U.S. patent application number 16/258967 was filed with the patent office on 2019-05-23 for hybrid multifunctional posterior interspinous fusion device.
This patent application is currently assigned to The University of Toledo. The applicant listed for this patent is The University of Toledo. Invention is credited to Aakash Agarwal, Anand K. Agarwal, Vijay K. Goel.
Application Number | 20190150992 16/258967 |
Document ID | / |
Family ID | 48984818 |
Filed Date | 2019-05-23 |
![](/patent/app/20190150992/US20190150992A1-20190523-D00000.png)
![](/patent/app/20190150992/US20190150992A1-20190523-D00001.png)
![](/patent/app/20190150992/US20190150992A1-20190523-D00002.png)
![](/patent/app/20190150992/US20190150992A1-20190523-D00003.png)
![](/patent/app/20190150992/US20190150992A1-20190523-D00004.png)
![](/patent/app/20190150992/US20190150992A1-20190523-D00005.png)
![](/patent/app/20190150992/US20190150992A1-20190523-D00006.png)
![](/patent/app/20190150992/US20190150992A1-20190523-D00007.png)
![](/patent/app/20190150992/US20190150992A1-20190523-D00008.png)
![](/patent/app/20190150992/US20190150992A1-20190523-D00009.png)
![](/patent/app/20190150992/US20190150992A1-20190523-D00010.png)
View All Diagrams
United States Patent
Application |
20190150992 |
Kind Code |
A1 |
Agarwal; Anand K. ; et
al. |
May 23, 2019 |
HYBRID MULTIFUNCTIONAL POSTERIOR INTERSPINOUS FUSION DEVICE
Abstract
An interspinous stabilization device is provided that more
evenly distributes loads throughout the adjacent vertebrae than
known interspinous stabilization devices, and further can readily
compensate for graft settling so as to maintain continued axial
loading of the graft material.
Inventors: |
Agarwal; Anand K.; (Toledo,
OH) ; Goel; Vijay K.; (Toledo, OH) ; Agarwal;
Aakash; (Toledo, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The University of Toledo |
Toledo |
OH |
US |
|
|
Assignee: |
The University of Toledo
Toledo
OH
|
Family ID: |
48984818 |
Appl. No.: |
16/258967 |
Filed: |
January 28, 2019 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
14379139 |
Aug 15, 2014 |
10188434 |
|
|
PCT/US2013/026665 |
Feb 19, 2013 |
|
|
|
16258967 |
|
|
|
|
61599988 |
Feb 17, 2012 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 17/7068 20130101;
A61B 17/7062 20130101 |
International
Class: |
A61B 17/70 20060101
A61B017/70 |
Claims
1. An interspinous stabilization device comprising: a body portion;
a pair of mounting plates supported on the body portion and adapted
to engage a first vertebra; and a pair of connecting plates
supported on the body portion and adapted to engage a second
vertebra, wherein the interspinous stabilization device is adapted
to maintain continued axial loading of a graft disposed between the
first and second vertebra as settling of the graft occurs.
2. The interspinous stabilization device defined in claim 1,
wherein one or both of the mounting plates are shaped having a
torsional twist.
3. The interspinous stabilization device defined in claim 1,
wherein one or both of the mounting plates has an aperture formed
therethrough that is shaped to permit a fastener to extend
therethrough at multiple locations.
4. The interspinous stabilization device defined in claim 1,
wherein one or both of the connecting plates has a slot-shaped
aperture formed therethrough.
5. The interspinous stabilization device defined in claim 1,
wherein the body portion is defined by a bottom wall, first and
second opposed side walls, and a rear wall that cooperate to define
a partially enclosed space for the receipt of a bone graft
material.
6. The interspinous stabilization device defined in claim 1,
wherein one or both of the mounting plates is fixed in position
relative to the body portion.
7. The interspinous stabilization device defined in claim 1,
wherein one or both of the mounting plates is movable relative to
the body portion and lockable in a desired position relative
thereto.
8. The interspinous stabilization device defined in claim 1,
wherein the body portion is defined by a bottom wall, first and
second opposed side walls, and a rear wall, and wherein a hinge is
provided between the bottom wall and the rear wall to allow
relative pivoting movement therebetween.
9. The interspinous stabilization device defined in claim 8,
further including a movement-limiting mechanism to restrict the
pivoting movement of the rear wall relative to the bottom wall to a
single rotational direction.
10. The interspinous stabilization device defined in claim 1,
wherein one or both of the mounting plates has a generally uniform
thickness.
11. The interspinous stabilization device defined in claim 1,
wherein one or both of the mounting plates varies in thickness from
end to end.
12. The interspinous stabilization device defined in claim 1,
wherein one or both of the mounting plates is linear from end to
end.
13. The interspinous stabilization device defined in claim 1,
wherein one or both of the mounting plates is curved from end to
end.
14. The interspinous stabilization device defined in claim 1,
wherein one or both of the mounting plates has a slot-shaped
aperture formed therethrough.
15. The interspinous stabilization device defined in claim 5,
wherein one or both of the side walls are pivotably connected to
the rear wall.
16. The interspinous stabilization device defined in claim 5
wherein one or both of the mounting plates are pivotably connected
to the rear wall.
17. The interspinous stabilization device defined in claim 1,
wherein either or both of the pair of mounting plates is pivotably
supported on the body portion.
18. The interspinous stabilization device defined in claim 1,
wherein either or both of the pair of connecting plates is
pivotably supported on the body portion.
19. The interspinous stabilization device defined in claim 1,
wherein the body portion includes a spring-like hinge between the
pair of mounting plates and the pair of connecting plates.
20. The interspinous stabilization device defined in claim 19,
wherein the spring-like hinge is defined by a slot that extends
between the pair of mounting plates and the pair of connecting
plates.
21. The interspinous stabilization device defined in claim 19,
wherein the slot has a length of about 12 mm.
22. The interspinous stabilization device defined in claim 19,
wherein the slot expands at an angular relationship of about
2.degree..
23. The interspinous stabilization device defined in claim 1,
wherein the body portion includes a hinge between the pair of
mounting plates and the pair of connecting plates.
24. The interspinous stabilization device defined in claim 23,
wherein the hinge includes a pivot pin that extends through
portions of the pair of mounting plates and the pair of connecting
plates.
25. The interspinous stabilization device defined in claim 24,
further including a mechanism for maintaining the pair of mounting
plates in a predetermined position relative to the pair of
connecting plates.
26. The interspinous stabilization device defined in claim 25,
wherein the mechanism for maintaining includes a locking nut
provided on the pivot pin.
27. The interspinous stabilization device defined in claim 1,
wherein the interspinous fusion device is split into two separate
lateral portions that are supported on one another.
28. The interspinous stabilization device defined in claim 27,
wherein a first lateral portion has a protrusion provided thereon,
and wherein a second lateral portion has a recess provided therein
that receives the protrusion.
29. The interspinous stabilization device defined in claim 28,
wherein the recess and the protrusion are sized and shaped in a
complementary manner.
30. The interspinous stabilization device defined in claim 28,
wherein the recess and the protrusion are U-shaped.
31. An interspinous stabilization device that is connected to a
plate so as to directly stabilize a spinous process with a facet
joint in a vertebra in a spine.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. Ser.
No. 14/379,139 filed Aug. 15, 2014, now U.S. Pat. No. 10,188,434
issued Jan. 29, 2019, which is a national stage application filed
under 35 USC .sctn. 371 of international application
PCT/US2013/026665 filed Feb. 19, 2013, which claims the priority to
United States provisional application Ser. No. 61/599,988 filed
Feb. 17, 2012, the disclosure of which is incorporated herein by
reference.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
BACKGROUND OF THE INVENTION
[0003] This invention relates in general to an improved structure
for a hybrid multifunctional posterior interspinous fusion
device.
[0004] An interspinous stabilization device is a device that is
adapted to be secured to two or more adjacent vertebrae of a spine
in order to stabilize the relative positioning therebetween. An
interspinous stabilization device can also be used to facilitate
the placement of a bone-growth material, such as a bone graft
material, between such adjacent vertebrae to enhance bone growth
and promote fusion of the adjacent vertebrae.
[0005] Wolff s law of dynamic osteosynthesis states that every
change in the function of a bone is followed by definitive changes
in its internal architecture and secondary alterations in its
external confirmation. This means that osseous tissues remodel in
direct response to the stresses placed upon them. Although known
interspinous stabilization devices have functioned satisfactorily
for stabilizing the relative positioning of the adjacent vertebrae
to which they are connected, they are not well suited for desirably
maintaining axial compression on a bone graft material that is
disposed between such adjacent vertebrae after graft settling
occurs, such as described in Wolff s law. Thus, it would be
desirable to provide an improved structure for an interspinous
stabilization device that more evenly distributes loads throughout
the adjacent vertebrae than known structures, and further readily
compensates for graft settling so as to maintain continued axial
loading of the graft.
SUMMARY OF THE INVENTION
[0006] This invention relates to an improved structure for an
interspinous stabilization device that more evenly distributes
loads throughout the adjacent vertebrae than known interspinous
stabilization devices, and further readily compensates for graft
settling so as to maintain continued axial loading of the
graft.
[0007] More specifically, this invention relates to a medical
device that helps in performing a spinal fusion procedure by
holding the bone graft in place and stabilizing the facet screw by
a plate that is attached to it. The invention also performs a
dynamic function that compensates for settling of the bone graft
over time. This dynamic function may, if desired, be enhanced by a
movement-limiting mechanism that allows extension but not flexion
such that the bone graft fusion remains in contact and fusion takes
place. Thus, the interspinous stabilization device of this
invention is a multipurpose device that both more evenly
distributes loads throughout the adjacent vertebrae than known
interspinous stabilization devices, and further readily compensates
for graft settling so as to maintain continued axial loading of the
graft. A mounting plate of the interspinous fusion device may be
secured to a body portion therein in either a fixed or poly-axial
manner so as to provide better stability in lateral bending and
rotation.
[0008] Some of the indications for use of the interspinous fusion
device of this invention may include: (1) supplemental fixation for
anterior lumbar interbody fusion (ALIF) procedures; (2)
supplemental fixation for transforaminal lumbar interbody fusion
TLIP) procedures; (3) supplemental fixation lateral interbody
fusion procedures; (4) posterior interlaminar fusion; (5)
posterolateral fusion; (6) fusion in pars defect with facet
pedicular screw; (7) fusion in Grade I spondolystheis; and (8)
revision option in failed fusion/hybrid constructs.
[0009] Various aspects of this invention will become apparent to
those skilled in the art from the following detailed description of
the various embodiments of the invention, when read in light of the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a perspective view of a first embodiment of an
interspinous fusion device in accordance with this invention.
[0011] FIG. 2 is a front elevational view of the first embodiment
of the interspinous fusion device illustrated in FIG. 1.
[0012] FIG. 3 is a rear elevational view of the first embodiment of
the interspinous fusion device illustrated in FIGS. 1 and 2.
[0013] FIG. 4 is a side elevational view of the first embodiment of
the interspinous fusion device illustrated in FIGS. 1 through
3.
[0014] FIG. 5A is a side elevational view of a modified version of
the first embodiment of the interspinous fusion device illustrated
in FIG. 4.
[0015] FIG. 5B is a schematic view of a movement-limiting mechanism
that can be used with the modified version of the first embodiment
of the interspinous fusion device illustrated in FIG. 5A.
[0016] FIG. 6 is a perspective view of a portion of a second
embodiment of an interspinous fusion device in accordance with this
invention.
[0017] FIG. 7 is an enlarged view of a portion of the second
embodiment of the interspinous fusion device illustrated in FIG.
6.
[0018] FIG. 8 is a front elevational view of the second embodiment
of the interspinous fusion device illustrated in FIGS. 6 and 7.
[0019] FIG. 9 is a side elevational view of the second embodiment
of the interspinous fusion device illustrated in FIGS. 6 through
8.
[0020] FIG. 10 is an enlarged front elevational view of a
poly-axial mounting plate that can be used with the second
embodiment of the interspinous fusion device illustrated in FIGS. 6
through 9.
[0021] FIG. 11 is a perspective view of the poly-axial mounting
plate illustrated in FIG. 10.
[0022] FIG. 12 is a further enlarged front elevational view of a
modified portion of the poly-axial mounting plate illustrated in
FIGS. 10 and 11.
[0023] FIGS. 13 through 18 are perspective views of alternative
embodiments of the poly-axial mounting plate illustrated in FIGS. 9
through 12.
[0024] FIG. 19 is a perspective view of a third embodiment of an
interspinous fusion device in accordance with this invention.
[0025] FIG. 20 is a front elevational view of the third embodiment
of the interspinous fusion device illustrated in FIG. 19.
[0026] FIG. 21 is a side elevational view of the third embodiment
of the interspinous fusion device illustrated in FIGS. 19 and
20.
[0027] FIG. 22 is a perspective view of a fourth embodiment of an
interspinous fusion device in accordance with this invention.
[0028] FIG. 23 is a side elevational view of the fourth embodiment
of the interspinous fusion device illustrated in FIG. 22.
[0029] FIG. 24 is a top plan view of the fourth embodiment of the
interspinous fusion device illustrated in FIGS. 22 and 23.
[0030] FIGS. 25 and 26 are rear elevational views of modified
versions of the pivotable mounting plates illustrated in FIGS. 22
through 24.
[0031] FIG. 27 is a perspective view of a fifth embodiment of an
interspinous fusion device in accordance with this invention.
[0032] FIG. 28 is a side elevational view of the fifth embodiment
of the interspinous fusion device illustrated in FIG. 27.
[0033] FIG. 29 is a perspective view of a bone graft material that
can be used with the fifth embodiment of the interspinous fusion
device or any of the other embodiments of the interspinous fusion
device described herein.
[0034] FIG. 30 is a side elevational view of the bone graft
material illustrated in FIG. 29.
[0035] FIG. 31 is a perspective view of a modified version of the
fifth embodiment of the interspinous fusion device illustrated in
FIGS. 27 and 28.
[0036] FIG. 32 is a front end elevational view of the modified
version of the fifth embodiment of the interspinous fusion device
illustrated in FIG. 31.
[0037] FIG. 33 is a perspective view of a sixth embodiment of an
interspinous fusion device in accordance with this invention.
[0038] FIG. 34 is a side elevational view of the sixth embodiment
of the interspinous fusion device illustrated in FIG. 33.
[0039] FIG. 35 is a rear end elevational view of the sixth
embodiment of the interspinous fusion device illustrated in FIGS.
33 and 34.
[0040] FIG. 36 is an exploded perspective view of a seventh
embodiment of an interspinous fusion device in accordance with this
invention.
[0041] FIG. 37 is a perspective view of a first portion of the
seventh embodiment of an interspinous fusion device illustrated in
FIG. 36.
[0042] FIG. 38 is a perspective view of a second portion of the
seventh embodiment of an interspinous fusion device illustrated in
FIGS. 36 and 37.
DESCRIPTION OF THE EMBODIMENTS
[0043] Referring now to the drawings, there is illustrated in FIGS.
1 through 4 a first embodiment of an interspinous fusion device,
indicated generally at 10, in accordance with this invention. The
interspinous fusion device 10 includes a central body portion that
is defined by a bottom wall 11, first and second opposed side walls
12 and 13, and a rear wall 14. The bottom wall 11, the side walls
12 and 13, and the rear wall 14 cooperate to define a partially
enclosed space, the purpose of which will be explained below. The
side walls 12 and 13 have respective inwardly facing serrated
surfaces 12a and 13a provided thereon. Also, the side walls 12 and
13 have respective apertures 12b and 13b formed therethrough. The
purposes for these structures will also be explained below.
[0044] As best shown in FIG. 4, a slot 14 a is formed between
portions of the side walls 12 and 13 and the rear wall 14 so as to
define a spring-like hinge between the bottom wall 11 and the rear
wall 14 of the interspinous fusion device 10. This spring-like
hinge allows a limited amount of pivoting movement of the rear wall
14 relative to the bottom wall 11. The purpose for allowing this
pivoting movement will be explained below.
[0045] First and second mounting plates 16 and 17 are respectively
secured to the rear wall 14 of the interspinous fusion device 10,
extending upwardly therefrom above the side walls 12 and 13,
respectively. The mounting plates 16 and 17 have respective
inwardly facing serrated surfaces 16a and 17a provided thereon, the
purpose of which will be explained below. First and second mounting
plates 18 and 19 are respectively secured to the upper ends of the
first and second mounting plates 16 and 17. In the illustrated
embodiment, the mounting plates 18 and 19 extend laterally
outwardly in opposite directions from the upper ends of the
mounting plates 16 and 17, although such is not required. Each of
the illustrated mounting plates 18 and 19 is shaped having a
torsional twist as it extends laterally outwardly from the
associated brackets 16 and 17. However, the mounting plates 18 and
19 may have any desired shape or combination of shapes.
Additionally, the mounting plates 18 and 19 need not be fixed in
position relative to the associated brackets 16 and 17, but rather
may be movable relative thereto in a poly-axial manner, as
described below. In either event, the mounting plates 18 and 19
have respective apertures 18a and 19a formed therethrough for a
purpose that will be explained below.
[0046] First and second connecting plates 20 and 21 are
respectively secured to the lower ends of the first and second side
walls 12 and 13 of the central body portion of the interspinous
fusion device 10. In the illustrated embodiment, the connecting
plates 20 and 21 are each generally planar and extend parallel to
one another. However, the connecting plates 20 and 21 may have any
desired shape or combination of shapes. The connecting plates 20
and 21 have respective slot-shaped apertures 20a and 21a formed
therethrough. The purposes for the connecting plates 20 and 21 and
the slot-shaped apertures 20a and 21a will be explained below.
[0047] The interspinous fusion device 10 is adapted to be secured
to pair of adjacent vertebrae (not shown) in a spine to stabilize
the relative positioning therebetween and to facilitate the
placement of a bone-growth material, such as a bone graft material,
to enhance bone growth and fusion of the adjacent vertebrae. To
accomplish this, the first and second mounting plates 18 and 19 are
adapted to be secured to an upper one of the pair of adjacent
vertebrae. To accomplish this, the interspinous fusion device 10 is
initially positioned such that the first and second mounting plates
18 and 19 are disposed adjacent to respective facets or other
portions of the upper vertebra. Then, one or more fasteners (not
shown), such as conventional bone screws, can be inserted through
each of the apertures 18a and 19a into engagement with the adjacent
facets or other portions of the upper vertebra. In this manner, the
first and second mounting plates 18 and 19 of the interspinous
fusion device 10 can be secured to the upper one of the pair of
adjacent vertebrae.
[0048] As shown in the drawings, either or both of the apertures
18a and 19a formed through the first and second mounting plates 18
and 19 can be shaped to permit the fasteners to extend therethrough
at multiple locations. In the illustrated embodiment, both of the
apertures 18a and 19a are irregularly shaped so as to define plural
discrete positions on the mounting plates 18 and 19 through which
the fasteners may extend into engagement with the adjacent facets
or other portions of the upper vertebra. These plural discrete
positions provide desirable flexibility during the installation
process, inasmuch as the geometries of each of the upper pair of
adjacent vertebrae can vary in accordance with the specific anatomy
of the patient. The interspinous fusion device 10 of this invention
can readily accommodate such variations in anatomy because the
fasteners can be provided at any selected one of the plural
discrete positions defined by the apertures 18a and 19a that is
deemed to be most appropriate based upon such anatomy.
[0049] Additionally, as discussed above, the illustrated mounting
plates 18 and 19 extend laterally outwardly in opposite directions
from the upper ends of the side walls 12 and 13, and each is shaped
having a torsional twist. The shapes of the first and second
mounting plates 18 and 19 are such that relatively large surface
areas thereof engage the respective facets or other portions of the
upper vertebra. Such relatively large surface area engagement
functions to distribute load forces imparted by the interspinous
fusion device 10 more evenly across the surface areas of the
respective facets or other portions of the upper vertebra. As a
result, the generation of undesirable localized stresses on the
facets or other portions of the upper vertebra is substantially
reduced or avoided.
[0050] The first and second connecting plates 20 and 21 of the
interspinous fusion device are adapted to be secured to a lower one
of the pair of adjacent vertebrae. To accomplish this, the
interspinous fusion device 10 is initially positioned such that the
first and second connecting plates 20 and 21 are disposed about a
spinous process or other portion of the lower vertebra. Then, one
or more fasteners (not shown), such as conventional bone screws,
can be inserted through each of the slot-shaped apertures 20a and
21a of the connecting plates 20 and 21 and through the spinous
process or other portion of the lower vertebra. In this manner, the
first and second connecting plates 20 and 21 of the interspinous
fusion device 10 can be secured to the lower one of the pair of
adjacent vertebrae.
[0051] As mentioned above, the bottom wall 11, the side walls 12
and 13, and the rear wall 14 cooperate to define a partially
enclosed space within the interspinous fusion device 10. This
partially enclosed space can be used to receive a quantity of a
bone-growth material, such as a bone graft material, to enhance
bone growth and fusion of the adjacent vertebrae. The partially
enclosed space within the interspinous fusion device further
functions to prevent the bone-growth material from undesirably
flowing out of the region between the adjacent vertebrae. The
inwardly facing serrated surfaces 12a and 13a and the apertures 12b
and 13b on the side walls 12 and 13 provide irregularly shaped
surfaces that are well adapted to be engaged by the bone-growth
material, thereby functioning to positively retain such material
within the central body portion of the interspinous fusion device
10. The mounting inwardly facing serrated surfaces 16a and 17a of
the mounting plates 16 and 17 function in the same manner.
[0052] As also mentioned above, the interspinous stabilization
device 10 of this invention not only more evenly distributes loads
throughout the adjacent vertebrae than known interspinous
stabilization devices, but also can readily compensate for graft
settling so as to maintain continued axial loading of the graft
material disposed between the adjacent vertebrae. In the
interspinous stabilization device 10 of this invention, this is
accomplished by the provision of the two slot-shaped apertures 20a
and 21a formed through the connecting plates 20 and 21. During the
above-described installation process, the first and second
connecting plates 20 and 21 are disposed about a spinous process or
other portion of the lower vertebra, and a fastener is inserted
through the slot-shaped apertures 20a and 21a and through the
spinous process of the lower vertebra. As settling of the bone
graft material occurs, the fastener can slide through the
slot-shaped apertures 20a and 21a, thereby allowing the distance
between the two adjacent vertebrae to decrease as settling of the
bone graft occurs. Consequently, the axial pressure exerted by such
adjacent vertebrae on the bone graft material is effectively
maintained as settling of the bone graft material occurs.
[0053] Additionally, as also described above, the slot 14 a formed
between portions of the side walls 12 and 13 and the rear wall 14
defines a spring-like hinge between the bottom wall 11 and the rear
wall 14 of the interspinous fusion device 10. This spring-like
hinge allows a limited amount of pivoting movement of the rear wall
14 relative to the bottom wall 11. As a result, the axial pressure
exerted by such adjacent vertebrae on the bone graft material is
effectively maintained as settling of the bone graft material
occurs.
[0054] Thus, the dynamic system of this invention is designed to
take full advantage of Wolff s law of dynamic osteosynthesis. By
avoiding stress shielding and allowing full load sharing, earlier
and more substantial graft incorporation can occur. The unique
slot-shaped apertures 20a and 21a and slot 14a are designed to
compensate for graft setting (bone graft or special scaffold
material, such as calcium phosphate, etc.) so as to maintain
continued axial loading on the graft. Axial settling, which allows
full load sharing capability, occurs because the fasteners are free
to move through the slot-shaped apertures 20a and 21 formed through
the first and second connecting plates 20 and 21 and because the
spring-like hinge defined between the bottom wall 11 and the rear
wall 14 of the interspinous fusion device 10 allows a limited
amount of pivoting movement of the mounting plates 16 and 17 (which
are connected to the upper vertebra) relative to the connecting
plates 20 and 21 (which are connected to the lower vertebra). As a
result, the amount of this settling distance is determined by the
amount of graft resorption, not because of any physical restriction
imposed by the interspinous stabilization device 10 of this
invention. Also, compression of the bone graft material as
explained above is facilitated.
[0055] Referring now to FIGS. 5A and 5B, there is illustrated a
modified version 10' of the first embodiment of the interspinous
fusion device illustrated in FIGS. 1 through 4, wherein like
reference numbers are used to identify similar structures. In this
modified version 10', a movement-limiting mechanism, indicated
generally at 15, is provided with (or in lieu of) the spring-like
hinge to limit the pivoting movement of the mounting plates 16 and
17 relative to the connecting plates 20 and 21 to a single
rotational direction. An exemplary structure of the
movement-limiting mechanism 15 is illustrated in FIG. 5B. As shown
therein, the movement-limiting mechanism 15 can include an outer
ring 15a that is secured to one of the bottom wall 11 and the rear
wall 14, an inner hub 15b that is secured to the other of the
bottom wall 11 and the rear wall 14, and one or more spring-loaded
balls 15c disposed between the outer ring 15a and the inner hub
15b. The spring-loaded balls 15c cooperate with the outer ring 15a
and the inner hub 15b in a manner that is well known in the art to
allow relative movement to occur only in one rotation direction. As
a result, the movement-limiting mechanism 15 may be used to
restrict the pivoting movement of the rear wall 14 relative to the
bottom wall 11 to allow extension of the joint between the adjacent
vertebrae but not flexion. It will be appreciated that the
movement-limiting mechanism 15 may also be used in connection with
any of the embodiments described herein.
[0056] Referring now to FIGS. 6 through 11, there is illustrated a
second embodiment of an interspinous fusion device, indicated
generally at 110, in accordance with this invention. The second
embodiment of the interspinous fusion device 110 is similar to the
first embodiment of the interspinous fusion device 10 described
above, and like reference numbers (incremented by 100) are used to
indicate similar structures. In this second embodiment of the
interspinous fusion device 110, however, the mounting plates 118
and 119 (see FIGS. 10 and 11) are not fixed in position relative to
the upper ends of the first and second mounting plates 116 and 117.
Rather, the mounting plates 118 and 119 are respectively secured to
the upper ends of the first and second mounting plates 116 and 117
in a manner that allows for poly-axial or other relative
movement.
[0057] In the illustrated embodiment, this is accomplished by
providing each of mounting plates 116 and 117 with a mounting
structure 116b and 117b, and further by providing each of the
mounting plates 118 and 119 with a cooperating mounting structure
118a and 119a. As shown in FIGS. 6 through 9, the illustrated
mounting structures 116b and 117b are generally hollow and
cylindrical in shape and extend laterally outwardly in opposite
directions from the associated mounting plates 116 and 117. Each of
the hollow cylindrical mounting structures 116b and 117b has an
outer surface, an inner surface, and a transverse aperture that
extends from the outer surface to the inner surface. As shown in
FIGS. 10 and 11, the illustrated mounting structures 118a and 119a
of the mounting plates 118 and 119 are generally spherical in
shape. The spherical mounting structures 118a and 119a of the
mounting plates 118 and 119 are sized and shaped to fit snugly
within the hollow cylindrical mounting structures 116b and 117b of
the mounting plates 116 and 117. As a result, the positions of the
mounting plates 118 and 119 relative to the associated mounting
plates 116 and 117 can be adjusted in a poly-axial manner to
correspond with the anatomy of the vertebra to which they are
secured, as described above. When a desired relative positioning
has been achieved, the mounting plates 118 and 119 can be locked in
those relative positions by set screws (not shown) that extend
respectively through each of the transverse apertures formed
through the hollow cylindrical mounting structures 116b and 117b of
the mounting plates 116 and 117 into engagement with the spherical
mounting structures 118a and 119a of the mounting plates 118 and
119. However, the mounting plates 118 and 119 can be locked in
those relative positions by any desired means.
[0058] As shown in FIG. 6, the inner surfaces of the hollow
cylindrical mounting structures 116b and 117b of the mounting
plates 116 and 117 are smooth. However, if desired, such inner
surfaces of the hollow cylindrical mounting structures 116b and
117b may be formed having a serrated or other irregular shape, such
as shown at 116b' in FIG. 7. Such irregular shape can provide an
enhanced locking capability over smooth inner surface. Similarly,
as shown in FIGS. 10 and 11, the outer surfaces of the spherical
mounting structures 118a and 119a of the mounting plates 118 and
119 are smooth. However, if desired, such outer surfaces of the
spherical mounting structures may be formed having a serrated or
other irregular shape, such as shown at 118a' and 119a' in FIG. 12.
Such irregular shape can similarly provide an enhanced locking
capability over smooth outer surface. Either or both of the inner
surfaces of the hollow cylindrical mounting structures 116b and
117b and the outer surfaces of the spherical mounting structures
118a and 119a may be formed in this manner.
[0059] FIGS. 13 through 18 are perspective views of alternative
embodiments of one of the poly-axial mounting plates 118
illustrated in FIGS. 9 through 12.
[0060] In FIGS. 13 and 14, a first modified mounting plate 119-1 is
curved from end to end, has a generally uniform thickness
throughout, and has a generally uniform width throughout.
[0061] In FIG. 15, a second modified mounting plate 119-2 is linear
from end to end, has a thickness that varies from a relatively
thick portion adjacent to the mounting structure to a relatively
thin portion adjacent an outer end thereof, and has a width that
varies from a relatively narrow portion adjacent to the mounting
structure to a relatively wide portion adjacent the outer end
thereof. In FIG. 16, a third modified mounting plate 119-3 has a
torsional twist from end to end, has a generally uniform thickness
throughout, and has a width that varies from a relatively narrow
portion adjacent to the mounting structure to a relatively wide
portion adjacent an outer end thereof. In FIG. 17, a fourth
modified mounting plate 119-4 is linear from end to end, has a
thickness that varies from a relatively thin portion adjacent to
the mounting structure to a relatively thick portion adjacent an
outer end thereof, and has a width that is generally uniform
throughout. Lastly, in FIG. 18, a fifth modified mounting plate
119-5 is shaped having a torsional twist from end to end, has a
generally uniform thickness throughout, and has a generally uniform
width throughout.
[0062] Referring now to FIGS. 19 through 21, there is illustrated a
third embodiment of an interspinous fusion device, indicated
generally at 210, in accordance with this invention. The third
embodiment of the interspinous fusion device 210 is similar to the
first embodiment of the interspinous fusion device 10 described
above, and like reference numbers (incremented by 200) are used to
indicate similar structures. In this third embodiment of the
interspinous fusion device 210, however, the mounting plates 216
and 217 have respective slot-shaped apertures 216a and 217a formed
therethrough, and the mounting plates 18 and 19 are eliminated. In
this embodiment, rather, the mounting plates 216 and 217 are
secured directly to respective portions of the upper vertebra in a
manner that is similar to how the connecting plates 20 and 21 are
secured directly to respective portions of the lower vertebra, as
described above. The slot-shaped apertures 216a and 217a function
in a manner that is similar to the slot-shaped apertures 20a and
21a to maintain the axial pressure exerted by the adjacent
vertebrae on the bone graft as settling of the bone graft material
occurs.
[0063] Referring now to FIGS. 22 through 24, there is illustrated a
fourth embodiment of an interspinous fusion device, indicated
generally at 310, in accordance with this invention. The fourth
embodiment of the interspinous fusion device 310 is similar to the
first embodiment of the interspinous fusion device 10 described
above, and like reference numbers (incremented by 300) are used to
indicate similar structures. In this fourth embodiment of the
interspinous fusion device 310, however, the side walls 312 and 313
are connected to the back wall 314 by respective first hinges 315a.
Thus, the side walls 312 and 313 can be pivoted inwardly and
outwardly relative to one another and relative to the back wall 314
as desired. Similarly, the mounting plates 316 and 317 are
connected to the back wall 314 by respective second hinges 315b.
Thus, the mounting plates 316 and 317 can be pivoted inwardly and
outwardly relative to one another and relative to the back wall 314
as desired. Consequently, the interspinous fusion device 310 can
readily accommodate variations in the anatomy of the vertebrae to
which the interspinous fusion device 310 is attached, as described
above.
[0064] FIGS. 25 and 26 are rear elevational views of alternative
embodiments of the pivotable mounting plates 318' and 319'
illustrated in FIGS. 22 through 24. In addition to the apertures
318a' and 319a' formed respectively therethrough, each of the
mounting plates 318' and 319' has one or more protrusions 318b' and
319b' formed thereon. The protrusions 318b' and 319b' are adapted
to engage respective portions of the associated vertebra to provide
a more positive locking engagement therewith and to more evenly
distributes loads throughout.
[0065] Referring now to FIGS. 27 and 28, there is illustrated a
fifth embodiment of an interspinous fusion device, indicated
generally at 410, in accordance with this invention. The fifth
embodiment of the interspinous fusion device 410 includes a central
body portion that is defined by first and second opposed lower side
walls 411 and 412, a rear wall 413, and first and second opposed
upper side walls 414 and 415. The first and second opposed lower
side walls 411 and 412 have respective upper surfaces 411a and 412a
provided thereon, while the first and second opposed upper side
walls 414 and 415 have respective lower surfaces 414a and 415a
provided thereon. If desired, some or all of the surfaces 411a,
412a, 414a, and 415a may be defined by embossments or other raised
structures provided as shown in FIGS. 27 and 28, although such is
not required. The first and second opposed lower side walls 411 and
412, the rear wall 413, and the first and second opposed upper side
walls 414 and 415 cooperate to define a partially enclosed space,
the purpose of which will be explained below.
[0066] As best shown in FIG. 28, the rear wall 413 defines a
spring-like hinge between the lower side walls 411 and 412 and the
upper side walls 414 and 415. A slit 415c (see FIG. 28) or other
gap or space is defined between the upper surfaces 411a and 412a of
the lower side walls 411 and 412 and the lower surfaces 414a and
415a of the upper side walls 414 and 415. The slit 415c may have
any desired shape or size. However, it has been found desirable
that the slit 415c have a front-to-rear length L (see FIG. 28) of
about 12 mm. As also best shown in FIG. 28, it is desirable that
the top-to-bottom height of the slit 415c increases from the rear
to the front thereof. The angular relationship between the upper
surfaces 411a and 412a of the lower side walls 411 and 412 and the
lower surfaces 414a and 415a of the upper side walls 414 and 415
can vary as desired. However, an angular relationship of about
2.degree. has been found to be desirable.
[0067] First and second mounting plates 416 and 417 are
respectively secured to the upper side walls 414 and 415. The
mounting plates 416 and 417 have respective apertures 416a and 417a
or other structures provided thereon to facilitate the securement
of the interspinous fusion device 410 to an upper one of the pair
of adjacent vertebrae, as described above. In the illustrated
embodiment, the mounting plates 416 and 417 are each generally
planar and extend parallel to one another. However, the mounting
plates 416 and 417 may have any desired shape or combination of
shapes. Similarly, first and second connecting plates 420 and 421
are respectively secured to the lower side walls 414 and 415. The
connecting plates 420 and 421 have respective apertures 420a and
421a or other structures provided thereon to facilitate the
securement of the interspinous fusion device 410 to a lower one of
the pair of adjacent vertebrae, as also described above. In the
illustrated embodiment, the connecting plates 420 and 421 are each
generally planar and extend parallel to one another. However, the
connecting plates 420 and 421 may have any desired shape or
combination of shapes.
[0068] FIGS. 29 and 30 illustrate a quantity of a bone graft
material, indicated generally at 450, that can be used with the
fifth embodiment of the interspinous fusion device 410 or any of
the other embodiments of the interspinous fusion device described
herein. The illustrated bone graft material 450 is generally
rectilinear in shape (although such is not required) and includes
an upper surface 451, a lower surface 452, a front end 453, and a
rear end 454. The bone graft material 450 is adapted to be disposed
within the interspinous fusion device 410 with the upper surface
451 adjacent to the lower surfaces 414a and 415a of the upper side
walls 414 and 415, the lower surface 452 adjacent to the upper
surfaces 411a and 412a of the lower side walls 411 and 412, and the
rear end 454 adjacent to the rear wall 413. The angular
relationship between the upper and lower surfaces 451 and 452 of
the bone graft material 450 can vary as desired. However, as best
shown in FIG. 30, the top-to-bottom distance between the upper and
lower surfaces 451 and 452 of the bone graft material 450
preferably gets larger from the front end 453 to the rear end 454.
The top-to-bottom distance between the upper and lower surfaces 451
and 452 of the bone graft material 450 can, for example, vary in
the range of from about 1.degree. to about 5.degree., preferably
about 2.degree..
[0069] The relationship between the size and shape of the gap 415c
in the interspinous fusion device 410 and the size and shape of the
bone graft material 450 is advantageous. In particular, it is
desirable that this relationship be such that a relatively high
compression be placed upon the bone graft material 450 while
imposing a relatively low stress on the interspinous fusion device
410. The relatively high compression placed upon the bone graft
material 450 facilitates that the bone graft material 450 remain in
a desired position relative to the interspinous fusion device 410
and, thus, to the vertebrae to which the interspinous fusion device
410 is to be secured. The relatively low stress imposed upon the
interspinous fusion device 410 minimizes the likelihood that damage
may occur during or after installation of the bone graft material
450. The interspinous fusion device 410 may be formed from any
desired material including, but not limited to, polyether ether
ketone (PEEK), titanium, nitinol (nickel titanium), cortical bone,
and composites.
[0070] FIGS. 31 and 32 illustrate a variation 410' on the fifth
embodiment of the interspinous fusion device 410 illustrated in
FIGS. 27 and 28, and like reference numbers are used to indicate
similar structures. In this variation, the interspinous fusion
device 410' includes first and second mounting plates 418' and 419'
that are respectively secured to the upper ends of the first and
second mounting plates 416' and 417'. Like the various mounting
plates discussed above, the first and second mounting plates 418'
and 419' may have any desired shape or combination of shapes, may
be fixed in position relative to the respective mounting plates
416' and 417' (as illustrated) or movable relative thereto (such as
shown in FIGS. 6 through 18), and may include one or more apertures
(not shown) to facilitate the securement of the interspinous fusion
device 410' to respective ones of the upper pair of adjacent
vertebrae, all as described above.
[0071] Referring now to FIGS. 33 through 35, there is illustrated a
sixth embodiment of an interspinous fusion device, indicated
generally at 510, in accordance with this invention. The sixth
embodiment of the interspinous fusion device 510 is similar to the
fourth embodiment of the interspinous fusion device 410 described
above, and like reference numbers (incremented by 100) are used to
indicate similar structures. In this sixth embodiment of the
interspinous fusion device 510, however, the rear wall of the
interspinous fusion device 510 is defined by a hinge, indicated
generally at 513, that includes a first portion 513a that is formed
integrally with or connected to the lower side walls 511 and 512
and a second portion 513b that is formed integrally with or
connected to the lower side walls 511 and 512. A pivot pin 513c
extends through aligned apertures (not shown) formed through the
first and second portions 513a and 513b such that the lower side
walls 511 and 512 can pivot relative to the upper side walls 514
and 515 in a jaw-like manner. A locking nut 513d may be threaded
onto the end of (or otherwise secured to) the pivot pin 513c. The
locking nut 513d can be selectively operated (typically tightened
on the pivot pin 513c) so as to retain the lower side walls 511 and
512 in a desired position relative to the upper side walls 514 and
515.
[0072] In use, the sixth embodiment of the interspinous fusion
device 510 is installed by initially releasing the locking nut 513d
so that the lower side walls 511 and 512 are free to pivot relative
to the upper side walls 514 and 515. Then the interspinous fusion
device 510 is installed by securing the mounting plates 416 and 417
to an upper one of the pair of adjacent vertebrae, and further by
securing the connecting plates 420 and 421 to a lower one of the
pair of adjacent vertebrae, as also described above. Thereafter,
the locking nut 513d is tightened on the pivot pin 513c so as to
maintain the lower side walls 511 and 512 in a predetermined
position relative to the upper side walls 514 and 515. This
structure allows the spacing between the first and second opposed
lower side walls 511 and 512 and the first and second opposed upper
side walls 514 and 515 to be customized to the specific anatomy of
the patient.
[0073] Referring now to FIGS. 36 through 38, there is illustrated a
seventh embodiment of an interspinous fusion device, indicated
generally at 610, in accordance with this invention. The seventh
embodiment of the interspinous fusion device 610 is similar to the
fourth embodiment of the interspinous fusion device 410 described
above, and like reference numbers (incremented by 200) are used to
indicate similar structures. In this seventh embodiment, however,
the interspinous fusion device 610 is split into two separate
lateral portions 610a and 610b that are supported on one another.
To accomplish this, the first portion 610a has a protrusion 613b
provided thereon that extends laterally toward the second portion
6106 of the interspinous fusion device 610. Similarly, the second
portion 610a has a recess 613a provided thereon that faces
laterally toward the first portion 610a of the interspinous fusion
device 610. Preferably, the recess 613a and the protrusion 6136 are
sized and shaped in a complementary manner, such as the illustrated
U-shaped configurations. However, the recess 613a and the
protrusion 613b may be formed having any desired sizes and shapes,
as well as combinations thereof.
[0074] The interspinous fusion device 610 is assembled by initially
aligning the protrusion 613b provided on the first portion 610a
with the recess 613a provided on the second portion 610b as shown
in FIG. 36. Then, the first and second portions 610a and 610b are
moved toward one another such that the protrusion 613b is received
within the recess 613a. Preferably, the recess 613a and the
protrusion 613b are sized and shaped so that relative lateral
movement is permitted without significant other looseness
therebetween. This structure allows the lateral spacing between the
mounting plates 616 and 617 and/or between the connecting plates
620 and 621 to be customized to the specific anatomy of the
patient. If desired, a locking mechanism (not shown) can be
provided to maintain the first and second portions 610a and 610b in
a desired lateral orientation relative to one another.
[0075] The principle and mode of operation of this invention have
been explained and illustrated in its various embodiments. However,
it must be understood that this invention may be practiced
otherwise than as specifically explained and illustrated without
departing from its spirit or scope.
* * * * *