U.S. patent application number 15/864126 was filed with the patent office on 2018-07-12 for spinous process implants and associated methods.
The applicant listed for this patent is Zimmer Biomet Spine, Inc.. Invention is credited to Michael Fulton, Andrew Lamborne, Jeffrey J. Thramann.
Application Number | 20180193065 15/864126 |
Document ID | / |
Family ID | 39636540 |
Filed Date | 2018-07-12 |
United States Patent
Application |
20180193065 |
Kind Code |
A1 |
Lamborne; Andrew ; et
al. |
July 12, 2018 |
SPINOUS PROCESS IMPLANTS AND ASSOCIATED METHODS
Abstract
The present invention provides spinous process implant and
associated methods. In one aspect of the invention the implant
limits the maximum spacing between the spinous processes. In
another aspect of the invention, a spacer has at least one
transverse opening to facilitate tissue in-growth. In another
aspect of the invention, an implant includes a spacer and separate
extensions engageable with the spacer. The spacer is provided in a
variety of lengths and superior to inferior surface spacings. In
another aspect of the invention, an implant includes a spacer and a
cerclage element offset from the midline of the spacer in use so
that the spacer defines a fulcrum and the cerclage element is
operative to impart a moment to the vertebrae about the spacer. In
another aspect of the invention, instrumentation for inserting the
implant is provided. In other aspects of the invention, methods for
treating spine disease are provided.
Inventors: |
Lamborne; Andrew; (Golden,
CO) ; Fulton; Michael; (Superior, CO) ;
Thramann; Jeffrey J.; (Longmont, CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Zimmer Biomet Spine, Inc. |
Westminster |
CO |
US |
|
|
Family ID: |
39636540 |
Appl. No.: |
15/864126 |
Filed: |
January 8, 2018 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
15242960 |
Aug 22, 2016 |
9861400 |
|
|
15864126 |
|
|
|
|
13460738 |
Apr 30, 2012 |
|
|
|
15242960 |
|
|
|
|
11934604 |
Nov 2, 2007 |
8241330 |
|
|
13460738 |
|
|
|
|
60912273 |
Apr 17, 2007 |
|
|
|
60884581 |
Jan 11, 2007 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 17/842 20130101;
A61B 17/7068 20130101; A61B 2017/00477 20130101; A61B 17/7061
20130101 |
International
Class: |
A61B 17/70 20060101
A61B017/70; A61B 17/84 20060101 A61B017/84 |
Claims
1-15. (canceled)
16. An implant for placement between spinous processes of adjacent
vertebrae of a spine, the implant comprising: a cylindrical hollow
spacer with a first end, a second end, and a longitudinal axis
extending from the first end to the second end, the spacer
comprising superior and inferior surfaces operable to abut the
spinous processes and maintain minimum spacing between spinous
processes; a first extension integral with and projecting from the
first end of the cylindrical hollow spacer transverse to the
longitudinal axis to lie generally alongside the spinous processes
of adjacent vertebrae, the first extension including a first lobe
extending superiorly long a first extension axis and a second lobe
extending inferiorly long a second extension axis, wherein the
first extension axis is offset anteriorly from the second extension
axis; and a second extension slidably engageable with the
cylindrical hollow spacer opposing the first extension, the second
extension including a third lobe extending superiorly long a third
extension axis and a fourth lobe extending inferiorly long a fourth
extension axis, wherein the third extension axis is offset
anteriorly from the fourth extension axis, and wherein the third
lobe aligns opposite the first lobe engaging a first spinous
process of a first vertebrae and the fourth lobe aligns opposite
the second lobe engaging a second spinous process of a second
vertebrae.
17. The implant of claim 16, wherein the cylindrical hollow spacer
includes at least one channel running along a length of the spacer
aligned with the longitudinal axis and exposing an inner portion of
the cylindrical hollow spacer to facilitate tissue in-growth into
the cylindrical hollow spacer.
18. The implant of claim 17, wherein the second extension includes
a body with a c-shaped aperture for receiving the cylindrical
hollow spacer.
19. The implant of claim 18, wherein the c-shaped aperture includes
a tab extending radially inward and engaging the at least one
channel running along the length of the cylindrical hollow
spacer.
20. The implant of claim 16, wherein the second extension includes
set screw adapted to engage a posterior side of the cylindrical
hollow spacer.
21. The implant of claim 16, wherein the first lobe and third lobe
are offset anteriorly relative to the second lobe and the fourth
lobe to allow the extensions of multiple implants to be interleaved
on common interspinous processes.
22. The implant of claim 16, wherein the first extension includes
at least one fastener adapted to engage at least one of the spinous
processes to fix the cylindrical hollow spacer between the spinous
processes.
23. 8. The implant of claim 16, wherein the second extension
includes at least one fastener adapted to engage at least one of
the spinous processes to fix the cylindrical hollow spacer between
the spinous processes.
24. The implant of claim 16, wherein the first extension and the
second extension both include a plurality of fasteners, wherein a
first portion of the plurality of fasteners on the first extension
are adapted to be offset relative to a second portion of the
plurality of fasteners on the second extension when the plurality
of fasteners are engaged with the spinous processes.
25. An implant system for placement between spinous processes of
adjacent vertebrae of a spine, the system comprising: a first
implant spanning a first spinous process on a first vertebrae and a
second spinous process on a second vertebrae, the first implant
comprising: a first spacer with a first end, a second end, a hollow
cylindrical body, and a longitudinal axis extending from the first
end to the second end, the spacer comprising superior and inferior
surfaces operable to abut the first spinous process and the second
spinious process to maintain minimum spacing between the first
spinous process and the second spinous process; a first extension
integral with and projecting from the first end of the first spacer
transverse to the longitudinal axis, the first extension including
a first lobe extending superiorly long a first extension axis to
engage the first spinous process and a second lobe extending
inferiorly long a second extension axis to engage the second
spinous process, wherein the first extension axis is offset
anteriorly from the second extension axis; and a second extension
slidably engageable with the spacer opposing the first extension,
the second extension including a third lobe extending superiorly
long a third extension axis to engage the first spinous process
opposite the first lobe and a fourth lobe extending inferiorly long
a fourth extension axis to engage the second spinous process
opposite the second lobe; and a second implant spanning the second
spinous process on the second vertebrae and a third spinous process
on a third vertebrae, the second implant comprising: a second
spacer with a first end, a second end, a hollow cylindrical body,
and a second longitudinal axis extending from the first end to the
second end, the second spacer comprising superior and inferior
surfaces operable to abut the second spinous process and the third
spinious process to maintain minimum spacing between the second
spinous process and the third spinous process; a third extension
integral with and projecting from the first end of the second
spacer transverse to the second longitudinal axis, the third
extension including a fifth lobe extending superiorly long a fifth
extension axis to engage the second spinous process adjacent to the
second lobe and a sixth lobe extending inferiorly long a sixth
extension axis to engage the third spinous process, wherein the
fifth extension axis is offset anteriorly from the sixth extension
axis; and a fourth extension slidably engageable with the second
spacer opposing the third extension, the fourth extension including
a seventh lobe extending superiorly long a seventh extension axis
to engage the second spinous process adjacent the fourth lobe and a
eighth lobe extending inferiorly long an eighth extension axis to
engage the third spinous process opposite the sixth lobe.
26. The implant system of claim 25, wherein at least one of the
first spacer and the second spacer includes at least one channel
running along a length of the first spacer or second spacer aligned
with the longitudinal axis and exposing an inner portion of the
first spacer or second spacer to facilitate tissue in-growth.
27. The implant system of claim 26, wherein the second extension or
third extension includes a body with a c-shaped aperture for
receiving the first spacer or second spacer.
28. The implant system of claim 27, wherein the c-shaped aperture
includes a tab extending radially inward and engaging the at least
one channel running along the length of the first spacer or the
second spacer.
29. The implant system of claim 25, wherein the second extension
includes set screw adapted to engage a posterior side of the first
spacer.
30. The implant of claim 25, wherein the second lobe and fourth
lobe are offset posteriorly relative to the fifth lobe and the
seventh lobe to allow the first extension and second extension to
interleave with the third extension and the fourth extension.
31. The implant system of claim 30, wherein the second lobe and the
fifth lobe engage a first side of the second spinous process and
the fourth lobe and the seventh lobe engage a second side of the
second spinous process.
32. The implant system of claim 25, wherein the first extension
includes at least one fastener adapted to engage at least one of
the spinous processes to fix the first spacer to the spinous
processes.
33. The implant system of claim 25, wherein the second extension
includes at least one fastener adapted to engage at least one of
the spinous processes to fix the first spacer to the spinous
processes.
34. The implant system of claim 25, wherein the first extension and
the second extension both include a plurality of fasteners, wherein
a first portion of the plurality of fasteners on the first
extension are adapted to be offset relative to a second portion of
the plurality of fasteners on the second extension when the
plurality of fasteners are engaged with the spinous processes.
35. An implant for placement between spinous processes of adjacent
vertebrae of a spine, the implant comprising: a hollow spacer with
a medial end, a lateral end, and a longitudinal axis extending from
the medial end to the lateral end, the spacer comprising opposing
surfaces operable to abut the spinous processes and maintain
minimum spacing between spinous processes; a first extension
integral with and projecting from the medial end of the spacer
transverse to the longitudinal axis to lie generally alongside the
spinous processes of adjacent vertebrae, the first extension
including a first lobe extending superiorly long a first extension
axis and a second lobe extending inferiorly long a second extension
axis, wherein the first extension axis is offset anteriorly from an
intersection with the longitudinal axis and the second extension
axis is offset posteriorly from an intersection with the
longitudinal axis; and a second extension slidably engageable with
the spacer opposing the first extension, the second extension
including a third lobe extending superiorly long a third extension
axis and a fourth lobe extending inferiorly long a fourth extension
axis, wherein the third extension axis is offset anteriorly in line
with the first extension axis and the fourth extension axis is
offset posteriorly in line with the second extension axis.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 11/934,604, filed Nov. 2, 2007, which claims
the benefit of U.S. Provisional Application No. 60/912,273, filed
Apr. 17, 2007 and U.S. Provisional Application No. 60/884,581,
filed Jan. 11, 2007.
FIELD OF THE INVENTION
[0002] The present invention relates to spinous process implants
and associated methods.
BACKGROUND
[0003] The vertebrae of the human spine are arranged in a column
with one vertebra on top of the next. An intervertebral disc lies
between adjacent vertebrae to transmit force between the adjacent
vertebrae and provide a cushion between them. The discs allow the
spine to flex and twist. With age, spinal discs begin to break
down, or degenerate resulting in the loss of fluid in the discs and
consequently resulting in them becoming less flexible. Likewise,
the disks become thinner allowing the vertebrae to move closer
together. Degeneration may also result in tears or cracks in the
outer layer, or annulus, of the disc. The disc may begin to bulge
outwardly. In more severe cases, the inner material of the disc, or
nucleus, may actually extrude out of the disc. In addition to
degenerative changes in the disc, the spine may undergo changes due
to trauma from automobile accidents, falls, heavy lifting, and
other activities. Furthermore, in a process known as spinal
stenosis, the spinal canal narrows due to excessive bone growth,
thickening of tissue in the canal (such as ligament), or both. In
all of these conditions, the spaces through which the spinal cord
and the spinal nerve roots pass may become narrowed leading to
pressure on the nerve tissue which can cause pain, numbness,
weakness, or even paralysis in various parts of the body. Finally,
the facet joints between adjacent vertebrae may degenerate and
cause localized and/or radiating pain. All of the above conditions
are collectively referred to herein as spine disease.
[0004] Conventionally, surgeons treat spine disease by attempting
to restore the normal spacing between adjacent vertebrae. This may
be sufficient to relieve pressure from affected nerve tissue.
However, it is often necessary to also surgically remove disc
material, bone, or other tissues that impinge on the nerve tissue
and/or to debride the facet joints. Most often, the restoration of
vertebral spacing is accomplished by inserting a rigid spacer made
of bone, metal, or plastic into the disc space between the adjacent
vertebrae and allowing the vertebrae to grow together, or fuse,
into a single piece of bone. The vertebrae are typically stabilized
during this fusion process with the use of bone plates and/or
pedicle screws fastened to the adjacent vertebrae.
[0005] Although techniques for placing intervertebral spacers,
plates, and pedicle screw fixation systems have become less
invasive in recent years, they still require the placement of
hardware deep within the surgical site adjacent to the spine.
Recovery from such surgery can require several days of
hospitalization and long, slow rehabilitation to normal activity
levels.
[0006] More recently, investigators have promoted the use of motion
preservation implants and techniques in which adjacent vertebrae
are permitted to move relative to one another. One such implant
that has met with only limited success is the artificial disc
implant. These typically include either a flexible material or a
two-piece articulating joint inserted in the disc space. Another
such implant is the spinous process spacer which is inserted
between the posteriorly extending spinous processes of adjacent
vertebrae to act as an extension stop and to maintain a minimum
spacing between the spinous processes when the spine is in
extension. The spinous process spacer allows the adjacent spinous
processes to move apart as the spine is flexed.
SUMMARY
[0007] The present invention provides a spinous process implant and
associated methods.
[0008] In one aspect of the invention, an implant for placement
between spinous processes of adjacent vertebrae includes a spacer
and an extension. The spacer has sidewall generally parallel to its
longitudinal axis and having superior and inferior surfaces
operable to abut the spinous processes and maintain the spinous
processes in spaced apart relationship. The extension projects from
the spacer transverse to the longitudinal axis to lie generally
alongside the spinous processes of adjacent vertebrae and engage
the spinous processes to limit the maximum spacing between the
spinous processes.
[0009] In another aspect of the invention, the extension includes
an adjustable fastener.
[0010] In another aspect of the invention, the extension includes a
removable fastener.
[0011] In another aspect of the invention, an implant for placement
between spinous processes of adjacent vertebrae includes a spacer
having at least one transverse opening communicating from at least
one of a superior and inferior outer surface inwardly to facilitate
tissue in-growth.
[0012] In another aspect of the invention, the spacer includes a
hollow interior and a plurality of transverse openings
communicating from the superior and inferior outer surfaces to the
hollow interior to facilitate tissue, growth.
[0013] In another aspect of the invention, the spacer includes a
porous structure and the transverse openings comprise a plurality
of pores.
[0014] In another aspect of the invention, an implant for placement
between spinous processes of adjacent vertebrae of a spine includes
a spacer and separate extensions engageable with the spacer at its
ends. The spacer is provided in a variety of lengths and superior
to inferior surface spacings.
[0015] In another aspect of the invention, an implant for placement
between spinous processes of adjacent vertebrae of a spine includes
a spacer and a cerclage element. The cerclage element is offset
posteriorly of the midline in use so that the spacer defines a
fulcrum and the cerclage element is extendible around a portion of
a vertebra and operative to impart a moment to the vertebra about
the spacer.
[0016] In another aspect of the invention, instrumentation includes
two instruments each having a working portion tapering from a
larger cross-sectional dimension nearer a handle to a smaller
cross-sectional dimension near the free end. The free end of one of
the instruments defines a hollow tip sized to engage the free end
of the first instrument and sized to engage the hollow tip of the
implant.
[0017] In another aspect of the invention, a method includes
inserting a spacer between spinous processes of adjacent vertebrae
to provide both an extension stop and a flexion stop.
[0018] In another aspect of the invention, a method includes
inserting a spacer between spinous processes of adjacent vertebrae
and connecting a cerclage element to the adjacent vertebrae to
impart a moment to the vertebrae about the spacer.
[0019] In another aspect of the invention, a method includes
inserting a tapered instrument between adjacent spinous processes;
engaging a tip of a spinous process spacer with the tip of the
tapered instrument and passing the engaged pair back between the
adjacent spinous process to insert the spacer between the spinous
processes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Various examples of the present invention will be discussed
with reference to the appended drawings. These drawings depict only
illustrative examples of the invention and are not to be considered
limiting of its scope.
[0021] FIG. 1 is a cross sectional view of an implant according to
the present invention in situ;
[0022] FIG. 2 is a side elevational view of the implant of FIG. 1
in situ;
[0023] FIG. 3 is a an exploded perspective view of the implant of
FIG. 1;
[0024] FIG. 4 is a front elevational view of the implant of FIG.
1;
[0025] FIG. 5 is a back elevational view of the implant of FIG.
1;
[0026] FIG. 6 is a top plan view of the implant of FIG. 1;
[0027] FIG. 7 is a front elevational view of the implant of FIG. 1
showing the assembly in an alternate position;
[0028] FIG. 8 is a side elevational view of the implant of FIG.
1;
[0029] FIG. 9 is a perspective view of a pair of implants like that
of FIG. 1 in situ;
[0030] FIG. 10 is a cross sectional view of an implant like that of
FIG. 1 illustrating an alternate material and cerclage
elements;
[0031] FIGS. 11-13 are side elevational views of an implant like
that of FIG. 1 shown in use with cerclage elements;
[0032] FIGS. 14-24 are perspective views of alternative embodiments
of the invention;
[0033] FIG. 25 is a perspective view of instrumentation for
implanting the implant of FIG. 1;
[0034] FIG. 26 is a perspective view of the instrumentation of FIG.
25 in use to implant the implant of FIG. 1.
DESCRIPTION OF THE ILLUSTRATIVE EXAMPLES
[0035] Embodiments of spinous process implants according to the
present invention include a spacer and an extension extending
outwardly from the spacer. The spinous process implant may be
configured for insertion between adjacent spinous processes of the
cervical, thoracic, and/or lumbar spine. The spacer may be provided
in a variety of sizes to accommodate anatomical variation amongst
patients and varying degrees of space correction. The spacer may
include openings to facilitate tissue in-growth to anchor the
spacer to the vertebral bodies such as tissue in-growth from the
spinous processes. The spacer may be configured for tissue
in-growth from superior and inferior spinous processes to cause
fusion of the adjacent spinous processes. The openings may be
relatively large and/or communicate to a hollow interior of the
spacer. A hollow interior may be configured to receive bone growth
promoting substances such as by packing the substances into the
hollow interior. The openings may be relatively small and/or
comprise pores or interconnecting pores over at least a portion of
the spacer surface. The openings may be filled with bone growth
promoting substances.
[0036] The spacer may have any suitable cross-sectional shape. For
example, it may be cylindrical, D-shaped, C-shaped, H-shaped,
include separated cantilevered beams, and/or any other suitable
shape. The shape may include chamfers, fillets, flats, relief cuts,
and/or other features to accommodate anatomical features such as
for example the laminae and/or facets.
[0037] The extension may extend transversely from the spacer
relative to a spacer longitudinal axis to maintain the spacer
between adjacent spinous processes. A single extension may extend
in one or more directions or multiple extensions may be provided
that extend in multiple directions. One or more extensions may be
adjustable longitudinally relative to one another and/or the spacer
to allow the extensions to be positioned relative to the spinous
processes. A moveable extension may be provided that is movable
axially relative to the spacer and another extension.
Alternatively, a plurality of moveable extensions may be provided.
For example, the extensions may clamp against the sides of the
spinous processes to immobilize the spinous processes relative to
one another and promote fusion between the adjacent vertebrae. The
extensions may include fasteners engageable with the spinous
processes. The fasteners may include sutures, wires, pins, straps,
clamps, spikes, screws, teeth, adhesives, and/or other suitable
fasteners. The fasteners may be integrated into the extensions or
they may be modular. Modular fasteners may be adjustable,
replaceable, and/or removable to allow tailoring of the kind and
quality of fixation from rigid fixation to no fixation. The spacer,
extensions, and/or fasteners may advantageously be made of
different materials. For example, the spacer and extensions may be
made of a relatively softer material while the fasteners may be
made of a relative harder material. For example, the spacer and/or
extension may be made of a polymer and/or other relatively soft
material and the fastener may be made of a metal and/or other
relatively hard material.
[0038] Cerclage may be used to stabilize the spinous process
implant and/or to provide other benefits. For example, wires,
straps, bands, cables, cords, and/or other elongated members may
encircle the pedicles, laminae, spinous processes, transverse
processes, and/or other spinal structures. The cerclage may be
relatively inextensible to provide a hard check to spine flexion or
the cerclage may be relatively extensible to provide increasing
resistance to flexion. The cerclage may be relatively flexible and
drapeable such as a woven fabric or it may be relatively rigid such
as a metal band. The cerclage may have shape memory properties that
cause it to resume a prior set shape after implantation. The
cerclage may be independent of the spinous process implant or may
engage it. For example, the cerclage may pass through a hollow
interior of the spinous process implant and/or engage the
extension. The cerclage may be offset from the spacer and provide a
tensioning force that uses the spacer as a fulcrum to offload the
disc and/or open the disc space.
[0039] The implant may be supplemented with bone growth promoting
substances to facilitate fusion of adjacent vertebrae between
spinous processes, laminae, transverse processes, facets, and/or
other spinal structures. The bone growth promoting substances may
be spaced from the implant, placed adjacent the implant, sandwiched
between the implant and underlying bone, placed inside the implant,
coated onto the implant, and/or otherwise placed relative to the
implant. If it is coated onto the implant it may cover the entire
implant or only selected portions of the implant such as the
extensions, fasteners, spinous process contacting portions of the
spacer, and/or other portions.
[0040] As used herein, bone growth promoting substances may include
bone paste, bone chips, bone strips, structural bone grafts,
platelet derived growth factors, bone marrow aspirate, stem cells,
bone growth proteins, bone growth peptides, bone attachment
proteins, bone attachment peptides, hydroxylapatite, calcium
phosphate, and/or other suitable bone growth promoting
substances.
[0041] The implant and any associated cerclage or other components
may be made of any suitable biocompatible material including among
others metals, resorbable ceramics, non-resorbable ceramics,
resorbable polymers, and non-resorbable polymers. Some specific
examples include stainless steel, titanium and its alloys including
nickel-titanium alloys, tantalum, hydroxylapatite, calcium
phosphate, bone, zirconia, alumina, carbon, bioglass, polyesters,
polylactic acid, polyglycolic acid, polyolefins, polyamides,
polyimides, polyacrylates, polyketones, fluropolymers, and/or other
suitable biocompatible materials and combinations thereof.
[0042] The spinous process implant may be used to treat spine
disease in a variety of surgical techniques including superspinous
ligament sacrificing posterior approaches, superspinous ligament
preserving posterior approaches, lateral approaches, and/or other
suitable approaches. The spinous process implant may be used to
treat spine disease by fusing adjacent vertebrae or by preserving
motion between adjacent vertebrae. It may include only an extension
stop such as a spacer, only a flexion stop such as flexible
cerclage elements, or both a flexion and extension stop. The
spinous process implant may be used to reduce loads on the facet
joints, increase spinous process spacing, reduce loads on the disc,
increase anterior disc spacing, and/or otherwise treat spine
disease. Anterior effects may be accomplished by tensioning spine
elements posterior to the spacer to apply a mechanical advantage to
the spinal construct. Techniques for the spinal process implant may
include leaving the tissues at the surgical site unmodified or
modifying tissues such as trimming, rasping, roughening, and/or
otherwise modifying tissues at the implant site.
[0043] FIGS. 1 and 2 depict posterior and lateral views of a pair
of adjacent vertebrae of the lumbar spine 10. A superior vertebra
12 is separated from an inferior vertebra 14 by a disc 16. Each
vertebra includes a pair of transverse processes 18, 19, a
posteriorly projecting spinous process 20, 21, and a pair of
laminae 22, 23 connecting the transverse processes 18, 19 to the
spinous process 20, 21. In addition to the connection through the
disc 16, the vertebrae 12, 14 articulate at a pair of facet joints
24.
[0044] FIGS. 1-9 illustrate an exemplary spinous process implant
100. The implant 100 includes a spacer 102 positioned between the
spinous processes 20, 21. The height 104 of spacer 102 limits how
closely the spinous processes 20, 21 can move together. Thus, the
spacer 102 maintains a minimum distance between the spinous
processes 20, 21. In the case of spine disease involving posterior
subsidence of the adjacent vertebra, insertion of the spacer 102
between the spinous processes 20, 21 will move the vertebrae apart
and relieve pressure on nerve tissue and the facet joints 24.
[0045] As shown in FIG. 3, the spacer 102 includes a first end 106,
a second end 108, and a longitudinal axis 110 extending from the
first end to the second end. The spacer 102 has a sidewall 112,
generally parallel to the longitudinal axis 110, including superior
and inferior outer surfaces 114, 116. Transverse openings 118 (see
also FIG. 6) communicate from the superior and inferior outer
surfaces 114, 116 inwardly to facilitate tissue in-growth. The
exemplary spacer 102 includes a hollow interior 120 bounded by an
inner surface 122 such that the openings 118 communicate from the
outer surface to the hollow interior 120. Bone growth promoting
substances 124 are shown packed into the hollow interior 120 in
FIGS. 1 and 2 to promote fusion of the vertebrae 12, 14 by bone
growth between the spinous processes 20.
[0046] The spinous process implant 100 further includes a first
extension 126 projecting outwardly from the spacer 102 transverse
to the longitudinal axis 110 to lie generally alongside the
superior spinous process. Abutment of the first extension 126 with
the spinous process 20 helps to maintain the spacer 102 between the
spinous processes 20. In the exemplary spinous process implant 100,
the first extension 126 is fixed relative to the spacer 102 and the
implant includes a second extension 128 mountable to the spacer for
axial movement relative to the first extension 126. The second
extension 128 may be moved toward the first extension 126 to
approximate the width of the spinous process 20 and better
stabilize the implant 100. It is fixed in place by tightening a set
screw 130 against the spacer 102. The extensions 126, 128 include
fasteners 132, 134, 136 projecting from the extensions 126, 128 to
engage the spinous process 20 to fix the spacer 102 to the spinous
process 20. FIG. 1 depicts additional bone growth promoting
substance in the form of a strips of bone 125 sandwiched between
the extensions 126, 128 along the sides of the spinous processes 20
to promote bone growth along the sides of the spinous processes to
further inhance fusion of the vertebrae 12, 14. The extensions 126,
128 preferably extend inferiorly (as shown) as well as superiorly
to optionally attach to the inferior spinous processes to
immobilize the spinous processes 20 relative to one another while
fusion takes place.
[0047] The fasteners 132, 134, and 136 may take any suitable form.
They may be made integral with the extensions 126, 128 such as by
machining or casting them with the extensions or they may be formed
separately and permanently attached to the extensions 126, 128.
Fastener 132 is a sharpened spike that threadably engages the
extension 126. The threaded engagement allows the fastener 132 to
be replaced with a different fastener 132. For example, the
fastener 132 may be replaced by one that has a different shape, a
different size, a different material, or a different surface
coating. The threaded engagement also allows the fastener 132 to be
adjusted to extend by varying amounts from the extension 126 to
vary how it engages the bone. Thus, the fastener 132 can be
adjusted to fit differently shaped bones or to penetrate into a
bone by varying amounts. For example, multiple threaded fasteners
132 can be adjusted to extend by different amounts to conform to
curved or angled bone. Finally, the threaded engagement allows the
user to remove the fastener 132 when fixation is not desired such
as when it is desired to use implant 100 in a non-fusion procedure
as an extension stop without limiting flexion.
[0048] Fasteners 134 and 136 are provided as multi-spike pods
allowing a plurality of spikes to be quickly adjusted, changed, or
omitted. Fastener 134 includes a non-circular tab 138 engageable
with a non-circular opening 140 in the extension 126. The
non-circular engagement prevents the fastener 134 from rotating.
The tab 138 may form a press-fit, snap-fit, or other suitable
engagement with the opening 140. The tab 138 may be further secured
by a supplemental screw 142. Fastener 136 includes a threaded shaft
144 threadably engaged with a base member 146 to allow the length
of the fastener 136 to be adjusted. The shaft 144 engages the
extension 126 in rotating and pivoting manner such that the
fastener 136 can be adjusted rotationally and angularly to engage
the bone surface. In the illustrative embodiment, the shaft 144
terminates in a spherical ball 148 that engages the opening 140 in
a ball-and-socket arrangement for three degrees of freedom.
However, any mechanism that allows any number of degrees of freedom
may be used. The fastener 136 may be allowed to move in use so that
as the extension 126 is pressed toward a bone the fastener 136
adjusts to the angle of the bone surface. The fastener 136 may also
be secured such as by screw 142 to adjust the tension in the joint
and/or to lock the fastener 136 in a predetermined orientation.
[0049] FIG. 4 illustrates the axial relationship of fasteners on
the opposing extensions 126, 128. In the illustrative implant 100,
the fasteners 132 at the top of the implant 100 are shown aligned
along a common axis 150. The fasteners 134 at the bottom of the
implant 100 are shown offset so that they can interleave if
necessary as they are pressed into a bone. Any combination of
fastener type, number, and alignment may be provided on the implant
100.
[0050] As seen in FIGS. 5 and 6, the ends 106, 108 of the spacer
102 include anterior chamfers 152. These chamfers 152 allow the
ends 106, 108 to clear posteriorly facing structures of the
vertebrae 12, 14 such as the facet joints 24. Also, as seen in
FIGS. 5 and 6, the spacer 102 is offset anteriorly relative to the
extensions 126, 128 such that the longitudinal axis 110 of the
spacer 102 is anterior of the midline 154 of the extensions 126,
128. The anterior offset of the spacer 102 allows it to fit deeply
between the spinous processes 20, 21 while the extensions 126, 128
fit alongside the spinous processes 20, 21.
[0051] As best seen in FIGS. 3 and 8, the second extension 128
defines an aperture 155 conforming generally to the cross-sectional
shape of the spacer 102. In the illustrative embodiment of FIGS.
1-9, the aperture 155 opens anteriorly to form a "C"-shape. Tabs
156 extend inwardly from the superior and inferior portions of the
aperture to slidingly engage elongated slots 158 in the superior
and inferior surfaces of the spacer 102. The second extension 128
can be translated longitudinally toward and away from the first
extension 126. Tightening the set screw 130 against the posterior
side 160 of the spacer 102 forces the tabs 156 posteriorly against
the sides of the slots 158 and locks the second extension 128 in
place longitudinally. The posterior side 160 of the spacer 102 may
be roughened as shown to better grip the set screw 130. The set
screw 130 may also dig into the surface of the spacer 102 upon
tightening to postitively grip the spacer 102. The aperture 155 may
conform closely to the spacer 102 to constrain the second extension
128 to generally parallel motion relative to the first extension
126. Alternatively, the aperture 155 may be larger than the spacer
102 by a predetermined amount to permit a predetermined amount of
angular adjustment of the second extension 128 relative to the
first extension 126 as shown in FIG. 7 to allow the extension 128
to adjust to the underlying bone surface.
[0052] As best seen in FIG. 8, the second extension 128 includes a
first lobe 161 having a first lobe centerline 162 and a second lobe
164 having a second lobe centerline 166. In the illustrative
embodiment, the first lobe centerline 162 and the second lobe
centerline 166 are parallel and spaced apart so that the second
extension 128 has a generally "Z"-shaped plan form. This shape
allows the extension of one implant 100 to interleave, if
necessary, with another implant 100 in a multilevel surgery as
shown in FIG. 9 to permit close spacing of the implants, and/or
longer extension lobes for more extensive bone engagement. In the
illustrative embodiment of FIGS. 1-9, the centerlines 162 and 166
are offset equidistantly from the midline 154 of the second
extension 128. The centerlines 162 and 166 may vary from parallel
and they may be offset asymmetrically to form different shapes to
accommodate different vertebral anatomy. For example, the shape may
be tailored for different portions of the spine 10. In the
illustrative embodiment of FIGS. 1-9, the first extension 126 has
the same shape as the second extension 128. However, the shape may
be varied between the first and second extensions 126, 128.
[0053] FIG. 10 depicts an implant 200 having a spacer 202 and first
and second extensions 204, 206. The spacer 202 includes pores 208
for tissue to grow into. The pores 208 may be individual openings
spaced from one another, interconnecting openings, or combinations
of individual and interconnecting openings. The spacer 202 may be a
monolithic block having uniform porosity throughout. Alternatively,
the spacer 202 may include an outer porous layer 210 and an inner
layer 212 of different composition. For example, the inner layer
212 may be solid, porous, hollow, or some other configuration. A
porous inner layer may have pores of a different size and/or
distribution than the outer layer 210. Similarly, any porous
portion may have uniform porosity or porosity that varies in pore
size or density. A variety of pore configurations are suitable.
Preferably the pore size is in the range of 1 .mu.m to 2 mm. More
preferably, the pore size is in the range of 1 .mu.m to 500 .mu.m.
Still more preferably, the pore size is in the range of 75 .mu.m to
3001 .mu.m. The pores may be produced by a variety of processes
such as sintering of particles; leaching a soluble component from
the material; matting, weaving, or otherwise combining fibers;
and/or by any other known process. The pore size may be tailored to
preferentially promote hard tissue growth, soft tissue growth, or a
combination of hard and soft tissue growth. The extensions 204, 206
may be solid or they may have large and/or small openings to
encourage bone growth in and/or around the extensions 204, 206. The
spacer 202 and/or extensions 204, 206 may also be coated as
previously described.
[0054] The extensions 204, 206 may be fixed and/or adjustable. In
the illustrative implant 200 of FIG. 10, the first extension 204 is
fixed to one end of the spacer 202 and the second extension 206 is
translatable along the spacer 202 to allow the extensions to be
placed adjacent the spinous processes. The extensions 204, 206 are
shown with optional spikes 214 that may engage the spinous
processes 20, 21 to fix the spinous processes 20, 21 relative to
one another.
[0055] FIG. 10 also depicts the use of cerclage in conjunction with
the implant 200. For example, one or more flexible bands 216 are
placed around the lamina 22, 23 to provide a flexion stop. The band
216 may help carry the load exerted on the spikes 214 during spine
flexion. Alternatively or in addition to the band 216, one or more
bands 218, 220 may be placed around the transverse processes 18,
19.
[0056] FIGS. 11-13 depict additional examples of the use of
cerclage in conjunction with a spinous process implant 300
according to the present invention. The implant includes a spacer
302 for placement between adjacent spinous processes 20, 21 and an
extension 304. In the example of FIG. 1, a band 310 of flexible
material is looped around the spinous processes 20, 21. By placing
the band 310 behind the areas 312, 314 where the spinous processes
contact the spacer 302 an offset 318 is created. Tightening of the
band 310 creates a moment 320, 322 on each vertebra 12, 14 that
offloads some of the pressure on the disc 16 between the adjacent
vertebrae 12, 14. With increased tightening of the band 310, the
anterior spacing 324 of the vertebrae 12, 14 may actually be
increased. Thus, by using the spinous process implant 300 in
combination with the band 310, the vertebrae 12, 14 may be levered
apart with the implant 300 being used as the fulcrum. In addition
to the advantages already mentioned, this combination produces an
anterior disc space effect with a posterior spinous process
procedure that is less invasive than typical disc spacing
procedures.
[0057] In the examples of FIGS. 12 and 13, the implant 300 includes
a mechanism for attaching the cerclage band 310 to the implant 300.
In the example of FIG. 12, the mechanism includes openings 330, 332
in the superior and inferior ends of the extension 304. By
attaching the band 310 to the extension 304, the band 310 and
extension 304 help stabilize one another against anterior-posterior
displacement. This attachment also helps position the band 310 at a
predetermined offset 318 from the spacer 302. In the example of
FIG. 13, the band 310 is looped through a hollow interior of the
spacer 302 itself. In this example, the band is not offset and
produces minimal or no moment on the vertebrae.
[0058] FIGS. 14-24 illustrate alternative mechanisms for attaching
a movable extension to the implant of FIG. 1. Referring to FIG. 14,
an implant 400 includes a spacer 402, a first extension 404 and a
second, movable extension 406. The movable extension 406 includes a
body in the form of a ring 408 with an inner surface 410 generally
conforming to the outer surface of the spacer 402 so that the ring
is slidingly receivable on the spacer 402. A set screw 412 is
tightened against the spacer 402 to fix the movable extension 406
at a desired position on the spacer 402. Tightening of the set
screw 412 biases the movable extension 406 posteriorly relative to
the spacer 402. The anterior portion 414 of the ring presses
against the anterior portion 416 of the spacer 402 to counter this
posterior bias and allow the set screw 412 to lock the extension
406. The spacer 402 may include a plurality of indentations 418 to
create a positive engagement with the set screw 412 at
predetermined axial locations. The ring 408 may be sized to permit
a predetermined amount of tilting of the extension 406 relative to
the spacer 402.
[0059] Referring to FIG. 15, an implant 500 includes a spacer 502,
a first extension 504, and a second, movable extension 506. The
spacer 502 includes a plurality of cantilevered beams 508, 510
projecting parallel to a longitudinal axis 512 away from the first
extension 504. In the example of FIG. 15, the spacer 502 includes a
pair of opposed "C"-shaped beams 508, 510 with their concave
surfaces directed inwardly. The spacer 502 includes openings 514
through the beams 508, 510 and defines elongated openings 516, 518
anteriorly and posteriorly between the beams. The movable extension
506 includes a body in the form of an interrupted ring 520. The
ring 520 is open anteriorly and the margins of the opening define
posteriorly directed hooks 522, 524. The inner surface 526 of the
ring conforms generally to the outer surface of the beams 508, 510
so that the ring is slidingly receivable on the spacer 502. The
open anterior configuration of the ring 520 provides clearance to
ease sliding of the ring in-vivo. A set screw 528 is tightened
against the spacer 502 to fix the movable extension 506 at a
desired longitudinal position on the spacer. The hooks 522, 524
curve around a portion of the anterior edge of the beams 508, 510
to resist posterior translation of the ring relative to the spacer
502 when the set screw 528 is tightened.
[0060] Referring to FIG. 16, an implant 600 is depicted that is
similar to implant 500 of FIG. 15 having a spacer 602, first
extension 604, and movable extension 606. However, the ring 608 is
truncated anteriorly to provide even more anterior clearance than
the ring 520 of FIG. 15. The ring 608 includes a key 610 projecting
anteriorly from the posterior side of the ring 608 and expanding
superiorly and inferiorly to engage the inner surface 612 of the
beams 614, 616 to resist posterior translation of the ring relative
to the spacer 602. The key 610 also partially blocks the hollow
interior 618 of the spacer 602 to help retain material optionally
packed into the interior 618.
[0061] Referring to FIG. 17, an implant 700 includes a spacer 702,
a first extension 704, and a second movable extension 706. The
spacer 702 includes a sidewall 708 defining an outer surface 710
and an inner surface 712. In the example of FIG. 17, the spacer 702
is generally in the shape of a hollow flattened cylinder with a
"D"-shaped cross section. However, the spacer 702 could be any
desirable shape. The spacer 702 includes a plurality of openings
714 communicating from the outer surface 710 to the inner surface
712. The movable extension 706 includes a projection 716 configured
generally like the spacer 702 but being sized to slide within the
spacer 702 in telescoping relationship. The projection (or the
spacer) may optionally include one or more fixation mechanisms to
lock the extensions 704, 706 at a desired longitudinal spacing.
Fixation mechanisms may include a set screw 718, a ridge 720
forming a snap fit with a groove 722 or other feature, a detent 724
engageable with openings 714, and/or other suitable fixation
mechanisms. Any one or combinations of these mechanisms may be used
and they may be reversed from the orientation shown.
[0062] Referring to FIGS. 18-20, an implant 800 includes a spacer
802, a first extension 804, and a second, movable extension 806.
The spacer 802 includes a plurality of cantilevered beams similar
to FIGS. 15 and 16 except that in this example there are three
beams 808, 810, 812. The beams project parallel to a longitudinal
axis 814 away from the first extension 804. In the example of FIG.
18, the anterior beam 812 includes a posteriorly opening groove
816. The posterior beams 808, 810 and anterior beam 812 define an
elongated slot 818 between them opening superiorly and inferiorly.
The posterior beams 808, 810 further define an elongated slot 820
between them opening posteriorly. FIG. 20 illustrates a cruciform
opening 822 defined by the projection of the groove 816 and slots
818, 820 projected through the first extension 804. The movable
extension 806 includes a body 824 sized to slidingly engage the
slot 818. An optional lug 826 can project anteriorly into groove
816 to constrain tilting of the movable extension 806 relative to
the first extension 804. The lug 826 can be sized to fit closely
within groove 816 to prevent tilting of the movable extension 806
or it can be sized smaller than the groove 816 to permit a
predetermined amount of tilt. A set screw 828 is provided to lock
the movable extension 806 to the spacer 802.
[0063] Referring to FIG. 21, an implant 900 is depicted that is
configured generally like that of FIG. 16. However, an end wall 902
adjacent the first extension 904 includes a through bore 906 and
the movable extension 908 includes a key 910 with a through bore
912. The bores 906, 912 receive a fastener to fix the extensions
904, 908 at a maximum spacing to prevent them from moving apart.
Fasteners may include screws, bolts, nuts, cables, wires, ties,
rods, and/or any other suitable fastener. In the example of FIG.
21, the fastener includes an elongated crimp receiving member 914,
such as a cable, and crimp members 916, 918, such as ferrules or
compressible beads.
[0064] Referring to FIG. 22, an implant 1000 includes a spacer
1002, a first extension 1004, and a second extension 1006. The
spacer 1002 includes an outer surface 1008 defining one or more
longitudinal grooves 1010 extending along the outer surface 1008
and through the first extension 1004. The first extension 1004
includes one or more corresponding slots 1012 having a radially
outwardly extending portion 1014 through the first extension 1004
and communicating with the grooves 1010. The slots 1012 have a
radially inwardly extending portion 1016 defining a shoulder 1018
at the end of the grooves 1010. The second extension 1006 includes
one or more corresponding projections 1020 projecting
longitudinally toward the first extension 1004 and terminating at a
radially inwardly directed tab 1022. The second extension 1006
further includes a centering bore 1024 having conical opening
engageable with a conical free end 1026 of the spacer 1002. The
second extension 1006 is attached to the spacer 1002 by pressing
the tabs 1022 against the conical end 1026 of the spacer 1002 to
spread the projections outwardly until the tabs 1022 engage the
grooves 1010. The tabs 1022 are slid along the grooves 1010 until
they exit through the slots 1012 and the tabs 1022 snap inwardly
over the shoulders 1018 and into the portions 1016. Abutment of the
tabs 1022 against the shoulders 1018 prevents the first and second
extensions 1004, 1006 from moving apart. The engagement of the
conical end 1026 of the spacer 1002 with the bore 1024 provides
radial stability to the assembly.
[0065] Referring to FIG. 23, an implant 1100 includes a spacer
1102, a first extension 1104, and a second extension 1106. The
spacer 1102 includes a transverse groove 1108 with a central boss
1110 having an enlarged head 1112. The second extension 1106
includes a portion 1114 sized to fit within the groove 1108 and an
opening 1116 bordered by one or more angled tabs 1118. The second
extension 1112 is assembled to the spacer by pressing the portion
1114 into the groove 1108 with the central boss 1110 directed into
the opening 1116. As the boss 1110 is pressed through the opening
1116, the tabs 1118 flex outwardly to allow it to pass. Once the
boss 1110 is past the tabs 1118, the tabs 1118 return to their
original position and snap behind the enlarged head 1112. In this
configuration, the boss 1110 retains the second extension 1106
longitudinally and the groove 1108 prevents the second extension
1106 from rotating about the longitudinal axis of the implant
1100.
[0066] Referring to FIG. 24, an implant 1200 includes a spacer
1202, a first extension 1204, and a second extension 1206. The
spacer 1202 includes a solid cylindrical sidewall 1208 defining a
hollow interior 1210. The extensions 1204, 1206 are similarly
configured and each includes a projection 1212, 1214 sized to fit
inside of the spacer 1202. The extensions 1204, 1206 may attach to
the spacer by press-fitting, snap-fitting, screwing, and/or
otherwise engaging the projections 1212, 1214 with the spacer 1202.
Alternatively, or additionally, the extensions 1204, 1206 may
attach to the spacer 1202 with any of the previously depicted
attachment mechanisms such as with a set screw as shown in FIG. 3
or an elongated fastener as shown in FIG. 21. In the example of
FIG. 24, the extensions 1204, 1206 are slotted longitudinally to
form flexible petals 1216 that press into the spacer 1202. The
extensions 1204, 1206 include openings 1218 to allow tissue growth,
permit attachment of cerclage members, and/or receive additional
fasteners attached to the spinous-processes.
[0067] The spacer 1202 of FIG. 24 could have openings as shown in
some of the other examples. Likewise, the other examples could have
a solid surface as shown in FIG. 24. Similarly the extensions of
any of the examples may be solid, have openings, or be otherwise
advantageously configured.
[0068] Implants according to the present invention may be implanted
using a variety of surgical approaches and techniques. Surgical
approaches may include superspinous ligament sacrificing posterior
approaches, superspinous ligament preserving posterior approaches,
lateral approaches, and/or other suitable approaches. Techniques
may include leaving the tissues at the surgical site unmodified or
modifying the tissues such as trimming, rasping, roughening, and/or
otherwise modifying them. For example, in FIG. 1, a lateral
approach is used and the inferior spinous process is cut on its
superior surface 26 to enlarge the interspinous space to receive
the implant 100. After the interspinous space is prepared, the
spacer 102 is inserted into the interspinous space. If a first
extension 126 is present it may be pressed inwardly to lie near or
abut one or more spinous processes. If a second extension 128 is
used, it is engaged with the spacer 102 and also optionally pressed
inwardly. In FIG. 1, opposing extensions 126, 128 having inwardly
directed bone fasteners have been used and pressed inwardly so that
the fasteners 132 engage the spinous processes 20, 21. The
engagement of the fasteners 132 with the inferior spinous process
21 is not shown in FIG. 1 because the extensions are offset
superiorly and inferiorly as shown in FIGS. 3, 8, and 9.
[0069] Referring to FIGS. 25 and 26, a set of instruments 1300 is
provided to facilitate lateral insertion of an implant into the
interspinous space. The set of instruments includes a plurality of
inserters 1302, 1303 in which each inserter 1302, 1303 has a first
or handle portion 1304 and a second or working portion 1306. The
working portion 1306 is insertable into the interspinous space.
Preferably, the handle portion 1304 extends transverse to the
working portion 1306 to facilitate holding and manipulating the
inserter 1302, 1303 while the working portion 1306 is in the
interspinous space. The handle portion 1304 and working portion
1306 may define a curve, angle, offset, and/or any other suitable
transverse orientation. In the example of FIG. 25, the inserters
1302, 1303 are generally "L"-shaped. The working portion 1306
tapers from a relatively larger cross-sectional dimension at a
first portion 1307 spaced away from its free end 1308 to a
relatively smaller cross-sectional dimension at its free end 1308.
In the illustrative embodiment, the working portion is conical and
tapers from a larger diameter to a smaller diameter. The end 1308
defines a hollow tip having an opening 1310. The set of instruments
1300 is provided with a plurality of similarly configured inserters
having differently sized working portions 1306 such that the end
1308 of one inserter 1302 will fit inside the opening 1310 at the
tip of another inserter 1303. Optionally, the working portion 1306
may be separated into opposing halves attached to opposing handles
1314, 1316. As the opposing handles 1314, 1316 are moved relative
to one another, the opposing halves of the working portion 1306
move relative to one another. In the illustrative embodiment,
squeezing the handles 1314, 1316 toward one another causes the
working portion 1306 to expand as the opposing halves of the
working portion 1306 open outwardly away from one another.
[0070] In use, a first inserter 1302 is inserted into the
interspinous space. The first inserter 1302 is relatively small to
ease insertion. As the end 1308 is inserted further, the tapered
working portion 1306 expands the interspinous space. Optionally,
the interspinous space can be further expanded by expanding the
working portion while it is inside the interspinous space such at
by squeezing the handles 1314, 1316. A second, larger inserter 1302
is engaged with the first inserter 1303 by placing its hollow tip
over the tip of the first inserter 1303 and then passing the
overlapping instruments back through the interspinous space to
remove the first inserter 1303 and insert the second inserter 1302.
As the end of the second inserter 1303 is inserted further, the
tapered working portion expands the interspinous space. Optionally,
the interspinous space can be further expanded by expanding the
working portion while it is inside the interspinous spaces.
Progressively larger inserters can be inserted in this fashion
until the interspinous space has been expanded to the desired size.
Once the desired size has been reached the appropriate implant size
may be determined by noting the size of the last inserter. The
inserter may optionally include indicia 1320 on the tapered working
end corresponding to different spacer sizes to further facilitate
sizing the implant. The implant is inserted by engaging the spacer
1402 with the working end of the inserter as shown in FIG. 26. The
implant may be engaged inside of the hollow tip of the inserter or
the tip of the inserter may engage a hollow tip on the implant as
shown. The spacer 1402 is pressed into the interspinous space as
the inserter is withdrawn.
[0071] Although examples of a spinous process implant and
associated instruments and techniques have been described and
illustrated in detail, it is to be understood that the same is
intended by way of illustration and example only and is not to be
taken by way of limitation. Accordingly, variations in and
modifications to the spinous process implant, instruments, and
technique will be apparent to those of ordinary skill in the art,
and the following claims are intended to cover all such
modifications and equivalents.
* * * * *