U.S. patent application number 16/280284 was filed with the patent office on 2019-06-20 for spinal implant assembly.
This patent application is currently assigned to Fitzbionics Limited. The applicant listed for this patent is Fitzbionics Limited. Invention is credited to Noel Fitzpatrick.
Application Number | 20190183537 16/280284 |
Document ID | / |
Family ID | 48226594 |
Filed Date | 2019-06-20 |
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United States Patent
Application |
20190183537 |
Kind Code |
A1 |
Fitzpatrick; Noel |
June 20, 2019 |
SPINAL IMPLANT ASSEMBLY
Abstract
A spinal implant assembly comprising an intervertebral device
configured to be installed in a spinal disc space, the
intervertebral device having a head component and a body component,
the spinal implant assembly further comprising a coupling body for
coupling the head component of the intervertebral device and an
elongate member, the coupling body and head component each having a
longitudinal axis, wherein the head component can be received by
the coupling body with its longitudinal axis at a selected angle
within a predetermined range of angles relative to the longitudinal
axis of the coupling body.
Inventors: |
Fitzpatrick; Noel;
(Godalming, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Fitzbionics Limited |
Godalming |
|
GB |
|
|
Assignee: |
Fitzbionics Limited
Godalming
GB
|
Family ID: |
48226594 |
Appl. No.: |
16/280284 |
Filed: |
February 20, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15634277 |
Jun 27, 2017 |
10245076 |
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16280284 |
|
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14778280 |
Sep 18, 2015 |
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PCT/GB2014/050570 |
Feb 26, 2014 |
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15634277 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 2034/108 20160201;
A61B 2017/00526 20130101; A61F 2/446 20130101; A61B 17/864
20130101; A61F 2002/449 20130101; A61B 17/7002 20130101; A61B
17/7037 20130101; A61B 34/10 20160201; A61B 17/7005 20130101; A61F
2002/30405 20130101; A61B 17/8685 20130101; A61F 2002/30622
20130101; A61B 17/7032 20130101; A61F 2002/30433 20130101; A61F
2/30942 20130101 |
International
Class: |
A61B 17/70 20060101
A61B017/70; A61F 2/30 20060101 A61F002/30; A61B 17/86 20060101
A61B017/86; A61B 34/10 20060101 A61B034/10; A61F 2/44 20060101
A61F002/44 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 18, 2013 |
GB |
1304921.8 |
Claims
1. A spinal implant assembly comprising an intervertebral device
configured to be installed in a spinal disc space, the
intervertebral device having a head component and a body component,
the spinal implant assembly further comprising a coupling body for
coupling the head component of the intervertebral device and an
elongate member, the coupling body and head component each having a
longitudinal axis, wherein the head component can be received by
the coupling body with the longitudinal axis of the head component
at a selected angle within a predetermined range of angles relative
to the longitudinal axis of the coupling body.
2. A spinal implant assembly according to claim 1, wherein the
assembly further comprises an elongate member, the coupling body
receiving the elongate member and the head component of the
intervertebral device when assembled.
3. A spinal implant assembly according to claim 1, wherein the head
component of the intervertebral device is releasably attachable to
the body component.
4. A spinal implant assembly according to claim 1, wherein the head
component of the intervertebral device is releasably attachable to
the body component via a threaded connection.
5. A spinal implant assembly according to claim 1, wherein the head
component has a head portion and a shank portion, the shank portion
being at least partially externally threaded, the body component
having a bore with a first open end, the bore being at least
partially internally threaded, the internal threads of the bore
corresponding with the external threads of the shank portion of the
head component such that the head component is releasably
attachable to the body component.
6. A spinal implant assembly according to claim 1, wherein the head
portion of the head component is at least partially spherical, and
the coupling body comprises a hollow tubular body, the head portion
of the head component being receivable in the hollow tubular body,
and wherein the coupling body has a first opening in a first end
and a second opening in a second end, the first opening being
larger in diameter than that of the head portion and the second
opening being smaller in diameter than that of the head portion, a
portion of the inner surface of the coupling body having a
concavely curved inner surface, the curved inner surface
corresponding with the at least partially spherical head portion,
such that the head component may be positioned polyaxially relative
to the coupling body when assembled.
7.-8. (canceled)
9. A spinal implant assembly according to claim 1, wherein the
coupling body has at least a first slot.
10. A spinal implant assembly according to claim 9, wherein the
coupling body has a second slot.
11. A spinal implant assembly according to claim 1, wherein the
elongate member comprises a rod.
12. A spinal implant assembly according to claim 1, wherein the
elongate member has a first end that is at least partially
spherical.
13. A spinal implant assembly according to claim 12, wherein the
elongate member has a second end that is at least partially
spherical.
14. A spinal implant assembly according to claim 1, wherein the
assembly further comprises a washer for location between the head
component and the elongate member when assembled.
15. A spinal implant assembly according to claim 14, wherein the
washer has first and second opposing surfaces, the first surface
being concavely curved and facing the first end of the elongate
member when assembled.
16. A spinal implant assembly according to claim 14, wherein the
washer has first and second opposing surfaces, the first surface
having an elongate groove for receiving the elongate member when
assembled.
17. A spinal implant assembly according to any of claim 14, wherein
the washer has first and second opposing surfaces, the second
surface being concavely curved and facing the head component when
assembled.
18. A spinal implant assembly according to claim 1, wherein at
least part of the body component of the intervertebral device is
externally tapered.
19. A spinal implant assembly according to claim 18, wherein the
body component has a proximal end and a distal end and the external
taper of the body component tapers towards the proximal end of the
bolt.
20. A spinal implant assembly according to claim 1, wherein at
least part of the body component is externally threaded.
21. A spinal implant assembly according to claim 1, wherein the
body component has a hollow bore.
22. A spinal implant assembly according to claim 21, wherein the
head component has a shank portion insertable within the hollow
bore of the body component, the shank portion of the head component
being shorter in length than the hollow bore of the body component
such that with the shank portion fully inserted in the body
component, at least some hollow space in the hollow bore remains
unoccupied by the shank portion.
23. A spinal implant assembly according to claim 21, wherein the
body component has at least one aperture, the aperture
communicating with the hollow bore.
24.-32. (canceled)
Description
FIELD OF THE INVENTION
[0001] The invention relates to a spinal implant assembly. More
specifically the invention relates to assemblies with parts for
implantation into intervertebral space between adjacent vertebrae
of the spine.
BACKGROUND TO THE INVENTION
[0002] The spine or vertebral column comprises a plurality of
separate vertebrae. The vertebrae are movable relative to one
another, and separated from one another by fibrocartilage called
inter-vertebral discs.
[0003] In its entirety, the spinal column is highly complex in that
it houses and protects critical elements of the nervous system
which have innumerable peripheral nerves and arterial and venous
bodies in close proximity. In spite of these complexities, the
spine is a highly flexible structure, capable of a high degree of
curvature and twist through a wide range of motion. The
intervertebral discs provide mechanical cushion between adjacent
vertebrae. Genetic or developmental irregularities, trauma, chronic
stress, tumors, and disease, however, can result in spinal
pathologies which either limit this range of motion, or which
threaten the critical elements of the nervous system housed within
the spinal column. A variety of systems have been disclosed in the
art which achieve immobilization by implanting artificial
assemblies in or on the spinal column.
[0004] In order to treat certain injuries or conditions of the
spinal column an intervertebral device may be placed in the
intervertebral disc space to fuse or promote fusion of adjacent
vertebrae. Such fusion devices are often used in combination with
stabilisation systems wherein a metal rod that is bendable to match
the natural curvature of the spine is mechanically attached at
strategically selected vertebrae, allowing the rod to be rigidly
fixed to the spine. This provides a rigid support to the spinal
column. For this, pedicle screws located in the bone structure are
typically fixed to a specially designed clamp to attach to a spinal
rod. A problem with these stabilisation systems is that parts of
the vertebra cannot stably receive a bone screw, or can only
receive a bone screw screwed in at a certain angle. Also, for
spinal fixings for small animals, within the confined spaces
allowed therein, conventional rod anchoring methods are not
suitable since the placement of the pedicle screw and the direction
of the rod cannot be matched adequately. A system that can be used
in small animals is needed, wherein confined spaces make
conventional rod anchoring systems unsuitable. Furthermore, many
devices for providing positioning of bone screws with respect to a
stabilising rod loosen over time, providing an unstable joint.
There is therefore a need for a solution that overcomes one or more
of these problems.
SUMMARY OF INVENTION
[0005] According to a first aspect of the invention there is
provided a spinal implant assembly comprising an intervertebral
device configured to be installed in a spinal disc space, the
intervertebral device having a head component and a body component,
the spinal implant assembly further comprising a coupling body for
coupling the head component of the intervertebral device and an
elongate member, the coupling body and head component each having a
longitudinal axis, wherein the head component can be received by
the coupling body with the longitudinal axis of the head component
at a selected angle within a predetermined range of angles relative
to the longitudinal axis of the coupling body. Suitably the head
component can be adjusted polyaxially relative to the coupling
body.
[0006] The intervertebral device provides a stable anchorage for
the spinal stabilisation system provided by the elongate
member.
[0007] Suitably the spinal implant assembly can be adapted to
provide a locked configuration, wherein the head component and/or
elongate member are locked in position relative to the coupling
body, and an adjustable configuration, wherein the position of the
head component and/or elongate member relative to the coupling body
can be adjusted.
[0008] Preferably the assembly further comprises an elongate
member, the coupling body receiving the elongate member and the
head component of the intervertebral device when assembled.
[0009] The head component and body component can be integral,
however preferably are releasably attachable to one another.
[0010] Preferably the head component of the intervertebral device
is releasably attachable to the body component via a threaded
connection.
[0011] Preferably the head component has a head portion and a shank
portion, the shank portion being at least partially externally
threaded, the body component having a bore with a first open end,
the bore being at least partially internally threaded, the internal
threads of the bore corresponding with the external threads of the
shank portion of the head component such that the head component is
releasably attachable to the body component.
[0012] Preferably the head portion of the head component is at
least partially spherical.
[0013] Preferably the coupling body comprises a hollow tubular
body, the head portion of the head component being receivable in
the hollow tubular body.
[0014] Preferably the coupling body has a first opening in a first
end and a second opening in a second end, the first opening being
larger in diameter than that of the head portion and the second
opening being smaller in diameter than that of the head portion, a
portion of the inner surface of the coupling body having a
concavely curved inner surface, the curved inner surface
corresponding with the at least partially spherical head portion,
such that the head component may be positioned polyaxially relative
to the coupling body when assembled.
[0015] Preferably the coupling body has at least a first slot.
Suitably the elongate member suitably extends through the first
slot when assembled with the coupling body. The slot communicates
with the first open end of the coupling body. In some embodiments,
when assembled, the elongate member can pivot relative to the
coupling body, within the first slot, over a pre-determined range
of motion.
[0016] Preferably the coupling body has a second slot. Suitably the
elongate member extends through the second slot when assembled with
the coupling body. The first and/or second slots preferably are
elongate, the or each slot having a longitudinal axis parallel with
the longitudinal axis of a bore of the coupling body. Where the
elongate member is a rod, the elongate member will extend through
both the first and second slots when assembled, the first and
second slots effectively providing a rod receiving channel.
[0017] Preferably the elongate member comprises a rod.
[0018] Preferably the elongate member has a first end that is at
least partially spherical. Preferably the elongate member has a
second end that is at least partially spherical.
[0019] Preferably the assembly further comprises a washer for
location between the head component and the elongate member when
assembled.
[0020] Preferably the washer has first and second opposing
surfaces, the first surface being concavely curved and facing the
first end of the elongate member when assembled. Such a washer will
be used to engage the elongate member when it has a first end that
is at least partially spherical.
[0021] Preferably the washer has first and second opposing
surfaces, the first surface having an elongate groove for receiving
the elongate member when assembled. Such embodiments are suitable
for use with a rod-like elongate member.
[0022] Preferably the washer has first and second opposing
surfaces, the second surface being concavely curved and facing the
head component when assembled.
[0023] Preferably at least part of the body component of the
intervertebral device is externally tapered.
[0024] Preferably the body component has a proximal end and a
distal end and the external taper of the body component tapers
towards the proximal end of the bolt. In this context the term
proximal used in relation to parts of spinal implants or spinal
fixings means located nearer or towards the centre of the subject's
body or spine when the implant part or fixing part is installed and
distal means located away from the centre of the body or spine when
the implant part or fixing part is installed. The term subject as
used herein can be a human or animal subject.
[0025] The maximum diameter of the body component at any point
along its longitudinal axis is greater than the opening in the
second open end of the coupling body. In this way, the coupling
body can be compact whilst the body component can be large in
diameter, suitable for vertebral distraction and stable anchoring
in the disc space.
[0026] Preferably at least part of the body component is externally
threaded.
[0027] Preferably the body component has a hollow bore.
[0028] Preferably the head component has a shank portion insertable
within the hollow bore of the body component, the shank portion of
the head component being shorter in length than the hollow bore of
the body component such that with the shank portion fully inserted
in the body component, at least some hollow space in the hollow
bore remains unoccupied by the shank portion. This allows for bone
ingrowth into the body component when installed, thus improving the
stability of the anchorage.
[0029] Preferably the body component has at least one aperture, the
aperture communicating with the hollow bore. Suitably said at least
one aperture is not obscured, or is only partially obscured, by the
shank portion of the head component when assembled, such that the
aperture communicates with the hollow bore when the spinal implant
assembly is assembled.
[0030] Preferably at least part of the body component is
hydroxyapatite coated.
[0031] Preferably the assembly further comprises a compression
member for compressing the elongate member and the head component
in locking engagement within the coupling body.
[0032] Preferably the compression member is a locking screw. The
locking screw may be externally threaded, the coupling body having
a bore with first and second open ends, at least part of the bore
being internally threaded, the internal threads of the bore
corresponding with the external threads of the locking screw.
Preferably the assembly further comprises a ring, configured to be
received around the coupling body when assembled.
[0033] There is also provided a spinal implant system comprising
two or more spinal implant assemblies according to any previous
aspect of the invention and an elongate member, wherein the
assemblies are configured to be coupled together using the elongate
member. This provides a system wherein a first implant assembly can
be installed in a first disc space and a second implant assembly
can be installed in a second, adjacent disc space, and the spine
can be stabilised by the coupling of the implant assemblies using
the elongate member. Further implant assemblies installed in
further disc spaces can be assembled, all being coupled by a single
elongate member. Alternatively a first implant assembly can be
installed in a disc space and a second implant assembly can be
installed in the same disc space.
[0034] The assembly can also be used as part of a spinal implant
system comprising a spinal implant assembly according to any
preceding claim and an elongate member, wherein the system further
comprises a spinal fixing comprising a bone fastener configured to
be installed into bone and a coupling body for receiving the bone
fastener and said elongate member such that the elongate member
couples the spinal implant assembly and spinal fixing when the
system is assembled. The bone fastener may be a pedicle screw for
example, suitable for installation into a vertebra.
[0035] There is also provided a kit for assembly into a spinal
implant assembly or system, wherein the kit comprises the parts of
the assembly according to any previous aspect of the invention. A
modular kit can be provided wherein intervertebral devices of
differing dimensions are provided, for example.
[0036] There is also provided a computer program embodied on a
computer readable medium for manufacturing a spinal implant
assembly or system to any previous aspect of the invention.
[0037] There is also provided a method of installing a spinal
implant assembly, the method comprising the steps of providing a
spinal implant assembly, the spinal implant assembly comprising an
intervertebral device configured to be installed in a spinal disc
space, the intervertebral device having a head component and a body
component, the spinal implant assembly further comprising a
coupling body for coupling the head component of the intervertebral
device and an elongate member, the coupling body and head component
each having a longitudinal axis, wherein the head component can be
received by the coupling body with its longitudinal axis at a
selected angle within a predetermined range of angles relative to
the longitudinal axis of the coupling body, the method further
comprising [0038] implanting the body component of the
intervertebral device between adjacent vertebrae or between a
vertebra and the sacrum; [0039] coupling the intervertebral device
with the coupling body, before or after implanting the body
component, wherein the head component can be received by the
coupling body such that its longitudinal axis is at a selected
angle within a predetermined range of angles relative to the
longitudinal axis of the coupling body.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] A preferred embodiment of the present invention will now be
more particularly described by way of example only with reference
to the accompanying drawings, wherein:
[0041] FIG. 1 is an exploded view of a spinal implant assembly;
[0042] FIG. 2 is a perspective view of the assembly of FIG. 1,
assembled together;
[0043] FIG. 3 is a side view of the assembly of FIG. 2, but with
the longitudinal axis of the intervertebral device shown
non-parallel with that of the coupling body;
[0044] FIG. 4 is a cross-sectional view of the assembly of FIG.
2;
[0045] FIGS. 5 to 7 show another embodiment, similar to that of
FIGS. 1 to 4, but wherein the elongate member is a dumbbell rather
than a rod;
[0046] FIG. 5 is an exploded view of a spinal implant assembly;
[0047] FIG. 6 is a perspective view of the assembly of FIG. 4,
assembled together;
[0048] FIG. 7 is a cross-sectional view of the assembly of FIG.
6.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0049] The present embodiments represent currently the best ways
known to the applicant of putting the invention into practice. But
they are not the only ways in which this can be achieved. They are
illustrated, and they will now be described, by way of example
only.
[0050] Referring to FIG. 1, this shows a spinal implant assembly 10
according to a first embodiment. The assembly can be used to fuse
two or more vertebra together, in order and to provide
stabilisation of the spine. The assembly 10 comprises an
intervertebral device 20, an elongate member 30 and a coupling body
40. The assembly is designed such that the intervertebral device 20
can be coupled for multiaxial positioning relative to the coupling
body 40 and elongate rod 30.
[0051] The intervertebral device 20 comprises a body component 20a
and a head component 20b. The body component 20a of the
intervertebral device is configured for installation in a spinal
disc space between any two vertebrae of a subject, including the
space between the sacrum and the adjacent vertebra. The body
component 20a of the intervertebral device is a tapered bolt that
can be used to induce fusion and distraction when implanted. The
bolt 20a has a proximal end 21 and a distal end 22, and is tapered
towards the proximal end 21. The external surface of the bolt 20a
is threaded with deep threads for cutting into vertebral bone on
either side of the spinal disc space. The threads are thin in
section and very pronounced, to cut into the bone and aid the
insertion process.
[0052] The bolt 20a has a hollow bore. The proximal end 21 is
closed and the distal 22 end is open. Alternatively, the proximal
end 21 may be open. The hollow bore is internally threaded, at
least partially, at or near the distal end 22 of the bolt.
[0053] The bolt has a first elongate slot 23, having a longitudinal
axis running parallel with the longitudinal axis of the bolt 20.
The bolt has a second elongate slot opposite the first elongate
slot (not visible in the figures). The bolt may have more than two
elongate slots. The outer surface of the bolt 20 may have a
hydroxyapatite coating to stimulate bone ingrowth.
[0054] The head component 20b of the intervertebral device has a
head portion 51 and a shank portion 52. The shank portion 52 has an
externally threaded portion 53 and an enlarged shoulder 54. The
externally threaded shank portion 52 is receivable within the
hollow bore of the bolt 20a, the external threads of the shank
portion 52 corresponding with the internal threads of the hollow
bore of the bolt 20a, such that the head component 20b is
releasably attachable to the bolt 20a. The enlarged shoulder 54
butts up against the distal end 22 of the bolt 20a when the shank
portion 52 is fully inserted in the bolt 20a.
[0055] The head portion 51 and shank portion 52 of the head
component 20b are preferably integral with one another. The head
portion 51 comprises a substantially spherical head with a female
recess 55 at its distal end. The recess is hexagonal in shape. The
recess 55 can receive a wrench or other torque-transferring tool,
for transferring torque to the head component 20b during assembly,
to assemble it to the bolt 20a. Alternatively, the recess 55 may be
a shape other than hexagonal, the shape being suitable for
receiving torque transfer from a suitable tool. In an alternative
embodiment the head portion 51 can comprise a part-spherical
portion and removable rocker, to form a substantially complete ball
end. The term part-spherical as used herein refers to a surface
that comprises a portion of a sphere.
[0056] The coupling body 40 comprises a tubular, hollow body. The
coupling body 40 has a bore 41 having first and second open ends.
The first and second open ends each have an opening that is
circular in shape 42,43, the first opening communicating with first
and second elongate slots 44, 45, disposed in opposite sides of the
coupling body 40. The elongate slots 44,45 extend from the first
opening 42, part of the way down the side of the coupling body 40.
The elongate slots 44, 45 form a channel for receiving the elongate
member 30 when assembled. The second opening 43, in the proximal
end, is smaller in diameter than the first opening 42. The first
opening 42 is large enough to receive the head portion 51 of the
head component 20b therethrough. The second opening 43 is
surrounded by a curved inner surface, internally to the coupling
body 40. The curvature of the curved inner surface corresponds to
the curvature of the head portion 51, such that the head portion 51
can pivot smoothly in the coupling body 40 within a pre-determined
range of angles relative to the coupling body 40 when the head
component 20b is received within the coupling body 40.
[0057] The assembly further comprises a washer 60, located between
the head component 20b and the elongate member 30 when assembled.
The washer 60 is circular in shape, having first and second
opposing surfaces 61, 62 (top and bottom surfaces, or distal and
proximal surfaces). The first surface 61 has an elongate groove 63
for receiving the elongate member 30 when assembled. The second
surface 62 is concavely curved (not visible in the figures). The
groove 63 in the first surface and concavely curved second surface
form sockets for receiving the elongate member 30 and head portion
51 respectively. The intermediate conforming washer 60 increases
the surface contact area that would exist between the head portion
51 and the elongate member 30, if the washer were not present. The
washer allows the distribution of loads evenly between the head
portion 51 and the elongate member 30.
[0058] In some embodiments the sockets in the washer conform in
shape with the corresponding piece of the assembly to be received
therein. In alternative embodiments, the first and second surfaces
of the washer may include one or more points or edges that, when
the assembly is subjected to compressive force by a locking member
70 (described below), bite into the respective members the washer
engages with. The axial mouth of the groove 63 may have a
transverse diameter that is smaller than the radius of the elongate
member. Similarly the radius of curvature of the second surface 62
may be slightly less than the radius of curvature of the head
portion 51. This non-conformance between the sockets in the first
and second surfaces of the washer and the corresponding head
portion and elongate member provides an edge contact between the
socket and the member to be received therein, which enhances the
locking mechanism provided by the washer.
[0059] The elongate extension 30 is a rod. The rod may of course be
long or short, and may be fixed to the subject using another fixing
device at its end or at one or more points along the length of the
rod. The rod may be longer than as shown in FIGS. 1 to 3. The rod
may be straight or curved. The rod may be flexible, such that it
can be curved into a desired shape by the surgeon during
installation.
[0060] The assembly further comprises a locking screw 70, which
acts as a compression member in use, to compress the elongate
member 30, washer 60, and head component 20b together, against the
inside of the coupling body 40, and therefore to lock the head
component 20b at a selected angular orientation relative to the
coupling body 40. The locking screw 70 has a circular
cross-section, and has externally threaded sides. The coupling body
40 has internal threading on at least part of its internal surface,
near to the first opening 42. The internal threads of the coupling
body 40 correspond with the external threads of the locking screw
70. The locking screw 70 can be screwed into the first opening 42
of the coupling body, thus providing a compressive force on the
elongate member 30, washer 60 and head component 20b. The locking
screw 70 has a hexagonal shaped recess 71 in its top surface
(distal surface), which can receive a hexagonal shaped
torque-transferring tool for tightening the locking screw 70 in
threaded engagement in bore 41. Alternatively the recess 71 may be
a shape other than hexagonal, the shape being suitable for
receiving torque transfer from a suitable tool.
[0061] The FIG. 1 embodiment also includes a further optional
feature, ring 80. The ring 80 is a circular piece which is shaped
and dimensioned to sit in a recessed region 46 in the outer wall of
the distal end of the coupling body 40, as shown assembled in FIG.
2. The ring 80 is placed in the recessed region 46, the ring 80
butting up against a shoulder on the outer wall of the coupling
body 40. The ring 80 is usually placed around the coupling body 40
before the locking screw 70 is tightened. The ring 80 captivates
the distal end of the coupling body 40, preventing the split distal
end of the coupling body from springing apart as the locking screw
70 is tightened. The ring is shown in the embodiment of FIGS. 1 to
4, but it is an optional part of the assembly.
[0062] In operation, in order to assemble the spinal implant
assembly and install it in a subject, the shank portion 52 of the
head component 20b is inserted, through the first opening 42, then
through the second opening 43 of the bore 41 of the coupling body
40, until the head portion 51 butts up against the internal edges
of the second opening 43. A torque-transferring tool, such as a
wrench, is received in recess 55 to threadedly secure the head
component 20b to the bolt 20a. The bolt 20a may already be
installed in a subject's disc space or may be installed in a
subject's disc space after the head component 20b with coupling
body 40 assembled thereto is secured to the bolt 20a.
[0063] When installing the bolt 20a in the subject it is inserted
in the disc space between adjacent vertebrae or at the lumbo-sacral
joint. The threads on the external surface of the bolt 20a cut into
the bone during insertion. The hollow bore of the bolt 20a can be
impregnated with bone graft before insertion of the bolt 20a in the
subject. The subject's bone will ingrow, through the elongate slots
23, and attach with the bone graft inside the hollow section of the
bolt 20a. This further anchors the bolt 20a in the subject. Even if
no bone graft is inserted in the hollow of the bolt 20a before
implantation of the bolt 20a into the subject, cutting of the
subject's bone by the bolt threads as the bolt is inserted will
create bone debris that will accumulate, via the elongate slots 23,
in the hollow bore of the bolt 20a. The subject's bone will ingrow,
through the elongate slots 23, and attach with the accumulated bone
debris, further anchoring the bolt 20a against rotation.
[0064] The washer is then inserted in the coupling body, with the
second surface 62 facing the head component 20b, then the elongate
member 30 is inserted in the slots 44, 45 of the coupling body
40.
[0065] With the assembly assembled as described above, the coupling
body 40 can pivot relative to the anchored intervertebral device 20
(comprising the bolt 20a and head component 20b), giving rise to
polyaxial positioning within a predetermined angle range.
Therefore, the assembly is in this adjustable configuration, it
provides a polyaxial or universal joint between the bolt 20a and
the coupling body 40 and also between the bolt 20a and the elongate
member 30. The elongate extension can slide within the slots 44,
45, relative to the coupling body 40. The locking screw 70 can be
tightened within the threaded bore 41, with the ring 80 in place
around the coupling body 40, to compress the head component 20b,
washer 60 and elongate member 30 together, against the inside of
the coupling body 40, until the elongate member 30 and
intervertebral device 20 are locked, relative to the coupling body,
such that they can no longer be positionally adjusted. An assembled
device is shown in FIG. 2. A further assembled device in which the
longitudinal axis of the intervertebral device 20 is non-parallel
with that of the coupling body 40 is shown in FIG. 3.
[0066] The spinal implant assembly can be provided as part of a
system in which two or more spinal implant assemblies, as described
above, are coupled by a single elongate member 30. A first implant
assembly can be installed in a first disc space and a second
implant assembly can be installed in a second, adjacent disc space,
and the spine can be stabilised by the coupling of the implant
assemblies using the elongate member. Alternatively a first implant
assembly can be installed in a disc space and a second implant
assembly can be installed in the same disc space.
[0067] Instead of a bolt, the body component 20a may be an
interbody cage.
[0068] The spinal implant assembly can also be provided as part of
a system in which one or more spinal implant assemblies, as
described above, are coupled to at least one spinal fixing having a
simple pedicle screw or other bone fixing means, which is
coupleable to the elongate member 30 via a suitable coupling
body.
[0069] FIGS. 5 to 7 show an alternative embodiment for a spinal
implant assembly 110 similar to that of FIGS. 1 to 4. The same
reference numerals have been used in FIGS. 5 to 7 to refer to
components which are substantially the same as those in the
previous embodiment. The implant assembly 110 differs from that of
FIGS. 1 to 4 in that the elongate member 130 in the FIG. 5
embodiment has first and second ball ends 131, 132 joined by a rod
portion 134. Each ball end 131, 132 is substantially spherical,
such that the elongate member 130 is like a dumbbell. Each ball end
131, 132 can have a diameter that is substantially the same as that
of the head portion 51 of head component 20b.
[0070] For the embodiment of FIG. 5, both the first and second
surfaces 161 of the washer 160 will be concavely curved. The washer
161 has a notch 164 extending between the first surface 161 and the
side of the washer. When assembled, the notch 164 faces toward the
rod portion 134 of the elongate member 130.
[0071] The coupling body 141 only has one slot 144 (although it can
have a second slot on the opposing side).
[0072] The underside 171 of the locking screw 170 has a concavely
curved surface corresponding with the curvature of the first ball
end 131 of the elongate member 130. The elongate member can pivot
relative to the coupling body 140, along the axis of slot 144, when
the locking screw 170 is not fully tightened. The notch 164 in the
washer 160 allows for a greater range of movement when the elongate
member 130 pivots within slot 144.
[0073] The second ball end 132 can be received within the coupling
body 40 of a second spinal implant assembly like that of FIG. 5, or
some other spinal implant assembly (such as an assembly including a
pedicle screw rather than an intervertebral device with detachable
head component).
[0074] In alternative embodiments, the elongate member 130 may have
only a first ball end 130 which is received by the coupling body
40, the elongate member forming a simple rod extending from the
first ball end 130.
[0075] Like the embodiment of FIGS. 1 to 4, the assembly of FIGS. 5
to 7 allows polyaxial positioning of the bolt 20a relative to the
coupling body 140 when the assembly is in an adjustable
configuration (when the locking member 170 is not tightly
compressing the assembly components) but not when the assembly is
in a locked configuration (when the locking member not tightly
compressing the assembly components).
[0076] The embodiment of FIGS. 5 to 7 is installed in a very
similar manner to that of FIGS. 1 to 4.
* * * * *