U.S. patent application number 14/022398 was filed with the patent office on 2016-07-21 for device for stabilizing a vertebral joint and method for anterior insertion thereof.
The applicant listed for this patent is GLOBUS MEDICAL, INC.. Invention is credited to Vipin Kunjachan, David C. Paul, Jon Suh, Sean Suh.
Application Number | 20160206438 14/022398 |
Document ID | / |
Family ID | 52630058 |
Filed Date | 2016-07-21 |
United States Patent
Application |
20160206438 |
Kind Code |
A9 |
Suh; Sean ; et al. |
July 21, 2016 |
Device for Stabilizing a Vertebral Joint and Method for Anterior
Insertion Thereof
Abstract
A prosthetic device can be used as a prosthesis following a
discectomy or a corpectomy. The prosthetic device includes two
endplates with staggered motion limiting members. The device can be
configured to allow six degrees of motion when comparing one
endplate relative to the other. The endplates can be configured to
fix the joint by changing the body held within the device and by
adding a locking plate and fasteners. A method teaches how to
insert a device to an intervertebral space via an anterior
incision.
Inventors: |
Suh; Sean; (Plymouth
Meeting, PA) ; Paul; David C.; (Phoenixville, PA)
; Suh; Jon; (Blue Bell, PA) ; Kunjachan;
Vipin; (Jeffersonville, PA) |
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Applicant: |
Name |
City |
State |
Country |
Type |
GLOBUS MEDICAL, INC. |
AUDUBON |
PA |
US |
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Prior
Publication: |
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Document Identifier |
Publication Date |
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US 20150073554 A1 |
March 12, 2015 |
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|
Family ID: |
52630058 |
Appl. No.: |
14/022398 |
Filed: |
September 10, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12699648 |
Feb 3, 2010 |
8556974 |
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14022398 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 2002/30599
20130101; A61F 2002/30607 20130101; A61F 2002/30563 20130101; A61F
2/44 20130101; A61F 2002/30578 20130101; A61F 2002/30014 20130101;
A61F 2002/30616 20130101; A61F 2/442 20130101; A61F 2002/30405
20130101; A61F 2002/304 20130101; A61F 2002/30411 20130101; A61F
2002/443 20130101; A61F 2002/30393 20130101; A61F 2/4425 20130101;
A61F 2002/30601 20130101; A61F 2002/30517 20130101 |
International
Class: |
A61F 2/44 20060101
A61F002/44 |
Claims
1. A device for stabilizing a first vertebra relative to a second
vertebra, the device comprising: a superior endplate having an
inferior surface and a motion limiting member, said motion limiting
member extending downward below said inferior surface; an inferior
endplate having a superior surface and a motion limiting member,
said motion limiting member extending upward above said superior
surface; a compressible and flexible body having a superior surface
and an inferior surface, said superior surface of said body facing
said inferior surface of said superior endplate, said inferior
surface of said body facing said superior surface of said inferior
endplate, said body being held in contact with and laterally
between said superior endplate and said inferior endplate by said
motion limiting members; and a locking plate having a superior
screw anchoring member configured to connect to a first vertebra
and an inferior screw anchoring member configured to connect to a
second vertebra, said locking plate overlying said superior
endplate and said inferior endplate.
2. The device according to claim 1, wherein said motion limiting
member on said superior endplate and said motion limiting member on
said inferior endplate are staggered with regard to each other.
3. The device according to claim 1, wherein: said body has a
height; and said motion limiting member on said superior endplate
is shorter than said height of said body.
4. The device according to claim 1, wherein: said body has a side;
and said motion limiting member on said superior endplate and said
motion limiting member on said inferior endplate both support said
body along said side.
5. The device according to claim 1, wherein: said body has a first
side and a second side opposing said second side; said motion
limiting member disposed on said superior endplate supports said
body along said first side of said body; and said motion limiting
member disposed on said inferior endplate supports said body along
said second side of said body.
6. The device according to claim 5, further comprising a further
motion limiting member disposed on said superior endplate, said
further motion limiting member supporting said body along said
second side of said body.
7. The device according to claim 1, wherein at least one of said
endplates is shaped substantially like a quadrilateral.
8. The device according to claim 1, wherein at least one of said
endplates complements a contact surface of a body of a vertebra to
be supported by said at least one of said endplates.
9. The device according to claim 1, wherein at least one of said
endplates has bone growth bore formed therein.
10. The device according to claim 1, further comprising a superior
screw anchoring member extending superiorly from said superior
endplate, said superior screw anchoring member being configured to
be fastened to a superior vertebra.
11. The device according to claim 10, further comprising an
inferior screw anchoring member extending inferiorly from said
inferior endplate, said inferior screw anchoring member being
configured to be fastened to an inferior vertebra.
12. The device according to claim 1, further comprising an inferior
screw anchoring member extending inferiorly from said inferior
endplate, said inferior screw anchoring member being configured to
be fastened to an inferior vertebra.
13. The device according to claim 10, further comprising a fastener
connected to said superior screw anchoring member, said fastener
being configured to secure said superior screw anchoring member to
the superior vertebra.
14. The device according to claim 12, further comprising a fastener
connected to said inferior screw anchoring member, said fastener
being configured to secure said inferior screw anchoring member to
the inferior vertebra.
15. A device for stabilizing a first vertebra relative to a second
vertebra, the device comprising: a superior endplate having an
inferior surface and a motion limiting member, said motion limiting
member extending downward below said inferior surface; an inferior
endplate having a superior surface and a motion limiting member,
said motion limiting member extending upward above said superior
surface; a compressible and flexible body having a superior surface
and an inferior surface, said superior surface of said body facing
said inferior surface of said superior endplate, said inferior
surface of said body facing said superior surface of said inferior
endplate, said body being held in contact with and laterally
between said superior endplate and said inferior endplate by said
motion limiting members; and a locking plate having a superior
screw anchoring member configured to connect to a first vertebra
and an inferior screw anchoring member configured to connect to a
second vertebra.
16. The device according to claim 15, wherein said motion limiting
member on said superior endplate and said motion limiting member on
said inferior endplate are staggered with regard to each other.
17. The device according to claim 15, wherein: said body has a
height; and said motion limiting member on said superior endplate
is shorter than said height of said body.
18. The device according to claim 15, wherein: said body has a
side; and said motion limiting member on said superior endplate and
said motion limiting member on said inferior endplate both support
said body along said side.
19. The device according to claim 15, wherein: said body has a
first side and a second side opposing said second side; said motion
limiting member disposed on said superior endplate supports said
body along said first side of said body; and said motion limiting
member disposed on said inferior endplate supports said body along
said second side of said body
20. A device for stabilizing a first vertebra relative to a second
vertebra following a discectomy or a corpectomy, the device
comprising: a superior endplate having an anterior edge, a
posterior edge, a right edge, a left edge, an inferior surface, a
textured superior surface, and motion limiting members extending
inferiorly from said inferior surface, said superior endplate
having a bone growth bore formed therein; a inferior endplate
having an anterior edge, a posterior edge, a right edge, a left
edge, a superior surface, a textured inferior surface, and motion
limiting members, one of said motion limiting members extending
superiorly said inferior endplate having a bone growth bore formed
therein; a compressible and flexible body having a superior
surface, an inferior surface, and a height defined between said
superior surface and said inferior surface, said superior surface
of said body facing said inferior surface of said superior
endplate, said inferior surface of said body facing said superior
surface of said inferior endplate, said body being held in contact
and laterally between said superior endplate and said inferior
endplate by said motion limiting members; a superior screw
anchoring member extending superiorly from said anterior edge of
said superior endplate, said superior screw anchoring member being
configured to connect to a superior vertebra; an inferior screw
anchoring member extending inferiorly from said anterior face of
said inferior endplate, said inferior screw anchoring member being
staggered from said superior screw anchor and configured to connect
to an inferior vertebra; and wherein the device further comprises a
locking plate having a superior screw anchoring member configured
to connect to a first vertebra and an inferior screw anchoring
member configured to connect to a second vertebra, said locking
plate overlying said superior endplate and said inferior endplate.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation application of
U.S. patent application Ser. No. 12/699,638 filed on Feb. 3, 2010,
which is incorporated in its entirety herein.
FIELD OF THE INVENTION
[0002] The present disclosure generally relates to spinal
prostheses and surgical methods for inserting spinal
prostheses.
BACKGROUND OF THE INVENTION
[0003] The spine includes a series of joints routinely called
motion segment units. Motion segment units are the smallest
component of the spine that exhibit kinematic behavior
characteristic of the entire spine. The motion segment unit is
capable of flexion, extension, lateral bending, and translation.
The components of each motion segment unit include two adjacent
vertebrae and their apophyseal joints, the intervertebral disc, and
the connecting ligamentous tissue. Each component of the motion
segment unit contributes to the mechanical stability of the
joint.
[0004] Components of a motion segment that move out of position or
become damaged can lead to serious pain and may lead to further
injury to other components of the spine. Depending upon the
severity of the structural changes that occur, treatment may
include fusion, discectomy, or laminectomy.
[0005] Underlying causes of structural changes in the motion
segment unit leading to instability include trauma, degeneration,
aging, disease, surgery, and the like. Thus, rigid stabilization of
one or more motion segment units may be an important element of a
surgical procedure in certain cases (i.e., injuries, deformities,
tumors, etc.), whereas it is a complementary element in others
(i.e., fusion performed due to degeneration). The purpose of rigid
stabilization is the immobilization of a motion segment unit.
[0006] As mentioned above, current surgical techniques typically
involve fusing one or more unstable motion segment units and
possibly, the removal of ligaments, bone, disc, or combinations
thereof included in the unstable motion segment unit or units prior
to fusing. There are several disadvantages to fusion, however. For
example, the fusing process results in a permanent or rigid
internal fixation of all or part of the intervertebral joints and
usually involves metallic rods, plates, and the like for
stabilization. In all cases, the systems are intended to immobilize
rigidly the motion segment unit to promote fusion within that
motion segment unit.
[0007] In addition to a loss of mobility, fusion also causes the
mobility of the motion segment to be transferred to other motion
segments of the spine. The added stresses transferred to motion
segments neighboring or nearby the fused segment can cause or
accelerate degeneration of those segments. One other disadvantage
to fusion is that it is an irreversible procedure. In addition, it
is believed that fusion of a motion segment has a clinical success
of approximately seventy percent (.about.70%), and often does not
alleviate pain experienced by the patient.
[0008] Analysis of fusion systems going back to the early 1960's
has shown that the intentionally rigid designs have often caused
stress concentrations and have directly and indirectly contributed
to the degeneration of the joints above and below the fusion site
(as well as at the fusion site itself). In addition, rigid, linear
bar-like elements eliminate the function of the motion segment
unit. Finally, removal of portions of the motion segment unit
reduces the amount of support available for the affected motion
segment unit.
[0009] Analysis has also shown that fusion procedures can be
improved by modifying the load haring characteristics of the
treated spine. Thus, it would be desirable to allow more of a
physiologic loading between pedicular fixation and anterior column
support. It would also be desirable to have a device that precludes
or at least delays the need for fusion for all but the most
advanced degeneration of a motion segment, particularly if such a
device would allow close to normal motion and pain relief.
SUMMARY
[0010] The present application is generally directed to devices and
methods for installing a soft spine stabilization system that
replicates the physiologic response of a healthy spinal motion
segment.
[0011] According to one aspect of the invention, a device for
stabilizing a first vertebra relative to a second vertebra
following discectomies or corpectomies is provided. The device is a
prosthesis that is able to articulate in up to six degrees of
freedom when installed. In the X-axis, the device allows
flexion/extension and lateral slip. In the Y-axis, the device
allows a joint to have left/right axial rotation and
anterior/posterior slip. In the Z-axis, the device allows
left/right lateral bending. The device includes a superior endplate
with at least one motion limiting member and inferior endplate with
at least one motion limiting member. A body is held between the
endplates. The motion limiting member on the superior endplate
extends inferiorly (i.e. downward) below the inferior surface of
the endplate. The motion limiting member of the inferior endplate
extends superiorly (i.e. above) the superior surface of the
inferior endplate. The body is disposed between the endplates and
is held, at least in part, within the device by the motion limiting
members. The motion limiting member of the superior endplate
contacts the motion limiting member of the inferior endplate to
limit motion of the endplates relative to each other.
[0012] The endplates may generally have a transverse section shaped
like the abutting (i.e. superior or inferior) surface of the body
of the vertebra being supported. Generally, this shape is a
trapezoid shape. The longer base on the trapezoid is on the
anterior side of the vertebra. The shape of the endplate is said to
be "generally" trapezoid shaped because the shape can be
curvilinear to compliment the anatomy being supported.
[0013] The motion limiting members may have a generally rectangular
cuboid shape. The edges of the motion limiting members can be
rounded.
[0014] According to a further aspect of the invention, the motion
limiting members on the superior endplate are staggered with
respect to the motion limiting members on the inferior endplate.
"Staggered" generally means that the motion limiting members
alternate between a motion limiting member disposed on the superior
endplate and a motion limiting member disposed on the inferior
endplate. In addition, "staggered" connotes that there can be at
least some separation between a motion liming member and a
neighboring motion liming member.
[0015] By being staggered, the motion limiting members on the
superior endplate can enmesh with the motion limiting members on
the inferior endplate. In addition, by being staggered and enmeshed
the motion limiting members can move in a limited amount relative
to each other until they contact each other. The staggered
positioning allows the six degrees of freedom discussed previously
while simultaneously can limit the amount of freedom in those
degrees of freedom.
[0016] According to a further aspect of the invention, the body has
a height, and the motion limiting members on the endplates are
generally shorter than the body. By being shorter than the body,
the body may still compress by the difference in heights before a
motion limiting member on an opposing endplate contacts the
opposing endplate. In general, such a feature minimizes wear from
rubbing between the endplate and the opposing motion limiting
member. It also limits movements and prevents the body from being
compressed to an extreme thinness.
[0017] According to a further aspect of the invention, a motion
limiting member on the superior endplate is disposed on the same
side of the body as a motion limiting member on the inferior
endplate. By having a motion limiting member on the superior
endplate and the inferior endplate, the body is secured on the
given side by the motion limiting members and cannot slip from the
superior endplate and the inferior endplate. Additional pairs (i.e.
a superior and an inferior) of motion limiting members can be
disposed about a periphery of the endplates to secure the body
between the endplates.
[0018] According to a further aspect of the invention, motion
limiting members can be disposed on a given endplate on opposite
sides of the body. For example, an endplate can have an anterior
motion limiting device and a posterior motion limiting device. In
this way, the body can be secured between the two motion limiting
devices. The motion limiting members that are disposed on opposite
sides of the body also can be placed with one on each of the
endplates. Combinations of motion limiting members can be added to
secure the body between the endplates and to provide the proper
restrictions on the range of motion of the joint.
[0019] According to a further aspect of the invention, the endplate
can have at least one bore to promote bone growth therethrough. The
bore can be a single large bore. Alternative, a plurality of
smaller bores can be formed in each endplate. Bone will generally
grow into the bore and help to secure the prosthesis to the
adjacent vertebra.
[0020] According to a further aspect of the invention, screw
anchoring members can be added to the superior surface and the
inferior surface to fasten the device to the vertebrae. While each
endplate can be secured to a respective vertebra, it is possible
for only one screw anchoring member to be used. The screw anchoring
member is a tab with a socket formed therein. The socket can be
threaded or unthreaded. The screw anchoring member can be disposed
on the anterior edge of a respective endplate. By being on the
anterior edge, the device can be slid into position from an
anterior position to place the screw anchoring members in contact
with the vertebra. The screw anchoring members can be configured to
be vertically aligned with movement limiting members on the
anterior edge. A fastener is used to attach the screw anchoring
member to the vertebra. A bone screw is one preferred form of
fastener. Other fasteners such as sutures, staples, and nails can
be used.
[0021] The device can include a locking plate for fixing one
vertebra relative to another vertebra. The locking plate can be
installed on an anterior of the vertebrae in a spinal joint. The
locking plate has a first screw anchoring member and a second screw
anchoring member. Each screw anchoring member receives a respective
fastener that connects to a respective vertebra. The first screw
anchoring member is configured to connect to a first vertebra. The
second screw anchoring member is configured to connect to a second
vertebra. The locking plate can be screwed into a vertebra or
vertebrae that is/are immediately adjacent to the rest of the
device. The locking member can overly the superior endplate and the
inferior endplate. When the locking plate is installed, the two
vertebrae are fixed in position relative to each other. Typically,
the fastener is a bone screw.
[0022] The locking member can be configured so that the anchoring
member extends beyond an endplate at a position that is vertically
aligned with a motion limiting member on the opposing endplate. For
example, the superior screw anchoring member of the locking plate
can be configured to connect to a vertebra, above a motion limiting
member on the inferior endplate. Likewise, the inferior screw
anchoring member of the locking plate can be configured to connect
to a vertebra below the motion limiting member of the superior
endplate.
[0023] The screw anchor members of the locking plate can be
configured to connect to a vertebra alongside the screw anchor
member of respective endplates. The screw anchor members can press
against each other and even contact each other. By pressing against
each other, the locking plate forms a particularly stiff,
reinforced fixed joint. In the case of abutting screw anchor
members, a contact surface is defined where the two abut.
[0024] The device including the body, the superior endplate, and
the inferior endplate can have a combined height substantially
equal to an intervertebral disc that is to be replaced. By having a
height substantially equal to a disc, the device can be used as a
prosthesis in a discectomy. The device is said to be
"substantially" equal to the height of the disc because the
original disc might be compressed or damaged. Accordingly, the
height of the device should be the size that is desired.
[0025] The device including the body, the superior endplate, and
the inferior endplate can have a combined height substantially
equal to a vertebra and attached superior and inferior
intervertebral discs that are to be replaced. By having a height
substantially equal to a vertebra and adjacent discs, the device
can be used as a prosthesis in a corpectomy. The device is said to
be "substantially" equal to the height of the vertebra because the
original vertebra and/or discs might be compressed or damaged.
Accordingly, the height of the device should be the height that is
desired.
[0026] The body held between the endplates can be flexible and
resilient. By being flexible, the body can move and compress to
allow movement of one endplate relative to the other endplate. When
the body is resilient, the body tends to return to its original
state after being moved or compressed.
[0027] The body can have a fixed height. The body can be rigid. A
body with a fixed height is useful when the joint is to be
fixed.
[0028] The body can be made of different materials to affect its
qualities, in particular its flexibility. The body can be made of a
single homogenous material. The body can have layers of different
materials to control the physical properties of the body. The
materials in the different layers can have different
properties.
[0029] The body can be a self-standing single body cage. U.S. Pat.
No. 7,137,997 is incorporated by reference as an example of a
self-standing single body cage.
[0030] The body of the device can be a self-standing expandable
cage. U.S. Pat. Nos. 7,384,431, 5,702,453, and 5,236,460 are
incorporated by reference as examples of self-standing expandable
cages.
[0031] A fastener can be inserted through the body and into a
vertebra to stabilize being connected to said body and configured
to insert into a vertebra. The fastener can fix and stabilize the
body relative to the vertebra.
[0032] The device according to the invention can have a motion
limiting member on each side (anterior, posterior, left, and right)
of each endplate. The body is placed between the motion limiting
members. The motion limiting member prevents the body from moving
laterally from between the endplates. The body limits how far one
end plate can shift relative to the other when there are
surrounding motion limiting members.
[0033] The motion limiting members disposed on the superior
endplate can be staggered with regard to the motion limiting
members disposed on the inferior endplate. "Staggered" is generally
meant to mean that the motion limiting members are offset from each
other with reference to vertical alignment. In other words, a
motion limiting member on the top does not align vertically with a
motion limiting member on the top. In addition, a gap can be left
between adjacent superior and inferior motion limiting members. The
gap in the staggered motion limiting members allows for a desired
amount of play to allow for freedom of movement of one endplate
relative to another. The amount of play can be controlled by
adjusting the width of the gaps. By being staggered, the motion
limiting members on the superior endplate can enmesh with the
motion limiting members on the inferior endplate.
[0034] The device, in particular the endplates, can be made from a
biocompatible material. Examples of biocompatible material include
biocompatible metals and biocompatible polymers.
[0035] The outer surface (i.e. superior surface on the superior
endplate or the inferior surface on the inferior endplate) of each
end plate can be configured to support an adjacent vertebra. The
outer surface of each endplate can be textured with devices to
increase friction between the endplate and the adjacent vertebrae.
The devices to increase friction can be pyramid or tetrahedron
shaped spikes.
[0036] The invention may also include a method of stabilizing a
superior vertebra with respect to an inferior vertebra following a
discectomy or corpectomy. The method includes forming an incision
to anterior of an intervertebral space. The intervertebral space at
least originally has an intervertebral disc; the intervertebral
disc may have been replaced by a prosthesis in a previous
procedure. A superior vertebra is disposed superior to the
intervertebral disc. An inferior vertebra is disposed inferior to
the intervertebral disc. The superior vertebra and the inferior
vertebra each have an anterior face.
[0037] In the next step, a device as described previously is
inserted anteriorly via the anterior incision into the
intervertebral space. The device is inserted from the anterior
until the superior screw anchoring member contacts the anterior
face of the superior screw anchor member. The inferior anchoring
member also should be contacting the anterior face of the inferior
screw anchor member. The next step includes fastening the first
screw anchoring member to the anterior face of said superior
vertebra. Usually, the fastening step is accomplished by a
inserting a bone screw through the screw anchoring member into the
vertebra. Likewise, the method includes fastening the second screw
anchoring member to the anterior face of the inferior vertebra. The
fastening can be accomplished by screwing a bone screw through the
anchoring member into the vertebra.
[0038] The invention encompasses a method of stabilizing a superior
vertebra with respect to an inferior vertebra following a
discectomy or corpectomy. The method can begin with forming an
incision to anterior of an intervertebral space having a superior
vertebra with an anterior face. In the next step, a device as
described previously is inserted via the anterior incision to the
intervertebral space. The next step includes fastening a first
screw member to the anterior face of a superior or an inferior
vertebra. The next step can include fastening the second screw
member to the anterior face of the other vertebra.
[0039] The method of securing the vertebrae to each other can
include adding a locking plate, which has been described
previously. The locking body is placed over the device. The locking
body can be placed to overly the superior endplate and the inferior
endplate. The locking plate can be configured to abut the screw
anchor members. The locking body is then fastened to the superior
vertebra and the inferior vertebra.
[0040] Other features that are considered as characteristic for the
invention are set forth in the appended claims.
[0041] Although the invention is illustrated and described herein
as embodied in a device for stabilizing a vertebral joint and a
method for anterior insertion of the device, it is nevertheless not
intended to be limited to the details shown, since various
modifications and structural changes may be made therein without
departing from the spirit of the invention and within the scope and
range of equivalents of the claims.
[0042] The construction and method of operation of the invention,
however, together with additional objects and advantages thereof
will be best understood from the following description of specific
embodiments when read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] FIG. 1 is a diagrammatic top side view of a device according
to the invention.
[0044] FIG. 2 is a front side view of the device shown in FIG.
1.
[0045] FIG. 3 is a left side view of the device shown in FIG.
1.
[0046] FIG. 4 is a right side view of the device shown in FIG.
1.
[0047] FIG. 5 is a rear side view of the device shown in FIG.
1.
[0048] FIG. 6 is a bottom side view of the device shown in FIG.
1.
[0049] FIG. 7 is a front side view of a locking plate according to
the invention.
[0050] FIG. 8 is a perspective view of the locking plate shown in
FIG. 7.
[0051] FIG. 9 is a front side view of the device shown in FIG. 2
with the locking plate shown in FIG. 7 installed.
[0052] FIG. 10 is a perspective view of a screw according to the
invention.
[0053] FIG. 11 is a side view of a first embodiment of a body that
is homogeneous.
[0054] FIG. 12 is a side view of a second embodiment of a body
having three layers.
[0055] FIG. 13 is a perspective view of a self-standing expanding
cage.
[0056] FIG. 14 is a perspective view of a self-standing single body
cage.
[0057] FIG. 15 is a left side view of a device being inserted
anteriorly in a corpectomy.
[0058] FIG. 16 is a top side view of the device shown in FIG. 15
installed after a corpectomy.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
[0059] Referring now to the figures of the drawing in detail and
first, particularly, to FIGS. 1-6 thereof, there is seen a device
20 for stabilizing a first bone of a joint relative to a second
bone of a joint. In particular, the device 20 is useful for
stabilizing a first vertebra relative to a second vertebra
following discectomies or corpectomies. The device 20 includes a
superior endplate 1 and inferior endplate 11. As shown in FIG. 15,
the superior endplate 1 is configured to support a superior
vertebra 101. The inferior endplate 11 is configured to support an
inferior vertebra 111. In one embodiment, a superior surface 8 of
the superior endplate 1 is textured to increase friction between
the superior vertebra 101 and the superior endplate 1. Likewise,
the inferior surface 18 of the inferior endplate 11 is textured.
The textured surface can include teeth, ridges, and/or grooves.
These protrusions extend from a bone engaging surface of the device
and engage bone of the joint to reduce or prevent movement of the
surface relative to the bone. The superior surface 8 and inferior
surface 18 either directly contact the superior vertebra 101 or
inferior vertebra 111, respectively, or intervening layers and
bodies, which are not shown, can be inserted therebetween.
[0060] In the embodiment shown in FIG. 1, the superior endplate 1
has a bone growth bore 4 formed therein. Multiple bores 4 are
formed in the embodiment of the inferior endplate shown in FIG. 6.
Bone tissue from an adjacent bone can grow into bone growth bore 4.
Growing bone into the bone growth bore 4 forms a strong connection
between the bone and the device 20.
[0061] As shown in FIGS. 1 and 6, the endplates 1 and 11 have a
cross section that is similar to the cross section of the vertebrae
being supported. Generally, this shape is substantially
trapezoidal. With respect to the shape, "substantially" means that
the shape is interpreted as generally trapezoidal but the sides may
be curvilinear. The larger base of the trapezoid shape is to be the
anterior edge (i.e. front edge).
[0062] Motion limiting members 5 extend downward (i.e. inferiorly)
from the superior endplate 1. The motion limiting members 5 are
spaced apart from each other. In the preferred embodiment, the
motion limiting members are rectangular cuboids. The edges can be
rounded.
[0063] Motion limiting members 15 extend upward (i.e. superiorly)
from the inferior endplate 11. The motion limiting members 15 are
spaced apart from each other. In the preferred embodiments, the
motion limiting elements 15 are rectangular cuboids. The edges can
be rounded.
[0064] When the endplate 1 and the endplate 11 are brought
together, the motion limiting members 5 and 15 seat between each
other. Space can remain between the motion limiting members 5 and
15 to allow the endplates 1 and 11 to move relative to each other.
The relative movement is subject to the compressive and elastic
qualities of a body 10; the body 10 is described in detail below.
However, when the endplates 1 and 11 move too far laterally from
each other, a given motion limiting members 5 and 15 contact a
neighboring motion limiting member 5 or 15 to limit how far the
endplates 1 and 11 can shift relative to each other. The amount of
lateral movement allowed can match a typical range of motion before
the implantation or can match an amount that the device 20 is safe
to allow. In the preferred embodiment, the motion limiting members
5 and 15 alternate between a motion limiting member 5 on the
superior endplate 1 and a motion limiting member 15 on the inferior
endplate 11.
[0065] The motion limiting members 5 and 15 are distributed about
the perimeter of the respective endplate 5 and 15. In an exemplary
embodiment, a motion limiting member 5 is located at each corner of
the superior endplate 1. A motion limiting member 15 is located in
the middle of each edge of the inferior endplate 11.
[0066] A body 10 is placed between the superior endplate 1 and the
inferior endplate 11. The body 10 is placed in the center in the
middle of the motion limiting members 5 and 15, which are disposed
about the perimeter of the endplates 1 and 11. Embodiments of the
body 10 are discussed later in the specification. The body 10 has a
height that is sized so that the overall height of the device (i.e.
the height of the endplates 1 and 11 plus the height of the body
10) is substantially equal to the space in which the device is
being inserted. For example, if the device were to replace an
intervertebral disc, the height of the device would be equal to the
height of the intervertebral disc. If the device were replacing a
vertebra, the height of the device when installed would be equal to
the height of the vertebra. The combined height is said to be
"substantially" equal because often the anatomy being replaced has
degenerated and is compressed so the height of the replacement may
be slightly larger to provide a replacement of what the height
should be.
[0067] In one embodiment, the motion limiting members 5 and 15 have
a height from the face of the endplate that is less than the height
of the body 10. In this way, the body 10 can compress axially and
the motion limiting members 5 and 15 will not contact the opposing
endplate.
[0068] In the preferred embodiment, the motion limiting members 5
and 15 have a height at least as high as the expected amount of
axial expansion. In this way, the motion limiting members 5 and 15
will remain in contact with the body 10 even when the spine is at
its greatest length. Accordingly, the motion limiting members 5 and
15 never become disengaged from the body 10.
[0069] The space between a given limiting member 5 or 15 with
neighboring motion limiting members 15 or 5, respectively, should
be great enough to allow the intended range of motion. The space
between should not be so great to exceed a safe amount of
twisting.
[0070] A screw anchor member 4 extends superiorly (i.e. upward)
from the superior endplate 1. The screw anchor member 4 is a
rectangular tab, although other shapes are possible. The screw
anchor member 2 extends upward from an anterior edge 7 of the
endplate 1. The screw anchor member 2 is disposed above the motion
limiting member 5 on the anterior edge 7. A socket 3 is formed in
the screw anchor member 2. The socket 3 is preferably threaded and
counter sunk. In an alternate embodiment, the socket 3 is not
threaded and not counter sunk. A bone screw 30 is screwed though
the socket 3 into the underlying body of the vertebra.
[0071] The bone screw 30 includes a head 31. The head 31 cannot
pass through the socket 3. The head and socket 3 may be polyaxially
matable to facilitate secure attachment of the screw to bone, for
example, cortical bone. The head 31 has a socket 32 formed therein.
The bone screw includes a thread 33.
[0072] A screw anchor member 14 extends inferiorly (i.e. downward)
from the inferior endplate 11. The screw anchor member 14 is a
rectangular tab. The screw anchor member 12 extends downward from
an anterior edge 17 of the endplate 11. The screw anchor member 12
is disposed below the motion limiting member 15 on the anterior
edge 17. A socket 13 is formed in the screw anchor member 12. The
socket 13 is preferably threaded and counter sunk. In an alternate
embodiment, the socket 13 is not threaded and not counter sunk. A
bone screw 30 or compatible fastener is screwed though the socket 3
into the underlying body of the vertebra.
[0073] In the preferred embodiment, the device 20 allows six
degrees of motion in the joint. In the X-axis, the device 20 allows
flexion/extension and lateral slip. In the Y-axis, the device 20
allows left/right axial rotation and anterior/posterior slip. In
the Z-axis, the device 20 allows left/right lateral bending and
axial tension/compression.
[0074] FIGS. 7-9 show a preferred embodiment of locking plate 40.
The locking plate 40 has a horizontal plate 42. A superior screw
anchoring member extends superiorly (i.e. upwardly) from said
horizontal plate 42. The superior screw anchoring member 41 is a
rectangular tab. The superior screw anchoring member 41 has a
socket 43 formed therein. The socket 43 is threaded and
countersunk. An inferior screw anchoring member 45 extends
inferiorly (i.e. downwardly) from said horizontal plate 42. The
inferior screw anchoring member 45 may also have a socket 43 formed
therein. The socket 43 is threaded and countersunk. In other
embodiments, the socket is unthreaded or not countersunk. The
locking plate 40 is configured to be tall enough so that the
superior screw anchoring member 41 overlies a superior vertebra
while the inferior screw anchoring member 45 overlies an inferior
vertebra. Screws 30 are screwed into each screw anchoring member 41
and 45 and underlying bone to fasten the locking member 40 to the
vertebrae. When installed, the vertebrae are no longer able to move
relative to each other.
[0075] The locking plate 40 is placed over the anterior face of the
device 20. The horizontal plate 42 overlies the superior endplate 1
and the inferior endplate 11. The superior screw anchoring member
41 of the locking plate 40 is adjacent the superior screw anchoring
member 12 of the superior endplate 1. The inferior anchoring member
45 of the locking plate 40 is adjacent the superior screw anchoring
member 22 of the inferior endplate 11. The superior anchoring
member 41 of the locking plate 40 is inline vertically with the
inferior anchoring member 12 of the inferior endplate 11. The
inferior anchoring member 41 of the locking plate 40 is inline
vertically with the superior anchoring member 2 of the superior
endplate 1.
[0076] The screw anchoring members 41 and 45 of the locking plate
40 abut the screw anchoring members 2 and 12 of the endplates 1 and
11. Each of the screw anchoring members 41 and 45 has a medial
contact surface 46 and 47, respectively. The screw anchoring member
2 has a medial contact surface 9. The screw anchoring member 12 has
a medial contact surface 19. When the locking plate 40 is
installed, the contact surface 46 abuts the contact surface 9 and
the contact surface 47 abuts the contact surface 19. While it is
preferred that the contact surfaces directly contact each other,
intervening objects can be placed between them.
[0077] The device 20 and locking plate 40 are made of a
biocompatible material. Preferably, the device 20 and locking plate
40 are made of a biocompatible metal or polymer.
[0078] In one embodiment shown in FIGS. 2-4, the device 20 allows
for movement. In this embodiment, the body 10 is flexible and
resilient. A suitable material allows for temporary motion of the
endplate 1 relative to the endplate 11 and then helps to return the
endplates 1 and 11 to their original position. The body 10 is
sandwiched between the superior endplate 1 and the inferior
endplate 11. The body 10 is surrounded by and retained by the
motion limiting members 5 and 15. The body 10 is compressible and
flexible to allow one endplate 1 to move relative to the other
endplate 11. As the body 10 compresses and flexes, the motion
limiting members 5 of the superior endplate 1 intermesh with the
motion limiting members 15 of the inferior endplate 11.
[0079] In the embodiment shown in FIG. 11, the body 10 is made of a
single material and is homogeneous. In the embodiment shown in FIG.
12, the body 10 is made of different materials. The body 10 has
three layers 61 and 62. The outer layers 61 are made of a first
material. The inner layer 62 is made of a second material. The
first material has different mechanical properties (i.e.
flexibility, resiliency, durability, etc.) than the second
material. The material or materials of the body 10 are selected to
match a desired flexibility of the device 20. The body 10 can be
made to flex like the original anatomy or within the mechanical
limits of the device 20.
[0080] In the embodiments shown in FIGS. 13 and 14, a fixed bone
spacer is used as the core. The fixed bone spacer is not flexible.
Accordingly, the endplates 1 and 11 do not move relative to each
other when the fixed bone spacer is used as the body 10. FIG. 13
shows an embodiment with a standing expanding cage as the core. An
example of a standing expandable cage is taught in U.S. Pat. No.
7,384,431, which is incorporated by reference herein. FIG. 14 shows
an embodiment in which a standing single body cage is used as the
body 10. Screws 30 are inserted through the body 10 into the
pedicle of the vertebra to fix the body to the vertebra. The device
20 provides a device that can be used for an anterior installation
with greater stability than an expanding cage alone.
[0081] A preferred embodiment of the invention includes a method of
stabilizing a first vertebra relative to a second vertebra after a
discectomy. An incision is made to an anterior aspect of an
intervertebral disc of the spine. Next, the intervertebral disc is
removed via the anterior incision. If a prosthesis had been
inserted previously to replace an intervertebral disc, the
prosthesis can be removed via the incision. Next, the device is
inserted into the intervertebral space from which the disc was
removed. The joint can be expanded or the device compressed to help
insert the device 20 into the intervertebral space. To compress the
device 20, the superior endplate 1 can be pressed toward the
inferior endplate 11 to compress the body 10. When inserting the
device 20, the anterior edge 117 is aligned along the anterior of
the spine. When the device 20 is inserted, the superior surface 8
of the superior endplate 1 presses against the superior vertebra.
Likewise, the inferior surface 18 of the inferior endplate presses
against the inferior vertebra. To fix the device 20 to the
vertebra, a screw is inserted through the socket 3 of the screw
anchor member 2 into the anterior face of the body of the superior
vertebra. Likewise, a screw 30 is inserted through the socket 13 of
the screw anchor member 12 into the anterior face of the body of
the inferior vertebra. Next, the incision is closed.
[0082] When the superior endplate 1 is connected to the superior
vertebra and the inferior endplate 11 is connected to the inferior
vertebra, the device 20 preserves movement along six degrees of
freedom: X-axis: flexion/extension, lateral slip; Y-axis:
Left/Right Axial Rotation; Anterior/Posterior Slip; Z-Axis:
Left/Right Lateral Bending, Axial tension/compression. A
practitioner can determine a permissible range of motion by
configuring the body 10 and the spacing and size of the motion
limiting members 5 and 15.
[0083] A preferred embodiment of a method for providing soft
stabilization utilizes a locking plate 40. The device 20 is
installed as described previously. Next, a locking plate 40 is
placed over the device 20. The horizontal plate 42 is placed to
overly the endplates 1 and 11. The superior screw anchor member 41
is placed on the anterior face of the superior vertebra. The
superior screw anchor member 41 is aligned vertically above the
anterior motion limiting member 15 on the inferior endplate 11. The
superior screw anchor member 41 is placed so a medial contact
surface 46 abuts a medial contact surface 9 of the superior screw
anchor member 2 of the superior endplate 1. Likewise, the inferior
screw anchor member 45 is placed so its medial contact surface 47
abuts a medial contact surface 19 of the inferior screw anchor
member 12 of the inferior endplate 11. The locking plate 40 limits
the motion of the first endplate 1 with respect to the second
endplate 11. However, depending on the qualities of the body 10,
some motion still may be provided even when the locking plate 40 is
installed.
[0084] A preferred embodiment of a method for stabilizing a
vertebra with respect to another vertebra following a corpectomy
utilizes the device 20. An incision is made to an anterior surface
of a vertebra. The body of the vertebra is removed during the
corpectomy. The device 20 is delivered to the site where the body
of the vertebra was removed via the anterior incision. In the
preferred embodiment, the body 10 is not flexible and has a height
so the overall height of the device 20 including the superior
endplate 1, body 10, and inferior endplate 11 is substantially
equal to the height of the vertebra being replaced. "Substantially"
is used to denote that the height may not be exactly the same as
the vertebra being replaced. For example, if the vertebra being
replaced was damaged, or compressed, the device 20 might need a
height slightly greater or less than the vertebra being replaced.
The body 10 can be a rigid homogenous piece of material or have
layers of different stiffness. In a preferred embodiment, the body
10 is a self-standing expanding cage. The expanding cage is
operated to adjust a height of the self-standing expanding cage to
match the height of the vertebra being replaced. In another
embodiment, the body 10 is a self-standing single body cage. Screws
are inserted from an anterior side into the pedicle of the
vertebrae that has had its body removed. In one embodiment, the
body 10 is fastened to each of the superior endplate 1 and inferior
endplate 11 with respective screws 30.
[0085] While it is apparent that the invention disclosed herein is
well calculated to fulfill the objects stated above, it will be
appreciated that numerous modifications and embodiments may be
devised by those skilled in the art.
* * * * *