U.S. patent application number 09/737074 was filed with the patent office on 2002-11-14 for interbody spine fusion cage.
Invention is credited to Malone, David.
Application Number | 20020169507 09/737074 |
Document ID | / |
Family ID | 37911861 |
Filed Date | 2002-11-14 |
United States Patent
Application |
20020169507 |
Kind Code |
A1 |
Malone, David |
November 14, 2002 |
Interbody spine fusion cage
Abstract
An improved spine fusion cage is provided which is particularly
useful with biological compounds which are utilized in place of or
in combination with a patient's bone matter. In one embodiment
there is provided a cage with preselected perforated and
non-perforated zones to direct the growth of bone in desired
directions. In another embodiment there is provided a cage having
inner and outer perforated cage bodies separated by an annulus. An
end closure with occluding surfaces suitable for introduction into
the annulus serves to establish one or more desired zones or
patterns of occluded apertures in the cage body. In still another
embodiment an end closure having occluding surfaces is provided for
use in connection with conventional perforated fusion cages so as
to establish desired zones or patterns of occluded apertures.
Inventors: |
Malone, David; (Tulsa,
OK) |
Correspondence
Address: |
FELLERS SNIDER BLANKENSHIP
BAILEY & TIPPENS
THE KENNEDY BUILDING
321 SOUTH BOSTON SUITE 800
TULSA
OK
74103-3318
US
|
Family ID: |
37911861 |
Appl. No.: |
09/737074 |
Filed: |
December 14, 2000 |
Current U.S.
Class: |
623/17.11 |
Current CPC
Class: |
A61B 17/7064 20130101;
A61F 2/446 20130101; A61F 2230/0006 20130101; A61B 17/80 20130101;
A61F 2002/30153 20130101; A61B 17/72 20130101; A61F 2002/30364
20130101; A61F 2002/30904 20130101; A61F 2002/30677 20130101; A61B
17/8685 20130101; A61F 2002/30593 20130101; A61F 2310/00023
20130101; A61F 2/3662 20130101; A61F 2002/448 20130101; A61F
2/30744 20130101; A61F 2002/3085 20130101; A61F 2002/368 20130101;
A61F 2002/30787 20130101; A61F 2002/30235 20130101; A61F 2230/0069
20130101; A61F 2002/30604 20130101; A61F 2/36 20130101; A61F
2002/2835 20130101; A61F 2002/2817 20130101; A61B 17/864 20130101;
A61F 2002/30143 20130101; A61F 2230/0017 20130101; A61F 2002/3611
20130101; A61F 2310/00017 20130101; A61F 2002/30028 20130101; A61F
2/4611 20130101; A61F 2002/30616 20130101; A61F 2002/30115
20130101; A61F 2220/0033 20130101; A61F 2002/30932 20130101; A61F
2230/0019 20130101 |
Class at
Publication: |
623/17.11 |
International
Class: |
A61F 002/44 |
Claims
What is claimed is:
1. An interbody spine fusion cage for promoting fusion between
adjacent bone structures, comprising: a cage body having a
posterior end and an anterior end and defining an internal cavity,
the cage body further having an outer surface and a plurality of
radial apertures extending through the outer surface in
communication with the internal cavity, the outer surface
comprising a preselected pattern of perforated and non-perforated
zones; and a non-perforated end closure at each end of said cage
body, at least one of the end closures being movable so as to
provide access to the internal cavity; and wherein the preselected
pattern comprises at least a first non-perforated zone extending
from the posterior end of the cage body for a length of 5-10 mm
toward the anterior end of the cage body and at least one
perforated zone positioned upon the outer surface of the cage body
so as to be juxtaposed one of the bone structures upon
implantation.
2. The cage according to claim 1, wherein the preselected pattern
further includes at least a second non-perforated zone extending
from the first zone further toward the anterior end of the cage
body on a lateral side of the cage body.
3. The cage according to claim 1, wherein the preselected pattern
further includes: second and third non-perforated zones on the
lateral sides of the cage extending in opposing relation from the
first zone further toward the anterior end; and two opposed
perforated zones oriented so that upon insertion the perforated
zones adjacent the bone structures to be fused.
4. An interbody spine fusion cage for promoting fusion between
adjacent bone structures, comprising: a cage body having a
posterior end and an anterior end and defining an internal cavity,
the cage body further having an outer surface and a plurality of
radial apertures extending through the outer surface in
communication with the internal cavity; a non-perforated end
closure at each end of said cage body, at least one of the end
closures being movable so as to provide access to the internal
cavity; and wherein the movable end closure has at least one
aperture occluding surface extending therefrom, the surface being
suitable for introduction into the internal cavity to establish a
desired pattern of occluded apertures.
5. The cage according to claim 4, further comprising: a second cage
body having a posterior end and an anterior end and being disposed
within the internal cavity of the other cage body and so positioned
as to form an annulus therebetween, the outer surface of the second
cage body having a plurality of radial apertures extending
therethrough so as to establish communication with the annulus; and
wherein the occluding surface of the movable end closure being
suitable for introduction into the annulus to establish a desired
pattern of occluded apertures.
6. End closure means for effecting the closure of the posterior end
of a fusion cage while establishing a desired occlusion pattern of
apertures in the wall of the fusion cage which comprises: a first
sealing member to effect the closure of the posterior end of the
internal cavity of said fusion cage; and at least one occluding
surface extending from the sealing member and essentially parallel
to the longitudinal axis of the fusion cage so as to establish a
predetermined pattern of occlusion of the apertures in the wall of
the fusion cage.
7. The end closure means according to claim 6, further comprising a
pair of opposed occluding surfaces so spaced as to occlude
laterally positioned apertures along the wall of the fusion cage.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field
[0002] This invention is directed to improved devices for
facilitating the fusion of vertebral bone structure, which devices
can be inserted either anteriorly or posteriorly into the
spine.
[0003] 2. Background
[0004] Chronic back problems cause pain and disability for a large
segment of the population. In many cases, such problems are
attributable to relative movement between vertebrae in the spine.
Spinal surgery includes procedures to stabilize adjacent vertebrae.
Common stabilization methods often involve fusing adjacent
vertebrae together.
[0005] Fusion techniques include removing disc material which
separates the vertebrae and impacting bone into the disc area. The
impacted bone fuses with the bone material of the two adjacent
vertebrae to thereby fuse the vertebrae together. In a further
advance in the art, spinal implants have been developed to increase
the probability of a successful fusion. Such devices generally
comprise a hollow cylindrical cage into which bone growth inducing
substances, such as bone chips or bone slurry, may be placed. The
cage wall has holes extending radially therethrough, typically
throughout the entire cage surface. The combination of the cage and
bone growth inducing substance facilitates arthrodesis between the
adjacent vertebral bone structures. Fusion cages in both a threaded
and non-threaded form have come into wide use in the last several
years. Such cages are inserted either anteriorly or posteriorly
into the spine in the intervertebral disc space to fuse the
adjacent vertebrae as aforedescribed and to decompress neural
elements.
[0006] With the continued development of techniques for achieving
spinal fusion through the use of spine fusion cages, there has also
been developed new materials to augment the fusion process. In the
older method, the patient's own bone, or cadaver bone, was used in
the cage to promote bony fusion. Newer biologic materials have now
been discovered that greatly augment the fusion process and in some
cases make using the patient's own bone unnecessary.
[0007] However, with the utilization of the newer biologic
materials there has arisen a significant problem. When bone growth
accelerants, such as bone morphogenic proteins, are used in cages
of existing design there is risk of inducing the growth of bone
around and into sensitive neural tissues. This is especially the
case when a posterior approach is utilized to implant the fusion
cage, as bony overgrowth in this direction may impinge on spinal
nerve roots. It accordingly should be appreciated that there is a
need for a fusion cage designed to be used with such biologic
materials to prevent bone growth from impinging on neural
tissue.
[0008] It is thus an object of the present invention to provide an
improved spine fusion cage which prevents the overgrowth of bone
around and into sensitive areas of neural tissue.
[0009] It is another object of the invention to provide a spine
fusion cage having a feature whereby a surgeon may selectively
occlude holes in the cage wall to prevent bone growth
therethrough.
[0010] A further object of this invention is to provide a novel
closure for spine fusion cages which can be used with presently
available fusion cages in preventing bone growth into undesirable
areas.
SUMMARY OF THE INVENTION
[0011] In accordance with one embodiment of the present invention
there is provided a novel spine fusion cage which can be inserted
into an intervertebral disc space using either a posterior or
anterior approach and which prevents overgrowth of bone around or
into neural tissue. Growth of bone into sensitive areas is
prohibited by providing the cage with various zones wherein the
cage wall is either perforated or non-perforated. A cage body is
provided having a posterior end and an anterior end and defining an
internal cavity and a longitudinal axis. The cage body has an outer
surface and a plurality of radial apertures extending through the
outer surface in communication with the internal cavity in a
preselected pattern. Preferably, there is a first non-perforated
zone extending from the posterior end of the cage a preselected
length toward its anterior end, second and third non-perforated
zones on the lateral sides of the cage extending in opposing
relation from the first zone further toward the anterior end, and
two opposed perforated zones oriented so that upon insertion of the
device the perforated zones will be adjacent the vertebral bodies
to be fused to allow bone growth across the vertebral interspace.
Each end of the cage is provided with a non-perforated closure. In
this manner bone growth is prevented in areas adjacent the
non-perforated zones when the fusion cage is in place.
[0012] In accordance with another embodiment of the present
invention there is provided a novel spine fusion cage which
provides for the selective occlusion of apertures in the cage wall
so as to prevent the growth of bone in undesired directions. As an
example, there is provided an inventive cage having outer and inner
cage elements. An outer cage body having a posterior end and an
anterior end defines an internal cavity. A plurality of radial
apertures extend through the outer surface of the outer cage body
to communicate with the internal cavity in a pattern covering a
substantial portion of the outer surface of the cage body. An inner
cage body is disposed within the internal cavity of the outer cage
body and is positioned as to form an annulus between the inner wall
surface of the outer cage body and the outer wall surface of the
inner cage body. The inner cage body likewise has a plurality of
radial apertures extending through its outer surface so as to
establish communication with the annulus and the outer surface of
the outer cage. An end closure means having occluding surfaces
suitable for introduction into the annulus between the outer and
inner cages serves to establish one or more desired zones or
patterns of occluded apertures amongst the plurality of apertures
in the outer cage body, thereby obstructing bone growth in
undesired directions.
[0013] In still another embodiment there is provided an end closure
means for effecting the closure of the posterior end of a fusion
cage while establishing a desired occlusion pattern of apertures in
the wall of the fusion cage. The closure means comprises a
non-perforated sealing member to effect the closure of the
posterior end of the internal cavity of the fusion cage and one or
more occluding surfaces extending from the sealing member
essentially parallel to the longitudinal axis of the fusion cage so
as to establish one or more desired zones or patterns of occluded
apertures amongst the plurality of apertures in the cage body.
[0014] A better understanding of the present invention, its several
aspects, and its advantages will become apparent to those skilled
in the art from the following detailed description, taken in
conjunction with the attached drawings, wherein there is shown and
described the preferred embodiments of the invention, simply by way
of illustration of the best mode contemplated for carrying out the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 anatomically illustrates a bilateral posterior
insertion of two inventive cylindrical spine fusion cages to
achieve fusion across the L5/S1 disc space.
[0016] FIG. 2 is an exploded perspective view of an embodiment of
an inventive cage having preselected perforated and non-perforated
zones on its outer surface.
[0017] FIG. 3 is a perspective view taken along line 3-3 of FIG.
2.
[0018] FIG. 4 is a sectional view taken along line 4-4 of FIG.
2.
[0019] FIG. 5 is perspective view of an embodiment of an inventive
cage having outer and inner cage elements.
[0020] FIG. 6 is a sectional view taken along line 6-6 of FIG.
5.
[0021] FIG. 7 is a perspective view of an end closure for use in
connection with the cage of FIG. 5.
[0022] FIG. 8 a top sectional view of the cage of FIG. 5 including
the end closure of FIG. 7.
[0023] FIG. 9 is an exploded side view of a conventional fusion
cage modified to utilize an inventive end closure means to
selectively occlude certain apertures in the outer surface of the
cage.
[0024] FIG. 10 depicts the partial insertion of the inventive
closure means into the cage of FIG. 9.
[0025] FIG. 11 depicts the full insertion of the inventive closure
means into the cage of FIG. 9.
[0026] FIG. 12 is top sectional view of a modified conventional
cage including an inventive end closure means.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] Several types of conventional spine fusion cages have been
designed, such as those described by Bagby, Brantigan and Ray,
respectively, in Athrodesis by the Distraction-Compression Method
Using a Stainless Steel Implant, Orthopaedics 1988, Vol. 11:931-4;
A Carbon Fibre Implant to Aid Interbody Lumbar Fusion, Spine 1991,
16 (Suppl):S277-82 (with Steffee and Geiger); and Threaded Titanium
Cages for Lumbar Interbody Fusions, Spine 1997, 22:667-80; and as
described in the patent art, for example, in U.S. Pat. Nos.
4,501,269; 5,055,104; 5,571,192; 5,702,449; 5,876,457; 5,906,616;
5,976,187; 5,980,522; 6,010,502; 6,015,436; and 6,039,762. Each of
the foregoing publications and patents is incorporated herein by
reference.
[0028] Such devices provide for a relatively simple and effective
technique for implementing lumbar interbody fusion by correcting
any existing mechanical deformity of the spine while providing
stability and a good environment until successful arthrodesis is
obtained. These cage devices are hollow and are positioned between
the articulating vertebrae, where they support and immobilize the
joint as well as contain the growth of the bone graft that is
packed into the internal cavity of the device.
[0029] Anterior lumbar interbody fusion (ALIF) and posterior lumbar
interbody fusion (PLIF) are two commonly adopted approaches for
grafted lumbar interbody fusion with augmentation via a spine
fusion cage. ALIF is performed through a retroperitoneal or
transperitoneal approach with extensive discectomy followed by the
placement of one or more cages in the vertebral interspace. In
PLIF, partial or complete laminectomy and facetectomy is followed
by posterior discectomy and the placement of one or more cages in
the vertebral interspace. FIG. 1 is illustrative of a bilateral
posterior insertion of two inventive cylindrical spine fusion cages
20 to achieve fusion across the L5/S1 disc space. The cages 20 are
secured far enough apart from each other (by a few millimeters) to
avoid contact and potential back-threading. It should be understood
that the fusion cages of this invention can be installed in their
operative positions via either the anterior or posterior
approaches; however, the posterior approach is the most dangerous
in regards for bony overgrowth impinging on neural tissue
particularly when the cage is used along with bone growth inducing
materials.
[0030] The inventive cages 20 promote bony fusion by holding
adjacent levels immobile and by allowing bone to grow only into the
vertebral bodies an away from the spinal canal and nerve roots.
Designs that do not control direction of growth are undesirable for
use with biologic bone growth accelerants to the extent unchecked
bony overgrowth may impinge upon neural tissues. Through the
present invention there are provided designs for spine fusion cages
which prevent bone growth around and into sensitive areas of neural
tissue.
[0031] Referring now to FIGS. 2-4, and in accordance with one
embodiment of the present invention, there is provided an inventive
spine fusion cage 20 wherein growth of bone into sensitive areas is
prohibited by providing the cage with various zones or areas
wherein the cage wall is either perforated or non-perforated. A
cage body 22 is provided having a posterior end 24 and an anterior
end 26 and defining an internal cavity 28 and a longitudinal axis
30. The cage body 22 is typically between 20-25 mm in length and
may be of a variety of diameters (if cylindrical) and heights. The
cage body 22 has an outer surface 32 and a plurality of radial
apertures 34 extending through the outer surface 32 in
communication with the internal cavity 28 in a preselected pattern.
Preferably, there is a first non-perforated zone 36 extending from
the posterior end 24 of the cage body 22 a preselected length,
preferably 5-10 mm, toward its anterior end 26, second and third
non-perforated zones 38, 40 on the lateral sides of the cage body
22 extending in opposing relation from the first zone 36 further
toward the anterior end 26, and two opposed perforated zones 42, 44
oriented cephalad (or to the superior side) and caudad (or to the
inferior side) so that upon insertion of the device the perforated
zones 42, 44 will be adjacent the vertebral bodies to be fused to
allow bone growth across the vertebral interspace. Each end 24, 26
of the cage body 22 is provided with a non-perforated closure. In
the illustrated embodiment, the anterior end 26 is closed by an
integral non-perforated end wall 46, while there is provided a
removable end cap 48 securable, by threaded attachment, friction
fit or otherwise, to the posterior end 24 of the cage body 22. The
end cap 48 may be provided with a recess 50 for receiving an
insertion tool, for example if the end cap is made to threadably
connect to the cage body, and there is preferably provided on the
top of the end cap 48 a line score 52 for aiding proper orientation
of the device in the vertebral interspace.
[0032] The cage body 22 may be provided with threads 54,
projections, ridges, protrusions, barbs, spurs or other insertion
means to aid in placement of the cage within the interbody area.
The anterior end 26 can be rounded in order to facilitate the
insertion of the cage 20 relative to one or more bone structures.
The cage 20 may be made of surgical steel, titanium or other
acceptable implantable materials. Typically, the cage 20 is
countersunk into the vertebral interspace with the end cap 48 in
place by using an insertion tool (not shown) to screw the cage 20
into position. Once the cage is properly aligned, the end cap 48 is
removed so that bone growth inducing material can be packed into
the internal cavity 28 of the cage body 22, whereupon the end cap
48 is tightly replaced.
[0033] As can now be appreciated, the inventive cage 20 prevents
bone growth into areas adjacent the non-perforated zones when the
fusion cage is in place. Because the posterior 5-10 mm of the cage
is non-perforated, including, importantly, the end cap, bony
overgrowth is inhibited in areas immediately adjacent the
posteriorly located neural tissues. In similar fashion, lateral
overgrowth of bone is impeded by the second and third
non-perforated zones. Desired growth through the vertebral
interspace, however, is facilitated via the perforated zones.
[0034] It should be understood to be within the ordinary skill of
one in the art to modify the placement of the various perforated
and non-perforated zones as warranted by orthopaedic considerations
to achieve desired bone growth and preclude unwanted bone growth.
It is also within the ordinary skill of one in the art to modify
the aforedescribed device for anterior insertion procedures by
providing a removable end cap on the anterior end of the cage body
and reversing the thread direction on the outside surface of the
cage body.
[0035] As mentioned above, it is also advantageous for a surgeon to
have the ability to selectively occlude apertures in the cage wall
to prevent bone growth in undesired directions. Now referring to
FIGS. 5-8, to achieve this object, and in accordance with another
embodiment of the present invention, there is provided a spine
fusion cage 120 having an outer cage body 122 with a posterior end
124 and an anterior end 126 and defining an internal cavity 128 and
a longitudinal axis 130. The outer cage body 122 has an outer
surface 132 and a plurality of radial apertures 134 extending
through the outer surface 132 in communication with the internal
cavity 128 in a pattern covering a substantial portion of the outer
surface 132 of the cage body 122. An inner cage body 136 into which
is placed bone growth inducing substances is disposed within the
internal cavity 128 of the outer cage body 122 and is positioned as
to form an annulus 138 between the inner wall surface 140 of the
outer cage body 122 and the outer wall surface 142 of the inner
cage body 136. The inner cage body 136 likewise has a plurality of
radial apertures 144 extending through its outer surface 142 so as
to establish communication with the annulus 138 and the outer
surface 132 of the outer cage body 122. A solid end closure 146
having opposed occluding surfaces 148, 150 suitable for
introduction into the annulus 138 serves to establish one or more
desired zones or patterns of occluded apertures amongst the
plurality of apertures in the outer cage body 122, thereby
obstructing bone growth in undesired directions.
[0036] More specifically, as shown in FIG. 7 end closure 146 is
comprised of a non-perforated cap or closure means 152 having
occluding surfaces 148 and 150 extending therefrom. Such surfaces
may be of sufficient length to extend to the bottom of the cage
member 120 as shown in FIG. 5 or may be of a more limited length so
as to occlude only a portion of the apertures 134 in the outer cage
body 122. The end closure 146 may be constructed so as to provide a
top circumferential crown portion 154 and between the occluding
surfaces 148, 150 a shoulder 156 which may engage a rib means 158,
160 as shown in FIG. 8 to act as a longitudinal stop and to limit
the degree of rotation which can be made by occluding surfaces 148,
150 so as to maintain the selected occlusion pattern. When
positioned within the annulus 138 of the fusion cage 120, the
occluding surfaces 148, 150 serve to close openings in the
posterior end of the cage 120 as well as to occlude openings which
are in a lateral position so as to effect bone growth through the
apertures in the caudal and cephalad directions when placed in the
desired position between two vertebrae. Various interchangeable
forms of end closures may be provided, for example having
differently shaped and dimensioned occluding surfaces, so as to
provide for the surgeon a selection which meets objectives
according to various orthopaedic exigencies. It is also within the
scope of this invention that the shape and dimensions of the
occluding surfaces may be modifiable by the surgeon, such as if the
occluding surfaces comprise a surgical plastic adapted to be cut or
trimmed to achieve a desired configuration. In this manner, a cage
possessing a full pattern of apertures can be used as a "universal"
cage in combination with one of a wide selection of end closures or
a modifiable end closure to achieve any desired patterned of
perforation.
[0037] The end closure 146 can be threaded or otherwise designed to
effect the closure of the posterior end of the cage 120 and may be
provided with securing means such as square or hex-shaped recess
162 which can be used with a socket wrench to tightly position the
end closure 146 in the posterior end of the fusion cage 120. In
complementary fashion, threads may be provided at the posterior end
of the cage 120 to receive a threaded end closure 146 or it can be
so adapted that the end closure 146, when not threaded, can be
simply snapped into place to effect the desired closing of the
fusion cage 120.
[0038] A thread 164 may be provided as part of the outer surface
132 of the fusion cage 120. Such a thread can be replaced with a
plurality of discrete threads or a plurality of projections,
ridges, protrusions, barbs or spurs and be within the spirit and
scope of the invention.
[0039] In assembly of the fusion cage of this embodiment of the
invention, following introduction of the selected biologic material
into the internal cavity 128 within the inner cage body 136, the
annulus 138 remains clear so as to easily accept end closure 146
within the annulus 138 while the biologic materials are retained in
the internal cavity 128. Through the dimensioning, shaping and
rotation of occluding surfaces 148, 150 there is achieved an
occlusion of apertures so as to define the desired pattern of
apertures through which bone growth is to be permitted.
[0040] In keeping with the teachings of the present invention,
there is further provided a novel closure for conventional spine
fusion cages which can be used with little or no modification to
presently available fusion cages in preventing bone growth into
undesirable areas. This embodiment involves providing a means for
the occlusion of selected apertures in currently available fusion
cages, such as to those commonly referred to as Brantigan, BAK and
Ray cages, so that bone growth is directed only toward the
vertebral bodies and away from the spinal canal and nerve
roots.
[0041] Making reference now to FIGS. 9-11, there is illustrated an
end closure 220 for effecting the closure of the posterior end 222
of a conventional fusion cage body 224 while establishing a desired
occlusion pattern of apertures in the wall of the cage body 224,
which cage possesses apertures 226 substantially entirely
thereabout. The end closure 220 comprises a non-perforated sealing
member 228 to effect the closure of the posterior end 222 of the
cage body 224 and one or more occluding surfaces 230, 231 extending
from the sealing member 228 essentially parallel to the
longitudinal axis 230 of the cage body 224 so as to establish one
or more desired zones or patterns of occluded apertures amongst the
plurality of apertures in the cage body 224. Reference is made to
the disclosure provided above with respect to the aforedescribed
end closure 146, which disclosure is equally applicable to end
closure 220 and further recitation is believed unnecessary. Suffice
it to say that the prior described end closure 146 may be made
adaptable to conventional fusion cages so as to achieve the
objectives of the present invention.
[0042] As depicted in FIG. 12, if desired the conventional type of
fusion cage can be so modified as to provide ribs 232, 234 in
association with the inner surface of the posterior end of the cage
according to the teachings herein. FIG. 12 provides a top view of
the fusion cage of FIG. 11 along the line 12-12 which shows the
placement of the ribs 232 and 234 to accommodate occluding surfaces
230, 231 of the end closure 220.
[0043] While the invention has been described with a certain degree
of particularity, it is understood that the invention is not
limited to the embodiment(s) set for herein for purposes of
exemplification, but is to be limited only by the scope of the
attached claim or claims, including the full range of equivalency
to which each element thereof is entitled.
* * * * *