U.S. patent application number 11/348214 was filed with the patent office on 2006-09-07 for bone implants and methods.
This patent application is currently assigned to Zimmer Spine, Inc.. Invention is credited to David A. Hanson, Ross A. Longhini, Daniel D. McPhillips, Steven J. Seme.
Application Number | 20060200166 11/348214 |
Document ID | / |
Family ID | 46280334 |
Filed Date | 2006-09-07 |
United States Patent
Application |
20060200166 |
Kind Code |
A1 |
Hanson; David A. ; et
al. |
September 7, 2006 |
Bone implants and methods
Abstract
The disclosure provides implants, instruments and methods for
bone fusion procedures. In some embodiments, the implants are
particularly advantageous for use between opposing vertebral bodies
to facilitate stabilization or arthrodesis of an intervertebral
joint. The implants include, at least, a support component that
provides structural support during fusion. In a typical embodiment,
the implants also include a growth component. A growth component
provides an environment conducive to new bone growth between the
bones being fused. Several unique configurations to enhance fusion,
instruments for insertion and methods for insertion are also
disclosed.
Inventors: |
Hanson; David A.; (St.Louis
Park, MN) ; Longhini; Ross A.; (West Lakeland,
MN) ; McPhillips; Daniel D.; (Ham Lake, MN) ;
Seme; Steven J.; (Savage, MN) |
Correspondence
Address: |
WOOD, HERRON & EVANS;ATTN: PATENT DOCKETING
2700 CAREW TOWER
441 VINE STREET
CINCINNATI
OH
45202
US
|
Assignee: |
Zimmer Spine, Inc.
Minneapolis
MN
|
Family ID: |
46280334 |
Appl. No.: |
11/348214 |
Filed: |
February 6, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
10080375 |
Feb 19, 2002 |
7018416 |
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|
11348214 |
Feb 6, 2006 |
|
|
|
09896926 |
Jun 28, 2001 |
6635060 |
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|
11348214 |
Feb 6, 2006 |
|
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|
09611237 |
Jul 6, 2000 |
6641582 |
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09896926 |
Jun 28, 2001 |
|
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60269777 |
Feb 16, 2001 |
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Current U.S.
Class: |
606/99 |
Current CPC
Class: |
A61F 2/4603 20130101;
A61F 2002/30383 20130101; A61F 2002/30892 20130101; A61F 2002/30879
20130101; A61B 17/1757 20130101; A61F 2002/30599 20130101; A61B
2017/0256 20130101; A61B 17/1659 20130101; A61B 17/1671 20130101;
A61F 2/4465 20130101; A61F 2002/30593 20130101; A61F 2002/30131
20130101; A61B 17/1735 20130101; A61F 2250/0063 20130101; A61F
2/4611 20130101; A61F 2002/3082 20130101; A61B 17/1604 20130101;
A61F 2230/0013 20130101; A61F 2220/0025 20130101; A61F 2/30744
20130101; A61F 2/442 20130101; A61F 2002/30904 20130101 |
Class at
Publication: |
606/099 |
International
Class: |
A61F 2/34 20060101
A61F002/34 |
Claims
1. A bone implant system comprising: a bone support member for
intervertebral implantation, the bone support member having a
partial ring shape that defines a central cavity including a closed
end and an open end; and an elongate insertion tool for inserting
the bone support member between adjacent vertebrae, the insertion
tool including an insertion head sized to fit securely within the
central cavity of the bone support member such that the bone
support member is retained on the insertion tool during the
insertion process; and an insert block for insertion in the bone
support member after implantation of the bone support member and
removal of the insertion tool from the inner cavity, the insert
block including a bone growth promoting material, the insert block
having a pre-manufactured size and shape adapted to substantially
fill the inner cavity.
2. The bone implant system of claim 1, wherein the insertion head
is sized and shaped to complement the shape of the central
cavity.
3. The bone implant system of claim 1, wherein the insertion head
is sized and shaped to occupy a majority of the central cavity.
4. The bone implant system of claim 1, wherein the bone support
member and the insertion head include a rail and slot arrangement
for securing the bone support member to the insert head.
5. The implant system of claim 1, wherein the bone support member
includes cortical bone and the insert block includes cancellous
bone.
6. The implant system of claim 5, wherein the insert block is a
natural material.
7. The bone implant system of claim 4, wherein the rail and slot
arrangement includes: opposing slots defined within the central
cavity by the bone support member; oppositely positioned rails
provided on the insert head; the rails being configured to slide
within the slots when the insert head is inserted into the central
cavity.
8. The bone implant system of claim 1, wherein the insertion head
includes a curved distal nose and generally parallel sidewalls that
extend proximally from the distal nose.
9. The bone implant system of claim 1, wherein the inner cavity and
the insert block have complementary shapes.
10. The bone implant system of claim 1, wherein the inner cavity is
coextensive with a center of the bone support member.
11. The bone implant system of claim 1, wherein the bone support
member is non-threaded.
12. A method for implanting a spinal implant between adjacent
vertebrae, the spinal implant including a bone support member and
an insert block, the bone support member defining an inner cavity
having an open end and a closed end, the method comprising:
inserting the bone support member between the adjacent vertebrae
with an insertion tool having an end portion retained within the
inner cavity; removing the end portion of the insertion tool from
the inner cavity of the bone support member after implantation of
the bone support member; and inserting the insert block into the
inner cavity after the end portion of the insertion tool has been
removed from the inner cavity.
13. The method of claim 12 further comprising selecting an insert
block with a shape that complements the shape of the inner
cavity.
14. The method of claim 12 further comprising selecting an insert
block with a shape that fills a majority of the inner cavity.
15. The method of claim 12 wherein inserting the insert block
further comprising inserting an insert block that includes
cancellous bone.
16. The method of claim 12 further comprising preparing the
adjacent vertebrae by rasping one or more of an endplate of the
adjacent vertebrae.
17. A bone implant system comprising: a bone support member for
intervertebral implantation, the bone support member having a
partial ring shape that defines a central cavity including a closed
end and an open end; and an elongate insertion tool for inserting
the bone support member between adjacent vertebrae, the insertion
tool including an insertion head sized to fit securely within the
central cavity of the bone support member such that the bone
support member is retained on the insertion tool during the
insertion process; and an insert block for insertion in the bone
support member after implantation of the bone support member and
removal of the insertion tool from the inner cavity, the insert
block including a bone growth promoting material, the insert block
having a pre-manufactured size and shape adapted to substantially
fill the inner cavity, wherein the bone support member and the
insertion head include a rail and slot arrangement for securing the
bone support member to the insert head.
18. The system of claim 17, wherein the insertion head is sized and
shaped to complement the shape of the central cavity.
19. The system of claim 17, wherein the bone support member and the
insertion head include a rail and slot arrangement for securing the
bone support member to the insert head.
20. The system of claim 17, wherein the bone support member
includes cortical bone and the insert block includes cancellous
bone.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 10/080,375, filed Feb. 19, 2002, which claims the benefit of
U.S. Provisional Application No. 60/269,777, filed Feb. 16, 2001,
and is a continuation-in-part of U.S. application Ser. No.
09/896,926, filed Jun. 28, 2001, now U.S. Pat. No. 6,635,060, which
is a continuation-in-part of U.S. application Ser. No. 09/611,237,
filed Jul. 6, 2000, now U.S. Pat. No. 6,641,582, which applications
are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] This invention pertains to bone implants, instruments and
procedures. Specifically, the invention provides bone implants,
instruments and methods to facilitate fusion of bone. The invention
is particularly suited for stabilization or fusion of the
intervertebral disc space between adjacent vertebrae.
BACKGROUND OF THE INVENTION
[0003] Chronic back problems cause pain and disability for a large
segment of the population. Frequently, the cause of back pain is
traceable to diseased disc material between opposing vertebrae.
When the disc material is diseased, the opposing vertebrae may be
inadequately supported, resulting in persistent pain. Surgical
techniques have been developed to remove all or part of the
diseased disc material and fuse the joint between opposing
vertebral bodies. Stabilization and/or arthrodesis of the
intervertebral joint can reduce the pain associated with movement
of a diseased intervertebral joint. Spinal fusion may be indicated
to provide stabilization of the spinal column for a wide variety of
spine disorders including, for example, structural deformity,
traumatic instability, degenerative instability, post-resection
iatrogenic instability, etc.
[0004] Generally, fusion techniques involve partial or complete
removal of the diseased disc and packing the void area with a
suitable matrix for facilitating a bony union between the opposing
vertebral bodies.
[0005] Surgical devices for facilitating interbody fusion are
known. Some devices are positioned external to the intervertebral
joint during the fusion process. Other devices are positioned
within the intervertebral joint. Devices positioned within the
joint space typically distract the joint space and provide
stabilization by causing tension on the annulus fibrosus and other
supporting tissues surrounding the joint space. Examples of devices
positioned within the joint space are disclosed in, for example,
U.S. Pat. Nos. 5,458,638, 5,489,307, 5,055,104, 5,026,373,
5,015,247, 4,961,740, 4,743,256 and 4,501,269, the entire
disclosures of which are incorporated herein by reference. Some
systems use both external fixation and internal fixation
devices.
[0006] Regardless of the type or location of the fusion device, a
bone graft and/or other implant is often used to facilitate new
bone growth. The surface area, configuration, orientation, surface
texture and deformity characteristics of an implant or bone graft
placed in the disc space can affect the stability of the joint
during fusion and thus affect the overall success of a fusion
procedure.
[0007] Accordingly, the present invention is directed to unique
implants or bone grafts that can be inserted at a fusion site, with
or without other stabilizing systems, and instruments and methods
for inserting the same.
SUMMARY OF THE INVENTION
[0008] One inventive aspect of the present disclosure relates to an
implant (e.g., a spinal implant) having a first component having
support mechanical characteristics and a second component having
mechanical characteristics for allowing bone in-growth. Other
inventive aspects include systems and methods for implanting
multi-component implants. It should be noted that the examples are
provided for illustrative purposes and are not intended to limit
the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a perspective view of an implant that is an
embodiment of the invention;
[0010] FIG. 2 is a top plan view of the implant of FIG. 1;
[0011] FIG. 3 is a front elevational view of the implant of FIG.
1;
[0012] FIG. 4 is a side elevational view of the implant of FIG.
1;
[0013] FIG. 5 is a perspective view of a portion of the implant of
FIG. 1;
[0014] FIG. 6 is a front elevational view of the implant of FIG.
5;
[0015] FIG. 7A is a perspective view of an implant cap that is an
embodiment of the present invention;
[0016] FIG. 7B is a side elevational view of the cap of FIG.
7A;
[0017] FIG. 7C is a top plan view of the cap of FIG. 7A;
[0018] FIG. 7D is a front elevational view of the cap of FIG.
7A;
[0019] FIG. 8A is a top plan view of an inferior vertebrae prior to
a preparation step according to the principles of the present
invention;
[0020] FIG. 8B is a front elevational view of the inferior
vertebrae of FIG. 8A and a corresponding superior vertebrae;
[0021] FIG. 9A is a top plan view of the inferior vertebrae of FIG.
8A after a preparation step according to the principles of the
present invention;
[0022] FIG. 9B is a front elevational view of the inferior
vertebrae and the superior vertebrae of FIG. 8B after the
preparation step of FIG. 9A;
[0023] FIG. 10A is a top plan view of the inferior vertebrae of
FIG. 9A after another preparation step according to the principles
of the present invention;
[0024] FIG. 10B is a front elevational view of the inferior
vertebrae and the superior vertebrae of FIG. 9B after the
preparation step of FIG. 10A;
[0025] FIG. 11 is a front elevational view of the inferior
vertebrae and the superior vertebrae of FIG. 10B after placement of
a support member in accordance with the present invention;
[0026] FIG. 12 is a front elevation view of the inferior vertebrae
and the superior vertebrae of FIG. 11 after placement of a growth
member in accordance with the present invention;
[0027] FIG. 13 is a perspective view of an implant kit that is an
embodiment of the present invention;
[0028] FIG. 14 is a perspective view of a wedge and portal assembly
of the implant kit of FIG. 13;
[0029] FIG. 15 is a top plan view of a rasp that is an embodiment
of the present invention;
[0030] FIG. 16 is a side elevational view of the rasp of FIG.
15;
[0031] FIG. 17 is a proximal end-on elevational view of the rasp of
FIG. 15;
[0032] FIG. 18 is an enlarged partial perspective view of teeth on
a rasp head of FIG. 15;
[0033] FIG. 19 is an enlarged partial top plan view of a rasp head
of the rasp of FIG. 15;
[0034] FIG. 20 is a top plan view of a bone-cutting instrument that
is an embodiment of the present invention;
[0035] FIG. 21 is a side elevational view of the bone-cutting
instrument of FIG. 20;
[0036] FIG. 22 is a distal end-on elevational view of the
bone-cutting instrument of FIG. 20;
[0037] FIG. 23 is a top plan view of an implant insertion tool that
is an embodiment of the present invention;
[0038] FIG. 24 is a side elevational view of the implant insertion
tool of FIG. 23;
[0039] FIG. 25 is a distal end-on elevational view of the implant
insertion tool of FIG. 23;
[0040] FIG. 26 is a side elevational view of a sleeve that is an
embodiment of the present invention;
[0041] FIG. 27 is a cross-sectional view of the sleeve of FIG.
26;
[0042] FIG. 28 is an end-on elevational view of the sleeve of FIG.
26;
[0043] FIG. 29 is a top plan view of an insertion tool handle that
is an embodiment of the present invention;
[0044] FIG. 30 is a cross-sectional view of the handle of FIG. 29
taken along line 30-30
[0045] FIG. 31 is an end-on elevational view of the handle of FIG.
29;
[0046] FIG. 32 is side elevational view of an implant insertion
tool that is another embodiment of the present invention;
[0047] FIG. 33 is a top plan view of the implant insertion tool of
FIG. 32;
[0048] FIG. 34 is a perspective view of a portal insertion step
according to the principles of the present invention;
[0049] FIG. 35 shows a vertebrae preparation step using a rasp
according to the principles of the present invention;
[0050] FIG. 36 shows a vertebrae preparation step using a box
chisel according to the principles of the present invention;
[0051] FIG. 37 is a perspective view of a support member being
positioned upon an incertion tool according to the principles of
the present invention;
[0052] FIG. 38 shows a support member insertion step according to
the principles of the present invention;
[0053] FIG. 39 is shows a growth member insertion step according to
the principles of the present invention;
[0054] FIG. 40 shows a portal extraction step according to the
principles of the present invention;
[0055] FIG. 41 is a perspective view of an implant that is another
embodiment of present invention;
[0056] FIG. 42 is a side elevational view of the implant of FIG.
41;
[0057] FIG. 43 is a front elevational view of the implant of FIG.
41; and
[0058] FIG. 44 is a top plan view of the implant of FIG. 41.
DETAILED DESCRIPTION OF THE INVENTION
[0059] The present invention is directed toward the fusion of
bones. The invention provides natural and/or synthetic bone
implants that can function as a bone graft between adjacent bones
to be fused. The implants of the invention include unique
arrangements, configurations and components to facilitate fusion
and maintain stability during the fusion process.
[0060] The implants, instruments and methods of the invention can
be used in a variety of bone fusion procedures. In some
embodiments, the invention may be particularly advantageous for
intervertebral stabilization or arthrodesis of the intervertebral
disc space between adjacent vertebrae. Accordingly, for purposes of
description herein, the invention will be described by reference to
intervertebral fusion procedures in the lumbar region of the spine.
However, this description is for exemplary purposes only and should
not be construed to limit the intended scope of use of the
disclosed implants, instruments or methods. For example, in the
case of vertebral fusion, the implants, instruments and methods of
the invention can be used to fuse cervical, thoracic, lumbar or
lumbo-sacral vertebrae.
[0061] In general, the implants, instruments and methods of the
invention are directed to facilitating greater continuity between
the bone formed at the fusion site and the bones fused. The
implants are also designed to provide greater structural support at
the fusion site to maintain stability and alignment at the fusion
site, to reduce healing time and optimize the structural integrity
of the new bone formed at the fusion site. The implants of the
invention can also facilitate the ease of implanting and
positioning implants at a fusion site.
[0062] The implants can be prepared from natural materials,
synthetic materials, or a combination of natural and synthetic
materials. As used herein, "natural material" means "bone" and
includes bone harvested from humans or animals. "Bone" may further
include heterologous, homologous and autologous (i.e., xenograft,
allograft, autograft) bone derived from, for example, fibula,
tibia, radius, ulna, humerus, cranium, calcaneus, tarsus, carpus,
vertebra, patella, ilium, etc. Bone may further include one or more
bone products which have been partially or completely
demineralized, prepared for transplantation (e.g., via removal of
immunogenic proteins), and/or processed by other techniques.
Additionally, the implants can be prepared from products made from
bone, such as chips, putties, and other similar bone products. In
some embodiments, human source bone is preferred for human
applications. In a preferred embodiment, the bone of an implant can
be cancellous and/or cortical.
[0063] Cortical implant material can be obtained from known long
bones, such as the humerus, radius, ulna, tibia, femur, fibula,
etc. Cancellous material can be obtained from the patella, distal
condyles, tibial plateau, femoral head, etc. Cranial, pelvic (e.g.
iliac crest) and patellar bone can advantageously provide both
cortical and cancellous bone in a single piece. Indeed, these
sources can provide an implant having cancellous bone surrounded on
opposing sides by cortical bone.
[0064] "Synthetic materials" include non-bone materials such as
titanium, stainless steel, porous titanium, ceramic, carbon fiber,
silicon, methylmethacrylate, polytetrafluoroethylene, polycarbonate
urethane, PEEK and other materials suitable for use as an
orthopedic implant. Further, the materials may include any of the
above synthetic materials combined with a natural bone material.
For example, the material may comprise a combination of bioglass
and bone chips or bone chips with a bonding agent. As stated above,
an implant of the invention can consist solely of a synthetic
material. In other applications, a synthetic material may be used
in combination with cancellous bone.
[0065] In one embodiment, an implant can include a support
component or member and a growth component or member. The support
component includes a material having mechanical properties suitable
for providing, support, stabilization or alignment at the fusion
site. An exemplary material for the support component includes
cortical bone. The growth component includes a material having
mechanical or physical properties that allow or support new bone
in-growth. An exemplary material for the growth component includes
cancellous bone. In such an embodiment, the support component of
the implant provides strength for column support and/or
stabilization, and the growth component facilitates tissue growth,
vascularization and deposition of new bone (e.g., by providing
increased surface area). In one embodiment, the support component
includes a material that provides greater axial column strength
than the growth component, and the growth component includes a
material that allows for enhanced bone in-growth as compared to the
support component.
[0066] As indicated above, in some embodiments, the "support"
portion (component) of an implant of the invention is provided by
cortical bone or a natural or synthetic material having
biomechanical and biological characteristics similar to cortical
bone. The support portion provides support, stabilization, and
facilitates alignment at the fusion site. The "growth" portion
(component) of the implant can include a material that allows bone
in-growth (i.e., an osteoconductive material) such as a bone growth
matrix. In these embodiments, the growth portion provides a matrix
or scaffold to support new bone growth. One preferred bone growth
component that can also provide some support is cancellous bone.
"Porous" synthetic materials can also act as a supporting, growth
component. As used herein, a "porous synthetic material" includes,
for example, porous titanium, porous ceramics, porous stainless
steel and like materials. Such porous materials can provide
characteristics of both the growth portion and the support portion
of the implant.
[0067] In some embodiments, the growth component of the implant can
be prepared from cancellous bone or alternatively a bone growth
matrix shaped into any one of the advantageous configurations of
growth components disclosed herein. Suitable bone growth matrices
can be resorbable or nonresorbable, and with or without
osteoinductive properties or materials. Examples of suitable
osteoconductive matrices include synthetic materials, such as
Healos.TM., available from Orquest, Mountain View, Calif. Examples
of osteoinductive materials include bone marrow, blood platelets
and/or bone morphogenic proteins (BMPs).
[0068] An implant of the invention can have one of several
configurations including a single component or a plurality of
components. In one embodiment, the implants have first and second
bearing surfaces, which in use are positioned adjacent opposing
vertebrae endplates. The bearing surfaces can include an engaging
surface having a surface texture that enhances stability at the
bone-implant interface and reduces the likelihood of motion during
the fusion process. Examples of engaging surfaces suitable for the
invention include ridges, knurls, grooves, teeth, serrations,
etc.
[0069] Natural or synthetic bone implants of the invention can be
manufactured using procedures known in the art. Methods for
preparing natural bone implants are disclosed in for example, U.S.
Pat. Nos. 6,033,438; 5,968,047; 5,585,116; 5,112,354; and
5,439,684; the entire disclosures of which are incorporated herein
by reference.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
[0070] The implants, instruments and methods of the invention will
now be described by reference to the several drawing figures. The
functional features of the implants of the invention can be
embodied in any of a number of specific configurations. It will be
appreciated, however, that the illustrated embodiments are provided
for descriptive purposes and should not be used to limit the
invention. In addition, in many exemplary embodiments, cortical and
cancellous bone are used. It will be appreciated from an
understanding of the present invention that the cortical or support
and/or growth portions of the implants can be substituted with
synthetic materials.
[0071] I. Representative Bone Implant
[0072] FIGS. 1-4 illustrate a multi-piece bone implant 320 that is
a representative embodiment of the present invention. The bone
implant 320 includes a bone support member 341 (also referred to as
a support component or support portion) configured for
intervertebral implantation. As best shown in FIG. 1, the bone
support member 341 defines a cavity 327 (i.e., a void, pocket or
channel) having an open end 342 positioned opposite from a closed
end 343. The bone implant 320 also includes a growth member 321
(also referred to as a growth component or growth portion) having a
shape that generally corresponds to or matches (i.e., complements)
a shape of the cavity 327. The open ended configuration of the
cavity 327 allows the growth member 321 to be inserted into the
cavity 327 through the open end 342. In one embodiment, the growth
member 321 is inserted after the bone support member 341 has been
implanted between adjacent vertebrae. In another embodiment, the
bone support member 341 is implanted such that the open end 342 of
the bone support member 341 faces in an anterior direction (i.e.,
toward the ventral surface of the patient), and the growth member
321 is inserted into the cavity 327 using an anterior approach.
Alternatively, the open end 342 may face in an anterior-lateral or
lateral direction and the growth member 342 may be inserted using
an anterior-lateral or lateral approach, respectively.
[0073] A. Bone Support Member
[0074] Referring to FIG. 2, the bone support member 341 of the
implant 320 has a generally "C-shaped" configuration and includes
outer and inner wall surfaces 323, 324. The shape of the bone
support member 341 can also be described as "partial ring-shaped",
"U-shaped", "semi-annular", or generally "horseshoe-shaped". In a
preferred embodiment, the bone support member 341 includes first
and second arms 325, 326 that are integrally connected at mid-line
ML. Interior portions of the arms 325, 326 oppose one another so as
to define the cavity 327 of the support member 341 therebetween.
For example, the inner wall surface 324 includes opposing portions
325a and 326a, respectively, defined by the arms 325, 326. The
opposing portions 325a, 326a extend on opposite sides of the
mid-line ML from the open end 342 of the cavity 327 to the closed
end 343 of the cavity 327.
[0075] Referring still to FIG. 2, the opposing portions 325a, 326a
of the inner wall surface 324 include opposing curved portions
325b, 326b located adjacent the closed end 342 of the cavity 327
and opposing planar portions 325c, 326c located adjacent the open
end 342 of the cavity 327. The curved portions 325b, 326b are shown
having a concave, circular curvature. The planar portions 325c,
326c are generally parallel and define an insertion channel 371 for
guiding the growth member 321 into the cavity 327 during insertion,
and for aligning the growth member 321 within the cavity 327. In a
preferred embodiment, the insertion channel is sufficiently wide
between the planar portions 325c, 326c to receive the growth member
321 therein without requiring the arms 325, 326 to be flexed apart.
The outer wall surface 323 of the support member 341 is shown
including a convex, circular curvature that is concentric with the
curvature defined by the curved portions 325b, 326b of the inner
wall surface 324. In other embodiments, the support member 341 may
be non-circular and/or not curved at all. For example, the support
member 341 could include other shapes such as rectangles, squares,
ovals, ellipses, etc.
[0076] FIGS. 5 and 6 illustrate the support member 341 with the
growth component 321 removed from the cavity 327. As can be seen,
inner wall 324 includes a first groove 336 extending partially
along first arm 325 and a second groove 337 extending partially
along second arm 326. The grooves 336, 337 (e.g., slots) oppose one
another and extend from the open end 342 of the cavity 327 toward
the closed end 343 of the cavity 327. At least portions of the
grooves 336, 337 are preferably defined by the planar portions
325c, 326c of the inner wall surface 324. Although grooves 336 and
337 are shown as being discontinuous, the groove can be continuous
around inner wall 324. As will be described below, grooves 336 and
337 provide for attachment of a cover 350 (FIGS. 7A-7D) or an
implant insertion tool 800 (FIGS. 23 and 24). While the grooves
336, 337 are shown including rectangular cross-sections, other
shaped cross-sections such as rounded or triangular shapes could
also be used. Further, the portions of the tool 800 or the cover
350 may or may not be complementary with the shapes of the
grooves.
[0077] Referring to FIG. 4, the bone support member 341 includes
first and second bearing surfaces 328, 329 separated by a height or
thickness of the support member 341. The inner and outer wall
surfaces 323, 324 extend generally perpendicularly between the
first and second bearing surfaces 328, 329. In the illustrated
embodiment, the first bearing surface 328 includes an engaging
surface comprising ridges 328a, and the second bearing surface 329
includes an engaging surface comprising ridges 329a. As discussed
previously, engaging surfaces reduce the likelihood of
post-implantation mobility of an implant.
[0078] Referring to FIGS. 5 and 6, the cavity 327 of the bone
support member 341 preferably extends completely through the bone
support member 341 between the top load bearing surface 328 and the
bottom load bearing surface 329. Thus, the cavity 327 is open on
the top and bottom sides of the bone support member 341 to
facilitate exposure of top and bottom surfaces of the growth member
321 to the endplates of adjacent vertebrae when the growth member
321 positioned within the cavity 327.
[0079] While the bone support member 341 can have a constant
height, in a preferred embodiment, the support member 12 is
slightly tapered so as to define a wedge shape. In one embodiment,
the bone support member 341 can include a lordotic taper at an
angle .theta. in the range of 0-16 degrees (see FIG. 4). As shown
in FIG. 4, in an exemplary embodiment with a lordotic taper, the
support member 341 has a maximum thickness H.sub.max adjacent the
open end 342 of the cavity 327 and a minimum thickness H.sub.min
adjacent the closed end 343 of the cavity 327. In certain
embodiments, a gradual taper is provided between the two
thicknesses H.sub.max and H.sub.min.
[0080] In one non-limiting embodiment, the support member 341 can
have a maximum depth D in the range of 20-30 mm, a maximum width W
in the range of 20-30 mm, an average thickness (the average of the
two thicknesses H.sub.max and H.sub.min) in the range of 6-24 mm.
In another embodiment, the support member 341 is made of a
homogeneous material having consistent (i.e., non-varying)
mechanical properties. For example, in one embodiment, the support
member 341 can include a bone material having a consistent degree
of mineralization. In other embodiments, the support member 341 can
include regions of decreased mineralization (e.g., demineralized
portions) that provide regions of increased flexibility. In a
preferred embodiment, the support member 341 includes a cortical
bone cross-section from a femur or tibia bone.
[0081] B. Bone Growth Member
[0082] In certain embodiments, the growth member 321 preferably has
a pre-manufactured or pre-formed shape. The terms
"pre-manufactured" and "pre-formed" mean that the growth member 321
has a pre-defined shape prior to insertion in the cavity 327. In
some embodiments, the pre-manufactured shape of the growth member
321 complements the shape of the cavity 327. In certain other
embodiments, the growth member 321 includes multiple sub-units
having pre-defined individual shapes and/or having collective
shapes. In another embodiment, the growth member 321 includes a
block of cancellous bone having a shape that complements the shape
of the cavity 327.
[0083] As shown in FIG. 2, the bone growth member 321 includes a
first end 370 positioned opposite from a second end 372. The first
end 370 includes an end curvature that generally matches the
curvature of the inner wall surface 324 adjacent the closed end 343
of the cavity 327. The bone growth member 321 also includes
substantially parallel sidewall surfaces 374 that extend between
the first and second ends 370 and 372. The second end 372 of the
bone growth member 321 includes a substantially planar surface 376
that extends between the sidewall surfaces 374. In one preferred
embodiment, the planar surface 376 is generally perpendicular
relative to the sidewall surfaces 374. The bone growth member 321
also may include top and bottom surfaces 378 and 380 that are
generally parallel relative to one another. In the embodiment
shown, the top and bottom surfaces 378 and 380 extend between the
first and second ends 370 and 372 of the bone growth member 321 and
are generally perpendicular relative to the sidewall surfaces 374
and the planar end surface 376. In the depicted embodiment, the
bone growth member 321 has a thickness H.sub.gm that is
substantially constant from the first end 370 to the second end
372. In alternative embodiments, the thickness can taper gradually
along the entire or part of the distance between the first and
second ends 370 and 372. In some preferred embodiments, the
thickness H.sub.gm of the bone growth member 321 is greater than
the thickness H.sub.max of the bone support member 341. In these
embodiments, the thickness H.sub.gm is preferably at least 2 or 3
mm greater than the thickness H.sub.max.
[0084] In certain embodiments, the top and bottom surfaces 378 and
380 are adapted for direct contact with cancellous bone upon
implantation. In these embodiments, to promote bone growth, it is
desirable for the surface area provided by the top and bottom
surfaces 378 and 380 to provide a significant portion of the total
contact area provided by the implant 320 (the combined contact area
provided by both the support member 341 and the bone growth member
321). In one embodiment, the top and bottom surfaces 378 and 380
provide at least 20 percent of the total contact area. In another
embodiment, the top and bottom surfaces 378 and 380 provide at
least 25 percent of the total contact area. In still another
embodiment, the top and bottom surfaces 378 and 380 provide at
least 30 or 40 percent of the total contact area. In a further
embodiment, the top and bottom surfaces 378, 380 each have a width
W.sub.gm (shown in FIG. 2) at least 40 percent as wide as the width
W of the support member 341, and a depth D.sub.gm (shown in FIG. 2)
at least 50 percent as deep as the depth D of the support member
341.
[0085] In a preferred embodiment, the bone growth member 321 has a
non-threaded exterior. In this embodiment, the bone growth member
321 can be inserted into the cavity 327 by sliding the growth
member 321 therein without requiring rotation. Additionally, the
non-threaded configuration of the growth member 321 eliminates the
need for tapping threads into the bone support member 341 or the
opposing vertebral end plates between which the growth member 321
is desired to be implanted.
[0086] Referring to FIG. 3, the bone implant 320 has a dome shape
for limiting end plate removal and thereby minimizing subsidence.
By "dome shape", it is meant that the implant is curved or tapered
on the top and bottom surfaces 378 and 380 such that a thickness of
the implant increases in a direction extending from the outer
perimeter of the support member 341 toward the mid-line ML. In one
embodiment, the degree of curvature of the dome is defined by a
3-inch radius.
[0087] Other implant configurations are disclosed in U.S.
application Ser. Nos. 60/325,585 and 60/325,804 which are hereby
incorporated by reference.
[0088] C. End Cap
[0089] FIGS. 7A-7D illustrate an optional cap 350 for positioning
in cavity 327 between arms 325 and 326. In the illustrated
embodiment, cap 350 has a first bearing surface 351, a second
bearing surface 352, an inner surface 353 and an outer surface 354.
Bearing surface 351 includes an engaging surface 352 which can be
similar to that of implant 320 (bearing surface 352 can also
include an engaging surface). On each side, cap 350 includes a tab
360 and 361. Tabs 360 and 361 are configured to pass into grooves
337 and 336. As illustrated in FIGS. 7A and 7B, tab 360 (and 361)
have a major height G.sub.M, and minor height G.sub.m. The
difference in height G.sub.M and G.sub.m provides tabs 360 and 361
with a diverging taper from inner surface 353 to outer surface 354.
Thus, when tabs 360 and 361 have passed into grooves 337 and 336 as
cap 350 is advanced within arms 325, 326 the taper from height
G.sub.m to height G.sub.m is selected to provide for a snug fit
between tabs 360 and 361 and grooves 336 and 337 to retain cap 350
in position. That is, cap 350 is friction fit into implant 320. The
grooves 336 and 337 of implant 320, and a cap, such as cap 350 can
be used with other implants, such as implants 120 and 140.
[0090] Cap 350 can also include a bore 365 that may be threaded
(not shown) which permits for attachment of an insertion tool
having a threaded male end to mate with bore 365.
[0091] II. General Implantation Method
[0092] To implant the implant 320, a discectomy is performed on a
patient to partially or completely remove a diseased disc between
adjacent vertebrae 20, 22 (see FIGS. 8A and 8B). With the disc
material removed, end plates 20', 22' of the adjacent vertebra 20,
22 are distracted/separated (e.g., with a wedge distractor). After
the vertebra 20, 22 have been spaced-apart, first regions 24 (see
FIGS. 9A and 9B) of the end plates 20', 22' are
prepared/conditioned to receive the bone implant 10. For example,
the end plates 20', 22' can be conditioned by rasping the end
plates 20', 22' to remove cartilaginous material from the end
plates 20', 22' and to smooth the cortical bone of the end plates
20', 22' by reducing surface irregularities. Next, second regions
26 of the end plates 20', 22' are prepared within the first regions
24 (see FIGS. 10A and 10B). In a preferred embodiment, the second
regions 26 have smaller areas than the first regions 24 and are
subsets or sub regions of the first regions 24. In one embodiment,
the second regions 26 are prepared by using a cutting tool (e.g., a
chisel) to remove the cortical bone from the second regions 26 and
expose underlying cancellous bone. In this embodiment, the exposed
cancellous bone at the second regions 26 is preferably surrounded
by partial rings 27 of cortical bone (e.g., including the
epiphyseal ring).
[0093] After preparation of the end plates 20', 22', the bone
support member 341 is inserted between the distracted vertebrae 20,
22 (see FIG. 11). As so inserted, the top and bottom load bearing
surfaces 328, 329 of the support member 341 directly engage the
partial rings 27 of cortical bone to provide column support. After
implantation of the support member 341, the bone growth member 321
is inserted into the cavity 327 through the open end 342. As so
inserted, the top and bottom sides 378 and 380 of the growth member
341 directly contact the exposed cancellous bone of the second
regions 26 to provide a fusion lattice (see FIG. 12).
[0094] In a preferred embodiment, each first region 24 is
co-extensive with a majority of the surface area of each end plate
20', 22'. As shown in FIGS. 9A and 9B, each first region 24 covers
substantially all of the surface area of each corresponding end
plate 20', 22'. Thus, in such an embodiment, the implant 320 is
sized to fill a majority of the intervertebral space between the
end plates 20', 22' and to contact a majority of the surface area
of each end plate 20', 22'. In one embodiment, each second region
26 defines an area that coincides with 20-80 percent of the total
area defined by each corresponding first region 24. In another
embodiment, each second region 26 defines an area that coincides
with 30-70 percent of the total area defined by each corresponding
first region 24. In yet another embodiment, each second region 26
defines an area that coincide, with 40-60 percent of the total area
defined by each corresponding first region 24.
[0095] III. Implantation Kit
[0096] FIG. 13 illustrates an embodiment of a kit (i.e., an
instrument set) for implanting the bone implant 320 of FIG. 1. The
kit includes a wedge distractor 50 for providing a desired spacing
between two vertebrae desired to be stabilized. The kit also
includes a portal 52 for maintaining the spacing between the
vertebrae after the wedge distractor 50 has been removed from
between the vertebrae. The portal 52 includes a window 54 for
allowing access to the space between the distracted vertebrae.
Certain embodiments of the wedge distractor and portal system have
previously been disclosed in U.S. Pat. No. 6,224,599, incorporated
herein by reference. The kit further includes instruments that can
be inserted through the window 54 of the portal 52 for preparing
the vertebral end plates. For example, the kit includes a rasp 600
for removing cartilage from the vertebral end plates and for
conditioning the cortical bone of the vertebral end plates. A box
chisel 510 is included in the kit for removing cortical bone from
the vertebral end plates to provide regions of exposed cancellous
bone.
[0097] The box chisel 510 includes a hollow handle 518 configured
to slide over a shaft 603 of the rasp 600 such that the shaft 603
functions as a guide for controlling the cutting location of the
chisel 510. A side handle 701 having an alignment pin 703 is
adapted to maintain rotational alignment between the rasp 600 and
the box chisel 510. The alignment pin 703 inserts within an opening
605 defined by the shaft 603 of the rasp 600 and also extends
through a slot 550 defined by the handle 518 of the chisel 510. The
slot 550 allows the chisel 510 to be moved axially back and forth
along the rasp handle to provide a chiseling motion. As the chisel
510 is moved along the rasp handle, the pin 703 slides along the
slot 550. The range of axial motion of the chisel 510 is limited by
the length of the slot 550. During chiseling, the side handle 701
is preferably grasped to stabilize the rasp 600. A slap hammer 501
can be used to provide greater impact forces for cutting the
vertebrae with the chisel 510. The slap hammer 501 includes a slot
503 for allowing the slap hammer 501 to be moved past the alignment
pin 703 when slid over the handle 518 of the chisel 510.
[0098] The kit further includes an insertion tool 800 having an
insertion head 803 (also referred to as a "working end") sized to
fit within the cavity 327 of the bone support member 341. In use,
the bone support member 341 is mounted on the insertion head 803,
and the insertion tool 800 is used to insert the bone support
member 341 between the distracted and pre-conditioned vertebrae.
Thereafter, the insertion head 803 is removed from the cavity 327
of the bone support member 341, and the growth member 321 is
inserted into the cavity 327 through the open end 342 of the cavity
327. Alternatively, a conventional tool, such as a forceps, can be
used to insert the growth member 321 into the cavity 327. After the
implant 320 has been implanted into the intervertebral space, a
portal extractor 60 can be used to remove the portal 52.
[0099] A. Wedge Distractor, Portal and Portal Extractor
[0100] FIG. 14 shows the wedge distractor 50 and the portal 52 of
the kit of FIG. 13 in alignment with one another. The wedge
distractor 50 includes a generally rectangular base portion 64. A
back side 65 of the base portion 64 defines a threaded opening (not
shown) sized to receive a threaded end of a handle 66. A vertebral
wedge 68 projects forwardly from a front side 67 of the base
portion 64.
[0101] The portal 52 includes a generally rectangular frame 70
defining the portal window 54. The portal window 54 is sized to
receive the wedge distractor 50 with a friction fit between the
base portion 64 of the wedge distractor 50 and the frame 70 of the
portal 52. The portal 52 also includes spaced apart distraction
paddles 74 that align on opposite sides of the vertebral wedge 68
when the wedge distractor 50 is press fit within the portal 52. The
distraction paddles 74 and the vertebral wedge 68 preferably have
substantially the same side profile.
[0102] Referring to FIG. 13, the portal extractor 60 is sized to
fit within window 54 of portal 52. Handle 66 (shown in FIG. 14)
preferably connects to extractor 60. Tab 63 of extractor 60 fits
within opening 65 of portal 52 to allow portal 52 to be pulled from
the intervertebral space.
[0103] B. Rasp
[0104] FIG. 15 is a top view and FIG. 16 a side view of the rasp
600 of the kit of FIG. 13. The rasp 600 is adapted to function as
both as a trial sizer, i.e. for a particularly sized and shaped
implant, and a rasp. Rasp 600 has a proximal end 601 and a distal
end 602 spaced along longitudinal axis X-X. At the proximal end 601
of shaft 603, there is a roughened area 604 that can be in the form
of knurls, etchings, grooves, ridges, or other suitable patterns to
enhance manual gripping of the shaft 603. The opening 605 for
receiving the alignment pin 703 of handle 701 extends transversely
through the proximal end 601 of the shaft 603. As previously
indicated, the opening 605 and alignment pin 703 assist in
maintaining rotational alignment between the rasp 600 and the
chisel 510.
[0105] At the distal end 602, rasp 600 includes a rasp head 606. In
the illustrated embodiment, rasp head 606 includes an outer wall
607, an inner wall 608 and has a generally "C-shaped" configuration
with a first arm 609 continuous with a second arm 610. The inner
wall 608 defines a pocket or receptacle which is sized to
complement and receive the distal end of the chisel 510. The first
arm 609 and second arm 610 are spaced apart from the shaft 603.
Rasp head 606 includes a first engaging surface 611 and a second
engaging surface 612. In the illustrated embodiment, the first and
second engaging surfaces 611, 612 have ridges 613 (see FIGS.
17-19). In alternative embodiments, knurls, etchings, teeth,
grooves or other suitable patterns may be substituted for ridges
613.
[0106] As illustrated best in FIG. 17, in this embodiment, rasp
head 606 has a major height H.sub.M and minor height H.sub.m. The
taper from the major height to the minor height can be from about
0.degree. to about 16.degree.. The shape and configuration of the
rasp head 606 corresponds to the shape and configuration of an
implant. In one embodiment, the rasp head 606 corresponds in size
and configuration with the support component 341 of the two-part
implant 320 of FIGS. 1-4. In such an embodiment, the rasp head 606
preferably has the same lordotic taper angle and the same dome
curvature as the support member desired to be implanted. The space
between the first and second arms 609, 610 of the rasp head 606
corresponds generally with the shape of the growth component 321 of
the implant 320. It will be appreciated, however, that the
configuration of the rasp head 606 can be square, rectangular,
circular, oval, etc., depending on the configuration of the
implant(s) to be inserted into the channel.
[0107] As a trial sizer, the rasp 600 provides a means for
determining the appropriate size bone cutting instrument and
implant to use for a particular implant site. Multiple rasps 600
are provided, with incrementally different sized, shaped, and/or
tapered rasp heads 606 corresponding to different sized, shaped,
and/or tapered implants. The surgeon inserts and removes the
various rasps 600 and determines (e.g., via evaluation of the
frictional fit) which one is the correct size for the
intervertebral space. The ridges 613 on the upper and lower
surfaces of the rasp head act as a rasp to condition the end plates
of the upper and lower adjacent vertebrae.
[0108] Proximal to the distal end 602, the shaft 603 of the rasp
600 also includes markings 614 at predetermined distances from the
distal edge 615 of the rasp head. During use, markings 614 provide
the surgeon with an indication of the depth of distal penetration
of rasp 600 between adjacent vertebrae.
[0109] C. Box Chisel
[0110] FIG. 20 is a top view and FIG. 21 a side view of the chisel
510 shown in the kit of FIG. 13. Chisel 510 has a proximal end 515
and a distal end 516 spaced along longitudinal axis X-X. At the
proximal end 515 of shaft 517 there is a handle 518 for operating
chisel 510. The handle 518 has a roughened area 519 that can be in
the form of knurls, etchings, grooves, ridges, or other suitable
patterns to enhance manual gripping of the handle 518. At the
distal end 516, chisel 510 includes a first cutting edge 520, a
second cutting edge 521, and third and fourth cutting edges 522 and
523. In the illustrated embodiment, cutting edges 520, 521, 522 and
523 are at the distal end of chamber 525. First, second, third, and
fourth cutting edges 520, 521, 522 and 523 are beveled 520a, 521a,
522a, and 523a, respectively, to facilitate cutting and removal of
bone. An internal hollow bore 527 extends from the proximal end 515
through the chisel 510 to the distal end 516 to receive the shaft
603 of rasp 600 and to receive bone.
[0111] In the illustrated embodiment, elongated openings 550 and
551 extend through the handle 518 and shaft 517, respectively, of
the chisel 510. As described previously, opening 550 allows for
alignment of the chisel 510 with rasp 600. Opening 551 provides
additional access to the internal bore 527 for cleaning the
instrument and reduces the weight of the instrument.
[0112] FIG. 22 is a distal end-on view of chisel 510 showing that
first and second cutting edges 520 and 521 define a height
dimension C.sub.H and the cutting edges 522 and 523 define a width
dimension W.sub.C. The perimeter configuration of cutting edges
520, 521, 522, and 523 in FIG. 22 is a rectangular shape
particularly suited for preparing a channel or implant bore between
adjacent bones for insertion of a two-part implant having a
configuration such as that of the implant 320 shown in FIG. 1.
[0113] As previously indicated, implant 320 includes growth member
321, such as cancellous bone, and support member 341, such as
cortical bone. The growth member 321 has a similar size and shape
as the distal end of the chisel 510 (e.g., dimension W.sub.gm of
growth member 321 corresponds to dimension W.sub.C of chisel 510
and dimension H.sub.gm of growth member 321 corresponds to
dimension C.sub.H of chisel 510). Also, the end curvature (i.e., at
end 370) of the growth member 321 corresponds to the curvature of
edges 520 and 521 of the chisel 510. The support member 341 has a
similar size and configuration as the rasp head (see for example
FIGS. 15, 16). The support member 341 of the implant may be the
same size as the rasp head, or it can be larger or smaller than the
rasp head. The support member 341 of the implant can be about 0 mm
to about 4 mm larger in height than the rasp head. The height
dimension C.sub.H of the chisel 510 can be about 3 mm taller than
the maximum height of the support member 321 of the implant. It
will be appreciated, however, that the perimeter configuration of
cutting edges 520, 521, 522, and 523 can be square, circular, oval,
etc., depending on the external configuration of the implant to be
inserted into the channel. The length of the first and second
cutting edges 520 and 521 can vary to correspond with the depth of
the vertebrae.
[0114] To cut different sized channels, a set of chisels 510 will
be available which has instruments with incrementally different
sizes of cutting edges 520, 521, 522, 523 corresponding to a
particular size implant. For example, chisels 510 having first and
second cutting edges 520, 521 with different heights C.sub.H will
be available to permit the surgeon to select a cutting edge height
corresponding to a particular disc space height. In addition, it
will be appreciated that the illustrated cutting edges 520 and 521
(and 522 and 523) are parallel. In alternative embodiments, cutting
edges 520 and 521 (and 522 and 523) can form a converging or
diverging taper.
[0115] D. Insertion Tool
[0116] FIGS. 23-25 illustrate the insertion tool 800 of the kit of
FIG. 13. As illustrated, implant insertion tool 800 has a proximal
end 801 and a distal end 802 having a working end 803. Working end
803 includes tabs 804 and 805 that fit cooperatively within grooves
336, 337 of the support member 341 of the implant 320. In addition,
the working end 803 includes a slot 806 that permits
resilient/elastic arms 807 and 808 to flex or expand laterally away
from axis A.sub.T.
[0117] In a typical embodiment, arms 807 and 808 are spring biased
to expand away (e.g., laterally) from axis A.sub.T in the normal,
relaxed position. A sleeve 820 (FIGS. 26-28) can then be slid from
the proximal end 801 of the insertion tool 800, over the slot 806,
to force arms 807 and 808 towards (e.g. medially) axis A.sub.T.
That is, when the sleeve is advanced distally it brings arms 807
and 808 together towards axis A.sub.T. In this position, the
working end 803 of implant insertion tool 800 can be inserted into
an implant. Similarly, where useful for additional control, tabs
804 and 805 can be inserted into grooves 336, 337 of an implant.
The sleeve can then be slid towards the proximal end to allow arms
807 and 808 to expand away from axis A.sub.T to provide friction
holding of an implant on the working end 803. After placement of an
implant, the sleeve can be slid distally to bring arms 807 and 808
back toward axis A.sub.T to remove implant insertion tool 800,
leaving the implant in place. Other arrangements providing for
expansion and contraction of arms 807, 808, relative to axis
A.sub.T also are contemplated by this disclosure
[0118] Thus, an implant can be mounted on the working end 803 of
implant insertion tool 800 allowing the surgeon to manipulate an
implant via tool 800 into a suitable position at the fusion
site.
[0119] Referring back to FIGS. 23 and 24, in one embodiment the
insertion tool 800 has a threaded region 809 at the proximal end
801. The threaded region 809 threads within a distal end 851 of a
handle 850 (shown in FIGS. 29-31). The handle 850 has a roughened
area 852 that can be in the form of knurls, etchings, grooves,
ridges, or other suitable patterns to enhance manual gripping of
the handle 850. In one embodiment, the distal end 851 of the handle
850 has exterior threading to match internal threading 821 on a
sleeve 820. The sleeve 820 is hollow and has a bore 822 extending
from the proximal end 823 to the distal end 824, and which is sized
to fit over the proximal end 801 of the implant insertion tool 800.
When the sleeve 820 is not being used to force the arms 807, 808 of
the insertion tool toward one another, the internal threadings 821
can be threaded on the distal end 851 of the handle 850 to prevent
unintended sliding of the sleeve 820.
[0120] FIGS. 32 and 33 illustrate an alternative embodiment of an
implant insertion tool 400 suitable for use with an implant of the
invention. As illustrated, implant insertion tool 400 has a
proximal end 401 including a handle 402 for operating the
instrument and a distal end 403 having a working end 404. Working
end 404 include tabs 405 and 406 that fit cooperatively within
grooves 336 and 337 of implant 320. Thus, implant 320 can be
mounted at the working end 404 of implant insertion tool 400
allowing the surgeon to manipulate implant 320 via tool 400 into a
suitable position at the fusion site.
[0121] IV. Method of Implantation Using Kit
[0122] In one embodiment, a technique for practicing the method of
FIGS. 8-12 involves using the kit of FIG. 13. In practicing the
method, a window, approximately the width of the portal 52 is cut,
symmetrically about the midline, in the annulus and a complete
discectomy is performed. Preferably, the lateral annulus is
retained to act as a tension band around the implant 320.
[0123] After cutting the window in the annulus, the appropriate
sized wedge distractor 50 and portal 52 are selected based on
pre-operative templating. A sizing chart for various components of
the kit is set forth below. The dimensions listed correspond to the
heights of portions of the components that are inserted into the
intervertebral space. TABLE-US-00001 INSTRUMENT LETTER CODE A B C D
E PORTAL 10 mm 12 mm 14 mm 16 mm 18 mm DISTRACTOR WEDGE 10 mm 12 mm
14 mm 16 mm 18 mm RASP/TRIAL 10 mm 12 mm 14 mm 16 mm 18 mm CORTICAL
GRAFT 10 mm 12 mm 14 mm 16 mm 18 mm BOX CHISEL 13 mm 15 mm 17 mm 19
mm 21 mm INSERTER HEAD 13 mm 15 mm 17 mm 19 mm 21 mm CANCELLOUS
BLOCK 13 mm 15 mm 17 mm 19 mm 21 mm
[0124] Once the wedge distractor 50 and portal 52 of the
appropriate size have been selected, the portal 52 is inserted over
the wedge distractor 50, and the combined unit is then delivered
into the midline of the disc space until a desired spacing and
annular tension is achieved between the adjacent vertebrae 20, 22.
Proper placement is achieved when the portal 52 is flush with the
vertebrae 20, 22 as shown in FIG. 34. The proper position of the
portal 52 can be confirmed by utilizing fluoroscopy.
[0125] With the portal in the position shown in FIG. 34, the slap
hammer 501 can be used to help facilitate the removal of the wedge
distractor 50 from the portal 52. Additional discectomy or
posterior decompression can be completed, if necessary.
[0126] After the wedge distractor 50 has been removed, a rasp 600
of the appropriate size is selected. The end plates 20', 22' are
then prepared by inserting the head of the rasp through the portal
52 and rasping in an anterior/posterior direction. Preferably, the
rasp 600 is advanced until shoulder 607 of the rasp is adjacent the
posterior most edge 51 of the portal 52 (see FIG. 35). In this
position, the thickness of the rasp head is slightly larger (e.g.,
about one-half millimeter) than the portal paddles. In this manner,
the rasp prepares the first regions 24 of the end plates 20', 22'
as shown in FIG. 9A. Fluoroscopy can be used to ensure proper
placement of the rasp within the disc space.
[0127] Once the end plates 20', 22' have been prepared with the
rasp as indicated above, a box chisel 510 of the appropriate size
is preferably selected. Box chisel 510 is then inserted over the
shaft 603 of the rasp 600. Rotational alignment between the rasp
600 and the chisel 510 is provided by the pin 703 of side handle
701 (see FIG. 13).
[0128] When rotational alignment between the rasp 600 and the box
chisel 510 achieved, the chisel 510 is slid along the shaft 603 of
the rasp toward the vertebrae 20, 22. The chisel 510 is then
impacted (e.g., with slap hammer 501) against the vertebrae 20, 22
until edges 522 and 523 of the chisel 510 contact the back side 617
(shown in FIG. 15) of the rasp head (see FIG. 36). Thereafter, the
rasp 600 and chisel 510 combination can be removed from the
intervertebral space using the slap hammer 501.
[0129] After the rasp 600 and box chisel 510 have been removed, an
insertion head 803 having a size corresponding to the size of the
rasp 600 and chisel 510 is selected. The insertion sleeve 820 is
placed over the shaft of the insertion tool 800 and slid toward the
insertion head 803 causing the arms 807, 808 of the insertion head
803 to be flexed together. Thereafter, the support member 341 of
the implant 320 is inserted onto the insertion head 803 such that
tabs 804, 805 of the insertion head fit within the corresponding
grooves 336, 337 of the support member 341 (see FIG. 37). The
sleeve 820 is then slid away from the insertion head 803 and
threaded on the handle 850 of the insertion tool 800. With the
sleeve 820 pulled back, the arms 807, 808 of the insertion head
flex outwardly to securely hold the support member 341 on the
insertion head.
[0130] The insertion tool 800 is then used to insert the support
member 341 through the portal 52 into the intervertebral space
between the vertebrae 20, 22. Light impaction may be utilized to
deliver the support member 341 into its final position. Final
positioning is achieved when the insertion head contacts a positive
stop 27 formed in the vertebrae 20, 22 by the chisel 510 (see FIG.
38). Thereafter, the inserter sleeve 820 is unthreaded from the
inserter handle 850 and pushed toward the inserter head 803 to
release the inserter head 803 from the support member 341. The
insertion tool 800 is then removed from the support member 341
leaving the support member 341 within the intervertebral space.
[0131] After the support member 341 has been implanted, a growth
member 321 having a size that corresponds to the support member 341
is selected. Preferably, the growth member 321 has a height that is
at least two millimeters, and preferably about three millimeters
larger than the corresponding support member 341. A tool such as a
forceps 29 is used to place the growth member 321 into the channel
(i.e., region 26 shown in FIGS. 10B-12) created by the chisel 510
(see FIG. 39). A tamp can be used to tap the growth member into the
channel. Once the growth member 321 is in its final position, the
portal extractor 60 is used to remove the portal 52 as shown in
FIG. 40. The procedure is then finalized by conducting conventional
surgical closure and post-operative care procedures.
[0132] V. Alternative Implant Configuration
[0133] FIGS. 41-44 illustrate an alternative embodiment of an
implant 140. According to this embodiment, implant 140 includes a
body 141 having a "C-shaped" configuration comprising a first arm
142 continuous with a second arm 143 forming a space 144
therebetween. Body 141 also includes an external wall 146 and an
internal wall 147. As best illustrated in FIGS. 8a and 8c, the
facing surfaces of arms 142 and 143 are concave 142a, 143a,
respectively. First bearing surface 150 and second bearing surface
151 are planar. However, in an alternative embodiment, one or both
of bearing surfaces 150 and 151 could be configured as described
for implants 70, 80 or 100.
[0134] A central void 155 is bounded by inner wall 147 and is
continuous with opening 144 between arms 142 and 143. Thus, body
141 is a support component which can receive a growth component 153
in central void 155. In the illustrated embodiment, growth
component 153 can be a dowel of cancellous bone.
[0135] The implants described herein can be included in a kit
comprising a plurality of incrementally sized implants which can be
selected for use by the clinician based on the size needed for a
particular patient. In other embodiments, kits will be provided
which include instrumentation for performing an implant procedure
with or without a plurality of incrementally sized implants.
Further, surface preparation tools (e.g., rasps and cutting tools)
other than those specifically depicted herein can be used to
practice various aspects of the invention.
[0136] Having now described the present invention, it will be
apparent to one of ordinary skill in the art that many changes and
modifications can be made in the invention without departing from
the spirit or scope of the appended claims.
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