U.S. patent application number 09/754038 was filed with the patent office on 2001-10-18 for intervertebral implants.
Invention is credited to Alfaro, Arthur A., Boyle, John W., Martz, Erik O., Morris, John W., Rosenthal, Daniel E., Russell, James, Shimp, Lawrence A..
Application Number | 20010032017 09/754038 |
Document ID | / |
Family ID | 22634287 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010032017 |
Kind Code |
A1 |
Alfaro, Arthur A. ; et
al. |
October 18, 2001 |
Intervertebral implants
Abstract
A multipart intervertebral implant is provided which includes an
implant portion and an implant extender portion. The implant
portion and the implant extender portion can be fastened together
using any known fastening means including pins, interlocking
structure (e.g., dovetail, tongue and groove, etc.), adhesives,
etc. The size of the implant extender portion can be selected
during a surgical procedure to provide an implant suitable for a
particular intervertebral receiving bed. An intervertebral implant
is also provided which may be formed from a multiplicity of implant
sections which are fastened together to provide an implant having a
desired length. Implants having surface configurations which more
closely correspond to the configuration of vertebral endplates are
also provided.
Inventors: |
Alfaro, Arthur A.; (Colts
Neck, NJ) ; Shimp, Lawrence A.; (Morganville, NJ)
; Russell, James; (Little Silver, NJ) ; Boyle,
John W.; (Upper Montclair, NJ) ; Martz, Erik O.;
(Howell1, NJ) ; Rosenthal, Daniel E.; (Millburn,
NJ) ; Morris, John W.; (Beachwood, NJ) |
Correspondence
Address: |
Christopher G. Trainor
Dilworth & Barrese
333 Earle Ovington Blvd.
Uniondale
NY
11553
US
|
Family ID: |
22634287 |
Appl. No.: |
09/754038 |
Filed: |
January 2, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60173973 |
Dec 30, 1999 |
|
|
|
Current U.S.
Class: |
623/17.11 |
Current CPC
Class: |
A61F 2002/30156
20130101; A61F 2002/30599 20130101; A61F 2002/30207 20130101; A61F
2002/30492 20130101; A61F 2002/3085 20130101; A61F 2002/30827
20130101; A61F 2002/2835 20130101; A61F 2002/30459 20130101; A61F
2002/30289 20130101; A61F 2230/0067 20130101; A61F 2230/0006
20130101; A61F 2230/0023 20130101; A61F 2002/30789 20130101; A61F
2002/30387 20130101; A61F 2002/30772 20130101; A61F 2310/00179
20130101; A61F 2220/0025 20130101; A61F 2220/0066 20130101; A61F
2002/30593 20130101; A61F 2002/30324 20130101; A61F 2002/30291
20130101; A61F 2002/30873 20130101; A61F 2230/0004 20130101; A61F
2002/30118 20130101; A61F 2310/00131 20130101; A61F 2/28 20130101;
A61F 2/4611 20130101; A61F 2250/0063 20130101; A61F 2002/30112
20130101; A61F 2310/00359 20130101; A61F 2002/2839 20130101; A61F
2002/3023 20130101; A61F 2230/0091 20130101; A61F 2002/30233
20130101; A61F 2/4455 20130101; A61F 2/442 20130101; A61F 2230/0069
20130101; A61F 2002/2817 20130101; A61F 2/30965 20130101; A61F
2002/30604 20130101; A61F 2250/0036 20130101 |
Class at
Publication: |
623/17.11 |
International
Class: |
A61F 002/44 |
Claims
1. An intervertebral implant comprising: a first implant portion
having a first end and a second end, the second end having engaging
structure formed therein; a second implant portion having a first
end and a second end, the first end of the second implant portion
including engaging structure formed thereon, the engaging structure
formed on the first end of the second implant portion being
configured to mate with the engaging structure formed on the second
end of the first implant portion to fasten the second implant
portion to the first implant portion.
2. An intervertebral implant according to claim 1, wherein one of
the first and second engaging structures includes a dovetail
connector.
3. An intervertebral implant according to claim 1, wherein the
first and second implant portions are cylindrical.
4. An intervertebral implant according to claim 1, wherein the
first and second implant portions are wedge-shaped.
5. An intervertebral implant according to claim 1, further
including at least one pin extending between the first and second
implant portions.
6. An intervertebral implant according to claim 2, wherein the
other of the first and second engaging structures includes a slot
configured to receive the dovetail connector.
7. An intervertebral implant according to claim 1 farther including
a third implant portion having first and second ends and third
engaging structure.
Description
[0001] This application claims priority from United States
provisional application Ser. No. 60/173,973, filed Dec. 30, 1999,
which is incorporated herein by reference.
BACKGROUND
[0002] 1. Technical Field
[0003] The present disclosure relates generally to biocompatible
implants and, more particularly, to intervertebral implants
suitable for implantation into the lumbar, thoracic and/or cervical
regions of the spine during a spinal fusion procedure.
[0004] 2. Background of Related Art
[0005] Intervertebral implants for fusing together adjacent
vertebrae of a spinal column are well known in the art. Such
implants are formed in a variety of different shapes and sizes and
are configured for insertion into receiving beds formed in the
lumbar, thoracic and cervical regions of the spine. The implants
may be formed from a variety of different biologically compatible
materials including ceramics, polymers, human or animal bone,
composites, etc. The implants may also be shaped to maintain the
natural lordoses of the spine or to prevent the implant from
backing out of an intervertebral receiving bed in which it will be
implanted.
[0006] Examples of known implants are disclosed in U.S. Pat. No.
4,877,020 to Vich and U.S. Pat. No. 4,878,915 to Brantigan. Vich
and Brantigan each disclose cylindrical implants having an outer
helical thread formed thereabout. The Vich implant is formed from
autogenic bone taken from the iliac crest of a patient. The
Brantigan implant is formed of an inert metal such as stainless
steel, cobalt-chromium-molybdenum alloys and titanium.
[0007] One problem associated with known implants is the difficulty
in adapting an implant to meet the size requirements of a
particular intervertebral receiving bed. For example, because
anatomically all patients are different, the specific size of
implant required for a surgical procedure will not be known to any
certainty until a surgeon has prepared the intervertebral space for
implantation. Thus, a surgeon must keep a variety of different size
implants available for use or have means to alter the dimensions of
the implant at his disposal.
[0008] Another problem associated with known implants constructed
from bone is that the anatomical limitations of donor bone limit
the size of the implant which can be formed from bone. As a result,
bone having satisfactory strength characteristics may not be
available for use as an implant because of size limitations
[0009] Finally, yet another problem associated with known implants
is their inability to accurately maintain the natural lordoses of
the spine. Because of the irregular shape of the vertebral
endplates, wedge-shaped implants and cylindrical dowels are
incapable of supporting adjacent vertebrae in their natural
orientation without substantially altering the shape of the
vertebral endplate(s).
[0010] Accordingly, a continuing need exists for an intervertebral
implant whose size may be easily altered by a surgeon during a
surgical procedure to meet the size requirements of a particular
implant receiving bed and for an implant capable of maintaining the
natural lordoses of the spine without substantially altering the
shape of the vertebral endplates.
SUMMARY
[0011] In accordance with the present disclosure, intervertebral
implants are provided which more precisely correspond in shape to
the shape of the vertebral endplates. In one preferred embodiment,
an implant is formed from a ring of material having a top surface
and a bottom surface. The top and/or bottom surfaces of the implant
include a series of annular stepped surfaces which together define
a convex configuration which closely corresponds to the concave
shape of the vertebral endplates. In an alternate embodiment, the
annular stepped surfaces on the top and/or bottom surfaces of the
implant can be replaced by a single helical pathway.
[0012] In another preferred embodiment, a multipart intervertebral
implant is provided which includes an implant portion and an
implant extender portion. The implant portion and the implant
extender portion can be fastened together using any known fastening
means including pins, interlocking structure (e.g., dovetail,
tongue and groove, etc.), adhesives, etc. The size of the implant
extender portion can be selected during a surgical procedure to
provide an implant suitable for a particular intervertebral
receiving bed.
[0013] In yet another preferred embodiment, an intervertebral
implant may be formed from a multiplicity of implant sections which
are fastened together to provide an implant having a desired
length. These implant sections and the implants described above can
be formed of any biocompatible material including bone.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Preferred embodiments of the presently disclosed
intervertebral implants are described herein with reference to the
drawings, wherein:
[0015] FIG. 1 is a perspective view of one preferred embodiment of
the presently disclosed intervertebral implant;
[0016] FIG. 2 is a top view of the intervertebral implant shown in
FIG. 1;
[0017] FIG. 3 is a side view from a first side of the
intervertebral implant shown in FIG. 1;
[0018] FIG. 4 is a top perspective view of the intervertebral
implant shown in FIG. 1;
[0019] FIG. 5 is a side view from the other side of the
intervertebral implant shown in FIG. 1;
[0020] FIG. 6 is a perspective view of another preferred embodiment
of the presently disclosed intervertebral implant;
[0021] FIG. 6A is a perspective view of another preferred
embodiment of the presently disclosed intervertebral implant;
[0022] FIG. 7 is a top view of the intervertebral implant shown in
FIG. 6;
[0023] FIG. 8 is a side view of the intervertebral implant shown in
FIG. 6;
[0024] FIG. 9 is a top perspective view of the intervertebral
implant shown in FIG. 6;
[0025] FIG. 10 is another side view of the intervertebral implant
shown in FIG. 6;
[0026] FIG. 11 is an elevational view of the intervertebral implant
shown in FIG. 6 positioned between adjacent vertebrae;
[0027] FIG. 12 is a perspective view of another embodiment of the
presently disclosed intervertebral implant;
[0028] FIG. 13 is a side view of the intervertebral implant shown
in FIG. 12;
[0029] FIG. 14 is a top view of the intervertebral implant shown in
FIG. 12;
[0030] FIG. 15 is a rear end view of the intervertebral implant
shown in FIG. 12;
[0031] FIG. 16 is a perspective view of yet another embodiment of
the presently disclosed intervertebral implant;
[0032] FIG. 17 is a side view of the intervertebral implant shown
in FIG. 16;
[0033] FIG. 18 is a top view of the intervertebral implant shown in
FIG. 16;
[0034] FIG. 19 is a rear end view of the intervertebral implant
shown in FIG. 16;
[0035] FIG. 20 is a perspective view of yet another embodiment of
the presently disclosed intervertebral implant.
[0036] FIG. 21 is a side view of the intervertebral implant shown
in FIG. 20;
[0037] FIG. 22 is a top view of the intervertebral implant shown in
FIG. 20;
[0038] FIG. 23 is a rear end view of the intervertebral implant
shown in FIG. 20;
[0039] FIG. 24 is a top view of yet another embodiment of the
presently disclosed intervertebral implant;
[0040] FIG. 25 is yet another embodiment of the presently disclosed
intervertebral implant;
[0041] FIG. 26 is a side view of the intervertebral implant shown
in FIG. 25 positioned between adjacent vertebrae;
[0042] FIG. 27 is a side view of the presently disclosed
intervertebral implant and implant extender positioned between
adjacent vertebrae with the implant extender positioned adjacent
the leading end of the intervertebral implant;
[0043] FIG. 28 is a side view of the intervertebral implant and
implant extender shown in FIG. 27 positioned between adjacent
vertebrae with the implant extender positioned adjacent the
trailing end of the intervertebral implant;
[0044] FIG. 29 is a side view of an alternate embodiment of the
presently disclosed intervertebral implant and implant extender in
an interlocked configuration;
[0045] FIG. 30 is a side view of the intervertebral implant and
implant extender shown in FIG. 29 in a partially assembled
configuration; and
[0046] FIG. 31 is a perspective view of yet another embodiment of
the presently disclosed intervertebral implant.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS,
[0047] Preferred embodiments of the presently disclosed
intervertebral implant and implant extender will now be described
in detail with reference to the drawings in which like reference
numerals designate identical or corresponding elements in each of
the several views.
[0048] FIGS. 1-5 illustrate a preferred embodiment of the presently
disclosed intervertebral implant shown generally as 10. Briefly,
implant 10 includes an upper surface 12, a lower surface 14 and a
sidewall 15 positioned between the upper and lower surfaces. Upper
and lower surfaces 12 and 14 each include a series of circular
steps 16 which move upwardly from the outer periphery 18 of implant
10 to the center 20 of implant 10. Alternately, steps 16 need not
be centered about the center of implant 10 nor do adjacent steps
need be of the same height. A throughbore 22 extends between upper
and lower surfaces 12 and 14 of implant 10. Throughbore 22 is
dimensioned to receive growth factors including autograft,
allograft, DBM, etc . . . , to stimulate bone growth.
[0049] FIGS. 6-10 also illustrate an implant 100 having stepped
upper and lower surfaces 112 and 114. In contrast to the implant
shown in FIGS. 1-5, implant 100 includes a greater number of steps
116 which define a more gradual taper than steps 16 of implant 10.
It is envisioned that any number of steps may be provided on the
upper and/or lower surfaces of the implant to provide any desired
surface curvature. For example, each stop may have a height of from
about 0.15 mm to about 3 mm. Other step dimensions are also
envisioned.
[0050] FIG. 6A illustrates another alternate embodiment of the
stepped implant shown in FIGS. 1-5 shown generally as 100'. Implant
100' includes a helical pathway 116' which extends from the outer
periphery 118' of implant 100' towards the center of implant 100'.
As discussed above, the helical pathway need not be centered about
the central axis of implant 100' but rather it may be oriented to
provide the desired curvature on the upper and/or lower surface of
implant 100'. Moreover, the height of the step defined by the
helical pathway 116' may vary along the length of pathway 116'.
[0051] Implants 10, 100 and 100' may be formed from a variety of
different biologically compatible materials including ceramics,
polymers, human or animal bone, carbon fiber tantalum composites,
etc. using a variety of known processes including molding, casting,
machining, etc. Preferably, implant 10 is formed from cadaveric
human or animal bone by making a transverse cut through the
diaphysis or metaphysis of a long bone, e.g., tibia, fibula, femur,
ulna, radius, etc., to form a ring and thereafter machining the
upper and/or lower surfaces of the implant, e.g., milling the
stepped or helical configuration into the upper and lower surfaces
of the ring. Alternately, only one of the upper and lower surfaces
of the ring may be provided with a stepped configuration.
[0052] The bone used to form implants 10, 100 and 100' may be
partially or fully demineralized bone. Preferably the bone is
surface demineralized. By surface demineralizing the bone, the
osteoconductivity and the conformability of the outer surfaces of
the implant are improved while the strength of the inner portion of
the implant is retained.
[0053] Referring to FIG. 11, implants 10, 100 and 100' may be
positioned within a receiving bed formed between adjacent vertebrae
32 and 34. Because the upper and lower surfaces of the implants
conform to the natural concavity of the vertebral endplates, only
minimal preparation of the vertebrae is required by a surgeon prior
to insertion of an implant to maintain the natural lordoses of the
spine.
[0054] FIGS. 12-15 illustrate an alternate embodiment of the
intervertebral implant shown generally as 200. Intervertebral
implant 200 is preferably formed from a cortical ring allograft cut
from the diaphysis or metaphysis of a long bone but may be formed
from any biocompatible material having the requisite strength
requirements. Implant 200 includes a tapered, ring-shaped body 212
having flat top and bottom surfaces 214 and 216, respectively.
Anterior end 218 of implant 200 has a height which is greater than
the height of posterior end 220. The taper of the implant should be
such as to conform to the vertebral end plates of adjacent
vertebrae. Mating structure 222 for engaging corresponding
structure of an insertion tool is formed in a sidewall 224 of
implant 200 in the anterior end 218 of implant 200. A plurality of
concentric rings 226 are formed in top and bottom surfaces 214 and
216. Rings 226 are preferably V-shaped, although other
configurations are also envisioned, i.e., U-shaped, rectangular,
etc. A throughbore 228 extends between top and bottom surfaces 214
and 216 of implant 200. If implant 200 is formed from bone,
throughbore 228 may be defined by the intramedullary canal of the
bone from which implant 200 is cut. Implant 200 is configured for
anterior insertion into the intervertebral space. Growth factors
including autograft, allograft, and demineralized bone particles
may be positioned in throughbore 228 and/or rings 226 to stimulate
bone growth.
[0055] FIGS. 16-19 illustrate an alternate embodiment of implant
200 shown generally as 300. Implant 300 is similar to implant 200
but includes convex top and bottom surfaces 314 and 316 which are
configured to engage the vertebral end plates of adjacent
vertebrae. Top and bottom surfaces 314 and 316 also include
concentric rings 326 similar to those described above with respect
to implant 200.
[0056] FIGS. 20-23 illustrate another alternate embodiment of
implant 200 shown generally as 400. Implant 400 is similar to
implant 200 except that anterior end 418 is approximately equal to
the height of posterior end 420.
[0057] FIG. 24 illustrates a partially threaded stepped implant
shown generally as 500. Implant 500 is preferably formed from
cortical bone by making a transverse cut through the diaphysis or
metaphysis of a long bone to obtain a cylindrical bone plug and
thereafter machining and threading the bone plug. Alternately,
implant 500 may be formed from any biocompatible material having
the requisite strength requirements using any known process
including machining, molding, etc. Implant 500 includes a
cylindrical body 510 having a first end portion 512 having a first
outer diameter and a second end portion 513 having a second outer
diameter larger than the first diameter. A variety of different
diameter implants are envisioned. A throughbore 514 extends through
first end portion 512 of cylindrical body 510. First end portion
512 has screw threads 516 at one end thereof, but does not include
threads in the area about throughbore 514. Second end portion 513
includes screw threads 518. When implant 500 is formed by cutting a
bone plug from a long bone, the absence of screw threads in the
area of throughbore 514 facilitates the use of long bones having a
thinner wall section, i.e., the bone wall between the
intramedullary canal of a long bone and the outer surface of the
bone plug cut therefrom can be thinner.
[0058] When implant 500 is inserted into intervertebral space
between adjacent vertebrae, second end portion 513 will sit in the
vertebral wall and provide the majority of the retaining force.
First end portion 512 will also screw into adjacent endplates but
thread engagement may be minimal, especially if the intervertebral
space is very concave. A stepped reamer and tap can be used to
prepare the intervertebral space.
[0059] FIGS. 25 and 26 illustrate an alternate embodiment of
implant 500 shown generally as 600. Implant 600 is similar to
implant 500 except that second end 613 of implant 600 is tapered
from one end to the other. Implant 600 may be used to vary the
spine geometry. Referring to FIG. 26, during insertion of implant
600 into the intervertebral space, implant 600 will directly force
adjacent vertebral surfaces 630 and 632 apart. The particular taper
of second end portion 613 of implant 600 can be chosen to provide
the desired spacing of the adjacent vertebrae.
[0060] Intervertebral implants in the form of threaded, cylindrical
dowels formed of bone, specifically, human or animal cadaveric
bone, are well known in the surgical arts. Typically, such implants
are formed by making a transverse cut through the diaphysis or
metaphysis of a long bone, i.e., the femur, tibia, fibula, ulna or
radius, using a cylindrical drill bit. One problem associated with
forming and using bone dowel implants is that anatomical
limitations make it difficult to recover bone dowels having the
desired length needed for intervertebral fusion procedures. This is
especially true when performing procedures in the cervical region
of the spine wherein small diameter dowels are required.
[0061] In order to compensate for anatomical limitations, a dowel
extender portion may be provided. Referring to FIGS. 27 and 28, a
cylindrical dowel extender 710 may be implanted within the
intervertebral space prior to implantation of the main dowel
portion D (FIG. 27), or alternately, after implantation of main
dowel portion D (FIG. 28). Preferably, dowel extender portion 710
includes helical threads 712 to engage vertebral end plates 714 and
716 and retain the dowel extender portion in place. However,
non-threaded dowel extender portions are also envisioned. Each
dowel extender portion 710 preferably includes engagement
structure, such as slot 718, for engaging an insertion tool (not
shown).
[0062] Generally, dowel extenders having a length of from about 4
to 8 mm are needed to supplement the main dowel, although other
length dowel extenders may also be needed depending upon the
particular surgical procedure being performed. A common thread
pattern associated with intervertebral dowels is 10 threads per
inch. Thus, a dowel extender having a length of 4 mm will only have
about 1.57 threads and a dowel extender having a length of 6 mm
will have only about 2.35 threads. Because of the limited number of
threads and the short thread engagement length, it may be difficult
to stabilize a dowel extender in the intervertebral space and
problems may result. For example, if the dowel extender is not
firmly seated in the intervertebral space between adjoining
vertebrae when contacted by the main dowel, it may tip over.
[0063] In order to provide greater stability, an alternate
embodiment of the presently disclosed dowel extender is described
herein. Referring to FIGS. 29 and 30, dowel extender 800 includes a
cylindrical body 810 having a first end 812 and a second end 814.
Second end 814 includes a projection 816 configured and dimensioned
to be received within a correspondingly shaped slot formed on one
end of main dowel D. Although illustrated as having a dove-tail
configuration, projection 816 may assume other configurations
capable of interlocking with a correspondingly shaped slot.
Referring to FIG. 29, locking pins 820 may be provided to further
secure dowel extender portion 800 to main dowel portion D.
Alternately, a locking pin or pins may be used to entirely replace
projection 816 and secure dowel extender 800 to main dowel D.
[0064] In an alternate embodiment, a bone dowel is constructed from
multiple dowel segments which are secured together using
interlocking structure. The interlocking structure may be formed
integrally with each dowel segment, e.g., each dowel segment may
have a slotted front end and a correspondingly shaped projection
formed at a rear end. Each dowel segment has a predetermined length
and is joined to one or more other dowel segments to form a dowel
having a desired length. For example, dowel segments may be formed
having lengths of 2, 4 and 6 mm. In order to form a dowel having a
length of 20 mm, three 6 mm dowel segments and a 2 mm dowel segment
can be joined together. The dowel segments are preferably formed
from bone, although other biocompatible materials listed above are
also envisioned. The dowel segments may be cylindrical,
rectangular, wedge-shaped, etc. For example, FIG. 31 illustrates a
wedge shaped intervertebral implant 900 formed of multiple implant
segments 910 which are fastened together in the manner described
above.
[0065] It will be understood that various modifications may be made
to the embodiments disclosed herein. For example, the configuration
of the sidewall of any of the implants described above may be
modified to better suit a particular procedure, i.e., the sidewalls
can be formed to be rectangular, circular, triangular,
semi-circular, etc. Moreover, the implants described above,
although disclosed in the context of spinal implantation, may be
suitable for other implantation procedures not specifically listed
here but obvious to those of ordinary skill in the art. Therefore,
the above description should not be construed as limiting, but
merely as exemplifications of preferred embodiments. Those skilled
in the art will envision other modifications within the scope and
spirit of the claims appended hereto.
* * * * *