U.S. patent application number 12/316199 was filed with the patent office on 2009-06-25 for spinal implant and cutting tool preparation accessory for mounting the implant.
Invention is credited to Philippe Bouquet, Daniel Chopin, Mingyan Liu, Hans-Jorg Meisel.
Application Number | 20090164015 12/316199 |
Document ID | / |
Family ID | 9510507 |
Filed Date | 2009-06-25 |
United States Patent
Application |
20090164015 |
Kind Code |
A1 |
Liu; Mingyan ; et
al. |
June 25, 2009 |
Spinal implant and cutting tool preparation accessory for mounting
the implant
Abstract
A spinal cage implant is adapted to be inserted in a damaged
intervertebral disc for restoring the discal height and permitting
an arthoesis. The implant comprises a central part with walls and
terminal parts for bearing against the cortical bone of the
vertebral end plates. The implant bears against the vertebral end
plates with terminal parts and contains bone graft material between
walls with an opening to permit bone fusion between the two
vertebrae. The implant permits restoring the physiological lordosis
and the intervertebral height.
Inventors: |
Liu; Mingyan;
(Borg-la-Reine, FR) ; Bouquet; Philippe;
(Lamorlaye, FR) ; Meisel; Hans-Jorg; (Berlin,
DE) ; Chopin; Daniel; (Groffliers, FR) |
Correspondence
Address: |
MEDTRONIC;Attn: Noreen Johnson - IP Legal Department
2600 Sofamor Danek Drive
MEMPHIS
TN
38132
US
|
Family ID: |
9510507 |
Appl. No.: |
12/316199 |
Filed: |
December 10, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10825767 |
Apr 16, 2004 |
7465305 |
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12316199 |
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09486301 |
Sep 29, 2000 |
6746484 |
|
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PCT/IB98/01324 |
Aug 14, 1998 |
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10825767 |
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Current U.S.
Class: |
623/17.11 ;
606/279; 606/79 |
Current CPC
Class: |
A61F 2002/30266
20130101; A61F 2230/0026 20130101; A61F 2210/0004 20130101; A61F
2/4465 20130101; A61F 2/4603 20130101; A61F 2/4455 20130101; A61F
2002/30261 20130101; A61F 2/4611 20130101; A61F 2310/00017
20130101; A61F 2002/30158 20130101; A61B 17/1757 20130101; A61B
2017/0256 20130101; A61F 2002/4627 20130101; A61F 2002/448
20130101; A61F 2/442 20130101; A61F 2002/30774 20130101; A61F
2230/0063 20130101; A61F 2002/30593 20130101; A61F 2310/00023
20130101; A61F 2002/30785 20130101; A61F 2002/30789 20130101; A61F
2002/3028 20130101; A61F 2/447 20130101; A61B 17/1671 20130101;
A61F 2310/00179 20130101; A61F 2002/30777 20130101; A61F 2002/2835
20130101; A61F 2002/30062 20130101; A61F 2002/30576 20130101; A61B
17/025 20130101; A61F 2/28 20130101; A61F 2230/0082 20130101; A61F
2002/30845 20130101 |
Class at
Publication: |
623/17.11 ;
606/279; 606/79 |
International
Class: |
A61F 2/44 20060101
A61F002/44; A61B 17/70 20060101 A61B017/70; A61B 17/00 20060101
A61B017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 16, 1997 |
FR |
97/10664 |
Claims
1-30. (canceled)
31. An implant for insertion between a first vertebra and a second
vertebra, comprising an elongated body extending along a
longitudinal axis, said body including: a first terminal part on
said longitudinal axis defining a first bearing surface to bear
against the first vertebra and a second bearing surface opposite
said first bearing surface to bear against the second vertebra; a
second terminal part on said longitudinal axis opposite said first
terminal part, said second terminal part defining a third bearing
surface to bear against the first vertebra and a fourth bearing
surface opposite said third bearing surface to bear against the
second vertebra; an elongated central part including first and
second longitudinal walls extending along said longitudinal axis
between said first and second terminal parts; a cavity defined
between said first and second terminal parts and between said first
and second longitudinal walls; and a projection extending
transversely to said longitudinal walls and positioned between said
cavity and said second terminal part, said projection configured to
correspondingly penetrate the first or second vertebra when said
first and third bearing surfaces bear against the first vertebra
and said second and fourth bearing surfaces bear against the second
vertebra, wherein said first and second bearing surfaces are
separated by a first distance and said third and fourth bearing
surfaces are separated by a second distance greater than said first
distance to accommodate a spinal curvature, wherein said
longitudinal walls define a substantially constant width of said
body along said longitudinal axis and said width and said first
distance are substantially the same.
32. The implant of claim 31, wherein each of said first and second
longitudinal walls projects transversely from said first and second
terminal parts and includes a tapering edge adapted to penetrate
the first vertebra and the second vertebra.
33. The implant of claim 32, further comprising a second projection
opposite said projection on said second terminal part, said second
projection extending transversely to said first and second
longitudinal walls and positioned between said cavity and said
second terminal part, said second projection configured to
correspondingly penetrate the first or second vertebrae when said
first and third bearing surfaces bear against the first vertebra
and said second and fourth bearing surfaces bear against the second
vertebra.
34. The implant of claim 33, wherein said first projection, said
second projection and said tapering edges of said longitudinal
walls define an opening into said cavity.
35. The implant of claim 34, wherein said tapering edge of each of
said first and second longitudinal walls extends in a longitudinal
direction along said longitudinal axis.
36. The implant of claim 31 wherein: said first terminal part
includes a first flange defining said first bearing surface and a
second flange defining said second bearing surface; and said second
terminal part includes a third flange defining said third bearing
surface and a fourth flange defining said fourth bearing
surface.
37. The implant of claim 31 wherein said first, second, third, and
fourth bearing surfaces are generally flat.
38. The implant of claim 31, wherein said first and second
longitudinal walls each have a generally trapezoidal contour.
39. The implant of claim 31, wherein said cavity holds bone graft
material.
40. The implant of claim 31, wherein at least a portion of the
implant is composed of a porous material.
41. The implant of claim 31, wherein said first and second terminal
parts each include a transverse face at a respective end of said
body, each of said transverse faces including a centrally located
threaded hole extending along said longitudinal axis.
42. An implant for insertion between a first vertebra and a second
vertebra, comprising an elongated body extending along a
longitudinal axis, said body including: a first terminal part on
said longitudinal axis defining a first bearing surface to bear
against the first vertebra and a second bearing surface opposite
said first bearing surface to bear against the second vertebra; a
second terminal part on said longitudinal axis opposite said first
terminal part, said second terminal part defining a third bearing
surface to bear against the first vertebra and a fourth bearing
surface opposite said third bearing surface to bear against the
second vertebra; an elongated central part including a pair of
longitudinal walls extending along said longitudinal axis between
said first and second terminal parts; a cavity defined between said
first and second terminal parts and between said pair of
longitudinal walls, wherein said pair of longitudinal walls define
a constant width of said body along said longitudinal axis; a first
projection extending transversely to and between said pair of
longitudinal walls, said first projection positioned between said
cavity and said second terminal part, said first projection
configured to correspondingly penetrate the first vertebra when
said first and third bearing surfaces bear against the first
vertebra and said second and fourth bearing surfaces bear against
the second vertebra; and a second projection extending transversely
to and between said pair of longitudinal walls, said second
projection being positioned between said cavity and said second
terminal part, said second projection configured to correspondingly
penetrate the second vertebra when said first and third bearing
surfaces bear against the first vertebra and said second and fourth
bearing surfaces bear against the second vertebra.
43. The implant of claim 42, wherein said first and second bearing
surfaces are separated by a first distance and said third and
fourth bearing surfaces are separated by a second distance greater
than said first distance to accommodate a spinal curvature.
44. The implant of claim 43, further comprising: a third projection
extending transversely to and between said pair of longitudinal
walls, said third projection positioned between said cavity and
said first terminal part, said third projection configured to
correspondingly penetrate the first vertebra when said first and
third bearing surfaces bear against the first vertebra and said
second and fourth bearing surfaces bear against the second
vertebra; and a fourth projection extending transversely to and
between said pair of longitudinal walls, said fourth projection
being positioned between said cavity and said first terminal part,
said fourth projection configured to correspondingly penetrate the
second vertebra when said first and third bearing surfaces bear
against the first vertebra and said second and fourth bearing
surfaces bear against the second vertebra.
45. The implant of claim 44, wherein each of said longitudinal
walls includes a first tapering edge and an opposite second
tapering edge, said first and second tapering edges are configured
to penetrate opposing endplates of the first and second
vertebrae.
46. The implant of claim 45, wherein said first tapering edges of
said longitudinal walls, said first projection, and said third
projection define an opening into said cavity.
47. The implant of claim 42, wherein at least a portion of the
implant is composed of a resorbable material.
48. The implant of claim 42, wherein said first and second terminal
parts each include a transverse face at a respective end of said
body, each of said transverse faces including a centrally located
threaded hole extending along said longitudinal axis.
49. The implant of claim 42, wherein said first, second, third, and
fourth bearing surfaces are generally flat.
50. The implant of claim 42, wherein each of said longitudinal
walls has a generally trapezoidal contour.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 10/825,767, filed on Apr. 16, 2004, which is a
divisional of U.S. patent application Ser. No. 09/486,301 entitled:
"SPINAL IMPLANT AND CUTTING TOOL PREPARATION ACCESSORY FOR MOUNTING
THE IMPLANT", now issued as U.S. Pat. No. 6,746,484 and which is a
national stage entry of WO 99/09913 (PCT/IB98/1324) filed Aug. 14,
1998, which claims priority to FR 97/10664 filed Aug. 16, 1997, all
of which are incorporated by reference herein in their
entirety.
TECHNICAL FIELD
[0002] The present invention relates to spinal implant devices and
associated techniques for promoting fusion of two or more
vertebrae.
BACKGROUND
[0003] It is known that when an intervertebral disc degenerates or
is damaged, there is often a compression of the disc and a
reduction in the normal intervertebral height. Typically, this
condition results in abnormal motions that become a source of
pain.
[0004] In order to treat a pathology of this type, the disc is
often stabilized to eliminate the abnormal motions caused by disc
disorders or injuries. Generally, one approach is to prevent
articulation between the two vertebrae situated on each side of the
damaged disc by bone fusion. This fusion fixes the vertebrae to
each other, eliminating the relative mobility causing the pain.
[0005] Various spinal implants to promote fusion between adjacent
vertebrae have been proposed. It has been proposed to interconnect
the two vertebrae by a kind of rigid U-shaped stirrup which
restores the discal height with a bone graft material disposed
inside the stirrup. However, one drawback of this proposal is its
diminishing effectiveness over a period of time.
[0006] A spinal cage is also known which consists of a cylindrical
member provided with a series of openings and provided with
anchoring points. This implant is placed in a recess formed in the
intervertebral disc and penetrates the opposite cortical plates of
the two vertebrae which were previously hollowed out to receive the
implant. This penetration forms openings in the sub-chondral plates
to place spongy bone of the vertebrae in contact with bone graft
material placed inside the implant, facilitating bone fusion. U.S.
Pat. No. 5,015,247 provides one example of this approach.
[0007] Proper performance of a spinal implant of this type requires
balancing the need to promote fusion between the spongy bone and
the need to form a reliable load bearing relationship with the
stronger cortical bone. As a result, the spinal cage must be
neither engaged too far into the openings provided in the cortical
plates to provide a sufficiently dense load bearing surface, nor
insufficiently inserted, in which case the bone fusion between the
two vertebrae would be adversely affected by a poor anchorage.
Thus, there is a demand for devices and techniques that facilitate
attaining the proper balance between fusion and load support.
[0008] The present invention meets this demand and provides other
significant benefits and advantages.
DISCLOSURE OF THE INVENTION
[0009] The present invention relates to spinal fusion implants and
techniques. Various aspects of the present invention are novel,
nonobvious, and provide various advantages. While the actual nature
of the invention covered herein can only be determined with
reference to the claims appended hereto, certain forms which are
characteristic of the preferred embodiments disclosed herein are
described briefly as follows.
[0010] According to one form of the invention, the spinal implant
comprises a body having a central part arranged to allow
arthrodesis and at least one terminal part for bearing against the
cortical bone of the vertebral end plates. The central part is
adapted to penetrate the vertebral end plates, transversely
projecting from the terminal bearing part. Thus the invention
achieves a separation between the end parts constituting the load
bearers, and the intermediate part of the implant which permits
fusion. In addition, the central part may include at least one
cavity for receiving a bone graft material.
[0011] In another form of the present invention, an implant for
insertion between a first vertebra having a first cortical bone
plate and a second vertebra having a second cortical bone plate
includes two terminal parts. The first terminal part defines a
first bearing surface to bear against the first cortical bone plate
and a second bearing surface opposite the first surface to bear
against the second cortical bone plate. The second terminal part
opposes the first terminal part and defines a third bearing surface
to bear against the first cortical bone plate and a fourth bearing
surface opposite the third surface to bear against the second
cortical bone plate. The implant has an elongated central part
defining an upper projection extending past the first and third
surfaces, and a lower projection extending past the second and
fourth surfaces. These projections correspondingly pass through
openings in the first and second cortical bone plates when the
first and third surfaces bear against the first cortical bone plate
and the second and fourth surfaces bear against the second cortical
bone plate. The terminal parts are dimensioned to facilitate
restoration of the natural geometry of the intervertebral space
(lordosis, kyphosis, and parallel discs). Thus, the first and
second surfaces may be separated by a first distance, and the third
and fourth surface may be separated by a second distance greater
than the first distance to accommodate a natural curvature of the
spine.
[0012] In a further form of the present invention, an implant with
two terminal parts also has an elongated central part that includes
a pair of longitudinal walls defining a cavity. The walls define a
first edge projecting past the first and third surfaces and a
second edge projecting past the second and fourth surfaces. The
first and second edges correspondingly penetrate the first and
second cortical bone plates when the first and third surfaces bear
against the first cortical bone plate and the second and fourth
surfaces bear against the second cortical bone plate.
[0013] According to another form, the bearing surfaces of the
terminal end parts are defined by flanges extending from opposing
ends of the implant along its longitudinal axis. Preferably, the
bearing surfaces are generally flat for bearing against the
cortical bone of the vertebral end plates of the two adjacent
vertebrae. It is also preferred that openings be cut into the
cortical plates in their central regions corresponding to the
length of a central part of the implant along the longitudinal axis
and leaving a region of the cortical bone plates around the
periphery of the openings. The length of the remaining peripheral
plate corresponds to the length of the bearing surfaces along the
longitudinal axis. When the implant is placed in position, the
edges of the walls of the central part engage the openings cut in
the cortical plates and consequently do not substantially bear
against the remaining peripheral portion of the plates. A cavity
may be defined by the central part that holds bone graft material
in contact with the spongy bone of the two vertebrae. In contrast,
the bearing surfaces of the flanges are disposed adjacent the edges
of the openings of the cortical plates and bear against the
remaining portions of the plates to establish a strong load bearing
relationship. Thus, both bone fusion and support are distinctly
accommodated by different parts of the implant structure, which
permits obtaining a satisfactory support of the vertebral bodies on
the implant and an excellent arthrodesis.
[0014] Yet another form of the present invention includes a cutting
tool accessory to prepare the cortical plates of two adjacent
vertebrae for insertion of an implant. This tool comprises a
proximal handle connected to an elongate shaft configured to rotate
about a longitudinal axis of the tool. The tool also includes a
first non-cutting portion with the shaft extending therethrough and
being configured to rotate relative thereto. A cutting portion is
fixed to the shaft to rotate therewith and is positioned distal to
the first non-cutting portion. The cutting portion includes a first
pair of generally parallel opposing faces and second pair of
opposing faces each extending between the first pair of faces. The
second pair of faces each define a number of cutting teeth. A
second non-cutting portion is fixed to the cutting portion that
includes a distal head. The first non-cutting portion, the cutting
portion, and the second non-cutting portion have a rotatably
selectable alignment that presents a generally constant height
corresponding to the intersomatic space defined between the
cortical bone plates to facilitate insertion therein. Once
inserted, the cutting portion may be rotated out of this alignment
to cut a first opening in the first cortical bone plate and a
second opening into the second cortical bone plate. The cutting
portion and non-cutting portions may be arranged to provide
uniform, symmetrical cutting of these openings with a predetermined
length corresponding to the dimensions of a given implant
device.
[0015] In an additional form, a technique of spinal fixation
includes cutting adjacent vertebrae and inserting an implant
therebetween to promote fusion and provide suitable support. The
implant may be inserted by anterior or posterior surgical
approaches. The cutting may be performed by the cutting tool of the
present invention and may include initially inserting the tool so
that a first pair of faces are in contact with a respective one of
the first and second cortical bone plates, turning a handle to
rotate the cutting portion to remove cortical bone with cutting
teeth defined by a second pair of faces, and withdrawing the tool.
The tool may be used to form openings readily positioned in the
central region of the adjacent vertebrae that leaves cortical bone
plate about the openings. The insertion of the implant may include
positioning the implant of the present invention between the first
and second vertebrae and turning the implant about one quarter of a
turn.
[0016] It is envisioned that the implants of the present invention
may be used with other tools and procedures, that the tools of the
present invention may be used with other implants and procedures,
and that the procedures of the present invention may be used with
other implants and tools as would occur to those skilled in the art
without departing from the spirit of the present invention.
[0017] Accordingly, one object of the invention is to provide a
spinal implant arranged to facilitate proper fusion of two or more
vertebrae. The implant may be arranged to have at least one
structural part to promote bone fusion through contact with spongy
vertebral bone and one or more other structural parts adapted for
contact with cortical bone to provide load support.
[0018] Another object is to provide a tool accessory to facilitate
implantation of devices suitable to promote fusion.
[0019] Still another object is to provide a technique for preparing
a site between two vertebrae to be fused and inserting an
implant.
[0020] Other objects, features, benefits, forms, aspects, and
advantages of the present invention will become apparent from the
description and drawings herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a perspective view, to a larger scale, of one
embodiment of a spinal implant of the present invention.
[0022] FIG. 2 is a perspective view of one embodiment of a cutting
tool of the present invention for mounting the implant of FIG.
1.
[0023] FIG. 3 is a perspective view of a distracting wedge or
"distractor" used for carrying out a surgical method in accordance
with the present invention.
[0024] FIG. 4 is a partial elevational view diagrammatically
illustrating the insertion of the cutting tool between two
vertebrae.
[0025] FIG. 5 is a partial elevation view showing the cutting tool
after rotation of the cutting portion through 90.degree. and
penetrating the cortical plates of the two adjacent vertebrae.
[0026] FIG. 6 is a partial sectional view taken in a sagittal plane
showing the implant of FIG. 1 positioned in an intervertebral disc
for achieving a spinal fusion.
[0027] FIG. 7 is a perspective view of a spinal segment in the
intervertebral disc in which two implants have been installed.
MODE(S) FOR CARRYING OUT THE INVENTION
[0028] For the purpose of promoting an understanding of the
principles of the invention, reference will now be made to the
embodiments illustrated in the drawings and specific language will
be used to describe the same. It will nevertheless be understood
that no limitation of the scope of the invention is thereby
intended. Any alterations and further modifications in the
described device, and any further applications of the principles of
the invention as described herein are contemplated as would
normally occur to one skilled in the art to which the invention
relates.
[0029] FIGS. 1, 6, and 7 depict spinal cage implant 1. Implant 1 is
adapted to be inserted in a cavity provided in a damaged
intervertebral disc 2 (FIG. 7), so as to restore the normal height
of the intervertebral space between the two vertebrae V1 and V2
adjacent to the disc 2, for example the lumbar vertebrae L3, L4 as
depicted in FIG. 7. FIG. 1 shows implant 1 disposed along its
longitudinal axis YY. Implant 1 comprises a hollow body 3 of
elongate shape, having a central part 3c formed by two parallel
longitudinal walls 4 arranged to permit the arthrodesis and, at the
two opposite ends of the central part 3c, in the direction of the
implantation of the implant 1, two terminal parts 5, 6 for bearing
against the cortical bone 14 of vertebral cortical bone plates 15,
16 of the two vertebrae (V1, V2) adjacent to the disc 2 (see, for
example, FIG. 6).
[0030] The longitudinal walls 4 define therebetween a cavity 7 and
are provided with openings 11. Terminal parts 5, 6 are disposed
opposite each other along axis YY and each include a terminal face
defining a centrally located threaded hole 11a. Holes 11a are
configured for engagement by a threaded shaft of an
insertion/manipulation accessory (not shown) to facilitate
placement of implant 1 between vertebrae V1, V2. The cavity 7 is
provided to receive a graft G of spongy bone or any other material
favoring bone fusion, for example a synthetic ceramic.
[0031] Terminal part 5 has two opposite bearing surfaces 12
transverse to axis YY which are so dimensioned that they are
separated by distance d1. Terminal part 6 has two opposite bearing
surfaces 13 transverse to axis YY which are so dimensioned that
they are separated by distance d2. Distances d1, d2 are adapted to
the geometry of the intervertebral space to be restored. When d2 is
greater than d1 as depicted, implant 1 is preferred for fusion of
vertebrae in a region of the spine having a natural curvature.
Distance 1 corresponds to a maximum width dimension of body 3. In
one embodiment, the width of body 3 is generally constant along
axis YY and is about the same as distance d1 to facilitate a proper
fit between vertebrae V1, V2 as will become more apparent
hereinafter.
[0032] The terminal parts 5, 6 are extended by load bearing flanges
8, 9, namely two load bearing flanges 8 for part 5 and two load
bearing flanges 9 for part 6. In the depicted embodiment, flanges
8, 9 form parallel bars perpendicular to the longitudinal walls 4,
and define generally flat surfaces 12, 13 for bearing against the
cortical bone 14 of the vertebral end plates 15, 16.
[0033] In the illustrated embodiment, the longitudinal walls 4 have
a substantially trapezoidal contour of which the small base
corresponds to the terminal part 5 and the large base corresponds
to the terminal part 6. The walls 4 constituting the central part
3c of the implant 1 are so shaped as to transversely project from
the terminal bearing parts 5, 6, as can be seen in FIGS. 1 and 6.
Thus the walls 4 can penetrate respective openings 19, 21 of the
vertebral plates 15, 16 whose edges bear against the bearing
surfaces 12, 13 of the flanges 8, 9 (FIG. 6). Flanges 8, 9 are
shaped to define step projections 17a, 18a to further facilitate
penetration of openings 19, 21. Projections 17a, 18a also provide a
lip to maintain alignment of bearing surfaces 12, 13 with cortical
bone plates 15, 16 about the periphery of the openings as shown in
FIG. 6. Walls 4 also include tapered edges 4a to facilitate
penetration. Correspondingly, central part 3c has upper projection
3a and lower projection 3b defined by edges 4a. Notably, edges 4a
and projections 3a, 3b transversely project away from surfaces 12,
13.
[0034] Implant 1 may be placed in position in the intervertebral
disc 2 after preparation with cutting tool accessory 22 which will
now be described with reference to FIGS. 2, 4, and 5. Preferably,
tool 22 is made from a metallic material suitable for surgical use.
Tool 22 has a milling cutter 23 including central cutting portion
24 and two non-cutting portions 31, 36 arranged at opposite ends of
central cutting portion 24. Non-cutting portions 31, 36 have height
h corresponding to the intersomatic space and permitting uniform,
symmetrical cutting of a predetermined length through a central
region of both vertebral plates 15, 16. Preferably, the geometry of
portions 24, 31, 36 is determined for preparing the intersomatic
space with the geometry of implant 1 to restore the natural
lordosis of the intervertebral space, and correspondingly the
distances represented by h and d1 are approximately equal.
[0035] Central cutting portion 24 has a trapezoidal shape with two
generally smooth, longitudinal faces 25 opposed to each other.
Faces 25 are configured to facilitate insertion into the
intersomatic space being generally separated from each other by
distance h. Central cutting portion 24 also has cutting faces 26
extending between faces 25. Cutting faces 26 define a number of
uniformly spaced apart cutting teeth 28. Teeth 28 each extend along
a generally straight path that is slanted at an oblique angle
relative to longitudinal axis XX of tool 22. Preferably, central
cutting portion 24 is made from a suitable metallic material that
has been machined to form teeth 28.
[0036] Non-cutting portion 31 is fixed to the distal end of central
cutting portion 24. Portion 31 extends from central cutting portion
24 to provide a distal head in the form of a parallel piped-shaped
bar. Portion 31 has a first dimension substantially the same as
distance h to be generally coextensive with faces 25 of central
cutting portion 24. Portion 31 also has opposing faces 32 separated
from each other by a distance H as shown in FIG. 5. Preferably
distance H is approximately equal to distance d2 when tool 22 is
being utilized to install implant 1.
[0037] Tool 22 also includes a shaft or shank 33 connected to a
proximal actuating handle 34. Shank 33 is fixed to central cutting
portion 24 and non-cutting portion 31. Shank 33 extends from the
small end face 27 remote from the non-cutting head 31 and
terminates in the handle 34 which permits rotating the cutting
portion 24 about the longitudinal axis XX of tool 22.
[0038] Non-cutting portion 36 has a rectangular shape with
generally planar faces 37, 38. Portion 36 may be inserted between
two consecutive vertebrae during rotation of central cutting
portion 24. Portion 36 extends in the direction toward the handle
34 by a tubular part 40 and through block 40a which terminates in
the vicinity of the handle 34. Non-cutting portion 36 is provided
with lateral stops 39 capable of being put into abutment against
the sides of the vertebrae (V1, V2) after insertion therebetween.
Non-cutting portion 36 encloses shank 33. Shank 33 is configured to
rotate relative to portion 36. Correspondingly, when handle 34 is
turned, shank 33, central cutting portion 24, and non-cutting
portion 31 rotate together about axis XX with non-cutting portion
36 preferably remaining stationary. It should be noted that the
partial view of FIGS. 4 and 5 do not show handle 34 and depict a
cutaway view of non-cutting portion 36 with shank 33 projecting
therefrom.
[0039] Various non-limiting embodiments of a spinal fixation or
fusion procedure of the present invention are next described. One
procedure is characterized by: (a) cutting the vertebrae V1, V2 and
disc 2 with tool 22 to prepare for implantation and (b) inserting
the implant 1 between vertebrae V1, V2. Another more detailed
procedure for fusing two vertebrae together is described in terms
of procedural stages (a)-(h) as follows:
[0040] (a) A surgeon first separates the dural sleeve forming the
extension of the bone marrow if the procedure is in the lumbar
region and then carries out a discectomy to provide space for
implant 1 in disc 2.
[0041] (b) The surgeon inserts between the two vertebrae V1, V2
from the rear (posterior), two lordosis distractors 41 as shown in
FIG. 3. Each distractor 41 consists of a parallel piped-shaped part
42 extended by a wedge part 43 of triangular section. Part 42 is
provided with thrust plate 44. Distractors 42 are inserted
laterally with respect to the cavity provided by the discectomy of
stage (a). Each distractor 41 is initially inserted by presenting
its narrower aspect between V1 and V2, and, then turned through
90.degree. so as to spread apart the vertebrae and restore the
discal height and the height of the considered vertebral segment.
Next, one of the distractors 41 is removed.
[0042] (c) The surgeon inserts tool 22 between the vertebrae V1, V2
as shown in FIG. 4 so that the larger, smooth faces 25 are in
contact with the vertebral plates 15, 16. When the cutting portion
24 is correctly positioned in the central region of the cortical
plates, stops 39 come into abutment with the outer surface of the
vertebrae V1, V2 and non-cutting portion 36 is partly inserted
between the plates 15, 16.
[0043] (d) Next, the surgeon turns handle 34, causing cutting
portion 24 to rotate about axis XX. Typically, portion 24 is
rotated a number of times. As rotation continues cutting teeth 28
engage the central parts of cortical plates 15, 16 (FIG. 5),
gradually removing cortical bone 14. At the end of the hollowing
out of these plates, the cutting faces 26 of the central cutting
portion 24 and the cutting teeth 28 have cut through the plates 15,
16 to form generally centrally located openings 19, 21. Remaining
portions of plates 15, 16 then bear against the opposite faces 32
of non-cutting portion 31 and against non-cutting portion 36.
[0044] (e) Then, the surgeon withdraws tool 22 from between
vertebrae V1, V2.
[0045] (f) Next, the surgeon inserts implant 1, previously filled
with the bone graft G, between the plates 15, 16 from the rear to a
suitable position by presenting the terminal part 6 and the bearing
flanges 9 at the front end. The implant 1 is presented flat, so
that longitudinal walls 4 are generally parallel to the cortical
plates 15, 16 and initially come into contact therewith during
insertion.
[0046] (g) Thereafter, the surgeon turns implant 1 through a
quarter of a turn about its longitudinal axis (YY) so as to place
it in the position shown in FIG. 6 with walls 4 substantially
perpendicular to the cortical plates and its flat surfaces 12, 13
generally parallel to cortical plates 15, 16. Implant 1 may be
inserted and turned by engaging hole 11a with a correspondingly
threaded shaft of an accessory tool (not shown). The edges 4a of
the longitudinal walls 4 which define projections 3a, 3b are
inserted into openings 19, 21 thereby passing through plates 15,
16, while remaining portions of plates 15, 16 bear against flat
surfaces 12, 13. Implant 1 is then in its final position in which
it is stabilized. The bone graft G is in contact with the spongy
part S1, S2, promoting bone fusion.
[0047] (h) The surgeon removes the second distractor 41 then
repeats the preceding sequence of stages (a) through (g) to mount a
second spinal cage implant 1 by placing it in a position generally
parallel to the first cage implant 1 on the other side of the axis
of the spinal column resulting in the configuration depicted in
FIG. 7 (implants 1 are shown in phantom).
[0048] In other embodiments, it is envisioned that the described
stages may be altered, deleted, combined, repeated, or resequenced
as would occur to those skilled in the art. By way of nonlimiting
example, the procedure according to the present invention may
utilize one or more different tools to prepare the spine for
fixation by the implant of the present invention. In another
example, the tool of the present invention may be utilized to
prepare a surgical site for a different implant.
[0049] Indeed, the scope of the invention is not intended to be
limited to the described embodiment and may also include variants
within the scope of the accompanying claims. For example, terminal
bearing surfaces 12, 13 for the vertebral plates may have any
shape, such as a curved or cylindrical shape with plates 15, 16
being correspondingly cut so as to allow placing the bearing
surfaces in a suitable position. Further, these bearing surfaces
may be interconnected in pairs and constitute a single member 50 as
shown in FIG. 6.
[0050] Likewise, the central part of the implant of the present
invention may have any shape, preferably retaining edges that
project from the terminal bearing parts. In particular, the body
may have a multitude of cells. Also, it should be generally noted
that the implant and tool of the present invention may be adapted
to a geometry of the spine with respect to lordosis, kyphosis or
parallel vertebral end plates. Thus, the present invention includes
application to adjacent vertebrae other than L3, L4.
Correspondingly, the implant and the cutting portion of the tool
may have a different shape, such as a cylindrical geometry other
than the generally conical geometry depicted. Also, instead of
using the disclosed implant 1, the spinal space prepared by tool 22
can be filled with any other material as would occur to those
skilled in the art.
[0051] According to the other embodiments, the implant can be
partly or totally constituted by porous rehabitable or resorbable
materials favoring osteointegration. Such embodiments include: (a)
an implant according to the above-illustrated geometry entirely
made of a resorbable or rehabitable material; (b) an implant in
which the whole of the central part is made of a resorbably or
rehabitable material; or (c) an implant in which the periphery of
the central part is made of a metallic or other material and the
inside part is of a material favoring osteointegration that may be
in an initially solid, pasty or liquid state.
[0052] In another alternative embodiment an implant is provided
with only one bearing end part in which the end portion opposite to
the bearing end part is open and forms a U shape for receiving a
bone graft or a rehabitable or resorbable material.
[0053] French Patent Application Number 97 10664 filed on Aug. 26,
1997 to which priority is claimed is hereby incorporated by
reference as if it were specifically set forth in its entirety
herein. While the invention has been illustrated and described in
detail in the drawings and foregoing description, the same is to be
considered as illustrative and not restrictive in character, it
being understood that only the preferred embodiments have been
shown and described and that all changes, modifications, and
equivalents that come within the spirit of the invention as defined
by the following claims are desired to be protected.
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