U.S. patent application number 11/234481 was filed with the patent office on 2007-04-12 for spinal stabilization systems and methods.
Invention is credited to Darin C. Gittings, Michael L. Reo, Janine C. Robinson.
Application Number | 20070083200 11/234481 |
Document ID | / |
Family ID | 37900215 |
Filed Date | 2007-04-12 |
United States Patent
Application |
20070083200 |
Kind Code |
A1 |
Gittings; Darin C. ; et
al. |
April 12, 2007 |
Spinal stabilization systems and methods
Abstract
Spinal stabilization devices, systems, and methods are
described. In a first aspect, a foramenal spacer includes a rigid
member adapted to maintain the integrity of the foramenal space. In
a second aspect, facet joint stabilizing members and prosthetic
facet joints are provided to augment or replace the native facet
joint. In a third aspect, lateral spinal stabilization systems are
adapted to be attached to the lateral surfaces of adjacent
vertebral bodies. In a fourth aspect, anterior spinal stabilization
systems are adapted to be attached to the anterior surfaces of
adjacent vertebral bodies. In a fifth aspect, several embodiments
of dynamic spinal stabilization devices and systems are described.
Each of the foregoing devices, systems, and methods is suitable for
use independently, in combination with other devices, systems, and
methods described herein, and/or in combination with prosthetic
intervertebral discs known in the art.
Inventors: |
Gittings; Darin C.;
(Sunnyvale, CA) ; Reo; Michael L.; (Redwood City,
CA) ; Robinson; Janine C.; (Half Moon Bay,
CA) |
Correspondence
Address: |
ORRICK, HERRINGTON & SUTCLIFFE, LLP;IP PROSECUTION DEPARTMENT
4 PARK PLAZA
SUITE 1600
IRVINE
CA
92614-2558
US
|
Family ID: |
37900215 |
Appl. No.: |
11/234481 |
Filed: |
September 23, 2005 |
Current U.S.
Class: |
606/279 |
Current CPC
Class: |
A61F 2/4405 20130101;
A61F 2002/30578 20130101; A61F 2002/30563 20130101; A61B 17/7071
20130101; A61F 2002/4495 20130101; A61B 17/7064 20130101; A61F
2/442 20130101; A61B 2017/00867 20130101 |
Class at
Publication: |
606/061 |
International
Class: |
A61F 2/30 20060101
A61F002/30 |
Claims
1. A foramenal spacer, comprising: a first support member having an
external surface configured to engage the pedicle surface of a
first vertebral body of a patient; a second support member having
an external surface configured to engage the pedicle surface of a
second vertebral body of a patient, said second vertebral body
being adjacent to said first vertebral body; said first support
member and said second member being connected together such that a
foramenal height between said first vertebral body and said second
vertebral body is maintained at no less than a minimum foramenal
height when said foramenal spacer is interposed between said first
vertebral body and second vertebral body.
2. The foramenal spacer of claim 1, wherein said first support
member and said second support member define a passage
therebetween.
3. The foramenal spacer of claim 2, wherein said first support
member and said second support member are capable of rotational
movement relative to one another.
4. The foramenal spacer of claim 2, wherein said first support
member and said second support member are capable of expansive
movement relative to one another.
5. A method for augmenting a facet joint between a superior
vertebral body and an inferior vertebral body of a patient,
comprising: providing a facet stabilizer, said facet stabilizer
including a first endplate, a second endplate, and a core member
interposed between said first endplate and said second endplate;
and implanting said facet stabilizer between the facets comprising
said facet joint.
6. A method for mammalian spinal stabilization, comprising:
implanting a prosthetic intervertebral disc between a superior
vertebral body and an inferior vertebral body of a patient; and
implanting a stabilizer system configured to engage said superior
vertebral body and said inferior vertebral body of said
patient.
7. The method of claim 6, wherein said stabilizer system comprises
a spacer interposed between the spinous processes of each of said
superior vertebral body and said inferior vertebral body.
8. The method of claim 7, wherein said stabilizer system further
comprises a restrictor band attached to each of said superior
vertebral body and said inferior vertebral body.
9. The method of claim 7, wherein said stabilizer system further
comprises a disc member embedded in said spacer, said disc member
comprising an upper endplate, a lower endplate, and a core member
located between said upper endplate and said lower endplate.
10. The method of claim 6, wherein said stabilizer system comprises
a first attachment member connected to said superior vertebral
body, a second attachment member connected to said inferior
vertebral body, and a stabilizer member connected to each of said
first attachment member and said second attachment member.
11. The method of claim 10, wherein said stabilizer member
comprises a shape memory material.
12. The method of claim 10, wherein at least one of said first
attachment member and said second attachment member is rotatable,
and wherein rotation of at least one of said first attachment
member and said second attachment member causes force from movement
of one of said superior vertebral body or said inferior vertebral
body to be transferred to said other of said superior vertebral
body or said inferior vertebral body.
13. The method of claim 6, wherein said stabilizer system comprises
a first member attached to and configured to impart a distracting
force between each of said superior vertebral body and said
inferior vertebral body, and a second member attached to and
configured to impart an attracting force between each of said
superior vertebral body and said inferior vertebral body.
14. The method of claim 10, wherein said first attachment member is
connected to a transverse process of said superior vertebral body,
and said second attachment member is connected to a transverse
process of said inferior vertebral body.
15. The method of claim 10, wherein said stabilizer system further
comprises a pot configured to receive and retain a filler
material.
16. The method of claim 6, wherein said stabilizer system is
attached to lateral surfaces of said superior vertebral body and
said inferior vertebral body.
17. The method of claim 6, wherein said stabilizer system is
attached to anterior surfaces of said superior vertebral body and
said inferior vertebral body.
Description
BACKGROUND OF THE INVENTION
[0001] The spine is comprised of twenty-four vertebrae that are
stacked one upon the other to form the spinal column. The spine
provides strength and support to allow the body to stand and to
provide flexibility and motion. A Section of each vertebrae
includes a passageway that provides passage of the spinal cord
through the spinal column. The spine thereby encases and protects
the spinal cord. The spinal cord also includes thirty-one pairs of
nerve roots that branch from either side of the spinal cord,
extending through spaces between the vertebrae known as the neural
foramen.
[0002] An intervertebral disc is located between each pair
of-vertebrae. The disc is composed of three component structures:
(1) the nucleus pulposus; (2) the annulus fibrosus; and (3) the
vertebral endplates. The disc serves several purposes, including
absorbing shock, relieving friction, and handling pressure exerted
between the superior and inferior vertebral bodies associated with
the disc. The disc also relieves stress between the vertebral
bodies, which stress would otherwise lead to degeneration or
fracture of the vertebral bodies.
[0003] Disorders of the spine comprise some of the costliest and
most debilitating health problems facing the populations of the
United States and the rest of the world, costing billions of
dollars each year. Moreover, as these populations continue to age,
the incidence of spinal disorders will continue to grow. Typical
disorders include those caused by disease, trauma, genetic
disorders, or other causes.
[0004] The state of the art includes a number of treatment options.
Medicinal treatments, exercise, and physical therapy are typical
conservative treatment options. Less conservative treatment options
include surgical intervention, including microdiscectomy,
kyphoplasty, laminectomy, dynamic stabilization, disc arthroplasty,
and spinal fusion. Traditionally, these treatment options have been
applied in isolation, rather than in combination, using the most
conservative treatment option that will provide a desired
result.
[0005] U.S. Provisional Patent Application Ser. No. 60/713,671,
entitled "Prosthetic Intervertebral Discs," ("the '671
application"), was filed Sep. 1, 2005, and is assigned to Spinal
Kinetics, Inc., the assignee of the present application. The '671
application describes, inter alia, a treatment option that combines
a prosthetic intervertebral disc with a dynamic stabilization
system. The '671 application is incorporated by reference herein in
its entirety.
[0006] In 1992, Panjabi introduced a model of a dynamic spinal
stabilization system that describes the interaction between
components providing stability in the spine. This model defined
spinal instability in terms of a region of laxity around the
neutral resting position of a spinal segment, identified as the
"neutral zone." Panjabi, M M., "The stabilizing system of the
spine. Part II. Neutral zone and instability hypothesis." J Spinal
Disord 5 (4): 390-397, 1992b. There is some evidence that the
neutral zone can be increased in cases of intervertebral disc
degeneration, spinal injury and spinal fixation. Id Panjabi has
subsequently described dynamic stabilization systems that provide
increased mechanical support while the spine is in the neutral zone
and decreased support as the spine moves away from the neutral
zone. See United States Published Patent Application No.
2004/0236329, published Nov. 25, 2004, which is hereby incorporated
by reference herein.
[0007] The need remains for improved spinal stabilization systems,
combinations of systems, and methods for their use.
SUMMARY OF THE INVENTION
[0008] Spinal stabilization components, systems, and methods are
provided. The spinal stabilization components are suitable for use
individually, together, or with other known spinal stabilization
components and systems.
[0009] In a first aspect, foramenal spacers and methods for their
use are described. The foramenal spacer includes a member that has
a size and shape adapted for insertion into the foramen located
between a pair of adjacent vertebral bodies to prevent the pair of
vertebral bodies from collapsing into one another, i.e., to
maintain the interpedicular spacing between the adjacent vertebral
bodies. The foramenal spacer also preferably includes a passage or
other member that protects the nerve root from being compressed or
otherwise physically impacted as it traverses the foramen. In a
first embodiment, the foramenal spacer includes an upper C-shaped
member, a lower C-shaped member, and an attachment member for
attaching the upper C-shaped member to the lower C-shaped member.
The upper C-shaped member is adapted to be attached to the pedicle
of the superior vertebral body and to extend into the foramen
defined by the pair of vertebral bodies, while the lower C-shaped
member is adapted to be attached to the pedicle of the inferior
vertebral body and to extend into the foramen defined by the pair
of vertebral bodies. When attached together, the upper and lower
C-shaped members define a passageway therethrough for allowing
passage of the nerve root. The attachment member may comprise a
tongue and groove mechanism, a snap-fit mechanism, or other
suitable mechanism for attaching the upper and lower C-shaped
member together. Alternatively, the upper C-shaped member and lower
C-shaped member may each be provided with surfaces adapted to butt
up against one another to form a butt-joint. In still another
embodiment, the C-shaped members are mated such that they allow
some travel (e.g., extension) relative to each other, such as that
which may be required during flexion, extension and lateral
bending, and maintain the patentcy of the passageway to allow
passage of the nerve root.
[0010] In a second embodiment, the foramenal spacer includes an
upper segment and a lower segment. The upper segment is adapted to
be attached to the pedicle of the superior vertebral body and to
extend into the foramen defined by the pair of vertebral bodies,
and the lower segment is adapted to be attached to the pedicle of
the inferior vertebral body and also to extend into the foramen
defined by the pair of vertebral bodies. The interior surface of
one of the upper segment or the lower segment and the external
surface of the other of the upper segment or the lower segment
define a pair of rounded, mating surfaces that together define a
bearing structure that allows the upper segment to pivot relative
to the lower segment. The upper segment and lower segment thereby
act as a bearing to define a center of rotation. Once the upper
segment and lower segment are attached to the respective vertebral
bodies and are engaged with one another, the foramenal spacer
provides a supporting structure that also protects the nerve root
traversing the foramen, and that allows the superior and inferior
vertebral bodies to pivot relative to one another.
[0011] Preferably, the foramenal spacer is formed of a rigid
biocompatible material, such as stainless steel, metal alloys, or
other metallic materials, or a rigid polymeric material. In
alternative embodiments, the foramenal spacer is provided with an
outer layer formed of a soft, conformable material (e.g., an
elastomeric polymer such as polyurethane) that provides
conformability with the foramen geometry and allows flexion,
extension and lateral bending of the spine. In still other
embodiments, the foramenal spacer includes an inner liner formed of
a soft and/or low-friction material to provide an atraumatic
surface for passage of the nerve root.
[0012] In a second aspect, devices, systems and methods for facet
joint augmentation and replacement are provided. The devices and
systems are intended to stabilize the spine and to increase the
foramenal space to thereby reduce the likelihood of nerve root
impingement. In a first embodiment, the stabilization and increase
of foramenal space is accomplished by inserting a stabilizing
member into the facet joint to restore the intra-foramenal
distance. The stabilizing member comprises a structure that
provides shock absorbance, cushioning, and support to the facet
joint. In several embodiments, the stabilizing member comprises an
encapsulated cushion. In other embodiments, the stabilizing member
comprises a structure having a pair of endplates separated by a
resilient core member.
[0013] In a second embodiment, some or all of the facets of each of
the superior and inferior vertebral bodies are removed and replaced
with a facet joint implant. In several embodiments, the facet joint
implant includes an upper prosthetic facet for attachment to the
superior vertebral body, and a lower prosthetic facet for
attachment to the inferior vertebral body. Each prosthetic facet is
attached to its respective vertebral body by screws or other
similar mechanisms. Each prosthetic facet joint includes a pair of
facing plates and a core member located between the pair of facing
plates. The prosthetic facet is constructed and attached in a
manner such that it closely mimics the functionality and
performance of the natural facet joint.
[0014] In a third aspect, a lateral spinal stabilization device is
provided. The lateral spinal stabilization device includes an upper
attachment member and a lower attachment member for attaching to
the lateral surfaces of each of the superior and inferior vertebral
bodies, respectively, and a stabilizing member connected and
extending between each of the upper and lower attachment members.
In one embodiment, the stabilizing member comprises a damping
mechanism. In other embodiments, the stabilizing member comprises a
pair of endplates separated by a resilient core member.
[0015] In a fourth aspect, an anterior spinal stabilization device
is provided. The anterior spinal stabilization device is adapted to
be attached to the anterior surfaces of a pair of vertebral bodies
and to extend between the pair of vertebral bodies to provide
stabilization to the anterior portion of the vertebral unit. In a
first embodiment, the anterior spinal stabilization device is in
the form of a spring having a structure sufficient to carry a load
after implantation and attachment to the vertebral unit. The
anterior stabilization device is preferably implanted by way of a
minimally invasive anterior approach, although posterior and
lateral approaches are also possible.
[0016] In a fifth aspect, several dynamic stabilization devices are
described. Each of the dynamic stabilization devices is intended to
provide a combination of stabilizing forces to one or more spinal
units to thereby assist in bearing and transferring loads. In a
first embodiment, a dynamic stabilization device includes a
posterior spacer member that is located generally between a pair of
adjacent vertebral bodies on the posterior side of the spine. The
posterior spacer is preferably formed of a generally compliant
material and functions to maintain spacing between the pair of
adjacent vertebral bodies while allowing relative motion between
the vertebral bodies. In a preferred form, the posterior spacer is
generally in the form of a short cylinder, having a central
through-hole to allow passage of one or more restrictor bands,
which are described more fully below. The spacer may take other
shapes or forms, however, depending upon the size and shape of the
spinal treatment site. The dynamic stabilization device also
includes one or more restrictor bands, each of which preferably
comprises a loop formed of an elastic material. The restrictor
band(s) each have a size and shape adapted to be attached to the
spinous processes extending from the posterior of the adjacent
vertebral bodies, or to be attached by an appropriate attachment
mechanism to the lamina of the adjacent bodies. Once linked to the
posterior of the spine, the bands provide both stability and
compliance. The performance properties of the bands are able to be
varied by choice of materials, size of the bands, and by the
routing of the restrictor band(s) between the adjacent vertebral
bodies. For example, restrictor bands that are oriented more
vertically than diagonally will provide greater resistance to
flexion of the spine, whereas the more diagonal orientation will
provide additional resistance to torsional movements.
[0017] In other embodiments, a dynamic stabilization device is
constructed and includes materials that allow the device to be
adjusted post-operatively. For example, in one embodiment, the
dynamic stabilization device includes a superior attachment member
for attachment to the pedicle of a superior vertebral body, an
inferior attachment member for attachment to the pedicle of an
inferior vertebral body, and one or more spring members extending
between and interconnecting the superior and inferior attachment
members. In the preferred form, the spring member is formed of a
shape memory material, such as nickel titanium alloy (Nitinol). The
properties of the spring member may thereby be altered
post-operatively by heating elements of the device, such as by
applying an electric current. As the shape memory materials may be
trained by heat treatment processes prior to implantation, the
properties of the spring member may be altered in a known manner by
application of heat in this manner. Preferably, the electric
current is applied by placing leads against the spring member under
X-ray or other guidance A given spring member may be extended or
contracted to provide greater or lesser load support, or to alter
any other performance characteristic of the device.
[0018] In still other embodiments, a spinal stabilization device is
provided that is capable of transferring reactions from one spinal
segment to an adjacent segment. In this manner, the spinal
stabilization device transfers loads and reactions in the same
manner as is done by the natural spinal segments operating
properly. The spinal stabilization device includes at least one
fixation member associated with each vertebral body, and a linkage
member extending between each pair of superior and inferior
fixation members. The fixation members each allow for rotation of
the linkage members, thereby providing the ability for one
vertebral segment to be loaded (or unloaded), either in compression
or torsion, based upon the activity being undergone at an adjacent
vertebral segment.
[0019] In still other embodiments, a dynamic stabilization device
includes a combination of an interspinous stabilization member and
one or more pedicle based stabilization members. In a preferred
form, the one or more pedicle based stabilization members function
by biasing the pair of adjacent vertebral bodies apart, while the
interspinous stabilization member functions by biasing together the
spinous processes of the adjacent pair of vertebral bodies. The
combined action of the interspinous member and the pedicle based
member(s) is to create a moment that relieves pressure from the
disc.
[0020] In still other embodiments, a dynamic stabilization device
is provided and is attached to a pair of adjacent vertebral bodies
at or near one or both pairs of transverse processes extending from
the pair of vertebral bodies. For example, at least one superior
attachment member, such as a screw, is attached to a transverse
process of the superior vertebral body, at least one inferior
attachment member, such as a screw, is attached to the transverse
process of the inferior vertebral body, and a loading member
extends between and interconnects the superior and inferior
attachment members. The attachment members may optionally extend
through the transverse processes into the vertebral bodies, or they
may be attached to the vertebral bodies adjacent to the transverse
processes.
[0021] In still other embodiments, a dynamic stabilization device
is attached such that the stabilization member is located
externally of the patient's skin surface. In these embodiments, the
stabilization member is attached to a pair of adjacent vertebral
bodies by a pair of screws that extend through the patient's skin
and into the pair of vertebral bodies. The stabilization member is
then attached to and extends between the pair of screws on the
exterior of the patient. The device is preferably fully
adjustable.
[0022] In yet other embodiments, a dynamic stabilization device is
provided and includes a fill-type adjustment mechanism. The device
includes a superior attachment member that is preferably attached
to the spinous process of a superior vertebral body, an inferior
attachment member that is preferably attached to the spinous
process of an inferior vertebral body, and a stabilization member
that extends between and interconnects the superior and inferior
attachment members. The attachment members may include screws, or
other suitable attachment mechanisms. Interposed between at least
one of the attachment members and the stabilization member is a
pot. As the pot is filled, such as by injecting a biocompatible
material such as bone cement containing polymethylmethacrylate
(PMMA), the added volume occupied in the pot decreases the
operating length of the stabilization member, thereby also changing
the performance characteristics of a given stabilization member.
Thus, adding material to the pot provides the ability to adjust the
device post-operatively. Preferably, the post-operative adjustment
may be done percutaneously.
[0023] In still other embodiments, a dynamic stabilization device
includes an intervertebral spacer having an integrated stabilizing
disc, the combined unit being interposed between the spinous
processes of a pair of adjacent vertebral bodies.
[0024] Each of the foregoing devices, structures, and methods is
adapted to be used independently, or in combinations of two or
more. Preferably, several devices, structures, or methods are used
in combination to obtain desired results. In particular, each of
the foregoing devices may be used in combination with a prosthetic
intervertebral disc to obtain desired therapeutic results.
[0025] Other and additional devices, apparatus, structures, and
methods are described by reference to the drawings and detailed
descriptions below.
BRIEF DESCRIPTION OF THE FIGURES
[0026] The Figures contained herein are not necessarily drawn to
scale, with some components and features being exaggerated for
clarity.
[0027] FIG. 1 is a lateral view of a pair of adjacent vertebral
bodies, including representation of the foramen and nerve roots
traversing the foramen.
[0028] FIGS. 2A-G are illustrations of foramenal spacers in
accordance with the present invention.
[0029] FIG. 3 is a posterior view of a pair of adjacent vertebral
bodies, including representation of the facets and facet
joints.
[0030] FIG. 4 is a perspective view of an embodiment of a facet
joint stabilizing member.
[0031] FIG. 5 is a side view of another embodiment of a facet joint
stabilizing member shown implanted in a facet joint.
[0032] FIGS. 6A-B are illustrations of prosthetic facets.
[0033] FIG. 7 is an illustration of a portion of a spinal column
having a plurality of prosthetic facets in place of the native
facets.
[0034] FIG. 8 is a lateral view of a pair of vertebral bodies
having a lateral stabilization device implanted therebetween.
[0035] FIG. 9A is a lateral view of a pair of vertebral bodies
having an anterior stabilization device and a posterior
stabilization device implanted therebetween.
[0036] FIG. 9B is an illustration of an anterior stabilization
device.
[0037] FIG. 10A is an illustration of a spacer member.
[0038] FIGS. 10B-D are illustrations of posterior dynamic
stabilization devices including a spacer member and restrictor
bands.
[0039] FIG. 11 is a posterior view of another dynamic stabilization
system.
[0040] FIG. 12 is a posterior view of another dynamic stabilization
system.
[0041] FIG. 13 is a lateral view of another dynamic stabilization
system.
[0042] FIG. 14 is a posterior view of another dynamic stabilization
system.
[0043] FIG. 15 is a lateral view of another dynamic stabilization
system.
[0044] FIG. 16 is a lateral view of another dynamic stabilization
system.
[0045] FIG. 17 is a lateral view of another dynamic stabilization
system.
[0046] FIG. 18 is a three dimensional cross-sectional view of an
exemplary prosthetic intervertebral disc.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0047] Before the present invention is described, it is to be
understood that this invention is not limited to particular
embodiments described, as such may, of course, vary. It is also to
be understood that the terminology used herein is for the purpose
of describing particular embodiments only, and is not intended to
be limiting, since the scope of the present invention will be
limited only by the appended claims.
[0048] Where a range of values is provided, it is understood that
each intervening value, to at least the tenth of the unit of the
lower limit unless the context clearly dictates otherwise, between
the upper and lower limit of that range and any other stated or
intervening value in that stated range is encompassed within the
invention. The upper and lower limits of these smaller ranges may
independently be included in the smaller ranges is also encompassed
within the invention, subject to any specifically excluded limit in
the stated range. Where the stated range includes one or both of
the limits, ranges excluding either or both of those included
limits are also included in the invention.
[0049] Unless defined otherwise, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which this invention belongs. Although
any methods and materials similar or equivalent to those described
herein can also be used in the practice or testing of the present
invention, the preferred methods and materials are now described.
All publications mentioned herein are incorporated herein by
reference to disclose and describe the methods and/or materials in
connection with which the publications are cited.
[0050] It must be noted that as used herein and in the appended
claims, the singular forms "a", "an," and "the" include plural
referents unless the context clearly dictates otherwise.
[0051] The publications discussed herein are provided solely for
their disclosure prior to the filing date of the present
application. Nothing herein is to be construed as an admission that
the present invention is not entitled to antedate such publication
by virtue of prior invention. Further, the dates of publication
provided may be different from the actual publication dates which
may need to be independently confirmed.
[0052] As will be apparent to those of skill in the art upon
reading this disclosure, each of the individual embodiments
described and illustrated herein has discrete components and
features which may be readily separated from or combined with the
features of any of the other several embodiments without departing
from the scope or spirit of the present inventions.
[0053] Turning now to the drawings, FIG. 1 illustrates a pair of
adjacent vertebral bodies, including a superior vertebral body 100
and an inferior vertebral body 102. Each vertebral body includes a
pair of transverse processes 104a-b and a spinous process 106
extending generally posteriorly from each vertebral body 100, 102.
A disc 108 is located between the superior vertebral body 100 and
the inferior vertebral body 102. The spinal cord 110 extends
through a central passage formed by the spinal column, and nerve
roots 112 transverse the foramenal space 114 defined by the pair of
vertebral bodies.
[0054] When the disc is damaged due to trauma, disease, or other
disorder, the superior vertebral body 100 and inferior vertebral
body 102 tend to collapse upon each other, thereby decreasing the
amount of space formed by the foramen 114. This result also
commonly occurs when the vertebral bodies are afflicted with
disease or are fractured or otherwise damaged. When the foramenal
space is decreased, the vertebral bodies 100, 102 tend to impinge
upon the nerve root 112, causing discomfort, pain, and possible
damage to the nerve root. The foramenal spacers described herein
are intended to alleviate this problem by maintaining the foramenal
opening and otherwise protecting the nerve root from impingement by
the vertebral bodies.
[0055] Turning to FIGS. 2A through 2G, several foramenal spacer
embodiments are shown. In a first embodiment, shown in FIGS. 2A-D,
the foramenal spacer 120 includes a superior C-shaped member 122
and an inferior C-shaped member 124. The pair of C-shaped members
preferably include an attachment mechanism or a pair of mating
surfaces. For example, as shown in FIG. 2B, the superior C-shaped
member 122 is provided with a groove 126 on each of its
inferior-facing surfaces 128, whereas the inferior C-shaped member
124 includes a mating tab 130 on each of its superior-facing
surfaces 132. Alternatively, the tabs may be place on the superior
C-shaped member and the grooves on the inferior C-shaped member, or
still other attachment members may be used, such as a snap-fit
mechanism or other similar structure. In still other embodiments,
the mating surfaces 128, 132 may simply butt up against one another
to form a butt-joint that prevents collapse of the foramenal space.
When combined, the pair of C-shaped members define a generally
disc-shaped member 134 having a central through-hole 136. The
central through-hole 136 has a size and shape adapted to allow the
nerve root 112 to pass without impingement as shown, for example,
in FIGS. 2C and 2D.
[0056] Turning to FIG. 2E, the foramenal spacer 120 may be provided
with an outer layer 140 that includes a coating of a soft,
conformable material. The outer layer 140 preferably covers all of
the external-facing surfaces of the foramenal spacer 120, and
particularly those that are positioned to engage the vertebral body
surfaces. The outer layer 140 is preferably formed of a soft,
conformable biocompatible material such as silicone, polyurethane,
or other similar polymeric materials, and may be applied to the
foramenal spacer 120 by methods well-known in the art. The outer
layer 140 may provide structural protection to the vertebral bodies
forming the foramenal space, and also allows the foramenal spacer
120 to adapt to the varying foramenal geometries formed by the
vertebral bodies.
[0057] An optional inner layer or liner 142 may be provided on the
exposed surfaces defining the through-hole 136. The inner layer or
liner 142 is preferably formed of a coating of soft and/or
low-friction material to provide an atraumatic surface for passage
of the nerve root 112. Preferably, the inner layer or liner 142 is
formed of similar materials as those used for the outer layer 140,
including silicone, polyurethane, or other polymeric materials.
Alternatively, the inner layer or liner 142 may comprise a coating
of polyethylene, PTFE, or other similar material.
[0058] In addition, an optional spring member, gasket, cushion, or
other similar material or device (not shown in the drawings) may be
interposed between the superior C-shaped member 122 and the
inferior C-shaped member 124. Preferably, the spring member (or the
like) may be located on the abutting surfaces of the two C-shaped
members. This spring member (or the like) provides the spacer 120
with the capability of vertical expansion and contraction as the
spring member extends and compresses, thereby providing a range of
motion for supporting the foramenal space.
[0059] Turning now to FIG. 2F, another foramenal spacer embodiment
is shown. In this embodiment, the foramenal spacer 120 includes an
upper segment 150 and a lower segment 156. The upper segment 150
includes an external surface 152 that has a shape adapted to engage
the portion of the superior vertebral body defining the foramenal
space 114. Similarly, the lower segment 156 includes an external
surface 158 that has a shape adapted to engage the portion of the
inferior vertebral body defining the foramenal space 114. An
internal surface 154 of the upper segment 150 includes a curved
portion that is adapted to rotatably engage a mating curved portion
of the external surface 158 of the lower segment 156. In this way,
the upper segment 150 and lower segment 156 are rotationally
connected to one another, i.e. the upper segment 150 and lower
segment 152 function similar to a bearing having a center of
rotation. When the upper segment 150 is attached to the superior
vertebral body 100, and the lower segment is connected to the
inferior vertebral body 102, the foramenal spacer 120 allows the
two vertebral bodies to pivot relative to one another, thereby
providing an additional range of motion. The foramenal spacer 120
shown in FIG. 2F also optionally includes the outer layer 140 and
inner layer or liner 142 described above in relation to FIG.
2E.
[0060] The foramenal spacer 120 may be implanted by any appropriate
surgical technique, including accessing the foramenal space by
either a posterior approach or a lateral approach. The lateral
approach is believed to provide optimal access to find exposure of
the foramen, but techniques for posterior lumbar interbody fusion
(PLIF) and transforamenal lumbar interbody fusion (TLIF) also
provide sufficient access. Once access is gained, the foramenal
spacer 120 is preferably attached to the pedicle or other anatomic
structure that allows extension of the spacer into the foramenal
space 114. For example, the foramenal spacer 120 may be press fit
into the foramen 116, as illustrated in FIG. 2G, or a tab (not
shown) may be provided for attaching the foramenal spacer 120 to
the pedicle or other anatomical structure.
[0061] Turning next to FIG. 3, a posterior view of a pair of
adjacent vertebral bodies is shown. The Figures illustrates a
superior vertebral body 100 and an inferior vertebral body 102.
Each vertebral body includes a pair of transverse processes 104a-b
and a spinous process 106 extending generally posteriorly from each
vertebral body 100, 102. The spinal cord 110 extends through a
central passage formed by the spinal column, and nerve roots 112
transverse the foramenal space 114 defined by the pair of vertebral
bodies. A facet joint 118 is formed by a pair of facing facets, one
each from the superior and inferior vertebral bodies.
[0062] Several of the known devices and systems for posterior
spinal stabilization are designed and provide the function of
opening the foramen or maintaining the foramenal spacing in order
to off-load the nerve that traverses the foramen. This is commonly
done by attaching a device to the pedicles of each of the vertebral
bodies and providing a distracting force between the attachment
members. Several alternative and novel devices and methods are
described herein.
[0063] Turning to FIG. 4, a facet stabilizing member 170 is shown.
The facet stabilizing member 170 preferably includes a core member
172 encased in a jacket 174. The core member 172 is preferably
formed of a hydrogel, polyurethane, or other polymeric material
suitable for providing the shock absorbing and spacing function
necessary to stabilize the facet joint. The jacket 174 may be a
woven fabric of biocompatible material and is intended to maintain
the integrity and shape of the core member 172 and to otherwise
provide structural strength to the facet stabilizing member 170.
The facet stabilizing member 170 has a size and shape adapted to be
placed in the facet joint 118 to thereby provide stabilization to
the joint and to prevent collapse of the foramenal space.
[0064] Turning to FIG. 5, another embodiment of a facet stabilizing
member 170 is shown. In this embodiment, the spinal stabilizing
member 170 includes an upper endplate 180, a lower endplate 182,
and a core member 184 extending between and interconnecting the
upper endplate 180 and lower endplate 182. Preferably, the facet
stabilizing member also includes a plurality of fibers 186 wound
between and interconnecting the upper endplate 180 and lower
endplate 182. The construction and materials of the facet
stabilizing member 170 shown in FIG. 5 are similar to the
construction and materials of the prosthetic intervertebral disc
described below in relation to FIG. 18, and to several of the
prosthetic intervertebral discs described in U.S. Patent
application Ser. No. 10/903,276, filed Jul. 30, 2004, and U.S.
Patent Application Ser. No. 60/713,671, filed Sep. 1, 2005, each of
which applications is hereby incorporated by reference herein.
Other prosthetic discs described in the foregoing applications may
also be adapted for use as a facet stabilizing member 170 as
described herein. The size of the facet stabilizing member 170 is
typically smaller than the sizes of the prosthetic discs described
in the foregoing applications, but the overall construction of the
structure is preferably the same.
[0065] The facet stabilizing member 170 is implanted between the
pair of opposed facets associated with the pair of adjacent
vertebral bodies. Additional features, such as fins, fixation
members, or other structures (not shown), may also be incorporated
on the facet stabilizing member 170 to limit translation. The facet
joint is synovial, therefore requiring implantation through the
capsule. Access to the facet joint is obtained by any of the
methods described above in relation to implantation of the
foramenal space r.
[0066] Turning to FIGS. 6A-B, prosthetic facets and facet joints
are shown. During many spinal surgical procedures, particularly
those including approach by the posterior, some or all of the facet
is removed to provide access to implant one or more prosthetic
structures. Similarly, many spinal procedures create loss of height
of the disc or similar unintended results. In these cases, or in
cases in which the facets or facet joints become damaged through
trauma, disease, or other disorder, it may be desirable to replace
some or all of the facet with a prosthetic device to restore
stabilization to the affected spinal segments.
[0067] In FIG. 6A, a number of prosthetic facets 190 are shown as
implanted in several locations on a spinal column. Each prosthetic
facet 190 includes an attachment arm 192 that is generally
elongated and curved to match the shape and structure of the native
facet. The attachment arm 192 terminates in an endplate 194 that
mimics the facing surface of the native facet. The attachment arm
192 is attached to its associated vertebral body by one or more
screws 196 or other suitable attachment mechanism. A facet
stabilizing member 170, identical to those described above in
relation to FIG. 5, is interposed between a pair of prosthetic
facets 190, with the facet endplates 194 serving as the endplates
for the facet stabilizing member 170. (See, in particular, FIG.
6B). As shown in FIG. 6A, the prosthetic facet joint is oriented to
be on plane with the native facet. Thus, the orientation of the
facet joint will vary between vertebral segments.
[0068] FIG. 7 illustrates a multi-level stabilization over several
adjacent vertebral segments using the prosthetic facets 190. A
first prosthetic facet 190 is attached to the sacrum 119, and
additional prosthetic facets 190 are attached to the L5 and L4
vertebrae.
[0069] Turning next to FIG. 8, a lateral stabilization device is
shown. The lateral stabilization device 200 includes an upper
attachment arm 202a adapted to be attached to the superior
vertebral body 100 by one or more screws 204 or other attachment
mechanism, and a lower attachment arm 202b adapted to be attached
to the inferior vertebral body 102 by one or more screws 204 or
other attachment mechanism. The device also includes a
stabilization member 206. The stabilization member 206 may include
a spring, a combination of springs, a damping mechanism, or other
mechanism that provides a desired stabilization function. In a
preferred embodiment, the stabilization member includes a structure
identical to the facet stabilization member 170 described above in
relation to FIG. 5.
[0070] Advantageously, the lateral stabilization device 200 is
attached to the lateral surfaces of the pair of adjacent vertebral
bodies 100, 102. In a particularly preferred embodiment, a lateral
stabilization device 200 is attached on both lateral sides of the
pair of vertebral bodies.
[0071] FIG. 9 shows a pair of adjacent vertebral bodies 100, 102
having both a posterior stabilization device 210 and an anterior
stabilization device 220 attached to each of the pair of vertebral
bodies. The posterior stabilization device 210 includes a pair of
pedicle screws 212, one attached to each of the superior vertebral
body 100 and the inferior vertebral body 102. A stabilization
member 212 extends between and interconnects the pair of pedicle
screws 212. The stabilization member 214 may comprise a load
bearing dynamic structure that is spring loaded, that includes a
damping member, or any combination of such structures. The anterior
stabilization device 220 includes an anterior element 222, the
details of which are best shown in FIG. 9B. The anterior element
222 is preferably formed of a material having superelastic
properties, and includes a shape that allows the anterior element
222 to be constrained for a minimally invasive implantation
procedure. As shown, the anterior element 222 includes an
attachment hole 224 at each end, and a central portion 226 that
includes a pair of side bands 228a-b that define a central aperture
230. The anterior element 222 may be rolled or compressed into a
low profile contracted state for implantation. Once introduced, the
anterior element is partially released from the contracted state
and attached to the pair of vertebral bodies adjacent to the
damaged disc 108. The anterior element 222 is preferably attached
by screws or other suitable mechanisms. Once attached, the anterior
element 222 is fully extended to its operative state and is capable
of bearing loads to provide stabilization to the vertebral
segments.
[0072] The anterior stabilization device 220 may be used alone, in
combination with the posterior stabilization device 210 illustrated
in FIG. 9A, or in combination with any other suitable stabilization
device or structure. By using a combination of stabilization
devices, it may be possible to provide additional amounts or types
of stabilization and unloading of the vertebral segment than is
possible by use of only a single stabilization structure.
[0073] Turning now to FIGS. 10A-D, several embodiments of a
posterior dynamic stabilization device are shown. The dynamic
stabilization devices include a posterior spacer and one or more
restrictor bands. As explained below, the spacer may be integrated
with the restrictor band(s), or it may be provided independently of
the restrictor band(s).
[0074] Turning first to FIG. 10A, a posterior spacer 240 is shown.
The posterior spacer 240 is generally in the shape of a short
cylinder, having a central through-hole 242 and an upper surface
244 and lower surface 246. The posterior spacer 240 may optionally
be provided in any other form or shape, as described more fully
below. The spacer 240 is preferably formed of a generally compliant
biocompatible material, such as a polyurethane, silicone, or other
suitable polymeric material. As shown in FIGS. 10B-D, the spacer
240 is generally located between the spinous processes of a pair of
adjacent vertebral bodies. The spacer maintains the spacing between
the vertebral bodies while allowing a desired amount of relative
motion between the two vertebral bodies.
[0075] The restrictor band(s) 250 are each preferably formed in a
continuous loop and are formed of a relatively elastic
biocompatible material, such as any number of elastomeric and/or
polymeric materials suitable for the purpose. The restrictor
band(s) 250 are linked to the posterior spine to provide both
stability and compliance. The band(s) 250 are attached either to
the lamina by way of attachment screws 252 or other suitable
attachment mechanisms (see FIG. 10C, or they are looped directly
onto the spinous processes 106 of the pair of vertebral bodies (see
FIGS. 10B, 10D). The materials, sizes, structures, and routing of
the restrictor band(s) 250 are able to be tailored to obtain a
desired type and degree of constraint. For example, a routing
pattern that is oriented relatively more diagonally, as in FIG.
10C, will provide more resistance to torsional movement than will a
routing pattern that is oriented more vertically, as in FIG. 10D.
Other routing variations are also possible, as will be recognized
by those skilled in the art.
[0076] Turning now to FIG. 11, another embodiment of a dynamic
spinal stabilization device is shown. The device includes a
construction and that provides the capability of adjusting the
performance characteristics of the stabilization device after it
has been implanted. In the illustrated embodiment, the spinal
stabilization device 260 includes a superior attachment member 262
and an inferior attachment member 264, for attachment to a superior
vertebral body 100 and an inferior vertebral body 100,
respectively. The superior attachment member 262 and inferior
attachment member 264 may be attached to the spinous processes 106
of the respective vertebral bodies 100, 102, as shown, or they may
be attached to the pedicles or other suitable portions of the
vertebral bodies. The attachment members 262, 264 preferably
comprise screws, although other attachment members may be used as
desired or as suitable. The stabilization device 260 includes one
or more spring elements 266 that each extend between and
interconnect the superior attachment member 262 and inferior
attachment member 264. Each spring element 266 is preferably formed
of nickel titanium alloy (Nitinol) or other suitable biocompatible
shape memory material. The shape and properties of each spring
element 266 are able to be altered at any time, either prior to
implantation or after implantation, by heating the spring element,
for example, using an electric current. The shape memory material
may be trained by a heating process to conform to a predetermined
shape upon being heated to a predetermined temperature, in a manner
known to those skilled in the art. Thus, the user is able to alter
the shape, size, or performance characteristics of the spring
elements 266 through application of heat to those members. For
example, leads may be placed in contact with the spring elements
266 under X-ray or other guidance after implantation in the spine
of a patient. Electric current is then supplied to the spring
elements 266 through the leads, allowing the user to alter the
size, shape, or performance characteristics of the spring
elements.
[0077] Although the spring elements 266 shown in the embodiment
illustrated in FIG. 11 are generally straight struts, the spring
elements 266 may alternatively be provided in any shape, size, or
orientation suitable for a given application.
[0078] Turning next to FIG. 12, another spinal stabilization device
is shown in a generally schematic representation. The spinal
stabilization device illustrated in FIG. 12 is adapted to transfer
loads from one motion segment to adjacent segments. Three adjacent
vertebral bodies 270, 272, and 274 are shown schematically in the
Figure. A pair of interconnected stabilization devices 276 are
attached to each of the three vertebral bodies. Each stabilization
device 276 includes a fixation element 278 attached to each
vertebral body and a linkage 280 extending between and attached to
each adjacent pair o fixation elements 278.
[0079] Each of the fixation elements 278 comprises a bearing
structure or similar mechanism that provides the capability of
rotating the attached linkage 280. This allows a first vertebral
segment, such as vertebral body 270, to be loaded in reaction to a
load placed upon the adjacent vertebral segments, such as vertebral
bodies 272 and 274: As a non-limiting example, when the lowest
vertebral body 274 moves to the right, as shown by arrow "A", the
transfer of this load through rotation of the fixation elements 278
imposing loading upon the attached linkages 280 influences the
upper vertebral body 270 to move to the left, as shown by arrow
"B". This movement is consistent with the natural movement of the
spine when the body twists. Compression and flexion loads are
transferred in a similar manner.
[0080] As noted above, each of the fixation elements 278 is
preferably in the form of a bearing or similar rotatable structure
that provides rotational movement as represented by the arrows "C".
The linkages 280 may comprise a spring element or multiple spring
elements having a size, shape, spring constant, and other
characteristics that provide the desired amount of load transfer in
response to rotation of the fixation elements 278. In addition,
although two stabilization devices 276 are shown in the Figure,
more or fewer devices may be used depending upon the degree of
stabilization needed or desired. The stabilization devices 276 may
also extend between more (e.g., four or more) or fewer (e.g., two)
adjacent vertebral segments.
[0081] Turning next to FIG. 13, a multi-component dynamic
stabilization system is shown schematically. Current dynamic spinal
stabilization systems are typically either interspinous devices
(i.e., connected between the spinous processes of adjacent
vertebral bodies) or pedicle screw based devices (i.e., connected
between pedicle screws attached to the pedicles of adjacent
vertebral bodies). Each of these types of dynamic stabilization
devices functions by providing a distracting force that unloads the
disc 108. The system shown in FIG. 13 includes an interspinous
stabilization system 290 connected to the spinous processes 106 of
a pair of adjacent vertebral bodies 100, 102, and a pair of pedicle
based stabilization systems 292a -b (only one of the pedicle based
systems is shown in the Figure) attached by pedicle screws to the
pair of adjacent vertebral bodies 100, 102 on each side of the
spinous processes. Each of the pedicle based systems 292a -b
comprises a spring loaded or other suitable structure that provides
a distracting force, represented by arrows "D", that tends to
unload the disc 108. The interspinous system 290, on the other
hand, includes a spring loaded or other suitable structure that
biases the spinous processes 106 of the adjacent vertebral bodies
100, 102 toward one another, as represented by arrows "E". The
combined action of the interspinous system 290 and the pedicle
based systems 292a -b creates a moment that relives pressure from
the disc 108.
[0082] Advantageously, the interspinous system 290 and/or the
pedicle based systems 292a -b of the foregoing embodiment may be
constructed such that one or more of the systems is externally
adjustable, as described, for example, in relation the devices
illustrated in FIG. 11.
[0083] Turning next to FIG. 14, a pair of adjacent vertebral bodies
100, 102 are shown. A dynamic stabilization device 300 is attached
to each of the vertebral bodies at a position at or near the
transverse processes 104a-b of each vertebral body 100, 102. Each
dynamic stabilization device 300 includes an upper attachment screw
302 and a lower attachment screw 304. The screws 302, 304 may be
placed through the transverse process to the vertebral body, or
they may be attached direction to the vertebral body adjacent the
transverse process 104a-b. A loading member 306 is attached to each
of the upper attachment screw 302 and the lower attachment screw
304 and extends therebetween. The loading member 306 is adapted to
stabilize the adjacent vertebral bodies by providing an appropriate
level of distraction or attraction forces. The loading member 306
may comprises a spring, a set of springs, a damping member, or any
other suitable structure such as those described elsewhere
herein.
[0084] FIG. 15 provides a schematic illustration of an externally
adjustable dynamic stabilization system. The system includes an
upper screw 310 and lower screw 312 extending posteriorly from a
superior vertebral body 100 and an inferior vertebral body 102,
respectively. Each screw extends outside of the patient's body. A
stabilization member 314 is attached to each of the screws 310, 312
on the external surface of the patient's back, i.e., outside the
surface of the skin 316. The stabilization member 316 may be a
spring loaded, multiple spring loaded, damping mechanism, or any
other suitable stabilization system such as those described
elsewhere herein. Advantageously, the stabilization system 316 is
readily adjustable post-operatively because it is located
externally of the patient. Accordingly, any adjustments to the
performance of the system may be made easily and without the need
for additional surgical intervention.
[0085] FIG. 16 is a schematic illustration of another adjustable
stabilization system. The spinal stabilization system 320 includes
an upper pot 322 attached to the spinous process 106 of a superior
vertebral body 100, and a lower pot 324 attached to the spinous
process 106 of an inferior vertebral body 102. Each of the upper
pot 322 and lower pot 324 forms a portion of the attachment
mechanism for the stabilization device. The upper pot 322 and lower
pot 324 may be attached to the spinous processes 106 by any
suitable mechanism, such as one or more screws. Each of the upper
pot 322 and lower pot 324 includes a cylindrical portion that is
adapted to receive a connector 326 located at each of the upper end
and lower end of a spring 328. Each of the connectors 326 engages
one of the upper pot 322 and lower pot 324, thereby allowing the
spring 328 to provide a distracting force to the vertebral bodies
100, 102.
[0086] Because the upper pot 322 and lower pot 324 are generally
hollow, it is possible to partially fill one or both of the pots
322, 324 to decrease the effective length of the spring 328
extending between the pots, i.e., partially filling the pots causes
the connectors to engage the filler material at a level removed
from the bottom of the pot 322, 324. Either or both of the pots
322, 324 may be partially filled with bone cement containing
polymethylmethacrylate (PMMA) or another suitable material.
Preferably, the filling operation may be performed post-operatively
by way of a percutaneous access, thereby eliminating the need for
additional surgical intervention.
[0087] FIG. 17 provides an illustration of another dynamic
stabilization system. The stabilization system 340 includes a
DIAM.TM. type intervertebral spacer 342 interposed between the
spinous processes 106 of a pair of adjacent vertebral bodies 100,
102. DIAM.TM. type intervertebral spacers are commercially
available and are produced by Medtronic Sofamor Danek. The spacer
342 is generally "H" shaped, including a relatively narrow center
section located between relatively wider side sections. This shape
allows the spacer to be effectively sandwiched between the spinous
processes 106 of a pair of adjacent vertebral bodies 100, 102, as
shown in FIG. 17. The spacer 342 is a silicone device covered with
polyethylene, and functions by reducing loading of the disc,
restoring the posterior tension band, realigning the facets, and
restoring the foramenal height.
[0088] In addition, a stabilizing disc 344 is interposed between
the spinous processes 106 in place of a portion of the spacer 340.
The stabilizing disc 344 has a structure and is constructed in a
manner identical to the facet stabilizing member 170 described
above in relation to FIG. 5, having a core member located between a
pair of endplates. The stabilizing disc 344 allows for compression.
and rotation, if needed. The stabilizing disc 344 also facilitates
lateral bending.
[0089] As noted above, this application incorporates by reference
U.S. Provisional Patent Application Ser. No. 60/713,671, entitled
"Prosthetic Intervertebral Discs," ("the '671 application"), which
was filed Sep. 1, 2005, and which is assigned to Spinal Kinetics,
Inc., the assignee of the present application. The '671 application
describes, inter alia, spinal treatment methods that combine a
prosthetic intervertebral disc with a dynamic stabilization system.
Each of the dynamic stabilization systems described in the present
application are suitable for use in combination with prosthetic
intervertebral discs such as those described in the '671
application, and others described in U.S. patent application Ser.
No. 10/903,276, filed Jul. 30, 2004, ("the '276 application"),
which is also incorporated by reference herein.
[0090] For example, an exemplary prosthetic intervertebral disc
1100 is shown in FIG. 18, which is reproduced from FIG. 3 of the
'671 application and which was also described in the '276
application. This prosthetic disc is described for exemplary
purposes, and is not intended to represent the only type of
prosthetic disc that is suitable for use in combination with the
devices and systems described elsewhere herein. Turning to the
Figure, the prosthetic disc 1100 has an integrated structure that
includes an upper endplate 1110, a lower endplate 1120, and a core
member 1130 retained between the upper endplate 1110 and the lower
endplate 1120. One or more fibers 1140 are wound around the upper
and lower endplates to attach the endplates to one another. The
wind of the fibers 1140 allows a degree of axial rotation, bending,
flexion, and extension by and between the endplates. An annular
capsule 1150 is optionally provided in the space between the upper
and lower endplates, surrounding the core member 1130 and the
fibers 1140. The upper endplate 1110 and lower endplate 1120 are
generally flat, planar members, and are fabricated from a
biocompatible material that provides substantial rigidity.
[0091] The upper surface of the upper endplate 1110 and the lower
surface of the lower endplate 1120 are preferably each provided
with a mechanism for securing the endplate to the respective
opposed surfaces of the upper and lower vertebral bodies between
which the prosthetic disc is to be installed. For example, in FIG.
18, the upper endplate 1110 includes a plurality of anchoring fins
1111a-b. The anchoring fins 1111a-b are intended to engage mating
grooves that are formed on the surfaces of the upper and lower
vertebral bodies to thereby secure the endplate to its respective
vertebral body. The anchoring fins 1111a-b extend generally
perpendicularly from the generally planar external surface of the
upper endplate 1110, i.e., upward from the upper side of the
endplate as shown in FIG. 18. Each of the anchoring fins 1111a-b
has a plurality of serrations 1112 located on the top edge of the
anchoring fin. The serrations 1112 are intended to enhance the
ability of the anchoring fin to engage the vertebral body and to
thereby secure the upper endplate 1110 to the spine.
[0092] Similarly, the lower surface of the lower endplate 1120
includes a plurality of anchoring fins 1121a-b . The anchoring fins
1121a-b on the lower surface of the lower endplate 1120 are
identical in structure and function to the anchoring fins 1111a-b
on the upper surface of the upper endplate 1110, with the exception
of their location on the prosthetic disc.
[0093] The anchoring fins 1111, 1121 may optionally be provided
with one or more holes or slots 1115, 1125. The holes or slots help
to promote bony ingrowth that assist in anchoring the prosthetic
disc 1100 to the vertebral bodies.
[0094] The upper endplate 1110 contains a plurality of slots 1114
through which the fibers 1140 may be passed through or wound, as
shown. The actual number of slots 1114 contained on the endplate is
variable. The purpose of the fibers 1140 is to hold the upper
endplate 1110 and lower endplate 1120 together and to limit the
range-of-motion to mimic the range-of-motion and torsional and
flexural resistance of a natural disc.
[0095] The core member 1130 is intended to provide support to and
to maintain the relative spacing between the upper endplate 1110
and lower endplate 1120. The core member 1130 is made of a
relatively compliant material, for example, polyurethane or
silicone, and is typically fabricated by injection molding. A
preferred construction for the core member includes a nucleus
formed of a hydrogel and an elastomer reinforced fiber annulus. The
shape of the core member 1130 is typically generally cylindrical or
bean-shaped, although the shape (as well as the materials making up
the core member and the core member size) may be varied to obtain
desired physical or performance properties. For example, the core
member 1130 shape, size, and materials will directly affect the
degree of flexion, extension, lateral bending, and axial rotation
of the prosthetic disc.
[0096] The annular capsule 1150 is preferably made of polyurethane
or silicone and may be fabricated by injection molding, two-part
component mixing, or dipping the endplate-core-fiber assembly into
a polymer solution. A function of the annular capsule is to act as
a barrier that keeps the disc materials (e.g., fiber strands)
within the body of the disc, and that keeps natural in-growth
outside the disc.
[0097] The foregoing prosthetic disc 1100, or other suitable
prosthetic discs, may be implanted by surgical techniques described
in the '671 and '276 applications and elsewhere. As described
above, it will often be advantageous to combine the prosthetic
intervertebral disc with any of the other devices, systems, and
methods described herein to obtain synergistic therapeutic results
in treatment of spinal disease, trauma, or other disorder.
[0098] Accordingly, it is to be understood that the inventions that
are the subject of this patent application are not limited to the
particular embodiments described, as such may, of course, vary. In
particular, it is specifically contemplated that two or more of the
specific embodiments described herein may be combined, to the
extent that the embodiments are compatible with one another. Such
combinations provide performance benefits that exceed those
available to known devices or devices utilized independently.
[0099] Unless defined otherwise, all technical arid scientific
terms used herein have the same meaning as commonly understood by
one of ordinary skill in the art to which these inventions belong.
Although any methods and materials similar or equivalent to those
described herein can also be used in the practice or testing of the
present inventions, the preferred methods and materials are herein
described.
[0100] All patents, patent applications, and other publications
mentioned herein are hereby incorporated herein by reference in
their entireties. The patents, applications, and publications
discussed herein are provided solely for their disclosure prior to
the filing date of the present application. Nothing herein is to be
construed as an admission that the present invention is not
entitled to antedate such publication by virtue of prior invention.
Further, the dates of publication provided may be different from
the actual publication dates which may need to be independently
confirmed.
[0101] As will be apparent to those of skill in the art upon
reading this disclosure, each of the individual embodiments
described and illustrated herein has discrete components and
features which may be readily separated from or combined with the
features of any of the other several embodiments without departing
from the scope or spirit of the present inventions.
[0102] The preceding merely illustrates the principles of the
invention. It will be appreciated that those skilled in the art
will be able to devise various arrangements which, although not
explicitly described or shown herein, embody the principles of the
invention and are included within its spirit and scope.
Furthermore, all examples and conditional language recited herein
are principally intended to aid the reader in understanding the
principles of the invention and the concepts contributed by the
inventors to furthering the art, and are to be construed as being
without limitation to such specifically recited examples and
conditions. Moreover, all statements herein reciting principles,
aspects, and embodiments of the invention as well as specific
examples thereof, are intended to encompass both structural and
functional equivalents thereof. Additionally, it is intended that
such equivalents include both currently known equivalents and
equivalents developed in the future, i.e., any elements developed
that perform the same function, regardless of structure. The scope
of the present invention, therefore, is not intended to be limited
to the exemplary embodiments shown and described herein. Rather,
the scope and spirit of present invention is embodied by the
appended claims.
* * * * *