U.S. patent application number 11/925569 was filed with the patent office on 2008-02-21 for apparatus and method for performing spinal surgery.
This patent application is currently assigned to Dynamic Spine, Inc.. Invention is credited to Glenn Robin Buttermann, Doug Wayne Cooper.
Application Number | 20080045966 11/925569 |
Document ID | / |
Family ID | 21926301 |
Filed Date | 2008-02-21 |
United States Patent
Application |
20080045966 |
Kind Code |
A1 |
Buttermann; Glenn Robin ; et
al. |
February 21, 2008 |
APPARATUS AND METHOD FOR PERFORMING SPINAL SURGERY
Abstract
A cutting guide for use in spinal surgery includes a sidewall
defining an internal cavity. A chisel guide, for use with the
cutting guide, includes a first block member to be inserted into
the internal cavity of the cutting guide to position the first
block member adjacent the vertebral body. The chisel guide also
includes a second block member connected to the first block member.
An apparatus for creating a cavity in a-vertebral body endplate and
in an intervertebral disc may be a compressor or a distractor
having at least one cutting implement thereon. A tensioner
determines a proper elongation distance in a prosthesis implanted
in a vertebral body.
Inventors: |
Buttermann; Glenn Robin;
(Mahtomedi, MN) ; Cooper; Doug Wayne; (Redwing,
MN) |
Correspondence
Address: |
FOLEY AND LARDNER LLP;SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
Dynamic Spine, Inc.
|
Family ID: |
21926301 |
Appl. No.: |
11/925569 |
Filed: |
October 26, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10701599 |
Nov 6, 2003 |
7303565 |
|
|
11925569 |
Oct 26, 2007 |
|
|
|
10043266 |
Jan 14, 2002 |
6761723 |
|
|
10701599 |
Nov 6, 2003 |
|
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Current U.S.
Class: |
606/87 |
Current CPC
Class: |
A61B 2090/034 20160201;
A61B 17/1617 20130101; A61B 2017/320052 20130101; A61B 17/025
20130101; A61B 17/15 20130101; A61B 17/1757 20130101; A61B
2017/00004 20130101; A61B 17/1671 20130101; A61B 2017/0256
20130101; A61B 17/1604 20130101; A61B 17/1735 20130101; A61B
17/1611 20130101 |
Class at
Publication: |
606/087 |
International
Class: |
A61F 5/00 20060101
A61F005/00 |
Claims
1. A cutting guide for use in removing bone from a vertebral body,
comprising: a sidewall defining an internal cavity, the sidewall
having (i) a first edge to face toward and to contact the vertebral
body in at least three points and (ii) a second, opposite edge to
face away from the vertebral body, the first edge including at
least two concave portions and at least one convex portion oriented
generally perpendicular to the at least two concave portions.
2. The cutting guide according to claim 1, wherein the sidewall
comprises four walls arranged to form a rectangular
cross-section.
3. The cutting guide according to claim 2, wherein the first edge
is concave along a first of the four walls and along an opposite
second of the four walls, and wherein the first edge is convex
along a third of the four walls and along an opposite fourth of the
four walls.
4. The cutting guide according to claim 3, wherein the concave
first edge along the first wall is a mirror image of the concave
first edge along the second wall, and wherein the convex first edge
along the third wall is a mirror image of the convex first edge
along the fourth wall.
5. The cutting guide according to claim 2, wherein at least one of
the four walls includes a hole extending from the first edge to the
second edge to receive a fastener therethrough.
6. The cutting guide according to claim 1, wherein the at least one
concave portion is formed by a plurality of adjacent surfaces, and
wherein the at least one convex portion is formed by a plurality of
adjacent surfaces.
7. A chisel guide for use in cutting bone of a vertebral body
comprising: a first block member to be positioned adjacent the
vertebral body; and a second block member connected to the first
block member, the second block member having a channel formed on
one side thereof, the channel terminating at the first block
member.
8. The chisel guide according to claim 7, wherein the first block
member and the second block member are formed as one integral
piece.
9. The chisel guide according to claim 7, wherein the first block
member has a first width, and the second block member has a second
width greater than the first width such that the second block
member form a pair of opposed shoulders with respect to the first
block member.
10. The chisel guide according to claim 7, wherein the second block
member extends beyond the perimeter of the first block member in at
least one dimension to form a shoulder with the first block
member.
11. A cutting guide and chisel guide combination for use in
removing bone from a vertebral body comprising: a cutting guide
including, a sidewall defining an internal cavity, the sidewall
having (i) a first edge to face toward and to contact the vertebral
body in at least three points and (ii) a second, opposite edge to
face away from the vertebral body; and a chisel guide including, a
first block member to be inserted into the internal cavity of the
cutting guide to position the first block member adjacent the
vertebral body such that a passage remains between a first side of
the first block member and an inner surface of the sidewall of the
cutting guide, and a second block member connected to the first
block member.
12. The cutting guide and chisel guide combination according to
claim 11, wherein the first block member and the second block
member are formed as one integral piece.
13. The cutting guide and chisel guide combination according to
claim 11, wherein the second block member is solid.
14. The cutting guide and chisel guide combination according to
claim 11, wherein the first block member has a first width, and the
second block member has a second width greater than the first width
such that the second block member forms a pair of opposed shoulders
with respect to the first block member.
15. The cutting guide and chisel guide combination according to
claim 11, wherein the second block member extends beyond the
perimeter of the first block member in at least one dimension to
form a shoulder with the first block member.
16. The cutting guide and chisel guide combination according to
claim 12, wherein the second block member comprises a channel
formed on one side thereof, the channel terminating at the first
block member.
17. An apparatus for use in removing bone from a vertebral body
comprising: a shaft having a first end and a second end, the second
end of the shaft connectable to a power source; and a reamer
connected to the first end of the shaft, the reamer including at
least one cutting member and a collection space to collect bone
fragments cut by the at least one cutting member, wherein adjacent
each of the at least one cutting member is a slot through which the
bone fragments pass into the collection space.
18. The apparatus according to claim 17, wherein the reamer is
detachably connected to the first end of the shaft.
19. The apparatus according to claim 17, wherein the power source
is a drill.
20. The apparatus according to claim 17, wherein the reamer has a
circular cross-section.
21. The apparatus according to claim 17, wherein the at least one
cutting member is positioned on a bone engaging surface of the
reamer.
22. The apparatus according to claim 21, wherein the bone engaging
surface is flat except for the at least one cutting implement and
slots associated therewith.
23-51. (canceled)
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to the field of spinal surgery. More
specifically, this invention relates to apparatuses for creating
cavities in vertebral bodies and in intervertebral discs located
between the vertebral bodies. This invention also relates to
methods for creating such cavities. Once the cavities are created
with the apparatuses and according to the methods of the present
invention, an intervertebral prosthetic device, designed to replace
a damaged intervertebral disc, can be implanted in the cavities.
Moreover, the implanted device may be used in vertebral body fusion
or in reconstruction of mobile discs through spinal arthroplasty
(i.e., disc replacement).
[0002] The human spine is a flexible structure comprised of
twenty-five vertebrae. Intervertebral discs separate and cushion
adjacent vertebrae. The intervertebral discs act as shock absorbers
and allow bending between the vertebrae.
[0003] An intervertebral disc comprises two major components: the
nucleus pulposus and the annulus fibrosis. The nucleus pulposus is
centrally located in the disc and occupies 25-40% of the disc's
total cross-sectional area. The nucleus pulposus usually contains
70-90% water by weight and mechanically may function like an
incompressible hydrostatic material. The annulus fibrosis surrounds
the nucleus pulposus and resists torsional and bending forces
applied to the disc. Thus, the annulus fibrosis serves as the
disc's main stabilizing structure. A healthy disc relies on the
unique relationship of the nucleus and annulus to one another. The
top and bottom surfaces of intervertebral discs abut vertebral body
endplates.
[0004] Individuals with damaged or degenerated discs often
experience significant pain. The pain results, in part, from
instability in the intervertebral joint due to a loss of
hydrostatic pressure in the nucleus pulposus, which leads to a loss
of disc height and altered loading of the annulus fibrosis.
[0005] A conventional treatment for degenerative disc disease is
spinal fusion. In one such surgical procedure, a surgeon removes
the damaged natural disc and then fuses the two adjacent vertebral
bodies into one piece. The surgeon fuses the vertebral bodies by
grafting bone between the adjacent vertebrae and sometimes uses
metal rods, cages, or screws to hold the graft in place until the
graft heals. Other fusion procedures do not require surgical
removal of the disc.
[0006] Although spinal fusion may alleviate pain associated with
degenerative disk disease, it also results in loss of motion at the
fused vertebral joint. Lack of motion at the fused site puts
abnormal loads on the adjacent discs above and below the fusion.
This additional pressure may cause the adjacent discs to degenerate
and produce pain, thereby recreating the problem which originally
existed. To remedy the problems associated with spinal fusion,
various prosthetic devices were developed to replace the damaged
disc with a suitable biomechanical equivalent.
[0007] Existing prosthetic devices have met with limited success in
reproducing the biomechanics of a natural disc. For example, U.S.
Pat. No. 4,759,769 to Hedman et al. discloses a synthetic disc
having upper and lower plates hinged together. Although the hinged
disc allows forward bending between adjacent vertebrae, the hinged
disc does not allow axial compression or lateral flexion. Nor does
it allow axial rotation of the vertebral column at the site of the
implant. Therefore, the Hedman et al. device lacks many of the
biomechanics of a natural disc.
[0008] Likewise, the prosthetic disc device disclosed in U.S. Pat.
No. 4,309,777 to Patil does not replicate natural motion between
adjacent discs. The Patil device includes two cups, one overlapping
the other and spaced from the other by springs. The cups move only
in a single axial dimension. Thus, the Patil device does not enable
natural flexion of the spine in any direction. In addition, the
highly constrained motion of the Patil device can lead to high
device/tissue interface stresses and implant loosening.
[0009] Many synthetic devices connect to the vertebral bodies by
conventional mechanical attachments, such as pegs or screws, which
are known to loosen under cyclic loading conditions. Other
synthetic devices use plastic or elastomeric components which, over
a lifetime, produce debris from wear and possible unknown side
effects.
[0010] In response to these and other known problems associated
with synthetic prosthetic disc devices, U.S. Pat. No. 5,827,328 to
Buttermann, which is incorporated herein by reference in its
entirety, discloses an intervertebral synthetic prosthetic device
designed to replace the biomechanical functionality of a failing
intervertebral disc. One embodiment of the Buttermann device
includes a first fixation member for implantation in a first
vertebral body, a second fixation member for implantation in a
second vertebral body adjacent the first vertebral body, and a
compressible member that is positioned between the first and second
fixation members. The Buttermann device overcomes the
aforementioned problems with synthetic devices.
SUMMARY OF THE INVENTION
[0011] There is a need for improved apparatuses and methods by
which cavities can be created in vertebral bodies and in an
intervertebral disc. Once the cavities are created, an
intervertebral prosthetic device designed to replace a damaged
intervertebral disc, such as the one described in U.S. Pat. No.
5,827,328, can be implanted in the cavities.
[0012] In one aspect of the present invention, a cutting guide is
provided for use in removing bone from a vertebral body. The
cutting guide includes a sidewall that defines an internal cavity.
In addition, the sidewall has (i) a first edge to face toward and
to contact a vertebral body in at least three points and (ii) a
second, opposite edge to face away from the vertebral body. The
first edge includes at least two concave portions and at least one
convex portion oriented generally perpendicular to the at least two
concave portions.
[0013] The sidewall of the cutting guide may be comprised of four
walls arranged to form a rectangular cross-section. At least one of
the four walls may include a hole extending from the first edge to
the second edge to receive a fastener therethrough. Further, the
first edge of the sidewall may be concave along a first of the four
walls and along an opposite second of the four walls, and it may be
convex along a third of the four walls and along an opposite fourth
of the four walls. The concave first edge along the first wall may
be a mirror image of the concave first edge along the second wall.
Similarly, the convex first edge along the third wall may be a
mirror image of the convex first edge along the fourth wall.
Moreover, although the concave and convex edges may each comprise
one smooth surface, they also may be formed by a plurality of
adjacent surfaces.
[0014] In another aspect of the invention, a chisel guide is
provided for use in cutting bone of a vertebral body. The chisel
guide includes a first block member to be positioned adjacent the
vertebral body and a second block member connected to the first
block member. The second block member has a channel, formed on one
side thereof, which terminates at the first block member.
[0015] In one embodiment of the chisel guide, the first block
member and the second block member may be formed as one integral
piece. Further, the second block member may extend beyond the
perimeter of the first block member in at least one dimension to
form a shoulder with the first block member. For example, the
second block member may have a width greater than the width of the
first block member such that the second block member forms a pair
of opposed shoulders with respect to the first member.
[0016] Another aspect of the invention relates to a cutting guide
and chisel guide combination for use in removing bone from a
vertebral body. The combination includes a cutting guide having a
sidewall defining an internal cavity. The sidewall, in turn, has a
first edge to face toward and to contact a vertebral body in at
least three points and a second, opposite edge to face away from
the vertebral body. The combination also includes a chisel guide.
The chisel guide has a first block member and a second block member
connected to the first block member. The first block member is
adapted to be inserted into the internal cavity of the cutting
guide to position the first block member adjacent the vertebral
body such that a passage remains between a first side of the first
block member and an inner surface of the sidewall of the cutting
guide.
[0017] In the aforementioned cutting guide and chisel guide
combination, the first and second block members may be formed as an
integral piece. Moreover, the second block member may be solid. In
addition, the second block member may extend beyond the perimeter
of the first block member, in at least one dimension, to form a
shoulder with the first block member. For example, the second block
member may have a width which is greater than the width of the
first block member so that the second block member forms a pair of
opposed shoulders with respect to the first block member. Finally,
the second block member may include a channel which is formed on
one side thereof and which terminates at the first block
member.
[0018] In yet another aspect of the invention, an apparatus for use
in removing bone from a vertebral body is provided. This apparatus
includes a shaft and a reamer. The shaft has a first end and a
second end, and the second end of the shaft is connectable to a
power source. The reamer is connected to the first end of the
shaft. The reamer includes at least one cutting member and a
collection space to collect bone fragments cut by the cutting
member. A slot, through which the bone fragments pass into the
collection space, is adjacent the at least one cutting member.
[0019] The reamer may be detachably connected to the first end of
the shaft. In addition, the reamer may have a circular
cross-section. Various power sources, such as a drill, may be used
to rotate the second end of the shaft. In one embodiment, the
cutting member is positioned on a bone engaging surface of the
reamer. The bone engaging surface of the reamer may be flat, except
for the cutting implement and slots associated therewith.
[0020] In still a further aspect of the invention, an apparatus for
creating a cavity in a vertebral body endplate and in an
intervertebral disc is provided. The apparatus includes a handle, a
first arm, and a second arm movable toward the first arm upon
actuation of the handle. The apparatus also includes a first
cutting implement that is mounted to the first arm and that has a
generally circular sidewall that terminates in a first cutting
edge. The first cutting edge faces away from the first arm. In one
embodiment of the cavity creating apparatus, the first cutting edge
also may face away from the second arm. In another embodiment, the
first cutting edge may face toward the second arm.
[0021] In addition, the apparatus may also include a second cutting
implement mounted to the second arm and having a generally circular
sidewall that terminates in a second cutting edge, the second
cutting edge facing away from the second arm and facing toward the
first cutting edge so that, upon actuation of the handle, the first
and second cutting edges move toward each other. The cutting edges
of the cutting implements may be serrated. The cutting implements
also may be rotatably mounted to their respective arms. Moreover,
in an embodiment having two cutting implements, the cutting
implements may be mounted to rotate about the same axis of
rotation.
[0022] In yet a further aspect of the invention, a tensioner
apparatus for use in determining a proper elongation distance in a
prosthesis implanted in a vertebral body is provided. The tensioner
apparatus includes a first arm and a second arm, each having a
handle portion and a separator portion. A pivot joins the first arm
to the second arm and separates the separator portions from the
handle portions. In addition, at least one tension measuring
element is positioned on the first arm; the tension measuring
element may be a strain gage.
[0023] The tensioner apparatus also may include at least one strain
gage positioned on the second arm. Moreover, the strain gages
positioned on the first and second arms may be part of a Wheatstone
bridge and may be positioned on the separator portions of the first
and second arms, respectively.
[0024] The invention also contemplates a method of creating a
cavity in a vertebral body. The cavity creating method includes
removably attaching a cutting guide to an outer surface of a
vertebral body. The cutting guide has a cavity therein. The method
also includes puncturing through the outer surface and cortical
bone of the vertebral body along a perimeter of the cavity in the
cutting guide, removing the punctured cortical bone of the
vertebral body to expose bone in the interior of the vertebral
body, and removing the bone in the interior of the vertebral
body.
[0025] The method of creating a cavity in a vertebral body may also
include inserting a chisel guide in the cavity in the cutting
guide. In this method, the puncturing step may include using the
chisel guide to guide a chisel, having a chisel blade, along a
perimeter of the cavity in the cutting guide. Alternatively, the
puncturing step may be accomplished by using a motorized sagittal
saw. Regardless of whether a chisel and chisel guide or a sagittal
saw is used to puncture through the outer surface and cortical
bone, the step of removing the bone in the interior of the
vertebral body may be accomplished using a reamer.
[0026] The invention further contemplates a method of creating an
intervertebral disc cavity. The method includes providing an
apparatus including a first arm having a first cutting implement
attached thereto, a second arm, and a handle. The method also
includes positioning the first arm in a cavity in a first vertebral
body, compressing the handle of compressor so that the first and
second arms move in a direction towards each other, cutting through
the nucleus pulposus of the intervertebral disc with the first
cutting implement, and removing the nucleus pulposus of the
intervertebral disc to create the intervertebral disk cavity. This
method also may include positioning the second arm of the
compressor in a cavity in a second vertebral body, wherein the
second arm has a second cutting implement thereon; and cutting
through the nucleus pulposus of the intervertebral disc with the
second cutting implement.
[0027] The method for creating an intervertebral disc cavity may
also include, prior to the step of positioning a first arm of a
compressor in a cavity in a first vertebral body, attaching a
cutting guide to a surface of the first vertebral body, the cutting
guide defining a cavity; cutting through the surface and cortical
bone of the first vertebral body along an inside perimeter of the
cavity in the cutting guide; removing the cut cortical bone of the
first vertebral body to expose bone in an interior of the first
vertebral body; removing the bone in the interior of the first
vertebral body to create the first vertebral body cavity; and
removing the cutting guide from the first vertebral body. Further,
the method also may include attaching the cutting guide to a
surface of the second vertebral body; cutting through the surface
and cortical bone of the second vertebral body along the inside
perimeter of the cavity in the cutting guide; removing the cut
cortical bone of the second vertebral body to expose the bone in
the interior of the second vertebral body; and removing the bone in
the interior of the second vertebral body to create the second
vertebral body cavity.
[0028] In addition, the invention contemplates a method of applying
a predetermined load to an implanted device. The implanted device
has a fixation member implanted within a vertebral body and a
compressible member implanted within an intervertebral disc. The
method includes providing a tensioner including a first arm and a
second arm each having a handle portion and a separator portion. A
pivot pin joins the first arm to the second arm and separates the
separator portions from the handle portions. At least one strain
gage is positioned on the first arm. The method also includes
inserting the first and the second arms into the fixation member,
and moving the handle portions toward each other to thereby move
the separator portions away from each other until one of the
separator portions contacts an upper member of the fixation member
and the other of the separator portions contacts a lower member of
the fixation member. The method further includes elongating the
fixation member with the tensioner, and monitoring a voltage
measured by the at least one strain gage, the voltage being
representative of the load applied by the tensioner and thus the
reactive load experienced by the compressible member of the
implanted device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] These and other features, aspects, and advantages of the
present invention will become more apparent from the following
description, appended claims, and accompanying exemplary
embodiments shown in the drawings, which are briefly described
below.
[0030] FIG. 1A is a top perspective view of a cutting guide;
[0031] FIG. 1B is a top view of the cutting guide of FIG. 1A;
[0032] FIG. 1C is a side elevation view of the cutting guide of
FIG. 1A;
[0033] FIG. 1D is a side elevation view of a cutting guide having
an alternative shape;
[0034] FIG. 2A is a top perspective view of a chisel guide;
[0035] FIG. 2B is a top view of the chisel guide of FIG. 2A;
[0036] FIG. 2C is a side elevation view of the chisel guide of FIG.
2A;
[0037] FIG. 2D is a front elevation view of the chisel guide of
FIG. 2A;
[0038] FIG. 3A is a top perspective view of the chisel guide
inserted into the cutting guide;
[0039] FIG. 3B is a top perspective view of a chisel for use with
the cutting guide and chisel guide of FIG. 3A;
[0040] FIG. 3C is a perspective view of the chisel of FIG. 3B
inserted into the cutting guide and chisel guide combination of
FIG. 3A;
[0041] FIG. 4A is an exploded side view, in cross section, of a
rotatable shaft and reamer;
[0042] FIG. 4B is an exploded perspective view of the rotatable
shaft and reamer of FIG. 4A;
[0043] FIG. 4C is a perspective view of the rotatable shaft and
reamer of FIGS. 4A and 4B;
[0044] FIG. 5A is a perspective view of an endplate and nucleus
cutter;
[0045] FIG. 5B is a side elevation sectional view, in cross
section, of the endplate and nucleus cutter of FIG. 5A;
[0046] FIG. 5C is a side elevation section view, in cross section,
of an alternative embodiment of the endplate and nucleus
cutter;
[0047] FIG. 6A is a side elevation view of a compressor having a
pair of endplate and nucleus cutters mounted thereto;
[0048] FIG. 6B is a side elevation view of a distractor having one
endplate and nucleus cutter mounted thereto;
[0049] FIG. 6C is an enlarged side elevation view, in cross
section, of encircled area 6C-6C in FIG. 6A with the screw
removed;
[0050] FIG. 7 is a side elevation view of a tensioner
apparatus;
[0051] FIG. 8 is a schematic view of a cutting guide affixed to a
curved surface of a vertebral body;
[0052] FIG. 9A is a schematic view of a cutting guide and chisel
guide combination and a chisel engaged in the cutting guide and
chisel combination to cut through the bone of the vertebral
body;
[0053] FIG. 9B is a schematic view of a cutting guide affixed to a
vertebral body and a sagittal saw positioned in the cutting guide
to cut through the bone of the vertebral body;
[0054] FIG. 10 is a schematic view of a vertebral body with a
section of the cortical bone removed from the vertebral body;
[0055] FIG. 11 is a schematic view of a reamer, positioned in the
cutting guide, for drilling into the vertebral bone of the
vertebral body to create a cavity;
[0056] FIG. 12A is a schematic view of two adjacent vertebral
bodies having cavities therein and a compressor having two endplate
and nucleus cutters thereon;
[0057] FIG. 12B is a schematic view of the compressor shown in FIG.
12A with the endplate and nucleus cutters inserted into the
cavities of the adjacent vertebral bodies;
[0058] FIG. 13 is a schematic, cut-away left side view of an
intervertebral prosthetic device implanted in adjacent vertebral
bodies and in an intervertebral disc;
[0059] FIG. 14 is a schematic, cut-away left side view of a cavity
in a vertebral body, showing the tensioner positioned therein;
[0060] FIG. 15 is a schematic, cut-away left side view of the
adjacent vertebral bodies having an intervertebral prosthetic
device implanted therein, wherein the vertebral bodies are provided
with bone shavings to induce bone grafting;
[0061] FIG. 16 is a schematic left side view of the adjacent
vertebral bodies with the cortical bone repositioned to cover the
cavities in the vertebral bodies;
[0062] FIG. 17A is a schematic view of a vertebral body having a
cavity therein and an alternative embodiment of the distractor
having one endplate and nucleus cutter thereon;
[0063] FIG. 17B is a schematic view of the distractor shown in FIG.
17A with the endplate and nucleus cutter inserted into the cavity
of the vertebral body and forced downward into the nucleus pulposus
of the intervertebral disc;
[0064] FIG. 18 is a schematic, cut-away left side view of the
vertebral body and intervertebral disc of FIG. 17B having a
prosthetic device positioned therein;
[0065] FIG. 19A is a schematic view of a rotatable dome-shaped
cutter; and
[0066] FIG. 19B is a schematic, cut-away left side view of a
vertebral body having a cavity formed therein by the rotatable
dome-shaped cutter of FIG. 19A.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0067] Referring now to the drawings, wherein like numerals
indicate like parts, and initially to FIGS. 1A-1C and 8, there will
be seen a cutting guide 20 for use in removing bone 22 from a
vertebral body 24. The cutting guide is designed to be placed into
contact with the outer surface of the vertebral body 24 to "guide"
a surgical instrument as it cuts through the cortical bone of the
vertebral body, as shown in FIGS. 8 and 9A-9B and as later
described in more detail. In this regard, the cutting guide 20 has
a sidewall that defines an internal cavity 34 extending through the
cutting guide 20. The sidewall generally has four walls 26, 28, 30,
32 arranged to form a rectangular cross-section. Although the
cavity 34 is preferably rectangular in cross section, the walls 26,
28, 30, 32 can be configured to define a cavity that is square in
cross-section or any other suitable geometric shape.
[0068] The cutting guide 20 has a first edge 38 to face toward and
to contact the vertebral body 24. The cutting guide also has a
second, opposite edge 36 to face away from the vertebral body 24.
The first edge 38 of the cutting guide is contoured to contact the
vertebral body in at least three points, although it will be
understood that the first edge 38 can have four or more points of
contact with a vertebral body. The first edge 38 includes both
concave portions 40 and convex portions 42 configured to fit
against the curved, outer surface of the vertebral body 24. The
second edge 36 of the cutting guide 20 is substantially planar.
[0069] The concave portions 40 of the first edge 38 are oriented
generally perpendicular to the convex portions 42. In particular,
the concave portions 40 are formed along the first edge 38 of
opposite walls 26, 30, and the convex portions 42 are formed along
the first edge 38 of opposite walls 28, 32. The concave first edge
along the wall 26 preferably is a mirror image of the concave first
edge along the wall 30. Similarly, the convex first edge along wall
28 preferably is a mirror image of the convex first edge along wall
32. In addition, as can be seen best in FIG. 1B, the concave
portion 40 of the first edge 38 of wall 26 preferably terminates
before it reaches either end of the wall 26 to create flattened
portions 41; the same is true of the concave portion of wall 30.
These flattened portions 41 add stability to the cutting guide 20
when it is positioned against the vertebral body, as later
described. Further, although the concave portions 40 and convex
portions 42 may be smooth surfaces, they also may be formed by a
plurality of adjacent straight surfaces. For example, as can be
seen in FIG. 1C, the convex portion 42 preferably is a smooth,
curved surface; however, it will be understood that the convex
portion can be formed by a plurality of straight segments 41', as
shown, for example, in FIG. 1D.
[0070] A plurality of holes 44 pass through the cutting guide 20
from edge 36 to edge 38. These holes 44 are adapted to receive
fasteners 48, as shown in FIG. 8, to secure the cutting guide 20 to
the vertebral body 24. Although the holes 44 can be positioned
anywhere along edges 36, 38, it is preferable that they be
positioned to extend through walls 28, 32 having convex portions
42. In addition, although FIGS. 1A-1C show six holes 44, one of
ordinary skill in the art will understand that fewer or more holes
can be employed in the cutting guide 20 without departing from the
broadest scope of the invention. Moreover, in a cutting guide
having more than four holes 44, a surgeon need not position
fasteners in all holes, but, in fact, may only need fasteners in
two holes 44 to secure the cutting guide 20 to the vertebral body,
depending on the surface contour of the vertebral body. In one
preferred embodiment, three or four holes 44 would receive a
fastener 48.
[0071] Turning to FIGS. 2A-2D, there is shown a chisel guide 50 for
use in cutting bone of a vertebral body 24. The chisel guide 50 can
be used in combination with the cutting guide 20 to guide a chisel
62, or osteotome, as seen in FIG. 3B, toward the cortical bone 22
of the vertebral body 24. The chisel 62 then can cut through the
bone 22 to expose the inside of the vertebral body 24, as will be
later described in more detail. The chisel guide 50 includes a
first block member 54 to be positioned towards the vertebral body
24 and a second block member 52 connected to the first block member
54. Although the blocks 52, 54 may be separate pieces joined
together to form the chisel guide 50, they preferably are solid and
integrally molded or machined as one piece. The second block 52
preferably extends beyond the perimeter of the first block 54 in at
least one dimension to form a shoulder 56 with respect to the first
block 54. For example, the first block 54 has a first width W1, and
the second block 52 has a second width W2 greater than the first
width W1, thereby forming opposed shoulders 56 with respect to the
first block 54. In addition, the second block 52 can have a channel
58 formed in a top side 60 thereof. The channel 58 terminates at
the first block 54. The channel 58 may receive a projection 59 on a
chisel 62, as shown in FIG. 3B, when the chisel guide 50 is
positioned in the cutting guide 20.
[0072] Although the blocks 52, 54 can have approximately the same
height, they are vertically offset from each other, thereby
creating two ridges 76, 78. As later described in detail, the first
ridge 76, formed by part of the second block 52, is designed to
engage the flat edge 36 of the cutting guide 20. Similarly, the
second ridge 78, formed by part of the first block 54, serves as a
chisel guiding edge by abutting a surface 63 on the chisel 62 to
prevent the chisel 62 from penetrating too deep into the vertebral
body 24. In this way, the surface 63 can act as a safety stop.
[0073] The second block 52 of the chisel guide 50 has two side
surfaces 68, 70, a bottom surface 72, and two connecting surfaces
64, 66 extending between each side surface 68, 70 and the bottom
surface 72, as shown most clearly in FIGS. 2C and 2D. The
connecting surfaces 64, 66 not only make it easier to position the
chisel guide 50 in the cutting guide 20, they also provide the
surgeon with access to at least one hole 44 formed in edge 36 so
that fasteners 48 can be driven through the holes 44 in the edge 36
while the chisel guide 50 is positioned in the cutting guide cavity
34, as shown in FIG. 3A. Accordingly, although the connecting
surfaces 64, 66 are shown as being slanted, they could be any shape
which provides sufficient access to holes 44 in edge 36; for
example, the surfaces 64, 66 could be curved.
[0074] FIGS. 3A-3C show a combination of the cutting guide 20 and
the chisel guide 50, how they engage each other, and how the chisel
62 can be inserted and guided into the cutting guide 20 by the
chisel guide 50. The first block 54 of the chisel guide 50 is
designed to fit in the cavity 34 of the cutting guide 20 so that
the shoulders 56 and the ridge 76 of the second block 52 abut the
flat edge 36 of the cutting guide 20. The shoulders 56 are designed
to abut two opposite walls of the cutting guide 20 whenever the
chisel guide 50 is inserted in the cutting guide 20. When so
positioned, the cutting guide 20 and the chisel guide 50 create a
restricted passage 80 for insertion of the chisel 62; the passage
80 is between a first side of the first block 54 and an inner
surface of the sidewall of the cutting guide 20.
[0075] The passage 80 is sized so that a blade 82 of the chisel 62
can pass therethrough in a controlled direction, as shown in FIG.
3C. The chisel 62 can have a projection 59 on one side 61 thereof
which slidably engages the channel 58 in the top side 60 of the
second block 52. When the cutting guide 20 is affixed to a
vertebral body 24, and the chisel guide 50 is positioned in the
cavity 34 of the cutting guide 20 to create the passage 80, a
surgeon can insert chisel blade 82 into the passage 80 to make a
straight cut into the bone 22 of the vertebral body 24. The chisel
can be inserted into the restricted passage 80 until the surface 63
on the chisel 62 abuts the second ridge 78 on the first block 54.
In this position, a first cut can be made into the vertebral body
24 along a first wall 26 of the cutting guide 20.
[0076] After the first cut is made, the chisel guide 50 can be
rotated 180 degrees from the orientation shown in FIG. 3A to create
a passage for the chisel blade 82 adjacent an opposite wall 30 of
the cutting guide 20, at which a second cut can be made into the
vertebral body 24. The second cut is substantially parallel to the
first cut. In this regard, the first width W1 of the first block 54
preferably is less than or equal to the inner distance between the
walls 28, 32.
[0077] As mentioned above, the cutting guide 20 can be rectangular
or square. If the cutting guide 20 has a rectangular shape, as
shown in FIG. 1A, then the surgeon can use a second chisel guide to
make cuts along walls 28, 32. The first block member of this second
chisel guide has a width less than or equal to the inner distance
between the walls 26, 30. Using this second chisel guide, the
surgeon can make third and fourth cuts substantially perpendicular
to the first and second cuts along the inner edges of walls 28, 32.
As a result, a substantially rectangular cut 202 can be made in a
controlled manner into the vertebral body 24. This surgical
technique will be described in more detail in connection with FIGS.
9A and 10.
[0078] If the cutting guide is square in shape, after the first and
second cuts the surgeon can rotate a single chisel guide 90 degrees
clockwise from the orientation of FIG. 3A, to make a third cut into
the vertebral body along wall 28. Further, after the third cut, the
surgeon can rotate the chisel guide 180 degrees, to make a fourth
cut into the vertebral body along wall 32.
[0079] FIGS. 4A-4C show a reamer 90 and a rotatable shaft 92 for
removing or coring bone out of the vertebral body. A first end 96
of the shaft 92 has a plate 98 affixed thereto. On the plate 98,
there are a plurality of pins 100 and preferably a boss 102 that
face away from a second end 94 of the shaft 92. The boss 102, which
is preferably cylindrical, can matingly engage a corresponding bore
110 in the reamer 90, as later described. The second end 94 of the
shaft 92 is adapted to engage a power source, such as a hand or
power drill, which is adapted to rotate the shaft 92.
[0080] Referring to FIGS. 4B and 4C, the reamer 90, which is
preferably circular in cross section, includes a plate 104 at a
first end 106. The plate 104 is adapted to engage the plate 98 on
the shaft 92. Specifically, the plate 104 has a front surface 105
with a plurality of channels 108 and a bore 110 therethrough. The
bore 110 passes through a central portion of the plate 104. The
channels 108 are adapted to receive the pins 100 of plate 98, and
the bore 110 is adapted to fit over the boss 102, to mount the
reamer 90 to the shaft 92. The pins 100 are tight-fit into the
channels 108 so that when the shaft 92 is rotated, for example, by
a drill, the reamer 90 is rotated in unison with the shaft 92. In
addition, the reamer 90 has a collection space 112 for capturing
bone shavings 118 as the reamer rotates and removes bone from the
vertebral body 24.
[0081] To remove bone from the vertebral body 24, the reamer 90
includes at least one cutting member 114 positioned at a second,
bone engaging end 116 of the reamer 90. The cutting member 114
preferably comprises a plurality of blades. The blades 114 extend
angularly from the bone engaging end 116 of the reamer 90, as seen
in FIG. 4A. A slot 120, which preferably is rectangular, is
positioned adjacent each blade 114. When a surface 117 of the bone
engaging end 116 of the reamer 90 is positioned adjacent cancellous
bone and rotated, the blades 114 shave through the bone and the
interior of a vertebral body 24. The bone shavings 118 pass through
the slots 120 and into the collection space 112. The shavings 118
can be collected and stored in the collection space 112 for later
use as needed. The surface 117 of the bone engaging end 116 is flat
except for blades 114 and slots 120.
[0082] As shown in FIGS. 4A-4C, the reamer 90 has a cylindrical
portion 109 which is adapted to be journalled into the cavity 34 of
the cutting guide 20, as shown in FIG. 11. The cylindrical portion
109 includes a contact surface 107 on the plate 104. The contact
surface 107 is on the side opposite the surface 105 that abuts the
plate 98 at the first end 96 of the shaft 92. When the cylindrical
portion 109 is inserted to the maximum depth to which the surgeon
should bore into a vertebral body 24, the contact surface 107 abuts
the second edge 36 of the cutting guide 20. The contact between the
plate 104 and the second edge 36 of the cutting guide 20 prevents
the surgeon from inadvertently reaming too far into the vertebral
body 24.
[0083] Referring now to FIGS. 5A-5C and 6A-6C, a cutting implement
that can be mounted to a compressor 160 or a distractor 500 in
accordance with the invention will now be described. The cutting
implement can be made to cut through an endplate (208 in FIG. 13)
of a vertebral body 24 and the nucleus pulposus of the
intervertebral disc 200 adjacent the vertebral body 24. Turning
first to FIGS. 5A-5B, there is shown an example of a cutting
implement which may be used in conjunction with the compressor 160
or distractor 500. Specifically, the exemplary cutting implement is
in the form of an endplate and nucleus cutter 130 having a
substantially circular sidewall 132 that terminates in a cutting
edge 134. The diameter of the substantially circular sidewall will
depend on the size of the nucleus pulposus to be removed. The
maximum diameter of the sidewall should be greater than the minimum
diameter of the nucleus pulposus and/or the diameter of the
prosthesis 220, 230 to be implanted. In addition, the cutting edge
134 can be smooth or, alternatively, serrated. The cutting edge 134
may be thinner than the sidewall 132 and may be tapered to a sharp
end 137. In addition, the endplate and nucleus cutter 130 has a
base 136 to which the sidewall 132 is attached. The base 136 and
the sidewall 132 define an essentially hollow cylindrical cavity
138. Extending from the base 136 in the cavity 138 is a projection
140 that contains a screw hole 188 adapted to receive a screw 142.
Although the projection 140 may extend only part way into the
cavity 138, it can extend beyond the sharp edge 137, as shown in
FIG. 5B. In the embodiment of FIG. 5B, the tip of projection 140
can be used to create a notch in an endplate, thereby bracing the
endplate and nucleus cutter 130 relative to the endplate. The
projection 140 then can serve as an axis of rotation. This bracing
effect enables a surgeon to cut through the endplate with the sharp
end 137 of the endplate and nucleus cutter 130 without risk that
the endplate and nucleus cutter 130 will inadvertently slide from
its proper position relative to the endplate surface.
[0084] An alternative embodiment of the endplate and nucleus cutter
130 is shown in FIG. 5C. The only difference between this
embodiment and the one shown in FIG. 5B is that the projection 140'
is cylindrical in shape and has a concave end. An advantage of
employing the embodiment of FIG. 5C with the embodiment of FIG. 5B
on a single compressor 160 is that when the sharp edges 137 of the
two endplate and nucleus cutters 130 approach each other, the tip
of the projection 140 will be partially journalled into the concave
end portion of the projection 140'.
[0085] With respect to FIG. 6A, the compressor 160 includes a
handle 162, which has two scissor-like members 164, 166 pivotally
joined at a pivot 167, such as a pin. The first member 164 is
joined at a pin 168 to a first arm 170. A channel 172 is located in
the first arm 170, and a projection pin 174 extending from the
second member 166 can slide in the channel 172. Similarly, the
second member 166 is joined at a pin 176 to a second arm 178. The
second arm 178 is substantially parallel to the first arm 170. In
addition, like the first arm 170, the second arm 178 has a channel
180 in which a projection pin 182 extending from the first member
164 can slide.
[0086] In the preferred embodiment shown in FIG. 6A, an endplate
and nucleus cutter 130 is attached to an end portion 186 of the
first arm 170 and faces toward the second arm 178. Similarly, an
endplate and nucleus cutter 130 is attached to an end portion 186
of the second arm 178 and faces toward the first arm 170 (i.e.,
toward the other endplate and nucleus cutter 130).
[0087] When the handle 162 is compressed by pressing members 164,
166 toward each other, the projection pins 174, 182 slide in their
respective channels 172, 180, and the first and second arms 170,
178 move toward each other in parallel. In addition, as the first
and second arms 170, 178 move toward each other, the arms 170, 178
maintain their approximately parallel orientation. Moreover, as the
first and second arms 170, 178 approach each other in parallel, the
endplate and nucleus cutters 130 also approach each other.
Preferably, the endplate and nucleus cutters 130 on the first and
second arms 170, 178 share a common central axis so that, when the
handle 162 is fully compressed, the cutting edges 134 of the
endplate and nucleus cutters 130 on the first and second arms 170,
178 contact each other.
[0088] The endplate and nucleus cutters 130 can be either fixedly
mounted or rotatably mounted to the arms 170, 178 of the compressor
150. When the endplate and nucleus cutters 130 are fixedly mounted,
the surgeon can manually rotate the cutters 130 by swinging the
handle 162 of the compressor 150 side-to-side. This side-to-side
motion, combined with compression of the handle 162, enables the
cutting edges 134 to cut through the endplate and nucleus pulposus
of the damaged disc. Alternatively, the endplate and nucleus
cutters 130 may be rotatably mounted to the compressor. A motor or
other drive source can be connected to the cutters 130 to rotate
them relative to the arms 170, 178 of the compressor 150.
[0089] The compressor 160 is shown having two endplate and nucleus
cutters 130 thereon which face inward and toward each other. The
compressor 160 is used, as later explained in detail, when a
surgeon wants to implant a prosthetic device 220 having two
fixation members 222, one of which is to go into a vertebral body
24 above a problematic disc 200 and the other of which is to go
into the vertebral body 24 below the problematic disc.
[0090] In some situations, however, the surgeon needs to implant
only one fixation member 222, for example, as shown in FIG. 19B,
and as will be described below. In such situations, a distractor
500, which has one outwardly facing endplate and nucleus cutter 130
is preferred. FIG. 6B shows a distractor 500 having one endplate
and nucleus cutter 130 on a first arm 514 which faces outward and
away from a second arm 510. Similarly, an outwardly facing plate
540 is rotatably attached to the second arm 510 by means of an axle
542. The plate 540 is designed to be placed against an endplate in
a vertebral body and to remain immobile relative thereto. As the
endplate and nucleus cutter 130 of the distractor 500 is either
manually rotated by the surgeon (in an embodiment where the
endplate and nucleus cutter 130 is fixedly mounted to the
distractor 500) or rotates as a result of a motor applied thereto
(in an embodiment where the endplate and nucleus cutter 130 is
rotatably mounted to the distractor 500), the endplate and nucleus
cutter 130 will cut through one endplate in a vertebral body 24,
while the plate 540 remains pressed against the other endplate in
the vertebral body 24. The plate 540 does not abrade the vertebral
body against which it is placed because it does not rotate with
respect to that endplate.
[0091] The distractor 500 has two scissor-like members 502, 504
which together form a handle 506. The scissor-like members 502, 504
are rotatably attached to one another by a pin 518. In addition,
the first scissor-like member 504 is rotatably connected to the
first arm 514 by means of a pin 522. A projection pin 526 extending
from the first scissor-like member 504 is adapted to slide in a
slot 508 in the second arm 510. Similarly, the second scissor-like
member 502 is rotatably connected to the second arm 510 by means of
a pin 520. Further, a projection pin 524 extending from the second
scissor-like member 502 is adapted to slide in a slot 512 in the
first arm 514.
[0092] When the handle 506 of the distractor 500 is compressed, the
handle members 502, 504 pivot with respect to each other at pin
518, thereby correspondingly increasing the distance between the
projection pins 524, 526. As the distance between the projection
pins 524, 526 increases, the pins slide forward in their respective
slots 512, 508. Simultaneously, the distance between the rotating
pins 522, 520 and hence the distance between the first and second
arms 514, 510 increases. In this manner, by compressing the handle
506, a surgeon can produce parallel distraction of the arms 510,
514 to increase the distance between the endplate and nucleus
cutter 130 and the plate 540.
[0093] When the arms 514, 510 of the distractor 500 are inserted
into a cavity 206 in a vertebral body 24 and the handle is
subsequently compressed, the plate 540 will move in one direction
to contact the endplate 208 of the vertebral body 24, whereas the
endplate and nucleus cutter 130 will move in an opposite direction
to contact the other endplate 208 of the vertebral body 24.
Continued compression of the distractor 500 and rotation of the
endplate and nucleus cutter 130 will force the cutter 130 through
the endplate 208 and nucleus pulposus of the intervertebral disc
200 adjacent thereto.
[0094] Various methods exist by which an endplate and nucleus
cutter can be connected to an arm 170, 510 of a compressor 160 or
distractor 500, respectively. For example, as shown in FIGS. 5B and
6C, the head 148 of the screw 142 is contained within a connective
plate 146, which forms part of an arm 170, 178 of the compressor
160 or an arm 510, 514 of the distractor 500. The threaded portion
150 of the screw 142 passes through a spacer 144 and the base 136
and terminates in the projection 140. The connective plate 146 has
a hole 184 through which the threaded portion 150 of the screw 142
passes; the diameter of the hole 184 in the connective plate 146 is
smaller than the diameter of the head portion 148 of the screw. The
height of the head portion 148 is approximately the same as that of
a recess 158 in plate 146, thereby allowing the head portion 148 to
sink into the connective plate 146, as shown in FIG. 5B.
[0095] The preceding discussion provides one way in which the
endplate and nucleus cutter 130 can be fixedly mounted to the end
portion 186 of the arm of a compressor 160 or a distractor 500.
However, those of ordinary skill in the art will understand that
the endplate and nucleus cutter 130 can be mounted to the end
portion 186 in other ways. For example, in one preferred method,
which is more permanent and integral in nature, the endplate and
nucleus cutter is attached to the end portion 186 by riveting or
otherwise suitably fastening the base 136 directly to the end
portion 186, without use of a connective plate 146 or a spacer
144.
[0096] Moreover, the screw 142 could be adapted to be connected to
(or be part of) a rotatable shaft which, in turn, is connected to a
motor, such as a drill, to provide automatic rotation of the
endplate and nucleus cutter 130. In this manner, the endplate and
nucleus cutter 130 can be mounted so that the connective plate 146
can rotate independently of the compressor 160 or distractor 500
(if driven, for example, by a motor, not shown). Rotation of the
connective plate 146 will cause a corresponding rotation of the
endplate and nucleus cutter 130 attached thereto. Rotational
friction can be avoided due to a gap 152 between the plate 146 and
the base 136 generated by the spacer 144. Moreover, if the two
endplate and nucleus cutters 130 of FIG. 6A are mounted to rotate,
they can share generally the same axis of rotation.
[0097] Finally, it should also be readily apparent to one of
ordinary skill in the art that the endplate and nucleus cutter 130
could have a cutting surface similar to the surface 117 of the bone
engaging end 116 of the reamer 90 shown in FIGS. 4A-4C.
[0098] The preceding discussion, provided a general description of
how the endplate and nucleus cutter 130 can be attached to the
compressor 160 and distractor 500. A detailed description follows.
To attach the endplate and nucleus cutter 130 to the compressor
160, the spacer 144 is positioned on the side of the arm 170, 178
from which the endplate and nucleus cutter 130 is to project. The
spacer hole 154 is aligned with the hole 184 through the connective
plate 146. The endplate and nucleus cutter 130 is then centrally
positioned on top of the spacer 144 so that hole 188 in the
projection 140 is aligned with both the hole 154 in the spacer 144
and the hole 184 in the connective plate 146. The threaded portion
150 of screw 142 is then inserted through the hole 184 in the
connective plate 146 and the hole 154 in the spacer 144 until the
threaded portion 150 engages a mutually engaging threaded portion
156 of the hole 188. By turning the screw 142, the threaded portion
150 of the screw 142 engages the threaded portion 156 of the hole
188, thereby holding the endplate and nucleus cutter 130 onto the
arm 170. In addition, the head portion 148 of the screw 142 is
received by the recess 158 in the connective plate 146, thereby
minimizing height H. Various alternative methods may be used to
attach the endplate and nucleus cutter 130 to the arms 170, 178 of
a compressor 160; however, the height H (as shown in FIG. 6C)
should be less than the height of the cavity 206 formed in
vertebral body 24, as later described.
[0099] Connecting the endplate and nucleus cutter 130 to the
distractor 500, as shown in FIG. 6B, is readily achieved by
inverting the orientation of the endplate and nucleus cutter of
FIG. 6A. If this orientation is chosen, a recess, similar to the
recess 158 formed on the side of the arm 170 shown in FIG. 6C
(i.e., adapted to receive the head portion 148 of the screw 142)
should be formed on the other side of the arm 170. However, as both
the first and second arms 514, 510 of the distractor will be
inserted into the same cavity 206, the height (H) of the first arm
514 (with the endplate and nucleus cutter 130 attached thereto)
plus the height (X) of the second arm 510 (with the plate 540
attached thereto) must be less than the height of the cavity 206 in
the vertebral body 24.
[0100] In mounting the endplate and nucleus cutter 130 to create
the embodiment shown in FIG. 6B, the surgeon must place the spacer
144 on the opposite side of the arm 170 as that shown in FIG. 6C.
When this is completed, the screw 142 can be journalled through a
hole 184 in the arm 514 and through the hole 154 in the spacer 144,
in a manner similar to that of the embodiment shown in FIG. 6C. The
threaded portion 150 of the screw 142 may then engage the
correspondingly threaded portion 156 in the projection 140, thereby
holding the endplate and nucleus cutter 130 against the arm
514.
[0101] It will be understood that an endplate and nucleus cutter
130 can be mounted to devices having a configuration different than
the compressor 160 and distractor 500. For example, an endplate and
nucleus cutter 130 can be attached to an end of a single arm, and a
surgeon can grip the opposite end of the single arm to position the
endplate and nucleus cutter 130 appropriately to cut through the
endplate and the nucleus pulposus of a damaged disc. The single arm
can be bent to provide additional leverage.
[0102] After a cavity is formed in the intervertebral disc 200 by
either the compressor 160 or the distractor 500, an appropriate
prosthetic device is implanted in the cavity. The implanted device
can include two fixation members 222 and a compressible member 224,
as shown in FIG. 13, or, in an alternative embodiment, the
implanted device 230 can include a single fixation member 222 and a
compressible member, as shown in FIG. 18. Once the implanted device
is in place, the surgeon must restore the intervertebral distance,
i.e., the distance between two adjacent vertebrae; this is achieved
by tensioning the implanted device. That is, the load applied by
the implanted device between the vertebrae on opposite sides of the
excised, damaged intervertebral disc should be sufficient to
recreate the approximate disc height of a healthy intervertebral
disc. To do so, the surgeon can use a tensioner 300, as shown in
FIG. 7. The tensioner 300 can be used to measure the tension or
load applied to the compressible member 224 by the fixation
member(s) 222. That is, the tensioner 300 can be used to determine
when the fixation member 222 has been elongated sufficiently to
apply the proper force (or load) on the compressible member 224, as
will be more fully described in connection with FIG. 14.
[0103] The tensioner 300 shown in FIG. 7 includes first and second
arms 302, 304, each of which has a handle portion 306, 308 and a
separator portion 310, 312. The arms 302, 304 are connected by a
pivot pin 316, which separates the separator portions 310, 312 from
the handle portions 306, 308. Positioned on at least one (and
preferably both) of the separator portions 310, 312 is at least one
tension measuring element. The tension measuring element preferably
is a strain gage 314 comprised of resistors or other suitable load
cell devices. It should be understood, however, that the tension
measuring element may be a torque needle, a spring, a transducer
other than a strain gage, or other suitable device for measuring
tension. The strain gages 314 can be cemented, glued, or otherwise
fastened on the separator portions 310, 312. In a preferred
embodiment, the strain gages 314 are part of Wheatstone bridge
circuits. Leads from the strain gages 314 are connected by wires
318 to a circuit monitoring device 320 which can measure the
resistance and voltage across the gages 314.
[0104] When the handle portions 306, 308 of the tensioner 300 are
compressed, i.e., moved toward each other, the separator portions
310, 312, by means of the pivot pin 316, move away from each other.
If the separator portions 310, 312, when moved away each other,
contact a generally immobile surface, continual compression of the
handle portions 306, 308 will cause the separator portions 310, 312
to bend slightly in the vicinity of the strain gages 314. As the
separator portions 310, 312 bend, the strain gages 314 are
stretched or compressed, as appropriate, thereby changing the
resistance of the resistors. As the resistance changes, the voltage
across the strain gages 314 correspondingly changes, where the
current in the circuit is constant. By monitoring the voltage, a
surgeon can determine when a predetermined load has been reached,
the voltage being representative of the predetermined load.
[0105] A method of creating a cavity in a vertebral body will now
be described with respect to FIGS. 8-16. FIG. 8 shows the anterior
aspects of two vertebral bodies 24 separated by an intervertebral
disc 200. A cutting guide 20 is positioned on a side surface of the
upper vertebral body 24 such that the walls 26, 30 having the
concave edges are substantially parallel to the vertebral body
endplates 208. The concave and convex portions 40, 42 of the
cutting guide 20 are shaped so as to fit against the curved surface
of the vertebral body 24. As the surface geometry of vertebral
bodies varies somewhat between patients, typically either a
three-point or four-point contact is achieved between the cutting
guide 20 and the vertebral body 24.
[0106] As the cutting guide 20 is held against the vertebral body
24, a drill bit is journalled through one of the holes 44 in the
cutting guide 20, and a hole is drilled into the vertebral body 24.
A fastener 48 (e.g., drill bit, screw, nail, or pin) is then
journalled through the hole 44 in the cutting guide and is received
by the hole drilled into the vertebral body 24. If the fastener 48
is, for example, a screw, the screw would be turned into the hole
in the vertebral body 24 by conventional means, thereby securing
the cutting guide 20 to the vertebral body 24. If the fastener 48
is a pin or a nail, it can be driven into the vertebral body 24 by
tapping with a hammer or similar device. This process is then
repeated for other holes 44 in the cutting guide 20 until the
cutting guide is secured to the vertebral body 24. As a result, a
plurality of fasteners 48 hold the cutting guide 20 onto the
vertebral body 24. Although the figures disclose the use of four
fasteners 48, any suitable number of fasteners can be used.
[0107] By journalling the fasteners 48 through the holes 44, the
cutting guide 20 can slide off the fasteners 48 while the fasteners
remain secured to the cortical bone 22, provided no part of the
fasteners 48 has a diameter larger than the diameter of the holes
44. This ability to slide the cutting guide 20 facilitates removal
of the cutting guide 20 (for purposes of removing a rectangular
section 204 of cortical bone 22, as later described), while
preserving the ability to reposition quickly the cutting guide 20
on the vertebral body 24 (for purposes of reaming the vertebral
body 24, as later described). In addition, to avoid sliding the
cutting guide 20 completely off of the fasteners 48, it is possible
to use fasteners 48 having a length much greater than the
cumulative depth of the cutting guide 20 and the holes drilled into
the cortical bone. Using fasteners 48 of this nature will allow the
surgeon to slide the cutting guide 20 away from the vertebral body
24 to a sufficient distance at which the cortical bone 22 of the
vertebral body 24 can be accessed. In this regard, the surgeon can
remove a generally rectangular section 204 of cortical bone 22 and
then quickly and easily reposition the cutting guide 20 on the
vertebral body 24, as is necessary before the vertebral body's 24
interior cancellous bone may be removed by reamer 90, as later
described.
[0108] Turning now to FIG. 9A, there is shown a vertebral body 24
having a cutting guide 20 affixed thereto. Positioned in the
cutting guide 20 is a chisel guide 50 and a blade 82 of a chisel
62. The width W1 of the first block member 54 is less than or equal
to the inner distance between two sidewalls 28, 30 of the cutting
guide 20. The shoulders 56 and the ridge 76 on the second block 52
of the chisel guide 50 rest against the flat edge 36 of the cutting
guide 20. In addition, the blade 82 of a chisel 62 is channeled
through the passage 80 created between the cutting guide 20 and the
chisel guide 50.
[0109] Once the blade 82 is positioned against the cortical bone 22
of the vertebral body 24, the free end of the chisel 60 can be
tapped to drive the blade 82 into the cortical bone 22. In this
manner, the chisel blade 82 punctures through the cortical bone 22
and cuts into the cancellous bone in the interior of the vertebral
body 24, thereby forming a first cut. In a preferred embodiment,
when the blade 82 of the chisel 62 is driven into the vertebral
body 24 to a maximum allowable depth, the surface 63 on the chisel
62 abuts the second ridge 78 on the first block 54, thereby
preventing the blade 82 from being driven further into the
vertebral body 24. In this fashion, the surface 63 can act as a
safety stop.
[0110] Due to the controlled manner of supporting the chisel 62
(i.e., by using the chisel guide 50), the surgeon can ensure a
nearly straight cut through the bone 22 of the vertebral body 24.
The nearly straight cut occurs along one side of an inside
perimeter of the cavity 34 of the cutting guide 20. In addition,
preferably fluoroscopy or radiographs are used to ensure that the
transverse cuts made into and through the bone (to the depth
limited by the surface 63 on the chisel 62 abutting the second
ridge 78 on the first block 54) are generally parallel to the
endplates 208 of the vertebral body 24.
[0111] Once the first transverse cut is made, the surgeon removes
the chisel guide 50 from the cutting guide 20, rotates it 180
degrees toward an opposite wall 30, slides it back into the cutting
guide 20, and creates a second cut into the cortical bone 22 of the
vertebral body 24. This rotation will allow the surgeon to ensure
that the cut made by the blade 82 of the chisel 62 is approximately
parallel to the first cut.
[0112] After the first and second cuts are complete, the surgeon
removes the chisel guide 50 and, if the cutting guide 20 is
rectangular, inserts a second chisel guide. The width of the first
block member of this second chisel guide is less than or equal to
the inner distance between the upper and lower walls 26, 30 of the
cutting guide 20. The second chisel guide is inserted into the
cutting guide 20 at an orientation 90 degrees from the chisel-guide
orientation shown in FIG. 3A, to create a passage for the chisel
blade that is substantially perpendicular to the first and second
cuts. In this position, a third cut can be made along wall 28.
Next, the second chisel guide is rotated 180 degrees, in order that
a fourth cut can be made along wall 32. The four completed cuts
form a substantially rectangular cut 202 into the cortical bone 22
along an inner perimeter of the cutting guide 20.
[0113] Alternatively, the surgeon can chisel along the inner
perimeter of the cutting guide 20 without using a chisel guide 50.
Moreover, if a square cutting guide is employed, then only a single
chisel guide would be necessary; after a first cut is made, that
is, the chisel guide could be rotated 90, 180, and 270 degrees from
its first orientation in the square cutting guide to make second,
third, and fourth cuts, respectively, into the vertebral body
24.
[0114] FIG. 9B shows an alternative manner by which cuts can be
made in the cortical bone 22 of the vertebral body 24. Rather than
using a chisel 62 (with or without a chisel guide 50), the surgeon
can use a sagittal saw 46 to make the cut into the cortical bone
22. The surgeon can also use the sagittal saw 46 to make
preliminary shallow cuts in the cortical bone 22 and, afterward,
use the chisel guide 50 and/or chisel 62 to make final cuts.
[0115] As shown in FIG. 10, after cut 202 is made in the cortical
bone 22, the cutting guide 20 is either removed or withdrawn along
the fasteners 48 to a distance sufficient to allow access to the
cortical bone 22 and the rectangular cut 202. In either case, some
or all of the fasteners 48 can remain in the cortical bone 22 of
the vertebral body. Once the cutting guide 20 is removed or
withdrawn, section 204 of cortical bone 22 (defined by cut 202) is
removed using an osteotome, thereby exposing the cancellous bone in
the interior of the vertebral body 24. After the section 204 is
removed, the cutting guide 20 is re-affixed to the vertebral body
24 by journalling the fasteners 48 projecting from the vertebral
body 24 through the holes 44 in the cutting guide 20, as shown in
FIG. 11.
[0116] Once the cutting guide 20 is re-affixed to the vertebral
body 24, the surgeon can use a reamer 90 to drill a cavity 206 in
the vertebral body 24 as shown in FIG. 11. The bone which is
removed to form the cavity 206 is cut into bone shavings 118 by
cutting implement 114 on the second end 116 of the reamer 90. The
shavings 118 pass through the slots 120 in the end 116 of the
reamer 90 and into the cavity 112 in the reamer 90. When the
vertebral body cavity 206 is both wide enough and deep enough to
accept a first fixation member 222 of a prosthetic device 220 which
will rest in a cavity 206 of FIG. 12A, such as shown in FIG. 13,
the surgeon stops reaming and removes the shavings 118 from the
cavity 112 in the reamer 90. The shavings 118 can be used after
implantation of a prosthetic device 220 to promote bone ingrowth
into the prosthetic device 220, as later described. The first
fixation member 222 then can be temporarily placed in the cavity
and centered using fluoroscopy. If the first fixation member 222
cannot be properly centered (i.e., if the cavity 206 is slightly
too mall), the surgeon can use a mechanical burr or curette to
remove sufficient bone to allow the first fixation member 222 to
fit within the cavity 206. The fixation member 222 then is removed
from the cavity 206.
[0117] After the cavity 206 is formed in the upper vertebral body
24, the surgeon goes through the same process with respect to the
lower vertebral body 24 to form a cavity 206 therein, as shown in
FIG. 12A. Once the two cavities 206 are created, the fasteners 48
can be removed from the cortical bone 22 of the vertebral bodies
24.
[0118] After the fasteners 48 are removed, a compressor 160, having
cutting implements on each of its first and second arms 170, 178,
is adjusted so that the cutting implements can simultaneously pass
into the cavities 206 in the vertebral bodies 24. The cutting
implements preferably are endplate and nucleus cutters 130. Prior
to compression of the compressor 160, fluoroscopy can be used to
ensure that the cutting implements are centered in the cavities 206
in the vertebral bodies 24.
[0119] Where endplate and nucleus cutters 130 are used as the
cutting implements, upon compression of the handle 162, as shown in
FIG. 12B, the two arms 170, 178 and the endplate and nucleus
cutters 130 are brought towards each other. By compressing the
handle 162, the generally circular cutting edges 134 of the
endplate and nucleus cutters 130 move in an axial direction and cut
through the endplates 208 (shown cut-through in FIG. 13) of the
respective vertebral bodies 24 and then through the nucleus
pulposus of the intervertebral disc 200 separating the vertebral
bodies 24; the annulus fibrosis of the disc 200 remains intact.
When the endplate and nucleus cutters 130 contact each other in a
central portion of the disc 200, compression is stopped.
[0120] To facilitate cutting, the endplate and nucleus cutters 130
can be manually rotated during compression; that is, the compressor
160 can be twisted side-to-side during compression. Or, if the
endplate and nucleus cutters 130 are mounted for mechanical
rotation to the compressor arms 170, 178, the cutters 130 can be
mechanically rotated during compression to facilitate cutting.
[0121] After the compressor 160, and its dual endplate and nucleus
cutters 130, are removed from the vertebral bodies 24, the portions
of the endplates 208 and the intervertebral disc 200, through which
the generally circular cutting edges 134 of the endplate and
nucleus cutters 130 were forced, are removed, thereby creating a
generally cylindrical channel 212 from the lower vertebral body 24
through the intervertebral disc 200 and to the upper vertebral body
24. The channel 212, which is formed, in part, by the cavities 206
in the vertebral bodies 24, will hold the entire prosthetic device
220 as shown in FIG. 13.
[0122] A suitable prosthetic device for implantation in channel 212
is described in U.S. Pat. No. 5,827,328, incorporated herein by
reference in its entirety. It is preferable that all parts of the
prosthetic device 220, 230 be formed or machined from a
biocompatible material, such as cobalt-chrome alloy. Initially, a
compressible member 224 of an appropriate size and with appropriate
angulation is selected based on the size and location of the disc
200 to be replaced and on the size of the patient. More
specifically, choosing the proper compressible member 224 will
depend both on the size of the annulus fibrosis in the particular
disc 200 (which had its nucleus pulposus removed) and on the
approximate lordosis of the motion segment level of the disc 200
that is being replaced. Once the compressible member 224, which may
include a series of springs, is selected, it is inserted into the
cavity 206 in one of the vertebral bodies 24. The compressible
member 224 then is pushed into the hole in the intervertebral disc
200 that originally contained the nucleus pulposus. The
compressible member 224 then is oriented so as to maintain lordosis
(i.e., the thicker portions of the component 224 are placed
anteriorly, as shown in FIG. 13).
[0123] After the compressible member 224 is in place, a first
fixation member 222 is positioned in one of the cavities 206 in the
vertebral bodies 24. The fixation member 222 is then connected to
the compressible member 224, and the lordotic alignment is
rechecked. Next, a second fixation member 222 is positioned in the
cavity 206 in the other vertebral body 24 and is connected to the
other side of the compressible member 224, thereby completing
implantation of the prosthetic device 220.
[0124] Each of the fixation members 222 has an upper plate 260 and
a lower plate 262. A plurality of vertically adjustable struts 264
are positioned between the upper and lower plates 260, 262. When
the struts 264 are unlocked, their height can be easily changed.
When the struts 264 are locked, their height remains constant.
[0125] Once the fixation members 222 are properly positioned in the
vertebral bodies 24, the tension or load experienced by the
compressible member 224 of the prosthetic device 220 needs to be
adjusted to optimize the normal loading and compression (i.e., the
functionality) of the particular disc 200 being replaced. To do so,
the surgeon inserts the separator portions 310, 312 of a tensioner
300 into the upper one of the fixation members 222. Upon
compression of the tensioner's handle portions 306, 308, the
separator portions 310, 312 move away from each other into contact
with the upper and lower plates 260, 262, respectively, forcing the
plates 260, 262 toward the endplates 208 of the vertebral body 24.
In this manner, the tensioner 300 elongates the fixation member 222
until a proper elongation distance between the plates 260, 262 is
achieved. The separator portions 310, 312 preferably are positioned
so that their tips contact the center of the plates 260, 262. As
the plates 260, 262 move away from each other, the unlocked struts
264 will increase in length. When the upper plate 260 contacts the
upper endplate 208 of the upper vertebral body, and the lower plate
262 contacts and encounters resistance from the compressible member
224, continual compression of the handle portions 306, 308 will
cause a slight bending in the tensioner's separator portions 310,
312.
[0126] As previously described, the slight bending of the separator
portions 310, 312 will deform the strain gages 314, thereby
changing their resistance which, in turn, changes the voltage
potential across the gages 314. By monitoring the change in voltage
caused when the separator portions 310, 312 are opened (closed),
and by amplifying and calibrating the voltage to known loads, a
surgeon can determine whether the fixation member 222 has been
suitably lengthened to properly tension, i.e., properly load, the
compressible member 224. More specifically, the surgeon can
calculate what load should be applied to a fixation member 222 to
cause a desired corresponding reactive force or load from the
compressible member 224; the more the surgeon expands the fixation
member 222, the greater the reactive force from the compressible
member 224. The voltage measured by the tensioner 300 is
representative of the load applied to the fixation member 222.
Thus, the surgeon uses the tensioner 300 to monitor the load
applied to the fixation member 222. When the applied load equals a
predetermined desired load, the surgeon knows that the fixation
member 222 has been lengthened or elongated the appropriate amount
to place the compressible member 224 under the proper degree of
tension.
[0127] When the fixation member 222 reaches the proper length, the
vertically adjustable struts 264 are locked, thereby maintaining
proper tension or load in the compressible member 224. After the
first fixation member 222 is properly lengthened, the same
procedure may be used to properly lengthen the other fixation
member 222 in the other vertebral body 24.
[0128] The struts 264 can be locked to maintain the proper length
of the fixation member 222, i.e., the proper elongation distance
between the upper and lower plates 260, 262, in a variety of ways.
For example, the struts can be configured for adjustment like a
crutch, that is, by having a hole through an outer casing and a
plurality of holes through an adjustable inner member. When the
inner member is adjusted to the proper height, a fastener can be
inserted through the hole in one side of the casing, through the
corresponding hole in the inner member, and then through the hole
in the other side of the casing. The fastener immobilizes the inner
member with respect to the casing and maintains the proper
elongation distance between the upper and lower plates 260,
262.
[0129] Clamps also can be used to maintain the proper elongation
distance between the plates 260, 262. The clamps are C-shaped in
cross section and have a length equal to the elongation distance.
The C-shaped cross section of the clamps leaves a slit or opening
along their length. The clamps also are resiliently flexible. When
the slit of a clamp is pressed against a strut, the slit widens so
that the clamp can be slid around the strut. Once around the strut,
the clamp returns to its initial shape. The clamps thus can be
positioned on the struts 264 to substantially surround the struts
264 and maintain the proper elongation distance between the plates
260, 262.
[0130] A tripod also can be used to maintain the proper distance
between the plates 260, 262. In this preferred method, the surgeon
selects a tripod of an appropriate height, that is, of a height
equal to the desired elongation distance, and slides it into the
fixation member 222. The surgeon then positions the legs of the
tripod on the lower plate 262, preferably against three struts 264,
and positions the top of the tripod against the upper plate
260.
[0131] After the length of the fixation members 222 is fixed (i.e.
by locking the struts 264 in each of the fixation members 222 when
the proper amount of tension is experienced by the compressible
member 224), the surgeon can use radiographs or fluoroscopy to
confirm that the prosthetic device 220 is properly positioned and
aligned. Once confirmed, the bone shavings 118 (bone graft) stored
in the cavity 112 of the reamer 90 are placed into the cavities 206
in the vertebral bodies 24, as shown in FIG. 15. In time, the bone
shavings 118 will induce new bone to grow in the vertebral bodies
24 during the healing process. It is also possible to place bone
cement, bone substitute, or bone morphogenic protein, rather than
bone shavings 118, into the cavities 206. In addition, it is
possible to use both bone cement combined with bone shavings
118.
[0132] As shown in FIG. 16, after the bone shavings 118 and/or the
bone cement are placed into the cavities 206 in the vertebral
bodies 24, the pieces 204 of cortical bone 22 are replaced in the
cuts 202 in the vertebral bodies 24 from which they came. The
pieces 204 can be fixed to the vertebral bodies 24 using
traditional methods, such as by a bone screw, plate, or bone
cement, thereby enclosing the cavities 206 containing the bone
shavings 118 and the prosthetic device 220.
[0133] The aforementioned describes one method by which to create a
cavity in an intervertebral disc. It is also possible, as shown in
FIGS. 17A and 17B, to use a distractor 500 of the type shown in
FIG. 6B to surgically implant a prosthetic device 230 through only
one vertebral body 24. Specifically, after a cavity 206 is created
in an upper (or lower) vertebral body 24 by a reamer 90 in the
manner previously discussed, the scissor-like members 502, 504 of a
distractor 500 are separated, thereby bringing the arms 510, 514
together. The arms 510, 514, having one outward facing cutting
implement thereon, preferably an endplate and nucleus cutter 130,
can then be inserted into the cavity 206.
[0134] When scissor-like members 502, 504 are compressed, the arms
514, 510 are separated, and the arm 514 having the endplate and
nucleus cutter 130 thereon is pushed against the endplate 208 that
is to be partially removed (to thereby provide access to the disc
200 below or above). As the handle 506 is compressed and, if
necessary, twisted, the endplate and nucleus cutter 130 can be
pushed downward (or upward) to cut through the endplate 208 of the
vertebral body 24 and into the nucleus pulposus of the
intervertebral disk 200 below (or above) the vertebral body 24.
During this cutting process, the plate 540 on the opposite arm 510
acts as a brace by pushing against the endplate 208 above (or
below) the endplate 208 through which the endplate and nucleus
cutter 130 is forced. When the distractor 500 is twisted side to
side, the plate 540 will remain fixed with respect to the endplate
208 against which it is positioned; this will prevent any
inadvertent shaving of bone from the endplate 208 against which the
plate 540 is positioned. In this manner, the endplate and nucleus
cutter 130 makes a generally circular cut through the endplate 208
and into the intervertebral disc 200 below (or above) the endplate
208.
[0135] Once the cut has been made, the distractor 500 and endplate
and nucleus cutter 130 attached thereto is removed from the cavity
206. The portion of the endplate 208 located within the generally
circular cut may then be removed. In addition, the nucleus pulposus
of the disk 200 can be removed using a commercially available soft
tissue ablator, thereby forming a well 232, the location of which
is shown in FIG. 18. The sides of the well 232 are formed by the
remaining disk annulus, and the bottom of the well 232 is formed by
non-removed disc 200 or by the endplate 208 of the vertebral body
24 below (or above) the intervertebral disc 200.
[0136] With respect to FIGS. 19A and 19B, after the well 232 is
formed, the endplate 208 below (or above) the intervertebral disc
200 may then be prepared to accept an alternative disc prosthetic
device 230. In this fashion, a rotating dome-shaped endplate reamer
400 can be used to abrade the endplate 208 on the side of the
intervertebral disc 200 opposite the vertebral body 24 which
accepted the distractor 500. The endplate reamer 400 creates a
dome-shaped indentation 402 in the endplate 208 which corresponds
to the shape of the side of the alternative disc prosthetic device
230 which will be positioned against it. In this manner, the
endplate 208 is shaped to be congruent with the prosthetic device
230. In addition, the reamer 400 can be used to roughen the bone
surface of endplate 208, which encourages bone ingrowth into the
prosthetic device 230.
[0137] Upon removal of the nucleus pulposus of the disk 200, a
prosthetic device 230 of the type shown in FIG. 18, i.e., a device
having a compressible member 224 and one expandable fixation member
222, can be inserted into the well 232 and the cavity 206 in the
vertebral body 24. Fluoroscopy is used to ensure that the device
230 is properly positioned, and a tensioner 300 is used, in the
manner previously described, to determine whether the device is
subject to the proper amount of loading. When the proper amount of
loading is applied, the struts 264 in the device will be locked, in
the manner previously described, to maintain the load. After the
prosthetic device 230 is properly inserted and subject to the
proper load, bone shavings 118 and/or bone cement can be poured
into the cavity 206 in the vertebral body 24, as previously
described. Finally, and similarly to the aforementioned manner of
closing a cavity 206 in a vertebral body 24, the previously removed
piece 204 of cortical bone 22 is repositioned and fused to the
vertebral body 24.
[0138] For both of the previously described methods in which the
nucleus pulposus of an intervertebral disk 200 is removed, it
should be readily apparent to one of ordinary skill in the art
these methods would be enhanced by a compressor 160 having or
working in conjunction with motors to cause the endplate and
nucleus cutters to rotate. Such rotation would make it easier for
the cutting edge 134 of an endplate and nucleus cutter 130 to cut
through both the endplate 208 of a vertebral body 24 and the
nucleus pulposus of an intervertebral disc 200.
[0139] It also will be understood that the cutting guide 20, the
chisel guide 50, the reamer 90, the compressor 160 and the
distractor 500 and their associated endplate and nucleus cutters
130, the facing plate 540 of the distractor 500, the tensioner 300,
the endplate reamer 400, and the chisel can be made of stainless
steel or other suitable material.
[0140] Apparatuses and methods for performing spinal surgery have
been described according to the present invention. Many
modifications and variations may be made to the apparatuses and
methods described and illustrated herein without departing from the
spirit and scope of the invention. Accordingly, it should be
understood that the apparatuses and methods described herein are
illustrative only and are not limiting upon the scope of the
invention.
* * * * *