U.S. patent application number 13/461771 was filed with the patent office on 2012-11-22 for methods and apparatus for treating spinal stenosis.
This patent application is currently assigned to NuVasive Inc.. Invention is credited to Benjamin Arnold, Bret A. Ferree, Rich Mueller, Forrest Samuel, Andrew Schafer.
Application Number | 20120296377 13/461771 |
Document ID | / |
Family ID | 37986262 |
Filed Date | 2012-11-22 |
United States Patent
Application |
20120296377 |
Kind Code |
A1 |
Ferree; Bret A. ; et
al. |
November 22, 2012 |
Methods and Apparatus for Treating Spinal Stenosis
Abstract
This invention relates generally to spine surgery and, in
particular, to methods and apparatus for treating spinal
stenosis.
Inventors: |
Ferree; Bret A.;
(Cincinnati, OH) ; Mueller; Rich; (San Diego,
CA) ; Samuel; Forrest; (San Diego, CA) ;
Schafer; Andrew; (San Diego, CA) ; Arnold;
Benjamin; (San Diego, CA) |
Assignee: |
NuVasive Inc.
San Diego
CA
|
Family ID: |
37986262 |
Appl. No.: |
13/461771 |
Filed: |
May 1, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11540318 |
Sep 28, 2006 |
8167915 |
|
|
13461771 |
|
|
|
|
60722065 |
Sep 28, 2005 |
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Current U.S.
Class: |
606/249 ;
606/279 |
Current CPC
Class: |
A61B 2017/8655 20130101;
A61B 17/7053 20130101; A61B 17/7062 20130101 |
Class at
Publication: |
606/249 ;
606/279 |
International
Class: |
A61B 17/70 20060101
A61B017/70; A61B 17/88 20060101 A61B017/88 |
Claims
1-22. (canceled)
23. A system for treating spinal stenosis, comprising an implant,
the implant dimensioned to fit between a superior spinous process
and an inferior spinous process, the implant being configured to
promote fusion to the superior spinous process, the implant further
being configured to discourage fusion to the inferior spinous
process; and at least one of a tether, screw, clamp, and zip cable
to couple the implant to the superior spinous process.
24. The system of claim 0, wherein the implant includes at least
one aperture to allow bone to grow into the implant.
25. The system of claim 0, wherein the implant includes an interior
chamber in communication with the at least one aperture, the
chamber dimensioned to receive fusion inducing material one of
before and after coupling the implant to the spinous process.
26. The system of claim 0, wherein the fusion inducing material
includes any of Bone Morphogenic Protein, demineralized bone
matrix, allograft cancellous bone, autograft bone, hydroxy
appetite, and coral.
27. The system of claim 0, wherein the at least one aperture is
positioned such that it contacts the superior spinous process.
28. The system of claim 0 of, wherein the implant includes an
aperture for releasably attaching an insertion tool.
29. The system of claim 28, wherein the insertion tool includes a
pair of prongs that engage a pair of insertion apertures
dimensioned to receive the prongs.
30. The system of claim 29, wherein the implant includes at least
two pairs of apertures for engaging the insertion tool in different
orientations.
31. The system of claim 0, wherein the tether is one of a wire,
cable, suture, and allograft tissue.
32. The method of claim Error! Reference source not found., wherein
the implant includes at least one aperture dimension to receive the
tether and comprising the additional step of tying the tether each
of through the at least one aperture dimensioned to receive the
tether and the superior spinous process.
33. The system of claim 0, wherein a zip cable is used, the zip
cable including a cable, two bases and two locking pins, the cable
being dimension to wrap around the superior spinous process and
lockingly engage both bases.
34. The system of claim 0, wherein the implant includes a main
aperture to allow bone growth into the implant and at least one
secondary aperture to allow bone growth into the implant.
35. The system of claim 0, wherein the implant includes a notch
dimensioned to receive a portion of the superior spinous
process.
36. The system of claim 35, wherein the at least one aperture for
allowing bone to grow into the implant is positioned within the
notch.
37. The system of claim 36, wherein a second notch is positioned on
a bottom of the implant and is dimensioned to engage the inferior
spinous process.
38. The system of claim 0, wherein the implant is made of non-bone
material.
39. The system of claim 38, wherein the implant is made from one of
polyetheretherketone and polyetherketoneketone.
40. The system of claim 38, wherein the implant includes at least
one radio-opaque marker viewable using an imaging technique.
41. The system of claim 40, wherein the marker is positioned at the
center of the implant in a posterior-anterior direction, the marker
being alignable with a top portion of the superior spinous process
and inferior spinous process to ensure proper placement.
42. The system of claim 41, wherein additional markers are
positioned in sides of the implant, at least one side marker being
positioned in anterior aspect of the implant, the side marker in
the anterior aspect of the implant being alignable relative to the
spinal canal.
43. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 11/540,318, filed Sep. 28, 2006, now pending,
which claims the benefit of the filing date under 35 USC 119(e) of
provisional application entitled "Methods and Apparatus for
Treating Spinal Stenosis," Ser. No. 60/722,065, filed Sep. 28,
2005, the entire contents of which is fully incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] I. Field of the Invention
[0003] This invention relates generally to spine surgery and, in
particular, to methods and apparatus for treating spinal
stenosis.
[0004] II. Discussion of the Prior Art
[0005] Spinal stenosis is a narrowing of spaces in the spine which
results in pressure on the spinal cord and/or nerve roots. This
disorder usually involves the narrowing of one or more of the
following: (1) the canal in the center of the vertebral column
through which the spinal cord and nerve roots run, (2) the canals
at the base or roots of nerves branching out from the spinal cord,
or (3) the openings between vertebrae through which nerves leave
the spine and go to other parts of the body. Pressure on the spinal
cord and/or exiting nerve roots may give rise to pain or numbness
in the legs and/or arms depending on the location within the spine
(e.g. cervical, thoracic, lumbar regions). While spinal stenosis
generally afflicts those of advanced age, younger patients may
suffer as well.
[0006] A variety of treatments have been undertaken to alleviate or
minimize the effects of spinal stenosis. One such technique is a
laminectomy, which involves removing the lamina portion from the
pathologic region. By removing the lamina, this procedure enlarges
the spinal canal and thus relieves the pressure on the spinal chord
and/or compressed nerves. While generally effective, some consider
lamimectomy disadvantageous in that, as with any procedure
involving bone removal, the resulting region of the spine may be
further compromised from a mechanical standpoint. Moreover, elderly
patients frequently have co-morbidities that increase the
likelihood of complications, such as increased back pain,
infection, and prolonged recovery.
[0007] Still other efforts at treating spinal stenosis involve
placing spacer devices within the inter-spinous space to indirectly
decompress the stenotic condition. These systems are characterized
by being secured at the superior and inferior spinous processes.
Having both ends of the spacer device coupled to the respective
spinous processes disadvantageously limits both flexion and
extension of the spine at that location, when it is believed that
limiting extension is the key to relieving spinal stenosis.
Moreover, the prior art inter-spinous spacers are typically
constructed from materials (e.g. metal) with properties
substantially different than that of the spinous processes
themselves, which raises questions of whether the spinous processes
will remodel around the spacer and thereby lose their ability to
distract and thereby alleviate spinal stenosis.
[0008] The present invention is directed at overcoming, or at least
improving upon, the disadvantages of the prior art.
SUMMARY OF THE INVENTION
[0009] The present invention is directed at treating spinal
stenosis involving an inter-spinous spacer dimensioned to distract
a stenotic inter-spinous space and further characterized as being
affixed to only one of the two adjacent spinous processes to
prevent spinal extension and allow spinal flexion. The
inter-spinous spacer of the present invention may be used in the
cervical, thoracic and/or lumbar spine. Although shown and
described throughout this disclosure with the inter-spinous spacer
affixed to the superior spinous process, it will be appreciated
that the inter-spinous spacer of the present invention may also be
affixed to the inferior spinous process without departing from the
scope of the invention. Various mechanisms may be used to affix the
inter-spinous spacer of the present invention to the given spinous
process, including but not limited to one or more tethers (e.g.
wire, cable, suture, allograft tissue, or other single or
multi-filament members), one or more screws and/or any of a variety
of clamping mechanisms.
[0010] According to an important aspect of the present invention,
the inter-spinous spacer of the present invention is designed to
fuse to the spinous process to which it is affixed over time,
resulting in what is called "hemi-fusion" in that the spacer will
be fused to only one spinous process. This is facilitated by
abrading the surface of the spinous process (to preferably cause
bleeding) where it will mate with the inter-spinous spacer of the
present invention. This junction will fuse over time based, in
part, on the fusion-enabling design and/or material of the
inter-spinous spacer of the present invention. More specifically,
the inter-spinous spacer of the present invention may be
constructed from bone (e.g. allograft) material, which is readily
known to enable fusion upon implantation. The inter-spinous spacer
may also be constructed from non-bone materials (e.g.
polyaryletheretherketone (PEEK) and/or polaryletherketoneketone
(PEKK)) which are physically designed to promote fusion. This is
accomplished, by way of example, by providing an interior lumen
within the inter-spinous spacer which is dimensioned to receive
fusion-inducing materials and which is in communication with the
abraded surface of the given spinous process. Such fusion-promoting
materials may include, but are not necessarily limited to BMP,
demineralized bone matrix, allograft cancellous bone, autograft
bone, hydroxy appetite, coral and/or other highly porous
substances.
[0011] The present invention overcomes the drawbacks of the prior
art by treating spinal stenosis while allowing spinal flexion with
an implant constructed from materials with properties substantially
closer to the properties of the spinous processes themselves than
prior art devices. This advantageously minimizes the risk of the
spinous processes remodeling around the inter-spinous spacer of the
present invention, which advantageously prevents and/or minimizes
the risk of a loss of distraction that may otherwise occur.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Many advantages of the present invention will be apparent to
those skilled in the art with a reading of this specification in
conjunction with the attached drawings, wherein like reference
numerals are applied to like elements and wherein:
[0013] FIG. 1 is a perspective view of an inter-spinous spacer
according to a first embodiment of the present invention in use
affixed to a superior spinous process of a human spine;
[0014] FIG. 2 is a perspective view of the inter-spinous spacer of
the present invention shown in FIG. 1;
[0015] FIG. 3 is a side view of the inter-spinous spacer of the
present invention as shown in FIG. 1;
[0016] FIG. 4 is a front view of the inter-spinous spacer of the
present invention as shown in FIG. 1;
[0017] FIG. 5 is a top view of the inter-spinous spacer according
to the present invention as shown in FIG. 1;
[0018] FIG. 6 is a cross-sectional view of the inter-spinous spacer
of the present invention as taken through lines A-A of FIG. 5;
[0019] FIG. 7 is a perspective view illustrating the inter-spinous
spacer shown in FIG. 1 with fusion-promoting materials disposed
within an inner lumen according to one aspect of the present
invention;
[0020] FIG. 8 is a perspective view of an inter-spinous spacer
according to a second embodiment of the present;
[0021] FIG. 9 is a side view of the inter-spinous spacer according
to the present invention as shown in FIG. 8;
[0022] FIG. 10 is an end view of the inter-spinous spacer according
to the present in invention as shown in FIGS. 8-9;
[0023] FIG. 11 is a perspective view of an inter-spinous spacer
according to a third embodiment of the present invention in use
affixed to a superior spinous process of a human spine;
[0024] FIG. 12. is a frontal view of the inter-spinous spacer
according to the present in invention as shown in FIG. 11, in place
in between the two spinous processes;
[0025] FIG. 13. is a side view of the inter-spinous spacer
according to the present in invention as shown in FIG. 11, in place
in between the two spinous processes;
[0026] FIG. 14. is a side view of the inter-spinous spacer
according to the present in invention as shown in FIG. 11, in place
in between the two spinous processes with fusion inducing material
packed inside;
[0027] FIG. 15 is a front view of the inter-spinous spacer
according the present invention as shown in FIG. 11;
[0028] FIG. 16 is a top view of an inter-spinous spacer according
the present invention as shown in FIG. 11;
[0029] FIG. 17 is a back side view of an inter-spinous spacer
according the present invention as shown in FIG. 11;
[0030] FIG. 18 is bottom view of an inter-spinous spacer according
the present invention as shown in FIG. 11;
[0031] FIG. 19 is a side view of an inter-spinous spacer according
the present invention as shown in FIG. 11;
[0032] FIG. 20 is perspective view of an inter-spinous spacer
according the present invention as shown in FIG. 11 including
visualization markers;
[0033] FIGS. 21-23 illustrate an exemplary insertion tool in use
with the inter-spinous spacer of FIG. 11, according to one
embodiment of the present invention;
[0034] FIGS. 24-27 illustrate an exemplary sizer tool for use when
implanting the inter-spinous spacer as shown in FIG. 11; according
one embodiment of the present invention;
[0035] FIGS. 28-29 illustrate an alternate attachment device for
use with the inter-spinous spacer shown in FIG. 11 according to an
alternate embodiment of the present invention;
[0036] FIG. 30 illustrates a posterior fluoroscopy view taken
during implantation of the inter-spinous spacer of FIG. 11
demonstrating the alignment of markers (including the formation of
a "T") to aid in placement; and
[0037] FIG. 31 illustrates a lateral fluoroscopy view taken during
implantation of the inter-spinous spacer of FIG. 11 demonstrating
the position of markers (including the formation of a backwards
"L") to aid in placement.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0038] Illustrative embodiments of the invention are described
below. In the interest of clarity, not all features of an actual
implementation are described in this specification. It will of
course be appreciated that in the development of any such actual
embodiment, numerous implementation-specific decisions must be made
to achieve the developers' specific goals, such as compliance with
system-related and business-related constraints, which will vary
from one implementation to another. Moreover, it will be
appreciated that such a development effort might be complex and
time-consuming, but would nevertheless be a routine undertaking for
those of ordinary skill in the art having the benefit of this
disclosure. The spinal alignment system disclosed herein boasts a
variety of inventive features and components that warrant patent
protection, both individually and in combination.
[0039] FIG. 1 illustrates a perspective view of a spinous process
spacer 10 of the present invention in use between two spinous
processes in a human spine. The spacer assembly 10 includes a
spacer 12, a primary spinous process tether 14, and two side
tethers 15 (only one of which is shown in FIG. 1). The spacer 12,
as illustrated in FIGS. 2-6, is generally cylindrical and includes
a main chamber 16, a pair of insertion tool apertures 18, a fusion
notch 20, and a pair of tether lumens 22. As will be described in
greater detail below, the spacer 12 is (according to a preferred
embodiment) coupled to only the superior spinous process such that
the spacer 12, with no coupling to the inferior spinous process.
This is accomplished, but way of example only, by securing the
primary spinous process tether 14 to the superior spinous process
(as a first step of affixation), followed by passing one side
tether 15 through each of the tether lumens 22, in between the
superior spinous process and the primary spinous process tether 14,
and finally tightening each side tether 15 until the spacer 12 is
generally transverse to the longitudinal axis of the spine.
[0040] The spacer 12 may be of bone or non-bone construction. The
bone embodiment involves manufacturing the spacer 12 from a
suitable allograft, including but not limited to clavicle, rib,
humerus, radius, ulna, metacarpal, phalanx, femur, tibia, fibula,
or metatarsal bone. The non-bone embodiment involves manufacturing
the spacer 12 from suitable non-bone materials, including but not
limited to polyaryletherketone (PEEK) and polyaryletherketoneketone
(PEKK). In either event, the spacer 12 is designed to fuse to the
superior spinous process over time, resulting in what is called
"hemi-fusion" in that the spacer 12 will be fused to only one
spinous process. This may be augmented by disposing any number of
suitable fusion-inducing materials within the spacer 12, including
but not limited to BMP1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14
. . . n, demineralized bone matrix, allograft cancellous bone,
autograft bone, hydroxy appetite, coral and/or other highly porous
substance.
[0041] Although shown and described with regard to the superior
spinous process, it will be appreciated that the spacer 12 may also
be coupled to only the inferior spinous process without departing
from the scope of the present invention. The spacer 12, once
positioned, serves to distract the inter spinous process space,
which advantageously restores foraminal height in stenotic patients
and may also indirectly decompress the intervertebral space.
[0042] As depicted in FIGS. 2-3, the main chamber 16 extends
through the lateral sides of the spacer 12. The main chamber 16 may
be provided in any of a variety of suitable shapes in addition to
the generally cylindrical shape shown, including but not limited to
a generally oblong, triangular, rectangular shape and/or
combinations thereof. The main chamber 16 may be dimensioned to
receive fusion inducing materials 32, as best illustrated in FIG.
8. Again, such fusion inducing materials may include, but are not
necessarily limited to BMP1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
13, 14 . . . n, demineralized bone matrix, allograft cancellous
bone, autograft bone, hydroxy appetite, coral and/or other highly
porous substance. The fusion inducing materials may be packed into
main chamber 16 before and/or after fixing spacer 10 to the spinous
process. The pair of insertion tool apertures 18 may be located on
either the posterior or anterior side of the spacer 12 and extend a
portion of the way through the spacer 12. The fusion notch 20
includes a slot or indent to receive a portion of an upper spinous
process or other vertebral feature to enhance fusion. The notch 20
may be located generally on the top surface towards the middle
portion of the spacer 12. The notch 20 helps center the spacer 12
relative to the superior spinous process.
[0043] According to another embodiment, shown in FIGS. 9-11, the
spacer 12 may be provided with a second notch 21 opposite the
fusion notch 20. The second notch 21 is capable of resting on the
inferior spinous process during use, which may assist in
maintaining the spacer 12 in a fully centered position relative to
the inferior spinous process. As best shown in FIG. 9, the fusion
notch 20 may be further provided with slots 23 extending into the
main chamber 16. When the spacer 12 is coupled to the superior
spinous process, these slots 23 will establish direct communication
between the fusion-inducing compounds provided within the main
chamber 16 and the lower aspect of the superior spinous process,
which advantageously augments the ability of the spacer 12 to fuse
to the superior spinous process (particularly if the spacer 12 is
constructed of non-bone materials).
[0044] As best shown in FIG. 6, the tether lumens 22 each extend at
an angle through the top surface of the spacer 12 and into the main
chamber 16. Each tether lumen 22 may be provided in any of a
variety of suitable shapes in addition to the cylindrical shape
shown, including but not limited to oblong, triangular, rectangular
and/or any combination thereof. The tethers 14, 15 may comprise any
number of suitable materials and configurations, including but not
limited to wire, cable, suture (permanent and/or bioresorbable),
allograft tissue and/or other single or multi-filament member.
Suture thread may include any number of components capable of
attaching to a spinous process, including but not limited to
ordinary suture threads known to and used by those skilled in the
art of wound closure. Suture thread may be of any length necessary
to effectively fuse the spacer 12 to the particular spinous
process.
[0045] The spacer 12 according to the present invention may be
constructed of allograft bone and formed in a generally cylindrical
shape. The spacer 12 of the present invention may be provided in
any number of suitable shapes and sizes depending upon a particular
patient and the shape and strength characteristics given the
variation from cadaver to cadaver. The spacer 12 may be dimensioned
for use in the cervical and/or lumbar spine without departing from
the scope of the present invention. The spacer 12 may be
dimensioned, by way of example only, having a length ranging
between 6-20 mm and a height ranging between 20-25 mm.
[0046] When constructed from allograft, the spacer 12 may be
manufactured according to the following exemplary method. A belt
sander may first be used to reduce any high spots or imperfections
to standardize the shape of the bone. Cut the allograft bone to
length using the band saw. Remove the cancellous material from the
inner canal to create the main chamber 16. Using calipers, measure
the struts and create a size distribution of spacers 12. Machine
the insertion tool apertures 18. Set-up a standard vice for holding
the implant across its width on the mill. Use a 3/32'' ball end
mill to create the insertion tool apertures 18 (same as cervical
allograft implant). Insert the spacer 12 into the vice and tighten.
Calculate the centerline of the 20 or 25 mm long spacer 12. Create
the holes 2.26 mm away from each side of the centerline (4.52 mm
hole to hole distance). Create a notch 22 for the spinous process.
Set-up the cervical allograft holding fixture that uses the
insertion tool apertures 18 and vice to hold the spacer 12 across
its width on the mill. Use a 1/4'' flat end mill to create the
notch 22. Calculate the centerline of the 20 or 25 mm long spacer
12. Insert the spacer 12 onto the fixture using the insertion tool
apertures 18 and tighten the vice. This automatically verifies the
correct sizing/spacing of the insertion tool apertures 18. Measure
the spacer 12 height. Calculate the cut depth to create the desired
spacer 12 size. Cut the flat on the spacer 12 to the desired depth.
Remeasure the spacer 12 to insure proper cut depth. Drill the
angled lumens 22 in face of spacer 12. Remove the spacer 12 from
the cervical allograft fixture and tighten into the standard vice.
Using a battery powered or corded drill with a 1/16'' drill bit,
drill through the front face to the canal on both sides. Belt sand
the face if needed to create a flat surface for the drill bit to
engage the spacer 12.
[0047] Turning now to FIG. 11 there is shown in perspective view an
example of a spacer 112 according to another embodiment of the
present invention. Spacer 112 includes a posterior side 113,
anterior side 114, lateral sides 115, a main chamber 116, and a
fusion notch 120. Spacer 112 is further provided with a plurality
of apertures including, but not necessarily limited to, three pairs
of insertion tool apertures 118a, 118b, and 118c, tether lumens
122, and fusion apertures 124.
[0048] FIGS. 12-14 depict spacer 112 in use in the inter spinous
process space of a patient. Spacer 112 is designed to fit between a
superior spinous process and an inferior spinous process and may be
dimensioned in any number of suitable shapes and sizes to
accomplish this. The spacer 112 may be positioned in any of the
cervical, thoracic, and/or lumbar spine and sizes may vary
accordingly. When in position, a properly sized spacer 112
distracts the inter spinous process space, restoring the foraminal
height in stenotic patients and indirectly decompresses the
intervertebral space. By way of example only, spacer 112 may be
dimensioned having a length ranging between 6-20 mm and a height
ranging between 20-25 mm.
[0049] Spacer 112 is preferably constructed of non-bone material.
Suitable non-bone materials may include, but are not necessarily
limited, to polyaryletherketone (PEEK) and
polyaryletherketoneketone (PEKK). Numerous advantages may be gained
by constructing spacer 112 out of materials such as PEEK and PEKK.
The stiffness properties of PEEK and PEKK closely match that of
bone. This reduces substantially the likelihood that the spinous
process will remodel around spacer 112 causing a re-narrowing of
the foraminal height and potentially resulting in revision
surgeries. PEEK and PEKK are also substantially radiolucent which
allows for improved post operative visualization of fusion between
the implant and the superior spinous process. Finally, by using the
non bone material with strategically placed apertures, fusion may
be confined to areas where it is useful. By way of example only,
spacer 112 may include fusion apertures only along the top (and
potentially posterior side 113) such that fusion occurs only
between the superior spinous process and spacer 112. In this
manner, extension is limited without disadvantageously limiting
flexion as well.
[0050] As depicted in FIG. 13, the main chamber 116 extends through
the lateral sides 115 of the spacer 112. Main chamber 116 may be
provided in any of a variety of suitable shapes in addition to the
generally cylindrical shape shown, including but not limited to a
generally oblong, triangular, rectangular shape and/or combinations
thereof. Main chamber 116 may be dimensioned to receive fusion
inducing materials 32, as best illustrated in FIG. 14. Again, such
fusion inducing materials may include, but are not necessarily
limited to BMP1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 . . .
n, demineralized bone matrix, allograft cancellous bone, autograft
bone, hydroxy appetite, coral and/or other highly porous substance.
The fusion inducing materials 32 may be packed into main chamber 16
before and/or after fixing spacer 10 to the spinous process. The
fusion inducing material 32 packed within main chamber 16 may
communicate openly with the superior spinous process through any of
the insertion tool apertures 118a, 118b, 118c, fusion apertures
124, and/or tether apertures 122. Through this communication,
fusion may occur from the superior spinous process into the main
chamber 116, permanently fixing spacer 112 in position.
[0051] With reference to FIGS. 15-19, the various features of
spacer 112 will now be described according to one preferred
embodiment. FIG. 16 is a view of the top of spacer 112. Fusion
notch 120 may be located generally on the top surface towards the
middle portion of the spacer 112. Fusion notch 120 generally
comprises a slot or indent dimensioned to receive an inferior
portion of a superior spinous process. The notch 120 helps center
the spacer 112 relative to the superior spinous process and may
assist in limiting side-to-side motion of spacer 112 prior to
fusion. Fusion notch 120 includes main fusion aperture 124a. Main
fusion aperture 124a extends into main chamber 116 and is the main
avenue for fusion between main chamber 116 and the superior spinous
process. Secondary fusion apertures 124b may be located along the
top of spacer 112 near the four corners of fusion notch 120 and
extend into main chamber 116. Secondary fusion apertures 124b may
provide additional routes for fusion to the superior spinous
process. Tether apertures 122 may be located along the top center
of spacer 112 near either side of fusion notch 120. Tether
apertures 122 are dimensioned to receive tethers 14, 15 to
temporarily fix spacer 112 in position until fusion to the superior
spinous process occurs, permanently fixing spacer 112 in place.
[0052] Main fusion aperture 124a, secondary fusion apertures 124b,
and tether apertures 122 may each be provided in any of a variety
of shapes in addition to the generally circular shapes shown,
including but not necessarily limited to, generally square,
rectangular, oblong, triangular, and/or any combination
thereof.
[0053] FIG. 16 illustrates the posterior side 113 of spacer 112.
The posterior side 113 may include 3 separate pairs of insertion
tool apertures 118a, 118b, and 118c. As will be described in more
detail below, having three pairs of insertion apertures allow
different insertion approaches to be utilized without needing to
make available separate tools and/or spacers with alternate
aperture configurations. Insertion tool apertures extend into main
chamber 116 and may serve as additional fusion routes after
insertion, this may further solidify and strengthen the fusion
between the superior spinous process and spacer 112.
[0054] FIG. 17 illustrates the anterior side 114 of spacer 112 and
FIG. 18 illustrates the bottom of the spacer. The anterior side 114
is preferably free of any apertures (except, secondary fusion
apertures 124b may be located near the top of spacer 112 on the
anterior side). When positioned in the inter spinous process space,
the anterior side 114 faces the spinal canal. Bone growth along the
anterior side could potentially interfere with the spinal canal and
the delicate neural tissue located inside, which could result in
pain and/or further surgery for the patient. The lack of
communication to main chamber 116 caused by the absence of
apertures on the anterior side 114 advantageously prevents bone
growth in the area. Likewise, the bottom of spacer 112 is also
aperture free and does not communicate with main chamber 116. This
advantageously prevents bone growth in the area and fusion to the
inferior spinous process will not occur. Again, this allows the
spinal segment to maintain flexion ability while still correcting
the stenosis. The bottom of spacer 112 may preferably have a
concave surface such that the distance from top to bottom of spacer
112 is greater neareast the lateral sides 115 and lesser near the
center. The concave bottom may rest along the inferior spinous
process and helps maintain spacer 112 in a centered position
relative to the inferior spinous process. FIG. 19 illustrates again
a lateral side 115 with main chamber 116 extending
therethrough.
[0055] To assist in visualization of spacer 112, both during and
after surgery, spacer 112 may include at least one marker.
Preferably, spacer 112 includes a top marker 126 and two side
marker 128. Markers 126, 128 may be comprised of biocompatible
radio-opaque material, such as for example only, titanium (or other
metals or polymers). Marker 126 may be positioned along the center
of spacer 112 within fusion notch 120. Preferably marker 126
extends through spacer 112 down to the bottom surface. Markers 128
may be located in the lateral sides below main chamber 116. During
and after placement of the spacer 112, markers 128 and 128 may be
utilized to correctly orient spacer 112.
[0056] Utilizing X-ray fluoroscopy and/or other suitable imaging
techniques from the posterior (or the back of the patient)
perspective of the spacer 112, the marker 126 situated in the
center and extending from fusion notch 120 to the bottom surface
should make a line between the superior spinous process and the
inferior spinous process viewable on the fluoroscopy screen when
the spacer 112 is properly positioned, as pictured in FIG. 30.
Markers 128 should be positioned on each side of the superior and
inferior spinous process in the inter spinous process space.
Drawing an imaginary line between markers 128 and connecting that
line to an imaginary line extending marker 126 to it should form an
upside down "T" if properly positioned. From a lateral view, the
depth of the spacer 112 in the interspinous space may be verified.
Marker 126 runs along the posterior side 113 of spacer 112. One or
both of markers 128 may be positioned in the lateral side 115 near
the posterior side 113. In one embodiment, one marker 128 is
positioned near the posterior side 113 and one marker 128 may be
positioned near the anterior side 114. On a lateral fluoroscopy
view taken during surgery the position of the markers 126 and 128
may be viewed in relation to the posterior end of the spinous
processes and the more anterior vertebral elements to ensure spacer
112 is neither too far anteriorly nor to far posoteriorly. Drawing
an imaginary line between markers 128 and connecting that line to
an imaginary line extending marker 126 to it should form an
backwards "L" if properly positioned, as pictured in FIG. 31.
[0057] The spinal apparatus 10 of the present invention may be
introduced into a spinal target site through the use of any of a
variety of suitable instruments having the capability to releasably
engage the spacer 12, 112. In a preferred embodiment, the insertion
tool permits quick, direct, accurate placement of the spacers 12,
112 between an upper and lower spinous process. An exemplary
insertion tool is shown and described in commonly owned U.S. Pat.
No. 6,923,814 entitled "System and Method for Cervical Fusion,"
which is expressly incorporated by reference as if set forth fully
herein. FIGS. 21-23 depict an exemplary insertion tool 200 for use
with spacers 12, 112. At a distal end 202, insertion tool 200
includes a pair of prongs 204 dimensioned to engage insertion
apertures 18 and 118a, 118b, 118c such that spacer 12, 112 becomes
temporarily attached to the distal end 202 for insertion. As
pictured in FIG. 24 insertion apertures 118a are aligned laterally
in the center of spacer 112 such that spacer 112 and insertion tool
200 mate at approximately the center point of the spacer. This
configuration may be advantageous if approaching the inter spinous
process space from a directly posterior approach. As pictured in
FIG. 23, insertion apertures 118b (and 118c) are aligned vertically
near the side of spacer 112. This configuration may be advantageous
if approaching from a more lateral direction.
[0058] In order to use the spinal apparatus 10 of the present
invention in a treatment of spinal stenosis, a clinician must first
designate the appropriate spacer size 12, 112. A clinician can
utilize the spinal apparatus 10 in either an open or minimally
invasive spinal fusion procedure. In either type of procedure, a
working channel would be created in a patient that reaches a
targeted spinal level. After the creation of the working channel,
the interspinous space would be prepared. After preparation a sizer
instrument is used to determine the appropriate size of the spacer
12, 112. One exemplary sizer instrument 300 is illustrated by way
of example only in FIGS. 24-27. Sizer instrument 300 includes a
handle portion 302 and an implant portion 304. Handle portion 302
may be configured in any variety of suitable shapes and sizes.
Implant portion 304 may be provided in a variety of sizes matching
the various sizes of spacer 112. As pictured, sizer implant may be
proved in an asymmetrical shape where the side opposite the handle
302 has a lesser height than the side to which handle 302 is
attached. This may allow the implant portion 304 to be rotated into
position with minimal interference from the spinous process.
Although it is not shown, it is conceived that spacer 112 may also
be provided in this asymmetrical fashion.
[0059] Preparation of the inter spinous process space includes
perforating the interspinous ligament between the superior and
inferior spinous processes. The supraspinous ligament may
preferably be left intact and distracted out of the way if
necessary. A key part of the preparation includes abrading the
inferior portion of the superior spinous process where it will
communicate with the fusion inducing materials 32 packed in the
main chamber 16, 116. Abrading removes the hard cortical bone from
the inferior surface of the superior spinous process and leaves
bleeding bone which is better adapted for fusion. As new bone
generates to heal the abraded portion it may grow into the main
chamber 16, 116, fixing spacer 12, 112 to the superior spinous
process.
[0060] In one embodiment described above the spacer 12, 112 is held
in position with tethers 14, 15 attached to the spinous process
through tether lumen 22, 122. According to an alternate embodiment,
pictured by way of example only in FIGS. 30-31 an alternate
securing mechanism may be used to fix spacer 12, 112 in place. The
alternate securing mechanism includes a zip cable 400 and a pair of
locking bases 402 404. Base 402 may be integral with cable 400.
Base 402 is positioned on the top of spacer 12, 112 next to the
fusion notch 20, 120 and fixed to the spacer 12, 112 via tether
apertures 22, 122. Base 402 is positioned over tether aperture 22,
122 and a locking pin 406 is inserted through the base into tether
aperture 22, 122. The step is repeated for base 404 on the opposite
side of the fusion notch 20, 120. Once both bases are in position
and the spacer 12, 112 is positioned between the spinous processes,
the zip cable 400 may be wrapped around the superior spinous
process and fed through the opposing base 404. Teeth 408 on the
cable 400 prevent cable 400 from loosening and thus holds the
spacer 12, 122 in place for fusion to occur. Any of a variety of
suitable materials may be used to form the zip cable 400, bases
402, 404, and locking pins 406. In one exemplary embodiment the
cable 400 and bases 402, 404 are comprised of nylon and the locking
pins 406 are comprised of titanium.
[0061] When the spacer 12, 112 is positioned and inserted into the
prepared space between the spinous processes it forces the spinous
processes apart. The spine flexes as the spinous processes are
forced apart and the neuroforamina and the spinal canal are
enlarged as the spine is flexed. The spinal apparatus 10 holds the
vertebrae in a flexed position, preventing extension but
advantageously allowing flexion.
[0062] While the invention is susceptible to various modifications
and alternative forms, specific embodiments thereof have been shown
by way of example in the drawings and are herein described in
detail. It should be understood, however, that the description
herein of specific embodiments is not intended to limit the
invention to the particular forms disclosed, but on the contrary,
the invention is to cover all modifications, equivalents, and
alternatives falling within the spirit and scope of the invention
as defined herein.
* * * * *