U.S. patent application number 11/438383 was filed with the patent office on 2006-09-21 for method and apparatus for total disc replacements with oblique keels.
Invention is credited to Bret Ferree.
Application Number | 20060212121 11/438383 |
Document ID | / |
Family ID | 33493552 |
Filed Date | 2006-09-21 |
United States Patent
Application |
20060212121 |
Kind Code |
A1 |
Ferree; Bret |
September 21, 2006 |
Method and apparatus for total disc replacements with oblique
keels
Abstract
Artificial disc replacement (ADR) systems with intradiscal
components feature non anterior-posterior (A-P) or oblique-oriented
keels such that the great vessels do not require as much retraction
during insertion. The system may further include guides for
aligning the ADR prior to insertion, and for cutting an oblique
slot into a vertebral endplate to receive the keel. A screw adapted
to penetrate a vertebral body may be used in conjunction with the
keel. The screw and keel may converge, diverge or intersect. The
screw may further include a mechanism providing a locking
relationship with the keel. The system may further including a
guide to direct drill bits and screws through holes in the keel.
ADRs according to the invention may additionally, independently
include a non-symmetrical endplate shaped so as to decrease the
risk of injuring the great vessels. By virtue of the invention, a
second ADR may be installed at a second level having a keel
oriented differently from that of the ADR having an orientation
other than anterior-to-posterior.
Inventors: |
Ferree; Bret; (Cincinnati,
OH) |
Correspondence
Address: |
John G. Posa;Gifford, Krass, Groh, Sprinkle,
Anderson & Citkowski, P.C.
PO Box 7021
Troy
MI
48007-7021
US
|
Family ID: |
33493552 |
Appl. No.: |
11/438383 |
Filed: |
May 22, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10860920 |
Jun 4, 2004 |
7048766 |
|
|
11438383 |
May 22, 2006 |
|
|
|
60476522 |
Jun 6, 2003 |
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Current U.S.
Class: |
623/17.11 ;
623/17.15 |
Current CPC
Class: |
A61F 2/4611 20130101;
A61B 17/8605 20130101; A61F 2002/3008 20130101; A61F 2002/449
20130101; A61F 2002/30495 20130101; A61F 2002/30884 20130101; A61F
2250/0098 20130101; A61F 2/4425 20130101; A61B 2017/1602 20130101;
A61B 17/1757 20130101; A61B 17/1671 20130101; A61F 2002/30878
20130101; A61B 2090/034 20160201; A61F 2/442 20130101; A61F
2002/30578 20130101; A61F 2220/0025 20130101; A61F 2002/30485
20130101; A61B 17/15 20130101; A61F 2002/4629 20130101; A61B
17/8038 20130101 |
Class at
Publication: |
623/017.11 ;
623/017.15 |
International
Class: |
A61F 2/44 20060101
A61F002/44 |
Claims
1-11. (canceled)
12. An artificial disc replacement (ADR) system, comprising: an
intradiscal component having an anterior portion, a posterior
portion, and a keel adapted to penetrate a vertebral endplate, the
keel defining a plane having an orientation other than
anterior-to-posterior when the component is installed; and a screw
adapted to penetrate a vertebral body in a direction not parallel
to the plane of the keel.
13. The system of claim 1, wherein the screw penetrates at least a
portion of the keel.
14. The system of claim 1, wherein the screw is directed toward the
keel but does a not penetrate the keel.
15. The system of claim 1, wherein the screw has a central axis
which converges with the plane of the keel.
Description
REFERENCE TO RELATED APPLICATION
[0001] This application claims priority from U.S. Provisional
Patent Application Ser. No. 60/476,522, filed Jun. 6, 2003, the
entire content of which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] This invention relates generally to artificial disc
replacements (ADRs) and, in particular, to ADRs with oblique
keels.
BACKGROUND OF THE INVENTION
[0003] Eighty-five percent of the population will experience low
back pain at some point. Fortunately, the majority of people
recover from their back pain with a combination of benign neglect,
rest, exercise, medication, physical therapy, or chiropractic care.
A small percent of the population will suffer chronic low back
pain. The cost of treatment of patients with spinal disorders plus
the patient's lost productivity is estimated at 25 to 100 billion
dollars annually.
[0004] Seven cervical (neck), 12 thoracic, and 5 lumbar (low back)
vertebrae form the normal human spine. Intervertebral discs reside
between adjacent vertebra with two exceptions. First, the
articulation between the first two cervical vertebrae does not
contain a disc. Second, a disc lies between the last lumbar
vertebra and the sacrum (a portion of the pelvis).
[0005] The spine supports the body, and protects the spinal cord
and nerves. The vertebrae of the spine are also supported by
ligaments, tendons, and muscles which allow movement (flexion,
extension, lateral bending, and rotation). Motion between vertebrae
occurs through the disc and two facet joints. The disc lies in the
front or anterior portion of the spine. The facet joints lie
laterally on either side of the posterior portion of the spine.
[0006] The human intervertebral disc is an oval to kidney bean
shaped structure of variable size depending on the location in the
spine. The outer portion of the disc is known as the annulus
fibrosis. The annulus is formed of 10 to 60 fibrous bands. The
fibers in the bands alternate their direction of orientation by 30
degrees between each band. The orientation serves to control
vertebral motion (one half of the bands tighten to check motion
when the vertebra above or below the disc are turned in either
direction). The annulus contains the nucleus. The nucleus pulpous
serves to transmit and dampen axial loads. A high water content
(70-80 percent) assists the nucleus in this function. The water
content has a diurnal variation. The nucleus imbibes water while a
person lies recumbent. Activity squeezes fluid from the disc.
Nuclear material removed from the body and placed into water will
imbibe water swelling to several times its normal size. The nucleus
comprises roughly 50 percent of the entire disc. The nucleus
contains cells (chondrocytes and fibrocytes) and proteoglycans
(chondroitin sulfate and keratin sulfate). The cell density in the
nucleus is on the order of 4,000 cells per micro liter.
[0007] Interestingly, the adult disc is the largest avascular
structure in the human body. Given the lack of vascularity, the
nucleus is not exposed to the body's immune system. Most cells in
the nucleus obtain their nutrition and fluid exchange through
diffusion from small blood vessels in adjacent vertebra.
[0008] The disc changes with aging. As a person ages the water
content of the disc falls from approximately 85 percent at birth to
70 percent in the elderly. The ratio of chondroitin sulfate to
keratin sulfate decreases with age. The ratio of chondroitin 6
sulfate to chondroitin 4 sulfate increases with age. The
distinction between the annulus and the nucleus decreases with age.
These changes are known as disc degeneration. Generally disc
degeneration is painless.
[0009] Premature or accelerated disc degeneration is known as
degenerative disc disease. A large portion of patients suffering
from chronic low back pain are thought to have this condition. As
the disc degenerates, the nucleus and annulus functions are
compromised. The nucleus becomes thinner and less able to handle
compression loads. The annulus fibers become redundant as the
nucleus shrinks. The redundant annular fibers are less effective in
controlling vertebral motion. The disc pathology can result in: 1)
bulging of the annulus into the spinal cord or nerves; 2) narrowing
of the space between the vertebra where the nerves exit; 3) tears
of the annulus as abnormal loads are transmitted to the annulus and
the annulus is subjected to excessive motion between vertebra; and
4) disc herniation or extrusion of the nucleus through complete
annular tears.
[0010] Current surgical treatments of disc degeneration are
destructive. One group of procedures removes the nucleus or a
portion of the nucleus; lumbar discectomy falls in this category. A
second group of procedures destroy nuclear material; Chymopapin (an
enzyme) injection, laser discectomy, and thermal therapy (heat
treatment to denature proteins) fall in this category. A third
group, spinal fusion procedures either remove the disc or the
disc's function by connecting two or more vertebra together with
bone. These destructive procedures lead to acceleration of disc
degeneration. The first two groups of procedures compromise the
treated disc. Fusion procedures transmit additional stress to the
adjacent discs. The additional stress results in premature disc
degeneration of the adjacent discs.
[0011] Prosthetic disc replacement offers many advantages. The
prosthetic disc attempts to eliminate a patient's pain while
preserving the disc's function. Current prosthetic disc implants,
however, either replace the nucleus or the nucleus and the annulus.
Both types of current procedures remove the degenerated disc
component to allow room for the prosthetic component. Although the
use of resilient materials has been proposed, the need remains for
further improvements in the way in which prosthetic components are
incorporated into the disc space, and in materials to ensure
strength and longevity. Such improvements are necessary, since the
prosthesis may be subjected to 100,000,000 compression cycles over
the life of the implant.
[0012] Artificial disc replacements (ADRs) are generally inserted
into anterior portion of the spine through a transabdominal or
retroperitoneal approach. The great vessels; aorta, vena cava,
iliac vein, and iliac artery lie on the anterior aspect of the
lumbar spine. Prior-art ADRs with anterior-to-posterior oriented
keels requires insertion of the ADR from a direct anterior approach
to the spine. The great vessels must be retracted be retracted from
the anterior portion of the spine to insert the ADRs. Retraction of
the great vessels is difficult and dangerous. The danger increases
the further the vessels are retracted. The vessels must retracted
almost completely off the anterior portion of the spine when
inserting ADRs with anterior to posterior directed keels.
SUMMARY OF THE INVENTION
[0013] This invention improves upon the prior art by providing ADR
systems with intradiscal components having non anterior-posterior
(A-P) or oblique-oriented keels. By allowing such components to be
inserted in an oblique direction, the great vessels do not require
as much retraction during insertion. In addition to traditional
methods, navigational systems may be used to help align components
with oblique-oriented keels. Such systems are well known to those
skilled in the art and include, for example, the Steath System by
Medtronic Sofamor Danek could be utilized.
[0014] An artificial disc replacement (ADR) system according to the
invention broadly comprises an intradiscal component including an
anterior portion, a posterior portion, and a keel adapted to
penetrate a vertebral endplate, the keel having an orientation
other than anterior-to-posterior when the component is
installed.
[0015] The system may further include a guides for aligning the ADR
prior to insertion, and for cutting an oblique slot into a
vertebral endplate to receive the keel. A screw adapted to
penetrate a vertebral body may be used in conjunction with the
keel. The screw and keel may converge, diverge or intersect. The
screw may further include a mechanism providing a locking
relationship with the keel. The system may further including a
guide to direct drill bits and screws through holes in the
keel.
[0016] By virtue of the invention, a second ADR may be installed at
a second level having a keel oriented differently from that of the
ADR having an orientation other than anterior-to-posterior. ADRs
according to the invention may additionally, independently include
a non-symmetrical endplate shaped so as to decrease the risk of
injuring the great vessels.
[0017] BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1A is a view of the anterior aspect of a prior-art
TDR;
[0019] FIG. 1B is a view of the side of a prior-art TDR with
anterior to posterior oriented keels;
[0020] FIG. 1C is a view of the vertebral side of a prior-art TDR
endplate;
[0021] FIG. 2A is a view of the anterior aspect of the lumbar spine
and the great vessels overlying the spine;
[0022] FIG. 2B is a view of the anterior aspect of the lumbar
spine, the great vessels, and a prior art TDR;
[0023] FIG. 3A is a view of the anterior aspect of a TDR with
novel, oblique, oriented keels;
[0024] FIG. 3B is a view of the lateral side of a TDR with novel,
oblique, oriented keels;
[0025] FIG. 3C is a view of the vertebral surface of a TDR with
novel, oblique, oriented keel;
[0026] FIG. 4A is an axial cross section of the spine and a
prior-art TDR;
[0027] FIG. 4B is an axial cross section of the spine and a TDR
with oblique oriented keels;
[0028] FIG. 5A is an axial cross section of a disc space, a TDR
with oblique keels, and a removal alignment guide;
[0029] FIG. 5B is an axial cross section of the disc space drawn in
FIG. 5A;
[0030] FIG. 6A is the view of the top of a novel guide to cut slots
for the oblique keels;
[0031] FIG. 6B is a view of the front of the novel guide drawn in
FIG. 6A;
[0032] FIG. 6C is a view of the anterior aspect of the spine and
the novel cutting guide;
[0033] FIG. 6D is a view of the endplate of a vertebrae;
[0034] FIG. 6E is a view of the front of an alternative cutting
guide to that drawn in FIG. 6B;
[0035] FIG. 6F is a view of the front of an alternative cutting
guide to that drawn in FIG. 6E;
[0036] FIG. 6G is a view of the top of the embodiment of the
cutting guide drawn in FIG. 6F;
[0037] FIG. 7 is a view of the top of an alternative embodiment of
the ADR;
[0038] FIG. 8A is an anterior view of the spine and an alternative
embodiment of the ADR drawn in FIG. 3A;
[0039] FIG. 8B is a view of the top of the ADR drawn in FIG.
8A;
[0040] FIG. 8C is a lateral view of the upper half of the ADR drawn
in FIG. 8B;
[0041] FIG. 8D is view of the top of an alternative embodiment of
the ADR drawn in FIG. 8B;
[0042] FIG. 8E is a view of the top of an alternative
embodiment;
[0043] FIG. 8F is a view of the top of an alternative embodiment of
the ADR drawn in FIG. 8B;
[0044] FIG. 8G is a lateral view of one embodiment of the screw
drawn in FIG. 8B;
[0045] FIG. 8H is an anterior view of an alternative locking
mechanism to prevent screws from backing out of the ADR drawn in
FIG. 8B;
[0046] FIG. 8I is an anterior view of an alternative locking
mechanism to prevent screws form backing out of the ADR drawn in
FIG. 8B;
[0047] FIG. 8J is an anterior view of the locking mechanism drawn
in FIG. 8I;
[0048] FIG. 9A is an anterior view of an alternative embodiment of
the guide drawn in FIG. 6F;
[0049] FIG. 9B is a lateral view of a router bit;
[0050] FIG. 9C is an oblique view of a saw blade;
[0051] FIG. 9D is an axial cross section of the disc and the
embodiment of the guide drawn in FIG. 9A;
[0052] FIG. 9E is an axial cross section of the guide drawn in FIG.
9D;
[0053] FIG. 9F is an exploded view of the top of the guide and
depth stop drawn in FIG. 9E;
[0054] FIG. 10A is an anterior view of the spine, an ADR with
oblique keels, and screws;
[0055] FIG. 10B, a novel drill guide, and a drill;
[0056] FIG. 11A is a view of the top of a novel locking screw;
[0057] FIG. 11B is a view of the top of the expandable screw drawn
in FIG. 11A;
[0058] FIG. 11C is a lateral view of the screw drawn in FIG.
11A;
[0059] FIG. 11D is a lateral view of the screw drawn in FIG.
11B;
[0060] FIG. 11E is a sagittal cross section of the screw drawn in
FIG. 11E;
[0061] FIG. 11F is a view of the tip of a screw driver that fits
into the cam of the screw drawn in FIG. 11A;
[0062] FIG. 11G is a view of the tip of a hex head screw
driver;
[0063] FIG. 11H is the view of the top of the screw drawn in FIG.
11A and the tip of the screw driver drawn in FIG. 11F;
[0064] FIG. 11I is a view of the top of the screw drawn in FIG. 11B
and the tip of the screw driver drawn in FIG. 11G;
[0065] FIG. 11J is a lateral view of a counter rotation tool;
[0066] FIG. 11K shows the screw of FIG. 11I cooperating with the
tool of FIG. 11J;
[0067] FIG. 11L is an anterior view of a portion of the ADR drawn
in FIG. 8A and the screw drawn in FIG. 11B;
[0068] FIG. 11M is an axial cross section of a portion of the ADR
drawn in FIG. 8A and the screw drawn in FIG. 11B;
[0069] FIG. 12A is sagittal cross section of the insertion
instrument drawn in FIG. 6E;
[0070] FIG. 12B is a view of the end of the instrument drawn in
FIG. 12B;
[0071] FIG. 12C is a view of the end of the instrument drawn in
FIG. 12B;
[0072] FIG. 13 is an anterior view of the spine, the ADR with
oblique keels drawn in FIG. 8A, and an ADR with straight keels;
[0073] FIG. 14A is a lateral view of the spine, a cutting guide, a
depth stop, and saw blades;
[0074] FIG. 14B is sagittal cross section of the guide, depth stop,
and saw drawn in FIG. 14A;
[0075] FIG. 14C is an anterior view of the guide drawn in FIG.
14A;
[0076] FIG. 15 is a view of the top of an alternative embodiment of
the TDR drawn in FIG. 8B; and
[0077] FIG. 16 is a view of the anterior portion of an alternative
embodiment of the guide drawn in FIG. 9A.
DETAILED DESCRIPTION OF THE INVENTION
[0078] FIG. 1A is a view of the anterior aspect of a prior-art ADR.
The anterior-to-posterior (A-P) oriented keels 102, 104 are
represented by the projections from the top and bottom ADR
endplates 106, 108. FIG. 1B is a view of the side of a prior-art
ADR with anterior to posterior oriented keels 112, 114. The keels
are represented by the trapezoidal shaped projections from the top
and bottom ADR endplates. FIG. 1C is a view of the vertebral side
of a prior-art ADR endplate. The keel is represented by area 120 of
the drawing that courses from the top (posterior aspect of the ADR)
to the bottom (anterior aspect of the ADR) of the drawing.
[0079] FIG. 2A is a view of the anterior aspect of the lumbar spine
and the great vessels overlying the spine. The aorta and iliac
arteries are indicated at 202, 204, and the vena cava and iliac
veins are indicated at 206, 208. Intervertebral discs are shown at
210, 212, and vertebrae are shown at 214, 216. FIG. 2B is a view of
the anterior aspect of the lumbar spine, the great vessels, and a
prior-art ADR. The drawing illustrates the great vessel retraction
required to insert the prior-art ADR. The drawing shows the great
vessels retracted to the left of the drawing.
[0080] FIG. 3A is a view of the anterior aspect of an ADR according
to the invention having oblique (i.e., non-AP) oriented keels 302,
304. FIG. 3B is a view of the lateral side of a ADR
oblique-oriented keels 306, 308. FIG. 3C is a view of the vertebral
surface of an ADR with oblique-oriented keel 310.
[0081] FIG. 4A is an axial cross section of the spine and a
prior-art ADR 410. The great vessels are drawn in their retracted
position on the left side of the drawing (400). The disc space is
shown at 402 with an arrow and dotted lines 404, 406 that represent
the edges of a channel needed to insert the ADR 410. The arrow
represents the direction of ADR insertion. FIG. 4B is an axial
cross section of the spine and an ADR with oblique oriented keels.
The drawing shows the novel ADR can be inserted with less great
vessel retraction. The vessels can remain over a larger portion of
the anterior aspect of the spine. The drawing also illustrates the
vessels are less compressed when they are retracted less.
[0082] FIG. 5A is an axial cross section of a disc space 500, an
ADR 504 with an oblique keel 506, and a removal alignment guide
502. FIG. 5B is an axial cross section of the disc space drawn in
FIG. 5A, and the ADR of 5A inserted into the disc space. The
position of the ADR can be checked by the orientation and position
of the alignment guide. For example, the alignment guide may be
located in the center of the disc space from the left to right, and
perpendicular to the vertebra when the ADR is placed properly. The
orientation of the alignment guide can be confirmed by direct view,
x-ray, fluoroscopy, CT scan, or MRI. The alignment guide could be
reversibly attached to the ADR. For example, the alignment guide
could be screwed to the ADR endplate.
[0083] FIG. 6A is the view of the top of a guide 600 having a
handle 602 and one or more grooves 604 used to cut slots for the
oblique keels. The area 602 represents an oblique groove on the top
of the guide. FIG. 6B is a view of the front of the novel guide
drawn in FIG. 6A. The guide is inserted into the disc space via an
oblique course. The position of the guide may be checked as
outlined in FIG. 5B. For example, surgeons can use x-ray,
fluoroscopy, CT scan, or MRI to confirm the proper position and
orientation of the guide. Once the guide is aligned properly, a
cutting instrument such as an osteotome, drill, or saw can be
inserted into the grooves 602 of the guide. The cutting instrument
is advanced into the guide to from oblique slots in the vertebrae.
The cutting instrument may have a depth stop that prevents cutting
through the back of the vertebra. Alternatively, the slot within
the cutting guide could end prior to the end of the guide.
[0084] FIG. 6C is a view of the anterior aspect of the spine and
the novel cutting guide. The areas 620, 622 of the drawing
represent the anterior aspect of slots cut into the vertebrae using
the cutting guide described in FIG. 6C. FIG. 6D is a view of the
endplate of vertebrae 630 showing an oblique slot 632. FIG. 6E is a
view of the front of an alternative cutting guide to that drawn in
FIG. 6B having a partially radio-opaque handle 640. The center 642
of the handle is radio-lucent. The hole within the guide, that
receives the handle, courses through the guide. When aligned
properly, an x-ray directed from anterior to posterior, shows the
radio-opaque circle within the handle, centered in the hole in the
guide that receives the handle.
[0085] FIG. 6F is a view of the front of an alternative cutting
guide including a single slot 660 that courses obliquely through
the cutting guide. Slots are created in both vertebrae at the same
time by inserting a cutting instrument into the guide. The front of
the guide has a window 662 that directs the cutting instrument into
the slot in the guide. FIG. 6G is a view of the top of the
embodiment of the cutting guide drawn in FIG. 6F used to form slot
670. The projection from the bottom of the guide represents the
window 622 on the front of the guide. The window portion of the
guide sits outside the disc space. The extradiscal location of the
raised window, allows the guide to be rotated in the disc space.
The dotted lines within the raised window of the guide represent
the oblique course of the walls of the window.
[0086] FIG. 7 is a view of the top of an alternative, asymmetric
embodiment of an ADR according to the invention. A portion of the
ADR on the left side of the drawing has been removed. The reduced
profile of the ADR facilitates passage of the ADR by the great
vessels during insertion of the ADR into the disc space.
[0087] FIG. 8A is an anterior view of the spine and an alternative
embodiment of an ADR having screws 802, 804 that help hold the ADR
in the disc space. FIG. 8B is a view of the top of the ADR drawn in
FIG. 8A. A screw 800 passes through the front of the ADR and an
oblique keel 820. The convergence of the screw and the keel resist
extrusion of the ADR in a direction parallel to the keel.
[0088] FIG. 8C is a lateral view of the upper half of the ADR drawn
in FIG. 8B. A cross section 830 of the screw can be seen in a hole
in the keel. FIG. 8D is view of the top of an alternative
embodiment of an ADR having a screw 840 that does not pass through
keel 842. FIG. 8E is a view of the top of a further embodiment
wherein a screw 850 and keel 852 converge, but the screw does not
pass through the keel.
[0089] FIG. 8F is a view of the top of an alternative embodiment
wherein the screw 860 and the keel 862 diverge. FIG. 8G is a
lateral view of an embodiment of a screw having a coarse thread
pattern 870 on the portion of the screw that rests in the vertebra.
The thread pattern 872 is finer in the area of the screw that lies
in the ADR. A single thread could be chased on the coarse portion
of the thread. Multiple threads could be traced in the ADR portion
of the screw. The screw may be tightened to the ADR without
stripping out the threads in the vertebra. The tight fit between
the screw and the ADR prevent the screw from backing out of the
ADR. Alternatively, the threads of the screw could be slightly
different than the threads in the ADR. The threads of the screw
could strip slightly as the screw is tightened in the ADR, thus
locking the screw to the ADR.
[0090] FIG. 8H is an anterior view of an alternative locking
mechanism to prevent screws from backing out of the ADR. A C-ring
within the ADR expands as the head of the screw passes through the
C-ring. The C-ring contracts after the head of the screw has passed
through the C-ring, thus locking the screw in the ADR.
[0091] FIG. 8I is an anterior view of an alternative locking
mechanism to prevent screws form backing out of the ADR. A screw
has been placed in a hole in the ADR. FIG. 8J is an anterior view
of the locking mechanism drawn in FIG. 8I. A tool has been inserted
and rotated within the slot adjacent to the hole for the screw in
the ADR. The thin bridge of ADR between the holes has been deformed
by the tool. A portion of the ADR blocks the screw from backing out
of the ADR.
[0092] FIG. 9A is an anterior view of an alternative embodiment of
a guide having two slots 902, 904. The smaller slot 902 is designed
to guide a router-like bit. The router-like bit mills a recess. The
recess accepts the portion of the ADR that holds the screw. The
longer slot 904 accepts a saw blade used to cut a slot for the
oblique keel. Prior art slots are created with chisels which may
cause microfractures and lead to a complete fracture of a vertebra.
Cutting bone with drill bits, router bits, and saw blades help to
preserve the strength of the vertebrae.
[0093] FIG. 9B is a lateral view of a router bit. The dotted area
of the drawing represents a collar. The collar cooperates with the
slot of the guide to create a recessed area in the vertebrae. FIG.
9C is an oblique view of a saw blade. The saw blade cooperates with
the larger slot in the guide to create a slot for the ADR keels.
FIG. 9D is an axial cross section of the disc and the embodiment of
the guide drawn in FIG. 9A. The dotted area represents opening in
the guide.
[0094] FIG. 9E is an axial cross section of the guide drawn in FIG.
9D. A removable depth stop. is placed over the slot used to create
a spot for the keels. Depth stops of various thickness can be used
to accommodate vertebrae of different sizes. FIG. 9F is an exploded
view of the top of the guide and depth stop drawn in FIG. 9E.
[0095] FIG. 10A is an anterior view of the spine, an ADR with
oblique keels, and screws 1002, 1004. The screws are threaded into
the keels. The threads of the screws may strip slightly as they
enter the holes in the keels. FIG. 10B is a view of the top of the
ADR drawn in FIG. 10B, a novel drill guide 1020, and a drill 1030.
The removable guide attaches to the front of the ADR. The guide
directs the drill into the hole in the keel. A sleeve fits into the
guide to accept the drill bit. The hole in the guide that remains
after removing the sleeve is used to guide the screw into the hole
in the keel.
[0096] FIG. 11A is a view of the top of a novel locking screw. A
cam 1102 can be rotated to expand the head of screw. FIG. 11B is a
view of the top of the expandable screw drawn in FIG. 11A. The cam
has been rotated 90 degrees to expand portions 1110, 1112, 1114,
1116 of the head of the screw. FIG. 11C is a lateral view of the
screw drawn in FIG. 11A. The head of the screw is drawn in its
resting shape. FIG. 11D is a lateral view of the screw drawn in
FIG. 11B. The head of the screw has been expanded. FIG. 11E is a
sagittal cross section of the screw. FIG. 11F is a view of the tip
of a screw driver that fits into the cam of the screw drawn in FIG.
11A. The thin projections from the sides of the hex head fit into
the slots of the cam. The projections impinge against the side of
the screw as the screw driver is rotated. The projections allow
advancement of the screw without rotating the cam relative to the
screw.
[0097] FIG. 11G is a view of the tip of a hex head screw driver.
The hex head screw driver is used to rotate the cam without
rotating the screw. FIG. 11H is the view of the top of the screw
drawn in FIG. 11A and the tip of the screw driver drawn in FIG.
11F. The screw driver is used to rotate the screw and the cam as a
unit. The screw is drawn in its contracted shape.
[0098] FIG. 11I is a view of the top of the screw drawn in FIG. 11B
and the tip of the screw driver drawn in FIG. 11G. The hex head
screw driver is used to expand the head of the screw by rotating
the cam relative to the screw. FIG. 11J is a lateral view of a
counter rotation tool. The tool is cannulated. The hex head screw
driver fits through the lumen of the counter rotation tool. The
projections from the tool engage the sides of the screw. The
counter rotation prevents rotation of the screw as the cam is
rotated. FIG. 11K shows the screw of FIG. 11I cooperating with the
tool of FIG. 11J. FIG. 11L is an anterior view of a portion of the
ADR drawn in FIG. 8A and the screw drawn in FIG. 11B. The head of
the screw is expanded after the screw is fully seated in the ADR.
Expanding the screw locks the screw into the hole of the ADR. The
head of the screw could also be expanded into a ring that fits into
the hole in the ADR.
[0099] FIG. 11M is an axial cross section of a portion of the ADR
drawn in FIG. 8A and the screw drawn in FIG. 11B. The head of the
screw is expanded after it is advanced past the first hole in the
ADR. The expanded head of the screw becomes locked between the two
screw holes in the ADR.
[0100] FIG. 12A is sagittal cross section of the insertion
instrument drawn in FIG. 6E. The shaft of the instrument is
preferably radio-opaque, whereas the handle 1202 of the instrument
is radiolucent. FIG. 12B is a view of the end of the instrument
drawn in FIG. 12B. The instrument is drawn as though it is viewed
by a fluoroscope. The circular cross section of the shaft of the
instrument indicates the fluoroscope is aligned directly
perpendicular to the instrument. Surgeons can use the alignment of
the tool and the fluoroscope to help align the ADR. FIG. 12C is a
view of the end of the instrument drawn in FIG. 12B. The instrument
is no longer circular in cross section. The image of the instrument
indicates the fluoroscope is not aligned perpendicular to the
instrument and the ADR.
[0101] FIG. 13 is an anterior view of the spine, the ADR 1302 with
oblique keels drawn in FIG. 8A, and an ADR 1304 with straight
keels. The novel method of pairing ADRs with oblique keels with
ADRs with straight keels reduces the risk of fracturing the
interposed vertebra. Keels that are parallel and directly across
from one another on either vertebral endplate (VEP) may act as
wedges to fracture the vertebra. Keels in different locations on
the VEPs and that course in different directions reduce the risk of
fracturing the vertebra. The locking screw courses an oblique
direction in the ADR with straight keels.
[0102] FIG. 14A is a lateral view of the spine, a cutting guide
1402, a depth stop 1404, and saw blades 1406, 1408. The cutting
guide was taught in my co-pending U.S. patent application Ser. No.
10/421,436, incorporated herein by reference. Novel depth stops of
different thickness are used accommodate vertebrae of different
sizes. The removal depth stops work like the stops described in
FIG. 9F. The use of saw blades rather than chisels reduces the
damage to the vertebrae. FIG. 14B is sagittal cross section of the
guide, depth stop, and saw drawn in FIG. 14A. The saw impinges upon
the stop to prevent the saw from entering the spinal canal. FIG.
14C is an anterior view of the guide drawn in FIG. 14A. The circle
1410 in the center of the drawing represents the shaft of a
removable impaction handle.
[0103] FIG. 15 is a view of the top of an alternative embodiment of
an ADR having a screw 1550 placed through the anterior portion of
the keel. The anterior portion of the keel is angled to ease
insertion of the screw. The anterior portion of the keel may have
features to cooperate with a drill and a screw guide. The removable
guide aligns the hole for the screw and the screw.
[0104] FIG. 16 is a view of the anterior portion of an alternative
embodiment of a guide used to prepare the vertebrae to receive the
embodiment of the ADR drawn in FIG. 15. The slot 1680 is used to
guide a saw to prepare the vertebrae to receive the straight
portions of the keels. The guide also has areas 1682, 1684 to mill
recesses in the vertebrae to accept the angled portions of the
keels. The guide also incorporates an alternative embodiment of the
partially radiolucent handle drawn in FIG. 6E. Partially
radiolucent components are incorporated into the guide (areas 1690,
1692). The partially radiolucent markers help determine if the
guide is inserted with the correct axial rotation. The guide is
placed properly if radio-opaque circles appear centered in
radiolucent circles. The anatomy of the spine, for example the
pedicles and the spinous processes of the vertebrae can be used to
align the beam of the fluoroscope. The guide can then be aligned
with respect to the fluoroscope.
* * * * *