U.S. patent application number 10/055673 was filed with the patent office on 2002-05-30 for intervertebral spacing implant system.
This patent application is currently assigned to Ortho Development Corporation. Invention is credited to Ogilvie, James A., Varga, Peter Pal.
Application Number | 20020065560 10/055673 |
Document ID | / |
Family ID | 24369156 |
Filed Date | 2002-05-30 |
United States Patent
Application |
20020065560 |
Kind Code |
A1 |
Varga, Peter Pal ; et
al. |
May 30, 2002 |
Intervertebral spacing implant system
Abstract
An intervertebral spacer adapted for implanting between adjacent
vertebral bodies of a human spine as a load-bearing replacement for
a spinal disc. The spacing member includes an external, non-porous,
concavo-convex contour with respect to one dimension of said
spacing member. The spacing member is preferably constructed from a
rigid, non-resilient load-bearing material that is incapable of
elastic deformation. The spacing member is inserted with the aid of
a sheathed trocar device that is releasably attached to the spacer,
to enable implantation and selective positioning of the spacer by
the surgeon from the posterior side of the spine, without the need
to retract the dural nerve or the posterior longitudinal
ligament.
Inventors: |
Varga, Peter Pal; (Budapest,
HU) ; Ogilvie, James A.; (Edina, MN) |
Correspondence
Address: |
KARL R CANNON
PO BOX 1909
SANDY
UT
84091
US
|
Assignee: |
Ortho Development
Corporation
|
Family ID: |
24369156 |
Appl. No.: |
10/055673 |
Filed: |
January 22, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10055673 |
Jan 22, 2002 |
|
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|
09592072 |
Jun 12, 2000 |
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Current U.S.
Class: |
623/17.16 ;
623/17.11 |
Current CPC
Class: |
A61F 2/4611 20130101;
A61F 2/4465 20130101; A61F 2002/30133 20130101; A61F 2310/00179
20130101; A61F 2/28 20130101; A61F 2002/4627 20130101; A61F
2002/2835 20130101; A61F 2/442 20130101; A61F 2002/30774 20130101;
A61F 2230/0015 20130101; A61F 2310/00023 20130101; A61F 2002/30828
20130101; A61F 2/4684 20130101; Y10S 623/908 20130101 |
Class at
Publication: |
623/17.16 ;
623/17.11 |
International
Class: |
A61F 002/44 |
Claims
What is claimed is:
1. An intervertebral spacing implant comprising: a spacing member
adapted for implanting between adjacent vertebral bodies of a human
spine as a load-bearing replacement for a spinal disc, said spacing
member further comprising an external, non-porous, concavo-convex
contour with respect to one dimension of said spacing member.
2. The intervertebral spacing implant of claim 1, wherein the
spacing member is constructed from a rigid, non-resilient
load-bearing material that is incapable of elastic deformation.
3. The intervertebral spacing implant of claim 2, wherein the
spacing member comprises metal.
4. The intervertebral spacing implant of claim 3, wherein the
spacing member comprises titanium.
5. The intervertebral spacing implant of claim 2, wherein the
spacing member comprises ceramic.
6. The intervertebral spacing implant of claim 1, wherein the
spacing member includes an anterior wall and a posterior wall, and
wherein the external concavo-convex contour of the spacer is
defined by the posterior wall being concave in a horizontal
dimension and by the anterior wall being convex in a horizontal
dimension.
7. The intervertebral spacing implant of claim 6, wherein the
anterior wall and the posterior wall of the spacing member are each
linear in a vertical dimension.
8. The intervertebral spacing implant of claim 7, wherein the
concavo-convex contour comprises a concave posterior side, and a
convex anterior side disposed in a substantial parallel orientation
with respect to the concave posterior side.
9. The intervertebral spacing implant of claim 1, wherein the
spacing member defines an imaginary arcuate centerline residing
between opposing sides of the external concavo-convex contour of
said spacing member to thereby enable said spacing member to be
inserted thorough an incision along an arcuate insertion path.
10. The intervertebral spacing implant of claim 9, wherein the
spacing member is configured and adapted to be inserted along said
arcuate movement path in a manner such that said arcuate movement
path coincides with the imaginary arcuate centerline of said
spacing member.
11. The intervertebral spacing implant of claim 1, wherein the
spacing member further comprises a disc-like member having a
thickness, and a length that is greater in length than said
thickness, and a width that is greater in width than said
thickness.
12. The intervertebral spacing implant of claim 11, wherein the
thickness of the spacing member is defined by a perimeter wall that
constitutes the concave side and the convex side of the external
concavo-convex contour of said spacing member.
13. The intervertebral spacing implant of claim 1, wherein the
spacing member further comprises un upper side having a plurality
of spaced-apart recesses formed therein.
14. The intervertebral spacing implant of claim 13, wherein the
recesses are elongate and are disposed in a substantial parallel
orientation with respect to each other.
15. An intervertebral spacing implant comprising: a spacing member
adapted for implanting between adjacent vertebral bodies of a human
spine as a load-bearing replacement for a spinal disc, said spacing
member further comprising a non-porous body having a tapered
external shape such that said spacing member narrows in thickness
in a first direction.
16. The intervertebral spacing implant of claim 15, said spacing
member having a discontinuous upper surface.
17. The intervertebral spacing implant of claim 15, wherein the
tapered external shape of said spacing member narrows in thickness
in a continuous manner along a majority width of said spacing
member in an anterior-to-posterior direction.
18. The intervertebral spacing implant of claim 17, wherein the
spacing member include an upper surface that forms an acute angle
with respect to a horizontal plan, said acute angle being in a
range of two to six degrees.
19. The intervertebral spacing implant of claim 18, the spacing
member having a discontinuous upper surface.
20. The intervertebral spacing implant of claim 19, wherein the
upper surface includes a plurality of elongate recesses formed
therein, said recesses extending in an anterior-to-posterior
direction.
21. The intervertebral spacing implant of claim 18, wherein the
spacing member includes a lower surface that forms an acute angle
with respect to a horizontal plan, said acute angle being in a
range of approximately two degrees to eight degrees.
22. The intervertebral spacing implant of claim 21, wherein the
upper and lower surface of the spacing member each form a
continuous acute angle of approximately four degrees with respect
to a horizontal plane, for a total continuous taper of
approximately eight degrees.
23. The intervertebral spacing implant of claim 15, wherein said
spacing member further comprises a convex side, and wherein the
tapered external shape of said spacing member is adapted such that
said spacing member narrows in thickness in an
anterior-to-posterior direction when implanted with said convex
side facing an anterior direction.
24. The intervertebral spacing implant of claim 23, wherein the
spacing member further comprises an upper surface, and wherein the
tapered external shape of the spacing member is such that the upper
surface of said spacing member defines a first acute angle with
respect to a plane that is orthogonal to the convex side of the
spacing member.
25. The intervertebral spacing implant of claim 15, wherein the
tapered external shape of said spacing member comprises a taper
sufficient in degree to permit a lordosis spinal configuration to
be restored when said spacing member is sandwiched between adjacent
intervertebral bodies.
26. An intervertebral spacing implant system comprising: a spacing
member adapted for implanting between adjacent intervertebral
bodies of a human spine; positioning means for enabling a surgeon
to adjust a position of the spacing member when said spacing member
resides between adjacent intervertebral bodies, said positioning
means comprising a sheath member, a rod member slidably insertable
into the sheath member, and a means for releasably attaching the
rod member to the spacing member.
27. The intervertebral spacing implant system of claim 26, wherein
the rod member has a longer length than the sheath member, such
that a proximal portion of the rod member protrudes from the sheath
member when said rod member resides within said sheath member and
is attached to the spacing member.
28. The intervertebral spacing implant system of claim 26, wherein
the means for releasably attaching the rod member to the spacing
member further comprises a threaded engagement.
29. The intervertebral spacing implant system of claim 28, wherein
the means for releasably attaching the rod member to the spacing
member further comprises a female threaded recess formed in the
spacing member, and wherein the rod member comprises a male
threaded distal end having a size and configuration sufficient to
permit threaded engagement between said male threaded distal end of
the rod member and the female threaded recess formed in the spacing
member.
30. An intervertebral spacing implant system comprising: a spacing
member adapted for implanting between adjacent intervertebral
bodies of a human spine; positioning means for enabling a surgeon
to adjust a position of the spacing member when said spacing member
resides between adjacent intervertebral bodies, said positioning
means further comprising an attachment means for becoming
releasably attached to the spacing member at a first area of
attachment, and a stabilizing means for removably contacting the
spacing member along a contact line that surrounds the first area
of attachment.
31. The intervertebral spacing implant system of claim 30, wherein
the stabilizing means further comprises means for contacting the
spacing member along a circular contact line that circumscribes the
first area of attachment, said circular contact line being disposed
in a substantially co-axial orientation with respect to the first
area of attachment.
32. A method of implanting an artificial intervertebral disc
comprising: (a) making an incision in an anulus of a human spinal
column between adjacent vertebral bodies of said spinal column to
thereby expose a space residing between said adjacent vertebral
bodies; (b) inserting a spacing member through the incision and
into position between the adjacent vertebral bodies, and
positioning said spacing member at an anterior location with
respect to the spinal column such that more intervertebral space
resides posteriorly to said spacing member than anteriorly thereto;
(c) applying compression to posterior portions of the adjacent
vertebral bodies.
33. The method of claim 32, further comprising: (d) removing a
natural human disc from the space, prior to part (b).
34. The method of claim 32, wherein part (c) further comprises
compressing the posterior portions of the adjacent vertebral bodies
toward each other to a degree sufficient to move said adjacent
vertebral bodies into a sagittal alignment.
35. The method of claim 34, further comprising: (e) attaching a
holding means to the adjacent vertebral bodies for holding said
adjacent vertebral bodies in the sagittal alignment to thereby
inhibit said vertebral bodies from moving out of sagittal
alignment.
36. The method of claim 32, wherein part (b) further comprises
positioning the spacing member sufficiently anteriorly such that
said spacing member resides in contact with an anterior
longitudinal ligament of the spinal column.
37. A method of implanting an artificial intervertebral disc
comprising: (a) making an incision in an anulus of a human spinal
column between adjacent vertebral bodies of said spinal column to
thereby expose a space residing between said adjacent vertebral
bodies; (b) inserting a spacing member through the incision and
into position between the adjacent vertebral bodies, and
positioning said spacing member at an anterior location with
respect to the spinal column such that more intervertebral space
resides posteriorly to said spacing member than anteriorly thereto;
(c) placing bone grafting material through the incision and into
position between the adjacent vertebral bodies such that said bone
grafting material resides between the spacing member and a
posterior longitudinal ligament of the spinal column; and (d)
attaching a compression means to posterior portions of the adjacent
vertebral bodies to thereby force said posterior portions of the
adjacent vertebral bodies toward each other and thereby compress
the bone grafting material, said compression means comprising
pedicle screws and rod members intercoupling said screws.
38. The method of claim 37, wherein the bone grafting material
comprises autogenous bone.
39. A method of implanting an artificial intervertebral disc
comprising: (a) inserting a spacing member into position between
adjacent vertebral bodies of a human spinal column, and positioning
said spacing member at an anterior location with respect to the
spinal column such that more intervertebral space resides
posteriorly to said spacing member than anteriorly thereto; and (b)
applying compression to posterior portions of the adjacent
vertebral bodies.
40. The method of claim 39, further comprising additional parts to
be performed prior to part (b), said additional parts comprising:
(i) placing bone grafting material into position between the
adjacent vertebral bodies such that said bone grafting material
resides between the spacing member and a posterior longitudinal
ligament of the spinal column; and (ii) attaching a compression
means to posterior portions of the adjacent vertebral bodies to
thereby force said posterior portions of the adjacent vertebral
bodies toward each other and thereby compress the bone grafting
material, said compression means comprising pedicle screws and rod
members intercoupling said screws.
41. A method of implanting an artificial intervertebral disc
comprising: (a) making an incision in an anulus of a human spinal
column between adjacent vertebral bodies of said spinal column to
thereby expose a space residing between said adjacent vertebral
bodies; (b) selecting a spacing member comprising an external
concavo-convex contour with respect to one dimension of said
spacing member, wherein the spacing member defines an imaginary
arcuate centerline residing between opposing sides of the external
concavo-convex contour of said spacing member; (c) inserting the
spacing member along an arcuate insertion path through the incision
such that the imaginary arcuate centerline follows said arcuate
insertion path during the insertion.
42. A method of implanting an artificial intervertebral disc
comprising: (a) making an incision in an anulus of a human spinal
column between adjacent vertebral bodies of said spinal column to
thereby expose a space residing between said adjacent vertebral
bodies; (b) inserting a trial spacer through the incision and into
position between the adjacent vertebral bodies, and evaluating a
snugness of fit of said spacer as it resides between said adjacent
vertebral bodies and determining a spacer size thereby; (c)
selecting a spacing member having the spacer size determined in
part (b) and inserting said spacing member through the incision and
into position between the adjacent vertebral bodies.
43. The method of claim 42, wherein part (b) further comprises
dislodging any unwanted soft tissue from between the vertebral
bodies with the trial spacer.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not Applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable.
BACKGROUND OF THE INVENTION
[0003] 1. The Field of the Invention
[0004] The present invention relates generally to an intervertebral
spacer, and more particularly, but not necessarily entirely, to a
interbody spacing system for accomplishing enhanced intervertebral
fusion between adjacent vertebral bodies of a human spine.
[0005] 2. Description of Related Art
[0006] The human spine is a complex, sophisticated mechanical
system. The vertebrate spine operates as a structural member,
providing structural support for the other body parts. A normal
human spine is segmented with seven cervical, twelve thoracic and
five lumbar segments. The lumbar portion of the spine resides on
the sacrum, which is attached to the pelvis. The pelvis is
supported by the hips and leg bones. The bony vertebral bodies of
the spine are separated by intervertebral discs, which reside
sandwiched between the vertebral bodies and operate as joints
allowing known degrees of flexion, extension, lateral bending and
axial rotation.
[0007] The intervertebral disc primarily serves as a mechanical
cushion between adjacent vertebral bodies, and permits controlled
motions within vertebral segments of the axial skeleton. The disc
is a multi-element system, having three basic components: the
nucleus pulposus ("nucleus"), the anulus fibrosus ("anulus") and
two vertebral end plates. The end plates are made of thin cartilage
overlying a thin layer of hard, cortical bone that attaches to the
spongy, richly vascular, cancellous bone of the vertebral body. The
plates thereby operate to attach adjacent vertebrae to the disc. In
other words, a transitional zone is created by the end plates
between the malleable disc and the bony vertebrae.
[0008] The anulus of the disc forms the disc perimeter, and is a
tough, outer fibrous ring that binds adjacent vertebrae together.
The fiber layers of the anulus include fifteen to twenty
overlapping plies, which are inserted into the superior and
inferior vertebral bodies at roughly a 40 degree angle in both
directions. This causes bi-directional torsional resistance, as
about half of the angulated fibers will tighten when the vertebrae
rotate in either direction.
[0009] It is common practice to remove a spinal disc in cases of
spinal disc deterioration, disease or spinal injury. The discs
sometimes become diseased or damaged such that the intervertebral
separation is reduced. Such events cause the height of the disc
nucleus to decrease, which in turn causes the anulus to buckle in
areas where the laminated plies are loosely bonded. As the
overlapping laminated plies of the anulus begin to buckle and
separate, either circumferential or radial anular tears may occur.
Such disruption to the natural intervertebral separation produces
pain, which can be alleviated by removal of the disc and
maintenance of the natural separation distance. In cases of chronic
back pain resulting from a degenerated or herniated disc, removal
of the disc becomes medically necessary.
[0010] In some cases, the damaged disc may be replaced with a disc
prosthesis intended to duplicate the function of the natural spinal
disc. U.S. Pat. No. 4,863,477 (granted Sep. 5, 1989 to Monson)
discloses a resilient spinal disc prosthesis intended to replace
the resiliency of a natural human spinal disc. U.S. Pat. No.
5,192,326 (granted Mar. 9, 1993 to Bao et al.) teaches a prosthetic
nucleus for replacing just the nucleus portion of a human spinal
disc.
[0011] In other cases it is desired to fuse the adjacent vertebrae
together after removal of the disc, sometimes referred to as
"intervertebral fusion" or "interbody fusion."
[0012] In cases of intervertebral fusion, it is known to position a
spacer centrally within the space where the spinal disc once
resided, or to position multiple spacers within that space. Such
practices are characterized by certain disadvantages, including a
disruption in the natural curvature of the spine. For example, the
vertebrae in the lower "lumbar" region of the spine reside in an
arch referred to in the medical field as having a sagittal
alignment. The sagittal alignment is compromised when adjacent
vertebral bodies that were once angled toward each other on their
posterior side become fused in a different, less angled orientation
relative to one another.
[0013] Another disadvantage of known spacing techniques and
intervertebral spacers are the additional surgical complications
that arise in the use of multiple spacers in a single disc space.
In such cases, surgeons will often first perform a posterior
surgery to remove the affected disc and affix posterior
instrumentation to the posterior side of the vertebrae to hold the
posterior portions of the vertebrae in a desired position.
Placement of the multiple spacers is often too difficult to
accomplish from the posterior side of the patient, at least without
causing with undue trauma to the patient, because a surgeon would
need to retract the dura nerve as well as the anterior longitudinal
ligament, thereby increasing damage, pain and morbidity to the
patient. Surgeons have therefore often chosen to turn the patient
over after completing the posterior surgical portion, to perform an
anterior operative procedure, through the patient's belly, in order
to insert multiple spacers between the vertebrae from the anterior
side instead of from the posterior side.
[0014] U.S. Pat. No. 5,961,554 (granted Oct. 5, 1999 to Janson et
al.) illustrates a spacer having a high degree of porosity
throughout, for enhanced tissue ingrowth characteristics. This
patent does not address the problem of compromising the sagittal
alignment, or of increased pain and trauma to the patient by
implantation of multiple spacers in a single disk space.
[0015] The prior art is thus characterized by several disadvantages
that are addressed by the present invention. The present invention
minimizes, and in some aspects eliminates, the above-mentioned
failures, and other problems, by utilizing the methods and
structural features described herein.
BRIEF SUMMARY AND OBJECTS OF THE INVENTION
[0016] It is therefore an object of the present invention to
provide an intervertebral spacing system that does not require an
additional, anterior surgical procedure.
[0017] It is another object of the present invention, in accordance
with one aspect thereof, to provide such an intervertebral spacing
system by which sagittal alignment of the spine is restored.
[0018] It is a further object of the present invention, in
accordance with one aspect thereof, to provide such an
intervertebral spacing system that can accommodate a larger
host-graft interface between adjacent vertebral bodies.
[0019] It is an additional object of the present invention, in
accordance with one aspect thereof, to provide such an
intervertebral spacing system in which bone grafting material is
loaded in compression between adjacent vertebral bodies of the
spine.
[0020] It is yet another object of the present invention, in
accordance with one aspect thereof, to provide such an
intervertebral spacing system that does not require retraction of
the dural nerve, or of the anterior or posterior longitudinal
ligaments, for implantation of the spacer.
[0021] The above objects and others not specifically recited are
realized in a specific illustrative embodiment of an intervertebral
spacer adapted for implanting between adjacent vertebral bodies of
a human spine as a load-bearing replacement for a spinal disc. The
spacing member includes an external, non-porous, concavo-convex
contour with respect to one dimension of said spacing member. The
spacing member is preferably constructed from a rigid,
non-resilient load-bearing material that is incapable of elastic
deformation. The spacing member is inserted with the aid of a
sheathed trocar device that is releasably attached to the spacer,
to enable implantation and selective positioning of the spacer by
the surgeon from the posterior side of the spine, without the need
to retract the dural nerve or the posterior longitudinal
ligament.
[0022] Additional objects and advantages of the invention will be
set forth in the description which follows, and in part will be
apparent from the description, or may be learned by the practice of
the invention without undue experimentation. The objects and
advantages of the invention may be realized and obtained by means
of the instruments and combinations particularly pointed out in the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The above and other objects, features and advantages of the
invention will become apparent from a consideration of the
subsequent detailed description presented in connection with the
accompanying drawings in which:
[0024] FIG. 1 is a perspective view of an intervertebral spacer,
made in accordance with the principles of the present
invention;
[0025] FIG. 2 is a plan view of the intervertebral spacer of FIG.
1;
[0026] FIG. 3 is a frontal view of the intervertebral spacer of
FIGS. 1 and 2;
[0027] FIG. 4 is a side view of the intervertebral spacer of FIGS.
1, 2 and 3;
[0028] FIG. 5 is side view of a pair of adjacent vertebral bodies
from the lumbar region of a human spine;
[0029] FIG. 6 is a schematic view of a sheathed trocar device
releasably attached to a trial spacer shaped similarly to the
intervertebral spacer of FIG. 1, in accordance with the principles
of the present invention;
[0030] FIG. 7 is a schematic view of a sheathed trocar device
releasably attached to the intervertebral spacer of FIG. 1, in
accordance with the principles of the present invention;
[0031] FIGS. 8A-8D illustrate a schematic progression of the
placement of the intervertebral spacer of FIG. 1 between vertebral
bodies of a human spine; and
[0032] FIG. 9 illustrates posterior instrumentation by which
compression is applied to the posterior sides of a paid of
adjacenet vertebral bodies of a human spine.
DETAILED DESCRIPTION OF THE INVENTION
[0033] For the purposes of promoting an understanding of the
principles in accordance with the invention, reference will now be
made to the embodiments illustrated in the drawings and specific
language will be used to describe the same. It will nevertheless be
understood that no limitation of the scope of the invention is
thereby intended. Any alterations and further modifications of the
inventive features illustrated herein, and any additional
applications of the principles of the invention as illustrated
herein, which would normally occur to one skilled in the relevant
art and having possession of this disclosure, are to be considered
within the scope of the invention claimed.
[0034] Before the apparatus and methods of the present invention
are described further, it is to be understood that the invention is
not limited to the particular configurations, process steps, and
materials disclosed herein as such configurations, process steps,
and materials may vary somewhat. It is also to be understood that
the terminology employed herein is used for the purpose of
describing particular embodiments of the invention only, and is not
intended to be limiting since the scope of the present invention
will be limited only by the appended claims and equivalents
thereof.
[0035] The publications and other reference materials referred to
herein to describe the background of the invention and to provide
additional detail regarding its practice are hereby incorporated by
reference. The references discussed herein are provided solely for
their disclosure prior to the filing date of the present
application. Nothing herein is to be construed as a suggestion or
admission that the inventors are not entitled to antedate such
disclosure by virtue of prior invention.
[0036] In describing and claiming the present invention, the
following terminology will be used in accordance with the
definitions set out below.
[0037] As used herein, "comprising," "including," "containing,"
"characterized by," and grammatical equivalents thereof are
inclusive or open-ended terms that do not exclude additional,
unrecited elements or method steps.
[0038] Applicants have discovered that several of the disadvantages
of the prior art spinal disc replacement systems can be minimized,
or even eliminated, by the use of a cashew-shaped interbody spacer
having a tapered external shape, placing it is far anteriorly as
possible between adjacent vertebral bodies, filling in the
remaining posterior space with bone graft material, and applying
compression to posterior portions of the vertebral bodies to load
the bone graft in compression and restore sagittal alignment.
[0039] Referring now to FIGS. 1-4, there is shown a spacing member,
referred to also herein as an intervertebral spacer or an interbody
spacer, designated generally at 10.
[0040] Briefly stated, the spacer 10 is utilized, along with
autogenous bone grafting material, to replace a diseased or damaged
spinal disc. Referring now to FIGS. 5-7, the procedure is
implemented by making an incision 32 in the anulus 34 connecting
adjacent vertebral bodies 31. The spinal disc (not shown) is
surgically removed from the incision 32, after which the spacer 10
is placed through the incision 32 into position between the
vertebral bodies 31. The spacer is preferably placed with its
convex, anterior sidewall 12 facing anteriorly, and with its
concave, posterior sidewall 14 facing posteriorly. Bone grafting
material is placed through the incision 32 to reside behind the
spacer 10, after which posterior instrumentation is attached to
pedicle areas 34 to force the vertebral bodies 31 together in
compression, as illustrated schematically in FIG. 8D and more
particularly in FIG. 9.
[0041] The unique aspects and procedures relating to the spacer 10
will now be explained in more detail. Some of the key features of
the invention comprise the size, shape and placement of spacer 10.
The spacer 10 is preferably made of titanium, thus having a
non-porous quality with a preferably smooth finish. The spacer 10
could also be made of ceramic, or any other suitable material that
is inert and biologically compatible. The spacer 10 is thus
constructed from a rigid, non-resilient load-bearing material, one
that is preferably incapable of elastic deformation. The spacer 10,
by its anterior, convex sidewall 12 and its posterior, concave
sidewall 14, has thereby a concavo-convex contour with respect to
one dimension.
[0042] It is to be understood that the concept of an object having
a concavo-convex contour with respect to one dimension of the
object, as referred to herein, shall not require the concave and
convex sides of the object to be parallel to one another, although
such is preferred. The concept does however refer to a dimension in
which the concave and convex sides of the object are at least
partially facing the direction of that dimension, as indicated by
the dimension 16 of FIG. 1 in relation to the spacer 10. It is also
to be understood that the concept of an object being concavo-convex
in a single dimension shall thereby include an object that has
concave and convex sides 14 and 12 in a horizontal dimension 16,
even though those very same sides are linear in a vertical
dimension 20 at all points, such as in the case of the spacer 10
shown in FIG. 1. For example, the spacer 10 is concavo-convex in
the anterior-posterior direction 16, though not in a medial-lateral
direction 18 or vertical direction 20.
[0043] The upper surface 22 of the spacer 10 is preferably a
planer, discontinuous surface having a plurality of spaced-apart
elongate recesses 24, with preferably a corner point 28 whereby one
side 26 of the spacer 10 begins tapering in the medial-lateral
direction 18, as shown most clearly in FIG. 3. The primary taper of
the spacer 10 occurs in the anterio-to-posterior direction 16, in
that the spacer 10 narrows in thickness in a continuous manner
along substantially the entire spacer 10 as shown most clearly in
FIG. 4. The upper surface 22 and lower surface 30 form an acute
angle relative to a horizontal plane 23, the angle being with a
range of preferably two to eight degrees, most preferably four
degrees. The entire taper is therefore most preferably an eight
degree total taper, with four degrees of taper resulting from the
upper surface 22 and the other four degrees of taper resulting from
the lower surface 30.
[0044] As shown most clearly in FIG. 2, the spacer 10 has an
arc-length AL that is preferably 1.218 inches, a width W that is
preferably 0.320 inches, a depth D that is preferably 0.532 inches,
an inner radius R.sub.2 that is 0.271 inches, an outer radius
R.sub.1 that is preferably 0.591 inches, and side radii R.sub.3 and
R.sub.4 that are each preferably 0.160 inches.
[0045] The anterior, convex sidewall 12 and the posterior, concave
sidewall 14 of the spacer 10 are each preferably linear in the
vertical dimension 20, and are most preferably parallel relative to
one another.
[0046] The primary goal in intervertebral fusion are immobilization
of the affected vertebrae, restoration of the spinal disc space and
sagittal alignment, and to provide an environment for bony fusion
between vertebral bodies. Applicants have discovered that these
goals are most effectively accomplished by the mechanical principle
of a cantilever. Using the spacer 10 as a compression point, a
cantilever is constructed within the disc space as shown most
clearly in FIG. 8D. The procedure for accomplishing this is as
follows.
[0047] FIG. 8A is a schematic side, internal view of the vertebral
bodies 31 indicated in FIG. 5. The spinal disc 33 resides between
the vertebral bodies 31, all of which reside between the anterior
longitudinal ligament (ALL) 36 and the posterior longitudinal
ligament (PLL) 38. The dural nerve (Dura) 40 resides posteriorly to
the vertebral bodies 31 and the PLL 38.
[0048] Referring now to FIG. 8B and FIG. 9, posterior access to the
spine of the patient (not shown) is accomplished. Posterior
instrumentation, preferably pedicle screws 42 (FIG. 9), are affixed
to posterior pedicle portions 34 of the vertebral bodies 31. The
associated rods 44 and structure interconnecting the rods 44 with
the pedicle screws 42 are not affixed until later on in the
procedure. A posterior portion of the lower vertebral body involved
in the fusion, namely, the left inferior articular facet, is
removed and saved for future autogenous bone grafting. A lamina
spreader (not shown, but indicated in FIGS. 8B and 8C), is placed
between the spinous processes 35 (shown in FIG. 5), and is operated
to spread the adjacent vertebral bodies 31 apart. The anterior
longitudinal ligament 36 and posterior longitudinal ligament 38 are
left intact and need not be retracted.
[0049] After coagulation of the veins (not shown), the incision 32
(FIG. 5) is made, preferably with a #15 scalpel, or any suitable
surgical instrument, in a side section of the anulus 37. The disc
33 is then detached from the vertebral end plates (not shown) with
the proper surgical instrumentation, and is removed through the
incision 32. Care is taken not to violate the bony vertebral end
plate, which would cause excessive bleeding and compromise the
resistance to axial load when the spacer 10 is inserted.
[0050] When as much disc material has been removed as can safely be
accomplished, a trial spacer 50 is used to determine the correct
spacer size. The trial spacer 50 preferably has the same shape as
the spacer 10, both of which are part of a set having various
sizes, except that the trial spacer 50 does not include the
recesses 24. The trial spacer 50 is inserted into the incision 32
with a sheathed trocar device 52. The main purpose of trial spacer
50 is to evaluate a snugness of fit of said trial spacer 50 as it
resides between the adjacent vertebral bodies 31, which enables the
surgeon to determine a spacer size thereby. The trial spacer 50 may
also have sharp edging, and is useable to clear away any remaining
unwanted tissue.
[0051] When the spacer size has been determined, a bone graft is
prepared, preferably autogenous bone graft material 54 as shown in
FIG. 8C. Care is taken to remove all soft tissue from the
autogenous bone, which will facilitate successful osseointegration
of the graft. Additional bone can also be harvested from the
spinous processes 35. The harvested autogenous bone is then passed
through a bone mill (not shown) to form suitable bone grafting
material as known and understood to those having ordinary skill in
the art.
[0052] The spacer 10 is inserted through the incision 32 with the
sheathed trocar device 52. The sheathed trocar device 52 includes a
trocar rod 56 preferably slidably disposed within a hollow sheath
58. The trocar rod 56 and the hollow sheath 58 may moveably engaged
with each other in any suitable manner.
[0053] Both the trial spacer 50 and the spacer 10 preferably
include a female-threaded opening 50a and 10a formed therein,
respectively, in which a male-threaded portion 57 of the trocar rod
56 may be releasably inserted. The trocar rod 56 may of course be
releasably attached to the trial spacer 50 and spacer 10 in any
other suitable manner. The trocar rod 56 has a longer length than
the sheath member 58, such that a proximal portion 60 of the trocar
rod 56 protrudes from the sheath member 58 when the trocar rod 56
is attached to the trial spacer 50 or the spacer 10.
[0054] The sheathed trocar device 52 accordingly provides an
efficiently stabilized, releasable connection with the spacer 10.
With the trocar rod 56 being attached directly to the spacer 10,
the sheath member 58 provides additional support by abutting up
against the spacer and contactably circumscribing the point of the
attachment of the trocar rod 56 with the spacer 10, thereby
providing additional stability and control over the positioning of
the spacer 10.
[0055] The surgeon then selectively positions the spacer 10 within
the space residing between the adjacent vertebral bodies 31,
preferably as far anteriorly as possible and most preferably such
that the spacer 10 resides in contact with the anterior
longitudinal ligament 36.
[0056] With the spacer 10 in place, the bone grafting material 54
is placed through the incision 32 and into position between the
adjacent vertebral bodies 31, such that said bone grafting material
54 resides posteriorly to the concave sidewall 14 of the spacer 10,
and thus between the sidewall 14 and the posterior longitudinal
ligament 38. A bone funnel (not shown) as known to those having
ordinary skill in the field may be used to funnel morselized bone
grafting material into the incision 32.
[0057] It is noted that the concavo-convex shape of the spacer 10,
and the method of implantation with the spacer 10 residing as far
anteriorly as possible, operates to provide a larger bone-graft
interface between the adjacent vertebral bodies 31.
[0058] Referring now to FIG. 8D and FIG. 9, the lamina spreader is
removed and the pedicle screws 42 are interconnected with the rods
44 as known in the field. Mild compression is applied by a
compression instrument 46 to thereby slide rods 44 downwardly,
after which the pedicle screws 42 are tightened to hold the rods 44
in place and maintain the compression. Further compression is
applied as desired, with the result being illustrated schematically
in FIG. 8D. The bone grafting material 54 is thereby loaded in
compression by the posteriorly compressed adjacent vertebral bodies
31 as shown. After final inspection of the placement of the bone
grafting material 54, routine closure of the wound is completed.
The use of drains may be made at the discretion of the surgeon.
[0059] The spacer 10 thus operates to cause the adjacent vertebral
bodies 31 to be suspended in the manner of a cantilever. The
posterior compression provided by the pedicle screws 42 and rods
44, which may alternatively be provided by any other suitable
holding structure, causes the adjacent vertebral bodies 31 to be
brought closer together on their posterior side than on their
anterior side, consistent with the natural sagittal alignment in
which they were originally positioned, as understood by those
having ordinary skill in the field.
[0060] It will be appreciated that the structure and apparatus of
the trocar rod 56 and sheath 58 constitute a positioning means for
enabling a surgeon to adjust a position of the spacer 10 when the
spacer 10 resides between the adjacent intervertebral bodies 31.
That structure is merely one example of a means for positioning the
spacer 10, and it should be appreciated that any structure,
apparatus or system for positioning which performs functions that
are the same as, or equivalent to, those disclosed herein are
intended to fall within the scope of a means for positioning,
including those structures, apparatus or systems for positioning
which are presently known, or which may become available in the
future. Anything which functions the same as, or equivalently to, a
means for positioning falls within the scope of this element.
[0061] In accordance with the features and combinations described
above, a preferred method of implanting an artificial
intervertebral disc includes:
[0062] (a) making an incision in an anulus of a human spinal column
between adjacent vertebral bodies of said spinal column to thereby
expose a space residing between said adjacent vertebral bodies;
[0063] (b) inserting a spacing member through the incision and into
position between the adjacent vertebral bodies, and positioning
said spacing member at an anterior location with respect to the
spinal column such that more intervertebral space resides
posteriorly to said spacing member than anteriorly thereto;
[0064] (c) applying compression to posterior portions of the
adjacent vertebral bodies.
[0065] It is to be understood that the above-described arrangements
are only illustrative of the application of the principles of the
present invention. Numerous modifications and alternative
arrangements may be devised by those skilled in the art without
departing from the spirit and scope of the present invention and
the appended are intended to cover such modifications and
arrangements. Thus, while the present invention has been shown in
the drawings and fully described above with particularity and
detail in connection with what is presently deemed to be the most
practical and preferred embodiment(s) of the invention, it will be
apparent to those of ordinary skill in the art that numerous
modifications, including, but not limited to, variations in size,
materials, shape, form, function and manner of operation, assembly
and use may be made without departing from the principles and
concepts set forth herein.
* * * * *