U.S. patent application number 14/500057 was filed with the patent office on 2015-01-15 for minimally invasive corpectomy cage and instrument.
This patent application is currently assigned to DEPUY SYNTHES PRODUCTS, LLC. The applicant listed for this patent is DEPUY SYNTHES PRODUCTS, LLC. Invention is credited to William Frasier.
Application Number | 20150018953 14/500057 |
Document ID | / |
Family ID | 43030990 |
Filed Date | 2015-01-15 |
United States Patent
Application |
20150018953 |
Kind Code |
A1 |
Frasier; William |
January 15, 2015 |
MINIMALLY INVASIVE CORPECTOMY CAGE AND INSTRUMENT
Abstract
An assembly comprising an expandable corpectomy cage and an
insertion instrument, wherein the expandable cage comprises an
instrument attachment features, including mating holes on the sides
of the outer sleeve, and a ball-shaped pocket on the endplate of
the inner sleeve, and the insertion instrument features a
tuning-fork shaped holder, which attaches to the mating holes on
the implant's outer sleeve using small bosses which mate with the
holes under the spring tension of the fork, and a lever with a
spherical end that mates with the ball-shaped pocket in the inner
sleeve endplate.
Inventors: |
Frasier; William; (New
Bedford, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DEPUY SYNTHES PRODUCTS, LLC |
Raynham |
MA |
US |
|
|
Assignee: |
DEPUY SYNTHES PRODUCTS, LLC
Raynham
MA
|
Family ID: |
43030990 |
Appl. No.: |
14/500057 |
Filed: |
September 29, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12432117 |
Apr 29, 2009 |
8876905 |
|
|
14500057 |
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Current U.S.
Class: |
623/17.15 |
Current CPC
Class: |
A61F 2002/30538
20130101; A61F 2002/30495 20130101; A61F 2250/0006 20130101; A61F
2002/3055 20130101; A61F 2002/30601 20130101; A61F 2/4611 20130101;
A61F 2002/30507 20130101; A61F 2002/30579 20130101; A61F 2/44
20130101; A61F 2002/30522 20130101; A61F 2002/30242 20130101; A61F
2230/0071 20130101; A61F 2220/0025 20130101; A61F 2002/30841
20130101; A61F 2002/30787 20130101; A61F 2/4465 20130101; A61F
2002/30224 20130101; A61F 2002/30593 20130101 |
Class at
Publication: |
623/17.15 |
International
Class: |
A61F 2/44 20060101
A61F002/44; A61F 2/46 20060101 A61F002/46 |
Claims
1. A method of inserting an expandable spinal corpectomy cage into
a defect space between a pair of vertebral bodies, the cage
comprising i) an outer member having a first endplate and opposing
attachment features defining a rotation axis, and ii) an inner
member having a second endplate, wherein the inner member is
received within the outer member and is axially adjustable relative
thereto in an axial direction thereof for adjusting the variable
axial height of the cage, the method comprising the steps of: a)
attaching the attachment features of the expandable cage to an
insertion instrument, b) inserting the expandable cage into the
defect space in an orientation in which the axis of the cage is
substantially orthogonal to an axis of the spine, and c)
manipulating the insertion instrument to rotate the expandable cage
about the rotation axis so that the axis of the cage is
substantially parallel to the axis of the spine.
2. The method of claim 1 wherein each of the outer and inner
members are sleeves.
3. The method of claim 2 wherein the outer sleeve comprises an
inner wall and an outer wall having a pair of recesses thereon
adapted for mating with the instrument.
4. The method of claim 3 wherein the inner sleeve comprises an
outer wall and an end plate having a substantially spherical pocket
thereon adapted for mating with the instrument.
5. The method of claim 2 wherein the outer sleeve comprises an
inner wall and an outer wall having a substantially spherical
pocket thereon adapted for mating with a first portion of the
instrument.
6. The method of claim 5 wherein the inner sleeve comprises an
outer wall and an end plate having a pair of recesses thereon
adapted for mating with a second portion of the instrument.
7. The method of claim 2 wherein the instrument comprises a fork
comprising a proximal shaft, an intermediate crossbar, and a distal
portion comprising a pair of extensions, each extension having a
pair of opposing bosses.
8. The method of claim 7 wherein the instrument comprises a lever
having a proximal shaft, an intermediate portion and a spherical
distal end.
9. The method of claim 8 wherein the intermediate portion of the
lever pivots upon the fulcrum.
10. The method of claim 9 wherein the outer member comprises an
inner wall and an outer wall having a pair of recesses thereon
adapted for mating with an instrument, wherein the opposing bosses
mate with the pair of recesses.
11. The method of claim 10 wherein the inner member comprises an
outer wall and an end plate having a substantially spherical pocket
thereon adapted for mating with the instrument, and wherein the
spherical distal end of the lever pivotally mates with the
spherical pocket.
12. The method of claim 1 wherein the cage has a closed
configuration in step a), and further comprising the step of: d)
expanding the cage to an expanded configuration.
Description
CONTINUING DATA
[0001] This divisional application claims priority from co-pending
U.S. Ser. No. 12/432,117, entitled "Minimally Invasive Corpectomy
Cage and Instrument", filed Apr. 29, 2009, by Frasier., (Attorney
Docket No. DEP6219USNP), the specification of which is incorporated
by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] A spinal corpectomy procedure seeks to remove a diseased
vertebral body from the patient, and is commonly performed through
an anterior approach using a large, open incision and general
retractors. Increasingly, however, surgeons are utilizing smaller
access portals for all types of surgeries, including spinal
corpectomies. They also are more often using a posterior approach
when the corpectomy involves the thoracic spine. However, this
approach provides a more limited access to the spine, and often
requires the surgeon to take a nerve root in order to use existing
corpectomy cages and instruments. Surgeons who strive to keep their
access windows small often resort to manipulating the corpectomy
cage into position using sutures and small instruments, by first
inserting the cage orthogonal to the axis of the spinal column,
then and rotating it into place so that the endplates of the cage
face the opposing vertebral bodies. A corpectomy implant and
instrument designed for use through a small incision or port would
make this cage placement easier and faster for the surgeon, and
safer for the patient.
[0003] US Patent Publication No. 20080114467 (Capote) discloses an
expandable medical implant for supporting bone structures. The
implant may include an outer member and an inner member receivable
in the outer member. One of the outer and inner members includes a
tapered surface and the other of the outer and inner members
includes a scalloped surface. The implant may also include a
locking element disposed between the tapered surface and the
scalloped surface. The tapered surface may be movable relative to
the locking element to transversely shift the locking element into
engagement with the scalloped surface to inhibit a decrease in the
overall implant height.
[0004] US Patent Publication No. 20080167720 (Melkent) discloses an
expandable vertebral replacement device and method of using the
same that allows surgeons to support two adjacent vertebrae after
an intermediate vertebra or a portion of an intermediate vertebra
has been removed for the spine. The expandable vertebral
replacement device includes a first replacement body, a second
replacement body and a collar. The second replacement body includes
a projecting portion that is telescopically received within an
axial passage defined by the first replacement body. The collar is
used to force the collet of the first replacement body into
clamping engagement with the projecting portion of the second
replacement body to lock the expandable vertebral replacement
device at a select height.
[0005] PCT Patent Publication No. WO2006116052 (Rhoda) discloses an
expandable prosthetic implant device for engagement between
vertebrae generally comprising an inner member, outer member, and
gear member positioned coaxial with respect to each other such that
the inner and outer members are moveable relative to each other
along an axis. The gear member is axially fixed to the outer member
and freely rotatable with respect to the outer member and the gear
member threadedly engages a threaded portion of the inner member to
translate inner member along the axis. The implant is configured to
engage the vertebrae in a predetermined alignment and the gear
member includes gear teeth exposed to the exterior and configured
to be accessible by a tool member at a plurality of angular
positions around the perimeter of the implant device.
[0006] PCT Patent Publication No. WO2008065450 (Parry) discloses an
implant for repairing a damaged body structure that comprises or is
associated with bone parts. In one aspect a spinal implant includes
an inferior member having an inferior end surface for engaging a
superior face of an inferior vertebral body and a longitudinal
portion; a superior member having a superior end surface for
engaging an opposing inferior surface of a second vertebral body,
and a portion adapted to cooperate with the longitudinal portion of
the inferior member such that the superior member is moveable
relative to the inferior member by sliding in the longitudinal
direction; and fixating means for securing the superior member to
the inferior member. Also described are instruments and methods
used in the repair of such damaged body structures.
SUMMARY OF THE INVENTION
[0007] The present invention is directed to implants, instruments
and methods of delivering a corpectomy implant into a spinal defect
space and then rotating the corpectomy implant in the defect space
without disconnecting it from its delivery instruments. In
preferred embodiments, the instruments of the present invention are
designed to work through a minimally invasive port. This minimally
invasive approach thereby eliminates the need for the surgeon to
take the local nerve root during the corpectomy procedure.
[0008] The present invention is further advantageous in that it
also eliminates the need for a parallel expansion insertion device
(which would require an open surgery), while maintaining a
sufficient external expansion mechanism and a large graft volume
inside the implant.
[0009] Preferred embodiments of the present invention feature an
expandable corpectomy cage and an insertion instrument designed to
both rotate and expand the cage.
[0010] In preferred embodiments, the expandable cage comprises an
instrument attachment features, these feature including i) mating
holes on the sides of the outer sleeve, and ii) a ball-shaped
pocket on the endplate of the inner sleeve.
[0011] In preferred embodiments, the insertion instrument features:
[0012] a) a tuning-fork shaped holder, which attaches to the mating
holes on the implant's outer sleeve using small bosses which mate
with the holes under the spring tension of the fork, and [0013] b)
a lever with a spherical end that mates with the ball-shaped pocket
in the inner sleeve endplate.
[0014] In other embodiments, the mating provided by the spring
tension of the fork can be accomplished with a pivot and lock.
[0015] Therefore, in accordance with the present invention, there
is provided a spacer for insertion between two vertebrae, the
spacer having a variable axial height and comprising: [0016] a) an
outer member comprising an inner wall and an outer wall having a
pair of attachment features thereon adapted for mating with an
insertion instrument, [0017] b) an inner member comprising an outer
wall and an end plate having a pocket having a substantially curved
bottom thereon adapted for mating with the instrument,
[0018] wherein the outer wall of the inner member is received
within the inner wall of the outer member and is axially adjustable
relative thereto in an axial direction thereof for adjusting the
variable axial height of the spacer.
Also in accordance with the present invention, there is provided a
spacer for insertion between two vertebrae by an insertion
instrument, the spacer having a variable axial height and
comprising: [0019] a) an outer member comprising an inner wall and
an outer wall having a pocket having a substantially curved bottom
thereon adapted for mating with a first portion of the instrument,
[0020] b) an inner member comprising an outer wall and an end plate
having a pair of attachment features thereon adapted for mating
with a second portion of the instrument,
[0021] wherein the outer wall of the inner member is received
within the inner wall of the outer member and is axially adjustable
relative thereto in an axial direction thereof for adjusting the
variable axial height of the spacer.
Also in accordance with the present invention, there is provided an
assembly for inserting a spacer between two vertebrae, the assembly
comprising: [0022] i) the spacer having a variable axial height and
comprising: [0023] a) an outer member comprises an inner wall and
an outer wall having a pair of attachment features thereon adapted
for mating with an instrument, [0024] b) an inner member comprises
an outer wall and an end plate having a a pocket having a
substantially curved bottom thereon adapted for mating with the
instrument, wherein the outer wall of the inner member is guided
within the inner wall of the outer member to be adjustable relative
thereto in an axial direction thereof for adjusting an overall
height, and [0025] ii) an insertion instrument comprising: [0026]
a) a fork comprising a proximal shaft comprising a handle, an
intermediate crossbar, and a distal portion comprising a pair of
extensions, the extensions having a pair of opposing bosses, [0027]
b) a lever having a proximal shaft comprising a handle, an
intermediate portion and a substantially curved distal end, wherein
the intermediate portion of the lever pivots upon the crossbar,
wherein the opposing bosses mate with the pair of attachment
features, and
[0028] wherein the substantially curved distal end of the lever
pivotally mates with the substantially curved bottom of the
pocket.
[0029] Also in accordance with the present invention, there is
provided a method of inserting an expandable spinal corpectomy cage
into a defect space between a pair of vertebral bodies, the cage
comprising i) an outer member having a first endplate and opposing
attachment features defining a rotation axis, and ii) an inner
member having a second endplate, wherein the inner member is
received within the outer member and is axially adjustable relative
thereto in an axial direction thereof for adjusting the variable
axial height of the cage, the method comprising the steps of:
[0030] a) attaching the attachment features of the expandable cage
to an insertion instrument, [0031] b) inserting the expandable cage
into the defect space in an orientation in which the axis of the
cage is substantially orthogonal to an axis of the spine, and
[0032] c) manipulating the insertion instrument to rotate the
expandable cage about the rotation axis so that the axis of the
cage is substantially parallel to the axis of the spine.
DESCRIPTION OF THE FIGURES
[0033] FIG. 1 discloses an expandable cage of the present invention
comprising instrument attachment features, including mating holes
on the sides of the outer sleeve, and a ball-shaped pocket on the
endplate of the inner sleeve.
[0034] FIG. 2 discloses a first instrument component of the present
invention, namely, a tuning-fork shaped holder, which attaches to
the mating holes on the implant's outer sleeve using small bosses
which mate with the holes under the spring tension of the fork.
[0035] FIG. 3 discloses a second instrument component of the
present invention, namely, a lever with a spherical end that mates
with the ball-shaped pocket in the inner sleeve endplate.
[0036] FIG. 4a discloses the cage of the present invention attached
to the instrument of the present invention.
[0037] FIGS. 4b and 4c disclose insertion of the cage into a defect
space in a minimally invasive orientation.
[0038] FIG. 4d discloses rotating the cage 90 ninety degrees.
[0039] FIG. 4e discloses expansion of the rotated cage.
[0040] FIG. 4f discloses rotation of the instrument to allow access
to the set screw.
[0041] FIGS. 5a-5j disclose a series of steps performed by the
surgeon in order to insert and expand the cage of the present
invention.
[0042] FIGS. 6a and 6b disclose front and back views of a cage of
the present invention.
[0043] FIG. 6c discloses a cage of the present invention having
windows in both annuluses.
[0044] FIG. 7a discloses a cage of the present invention in which
the teeth of the pressure plate mate with the notches on the inner
annulus.
[0045] FIG. 7b discloses details of the engagement mechanism of the
present invention.
[0046] FIG. 8a discloses a perspective view of the engagement
member of the present invention.
[0047] FIG. 8b discloses a cross-section of the engagement
mechanism of the present invention having a pressure plate.
DETAILED DESCRIPTION OF THE INVENTION
[0048] Now referring to FIG. 1, there is provided a spacer 150 for
insertion between two vertebrae, the spacer having a variable axial
height and comprising: [0049] a) an outer member 101 comprising an
inner wall 103 and an outer wall 105 having a pair of recesses 107
thereon adapted for mating with an instrument, [0050] b) an inner
member 111 comprising an outer wall 113 and an end plate 115 having
a substantially spherical pocket 117 thereon adapted for mating
with the instrument, wherein the outer wall of the inner member is
received within the inner wall of the outer member and is axially
adjustable relative thereto in an axial direction thereof for
adjusting the variable axial height of the spacer.
[0051] Now referring to FIG. 2, there is provided a first component
of the delivery instrument, comprising a fork 122 comprising a
proximal shaft 123 comprising a handle 125, an intermediate
crossbar 127 (fulcrum), and a distal portion 129 comprising a pair
of extensions 131, each extension having a pair of opposing bosses
133.
[0052] Now referring to FIG. 3, there is provided a second
component of the delivery instrument, comprising a lever 141 having
a proximal shaft 143 comprising a handle 145, an intermediate
portion 147 and a substantially spherical distal end 149.
[0053] In preferred embodiments, the cage of the present invention
is inserted into the defect space in the following manner:
[0054] First, the surgeon accesses the spinal level of interest by
removing the target vertebral body through a small incision or
portal.
[0055] Next, and now referring to FIG. 4a, an appropriately-sized
cage 150 is selected and attached to the fork 122 by snapping the
fork's bosses 133 over the recesses 7 on the outer member of the
cage. Next, the lever 141 is attached to the inner sleeve pocket
117 by sliding its spherical end 149 into the pocket from under the
inferior side of the superior endplate. Next, the cage is
collapsed, and the handles of the fork 125 and lever 145 are
oriented to be parallel to the main axis of the cage.
[0056] Next, and now referring to FIGS. 4b and 4c, the surgeon
holds the handles 125,145 together, and inserts the cage 150
through an access portal (not shown).
[0057] Now referring to FIG. 4d, once the cage 150 is in the defect
at the desired location (but not orientation), the surgeon
manipulates the two handles 125,145 to flip the cage ninety
degrees, thereby making it parallel to the axis of the spine.
[0058] Now referring to FIG. 4e, expansion of the cage 150 is then
initiated by placing the intermediate portion 147 of the lever
against the horizontal crossbar 127 of the fork, and squeezing the
handles together.
[0059] Now referring to FIG. 4f, the fork 122 and lever 141 can be
rotated slightly while still under tension, allowing access to a
set screw on the cage with a straight, thin driver. Once the set
screw is locked, the fork is removed by pulling it straight up to
overcome the spring tension in the fork. The lever is removed by
sliding it out from under the superior endplate.
[0060] A more detailed presentation of the procedure for inserting
the present invention is provided in FIGS. 5a-5j and is presented
below:
[0061] Now referring to FIG. 5a, the fork extensions 131 are
attached to the implant, with the extension bosses 133 resting in
the recesses 107 on the wall 105 of the outer member of the
implant. This attachment configuration allows rotation of the
implant about the bosses. The spring-loaded nature of the
extensions of the fork allow them to snap over the implant
body.
[0062] Now referring to FIG. 5b, the spherical distal end 149 of
the lever is mounted in the spherical pocket 117 located on the
implant. This spherical distal end is mounted in the pocket through
an underside 199 of the endplate portion 115 of the inner member.
Slot 153 provided above the spherical pocket on the endplate allows
the lever to rotate into an insertion position
[0063] Now referring to FIG. 5c, the fork 122 and the lever 141 are
held together in-line with the longitudinal axis of the implant as
the implant 150 is inserted between the vertebrae.
[0064] Now referring to FIG. 5d, the fork 122 is held steady while
the lever 141 is manipulated to begin rotation of the implant 150.
Now referring to FIG. 5e, rotation of the implant 150 about the
bosses 133 continues by continued manipulation of the lever
141.
[0065] Now referring to FIG. 5f, rotation of the implant 150 to its
final orientation is accomplished by pushing the lever 141 down
while holding onto the fork 122.
[0066] Now referring to FIG. 5g, once the implant 150 has been
rotated to its final orientation and the implant endplates seat
against the endplates of the vertebral bodies, the proximal shaft
143 of the lever is swung upwards to more substantially align with
the proximal shaft 123 of the fork.
[0067] Now referring to FIGS. 5h and 5i, to begin expansion of the
implant, the shafts 143,123 of the lever and fork are squeezed
together. In this configuration, the lever mates with a slot 155 on
the cross-bar of the fork so that the crossbar 127 behaves as a
fulcrum in order to expand the implant.
[0068] Now referring to FIG. 5j, to complete expansion of the
implant 150, the shaft 143 of the lever is typically pushed past
the shaft 123 of the fork, depending upon the amount of expansion
needed.
[0069] Generally, the attachment features of the cage can be any
conventional feature that is used to attach an implant to an
insertion instrument. Preferably, the attachment feature is a
recess having a shape corresponding to the bosses of the insertion
instrument. Also preferably, the cage has a pair of attachment
features that are located on diametrically opposite sides of a cage
wall. Although the attachment features are shown in the FIGS. as
recesses, in other embodiments, the attachment features can also be
projections (in which case, the insertion instrument possesses
corresponding recesses).
[0070] Generally, the pocket has a curved bottom that facilitates
the pivoting of the cage. Preferably, the curved surface has a
circular cross section in the axial direction. More preferably, the
pocket has a substantially spherical shape. In other embodiments,
the pocket has a cylindrical shape. In general, the distal end of
the lever component possesses a feature that matingly corresponds
to the pocket shape on the cage. For example, when the cage's
pocket is substantially spherical, the lever's distal end is
likewise substantially spherical.
[0071] Now referring to FIGS. 6a-6c there is provided a spacer for
insertion between two vertebrae, the spacer having a variable axial
height and comprising a sleeve-shaped first member 1 and a second
member 2 guided within the first member to be slidable relative
thereto in an axial direction thereof for adjusting an overall
height,
[0072] wherein the second member comprises an outer wall 3 and
ratchet notches 5 provided at its outer wall facing the first
member and extending in the axial direction, and
[0073] wherein the first member comprises a wall 7 having an
engagement member 9, which cooperates with the ratchet notches for
adjusting the overall height of the spacer,
[0074] wherein the first member has a window 10 therein for
inserting graft material therethrough, and
[0075] wherein the engagement member 9 comprises i) a set screw 11
and ii) a pressure plate 13 having an outer face 15 contacting the
set screw and an inner face 17 having teeth 19 adapted to mate with
the ratchet notches of the second member.
[0076] The first member generally has a tubular shape comprising a
first annulus 21. The outer end of the first member should be
adapted to seat upon a lower vertebral endplate, and so a
substantially flat endplate 25 is generally attached to the outer
end 27 of the first annulus. This endplate generally has a hole in
its center and extends outwardly substantially radially from the
outer end of the annulus. The outer face 28 of the endplate should
be adapted to grip the lower vertebral endplate and so is generally
provided with roughened features 29. These roughened features may
be a plurality of uniformly distributed, pointed teeth 31 that bite
into the adjacent endplate. In other embodiments, the teeth may be
non-uniformly distributed. For further insuring that the endplate
will be stably seated into the vertebral endplate, the outer face
of the endplate may also have a few long spikes 33 extending
therefrom. In some embodiments, the endplate has an overall convex
shape in order to suitably conform to the overall concave shape of
the natural vertebral endplate in which it seats. In some
embodiments (as in FIG. 6), the endplate has a wedge cross-section
in order to conform to the lordosis adopted by the natural spine in
the region of the implant. Typically, the wedge is designed to
provided a lordotic angle of between about 0 and about 24 degrees,
more typically between about 6 and about 12 degrees. The wedge may
also be designed to provided a kyphotic angle of between about 0
and about -12 degrees,
[0077] In general, the outer dimensions of the endplates of the
present invention are between about 16 mm and about 30 mm (e.g.,
16.times.20; 20.times.23 and 24.times.30).
[0078] The annular portion of the first member also comprises a
plurality of uniformly distributed, transverse, through-holes 35.
These throughholes are generally about 2-8 mm in diameter, and
provide a means for bone growth therethrough. The holes are
preferably of diamond shape, although other shapes such as
triangles may be used. When in a diamond shape, suitable sizes
include 2.5 mm.times.3.5 mm shapes to 5 mm.times.7 mm shapes. In
the particular FIGS. 6a and 6b, the throughholes have a diamond
shape. The diamond shape allows the annulus material to make a mesh
pattern in the wall that has structural advantages. However, any
conventional shape may be used for the through-hole pattern. In
some embodiments, the plurality of throughholes occupy only the
distal portion 37 of the annulus. In such an embodiment, graft
windows may be placed both on the proximal 39 and lateral 41
portions of the annulus. This has the advantage of allowing the
surgeon to place bone graft into the cage from a variety of angles.
In some embodiments, the plurality of throughholes occupy not only
the distal portion of the first annulus, but also the lateral
portions as well. In such an embodiment, graft windows may be
placed only through the proximal portion of the annulus, but the
cage has the structural advantage of extra strength.
[0079] The first member generally has at least one graft window 10
therein. The graft window functions both as a path through which
the surgeon can place bone graft into the cage, but also as a means
for bone growth therethrough. In other embodiments, the first
member has a plurality of graft windows therein. When a face of the
annulus has been selected for graft windows, in preferred
embodiments, two graft windows 43 are placed one on top of the
other, being separated by a bar 45. This bar enhances the strength
of the cage. In the particular cage shown in FIG. 6, there are two
graft windows on the proximal face of the annulus, two graft
windows on the left lateral face of the annulus and two graft
windows on the right lateral face of the annulus. This
configuration represents a balance between providing surgeon
flexibility (through the inclusion of multiple faces with graft
windows) and cage strength (through the use of a lateral bar
between windows on any face). Each window typically has a diameter
of between about 5 mm and about 20 mm. Typical windows measure 5.5
mm.times.5.6 mm to 12 mm.times.15.75 mm to 17.5 mm.times.12 mm.
[0080] The first member may preferably include a reinforcing collar
47 surrounding the inner (upper) end portion 48 of the first
annulus. The function of the reinforcing collar is to strengthen
the first member and reduce deflection when the screw is tightened.
The reinforcing collar also generally has a threaded screw hole
extending radially therethrough. This threaded screw hole is
adapted for threadable passage of a threaded locking set screw
therethrough.
[0081] Now referring to FIG. 7a, the first member comprises a
collar 47 having an engagement member 9 therein, and the engagement
member cooperates with the ratchet notches of the second member for
adjusting a desired overall height of the spacer.
[0082] Now referring to FIG. 7b, there is provided a more detailed
understanding of the engagement member. The engagement member 9
comprises i) a set screw 11 and ii) a pressure plate 13 having an
outer face 15 contacting the set screw and an inner face 17 having
teeth 19 adapted to mate with the ratchet notches of the second
member.
[0083] In some embodiments, as in FIG. 7b, a cylindrical outer
surface 20 of the set screw is threaded to allow its advance toward
the second member. In some embodiments, as in FIGS. 8a and 8b, the
set screw is tubular with internal axial recesses 22 therein
extending along its axis. These axial recesses mate with a
screwdriver, thus allowing the screw to be rotated and thereby
advanced towards the second member.
[0084] The set screw further has a neck and head extension 49
extending from its distal end 50, wherein the extension is shaped
so as to both provide engagement with a corresponding recess 51 of
the pressure plate and allow its rotation during that
engagement.
[0085] Now referring to FIGS. 8a and 8b, the pressure plate 13 has
an outer face 15 contacting the set screw and an inner face 17
having teeth 19 adapted to mate with the ratchet notches of the
second member. The outer face has a neck and head recess 51 therein
that corresponds with the head and neck extension of the set screw
so as to both provide engagement with a corresponding extension of
the set screw and allow rotation of the set screw during that
engagement. The pressure plate is seated on the inside face of the
collar.
[0086] The inner face of the pressure plate has at least two
elongated teeth 19 thereon forming at least one notch therebetween.
The tips of the teeth are preferably spaced apart a distance of
between about 1 mm and 2 mm, generally about 1.5 mm. The spacing
can be larger or smaller than these values, with smaller being
preferable.
[0087] Now referring to FIG. 6b, the distal 37 portion of the first
member also has an assembly pin 53 extending radially inward from
the collar. This assembly pin slidably mates with a corresponding
assembly groove 54 of the second member in order to maintain the
second member in a slidable orientation within the first member,
and to retain the first member to the second member.
[0088] Still referring to FIG. 6b, the second member generally has
a tubular shape comprising a second annulus 55. The outer diameter
of the second annulus should be slightly smaller than the inner
diameter of the first annulus of the first member, in order to
provide slidable reception of the second annulus within the first
member.
[0089] The outer end of the second member should be adapted to seat
upon an upper vertebral endplate, and so a substantially flat
endplate 57 is generally attached to the outer end 59 of the second
annulus 55. This endplate generally has a hole in its center and
extends outward substantially radially from the upper end of the
annulus. The outer face of the endplate should be adapted to grip
the upper vertebral endplate and so is generally provided with
roughened features 29. These roughened features may be a plurality
of uniformly (or non-uniformly) distributed, pointed teeth 31 that
bite into the adjacent endplate. For further insuring that the
endplate will be stably seated into the vertebral endplate, the
outer face of the endplate may also have a few long spikes 33
extending therefrom. In some embodiments, the endplate has an
overall convex shape in order to suitably conform to the overall
concave shape of the natural vertebral endplate in which it
seats.
[0090] The annular portion of the second member also comprises a
plurality of uniformly distributed, transverse, through-holes 35.
These throughholes are generally of the throughhole size discussed
above, and provide a means for bone growth therethrough. In this
particular FIG. 6a, the throughholes have a diamond shape. The
diamond shape allows the second annulus material to make a mesh
pattern that has structural advantages. However, any conventional
shape may be used for the through-hole pattern. In some
embodiments, the plurality of throughholes occupy each of the
lateral faces of the posterior portion of the second annulus.
[0091] The second member may preferably include a reinforcing
collar 61 surrounding the outer (upper) end portion 59 of the
second annulus. The function of this reinforcing collar is to allow
for instrument attachment. The reinforcing collar also generally
has a pluraliuty of through-holes 63 extending radially
therethrough. These throughholes function as areas for instrument
attachment, and as areas for bone growth and vascularization.
[0092] The proximal portion 65 of the second annulus has a
plurality of elongated teeth 67 thereon forming at least one notch
69 therebetween. These teeth and notches form a row extending up
the outside of the annulus. Typically, the annulus of the second
member has at least ten elongated notches thereon. These notches
are formed to compliment the teeth of the pressure plate. The
apices of the notches on the second member are generally spaced
apart a distance of between about 1 mm and 2 mm, generally about
1.5 mm. The spacing can be larger or smaller than these values,
with smaller being preferable.
[0093] The distal 70 portion of the second annulus of the second
member also has an assembly groove 54 extending inwardly and
axially along the outside 68 of the second annulus. This assembly
groove mates with the corresponding assembly pin of the first
member in order to maintain the second member in a slidable
orientation within the first member.
[0094] Once the overall height of the cage has been determined by
the surgeon and the relative disposition of the first and second
members set accordingly, the set screw is then rotated by the
surgeon using a screwdriver. The set screw acts to advance the
pressure plate so that the teeth on the pressure plate contact the
ratchet notches of the second member, thereby locking the desired
overall height of the cage.
[0095] Typically, the cages of the present invention are designed
to occupy either one, two or three levels of a thoracolumbar
corpectomy. In some embodiments having either 16 mm or 20 mm
endplate dimensions, the height of the cage can be between 22 mm
and 72 mm. In some embodiments having 24 mm endplate dimensions,
the height of the cage can be between 22 mm and 110 mm. In general,
the cage is designed to expand its height in an increment of
between about 8.5 mm to about 25 mm. Cages can be designed to
overlap in height ranges with their adjacent sizes. For example a
first cage can range in height from 25 to 33.5 mm, while a second
cage can range in height from 28.5 mm to 38.5 mm in height.
* * * * *