Note: Descriptions are shown in the official language in which they were submitted.
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MODULAR LORDOTIC INTERBODY
SPINAL FUSION IMPLANT
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates generally to interbody
spinal fusion implants, and in particular to spinal fusion
implants configured to restore and maintain two adjacent
vertebrae of the spine in correct anatomical angular
relationship.
Description of the Related Art
Both the cervical and lumbar areas of the human spine
are, in a healthy state, lordotic such that they are curved
convex forward. It is not uncommon that in degenerative
conditions of the spine that lordosis is lost. This
effectively shortens the spinal canal which decreases its
capacity. Further, the absence of lordosis.moves the spinal
cord anteriorly where it may be compressed against the
posterior portions of the vertebral bodies and discs.
Finally, such a loss of lordosis disturbs the overall
mechanics of the spine which may cause cascading
degenerative changes. throughout the adjacent spinal
segments.
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The surgical treatment of those degenerative conditions of the spine in which
the spinal discs are in various states of collapse, and out of lordosis,
commonly involves
spinal fusion. That is the joining together of adjacent vertebrae through an
area of shared
bone. When the shared bone is in the area previously occupied by the
intervertebral disc
that is referred to as an interbody fusion.
The Parent Application taught the use of artificial spinal fusion implants
that
were capable of being placed between adjacent vertebrae, and which implants
were capable
of containing and providing fusion promoting substances including bone at the
fusion site.
These devices were further capable of restoring the height of the disc space
and of
supporting the spine, and were self stabilizing as well as being stabilizing
to the spinal area
where implanted.
SUMMARY OF THE INVENTION
In one aspect, the present invention relates to an interbody spinal fusion
implant for fusion of two adjacent vertebral bodies in the human spine,
comprising a
plurality of modular members, each of the modular members having a height
substantially
equal to the surgically corrected height of the disc space and a width
substantially less than
the transverse width of the vertebral bodies, each of the modular members
comprising an
insertion end, a trailing end, opposed upper and lower portions adapted to be
placed in
contact with the end plates of the adjacent vertebral bodies, and side walls
connecting the
upper and lower portions, the upper and lower portions forming a support
structure
including at least a part of the surfaces of the upper and lower portions
between the side
walls for bearing against the end plates of the adjacent vertebral bodies, the
upper and lower
portions being disposed at least in part in a converging angular relationship
along a
longitudinal axis between the insertion and trailing ends to induce angulation
of the adjacent
vertebral bodies, the side walls of each of the modular members adapted to be
positioned
beside and in contact with at least another of the modular members in a side
to side
orientation within the space created between the adjacent vertebral bodies,
whereby the
plurality of modular members placed together form the spinal implant.
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The present invention is directed to interbody spinal fusion implants having a
structural configuration that provides for the maintaining and creating of the
normal
anatomic angular relationship of two adjacent vertebrae of the spine to
maintain and create
spinal lordosis. The spinal fusion implants of the present invention are sized
to fit within the
disc space created by the removal of disc material between two adjacent
vertebrae and
conform wholly or in part to the disc space created. The spinal fusion
implants of the
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upper and lower surfaces that form a support structure for
bearing against the end plates of the adjacent vertebrae.
In the preferred embodiments, the upper and lower surfaces
are disposed in a converging angular relationship, to each
other such that the -implants of the present invention have
an overall "wedged-shape" in an elevational side view. The
angular relationship of the wpper and lower surfaces places
and maintains the vertebrae adjacent to those surfaces in
an angular relationship to each other, creating and
l0 maintaining the desired lordosis.
The implants of the present invention may have
surface irregularities to increase their surface area;
and/or to further engage the adjacent vertebrae and to
enhance stability. The lordotic implants of the present
invention may have surface irregularities that are uniform
in height along the longitudinal axis of the upper and
lower vertebrae engaging surfaces, or may increase in
height from one end of the implant to the other. That is,
the implant body and the surface formed and the projections
may be similarly wedged. The outer contour of the surface
projections may be more or less rectangular while the
underlying implant may be wedge-shaped; or the reverse
wherein the underlying implant body is more or less
rectangular while the contour of the surface projections
are' wedge-shaped from one end of the implant to the other..
The implants of the present invention have
various faces which may be curved so as to conform to the
shape of the vertebral surfaces adjacent to the area of the
disc removal. specifically the upper and/or lower surfaces
may be convex, and/or the front and/or rear surfaces may be
convex. The surfaces of the implants of the present
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invention may have openings Which may or may not pass all
' the way through them, and a ~ central chamber in
communication to the surface through holes. The openings
may be of random sizes, and/or shapes, and/or
5~ distributions. The implants themselves may be composed of
materials, and/or have surface treatments, to encourage
microscopic bone ingrowth into the implants.
In the performing of a posterior lumbar interbody
fusion, it is not possible to replace the removed portions
to of the disc, if a total nuclear discectomy has been
performed, with a single large implant as the delicate
dural sac containing the spinal cord, and the nerve roots
cover at all times at least some portion of the posterior
disc space. As set forth in the Parent Application, the
15 use of "modular implants" is appropriate in such cases.
,The modular implants being approximately as long as the
depth of the disc material removed, but being considerably
narrower, such that they can be introduced into the disc
space from the posterior aspect to either side of the dural
2o sac, and then aligned side to side within the disc space so
that a number of them each having a length consistent with
the depth of the disc removed in that area would in
combination have a width equal to the width of the disc
material removed.
25 The modular implants of the present invention may
be generally wedge-shaped and may have upper and lower
surf aces conforming to the contours of the vertebral
endplates, which contours include but are not limited to
being relatively flat or convex. As the disc spaces in the
3o lumbar spine are generally lordotic, said implants in the
preferred embodiment would be taller anteriorly, that is at
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the implant's insertion end, and less tall posteriorly,
that is at the implant's trailing end. To introduce an
implant that is taller at its insertion end than the space
available at the posterior aspect of the disc space, even
5 when that disc space is optimally distracted, is
problematic.
The modular implants of the present invention
provide two solutions to the problem. In the first ,
embodiment, the modular implants may have a reduced size at
their insertion end, including but not limited to a bullet
nose, a convexity, and a chamfer to a smaller front
surface. This then provides that the implant has an area
small enough to be introduced into the posterior aspect of
the disc space when the disc space is adequately distracted
and the contour of that specialized leading portion of the
implant is such that it then allows for a ramping up of the
adjacent vertebrae relative to the implant as the implant
is advanced forward into the disc space.
The implants of the present invention provide a
second solution to this same problem. In the preferred
embodiment of the modular implant, the implant is again
wedge-shaped in the side elevational view and is taller at
its insertion end than a;t its trailing end. However, the
implant incorporates at its trailing end a means for
engaging insertion instrumentation such as the box and.
threaded opening configuration disclosed in the Parent
Application. Since in the preferred embodiment these
implants are wedge-shaped in the side elevational view when
upright but are generally rectangular when viewed from the
top plan view, these implants are therefore designed to be
introduced into the disc space on their side such that the
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side walls of the implants are adjacent to the end plates
of the adjacent vertebrae. The implants have a- side:-to-
side dimension that is less than the dimension through the
insertion end of the implant when upright. It is .possible
to easily insert these implants with them on their side and
then to use the insertion instrument engaged to the implant
to rotate the implants ninety degrees into the fully
upright position, once they have been fully inserted. Once
inserted, the upper and lower surfaces are adjacent to the
endplates of the adjacent vertebrae and create and maintain
the desired angular relationship of the adjacent vertebrae
as the upper and lower walls are angled with respect to
each other.
In an alternative embodiment of the present
invention, a mechanical implant which may be inserted in a
collapsed position and which may then .be adjusted to
increase in height so as to provide for the optimal
restoration of the height of the space between the adjacent
vertebrae is disclosed. The mechanical implant may, be
wedge-shaped, and have upper and lower surfaces, th-a
contours of which generally conform to the contacted areas
of the adjacent vertebral endplates and which contours may
include but are not limited to being relatively flat, or
convex. Further, the mechanical implant may be wedge-
shaped or generally rectangular, but capable of increasing
in both height and the extent of wedging when adjusted.
This may easily be achieved by having one of the two wedge
mechanisms employed in the example given being larger, or
steeper than the other. Alternatively, a single wedge may
be utilized, and if it is desired to achieved increased
height at one end of the implant while restricting the
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height at the other, then the end of the implant may
incorporate a hinge means and the height expansion at the
other end achieved by drawing a wedge member, bar, ball, or
other means from the far end towardlthe hinged end so as to
5~ drive said upper and lower surfaces apart in a wedged
fashion.
In an alternative embodiment of the present
invention, an implant having a mechanically deployable bone
engaging means is taught. Such an implant is generally
wedge-shaped in the side elevational view and has upper and
lower surfaces generally conforming to the contour of the
vertebral endplates where contacted by the implant, and
which upper and lower surfaces may be but are not limited
to being either flat ox convex. The use of such deployable
bone engaging means are particularly of value in that the
largest possible implant may be inserted into a disc space
and the vertebral engaging means, which if, fixed to the
surface would have
blocked the insertion of the implant, may then be deployed
after the insertion such that the distance from the tip of
the upper and lower bone engagement means exceeds the
height of the space available for insertion. Such a
feature is of particular value when the implant itself is
wedge-shaped as the considerable compressive loads across
the lumbar spine would tend to drive a wedge-shaped implant
out of the disc space.
OBE--TF. T.~~ OF ~F PRESENT
It is an object of the present invention to
provide a spinal fusion implant that is easily inserted
into the spine, having a tapered leading end;
It is another object of the present invention to
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provide a spinal fusion implant that tapers in height from
one end to the other consistent with the taper of a normal
spinal disc; ,
It is yet another object of the present invention
to provide a spinal fusion implant that is capable of
maintaining anatomic alignment and lordosis of two adjacent
vertebrae during the spinal fusion process;
It is still another object of the present
invention to provide a spinal fusion implant that is self
stabilizing within the spine;
It is yet another object of the present invention
to provide a spinal fusion implant that is capable of
providing stability between adjacent vertebrae when
inserted;
It is further another object of the present
invention to provide a spinal fusion implant that is
capable of spacing apart and supporting adjacent vertebrae
in an angular relationship during the spinal fusion
process;
It is still further another object of the present
invention to provide a spinal fusion implant that fits
between to adjacent vertebrae and preserves the end plants
of those vertebrae; and
It is another object of the present invention to
provide a spinal fusion implant having a shape which
conforms to the endplates of the adjacent vertebrae; and
These and other objects of the present invention
will become apparent from a review of the accompanying
drawings and the detailed description of the drawings.
BRTF D ~ RT TTON OF TT-~F D AWTNC''~
Figure 1 is a perspective view of the lordotic
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interbody spinal fusion implant of the present invention
' with a slidable door shown in a.partially open position
providing access to the internal chamber of the implant.
Figure 2 is a top plan view of the lordotic
5~ interbody spinal fusion implant of the present invention.
Figure 3 is a left side elevational view of the
lordotic interbody spinal fusion implant of the present
invention.
Figure 4 is a right side elevational view of the
lordotic interbody spinal fusion implant of the present
invention.
Figure 5 is a front end view of the lordotic
interbody spinal fusion implant of the present invention
showing the slidable door in a partially open position.
Figure 6 is a rear end view of the lordotic
~interbody spinal fusion implant of tie present invention
showing the means for engaging insertion instrumentation.
Figure 7 is an enlarged fragmentary view along
line 7 of Figure ,2 illustrating the bone engaging surface
configuration of the lordotic interbody spinal fusion
implant of the present invention.
Figure 7A is an elevational side view of a
segment of the spinal column having the lordotic implant of
the present invention inserted in the disc space at
different disc levels between adjacent vertebrae to restore
and maintain the correct anatomical alignment of the
adjacent vertebrae.-
Figure 8 is a top plan view of an alternative
embodiment of the lordotic interbody spinal fusion implant
of the present invention.
Figure 9 is a left side elevational view of the
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lordotic interbody spinal fusion implant of Figure 8.
Figure 10 is a front end view of the lordotic
interbody spinal fusion implant of Figure 8.
Figure 11 is a rear end view of the lordotic
5 interbody spinal fusion implant of Figure 8 showing the
means for engaging insertion instrumentation.
Figure 12 is an enlarged fragmentary view along
line 12 of Figure 8 illustrating the surface configuration
the lordotic interbody spinal fusion implant of the present
10 invention.
Figure 13 is a top plan view of an alternative
embodiment of the lordotic interbody spinal fusion implant
of the present invention made of a mesh-like material.
Figure 14 is a left side elevational view of the
lordotic interbody spinal fusion implant of Figure 13.
Figure 15 is a front end view of the lordotic
interbody spinal fusion implant of Figure 13.
Figure 16 is a rear end view of the lordotic
interbody spinal fusion implant of Figure 13 showing the
means for engaging insertion instrumentation.
Figure 17 is an enlarged fragmentary view along
line 17 of Figure 13 illustrating the surface configuration
of the lordotic interbody spinal fusion implant of the
present invention
Figure 18 is a perspective view of an alternative.
embodiment of the lordotic interbody spinal fusion implant
of the present invention.
Figure 19 is a top plan view of the lordotic
interbody spinal fusion implant of Figure 18.
Figure 20 is a left side elevational view of the
lordotic interbody spinal fusion implant of Figure 18. --
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Figure 21 is a rear end view of the lordotic
interbody spinal fusion implant'of Figure 18.
Figure 22 is a front end view of the lordotic
interbody spinal fusion implant of~Figure l8.
5' . Figure 23 is an enlarged fragmentary view along
line 23 of Figure 18 illustrating the surface configuration
the~lordotic interbody spinal fusion implant of the present
invention.
Figure 24 is a top plan view of an alternative
embodiment of the lordotic interbody spinal fusion implant
of the present invention.
Figure 25 is a left side elevational view of the
lordotic interbody spinal fusion implant of Figure 24.
Figure 26 is a rear end view of the lordotic
'I5 ~ interbody spinal fusion implant of Figure 24.
Figure 27 is a front end v~.ew of the lordotic
interbody spinal fusion implant of Figure 24.
Figure 28 is an enlarged fragmentary view along
line 28 of the lordotic interbody spinal fusion implant of
Figure 24 illustrating the surface configuration of the
lordotic interbody spinal fusion implant of the present
invention.
Figure 29 is a sectional view along lines 29--29
of Figure 28 the lordotic interbody spinal fusion implant
of the present invention.
Figure 30 is a side elevational view of a segment
of the human spinal column shown with an alternative
embodiment of the lordotic spinal fusion implant of the
present invention that is adjustable and expandable shown
in sectional view inserted in the disc space levels to
restore and maintain the correct anatomical alignment of
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the adjacent vertebrae.
Figure 31 is a side cross sectional view of an
alternative embodiment of the lordotic implant of the
present invention having movable projections, in the form
5' of spikes 708, which are movable from a first position
within the implant 700 to a second position extending to
the~exterior of the implant.
j~,ETAT .RD D .~ .$TPTTON OF THE i[1~AWT
Referring to Figures 1 through 7 the lordotic
interbody spinal fusion implant of the present invention
for use in the disc space between two adjacent vertebrae,
generally referred to by the numeral 100, is shown. The
implant 100 has a generally rectangular configuration,
having an upper surface 112 and a lower surface 114. In
the preferred embodiment, the upper and lower surfaces 112
,and 114 of implant 100 are disposed in.a converging angular
relationship toward each other such that the implant 100
appears "wedge-shaped" from a side elevational view .as
shown in Figures 3 and 4. The upper and lower surfaces 112
and 114 have an interior surface which form a support
structure for bearing against the endplates of the adjacent
vertebrae between which the implant 100 is inserted. The
angular relationship of the upper and lower surfaces 112
and 114 places and maintains the vertebrae adjacent to
those surfaces in an angular relationship, creating and
maintaining the desired lordosis of the spine.
The upper and lower surfaces 112 and 114 of the
implant 100 may be flat or curved to conform to the shape
of the end plates of the adjacent vertebrae between which
the implant 100 is inserted. The implant 100 conforms t.o
the shape of the nucleus pulposus and a porpon of the
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annulus fibrosus removed from the vertebrae. The upper and
lower surfaces 112 and 114 comprise surface roughenings
that provide a surface suitable for engaging the adjacent
vertebrae to stabilize the implant 100 within the disc
space once surgically implanted. The-surface roughenings
of the upper and lower surfaces 112 and 114 comprise
surface knurling 121.
Referring to Figure 7, an enlarged fragmentary
view of the surface knurling 121 of the implant 100 is
l0 shown as a diamond-shaped bone engaging pattern. The
implant 100 may have surface knurling 121 throughout the
entire upper and lower surfaces 112 and 114, throughout
only a portion of the upper and lower surfaces 112 and 114,
or any combination thereof, without departing from the
scope of the present invention. It is also appreciated
that the surface knurling 121 may have various
configuration other than the configuration shown.
In this embodiment; the implant 100 is hollow and
comprises a plurality of openings 115 of passing through
the upper and lower surfaces 112 and 114 and into a central
hollow chamber 116. The openings 115 provide for bone
growth to occur from thevertebrae through the openings 115
to the internal chamber 116. While the openings 115 have
been shown in the drawings as being circular, it is-
appreciated that the openings 115 may have any shape, size,
configuration or distribution suitable for use in a spinal
implant without departing from the scope of the present
invention. For example, the openings may have a tear-drop
configuration as shown in opening 115a in Figures l and 2.
The upper and lower surfaces 112 and 114 of the implant
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100 are supported and spaced apart by a side wall 118,
which may also comprise a plurality of, openings 122.
The implant lOO has an insertion end 120 and a
trailing end 130 both of which maybe curved or flat. The
5' trailing end 130 of the implant may be convex to conform to
the curvature of the vertebrae and .has a means for
enlarging an implant insertion instrument comprising a
depressed portion 124 with a central threaded opening 26
for receiving the engaging end of a driving instrument.
The insertion end 120 of the implant 100 comprises an
access opening 132 and a slidable door 134 which closes_the
opening 132. The slidable door 134 covers the opening 132
into the chamber 116 and permits the insertion of
autogenous bone material into the chamber 116.
'15 In use; the slidable door 134 is placed in the
ppen position for loading material into the chamber 116.
The slideable door 134 has a. depression 136 for
facilitating the opening and closing of the door 134. The
internal chamber 116 can be filled and hold any natural or
artificial osteoconductive, osteoinductive, osteogenic, or
other fusion enhancing material. Some examples of such
materials are bone harvested from the patient, or bone
growth inducing material such as; but not limited to,
hydroxyapatite, hydroxyapatite tricalcium phosphate; or
bone morphogenic protein. The implant 100 itself is made
of material appropriate for human implantation such as
titanium and/or may be made of, and/or filled and/or coated
with a. bone ingrowth inducing material such as, but not
limited to, hydroxyapatite or hydroxyapatite tricalcium
phosphate or any other osteoconductive, osteoinductive,
osteogenic, or other fusion enhancing material.
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The fusion enhancing material that is packed within the
chamber 116 of the implant 10 serves to promote bone
5 ingrowth between the implant 100 and the adjacent vertebrae.
Once the bone ingrowth occurs, the implant 100 will be a
permanent fixture preventing dislodgement of~the implant as
well as preventing any movement between the adjacent
vertebrae.
10 The slidable door 134 is then closed prior to
implantation. In the closed position, the slideable door
conforms to the curvature of the insertion end 120 of the
implant 100. Various methods of packing the implant 100
with the autogenous bone material may be used to Obtain a
15 completely packed implant 100.
The threaded end of a driving instrument is attached to
the threaded opening 126 in the trailing end 120 of the
implant 100 and the fitting of the driving instrument into
the depressed portion 124 prevents movement of the implant
100 in relationship to the driving instrument. The implant
100 is then placed at the entrance to the disc space between
the two adjacent vertebrae V. The driver instrument is then
tapped with a hammer sufficiently hard enough to-drive the
implant 100 into the disc space.
The size of the implant 100 is substantially the same
size as the disc material that it is replacing and thus will
be larger or smaller depending on the amount of disc
material removed to create the disc space in which it is to
be used. In the preferred embodiment in regard to the
lumbar spine the implant l00 is approximately 28-48 mm
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wide, approximately 36 mm being preferred. The implant 100
has a height conforming to the restoration of the anatomic
height of the disc space the average height would range
from e-16 mm, with 10-12 of which being the .preferred
average height. The depth would at is maximum range from
20 to 34~;mm with 26 to 32 being the preferred maximum
depth. In the cervical spine the width of the implant is
in the range of approximately 14-28 mm; with the preferred
width being 18-22 mm. The implant has a height in the
range of approximately 5-10 mm with the preferred height
being 6-8 mm. The implant has a depth in the range of
approximately 11-21 mm with the preferred depth being 11-13
mm.
Referring to Figure 7A, a side elevational view
of the lateral aspect of a segment of the spinal column' S
is shown with the implant 100 inserted in the disc space DZ
between two adjacent vertebrae v2 and V3. The implant'100
is inserted in the direction of arrow A into the disc space
D2 and maintains the two vertebrae V2 and V3 in anguhar
relationship to each other such that the natural lordosis
of that segment of the spinal column S is restored. The
forward advancement of the implant 100 is blocked by the
natural bone processes B in the endplates of the vertebrae
VZ and V3. Backing out of the implant 100 is prevented by
the bone engaging surface knurling 121 of the upper and
lower surfaces 1I2 and 114.
Referring to Figure 8-12, an alternative
embodiment of the lordotic interbody spinal fusion implant
of the present invention, generally referred to by the
numeral 200, is shown. The implant 200 has a similar
overall configuration as the implant 100 described above.
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In the preferred embodiment, the implant 200 is solid and
comprises a plurality of channels~2Z5 passing from the
upper surface 212 to the lower surface 214 through the
implant 200. The channels 215 provide for bone ingrowth
5~ and facilitate the incorporation of the implant 200 into
the spinal fusion mass. The channels may also be loaded
with fusion promoting materials such as those described
above, prior to implantation. It is appreciated that the
channels 215 need not pass all the way through the implant.
200, but can have a configuration similar to wells, which
may hold fusion promoting materials and permit bone
ingrowth into the upper and lower surfaces 212 and 214 of
the implant 200.
In addition to the channels 215, the implant 200
may have small openings 222 on the side wall 218 which may
,or may not pass through the entire implant 200. The same
openings 222 may be in communication with the channels 215
such that bone ingrowth may occur from the openings 222 to
the channels 215 ~o lock the implant 200 into the fusion
mass. If the openings 222 do not pass through the entire
implant 200, the may function as small wells for holding
fusion promoting materials or described above.
In the preferred embodiment of implant 200,
the channels 215 have a diameter in the range of 0.1 mm to
6 mm, with 2-3 mm being the preferred diameter. The
openings 222 have a diameter in the range of 0.1 mm to &
mm, with 1-3 mm being the preferred.diameter range. It is
appreciated that although the channels 215 and openings 222
are shown having a generally rounded configuration, it is
within the scope of the present invention that the channels
215 and openings 222 may have any size, shape,
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18 , .
w configuration, and distribution suitable for the intended
purpose. The implant 200, has a plurality~of
ratchetings 250 on the upper and lower surface 212 and 214
for engaging the bone of the adjacent vertebrae.. The
ratchetings 250 comprise a bone engaging edge 252 and
angled segment 254.
Referring specifically to Figure 9, the implant'
200 has a wedge-shaped elevational side view in which the
trailing end 230 is taller than the insertion end 220: The
plurality of ratchetings 250 are oriented in the direction
of the insertion end 220 to provide for a one-way insertion
of the implant 200 as the bone engaging edge 252 engages
the vertebrae and prevents the implant from backing out
once implanted. Alternatively, the trailing end
ratchetings could be of a lessor height such that the
overall shape of the ratchetings as a group is convex.
Referring to Figure 11, the trailing end 230 of
implant 200 has means for engaging insertion
instrumentation comprising a thread opening 226 ,as
described above for implant 100.
Referring to Figure 12, an enlarged fragmentary
view along line 12 of Figure 8 illustrating the surface
configuration the implant 200-is shown. The upper and
lower surfaces 212 and 214 of implant 200, in addition to
the ratcheting 250 comprise a porous texture 260 to present
an irregular surface to the bone to promote bone ingrowth.
The porous texture 260 is also able to hold fusion
promoting materials and provides for an increased surface
area to engage the bone in the fusion process and to
provide further stability. The porous texture 260 may also
be present on the side walls 218. It is appreciated that
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the outer surface and/or the entire' implant 200, may
comprise any other porous material or roughened surface
sufficient to hold fusion promoting substances and/or allow
for bone ingrowth and/or engage the bone during the fusion
, process: The implant 200 may be further coated with
bioactive fusion promoting substances ihcluding; but not
limited to, hydroxyapatite compounds, osteogenic proteins
and bone morphogenic proteins.
Referring to Figures 13-17, an alternative
embodiment of the lordotic interbody spinal fusion implant,
generally referred to by the numeral 300, is shown. The
implant 300 is made of a mesh-like, material comprising
strands, which may be made of metal, that are pressed
together and molded. The upper and lower surfaces 312 and
314 may be convex and conform to the natural surface
curvature of the end plates of the. vertebrae. In addition,
the entire implant 300 may be molded to .a shape that
canforms to the shape of the disc space created by the
removal of discmaterial from between two adjacent
vertebrae. In this manner, the implant 300 has curved
upper and lower surfaces 312 and 314, a curved side wall.
318 and chamfered edges 319.
Referring to Figure 7A, the implant 300 is shown
inserted in the direction of arrow A into the disc space D1
between adjacent vertebrae Vl and V2. The implant 300
conforms to the endplates of the adjacent vertebrae V, and
VZ as the upper and lower surfaces 312 and 314 are convex,
and the side walls 318 are curved to conform to the natural
curvature of the vertebrae Vl and V2. In this manner, the
implant 300 has the same dimensions as the disc material
removed from between the two adjacent vertebrae VI and V2.
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20 ,.
The implant 300 may be made wholly or in part of
a solid material and/or a porous material, and/or a mesh-
like material. The implant 300 may have a surface
comprising of a porous material, a mesh-like material, or
have a surface that is roughened. It is appreciated that
the implant 300 may be solid or may be partially hollow and
include at least one internal chamber in communication with
said upper and lower surfaces.
As shown in Figure 17, the mesh-like material
comprises strands that are formed and pressed together such
that interstices 339, capable of retaining fusion promoting
material and for allowing for bone ingrowth, are present
between the strands in at least the outer surface of
implant 300. Alternatively, it is appreciated that the
implant 300 may be made of a cancellous material, similar
in configuration to human cancellous bone, having
interstices allowing for bone ingrowth. As the implant 300
may be made entirely or in part of the cancellous material,
the interstices may be present in the outer surface of the
implant 300 and/or within the entire implant to promote
bone ingrowth and hold bone fusion promoting materials.
Referring to Figures 18-23 an alternative
embodiment of the implant of the present invention,
generally referred to by the numeral 400, is disclosed.
The implant 400 has a substantially rectangular shape
having upper and lower surfaces 412 and 414. The upper and
lower surfaces 412 and 414 support the adjacent vertebrae
and are disposed in a converging angular relationship to
each other in the same manner described above.
The implant 400 has a width W that is
substantially less than the width of the implants 100-300
CA 02447257 2003-11-19
21
such that a series of such implants 400 are used as the
interbody spinal implant, each placed closely adjacent to
one another to approximate the size of the removed disc.
The size of the implant 400 is approximately 26 millimeters
5~ in length and is wide enough so that four of them will
substantially fill the intervertebral space, depending on
which vertebrae are fused.
In the performing of a posterior lumbar interbody
fusion, it is not possible to replace the removed portions
of the disc, if a total nuclear discectomy has been
performed, with a single large implant as the delicate
dural sac containing the spinal cord and nerve roots covers
at all times at least some portion of the posterior disc
space. The use of modular implants 400 that are inserted
'separately into the disc space is appropriate in such case.
The modular implants 400 being approximately as long as the
depth of the disc material removed, but being considerably
narrower, such that they could be introduced into the disc
space from the posterior aspect to either side of the dural
sac, and then realigned side to side with the disc space so
that a number of them each having a length consistent with
the depth of the disc removed in that area would in
combination have a width equal to the width of the disc
material removed. As the disc spaces in the lumbar spine
are generally lordotic, the insertion end 420 of the
modular implants 400 would have to be taller and less tall
posteriorly at the trailing end 430.
To introduce the modular implant 400 that is
taller at its insertion end 420 than the space available at
the posterior aspect of the disc space, even when that disc
CA 02447257 2003-11-19
22
space is optimally distracted, is problematic. The modular
implants 400 of provide two solutions to the problem. The
modular implants 400 may have a reduced size at their
insertion end 420, including but not limited to, a bullet
nose, a convexity, and a chamfer to a smaller front
surface. This then provides that the implant 400 has an
area small enough to be introduced into .the posterior
aspect of the disc space when the disc space is adequately
distracted and the contour of that specialized insertion.
end of the implant 400 is such that it then allows for a
ramping up of the adjacent vertebrae relative to the
implant 400 as the implant is advanced forwardinto the
disc space.
Alternatively, or in combination with the above,
since in the preferred embodiment the implants 400 are
wedge-shaped in the side elevational view when upright but
are generally rectangular when viewed from the top plan
view, these implants may be introduced into the disc space
on their side such that the side walls of the implants are
adjacent to the end plates of the adjacent vertebrae. The
implants 400 have a side-to-side dimension that is less
than the dimension through the insertion end of the implant
400 when upright. It is possible to easily insert the
implant 400 first on their side and then to use the
insertion instrument engaged to the implant 400 to rotate
the implant ninety degrees into the fully upright position,
once it has been fully inserted. Once inserted, the upper
and lower surfaces 412 and 414 are adjacent to the
endplates of the adjacent vertebrae and create and maintain
the desired angular relationship of the adjacent vertebrae
as the upper and lower surfaces 412 and 414 of the implant
CA 02447257 2003-11-19
23
400 are angled with respect to each other.
The implant 400 has large openings 4~.5 in the
form of rectangular slots for holding fusion promoting
,, materials to promote bone growth from the vertebrae through
5~ the upper and lower surfaces 412 and 414 and into the-
interior of the implant 400. As the implant 400 is modular
and more than one is implanted at a time, 'the large
openings 415 are also present in the side walls 418 of the
implant 400 to provide for bone growth from one implant to
another implant such that after successful fusion; the
modular implants 400 are interconnected to form a single
unit.
Referring to Figure 21, the trailing end 430 of
the implant 400 is shown having an insertion instrument
engaging means comprising a rectangular slot 424 and
threaded opening 426. '.
Referring to Figure 23, an enlarged fragmentary
view along line 23 of Figure l8 illustrating the surf ace
configuration they implant 400 is shown. The surface
configuration of the implant 400 is the same as the porous
texture 260 described above.
Referring to Figure 24, an alternative embodiment
of the lordotic interbody spinal fusion implant of the
present invention, generally referred to by the numeral
500, is shown. The implant 500 is a modular implant and
has a similar overall configuration as implant 400. The
implant 500 instead of having slots 415 has an upper and
lower surfaces 512 and 514 that are capable of receiving
and holding bone, or other materials capable of
participating in the fusion process and/or capable of
promoting bone ingrowth. In the preferred embodiment, the
CA 02447257 2003-11-19
24
. upper and lower surfaces 512 and 514 comprise a plurality
of posts 540 that are spaced apart to provide a plurality
of interstices 542 which axe partial wells with incomplete
walls capable of holding and retaining milled bone material
or any artificial bone ingrowth promoting material. The
implant 520 maybe prepared for implantation by grouting or
otherwise coating the surface 538 with the appropriate
fusion promoting substances.
Referring to Figure 28 and 29, an enlarged view.
of the upper surface 512 of the implant 500 and a partial
cross section thereof are shown. In the preferred
embodiment, the posts 540 have a head portion 544 of a
larger diameter than the remainder of. the posts 540, and
each of the interstices 542 is the reverse configuration of
the posts 544, having a bottom 546 that is wider than the
entrance 548 to the interstices 542. Such a configuration
of the posts 540 and interstices 542 aids in the retention
of bone material in the surface 538 of the implant 520 and
further assists in the locking of the implant 520 into the
bone fusion mass created from the bone ingrowth. As the
bone ingrowth at the bottom 546 of the interstices 542 is
wider than the entrance 548, the bone ingrowth cannot exit
from the entrance 548 and is locked within the interstice
542. The surface 538 of the implant 520 provides for an
improvement in the available amount of surface area which
may be still further increased by rough finishing, flocking
or otherwise producing a non smooth surface.
In the preferred embodiment, the posts 540 have
a maximum diameter in the range of approximately 0.1-2 mm
3d and a height of approximately 0.1-2 mm and are spaced apart
a distance of approximately 0.1-2 mm such that the
CA 02447257 2003-11-19
interstices 542 have a width in the range of approximately
0.1 to 2 mm. The post sizes, shapes, and distributions may
be varied within the same implant.
It is appreciated that the implant 500 shares the
5 ~ same structure and features of the implant 400 described
above.
Figure 30 is a side elevational view of a segment
of the human spinal column S shown in lordosis with an
alternative embodiment of the lordotic spinal fusion
l0 implant referred to by the numeral 600, that is adjustable
and expandable shown inserted in a space to xestore and
maintain the correct anatomical alignment of the adjacent
vertebrae. The implant 600 comprises a lower member 682
and an upper member 684 which when fitted together form an
~15 essentially rectangular implant. The upper member 684 and
the lower member 682 have hollow portions that face one
another and receive tapered wedges 686 and 688 that fit
within the hollow portion of the upper and lower members
682 and 684. The upper and lower members 682 and 684 each
20 have a wedged interior surface 689a and 689b which are
angled towards the interior of the implant 600. The wedges
682 and 684 are such that at their large end, they are
higher than the combined hollow space between the upper and
lower members 684 and 682; and shallower at the other end
25 than the hollow space between the upper and lower members.
The wedges 686 and 688 have a central threaded
opening 690 and 692 in alignment with each other for
receiving threaded screw 694. As the screw 694 is threaded
into the opening 690, the wedges 686 and 688 abut the
interior sloped surfaces 689a and 689b of the upper and
lower members 682 and 684. As the screw 694 is turned, the
CA 02447257 2003-11-19
26
wedges 686 and 688 are drawn together, and the sloped
portions of the wedges force the upper member 682 away from
the lower member 684. As the interior sloped surfaces 6f9a
and 689b have a greater slope near the trailing end 630,
than near the insertion end 620, the upper and lower
members 6,82 and 684 are forced apart more at the .insertion
end 620 than at.the trailing end 630. As a result, the
upper and lower members 682 and 684 are disposed at a
converging angular relationship to each other and support
the adjacent vertebrae V1 and VZ in the same angular
relationship.
Referring to Figure 31, an alternative embodiment
of the implant of the present invention, generally referred
to by the numeral 700, is shown. The implant 700 has
movable projections, in the form of spikes 708, which are
movable from a first position within the implant 700 to a
second position extending outside of the implant. The
implant 700 is of .a generally rectangular configuration,
having a top surface 702 and a bottom surface 704 of the
implant with slots 706 for permitting pivotal member 707
having spikes 708 at their ends to project through said .
slots 706. The spikes 708 are pinned at one end 710 within
the, implant 700.
The implant 700 has opposing wedge shaped members.
?12 and 714 having a central threaded opening 716 for
receiving a threaded screw 718 having a head 720 and a slot
722. The wedges 712 and 714 are facing each other so that
upon turning of the screw 718, will the two wedges 712 and
714 are drawn together to cause the spikes 708 to pivot
about their end 710 and project to the exterior of the
implant 700 through the aligned slots 706. The implant
CA 02447257 2003-11-19
27
700 may comprise a series of holes in the upper and lower
surfaces 702 and 704 for promoting bone ingrowth and
fusion.
Iri use, after the removal of the'disc material,
the implant 700 with the spikes 708 in their withdrawn
position, is inserted into the disc space. Then the screw
718 is turned until the spikes 708 are forced to enter the
vertebrae and the implant 700 is thus held firmly in place.
While the invention has been described with
regards to the preferred embodiment. and a number of
alternative embodiments, it is. recognized that other
embodiments of the present invention may be devised which
would not depart. from the scope of the present invention.
