for contacting upper and lower
vertebral endplates, the superior and inferior faces defining a
thickness of the implant; at least one depression in the anterior
or posterior face for engagement by an insertion tool; and at least
two vertical through-channels extending through the implant from
the superior face to the inferior face, each vertical
through-channel having a width and walls on posterior and anterior
sides of the width, the walls on the posterior and anterior sides
of the width of the vertical through-channels having a thickness
greater than the width of the vertical through channels;
29. The implant of claim 28, further comprising a chamfer on the
superior and inferior faces at one of the convex narrow ends to
facilitate implant insertion.
30. The implant of claim 28, wherein the depression further
comprises multiple recesses for engagement with an insertion
tool.
31. The implant of claim 28, wherein the implant further includes
at least one horizontal through-channel extending through the
implant from the anterior face to the posterior face.
32. The implant of claim 28, wherein the implant further includes
at least one lateral through-channel extending from at least one of
the curved ends towards the vertical through channel.
33. The implant of claim 32, wherein the lateral through channel
extends from one curved end completely through the implant to the
other curved end.
34. The implant of claim 28, wherein the implant is formed from a
radiolucent material.
35. The implant of claim 34, wherein the implant includes at least
one radiopaque marker.
36. The implant of claim 28, wherein the implant is formed from a
titanium alloy.
37. An intervertebral implant sized and configured for implantation
between a first and second vertebra via transforaminal lumbar
interbody fusion technique, the implant comprising: curved
posterior and anterior faces, the posterior and anterior faces
extending along a longitudinal axis of the implant; a pair of
arcuate ends separating the posterior and anterior faces; superior
and inferior surfaces for contacting at least a portion of the
first and second vertebral, the superior and inferior faces
defining a thickness of the implant; at least one vertical
through-channel extending from the superior surface to the inferior
surface, the at least one vertical through-channel defining a first
wall between the anterior face and the vertical through-channel and
a second wall between the posterior face and the vertical through
channel, the first and second walls having a wall width, the
vertical through channel having a channel width, the wall width
being greater than the channel width.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 11/301,759, filed Dec. 12, 2005, which is a
continuation of U.S. patent application Ser. No. 10/293,997, filed
Nov. 13, 2002, now U.S. Pat. No. 6,974,480, which is a
continuation-in-part of U.S. patent application Ser. No.
09/848,178, filed May 3, 2001, now U.S. Pat. No. 6,719,794.
FIELD OF THE INVENTION
[0002] The present invention is directed to an intervertebral
implant, its accompanying instrumentation and their method of use.
More particularly, the present invention is directed to an
intervertebral implant and instrumentation for use in a
transforaminal posterior lumbar interbody fusion procedure.
BACKGROUND OF THE INVENTION
[0003] A number of medical conditions such as compression of spinal
cord nerve roots, degenerative disc disease, herniated nucleus
pulposus, spinal stenosis and spondylolisthesis can cause severe
low back pain. Intervertebral fusion is a surgical method of
alleviating low back pain. In posterior lumbar interbody fusion
("PLIF"), two adjacent vertebral bodies are fused together by
removing the affected disc and inserting posteriorly one or more
implants that would allow for bone to grow between the two
vertebral bodies to bridge the gap left by the removed disc.
[0004] One variation of the traditional PLIF technique is the
transforaminal posterior lumbar interbody fusion (T-PLIF)
technique. Pursuant to this procedure, an implant is inserted into
the affected disc space via a unilateral (or sometimes bilateral),
posterior approach, offset from the midline of the spine, by
removing portions of the facet joint of the vertebrae. The T-PLIF
approach avoids damage to nerve structures such as the dura, cauda
equina and the nerve root, but the resulting transforaminal window
available to remove the affected disc, prepare the vertebral
endplates, and insert the implant is limited laterally by soft
tissue and medially by the cauda equina.
[0005] A number of different implants typically used for the
traditional PLIF procedure have been used for the T-PLIF procedure
with varying success. These include threaded titanium or polymer
cages, allograft wedges, rings, etc. However, as these devices were
not designed specifically for the T-PLIF procedure, they are not
shaped to be easily insertable into the affected disc space through
the narrow transforaminal window, and may require additional
retraction of the cauda equina and nerve roots. Such retraction can
cause temporary or permanent nerve damage. In addition, some of
these implants, such as the threaded titanium or polymer cage,
suffer from the disadvantage of requiring drilling and tapping of
the vertebral endplates for insertion. Further, the incidence of
subsidence in long term use is not known for such cages. Finally,
restoration of lordosis, i.e., the natural curvature of the lumbar
spine is very difficult when a cylindrical or square titanium or
polymer cage is used.
[0006] As the discussion above illustrates, there is a need for an
improved implant and instrumentation for fusing vertebrae via the
transforaminal lumbar interbody fusion procedure.
SUMMARY OF THE INVENTION
[0007] The present invention relates to an intervertebral implant
("T-PLIF implant") and its use during a transforaminal lumbar
interbody fusion procedure. In a preferred embodiment, the T-PLIF
implant has an arcuate body with curved, preferably substantially
parallel, posterior and anterior faces separated by two narrow
implant ends, and superior and inferior faces having textured
surfaces for contacting upper and lower vertebral endplates.
Preferably, the textured surfaces comprise undulating structures
which may include projections, such as teeth, of a saw-tooth or
pyramidal configuration, or ridges which preferably penetrate the
vertebral endplates and prevent slippage. The narrow implant ends
may be rounded or substantially flat. The arcuate implant
configuration facilitates insertion of the implant via a
transforaminal window. The implant, which may be formed of
allogenic bone, metal, or plastic, may also have at least one
depression, such as a channel or groove, in the posterior or
anterior face for engagement by an insertion tool, such as an
implant holder. In a preferred aspect, the superior and inferior
faces are convex, and the thickness of the implant tapers with its
greatest thickness in the middle region between the narrow ends of
the implant, i.e., at a section parallel to a sagittal plane, and
decreasing toward each of the narrow ends.
[0008] In another embodiment, the T-PLIF implant preferably has
curved, substantially parallel posterior and anterior faces
extending along a longitudinal axis of the implant, a pair of
convex narrow ends separating the posterior and anterior faces, a
chamfer on the superior and inferior faces at one of the convex
narrow ends, a beveled edge along a perimeter of the superior and
inferior faces, and at least one depression in the anterior or
posterior face for engagement by an insertion tool, where the
superior and inferior faces contact upper and lower vertebral
endplates and define a thickness of the implant. The T-PLIF implant
preferably has at least two vertical through-channels extending
through the implant from the superior face to the inferior face,
each vertical through-channel having a width and walls on posterior
and anterior sides of the width. The arcuate implant configuration
and the chamfer on the inferior and superior faces at the narrow
insertion end of the implant facilitate insertion of the implant
via the transforaminal window. In a preferred aspect, the implant
also has at least two anterior-posterior horizontal
through-channels extending through the implant from the posterior
face to the anterior face. The implant may also feature at least
one lateral horizontal through-channel extending from a narrow end
of the implant inward toward an adjacent anterior-posterior
horizontal through-channel. Each of the channels may be packed with
bone-graft and/or bone growth inducing material to aid in spinal
fusion. In one exemplary embodiment, the walls on the posterior and
anterior sides of the width of the vertical through-channels have a
thickness greater than the width of the vertical through channels.
The implant may be formed of a radiolucent polymer material
selected from the polyaryl ether ketone family (PAEK), such as
polyether ether ketone (PEEK) or polyether ketone (PEKK), or other
suitable biocompatible material of sufficient strength, such as
titanium. The implant may include one or more radiopaque marker,
such as pins or screws, extending substantially through the
thickness of the implant to indicate implant location and size in
postoperative spinal scans.
[0009] In another preferred embodiment, the implant is formed of a
plurality of interconnecting bodies assembled to form a single
unit. In this configuration, the plurality of interconnecting
bodies forming the T-PLIF implant may be press-fit together and may
include one or more pin(s) or screw(s) extending through an opening
in the plurality of bodies to hold the bodies together as a single
unit. Adjacent surfaces of the plurality of bodies may also have
mating interlocking surfaces that aid in holding the bodies
together as a single unit.
[0010] In still another preferred embodiment, the present invention
relates to a kit for implanting an intervertebral implant into an
affected disc space of a patient via a transforaminal window. The
kit includes an implant having an arcuate body with curved,
preferably substantially parallel, posterior and anterior faces
separated by two narrower implant ends, superior and inferior faces
preferably having a textured surface, such as projections or teeth,
for contacting and preferably penetrating upper and lower vertebral
endplates. The superior and inferior faces may define a thickness.
Preferably the implant has at least one depression in its posterior
or anterior face near one of its ends for engagement by an
insertion tool. The implant may also have two or more vertical
through-channels extending through the implant from the superior
face to the inferior face, each vertical through-channel having a
width and walls on posterior and anterior sides of the width, a
chamfer on the superior and inferior surfaces at an insertion end
and a beveled edge along a perimeter of the superior and inferior
faces. The kit may further include one or more trial-fit spacer(s)
for determining the appropriate size of the implant needed to fill
the affected disc space, an insertion tool having an angled or
curved neck for holding and properly positioning the implant during
insertion through the transforaminal window, and an impactor having
an angled or curved neck for properly positioning the implant
within the affected disc space. The face of the impactor may be
concavely shaped to mate with the narrow end of the T-PLIF implant
during impaction. The kit may further include a lamina spreader for
distracting vertebrae adjacent to the affected disc space, an
osteotome for removing facets of the vertebrae adjacent to the
affected disc space to create a transforaminal window, one or more
curettes, angled and/or straight, for removing disc material from
the affected disc space, a bone rasp for preparing endplates of the
vertebrae adjacent the affected disc space, and a graft implant
tool for implanting bone graft material into the affected disc
space. The kit may still further include a curved guide tool to
guide the implant into the affected disc space. In another
preferred embodiment, the implant of the kit includes two or more
anterior-posterior horizontal through-channels extending through
the implant from the posterior face to the anterior face, wherein a
portion of the walls on the posterior and anterior sides of the
width of the vertical through-channels of the implant may have a
thickness greater than the width of the vertical through channels.
The implant of the kit may also include one or more lateral
horizontal through-channel(s) extending from a narrow end of the
implant inward toward an adjacent anterior-posterior horizontal
through-channel. Each of the channels may be packed with bone-graft
and/or bone growth inducing material prior to and/or after
insertion to aid in spinal fusion. The implant may also include one
or more radiopaque markers, such as pins, that extend substantially
through the thickness of the implant.
[0011] In yet another aspect, a method for implanting an
intervertebral implant into an affected disc space of a patient via
a transforaminal window is described. The transforaminal window is
created, the disc space is prepared and bone graft material may be
inserted into the affected disc space. Using an insertion tool, an
implant is inserted into the affected disc space via the
transforaminal window and seated in a portion of the disc space
closer to the anterior edge of the disc space than the posterior
edge of the disc space. As discussed above, the implant preferably
has an arcuate body with curved, substantially parallel posterior
and anterior faces separated by two narrow implant ends, superior
and inferior faces having a plurality of undulating surfaces for
contacting upper and lower vertebral endplates, and preferably at
least one depression at a first end for engagement by the insertion
tool. In the present method, the arcuate implant configuration
facilitates insertion of the implant via the transforaminal window.
The implant may be inserted along an arcuate path. The method may
further comprise impacting the implant with an impactor tool to
properly position the implant within the affected disc space.
Either or both the insertion tool and the impactor tool may be
angled to facilitate insertion, alignment, placement and/or proper
seating of the implant. The implant may also feature two or more
vertical through-channel(s) extending through the implant from the
superior face to the inferior face, each vertical through-channel
having a width and walls on posterior and anterior sides of the
width, a chamfer on the superior and inferior faces at the
insertion end, and a beveled edge along a perimeter of the superior
and inferior faces. The implant may also have two or more
anterior-posterior horizontal through-channel(s) extending through
the implant from the posterior face to the anterior face and/or at
least one lateral horizontal through-channel extending from a
narrow end of the implant inward toward an adjacent
anterior-posterior horizontal through-channel. Each of the channels
may be packed with bone-graft and/or bone growth inducing material
before implantation and/or after implantation to aid in spinal
fusion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a top view of a typical human vertebrae showing
the transforaminal window through which an implant according to the
present invention is inserted;
[0013] FIG. 2A is a cross-section view of an embodiment of an
implant according to the present invention;
[0014] FIG. 2B is a side view along the longer axis of the implant
of FIG. 2A;
[0015] FIG. 2C is a cross-section view taken along line 2C-2C of
FIG. 2B;
[0016] FIG. 2D is a perspective view of the implant of FIG. 2A;
[0017] FIG. 3A is a partial cross-section view of another
embodiment of an implant according to the present invention;
[0018] FIG. 3B is a partial cross-section view along the longer
axis of the implant of FIG. 3A;
[0019] FIG. 3C is a cross-section view taken along line 3C-3C of
FIG. 3B;
[0020] FIG. 3D is a perspective view of the implant of FIG. 3A;
[0021] FIG. 4 is a perspective view of still another embodiment of
the implant of the present invention;
[0022] FIG. 5 is an axial view of a typical human vertebrae showing
the implant of FIG. 4 in an asymmetric final position.
[0023] FIG. 6 is a posterior view of a section of human spine prior
to preparation of the transforaminal window;
[0024] FIG. 7 is a posterior view of a section of human spine with
the transforaminal window prepared;
[0025] FIG. 8A depicts an angled bone curette for use during the
T-PLIF procedure;
[0026] FIG. 8B depicts another angled bone curette for use during
the T-PLIF procedure;
[0027] FIG. 8C depicts an angled bone curette removing disc
material from an affected disc space;
[0028] FIG. 9A depicts an angled bone rasp for use during a T-PLIF
procedure;
[0029] FIG. 9B depicts an angled bone rasp removing material from
an affected disc space;
[0030] FIG. 10A depicts a trial-fit spacer for use during a T-PLIF
procedure;
[0031] FIG. 10B depicts a trial-fit spacer being inserted into an
affected disc space via a transforaminal window;
[0032] FIG. 11A depicts an implant holder for use during a T-PLIF
procedure;
[0033] FIG. 11B depicts the tips of the implant holder shown in
FIG. 11A;
[0034] FIG. 11C depicts an posterior view of the human spine
showing a T-PLIF implant being inserted with an implant holder;
[0035] FIG. 11D depicts a top view of a human vertebrae showing a
T-PLIF implant being inserted with in an implant holder;
[0036] FIG. 12 depicts an implant guide tool for use with the
T-PLIF implant;
[0037] FIG. 13A depicts an angled impactor tool for use with the
T-PLIF implant;
[0038] FIG. 13B is a close-up view of the tip of the impactor tool
shown in FIG. 13A;
[0039] FIG. 14 is a top view of a typical human vertebrae showing
an implant according to the present invention being properly
positioned into an affected disc space using the impactor tool
shown in FIG. 13A;
[0040] FIG. 15 is a top view of the vertebrae of FIG. 1 showing the
T-PLIF implant in a final position; and
[0041] FIG. 16A is a partial cross-section side view along the
longer axis of still another embodiment of an implant according to
the present invention;
[0042] FIG. 16B is a partial cross-section side view along the
shorter axis of the implant of FIG. 16A;
[0043] FIG. 16C is a partial cross-section top view of the implant
of FIG. 16A;
[0044] FIG. 16D is a perspective view of the implant in FIG.
16A;
[0045] FIG. 16E is a partial side view of the implant taken along
line 16E-16E in FIG. 16C;
[0046] FIG. 17A is a partial cross-section side view along the
longer axis of still another embodiment of an implant according to
the present invention;
[0047] FIG. 17B is a partial cross-section side view along the
shorter axis of the implant of FIG. 17A;
[0048] FIG. 17C is a partial cross-section top view of the implant
of FIG. 17A; and
[0049] FIG. 17D is a perspective view of the implant in FIG.
17A;
[0050] FIG. 17E is a partial side view of the implant taken along
line 17E-17E in FIG. 17C; and
[0051] FIG. 18 is a side view of another preferred embodiment of
the implant of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0052] While various descriptions of the present invention are
provided below, it should be understood that these descriptions are
intended to illustrate the principals of the present invention and
its various features, which can be used singly or in any
combination thereof. Therefore, this invention is not to be limited
to only the specifically preferred embodiments described and
depicted herein.
[0053] The transforaminal posterior lumbar interbody fusion implant
("T-PLIF implant") is designed for use as an intervertebral spacer
in spinal fusion surgery where an affected disk is removed from
between two adjacent vertebrae and replaced with an implant that
provides segmental stability and allows for bone to grow between
the two vertebrae to bridge the gap created by disk removal.
Specifically, the T-PLIF implant is designed for the transforaminal
lumbar interbody fusion (T-PLIF) technique, which, as shown in FIG.
1, involves a posterior approach 12, offset from the midline 14 of
the spine, to the affected intervertebral disk space 16. The window
18 available for implant insertion using the T-PLIF technique is
limited medially by the dura or cauda equina 20 and the superior
exiting nerve root (not shown).
[0054] As shown in FIGS. 2A through 2D, in a preferred embodiment,
the T-PLIF implant has an arcuate, "rocker-like" body 22 with
curved anterior and posterior faces 24, 26 to facilitate the offset
insertion of the implant through the narrow approach window 18 into
the disk space. Preferably, the anterior and posterior faces 24 and
26 are substantially parallel, separated by a pair of narrow ends
25. Narrow ends 25 may be rounded or blunt. The superior and
inferior surfaces 28, 30 preferably have projections, such as teeth
32, for engaging the adjacent vertebrae. Teeth 32 on superior and
inferior surfaces 28, 30 preferably provide a mechanical interlock
between implant 22 and the end plates by penetrating the end
plates. The initial mechanical stability afforded by teeth 32
minimizes the risk of post-operative expulsion/slippage of implant
22. Teeth 32 may have a saw-tooth shape, where one side of the
tooth is perpendicular to the superior or inferior surface, or a
pyramid shape, where each tooth has four sides and forms an acute
angle with the superior or inferior face. Preferably, implant body
22 has at least one channel or slot 34 on one end of implant 22 for
engagement by a surgical instrument, such as an implant holder 66
(shown in FIG. 11A). It should be noted that implant 22 may also be
configured with a channel 34 on only one side or without channels
altogether. Other known methods for engaging the implant with
surgical instruments, such as a threaded bore for receiving the
threaded end of a surgical tool or a non-threaded bore for
receiving an expandable head of an insertion tool, may also be
used.
[0055] As shown in FIG. 2B, thickness 31 of implant 22 is greatest
at the mid-section between the two narrow implant ends 25 and
tapers gradually along the longitudinal axis 36 of implant 22 so
that it is thinnest at the narrow ends 25 of implant 22. The taper
is preferably arcuate and provides a convex configuration and a
proper anatomical fit, while also facilitating insertion of implant
22 into the affected disc space. It should be noted that in a
preferred embodiment, thickness 31 does not taper or change along
the shorter axis 37 of implant 22. Thus for any given cross section
taken perpendicular to the longitudinal axis 36 of the implant, the
distance between the superior and inferior surfaces 28 and 30
remains substantially constant. In alternate embodiments, however,
thickness 31 may change or taper along shorter axis 37 of implant
22. The dimensions of implant 22 can be varied to accommodate a
patient's anatomy, and the thickness of the implant is chosen based
on the size of the disk space to be filled. Preferably, implant 22
has a maximum thickness 31 at its mid-section of about 7.0 to about
17.0 mm, and may be formed of metal, allograft, a metal-allograft
composite, a carbon-fiber polymer, pure polymer or plastic or
combinations of these materials. The implant may also be formed of
a resorbable polymer. The thickness at the narrow ends 25 of
implant 22 may range from about 1.5 to about 2.0 mm less than the
maximum thickness at the mid-section. The implant may range from
about 26 to about 32 mm in length, and have a width from about 9 to
11 mm. Implant 22, which as shown most clearly in FIG. 2A is
symmetric about at least one axis of rotation 37, is intended for
symmetric placement about the midline 14 of the spine (see FIG.
19). The arcuate configuration of implant 22 facilitates insertion
of the implant from the transforaminal approach into a symmetric
position about the midline of the spine so that a single implant
provides balanced support to the spinal column.
[0056] As shown in FIGS. 3A-3D, in an alternate embodiment implant
22 may be formed of two or more pieces 38 preferably having
interlocking grooves 39 and pallets 40 that may be press-fit and
fastened together with pins or screws 42. The number and
orientation of pins or screws 42 can be varied. In addition or
alternatively, the pieces may be fastened using glue, cement or a
welding or bonding process. This multi-component configuration may
be particularly useful for implants formed of allograft bone, since
it may be difficult and/or impractical to obtain a single,
sufficiently large piece of allograft for some applications. In the
case of implants formed completely of artificial (i.e.,
non-allograft) materials, such as steel, plastic or metallic or
non-metallic polymer, a one-piece implant may be more practical. As
shown in FIG. 3C, in a preferred embodiment for any given
cross-section taken perpendicular to the longitudinal axis of the
implant, the distance between the superior and inferior surfaces 28
and 30 remains substantially constant.
[0057] As in the previous embodiment, the anterior and posterior
faces 24, 26 are preferably substantially parallel, and, as shown,
may be defined by radii of curvature R1 and R2, where R1, for
example, may be in the range of 25-35 mm and preferably about 28 mm
and R2, for example, may be in the range of 15 to 25 mm and
preferably about 19 mm. The superior and inferior surfaces 28, 30
are arcuate shaped and the implant has a thickness 31, which is
preferably greatest at a center portion between narrow ends 25 and
gradually tapers becoming thinnest at narrow ends 25. Tapering
thickness 31 may be defined by a radius of curvature R3, where R3
for example, may be in the range of 85 to 115 mm and preferably
about 100 mm. As shown, the component pieces 46, 48 of implant 22
have holes 44 to accommodate pins or screws 42. Holes 44 are
preferably drilled after component pieces 38 have been stacked one
on top of the other. The multiple pieces 38 are then assembled with
screws or pins 42 so that practitioners receive the implant 22 as a
single, pre-fabricated unit. The upper component piece 46 has an
arcuate superior surface preferably with teeth 32, while its bottom
surface is preferably configured with grooves and pallets
preferably to interlock with the upper surface of lower component
piece 48. The arcuate inferior surface 30 of lower component piece
48 also preferably has teeth 32 for engaging the lower vertebral
endplate of the affected disc space. Either or both superior and
inferior surfaces 28, 30 may have ridges, texturing or some other
form of engaging projection in place of teeth 32.
[0058] Reference is now made to FIGS. 16A-16E, which display still
another preferred embodiment of the implant of the present
invention. Similar in profile to the embodiments shown in FIGS. 2A
and 3A, the anterior and posterior faces 24, 26 are substantially
parallel, and, as shown, may be defined by radii of curvature R1
and R2, where R1, for example, may be in the range of 25 to 35 mm
and preferably about 29 mm and R2, for example, may be in the range
of 15 to 25 mm and preferably about 19 mm. The superior and
inferior surfaces 28, 30 are arcuate shaped and the implant has a
thickness 31, which is preferably greatest at a center portion
between narrow ends 25 and gradually tapers becoming thinnest at
narrow ends 25. Tapering thickness 31 may be defined by a radius of
curvature R3, where R3 for example, may be in the range of 85 to
115 mm and preferably about 100 mm. Superior and inferior surfaces
28, 30 preferably have a textured surface which may include a
plurality of undulating surfaces, such as, for example, teeth 32,
for engaging the upper and lower vertebral endplates of the
affected disc space. (Note: For sake of clarity, teeth 32 are not
pictured in FIGS. 16C-16E, 17C-17E or on the inferior face of the
implant shown in FIGS. 16B & 17B.)
[0059] As shown, the implant has depressions or slots 34 on both
its anterior and posterior face that mate with an insertion tool 66
(shown in FIGS. 11A & 11B). As shown in FIGS. 11B, 16C and 17C,
projections 69 on the tips 67 of insertion tool 66 mate with
scalloped depressions 81 within slots 34 to securely hold the
implant during insertion. The implant has a pair of vertical
through-channels 74 extending through the implant from the superior
surface 28 to the inferior surface 30, which may be packed with
bone graft and other bone growth inducing material prior to and/or
after implantation to aid in spinal fusion. Preferably, the implant
also has a chamfer 75 on both its superior and inferior surfaces
28, 30 at insertion end 79. As shown best in FIGS. 16D and 16E,
chamfers 75 form a wedge-like shape at insertion end 79 to
facilitate implant insertion through the transforaminal window.
Chamfers 75 begin at a section of the implant at an angle .beta.
from the midline of the implant, where .beta. may be in the range
of 15.degree. to 30.degree. and preferably about 23.degree., and
taper to the end of narrow insertion end 79. As shown in FIG. 16E,
chamfers 75 form an angle .gamma. with the vertical wall of narrow
insertion end 79, where .gamma. may be in the range of 50.degree.
to 80.degree. and preferably about 60.degree..
[0060] Preferably, implant 22 also includes a beveled edge 76 along
the perimeter of its superior and inferior surfaces 28, 30 As shown
in FIG. 16B, beveled edge 76 may be beveled at an angle .alpha. to
the vertical axis, which may be in the range of 25.degree. to
45.degree. and preferably about 37.degree.. Beveled edge 76 is free
from teeth 32 and both facilitates implant insertion and handling
of the implant by physicians. Since edges 76 are free from teeth
32, the perimeter edges of the implant are unlikely to become
snagged by tissue during implant insertion and a surgeon is less
likely to tear protective gloves while handling the implant prior
to and during insertion.
[0061] As shown in FIG. 16C, in a preferred embodiment, the
thickness of the walls T1 on the anterior and posterior sides of
vertical through-channels 74 is greater than the width W1 of
vertical through-channel 74. For example, for an implant with walls
of equal thickness, T1 may be in the range of 3.4 to 4.0 mm and
preferably about 3.5 mm and W1 may be on the order of 3.2 to 2.0
mm. The total implant width may be in the range of 9 to 11 mm, and
preferably about 10 mm. It should be emphasized that the implant
shown in FIGS. 16A-16C has walls 82 of equal thickness T1 on either
side of channel 74, but in other embodiments walls 82 may have
different thicknesses. Channels 74 may have an arcuate shape or any
other suitable shape, e.g., rectangular, circular, etc. The implant
may be formed of a radiolucent material selected from the polyaryl
ether ketone family (PAEK), such as polyether ether ketone (PEEK)
or polyether ketone (PEKK), and may include radiopaque markers,
such as pins 77, that act as radiographic markers to aid in
positioning and monitoring the position of the implant. Preferably,
radiopaque pins 77 extend substantially through the height of the
implant so that postoperative spinal scans indicate the size of the
implant used in a given patient. For example, a radiolucent implant
with a 7.0 mm height includes radiopaque pins on the order of 6.0
mm in length, while a 17.0 mm implant has pins on the order of 16.0
mm in length. Pins 77 thus enable a physician to better evaluate a
postoperative patient and monitor the position of the implant. Pins
77 may also function as fasteners for implants formed of two or
more pieces. The implant may also be formed of a suitable
biocompatible material such as titanium. As shown in FIG. 18, the
implant may be formed of a stack of units to create an implant with
a varying heights H1 ranging from about 7.0 mm to about 88.0
mm.
[0062] In still another embodiment shown in FIGS. 17A-17E, in
addition to vertical through-channels 74, the implant has two
horizontal through-channels 78 extending through the implant from
anterior face 24 to posterior face 26. Channels 78 may have a width
W2 in the range of 2.5 to 7.5 mm and preferably about 5.0 mm, and a
radius of curvature R4 in the range of 1.0 to 2.0 mm and preferably
about 1.2 mm. The implant may also have at least one lateral
horizontal through-channel 80 extending from a narrow end 25 toward
an adjacent anterior-posterior horizontal through-channel 78.
Lateral through channel 80 may have a width W3 in the range of 2.0
to 5.0 mm and preferably about 3.0 mm, and a radius of curvature R5
in the range of 1.0 to 2.0 mm and preferably about 1.2 mm.
Preferably, the implant has lateral horizontal through-channels 80
at both narrow ends 25. Alternatively, a single lateral horizontal
through channel may extend from one narrow end 25 completely
through the implant to the other narrow end 25. Wall 84 between
horizontal through-channels 78 may have a thickness in the range of
2.0 to 4.0 mm and preferably about 2.2 mm. Channels 78, 80 may be
rectangular, trapezoidal or circular in shape, and may be packed
with bone graft or other bone growth inducing material before and
after implant insertion to aid in spinal fusion.
[0063] Reference is now made to FIG. 4 which is a perspective view
of another embodiment an implant. As in the previous embodiment,
implant 23 has a curved body with substantially parallel arcuate
anterior and posterior faces 24, 26, convex superior and inferior
surfaces 28, 30 contributing to a tapering thickness 31, and
channels 34 for engaging a surgical instrument, such as an
insertion tool. In this embodiment, implant 23 has a substantially
straight or blunted narrow end 50 and a curved narrow end 52
separating parallel, arcuate anterior and posterior faces 24, 26.
As shown in FIG. 5, the final position of implant 23 in disc space
16 may be asymmetric with respect to midline 14 of the patient's
spine. The final position of implant 22 may also be asymmetric with
respect to the midline of the spine.
[0064] As shown in FIGS. 2A, 3A, 16C, 17C and FIG. 11D, the
rocker-like shape of implant 22 enables the surgeon to insert the
implant through the narrow transforaminal window, typically on the
range of about 9.0 to 15.0 mm wide, and seat the implant in the
disc space anteriorly of the dura without disturbing the anterior
curtain of the disc space. The typical surgical technique for the
T-PLIF procedure begins with the patient being placed in a prone
position on a lumbar frame. Prior to incision, radiographic
equipment can assist in locating the precise intraoperative
position of the T-PLIF implant. Following incision, the facets,
lamina and other anatomical landmarks are identified. The affected
vertebrae are distracted using a lamina spreader or a lateral
distractor, both of which are commonly known in the art. In the
latter case, screws may be inserted through the pedicles into the
vertebrae to interface with the lateral distractor. As shown in
FIGS. 6 & 7, following distraction, the transforaminal window
54 is created by removing the inferior facet 56 of the cranial
vertebrae and the superior facet 58 of the caudal vertebrae using
one or more osteotomes 59 and/or automatic burrs (not shown) of
different sizes. A discectomy is performed during which disc
material from the affected disc space may be removed using a
combination of straight and angled curettes. Angled curettes, which
may be configured with rounded profile 60 (FIG. 8A) or a
rectangular profile 61 (FIG. 8B), enable removal of material on the
far side 63 of the disc space opposite transforaminal window 54, as
shown in FIG. 8C.
[0065] After the discectomy is complete, the superficial layers of
the entire cartilaginous endplates are removed with a combination
of straight and angled bone rasps. As shown in FIGS. 9A and 9B,
angled rasps 62 may be angled to reach far side 63 of the disc
space opposite transforaminal window 54. Rasps 62 expose bleeding
bone, but care should be taken to avoid excess removal of
subchondral bone, as this may weaken the anterior column. Entire
removal of the endplate may result in subsidence and loss of
segmental stability. Next, an appropriately sized trial-fit T-PLIF
spacer/template 64, shown in FIGS. 10A and 10B, may be inserted
into the intervertebral disc space using gentle impaction to
determine the appropriate implant thickness for the disc space to
be filled. Fluoroscopy can assist in confirming the fit of the
trial spacer. If the trial spacer 64 appears too loose/too tight,
the next larger/smaller size trial spacer should be used until the
most secure fit is achieved. For example, if a trial fit spacer
with a maximum thickness of 11 mm is too loose when inserted into
the disc space, a physician should try the 13 mm thick spacer, and
so on. Trial fit spacers preferably range in height from about 7 mm
to about 17 mm.
[0066] Upon identifying and removing the best fitting trial spacer,
a T-PLIF implant of appropriate size is selected. At this time,
prior to placement of the T-PLIF implant, bone graft material, such
as autogenous cancellous bone or a bone substitute, may be placed
in the anterior and lateral aspect of the affected disc space.
Channels in implant 22 may also be packed with bone graft material
prior to insertion. As shown in FIGS. 11C and 11D, T-PLIF implant
22 is then held securely using a surgical instrument such as
implant holder 66 (shown more clearly in FIG. 11A), which engages
the channels or slots 34 at one end of implant 22. The tips 67 of
implant holder 66 may be curved or angled to mate with curved
implant 22 and facilitate insertion of implant 22 into disc space
16. T-PLIF implant 22 is then introduced into the intervertebral
disc space 16 via the transforaminal window, as shown in FIG. 11C.
A guide tool having a curved blade 68 (shown in FIG. 12) to match
the curvature of the anterior face of implant 22 may be used to
properly guide the implant into affected disc space 16. The implant
may be guided along an arcuate path to its final position. Slight
impaction may be necessary using implant holder 66 (shown in FIG.
11A) or an impactor tool 70 (shown in FIG. 13A) to fully seat the
implant. As shown in FIGS. 13A & 13B, impactor tool 70 may also
be curved or angled to facilitate seating of the implant through
the narrow transforaminal window. Also, the face 71 of impactor 70
may be concavely shaped to mate with the end of implant 22, as
shown in FIG. 14.
[0067] Once the T-PLIF implant is in the desired final position,
such as the symmetric final position shown in FIG. 15 or the
asymmetric position shown in FIG. 5, implant holder 66, and
possibly guide tool 68, is removed and additional bone graft
material 73 may be inserted into the disc space and/or the channels
74, 78 and 80 of the implant. Preferably, T-PLIF implant 22 is
slightly recessed from the anterior edge 72 of the vertebral body,
but implanted in the anterior-most third of the disc space such
that the implant is closer to the anterior edge 72 of the disc
space than the posterior edge. As shown in FIG. 15, the curvature
of anterior face 24 of implant 22 is substantially the same as the
curvature of anterior edge 72 of disc space 16. In the symmetric
seated position shown in FIG. 15, a single T-PLIF implant 22
provides balanced support to the spinal column about the midline of
the spine.
[0068] While certain preferred embodiments of the implant have been
described and explained, it will be appreciated that numerous
modifications and other embodiments may be devised by those skilled
in the art. Therefore, it will be understood that the appended
claims are intended to cover all such modifications and embodiments
which come within the spirit and scope of the present
invention.
* * * * *