U.S. patent application number 10/212506 was filed with the patent office on 2002-12-19 for anterior lumbar interbody fusion cage with locking plate.
Invention is credited to Fraser, Robert.
Application Number | 20020193880 10/212506 |
Document ID | / |
Family ID | 23782880 |
Filed Date | 2002-12-19 |
United States Patent
Application |
20020193880 |
Kind Code |
A1 |
Fraser, Robert |
December 19, 2002 |
Anterior lumbar interbody fusion cage with locking plate
Abstract
A spinal fixation assembly includes a fusion cage to which a
plate is mated. The plate is configured to receive, retain and
orient bone screws.
Inventors: |
Fraser, Robert; (Myrtle
Bank, AU) |
Correspondence
Address: |
NUTTER MCCLENNEN & FISH LLP
WORLD TRADE CENTER WEST
155 SEAPORT BOULEVARD
BOSTON
MA
02210-2604
US
|
Family ID: |
23782880 |
Appl. No.: |
10/212506 |
Filed: |
August 5, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10212506 |
Aug 5, 2002 |
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09449105 |
Nov 24, 1999 |
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6432106 |
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Current U.S.
Class: |
623/17.11 |
Current CPC
Class: |
A61F 2/4465 20130101;
A61B 17/80 20130101; A61F 2/30965 20130101; A61F 2002/30604
20130101; A61F 2002/30787 20130101; A61F 2002/3023 20130101; A61F
2002/30841 20130101; A61F 2002/30892 20130101; A61F 2002/30112
20130101; A61F 2230/0069 20130101; A61F 2230/0004 20130101; A61F
2002/30187 20130101; A61F 2002/30398 20130101; A61F 2002/30774
20130101; A61B 17/86 20130101; A61F 2002/30845 20130101; A61F
2/30771 20130101; A61F 2220/0025 20130101; A61F 2/442 20130101;
A61F 2002/2835 20130101; A61B 17/7059 20130101; A61F 2002/30593
20130101; A61F 2002/30387 20130101; A61F 2002/30329 20130101; A61F
2002/30578 20130101; A61F 2310/00023 20130101; A61F 2/4611
20130101; A61F 2230/0034 20130101 |
Class at
Publication: |
623/17.11 |
International
Class: |
A61F 002/44 |
Claims
What is claimed is:
1. A spinal fixation assembly comprising: a fusion cage having a
posterior face, an anterior face, a superior face, and an inferior
face; a plate mated to the fusion cage, the plate defining an
aperture for receiving a bone screw; and a bone screw having a head
and a shank, the shank being dimensioned to pass through the
aperture in the plate, and the head being dimensioned to engage the
plate to inhibit passage of the head through the aperture in the
plate.
2. The spinal fixation assembly of claim 1, wherein the plate is
mated to the anterior face of the fusion cage.
3. The spinal fixation assembly of claim 1, wherein the plate is
slidably engaged with the fusion cage so as to be movable in a
superior/inferior direction.
4. The spinal fixation assembly of claim 1, wherein the plate and
the fusion cage are joined with a mortise and a tenon.
5. The spinal fixation assembly of claim 1, wherein the fusion cage
includes a medial plane that separates the inferior face from the
superior face to define an inferior side and a superior side, and
wherein the plate defines a first aperture on the inferior side of
the fusion cage and a second aperture on the superior side of the
fusion cage.
6. The spinal fixation assembly of claim 5, wherein the plate
further includes a first tab that defines the first aperture and a
second tab that defines the second aperture.
7. The spinal fixation assembly of claim 6, wherein the first tab
and the second tab are flexible.
8. The spinal fixation assembly of claim 6, wherein one of the
first tab and the second tab is angled with respect to the plate at
an angle between 15.degree. and 60.degree..
9. The spinal fixation assembly of claim 6, wherein one of the
first tab and the second tab is angled with respect to the plate at
an angle of about 20.degree..
10. The spinal fixation assembly of claim 1, wherein one of the
superior face and the inferior face is convex.
11. The spinal fixation assembly of claim 1, wherein the fusion
cage is thicker at the anterior face than at the posterior
face.
12. The spinal fixation assembly of claim 11, wherein the fusion
cage tapers at about 10.degree. from the anterior face to the
posterior face.
13. The spinal fixation assembly of claim 11, wherein the fusion
cage defines an annulus with a first transverse element and a
second transverse element.
14. The spinal fixation assembly of claim 13, wherein the first and
second transverse elements extend from the anterior face to the
posterior face.
15. The spinal fixation assembly of claim 14, wherein the first
transverse element is substantially parallel to the second
transverse element.
16. The spinal fixation assembly of claim 5, wherein the fusion
cage defines a bore centered on the medial plane and open at the
anterior face.
17. The spinal fixation assembly of claim 16, wherein the plate
defines a bore therethrough that is aligned with the bore defined
by the fusion cage.
18. The spinal fixation assembly of claim 1, further including a
plurality of fins extending outward from the fusion cage on one of
the superior face and the anterior face.
19. The spinal fixation assembly of claim 1, further including a
notch on one of the superior face and inferior face that extends
from the anterior face toward the posterior face.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 09/449,105, filed on Nov. 24, 1999, entitled
"Anterior Lumbar Interbody Fusion Cage With Locking Plate," which
is expressly incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to medical devices, and more
particularly to an implantable structure for promoting fusion of
adjacent vertebral bodies.
BACKGROUND OF THE INVENTION
[0003] Advancing age, as well as injury, can lead to changes in the
bones, disks, joints, and ligaments of the spine producing pain
from nerve root compression. Under certain circumstances,
alleviation of pain can be provided by performing a spinal fusion.
This is a procedure that involves joining two or more adjacent
vertebrae so that they no longer are able to move relative to each
other.
[0004] Many prosthetic devices are known for promoting fusion of
the spinal vertebrae, and the devices can be classified, in part,
based upon the approach to the spine that will be taken by the
surgeon (anterior, posterior, lateral, etc.). None of the known
devices is completely satisfactory, and improvements are
desirable.
SUMMARY OF THE INVENTION
[0005] The present invention improves upon known spinal fusion
devices, especially those devices intended for an anterior approach
to the spine. In an exemplary embodiment, a spinal fixation
assembly includes a fusion cage to which a plate is mated. The
plate is configured to receive, retain and orient bone screws,
thereby holding the fusion cage and adjacent vertebral bodies in a
stable relationship to promote fusion.
[0006] Additional features of the assembly can include a plate
mated to the fusion cage so as to be slidable therewith, and
joining them with a mortise and a tenon. The plate can include
extensions or tabs through which bone screws are passed and
retained on one or both of the superior and inferior sides of the
fusion cage. The tabs can be angled to orient the screws as
desired.
[0007] The fusion cage can include convex superior and inferior
surfaces, and it can be tapered from the anterior face to the
posterior face. Both the fusion cage and the plate can include
insertion tool guide and engagement features, such as bores and
notches. Fins can be provided at one or more points on the inferior
and superior faces of the fusion cage.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The invention will be more fully understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0009] FIG. 1 is a plan view of a fusion cage in accordance with
the present invention;
[0010] FIG. 2 is a view of the anterior face of the fusion cage of
FIG. 1;
[0011] FIG. 3 is a side view of the fusion cage of FIG. 1 with bone
screws;
[0012] FIG. 4 is a plan view of an embodiment of a fusion cage in
accordance with the invention having fins on the superior face of
the cage;
[0013] FIG. 5 is a view of the anterior face of the fusion cage of
FIG. 4;
[0014] FIG. 6 is a side view of the fusion cage of FIG. 4;
[0015] FIG. 7 illustrates adjacent vertebral bodies being separated
in preparation for insertion of a fusion cage;
[0016] FIG. 8 depicts a portion of the spine following placement of
the fusion cage of FIG. 1;
[0017] FIG. 9 depicts a portion of the spine following placement of
the fusion cage of FIG. 4;
[0018] FIG. 10 is a side elevation view of a bone engagement fin in
accordance with the invention; and
[0019] FIG. 11 is a top view of an exemplary bone engagement
fin.
DETAILED DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a plan view of a fusion cage in accordance with
the present invention. The cage includes a body 10 that
approximates the shape and size of the annulus portion of a disk
which normally separates two vertebral bodies. The body 10 includes
faces that are named in relation to their orientation with respect
to a patient. Specifically, the body 10 includes an anterior face
12, a posterior face 14, a superior face 16, and an inferior face
18 (visible in FIG. 2). Except where specifically noted, as used
herein, "face" is not intended to connote the outwardmost surface
("face surface" is used) or a specific geometry (e.g., planar).
Rather, "face" refers to a general region on different sides of the
body 10. A carbon fiber composite or other radiolucent material is
well suited for fabrication of the body.
[0021] The cage further includes a plate 20 that is matable with
the body 10. Titanium or carbon fiber composites are suitable
materials for the plate 20. As shown in FIGS. 1, 2, and 3, the
plate 20 is mated with the anterior face 12 of the body 10 for an
anterior approach to the spine. However, other embodiments of the
fusion cage are configured for mating the plate 20 to the body 10
at locations other than the anterior face 12 as required for an
anterolateral or lateral approach to the spine.
[0022] Although the plate 20 can be bonded firmly to the body 10 so
that the plate and body cannot move with respect to each other,
they can also be mated to allow movement with respect to each
other. For example, in the illustrated embodiment, the plate 20
includes a tenon 24 that is disposed within a mortise 26 defined by
the body 10, wherein the tenon can slide in a superior/inferior
direction within the mortise.
[0023] Continuing to refer to FIG. 1, the fusion cage can also be
provided with first and second transverse elements 28 and 30,
respectively, that join the posterior face 14 to the anterior face
12. The transverse elements 28 and 30 enhance the structural
integrity of the body 10 and provide additional load bearing
surface. The transverse elements 28 and 30 can also be configured
to provide a guide path for a fusion cage insertion tool. For
example, the guide path in the illustrated embodiment is between
the transverse elements in the space numbered 32. The guide path
can further include a notch or depression 34 in one or both of the
superior face 16 or inferior face 18 of the body or defined by the
plate 20 as shown in FIG. 2. In an exemplary embodiment, the guide
path is about 8 mm wide and recessed about 1 mm to 2 mm below the
superior/inferior face surface.
[0024] Referring now to FIG. 2, an embodiment of the plate 20 is
shown mated to the anterior face 12. In this illustration, four
bone screw holes 36, 38, 40 and 42 are visible as is a guide bore
or hole 44. The guide hole 44 is aligned with a bore 46 (shown in
FIG. 1) in the body 10. Both the guide hole 44 and the bore 46 are
configured to receive a portion of an insertion tool (not shown),
and both the guide hole and bore can be provided with tool
engagement features such as threads. As shown, the bone screw holes
36, 38, 40 and 42 can be disposed in or defined by plate extensions
or tabs 36', 38', 40' and 42', wherein the tabs and the remainder
of the plate 20 can all lie in the same plane, or one or more of
the tabs can be angled with respect to the remainder of the plate
or one or more of the other tabs.
[0025] Turning to FIG. 3, bone screws 46 and 48, each having a head
and a shank are shown disposed through the holes in tabs 40' and
38', respectively, such that the head of each screw engages the
respective tab to inhibit passage of the head through the aperture
in the tab. In an exemplary embodiment, the screws are about 3.6 mm
in diameter and about 22 mm in length. The screws are of the
"locking" type, so that they cannot "back out" of the holes in the
plate.
[0026] Continuing to refer to FIG. 3, tabs 38' and 40' are shown
angled with respect to the remainder of the plate 20 so that screws
46 and 48 are angled with respect to the medial plane "P" of the
body 10. The angle formed by the tab(s) and plate, as well as by
the screw(s) and medial plane, is designated as ".alpha." and is
determined by a particular situation and a patient's anatomy.
Although the angle ".alpha." can range from 15.degree. to
60.degree., for most applications the angle ".alpha." is about
20.degree.. However, in other embodiments, the tabs are flexible or
readily bent with respect to the remainder of the plate 20.
[0027] Also shown in FIG. 3 are other advantageous features of the
fusion cage, such as flat to slightly convex inferior and superior
face surfaces 18 and 16, respectively, and a slightly tapered
(about 10.degree.) or wedge profile, wherein the body 10 is thicker
at the anterior face 12 than at the posterior face 14.
[0028] Referring now to FIG. 4, a fusion cage is shown with sharp
fins 50 on the superior face of the transverse elements 28 and 30.
As shown in FIGS. 5 and 6, fins 50 can also be provided on the
inferior face of the transverse elements 28 and 30. Exemplary fins
are about 1 mm to 2 mm in height. FIGS. 10 and 11 illustrate
exemplary fins in greater detail. As shown in FIG. 10, an exemplary
fin 50 has a first end 68 and a second end 70, and as illustrated
in FIG. 4, each fin is oriented in a generally anterior/posterior
so that the first end is closer to the posterior face 14 of the
fusion cage and the second end is closer to the anterior face 12.
One or more fins can be tapered so that the second end 70 is taller
than the first end 68 which merges flush with the face of the cage
on which it is formed or mounted. Also, as shown in FIGS. 4 and 11,
the second end 70 can be wider than the first end 68 which comes to
a point.
[0029] Continuing to refer to FIG. 10, a posterior face 72 can be
angled during manufacture to provide a range of fin configurations.
When an angle defined by the posterior face 72 and a line 74 formed
by the intersection of opposing fin sides 76 and 78 is small (e.g.,
.alpha..sub.1) a top fin portion 80 forms a "spike" that readily
will dig into bone if the fin is moved toward the second end 70.
If, as shown by dotted lines in FIG. 10, and from above in FIG. 11,
the angle defined by the posterior face 72 and a line 74 formed by
the intersection of opposing fin sides 76 and 78 is larger (e.g.,
.alpha..sub.2) a top fin portion 80 forms a "spike" that readily
will dig into bone when the fin and bone are pressed toward each,
as when the fusion cage is compressed between two vertebral
bodies.
[0030] The fusion cage of FIGS. 4, 5 and 6 does not include a plate
20, but it does include a bore 46 for engaging an insertion tool,
as well as a guide path or groove. Additional advantages of the
present invention are evident when the invention is viewed in
context.
[0031] FIG. 7 is a lateral view of adjacent vertebral bodies 52 and
54 being distracted or separated with a surgical implement 56, of
which only the distal portion is visible, in preparation for
insertion of a fusion cage in accordance with the invention, the
disk having been removed and the implant area prepared.
[0032] FIG. 8 depicts the fusion cage described above with respect
to FIGS. 1, 2 and 3 after it has been implanted. In this view,
portions of the vertebral bodies are shown cut-away to illustrate
the penetration of the bone screws 58 and 60 into the bodies. It is
important to note that screw heads 62 and 64 are flush or sub-flush
with the anterior face surface 66 of the fusion cage, thus
minimizing the likelihood that major blood vessels running along
the spine will be injured.
[0033] FIG. 9 illustrates the fusion cage described above with
respect to FIGS. 4, 5 and 6 after it has been implanted. In this
view, portions of the vertebral bodies are shown cut-away to
illustrate the penetration of the fins 50 into the vertebral bodies
52 and 54. It should be noted that because the fins 50 can be
tapered both in height and width. Thus, the tapering, in
combination with the anterior/posterior orientation of the fins,
allows the fusion cage to be inserted between the vertebral bodies
with minimal resistance due to the fins, thereby minimizing
necessary distraction distance between vertebral bodies. Also, the
raised second end of the fins significantly inhibits anterior
movement of the fusion cage once it has been positioned between
vertebral bodies, as it "digs-in" to the vertebral bone if the
fusion cage is urged in an anterior direction. In other words, the
fins enhance purchas and provide expulsion protection.
[0034] Prior to inserting a fusion cage between vertebral bodies,
the space bounded by the body 10 and transverse elements 28 and 30
(if included) can be filled with autograft or allograft bone, or
demineralized bone matrix (DBM) to promote fusion. Over a period of
about three months the vertebral bodies fuse.
[0035] As should be readily apparent from the preceding
description, the present invention provides many advantages. For
example, the fusion cage is sufficiently broad and thick so that
only a single cage is needed to replace an excised disk. The
profile and slightly bowed or convex superior and inferior surfaces
of the fusion cage body closely approximate the shape of a natural
disk and provide an excellent, stable, load-bearing surface. The
plate, when included, ensures that the body will not become
dislodged from the spine, yet is readily accessible with an
anterior approach. Further, the plate allows bone screws to be
deeply embedded into the vertebral bodies without piercing or
otherwise damaging the hard, load-bearing, cortical bone. Also,
both the plate and the body include features that allow for
relatively easy manipulation and insertion with appropriately
configured surgical tools.
[0036] Of course, one skilled in the art will appreciate further
features and advantages of the invention based on the
above-described embodiments. Accordingly, the invention is not to
be limited by what has been particularly shown and described,
except as indicated by the appended claims. All publications and
references cited herein are expressly incorporated herein by
reference in their entirety.
* * * * *