U.S. patent application number 11/833536 was filed with the patent office on 2008-01-24 for anterior cervical plate.
This patent application is currently assigned to ZIMMER SPINE, INC.. Invention is credited to Thomas Ross.
Application Number | 20080021470 11/833536 |
Document ID | / |
Family ID | 34393537 |
Filed Date | 2008-01-24 |
United States Patent
Application |
20080021470 |
Kind Code |
A1 |
Ross; Thomas |
January 24, 2008 |
ANTERIOR CERVICAL PLATE
Abstract
An anterior cervical plate has a lower surface adapted to engage
the cervical spine and a top surface. At least one location along
the plate there are two transversely aligned bone screw holes. A
locking element is pivotally mounted between these two bone screw
holes for movement between an open position which uncovers the two
bone screw holes and a locking position wherein the locking element
at least partially covers each of the two bone screw holes. A
positive positioning structure positively positions the locking
element in the locking position.
Inventors: |
Ross; Thomas; (Austin,
TX) |
Correspondence
Address: |
WOOD, HERRON & EVANS (ZIMMER SPINE)
2700 CAREW TOWER
441 VINE STREET
CINCINNATI
OH
45202
US
|
Assignee: |
ZIMMER SPINE, INC.
7375 Bush Lake Road
Minneapolis
MN
55439-2029
|
Family ID: |
34393537 |
Appl. No.: |
11/833536 |
Filed: |
August 3, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10676064 |
Oct 2, 2003 |
7306605 |
|
|
11833536 |
Aug 3, 2007 |
|
|
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Current U.S.
Class: |
606/279 |
Current CPC
Class: |
A61B 17/7059 20130101;
A61B 17/8042 20130101; A61B 17/8033 20130101 |
Class at
Publication: |
606/061 |
International
Class: |
A61B 17/70 20060101
A61B017/70 |
Claims
1-20. (canceled)
21. An anterior cervical plate for engaging at least two vertebrae
along the anterior cervical spine, comprising: a lower surface
adapted to engage the anterior of at least two cervical vertebrae
and an opposite upper surface; at least one receiving area formed
in the upper surface and including two transversely aligned screw
holes, and a locking element pivotally mounted on the receiving
area and being movable to a first position in which the locking
element completely uncovers the screw holes and a second position
in which portions of the elongated locking element extend over a
portion of each screw hole to prevent the bone screws located
therein from backing out; and at least one projection on the
receiving area and at least one matching recess on the bottom of
the locking element, wherein the projection will snap into place in
the recess when the locking element is in said second position.
22. The cervical plate of claim 21, wherein the locking element has
a pair of recessed ramps on the bottom thereof to ride up over the
projections and permit the projections to snap into place in the
recesses.
23. The cervical plate of claim 21 further comprising: a tool
receiving opening in the locking element for receiving a tool to
turn the locking element between the first and second
positions.
24. The cervical plate of claim 21, wherein the receiving area is
recessed relative to a remainder of the upper surface and extends
substantially the width of the upper surface.
25. A spinal fixation assembly comprising: an anterior cervical
plate for engaging at least two vertebrae along the anterior
cervical spine; a lower surface of the plate adapted to engage the
anterior of at least two cervical vertebrae and an opposite upper
surface of the plate; at least two transversely aligned screw holes
extending between the upper and lower surfaces; at least two bone
screws each having a head and extending through and seated in one
of the screw holes; and a locking element pivotally coupled to the
upper surface of the plate and being movable to a first position in
which the locking element completely uncovers the screw holes and a
second position in which portions of the locking element extend
over a portion of each screw hole to prevent the bone screws
located therein from backing out; wherein the locking element is
spaced from the heads of bone screws when the locking element is in
the second position and the heads are seated in the screw
holes.
26. The assembly of claim 25 further comprising: a positive
positioning structure at an interface between the plate and the
locking element, which holds the locking element in the second
position.
27. The assembly of claim 25 further comprising: a pivot hole in
one of the plate and the locking element; and a post extending
through the pivot hole to pivotally couple the plate and locking
element together.
28. An anterior cervical plate for engaging at least two vertebrae
along the anterior cervical spine, comprising: a plate having a
lower surface adapted to engage the anterior of at least two
cervical vertebrae and an opposite upper surface; at least one pair
of spaced apart screw holes through the plate; a locking element
pivotally mounted between the screw holes and movable between a
first position in which the locking element completely uncovers the
screw holes and a second position in which the locking element
extends over a portion of each screw hole to prevent the bone
screws located therein from backing out; and a positive positioning
structure at an interface between the plate and the locking element
that holds the locking element in the second position.
29. The cervical plate of claim 28, wherein the positive
positioning structure further comprises: a projection on one of the
plate and the locking element; and a matching recess on the other
of the plate and the locking element, the projection and the
matching recess being positioned so as to hold the locking element
in said second position.
30. The cervical plate of claim 29, wherein the projection is on
the plate and the matching recess is on the bottom of the locking
element.
31. The cervical plate of claim 30, wherein the bottom of the
locking element has a recessed ramp to ride up over the projection
to permit the projection to snap into the matching recess when the
locking element is in the second position.
32. The cervical plate of claim 31 further comprising: a pair of
projections on the plate and a pair of matching recesses on the
bottom of the locking element.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to an anterior cervical plate, and in
particular it relates to such a plate with a new and improved
locking element.
[0002] It is known to provide an anterior cervical plate for
attachment to the anterior of two or more cervical vertebrae for
the purpose of immobilizing, stabilizing and/or aligning those
vertebrae. The plates can be used for a variety of conditions
including for example providing added strength and rigidity after
fusion of adjacent vertebrae, securing vertebrae together where an
intervening vertebrae has been removed and replaced, correcting
spinal deformities, and correcting instability caused by trauma,
tumors, advanced degenerative discs, infection or congenital or
acquired deformities.
[0003] Cervical plates of the present type are generally elongated
so as to span the distance between two, three, four or more
vertebrae, as required in a given situation. The plates are
generally curved transversely so as to fit the curvature of the
vertebrae to which they are attached. Additionally, plates of this
type are generally concave longitudinally thereof to match the
curvature of the cervical spine. Cervical plates of this type are
provided with holes for bone screws. Holes are drilled into the
adjacent vertebrae by instruments which are known in the art, after
which the cervical plate is attached by bone screws which pass
through the holes in the cervical plate for securing the plate to
the adjacent vertebrae.
[0004] Many cervical plates of the present type are known, each
having various arrangements for securing the bone screws. Such
arrangements are shown in prior U.S. Pat. Nos. 5,364,399;
5,549,612; 6,193,721; 6,224,602; 6,235,034; 6,383,186; and
6,454,771. Notwithstanding the development of the prior art to
date, a need exists for improvements in arrangements for securing
the bone screws in place after the bone screws have secured the
cervical plate onto the adjacent vertebrae.
[0005] It is a purpose of the present invention to provide an
anterior cervical plate of the type for attachment to cervical
vertebrae for stabilizing, immobilizing and/or aligning those
vertebrae, which plate has a new and improved arrangement for
securing the bone screws in place after the cervical plate has been
attached to the cervical vertebrae.
[0006] In accordance with the present invention, the cervical plate
includes a number of bone screw holes for attaching the cervical
plate to the vertebrae. Specifically, in accordance with the
present invention there is provided at least one pair of adjacent
bone screw holes, preferably transversely aligned, wherein the
cervical plate has a locking element mounted between the adjacent
bone screw holes and movable between a first, open position where
it uncovers the two bone screw holes to permit insertion there
through of the bone screws and a second, locking position whereat
the locking element overlies at least a portion of each of the two
bone screw holes, to lock those bone screws in place. The locking
element of the present invention is intended essentially to prevent
the screws from backing out, i.e., it is not intended to be a force
exerting member to exert a downward force on tightened bone
screws.
[0007] In accordance with one arrangement of the present invention,
an elongated locking element is pivotally mounted on a surface area
of the cervical plate between two adjacent bone screw holes. This
locking element is movable to a first position whereat it
completely uncovers the two adjacent holes so as to permit the
insertion of bone screws there through. The locking element is then
arranged to be pivoted to partially cover the two bone screw holes
with the bone screws secured in place there beneath.
[0008] The present invention provides various arrangements for
effecting the pivotal connection between the plate and the locking
element. In one arrangement the plate may have a raised boss onto
which is pivotally mounted a locking element having an opening
there through. In another arrangement the plate itself can have an
opening and the locking element can have a raised boss on the lower
side thereof which projects through the through hole in the plate.
In another arrangement, the locking element can have a central
opening and the plate can have a through hole, both of which
cooperate with a third element, a post which passes through the
opening and the through hole.
[0009] Another feature of the present invention is the provision of
a structure to positively position the locking element in its
locking position. For this purpose, a protrusion on either the
bottom of the locking element or the surface of the plate can be
arranged to be snap fitted into a recess or indentation in the
other of the cervical plate or locking element. Preferably, the
protrusions will be in the form of bumps on the surface of the
plate and the indentions will be in the form of recesses on the
bottom of the locking element, wherein the bumps and recesses are
aligned to positively position the locking element when it is in
its locking position. The bottom of the locking element may include
recessed ramps which ride over the bumps as the locking element is
initially turned from its open position to its locking position.
The bumps would then ride up the recessed ramps and then snap into
place in the recesses when the locking element has reached its
locking position.
[0010] Turning of the locking element between its open and locking
positions can be accomplished by using a tool, and for this purpose
the locking elements are provided with a pair of openings, offset
relative to the pivot axis, to receive such a tool.
[0011] The present invention is applicable to cervical plates of a
virtually limitless number of configurations. Cervical plates are
generally referred to by the number of levels that they overlie,
wherein the word "level" refers to the number of intervening
intervertebral spaces that are spanned. Thus, for example, a three
level cervical plate would span the four vertebrae beyond and
between the three intervertebral spaces. The plate can be connected
at some places by a single central bone screw through a single
central bone screw hole instead of by the two adjacent bone screw
holes which include the locking element of the present invention.
In virtually all configurations, an opening will be provided
between adjacent vertebrae for viewing the intervening
intervertebral space.
[0012] In any configuration the cervical plate would almost always
be attached to the upper and lower vertebrae. Connections of the
cervical plate between the upper and lower vertebrae would depend
on the level of the cervical plate and the nature of the surgery
performed on the spine adjacent to the cervical plate. For example,
if the surgery involved replacing only the discs and leaving the
vertebrae intact in a three or four level cervical plate, then
screws might be attached to the intermediate vertebrae. However, a
long plate such as a three level or four level plate would more
likely be used after a corpectomy, wherein the intervening
vertebrae and discs would have been removed and replaced with a
bone plug/graft or a mesh/cage implant. In these cases, it is
unlikely that screws would be attached between the upper and lower
vertebrae, although it might be desirable to place one or two
screws into a bone plug/graft.
[0013] 13 Thus, it is an object of the present invention to provide
a new and improved anterior cervical plate.
[0014] It is another object of the present invention to provide a
new and improved locking element in combination with a cervical
plate for locking a pair of bone screws in adjacent bone screw
openings of the plate.
[0015] These and other objects of the present invention will be
apparent from the detailed description to follow, together with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] There follows a detailed description of preferred
embodiments of the present invention which are to be read together
with the drawings wherein:
[0017] FIG. 1 is a top plan view of an anterior cervical plate in
accordance with the present invention;
[0018] FIG. 2 is a bottom plan view of FIG. 1;
[0019] FIG. 3 is a top plan view of the locking element of FIG.
1;
[0020] FIG. 4 is a bottom plan view of the locking element of FIG.
1;
[0021] FIG. 5 is a cross sectional view taken along line 5-5 of
FIG. 1;
[0022] FIG. 6 is a cross sectional view taken along line 6-6 of
FIG. 1;
[0023] FIG. 7 is a cross sectional view taken along line 7-7 of
FIG. 1;
[0024] FIGS. 8, 9, 10 and 11 show four different shaped anterior
cervical plates, all of which are designed to employ the features
of the present invention;
[0025] FIG. 12 is a top plan view of an anterior cervical plate
showing another embodiment of the present invention;
[0026] FIG. 13 is a bottom plan view of FIG. 12;
[0027] FIG. 14 is a top plan view of the locking element of FIG.
12;
[0028] FIG. 15 is a bottom plan view of the locking element of FIG.
12;
[0029] FIG. 16 is a bottom perspective view of the locking element
of FIG. 12;
[0030] FIG. 17 is a view taken along line 18-18 of FIG. 12, but
showing certain elements in a partially assembled state;
[0031] FIG. 18 is a cross sectional view taken along line 18-18 of
FIG. 12;
[0032] FIG. 19 is an exploded view which is taken along a plane
represented by plane 18-18 of FIG. 12 but showing a modification of
the present invention;
[0033] FIG. 20 illustrates the embodiment of FIG. 19, but during a
subsequent state of assembly;
[0034] FIG. 21 shows the modification of FIGS. 19 and 20 in the
fully assembled state; and
[0035] FIG. 22 is a schematic view showing an anterior cervical
plate which would in the final form include the features of the
present invention, but showing the plate in relation to vertebrae
and discs of the cervical spine.
DETAILED DESCRIPTION
[0036] Referring now to the figures, like elements are represented
by like numerals throughout the several views.
[0037] An anterior cervical plate of the type with which the
present invention is concerned attaches to the anterior surface of
a plurality of cervical vertebrae to perform a number of different
functions including stabilizing, aligning and immobilizing two or
more adjacent vertebrae. These will be described generally with
respect to the diagrammatic view of FIG. 22. This figure shows four
adjacent vertebrae V1, V2, V3 and V4 separated by intervertebral
discs D1, D2 and D3, respectively. Cervical plates are defined by
"levels" wherein the term "level" designates the number of
intervertebral disc spaces which are traversed by the cervical
plate. Thus for example the cervical plate go shown in FIG. 22
spans three different intervertebral spaces D1, D2 and D3 between
vertebral bodies V1, V2, V3 and V4 so that the embodiment shown
therein is a three level plate. Cervical plates can come in a
longer size, i.e., up to four levels or of course in smaller sizes,
i.e., two levels or one level. For convenience, the invention is
described throughout the present specification with respect to one
level and two level cervical plates. It is to be understood that
strictly for purposes of illustration FIG. 22 shows the cervical
plate go against what appears to be an essentially normal spine. In
practice, however, as discussed above, when the cervical plate is
attached, it will be subsequent to surgery that may have replaced
some or all of the intermediary discs and vertebrae with a
corpectomy to remove vertebrae which is replaced with a bone
graph/plug or a mesh/cage implant or the like.
[0038] A cervical plate can have different openings serving
different purposes. In FIG. 22 the pair of holes 100 are provided
for attaching two bone screws to the upper and lower vertebrae
adjacent thereto is the form of bone screw holes to which the
locking element of the present invention will be applied. However,
in combination with bone screw holes 100, the cervical plate can
have other bone screw holes such as simple holes 101 which are
shown in FIG. 22 for attachment if desired, between the upper and
lower bone screw holes 100. Between the attachments to the
vertebral bodies the cervical plates are provided with openings 102
which serve as windows to view into the interior of the
intervertebral spaces. There will generally be at least one such
window opening in the vicinity of each intervertebral space. As is
known, anterior cervical plates of this type, in the various
configurations, can be used to stabilize, immobilize and/or align
the cervical spine following a number of different problems. For
example, intermediate disc or discs can be removed and replaced by
a cage, mesh or bone graph/plug or allograft/autograft. In addition
to removal of the discs, the intermediate vertebrae can also be
removed. The cervical plate can also be used to correct instability
of the cervical spine caused by trauma, tumors, advanced
degenerative discs disease, cervical deformities caused by lordosis
or kyphosis or other conditions.
[0039] FIGS. 1-7 illustrate a first embodiment of the present
invention. These figures illustrate an anterior cervical plate lo
which has first, second and third recessed areas 11, 12 and 13 for
receiving bone screws through holes 17, 18; 19, 20; and 21, 22,
respectively. Between the recessed areas 11, 12 and 13 are provided
web areas 15 and 16, respectively, each including a window opening
28 and 29, respectively, for viewing the intervertebral space
adjacent thereto, as described above. In practice, each of the pair
of bone screw holes would have a locking element 30 mounted there
between. For purposes of illustration, in the first embodiment,
i.e., FIGS. 1, 2 and 5-7, the top recessed area 11 includes a
locking element 30 in the open position, the bottom recessed area
13 shows a locking element 30 in the locking position and the
middle recessed area 12 does not show any locking element, so as to
illustrate the recessed area there below.
[0040] Referring to FIG. 1 and the bottom plan view of FIG. 2, the
plates include spikes 41, 42 for initially engaging the vertebrae
when the cervical plate is first mounted thereon. Some operators
prefer to use a fixation pin in addition to the spikes 41, 42, and
for this purpose the cervical plate lo is provided with openings 23
and 24 at the top and bottom thereof, respectively.
[0041] Referring to FIGS. 1, 6 and 7, the lower bone screw holes 21
and 22 each have a bone screw 35 therein, each having a bone screw
socket 36 for receiving a screwdriver for securing the bone screws
into the bone. Referring to FIGS. 6 and 7, in a manner known per
se, the screws can be driven into the bone over a range of
transverse angles D, as shown in FIG. 6, or longitudinal angles C,
as shown in FIG. 7. Normally the range of the angles C and D is
approximately 15.degree. Referring to FIGS. 5 and 7, the cervical
plates would generally be curved in both the transverse and the
longitudinal direction. The radius of curvature of the plate in the
transverse direction would be approximately 24 mm, as represented
by arrow A, in order to fit the curvature of the vertebral bodies.
Referring to FIG. 7, the radius of curvature of the cervical plate
in the longitudinal direction would be approximately 200 mm, as
represented by arrow B.
[0042] A feature of the present invention is an elongated locking
element 30 which is mounted so as to move between an open position
as shown at recessed area 11 of FIG. 1 and a locking position as
shown at the lower recessed area 13 of FIG. 1. Referring to FIGS. 3
and 4, the locking element 30 includes a central hole 31 for
engaging the boss 27 on the cervical plate lo and additional
openings 32 and 33 offset from the pivot axis for receiving a tool
to assist in turning the locking element 30 between its open and
locking positions. To positively position the locking element 30 in
its locked position, a pair of bumps 25 and 26 on the cervical
plate are positioned to engage recesses 44 and 46, as shown in FIG.
4, on the bottom of the locking element 30. To facilitate movement
of the locking element over the bumps 25 and 26, the bottom of the
locking element 30 includes recessed inclined ramps 45 and 47 which
are deep enough to initially ride over the tops of the bumps. The
ramps stop short of the recesses 44 and 46 so that as the locking
element 30 is turned, the bumps 25, 26 will ride up the ramps and
then snap into place in the recesses 44 and 46.
[0043] The embodiment of FIGS. 1-7 illustrates a first arrangement
for attaching the locking element to the boss 27. It is noted that
the center boss 27 in recessed area 12 is essentially
frustoconical. When it is desired to attach a locking element 30 to
a boss 27, the locking element is placed thereon after which the
top of the boss 27 is swaged, as shown at 27a in FIGS. 5, 6 and 7,
so as to prevent removal of the locking element while allowing it
to pivot thereabout.
[0044] FIGS. 8, 9, 10 and 11 are intended to show various shapes of
anterior cervical plates, each intended for a different level
and/or showing a different connection and some such as FIG. 9 and
FIG. 11 showing simple bone screw holes for attachment to certain
intervening vertebrae.
[0045] Cervical plate 50 of FIG. 8 is a two level cervical plate
having pairs of bone screw holes at the two ends thereof which
would in practice incorporate the features of the present invention
and including a window opening 50a for viewing the intervertebral
space there between. FIG. 9 illustrates another cervical plate 51
which also would include the features of the present invention at
the pairs of holes at the top and bottom thereof. This is a two
level cervical plate having viewing holes 51a for viewing the
intervertebral spaces and a simple central bone screw hole 51b.
FIG. 10 illustrates a three level cervical plate 52 having the pair
of bone screw holes which could receive the locking element of the
present invention at all four connections to the vertebrae, and
showing window opening 52a for viewing the three intermediate
intervertebral spaces. FIG. 11 shows a cervical plate 53 which is
the same one previously described with respect to FIG. 22, and
having three viewing windows 53a and two simple bone screw holes
53b.
[0046] FIGS. 12-18 illustrate another embodiment of the present
invention which is identical in all respects to the embodiment of
FIGS. 1-12 with respect to the features of the locking element (and
other than the fact that some of the embodiments of FIGS. 1-12 show
different shapes and arrangements of cervical plates), except for a
different arrangement for connecting the locking element to the
cervical plate.
[0047] For convenience, FIGS. 12-18 use the same numerals as in
FIGS. 1-7 for identical parts. Different numerals are used with
respect to the modified locking element. As seen in FIGS. 12 and
13, in this case the recessed areas 11, 12 and 13 which receive the
locking element include a through hole 65 instead of raised boss
27. The locking element 55, as shown in FIGS. 14-16, instead of
having the opening 31 in the center thereof, has a raised boss 62
on the bottom thereof. This locking element 55 includes tool
receiving holes 56 and 57 which are similar to holes 32 and 33 of
FIGS. 1-7. In a manner similar to the embodiment of FIGS. 1-7, in
this locking element 55 there are provided recesses 58 and 60 for
cooperating with bumps 25 and 26 and recessed ramps 59 and 61 for
riding up over the bumps and allowing the bumps to snap into place
into the recesses 58 and 60, precisely as described above with
respect to FIGS. 1-7.
[0048] Referring to FIG. 17, the through hole 65 has a chamfer 65a
at the bottom thereof. FIG. 17 illustrates the locking element 55
with a boss 62 still of the shape as shown in FIGS. 15 and 16,
extending through the opening 65. The assembly process, however, is
completed by swaging the lower end of the boss 62 as shown at 62a
in FIG. 18 to secure the locking element 55 onto the plate 54 while
allowing it to pivot relative to the plate 54.
[0049] FIGS. 19-21 illustrate the anterior cervical plate 54 taken
along plane 18-18 of FIG. 12 but showing a modified attachment
between the locking element and the cervical plate. Referring to
FIG. 19, the locking element is of the type 30 shown in FIGS. 1-7
with an opening 31 therein. The plate is of the type 54 shown in
FIGS. 12-17 with a through hole 65 having a chamfer 65a. In this
embodiment, a tapered post 70 is inserted up through the through
hole 65 such that its conical surface engages the chamfer 65a with
the upper end of post 70 located above the upper surface of locking
element 30 as shown in FIG. 20. The post 70 is then fixed to the
plate at its bottom and swaged at the top as shown at 70a in FIG.
21 in order to allow the locking element 30 to pivot relative to
the cervical plate 54.
[0050] Although the operation of the present invention will be
apparent from the preceding discussion, for convenience the
operation will be summarized herein. First, after the problem of
the cervical spine has been surgically repaired, the anterior
cervical plate is placed against the anterior of the cervical
vertebrae. Initially it is held there by the spikes 41, 42 and/or
by fixation pins passing through the openings 23, 24. The method of
preparing the holes in the vertebral bodies for the bone screws is
well known, conventional and need not be further described
herein.
[0051] At the recessed areas which include the locking element of
the present invention, the screws are tightened to the point where
their upper surfaces are at or slightly below the level of the
recessed areas so that the locking elements, when pivoted to the
locking position, will prevent the screws from backing out but not
exert an inward force thereon. The bone screws for the holes
adjacent the locking elements are inserted and attached when the
locking element 30 or 55 is in the open position as shown at the
top of FIGS. 1 and 12. After the bone screws are tightened in
place, a tool (not shown) engages the openings 32 and 33 or 56 and
57 to turn the locking element clockwise. On the bottom of the
locking element, ramps 44, 47 or 59, 61 on the bottom of the
locking element will ride up the bumps 25, 26 until the locking
element moves to its locking position as shown at the bottom
recessed area 13 of FIGS. 1 and 12. At this point the bumps 25 and
26 have snapped into their respective recesses 44 and 46 for
locking element 30 and 58 and 6o for locking element 55. A
preferred material for the cervical plate would be implantable
Titanium alloy, Ti-6 Al-4V per ASTM F-136.
[0052] Although the invention has been described in considerable
detail with respect to preferred embodiments, it will be apparent
that the invention is capable of numerous modifications and
variations, apparent to those skilled in the art, without departing
from the spirit and scope of the invention.
* * * * *