U.S. patent application number 09/788693 was filed with the patent office on 2001-10-18 for apparatus for fusing adjacent bone structures.
Invention is credited to Castro, Salvatore, McDonnell, Christopher.
Application Number | 20010032018 09/788693 |
Document ID | / |
Family ID | 25145277 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010032018 |
Kind Code |
A1 |
Castro, Salvatore ; et
al. |
October 18, 2001 |
Apparatus for fusing adjacent bone structures
Abstract
An apparatus for facilitating fusion of adjacent bony structures
includes an implant body dimensioned for positioning between
adjacent bone structures to maintain the bone structures in desired
spaced relation during interbody fusion. The implant body has an
outer wall and an external threaded configuration disposed on the
outer wall. At least one concave surface at least partially extends
along the implant body. The concave surface advantageously reduces
the transverse cross-sectional dimension of the implant member
thereby facilitating placement of the implant member in restricted
intervertebral areas. In addition, the concave surface enables
placement of a pair of implants in nested side-by-side relation.
Preferably, the threaded configuration has portions removed along
an arc section of the outer wall thereby defining a series of
generally longitudinally aligned concave surfaces in individual
turns thereof. A system and method for facilitating fusion of
adjacent vertebrae is also disclosed.
Inventors: |
Castro, Salvatore; (Milford,
MA) ; McDonnell, Christopher; (Sandy Hook,
CT) |
Correspondence
Address: |
Lawrence Cruz, Esq.
United States Surgical, a division of
TYCO HEALTHCARE GROUP LP
150 Glover Avenue
Norwalk
CT
06856
US
|
Family ID: |
25145277 |
Appl. No.: |
09/788693 |
Filed: |
February 20, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09788693 |
Feb 20, 2001 |
|
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|
09545320 |
Apr 7, 2000 |
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Current U.S.
Class: |
623/17.11 |
Current CPC
Class: |
A61F 2/446 20130101;
A61F 2002/30616 20130101; A61F 2002/30593 20130101; A61F 2310/00023
20130101; A61F 2/4611 20130101; A61F 2002/30787 20130101; A61F
2002/2835 20130101; A61F 2310/00017 20130101; A61F 2002/3085
20130101; A61F 2002/3082 20130101; A61F 2/442 20130101; A61F
2002/448 20130101; A61F 2002/30785 20130101; A61F 2310/00179
20130101; A61F 2002/30858 20130101; A61F 2/30744 20130101 |
Class at
Publication: |
623/17.11 |
International
Class: |
A61F 002/44 |
Claims
What is claimed is:
1. An apparatus for facilitating fusion of adjacent bony
structures, which comprises: an implant body dimensioned for
positioning between adjacent bone structures to maintain the bone
structures in desired spaced relation during interbody fusion, the
implant body defining a longitudinal axis and having an outer wall
extending along the longitudinal axis, the outer wall having an
external threaded configuration and at least one concave surface at
least partially extending along the longitudinal axis, wherein the
transverse cross-sectional dimension along a first transverse axis
inclusive of the concave surface is less than the transverse
cross-sectional dimension along a second transverse axis.
2. The apparatus according to claim 1 wherein the threaded
configuration has portions removed along an arc section of the
outer wall thereby defining a series of generally longitudinally
aligned concave surfaces in individual turns thereof.
3. The apparatus according to claim 1 wherein the one concave
surface extends substantially along the length of the implant
member.
4. The apparatus according to claim 1 wherein the implant body
includes an internal cavity defined within the outer wall for
accommodating bone growth inducing substances.
5. The apparatus according to claim 4 wherein the implant body
includes a plurality of apertures extending through the outer wall
in communication with the internal cavity.
6. The apparatus according to claim 5 wherein the apertures extend
through the valleys of the individual turns of the thread in
communication with the inner cavity to permit immediate contact of
the vertebral bone tissue and the bone growth inducing substances
within the inner cavity upon insertion of the implant body.
7. The apparatus according to claim 1 wherein the implant body
defines entry and trailing longitudinal end faces, at least one of
the end faces having an aperture therein in communication with the
internal cavity.
8. The apparatus according to claim 7 further including an end cap,
the end cap being mountable to the one end face to enclose the
internal cavity.
9. The apparatus according to claim 8 wherein each of the leading
and trailing end faces include an aperture extending to communicate
with the internal cavity.
10. The apparatus according to claim 9 including first and second
end caps mountable to respective leading and trailing end
faces.
11. The apparatus according to claim 2 including a second series of
generally longitudinally aligned concave surfaces.
12. The apparatus according to claim 11 wherein the second series
of concave surfaces are disposed in diametrical opposed relation to
the first mentioned series of concave surfaces.
13. The apparatus according to claim 1 wherein the implant body is
generally cylindrical.
14. The apparatus according to claim 1 wherein the implant body is
dimensioned and configured for positioning between adjacent
vertebrae and to support the vertebrae in adjacent spaced
relation.
15. A system for facilitating fusion of adjacent vertebrae, which
comprises: first and second implants dimensioned for positioning
between adjacent vertebrae to support the vertebrae in spaced
relation, the first implant including an implant body defining a
longitudinal axis and an outer wall extending along the
longitudinal axis, the outer wall having an external threaded
configuration and at least one substantially concave surface
portion at least partially extending along the longitudinal axis,
the second implant including an implant body defining a
longitudinal axis and having an arcuate outer wall portion
correspondingly dimensioned to be received within the concave
surface portion of the first implant to permit the first and second
implants to be positioned in nested side by side relation within an
intervertebral space defined between the adjacent vertebrae.
16. The apparatus according to claim 15 wherein the threaded
configuration of the first implant has portions removed along an
arc section of the outer wall thereby defining a series of
generally longitudinally aligned concave surfaces in individual
turns of the threaded configuration.
17. The apparatus according to claim 15 wherein the implant body of
the second implant has an external threaded configuration.
18. A method for fusion of adjacent vertebrae, comprising the steps
of: accessing the intervertebral space defined between adjacent
vertebrae; providing a first implant including an implant body
defining a longitudinal axis and an outer wall extending along the
longitudinal axis, the exterior wall having at least one
substantially concave surface portion at least partially extending
along the longitudinal axis; positioning the first implant within a
first lateral side of the intervertebral space; providing a second
implant including an implant body defining a longitudinal axis and
having an arcuate outer wall portion correspondingly dimensioned to
be received within the concave surface portion of the first
implant; and positioning the second implant within a second lateral
side of the intervertebral space and arranging the second implant
whereby the arcuate outer wall portion of the second implant is
received within the concave surface portion of the first
implant.
19. The method according to claim 18 wherein the exterior walls of
the first and second implants each have an external threaded
configuration and wherein the steps of positioning includes
rotating the respective implant bodies whereby the threaded
configurations engage the adjacent vertebrae.
20. The method according to claim 19 wherein the implant bodies of
the first and second implants each define an internal cavity for
reception of bone growth inducing substances and have apertures
extending through the exterior walls in communication with the
internal cavity, and further including the step of permitting bone
growth through the apertures to facilitate fusion of the adjacent
vertebrae.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation-in-Part application of
co-pending U.S. application Ser. No. 09/545,320 filed on Apr. 7,
2000.
BACKGROUND
[0002] 1. Technical Field
[0003] The present disclosure generally relates to a surgical
apparatus for fusing adjacent bone structures, and, more
particularly, to an apparatus and associated method for fusing
adjacent vertebrae.
[0004] 2. Background of the Related Art
[0005] The fusion of adjacent bone structures is commonly performed
to provide for long-term replacement to compensate for degenerative
or deteriorated disorders in bone. For example, an intervertebral
disc, which is a ligamentous cushion disposed between adjacent
vertebrae, may undergo deterioration as a result of injury,
disease, tumor or other disorders. The disk shrinks or flattens
leading to mechanical instability and painful disc
translocations.
[0006] Conventional procedure for disc surgery include partial or
total excision of the injured disc portion, e.g., discectomy, and
replacement of the excised disc with biologically acceptable plugs
or bone wedges. The plugs are driven between adjacent vertebrae to
maintain normal intervertebral spacing and to achieve, over a
period of time, bony fusion with the plug and opposed vertebrae.
More recently, emphasis has been placed on fusing bone structures
(i.e., adjoining vertebrae) with metallic or ceramic prosthetic
cage implants. One fusion cage implant is disclosed in commonly
assigned U.S. Pat. No. 5,026,373 to Ray et al., the contents of
which are incorporated herein by reference. The Ray '373 fusion
cage includes a cylindrical cage body having a thread formed as
part of its external surface and apertures extending through its
wall which communicate with an internal cavity of the cage body.
The fusion cage is inserted within a tapped bore or channel formed
in the intervertebral space thereby stabilizing the vertebrae and
maintaining a pre-defined intervertebral space. Preferably, a pair
of fusion cages are implanted within the intervertebral space. The
adjacent vertebral bone structures communicate through the
apertures and with bone growth inducing substances which are within
the internal cavity to unite and eventually form a solid fusion of
the adjacent vertebrae. FIGS. 1-2 illustrate the insertion of a
pair of the Ray '373 fusion cages positioned within an
intervertebral space.
SUMMARY OF THE INVENTION
[0007] Accordingly, the present invention is directed to further
improvements in spinal fusion procedures. In accordance with a
preferred embodiment, an apparatus for facilitating fusion of
adjacent bony structures includes an implant body dimensioned for
positioning between adjacent bone structures to maintain the bone
structures in desired spaced relation during interbody fusion. The
implant body has an outer wall and an external threaded
configuration disposed on the outer wall. At least one concave
surface at least partially extends along the implant body. The
concave surface advantageously reduces the transverse
cross-sectional dimension of the implant member thereby
facilitating placement of the implant member in restricted
intervertebral areas. In addition, the concave surface enables
placement of a pair of implants in nested side-by-side relation.
Preferably, the threaded configuration has portions removed along
an arc section of the outer wall thereby defining a series of
generally longitudinally aligned concave surfaces in individual
turns thereof. A system and method for facilitating fusion of
adjacent vertebrae is also disclosed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Preferred embodiment(s) of the present disclosure are
described herein with reference to the drawings wherein:
[0009] FIG. 1 is a view illustrating a portion of the vertebral
column of a patient;
[0010] FIG. 2 is a view taken along line 2-2 of FIG. 1 illustrating
a pair of prior art fusion implants positioned within the
intervertebral space for fusion of adjacent vertebrae;
[0011] FIG. 3 is a perspective view of the fusion implant apparatus
in accordance with the principles of the present disclosure;
[0012] FIG. 4 is a side plan view of the implant apparatus;
[0013] FIG. 5 is an axial view of the implant apparatus;
[0014] FIG. 6 is a side cross-sectional view of the implant
apparatus taken along the lines 6-6 of FIG. 5;
[0015] FIG. 7 is an axial cross-sectional view of the implant
apparatus taken along the lines 7-7 of FIG. 4;
[0016] FIG. 8 is a view illustrating details of the threaded
configuration of the implant apparatus;
[0017] FIG. 9 is a perspective view of an alternate embodiment of
the implant apparatus of FIG. 3:
[0018] FIG. 10 is an axial view of the implant apparatus of FIG.
9.
[0019] FIG. 11 is a perspective view of another alternate
embodiment of the implant apparatus of FIG. 3; and
[0020] FIGS. 12-14 are views illustrating a preferred sequence of
the implant apparatus within adjacent vertebrae.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0021] The preferred embodiment of the apparatus and method
disclosed herein are discussed in terms of orthopedic spinal fusion
procedures and instrumentation. It is envisioned, however, that the
disclosure is applicable to a wide variety of procedures including,
but, not limited to ligament repair, joint repair or replacement,
non-union fractures, facial reconstruction and spinal
stabilization. In addition, it is believed that the present method
and instrumentation finds application in both open and minimally
invasive procedures including endoscopic and arthroscopic
procedures wherein access to the surgical site is achieved through
a cannula or small incision.
[0022] The following discussion includes a description of the
fusion implant utilized in performing a spinal fusion followed by a
description of the preferred method for spinal fusion in accordance
with the present disclosure.
[0023] In the discussion which follows, the term "proximal", as is
traditional, will refer to the portion of the structure which is
closer to the operator while the term "distal" will refer to the
portion which is further from the operator.
[0024] Referring now to the drawings in which like reference
numerals identify similar or identical elements throughout the
several views, FIG. 3 illustrates, in perspective, the fusion
implant apparatus of the present disclosure. Fusion implant 100 is
intended to be inserted within a preformed bore in adjacent bone
structures, e.g., adjacent vertebrae, with the bore spanning the
intervertebral space and penetrating the vertebral end plates.
[0025] Fusion implant 100 includes elongated implant body 102 which
is preferably fabricated from a suitable biocompatible rigid
material such as titanium and/or alloys of titanium, stainless
steel, ceramic materials or rigid polymeric materials. Implant body
102 is preferably sufficient in strength to at least partially
replace the supporting function of an intervertebral disc, i.e., to
maintain adjacent vertebrae in desired spaced relation, during
healing and fusion.
[0026] With reference to FIGS. 3-7, implant body 102 includes
exterior or outer wall 104 concentrically arranged about
longitudinal axis "a" of the implant body 102 and inner cavity 106
within the exterior wall 104. Implant body 102 is preferably
substantially cylindrical in configuration defining a constant
diameter along its length. Inner cavity 106 is intended to
accommodate bone growth inducing substances such as bone chips
taken from allograft or autograft, etc. . . . which facilitate the
fusion process. Implant body 102 is preferably provided in various
lengths ranging from about 18 mm-24 mm and in corresponding various
diameters ranging from about 14 mm-18 mm. Other dimensions are also
contemplated and may vary depending on the intended use of the
implant in the cervical, thoracic or lumbar regions of the
spine.
[0027] Outer wall 104 has an external threaded configuration 108
formed thereon. External threaded configuration 108 includes a
uniform helical thread 110 which assists in advancing implant body
102 into a preformed channel provided in the adjacent vertebrae. In
the preferred embodiment, thread 110 cooperates with an internally
threaded bore within the adjacent vertebrae to advance implant body
102 within the threaded bore. Alternatively, thread 110 may be a
self-tapping cutting thread, i.e., the thread is capable of
deburring bone material during advancement into the performed
channel thereby precluding the requirement of tapping the internal
bore in the vertebrae.
[0028] A plurality of apertures 112 extend through outer wall 104
of implant body 102. Apertures 112 are preferably formed by
broaching grooves in the internal surface of the internal cavity
108. The effect of such broaching is to remove material from the
valleys between the individual turn of the thread 110, thus
defining the apertures 112. The advantages of such an arrangement
are disclosed in U.S. Pat. No. 4,961,740, the contents of which are
incorporated herein by reference, and include immediate bone to
bone contact between the vertebral bodies or bone structures and
the bone inducing substances packed within the internal cavity 108
of the implant body 102. Apertures 112 are preferably substantially
the same in dimension although it is envisioned that the dimensions
of the apertures may vary to provide for more or less bone to bone
contact as desired.
[0029] As best depicted in FIGS. 4 and 7, apertures 112 are
clustered about a transverse axis "t1", both at the upper and lower
end of the axis. Consequently, apertures 112 come into contact with
the upper and lower vertebral bone structures to encourage bone
growth through implant body 102 from the vertebral bone structures
when appropriately positioned within the vertebrae. The lateral
sections of implant body 102 formed along transverse axis "t2" do
not have apertures in order to prevent growth of disk material
which might interfere with the bone fusion process.
[0030] Outer wall 104 has a plurality of independent arcuate
surfaces 114 defined in the outer wall and extending along the
length of implant body 102. The arcuate surfaces 114 are preferably
concave in configuration and may be formed by grinding, blasting
applications, etc. Preferably, concave surfaces 114 extend radially
inwardly within each thread turn without penetrating or extending
into the outer wall surface thereby defining removed portions of
the thread as shown.
[0031] The concave surface arrangement provides two specific
advantages. First, such arrangement increases the pull out or
expulsion force necessary to remove the implant from the adjacent
vertebrae. Secondly, the concave surface arrangement permits a pair
of implants to be positioned in side by side relation within the
adjacent vertebrae in a nested contacting relation. Moreover, the
concave surface arrangement provides a reduced cross-sectional
dimension along second transverse axis "t2" relative to the
cross-sectional dimension along first transverse axis "t1" thereby
facilitating placement of the implant body 102 within restricted
vertebral locations.
[0032] Implant body 102 defines entry and trailing end faces 116,
118. End faces 116, 118 are preferably open, i.e, having apertures
120, 122 therein in communication with the inner cavity 106. As
best depicted in FIG. 6, implant body 102 has internal annular
recesses 124 adjacent each end face 116, 118. Annular recesses 124
are intended to receive plastic end caps 126 (FIG. 3) which are
received within the recesses in snap-fit relation therewith to
enclose internal cavity 108 thereby retaining the bone growth
inducing substances therein. Implant body 102 further includes tool
receiving structure in the form of longitudinal extending internal
rails 128 extending the length of the implant body 102 in
diametrically opposed relation. Rails 128 receive correspondingly
dimensioned prongs of an insertion instrument such that the
insertion instrument may be rotated to cause corresponding rotation
and entry of implant body 102 into the intervertebral space.
[0033] Alternate Embodiment(s)
[0034] FIGS. 9-10 illustrate an alternate embodiment of the implant
apparatus of FIG. 3. This implant apparatus is substantially
similar to the apparatus disclosed in FIG. 3, but, however
incorporates a second series of concave surfaces 114 disposed in
diametrically opposed relation to the first series. The second
series provides flexibility to the user in terms of placement of
the implant within the desired orientation within the
intervertebral disc space. The second series also significantly
reduces the cross-sectional dimension of the implant body along the
second transverse axis "t2".
[0035] FIG. 11 illustrates an alternate embodiment of the implant
apparatus of FIG. 3 where the concave surface extends through
threaded configuration 110 and into exterior wall 104 thereby
defining a single concave surface 114' which extends along the
length of implant body 102.
[0036] Insertion of Fusion Implant
[0037] The insertion of the fusion implant 100 into an
intervertebral space defined between adjacent lumbar vertebrae will
now be described. The subsequent description will be particularly
discussed in conjunction with an open posterior approach for spinal
fusion implant insertion. However, it is to be appreciated that
other approaches, e.g., anterior, lateral, posterior lateral,
anterior lateral etc. . . . could be utilized. Laparoscopic
approaches are also envisioned.
[0038] Initially, a first lateral side of the intervertebral space
"i" is accessed utilizing appropriate retractors to expose the
posterior vertebral surface. A drilling instrument is selected to
prepare the disc space and vertebral end plates for insertion of
the fusion implant. The cutting depth of drilling instrument may be
adjusted as desired. The drilling instrument is advanced into the
intervertebral space adjacent to the first lateral side to shear
the soft tissue and cut the bone of the adjacent vertebrae thereby
forming a bore which extends into the adjacent vertebrae adjacent
the first lateral side as depicted in FIG. 12. With the first bore
"b1" drilled in the first lateral side, attention is directed to
forming the bore in the second lateral side. With continued
reference to FIG. 12, the second lateral side is accessed and the
center entry point for the drill is identified. Preferably, the
drill is positioned such that the second bore "b2" will overlap the
first bore "b1". The drill is activated to form the second bore.
The first and second bores "b1, b2" may be tapped with a
conventional tap instrument if desired.
[0039] With reference to FIG. 13, a first implant 100 is packed
with bone growth inducing substances as is conventional in the art.
The fusion implant 100 may then be mounted on an insertion
instrument (not shown) and advanced within the intervertebral space
by rotating the implant 100 whereby threaded configuration 110 of
the implant body 102 cooperates with the threaded bore to advance
within the intervertebral space "i". Preferably, the implant 100 is
arranged such that concave surface generally extends along the axis
"s" of the spine and faces the midline of the intervertebral space.
If the implant of FIGS. 9-10 is utilized, the second series of
concave surfaces facilitates placement of the implant 100 with the
concave surface arrangement adjacent to the midline of the
intervertebral space, i.e., when positioned, the implant need only
be rotated a maximum of 90.degree. in either direction to place the
concave surface arrangement adjacent the midline. With the first
implant positioned within the intervertebral space, a second
implant "x" is implanted within the second threaded bore in the
same manner. The second implant "x" is preferably a conventional
cylindrical implant such as the implant disclosed in the Ray '373
patent. As appreciated, although the second bore overlaps the first
bore, the clearance provided by the concave surface arrangement of
the first implant 100 permits the second implant "x" to be advanced
within the intervertebral space without interference. The second
implant "x" is arranged such that the outer convex surface is
received within the concave surface area of the first implant in
nested side-by-side relation as shown. Thus, the concave surface
arrangement permits two implants 100, "x" to be placed in nested
side-by-side arrangement. The concave surface arrangement also
reduces the effective cross-sectional dimension of implant 100
thereby facilitating placement of the implants in a restricted
vertebral location.
[0040] With reference to FIG. 14, it is appreciated that the second
implant may be identical to implant 100. When positioned within the
adjacent vertebrae, the concave surface area may be facing the
midline of the intervertebral space or alternatively adjacent the
outer portion of the space as shown in phantom.
[0041] Implants 100 form struts across the intervertebral space "i"
to maintain the adjacent vertebrae "V.sub.1, V.sub.2" in
appropriate spaced relation during the fusion process. Over a
period of time, the adjacent vertebral tissue communicates through
apertures 112 within implants 100 to form a solid fusion.
Desirably, lateral vertebral tissue growth into the implant 100 is
restricted due to the concave surface areas of the implant being
devoid of apertures. Such lateral growth would inhibit the fusion
process and potentially restrict subsequent spinal mobility.
[0042] While the above description contains many specifics, these
specifics should not be construed as limitations on the scope of
the disclosure, but merely as exemplifications of preferred
embodiments thereof. For example, the fusion implant 100 could also
be used for thoracic and cervical vertebrae. Those skilled in the
art will envision many other possible variations that are within
the scope and spirit of the disclosure as defined by the claims
appended hereto.
* * * * *