U.S. patent application number 10/108249 was filed with the patent office on 2003-10-02 for anterior bone plate system and method of use.
Invention is credited to Cesarone, Morris D., Cirino, Dennis, Lauryssen, Carl, Sheeran, Danielle.
Application Number | 20030187443 10/108249 |
Document ID | / |
Family ID | 27804382 |
Filed Date | 2003-10-02 |
United States Patent
Application |
20030187443 |
Kind Code |
A1 |
Lauryssen, Carl ; et
al. |
October 2, 2003 |
Anterior bone plate system and method of use
Abstract
An anterior bone plate system is provided that promotes osseous
fusion and allows subsidence while restricting extension. The bone
plate system requires a minimum number of screws for securing the
plate onto bone, thus reducing the amount of osseous tissue damage
incurred by the bone structures to which they are attached. The
system is also simple to use and provides for independent screw
placement while incurring minimal soft tissue damage from lateral
retraction. A method for implementing the system is also
provided.
Inventors: |
Lauryssen, Carl; (Ladue,
MO) ; Cesarone, Morris D.; (Linwood, MA) ;
Cirino, Dennis; (Collierville, TN) ; Sheeran,
Danielle; (Westwood, MA) |
Correspondence
Address: |
NUTTER MCCLENNEN & FISH LLP
WORLD TRADE CENTER WEST
155 SEAPORT BOULEVARD
BOSTON
MA
02210-2604
US
|
Family ID: |
27804382 |
Appl. No.: |
10/108249 |
Filed: |
March 27, 2002 |
Current U.S.
Class: |
606/71 |
Current CPC
Class: |
A61B 17/8047 20130101;
A61B 17/7059 20130101; A61B 17/8042 20130101 |
Class at
Publication: |
606/71 |
International
Class: |
A61B 017/58 |
Claims
What is claimed is:
1. A bone plate system for the stabilization and rigid fixation of
bone segments, comprising: a bone plate having a first surface, a
second bone-contacting surface opposed to the first surface, and a
channel formed on the first surface extending lengthwise from one
end of the plate to an opposite end, the bone plate further
including a plurality of apertures extending through the channel,
each aperture having a predefined shape and size; a plurality of
screws capable of insertion into bone, each screw having a lower
threaded portion at one end and an open screw head at an opposite
end, the screw head having a complementary shape and size
sufficient to pass through one of the apertures; and a locking
mechanism for securing the bone plate onto the plurality of
screws.
2. The system of claim 1, wherein each aperture and each screw head
is oblong.
3. The system of claim 1, wherein the second bone-contacting
surface includes surface features.
4. The system of claim 3, wherein the surface features are
cleats.
5. The system of claim 1, wherein each screw has a self-tapping end
extending from the lower threaded portion.
6. The system of claim 1, wherein each screw head includes an upper
threaded portion configured to sit proud.
7. The system of claim 6, wherein the locking mechanism includes a
locking device configured for placement over the upper threaded
portion.
8. The system of claim 7, wherein the locking device is selected
from the group consisting of a nut, cam, wedge, and retaining
ring.
9. The system of claim 1, wherein the bone plate further includes a
flap on each side of the plate extending lengthwise from one end of
the plate to the opposite end, each flap further extending over at
least a portion of the channel.
10. The system of claim 9, wherein the locking mechanism comprises
a notched region on each flap and a pair of diametrically opposed
ramps on each screw head, each ramp further including a groove for
engagement with the notched region of the flaps when the screw head
is rotated 90 degrees.
11. A bone plate for stabilizing and rigidly fixing bone segments,
comprising: a first surface; a second bone-contacting surface
opposed to the first surface; a channel formed on the first surface
extending lengthwise from one end of the plate to an opposite end;
a plurality of apertures extending through the channel, each
aperture having a predefined shape and size for insertion of a bone
screw; and a flap on each side of the plate extending lengthwise
from one end of the plate to the opposite end, each flap further
extending over at least a portion of the channel.
12. A method for stabilizing and rigidly fixing vertebral bodies in
a patient, comprising the steps of: providing an anterior bone
plate system comprising: a bone plate having a first surface, a
second bone-contacting surface opposed to the first surface, and a
channel formed on the first surface extending lengthwise from one
end of the plate to an opposite end, the bone plate further
including a plurality of apertures extending through the channel,
each aperture having a predefined shape and size; a plurality of
screws capable of insertion into bone, each screw having a lower
threaded portion at one end and an open screw head at an opposite
end, the screw head having a complementary shape and size
sufficient to pass through one of the apertures; and a locking
mechanism for securing the bone plate onto the plurality of screws;
inserting each of the screws into a different vertebral body;
placing the bone plate over the screws; and locking the bone plate
to the screws.
13. The method of claim 12, wherein the step of locking the bone
plate comprises inserting a locking device over each of the
screws.
14. The method of claim 12, wherein the step of locking the bone
plate comprises rotating the screws 90 degrees.
15. The method of claim 12, further comprising the step of
preparing a pilot hole in each of the vertebral bodies prior to
inserting the screws.
16. The method of claim 15, wherein the step of preparing a pilot
hole comprises inserting a distraction pin into the selected
vertebral body.
17. The method of claim 16, wherein the distraction pin is inserted
in the midline of the vertebral body.
18. The method of claim 12, further comprising the step of removing
osteophytes and creating a smooth flat surface on the vertebral
bodies prior to inserting the screws.
19. The method of claim 18, wherein the step of creating a smooth
flat surface on the vertebral bodies further comprises shaving the
vertebral bodies to precisely match the width of the bone
plate.
20. The method of claim 12, further including the steps of
distracting the vertebral bodies and removing a diseased disc
therebetween.
21. The method of claim 20, further including the step of placing a
graft into an evacuated disc space.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
[0002] Not Applicable.
FIELD OF THE INVENTION
[0003] The present invention relates to fixation devices used in
orthopedic and spinal surgery and particularly to bone fixation
plates useful for positioning and immobilizing bone segments.
BACKGROUND OF THE INVENTION
[0004] For a number of known reasons, bone fixation devices are
useful for promoting proper healing of injured or damaged vertebral
bone segments caused by trauma, tumor growth, or degenerative disc
disease. The external fixation devices immobilize the injured bone
segments to ensure the proper growth of new osseous tissue between
the damaged segments. These types of external bone fixation devices
often include internal bracing and instrumentation to stabilize the
spinal column to facilitate the efficient healing of the damaged
area without deformity or instability, while minimizing any
immobilization and post-operative care of the patient.
[0005] One such device is an osteosynthesis plate, more commonly
referred to as a bone fixation plate, that can be used to
immobilize adjacent skeletal parts such as bones. Typically, the
fixation plate is a rigid metal or polymeric plate positioned to
span bones or bone segments that require immobilization with
respect to one another. The plate is fastened to the respective
bones, usually with bone screws, so that the plate remains in
contact with the bones and fixes them in a desired position. Bone
plates can be useful in providing the mechanical support necessary
to keep vertebral bodies in proper position and bridge a weakened
or diseased area such as when a disc, vertebral body or fragment
has been removed.
[0006] Such plates have been used to immobilize a variety of bones,
including vertebral bodies of the spine. These bone plate systems
usually include a rigid bone plate having a plurality of screw
openings. The openings are either holes or slots to allow for
freedom of screw movement. The bone plate is placed against the
damaged vertebral bodies and bone screws are used to secure the
bone plate to the spine, usually with the bone screws being driven
into the vertebral bodies. Exemplary systems like the one just
described can be found in U.S. Pat. No. 6,159,213 to Rogozinski,
U.S. Pat. No. 6,017,345 to Richelsoph, U.S. Pat. No. 5,676,666 to
Oxland et al., U.S. Pat. No. 5,616,144 to Yapp et al., U.S. Pat.
No. 5,549,612 to Yapp et al., U.S. Pat. No. 5,261,910 to Warden et
al., and U.S. Pat. No. 4,696,290 to Steffee.
[0007] Despite the existence of these bone plate systems, there
remains a need for an anterior bone plate system that minimizes any
soft tissue and osseous tissue damage that would occur with its
implementation and still be easy to use. The system must be able to
provide effective fixation and immobilization of vertebral bodies,
while also providing for the subsidence necessary for proper fusion
and prevent axial extension of the plate.
SUMMARY OF THE INVENTION
[0008] The present invention achieves the aforementioned goals by
providing an anterior bone plate system that promotes osseous
fusion and allows subsidence while restricting extension. The bone
plate system further requires a minimum number of screws for
securing the plate onto bone, thus reducing the amount of osseous
tissue damage incurred by the bone structures to which they are
attached. The system is also simple to use and provides for
independent screw placement while incurring minimal soft tissue
damage from lateral retraction.
[0009] These desired features are accomplished by providing a
system comprising a bone plate having a first surface, a second
bone-contacting surface opposed to the first surface, and a channel
formed on the first surface extending lengthwise from one end of
the plate to an opposite end. A plurality of apertures extend
through the channel. Each aperture has a predefined shape and size.
A plurality of screws capable of insertion into bone are also
provided. Each screw has a lower threaded portion at one end and an
open screw head at an opposite end. The screw head has a
complementary shape and size sufficient to pass through the
apertures of the bone plate. Also included is a locking mechanism
for securing the bone plate onto the screws.
[0010] According to one aspect of the invention, the aperture and
the screw head is oblong in shape. The bone plate can also include
surface features such as cleats on the bone-contacting surface. The
bone plate can further include a rigid flap or lip on each side of
the plate extending lengthwise from one end of the plate to the
opposite end. The flaps can extend over the channel.
[0011] In one exemplary embodiment of the present invention, each
screw has a self-tapping end extending from the lower threaded
portion. Further, each screw head can extend into an upper threaded
portion configured to sit proud, i.e., not engaged in bone. A
locking device can be provided to secure the bone plate onto the
screws. The locking device can be a nut, cam, wedge, or a retaining
ring.
[0012] In another exemplary embodiment of the present invention,
each flap includes a notched region, and each screw head includes a
pair of diametrically opposed ramps. Each of the ramps further
includes a groove for engagement with the notched region of the
flaps. In this system, the bone plate can be effectively locked
onto the screws by placing the plate over the screws and rotating
the screw heads 90 degrees so that the grooves of the ramps and the
notched regions of the flaps form an interference fit.
[0013] Also provided is a method for stabilizing and rigidly fixing
vertebral bodies in a patient, involving the steps of identifying a
damaged region of the patient's spine, preparing a pilot hole in
each of the vertebral bodies in the damaged region, removing
osteophytes from the selected vertebral bodies, creating a smooth
flat surface on the selected vertebral bodies, providing an
anterior bone plate system as described above, inserting a screw in
each of the pilot holes, placing the bone plate over the screws,
and locking the bone plate to the screws.
[0014] The pilot holes can be prepared by inserting a distraction
pin into each of the selected vertebral bodies. Each of the
distraction pins should be inserted in the midline of the vertebral
bodies, with only one pilot hole being made in each vertebral body.
Hence, only one screw is inserted into any single vertebral body,
reducing the osseous damage to the spine.
[0015] If necessary, the selected vertebral bodies can be
distracted and a diseased disc removed from the damaged region. A
graft can then be placed into the evacuated disc space. Prior to
inserting the screws and plate, the vertebral bodies must be shaved
to create a smooth flat surface that precisely matches the width of
the bone plate. This ensures proper adhesion of the plate to the
bony surface and also produces a low profile so that damage to
surrounding soft tissue can be minimized.
[0016] Further features of the invention, its nature and various
advantages, will be more apparent from the accompanying drawings
and the following detailed description of the drawings and the
preferred embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The invention can be more fully understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0018] FIG. 1 is a perspective view of an anterior bone plate
system of the present invention, wherein the screws are extending
through the bone plate;
[0019] FIG. 2 is a side view of the system of FIG. 1;
[0020] FIG. 3 is a perspective view showing the bottom of the
system of FIG. 1;
[0021] FIG. 4 is a perspective view of another embodiment of the
anterior bone plate system of the present invention, wherein the
screws are extending through the bone plate;
[0022] FIG. 5 is a side view of the system of FIG. 4;
[0023] FIG. 6 is a detailed view of a portion of the screw of FIGS.
4 and 5;
[0024] FIG. 7 is a perspective view of yet another embodiment of
the anterior bone plate system of the present invention, wherein
the screws are extending through the bone plate;
[0025] FIG. 8 is a perspective view showing the bottom of the
system of FIG. 7;
[0026] FIG. 9 is a cross-sectional view of the anterior bone plate
system of FIG. 7; and
[0027] FIG. 10 is a detailed view of the retaining ring present in
the system of FIGS. 7 and 9.
DETAILED DESCRIPTION OF THE INVENTION
[0028] The present invention provides an anterior bone plate system
which is easy to use and allows independent screw placement. The
system requires only one bone screw to be used per vertebral body
level, thus reducing the amount of osseous tissue damage to the
vertebral bodies. The bone plate system of the present invention
also promotes good bone fusion by providing enough subsidence to
facilitate proper bone growth, while at the same time preventing
extension. Furthermore, the bone plate system of the present
invention provides a good bone screw to plate interface locking
mechanism.
[0029] Referring to FIG. 1, in one exemplary embodiment of the
anterior bone plate system 100 of the present invention, a bone
plate 110 with a plurality of screws 130 extending through
apertures or slots 112 thereon are shown. The apertures 112 allow
the plate 110 to be placed from above onto previously placed screws
130, thereby enabling independent screw placement. Each screw 130
has a self-tapping distal end 132 extending into a lower threaded
portion 134 with an aggressive thread pitch to facilitate its
purchase into bone. As shown in FIG. 2, each screw 130 includes a
screw head 136 at an opposite (proximal) end that is adapted to
seat within a channel 118 extending lengthwise on a first side 114
of the plate 110 that is configured to face away from a bony
surface. Channel 118 is machined parallel to the longitudinal axis
of the plate 110 such that a rigid lip or flap 120 is formed
lengthwise on both sides of the bone plate 110. Each lip or flap
120 extends over a portion of the channel 118 as illustrated in
FIGS. 1 and 2. Since the system 100 is a top loading plate system,
this lip 120 ensures the proper placement of the bone plate 110
with respect to the screws 130 when the plate 110 is dropped down
onto the screws 130.
[0030] In the present invention, screws 130 can have open screw
heads 136. Each screw 130 can also include an upper threaded
portion with threads set proud, i.e., not engaged in bone, for
engaging a locking device such as a nut 150 as shown in FIG. 2.
While a nut 150 has been illustrated, it is contemplated that other
suitable locking devices such as a wedge, cam, or retaining ring
can also be used. The major thread diameter of the lower threaded
portion 134 of the screws 130 can be in the range of about 3.5 to
5.5 mm, while the cancellous thread pitch of the lower threaded
region 134 can be approximately 1.5 or more to provide unicortical
purchase into bone. The bone screws 130 are placed in the midline
of the vertebral body, with only one bone screw 130 per vertebral
body or level required to adequately stabilize the bone segments to
the plate 110. This advantageous feature of the present invention
reduces the amount of bone damage that would occur to the spine
when more than one screw is inserted within the same vertebral
body.
[0031] Bone plate 110 can also include surface features 122 such as
cleats or ridges on the second side 116 that is configured to
contact bony surface as illustrated in FIG. 3. The surface features
122 help anchor the bone plate 110 onto the bony surface of the
vertebral bodies yet still allow flexion or subsidence while
preventing extension, which is undesirable for proper fusion and
healing. As can be seen in FIG. 3, the apertures 112 of the bone
plate 110 can be oblong in shape and extend in a lengthwise
direction. Further, the screw heads 136 of each of the screws 130
can be oblong in shape, enabling them to pass through the apertures
112. Thus, it may be necessary to align the screws 130
unidirectionally, i.e., the oblong-shaped screw heads 136 are
aligned lengthwise, so that the plate 110 can be placed on top of
the screws 130. The anterior bone plate system 100 can be
configured such that the bone plate 110 is able to slide with
respect to the screw heads 136 to allow for dynamic interaction
with the bone segments. As is well understood and established by
Wolffs Law, the ability of the plate 110 to distribute physiologic
loads to the bone is important for the fusion process. Since
osseous tissue grows along lines of stress, this translational
characteristic acts to maintain compressive loads across the
bone/graft interface to promote bony fusion. The ability of the
bone plate 110 of the present invention to effect subsidence,
particularly as a result of its oblong shaped apertures 212 that
allow the plate 110 some micromotion relative to the screw heads
236, provides for effective fusion of bony segments.
[0032] While the plate 110 has been illustrated as having three
apertures 112, it is contemplated that the bone plate 110 of the
present invention should have at least two apertures 112 for
immobilizing at least two bone segments. The plate 110 may also
contain more than two or three apertures 112. Further, while the
apertures 112 and screw heads 136 have been described as having an
oblong shape, it is understood that the apertures 112 and screw
heads 136 can have any complementary size, shape or geometry.
[0033] In another exemplary embodiment of the present invention,
FIG. 4 illustrates an anterior bone plate system 200 which provides
an additional benefit in that it does not require additional
external components to secure the bone plate 210 to screws 230. As
shown in FIG. 4, bone plate 210 includes at least two apertures 212
extending from a first side 214 of the plate 210 that is configured
to face away from bony structure to a second side 216 that is
configured to contact bony surface. A channel 218 extends
lengthwise down the first side 214 of the bone plate 210 and is
machined parallel to the longitudinal axis of the plate 110 such
that a rigid lip or flap 220 is created on both sides of the bone
plate 210. Each lip or flap 220 runs lengthwise and extends over at
least a portion of channel 218 as illustrated in FIGS. 4 and 5.
[0034] Consistent with anterior bone plate system 100, the
apertures 212 of bone plate 210 allow the plate 210 to be placed on
top of previously placed bone screws 230. Each bone screw 230 can
have a self-tapping distal end 232 extending into a lower threaded
portion 234 with an aggressive thread pitch to facilitate its
purchase into bone. As shown in FIG. 6, each screw 230 includes a
screw head 236 at an opposite (proximal) end that is adapted to
seat within the channel 218. The major thread diameter of the lower
threaded portion 234 of screw 230 can be in the range of about 3.5
to 5.5 mm, while the cancellous thread pitch of the lower threaded
region 234 can be approximately 1.5 or more to provide unicortical
purchase into bone. The bone screws 230 are placed in the midline
of the vertebral body, with only one bone screw 230 per vertebral
body or level required to adequately stabilize the bony segments to
the plate 210. This advantageous feature of the invention reduces
the amount of bone damage that would occur to the spine when more
than one screw is inserted within the same vertebral body.
[0035] Bone plate 210 can also include surface features 222 such as
cleats or ridges on the second side 216 that is adapted to contact
bony surface as illustrated in FIG. 4. The surface features 222
help anchor the bone plate 210 onto the bony surface of the
vertebral bodies yet still allow flexion or subsidence while
preventing extension, which is undesirable for proper fusion and
healing.
[0036] As shown in FIG. 6, the screw heads 236 of each of the
screws 230 can be oblong in shape, while the apertures 212 of bone
plate 210 are also oblong in shape in a lengthwise direction so
that the bone plate 210 can be placed on top of and pass through
the screw heads 236 when the screws 230 are unidirectional, i.e.,
the oblong-shaped screw heads 236 are aligned lengthwise. Each
screw 230 can also have an open head 236, which can include a
shaped bore 238 for attachment to an inserter tool or screwdriver
(not shown).
[0037] Extending proximally from the screw head 236, away from the
self-tapping distal end 232, are a pair of diametrically opposed
ramps 240. The ramps 240 are bi-level and include a cutaway
portion, or groove 242 that is configured to frictionally engage
with a notched region 222 on flaps 220 when the screws 230 are
rotated 90.degree., i.e., rotated such that the major diameter MD
of the screw head 236 is transversely oriented with respect to the
long axis of plate 210. The complementary surface features on the
screw heads 236 and flaps 220 provide a simple and effective
locking mechanism for securing the plate 210 to the bony surface,
without the need for any additional locking devices. By simply
rotating the screws 230 90.degree. after mounting the plate 210
upon the screws 230, the plate 210 is able to be locked onto the
screw heads 236, with the grooves 242 achieving an interference fit
with the notched region 222 of the flaps 220.
[0038] Anterior bone plate system 200 can be configured such that
the bone screws 230 are capable of sliding with respect to the
apertures 212 of the plate 210, until the screws 230 are properly
seated and locked. Once locked, the anterior bone plate system
allows for subsidence and micromotion to promote healing and
fusion, while preventing extension. In order for the locking system
to be implemented, bone plate 210 and channel 218 should be sized
and configured to allow the oblong screw heads 236 sufficient room
to rotate within the channel 218.
[0039] Bone plate 210 can contain at least two apertures 212 for
allowing the screw heads 236 to pass through the plate 210. The
apertures 212 should be positioned on the bone plate 210 such that
the plate can attach to an upper and lower vertebral body.
According to one aspect of the invention, the bone plate 210 can
include modified T-slots fabricated thereon extending from one end
of the plate 210 and directed longitudinally to the opposite end.
The T-slots can include one elliptical slot extending vertically,
and another slot extending horizontally. Lobes can be featured on
the T-slots to provide interference with the ramps 240. By rotating
the bone screw 230 90.degree., the screw head ramp interferes with
the T-slots of the plate 210. Continued rotation allows the screws
230 to cam until the interference is cleared on the other side and
the bone plate 210 is locked onto the screws 230.
[0040] In yet another exemplary embodiment of the present
invention, anterior bone plate system 300 is shown in FIGS. 7 and
8. Bone plate system 300 includes bone plate 310 which has at least
two apertures 312 extending from a first side 314 of the plate 310
that is configured to face away from bony structure to a second
side 316 that is configured to contact bony surface. A channel 318
extends lengthwise down the first side 314 of the bone plate
310.
[0041] Consistent with anterior bone plate systems 100 and 200, the
apertures 312 of bone plate 310 allow the plate 310 to be placed on
top of previously positioned bone screws 330. Each bone screw 330
can have a self-tapping distal end 332 and a lower threaded portion
334 with an aggressive thread pitch to facilitate its purchase into
bone. As shown in FIG. 8, each screw 330 includes a screw head 336
at an opposite (proximal) end that is adapted to seat within the
channel 218. The major thread diameter of the lower threaded
portion of the screws 330 can be in the range of about 3.5 to 5.5
mm, while the cancellous thread pitch of the lower threaded region
334 can be approximately 1.5 or more to provide unicortical
purchase into bone. The bone screws 330 are placed in the midline
of the vertebral body, with only one bone screw 330 per vertebral
body or level required to adequately stabilize the bony segments to
the plate 310 to reduce the amount of bone damage that would occur
to the spine when more than one screw is inserted within the same
vertebral body.
[0042] Bone plate 310 can also include surface features 322 such as
cleats or ridges on the second side 316 that is adapted to contact
bony surface as illustrated in FIG. 7. The surface features 322
help anchor the bone plate 310 onto the bony surface of the
vertebral bodies yet still allow flexion or subsidence while
preventing extension, which is undesirable for proper fusion and
healing.
[0043] As shown in FIG. 9, each of the screws 330 can have an open
head 336, which can include a shaped bore 338 for attachment to an
inserter tool or screwdriver (not shown). Each screw head 336 can
also include circumferential grooves 344 machined on the outside
diameter of the screw head 336. The grooves 344 are set proud,
i.e., not engaged in bone, for engaging a locking device such as
retaining ring 346 as shown in FIG. 10. The channel 318 of the bone
plate 310 is machined to provide a low profile that can accommodate
the screw heads 336 and provide an overall consistently low
profile, as illustrated in FIG. 9. Further, retaining rings 346
provide easy fastening between the bone screws 330 and the bone
plate 310 without increasing the profile of the anterior bone plate
system 300. While a retaining ring 346 of the shape shown in FIG.
10 is suitable, it is contemplated that the retaining ring can be
configured in any number of geometries which would allow the
retaining ring to be placed over the screw head 336 and against the
bone plate 310.
[0044] Bone plate 310 can have at least two apertures 312. The
apertures 312 can comprise two slots to enable the plate 310 to
glide with respect to the screws 330. Alternatively, the apertures
312 can be a slot and a hole, or any configuration of a slot and
hole that enables the screw head 336 to be passed through the plate
310, and which is configured to fix at least an upper and lower
vertebral body.
[0045] In each of the anterior bone plate systems 100, 200, 300
described above, the bone plate 110, 210, 310 can be constructed so
as to conform to the shape of the anterior surfaces of the
vertebrae that it will be mounted upon. The plate can be curved
along both its longitudinal and transverse axes such that the
second side 116, 216, 316 is substantially concave to improve its
conformity to the shape of the vertebral bodies. Further, one of
ordinary skill in the art will appreciate that the bone plates 110,
210, 310 of the invention can be made of a variety of high
strength, biologically compatible materials that are preferably
compatible with MRI techniques. Useful materials include polymers,
composite reinforced polymers, and metals such as stainless steel,
titanium and titanium alloys.
[0046] In an exemplary method for implementing the anterior bone
plate systems 100, 200, 300 described above, several steps are
necessary to prepare the patient for surgery and before the plate
system 100, 200, 300 can be installed. As an initial matter, the
patient should be placed in a supine position, with the spine
stabilized appropriately. Next, the patient is prepped and draped
in the usual manner. Using radiographic imaging, the affected
spinal level(s) or area(s) are identified. An incision is then made
to optimize the exposure appropriate for the procedure.
[0047] Where necessary, decompression and grafting procedures are
performed. To effect the decompression and grafting procedure, a
distraction pin insertion instrument is used. The distraction pin
insertion instrument allows distraction pins (also called Caspar
pins) to be inserted perpendicular to the bone's anterior cortical
surface or vertebral body, and perpendicular to the
superior/inferior midline of the vertebral bodies. In the present
invention, each vertebral body has only a single pin inserted. It
is important to note that the pilot holes must be perfectly
aligned, i.e., distraction pins must be inserted perfectly
parallel. Routine distraction is then performed and a diskectomy,
the surgical removal of a diseased disc, follows. A graft can then
be placed into the evacuated disc space under gentle distraction
and when the surgeon is comfortable with placement, the distraction
instrument and Caspar pins are removed.
[0048] The bone screws 130, 230, 330 of the present invention are
preferably inserted into pilot holes left in the vertebral bodies
or bony segments that will be attached to the bone plate 110, 210,
310 by the Caspar pins. It is also possible to drill using about a
2.0 mm diameter drill bit prior to using the distraction pins. The
distraction procedure provides each vertebral body with a pilot
screw hole for placement of a bone screw 130, 230, 330. It should
be noted that, while the bone screws are preferably used with pilot
holes, it is possible to use the anterior bone plate systems 100,
200, 300 without pilot holes as well, i.e., without first using a
distraction pin instrument.
[0049] After the pilot holes are prepared, all anterior anomalies,
i.e., osteophytes, that can impede bone plate 110, 210, 310
placement are removed. Using an osteophyte remover instrument, the
endplate and anterior column of the vertebral body is prepared to
allow the underside of the plate 110, 210, 310 to be sandwiched
tightly against the vertebral bodies to promote osseous fusion. The
osteophyte remover instrument is used to create a smooth flat
surface to fit the plate 110, 210, 310 precisely and match the
plate's width. By shaving the vertebral bodies in this manner, the
bone plate 110, 210, 310 is able to be inserted flush against the
bony surface and produce a low profile which reduces the amount of
damage to surrounding soft tissue.
[0050] Self-tapping screws 130, 230, 330 of the present invention
are inserted into Caspar pinholes and tightened down to the
anterior cortex, and aligned such that the open screw heads 136,
236, 336 are pointed so the openings are in the sagittal plane. The
appropriate length plate 110, 210, 310 is then chosen by the
surgeon and dropped onto the screw heads 136, 236, 336. The plate
110, 210, 310 is then secured down in the manner described above
for bone plate Systems 110, 210, 310 and finally the patient is
closed in a standard manner.
[0051] It will be understood that the foregoing is only
illustrative of the principles of the invention, and that various
modifications can be made by those skilled in the art without
departing from the scope and spirit of the invention. All
references cited herein are expressly incorporated by reference in
their entirety.
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