U.S. patent application number 12/046425 was filed with the patent office on 2008-09-18 for hinged bone plate and related methods.
This patent application is currently assigned to NuVasive, Inc.. Invention is credited to Bret A. Ferree.
Application Number | 20080228230 12/046425 |
Document ID | / |
Family ID | 23067878 |
Filed Date | 2008-09-18 |
United States Patent
Application |
20080228230 |
Kind Code |
A1 |
Ferree; Bret A. |
September 18, 2008 |
Hinged Bone Plate and Related Methods
Abstract
A bone plate system comprising a thin plate and fasteners for
securing the plate to at least two segments of bone. The plate may
be hinged along the central axis, with a pair of collinear holes on
each portion of the plate. Each of the holes accommodates a bolt
which is screwed into the bone and secured to the plate using a
nut.
Inventors: |
Ferree; Bret A.;
(Cincinnati, OH) |
Correspondence
Address: |
JONATHAN SPANGLER;NU VASIVE, INC.
4545 TOWNE CENTRE COURT
SAN DIEGO
CA
92121
US
|
Assignee: |
NuVasive, Inc.
San Diego
CA
|
Family ID: |
23067878 |
Appl. No.: |
12/046425 |
Filed: |
March 11, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10860850 |
Jun 3, 2004 |
7341590 |
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12046425 |
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10108287 |
Mar 27, 2002 |
6764489 |
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10860850 |
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60279157 |
Mar 27, 2001 |
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Current U.S.
Class: |
606/280 ;
606/290; 606/292; 606/70 |
Current CPC
Class: |
A61B 17/8695 20130101;
A61B 17/7059 20130101; Y10S 606/90 20130101; Y10S 606/901 20130101;
A61B 17/8047 20130101; A61B 17/8665 20130101; Y10S 606/909
20130101; Y10S 606/907 20130101 |
Class at
Publication: |
606/280 ; 606/70;
606/290; 606/292 |
International
Class: |
A61B 17/80 20060101
A61B017/80; A61B 17/56 20060101 A61B017/56 |
Claims
1. A system for rigidly affixing a first bone segment to at least a
second bone segment, comprising: a first plate having a first pair
of openings, said first plate hingedly coupled to a second plate
having a second pair of openings, wherein said first and second
pairs of openings are dimensioned to receive bone anchor elements;
and a plurality of bone anchor elements dimensioned to be inserted
through said first and second pairs of openings to rigidly affix
said first and second plates to said first and second bone
segments.
2. The system of claim 1, wherein said first and second bone
segments comprise first and second vertebral bodies at adjacent
vertebral levels within a spine.
3. The system of claim 1, wherein said first plate includes a first
hinge element, said second plate includes a second hinge element,
and said first and second plates are hingedly coupled together by
engaging said first hinge element with said second hinge
element.
4. The system of claim 1, wherein at least one of said first pair
of openings and said second pair of openings comprise elongated
slots.
5. The system of claim 4, wherein said elongated slots extend along
a longitudinal axis of at least one of said first and second
plates.
6. The system of claim 1, wherein said second pair of openings lie
at a 15.degree. anterior angulation to the upper surface of said
second plate.
7. The system of claim 1, wherein said first pair of openings
extend to an outer edge of said first plate.
8. The system of claim 1, further comprising a plurality of locking
devices which may be fixed in position on said bone anchor
elements.
9. The system of claim 8, wherein said locking devices comprise
snap rings.
10. The system of claim 1, wherein said bone anchor elements
comprise a plurality of bone engaging screws, each of said screws
including a lower threaded section for affixing said screw within
said bone.
11. The system of claim 1, wherein at least one of the first and
second plates can be hingedly rotated away from at least one of
said first and second bone segments during the plate affixation
process.
12. A method of affixing a first bone segment to a second bone
segment, comprising: providing a first plate having a first pair of
openings hingedly coupled to a second plate having a second pair of
openings; and positioning said first and second plates against said
first and second bone segments such at least one of said first pair
of openings is aligned with said first bone segment and at least
one of said second pair of openings is aligned with said second
bone segment; and introducing a plurality of bone anchor elements,
one through each of said first and second pairs of openings to
affix said first and second plates to said first and second bone
segments.
13. The method of claim 12, wherein said first and second bone
segments comprise first and second vertebrae at adjacent vertebral
levels within the spine.
14. The method of claim 12, wherein said first plate includes a
first hinge element, said second plate includes a second hinge
element, and said first and second plates are hingedly coupled
together by engaging said first hinge element with said second
hinge element.
15. The method of claim 12, wherein said bone anchor elements
comprise a plurality of bone engaging screws, each of said screws
including a lower threaded section for affixing said screw within
said bone.
16. The method of claim 12, wherein at least one of the first and
second plates can be hingedly rotated away from at least one of
said first and second bone segments during the plate affixation
process.
17. A system for performing orthopedic surgery, comprising: a first
plate having a first pair of openings and a first elongated hinge
element, said first plate hingedly coupled to a second plate having
a second pair of openings and a second elongated hinge element,
wherein said first and second pairs of openings are dimensioned to
receive bone anchor elements; and a plurality of bone anchor
elements dimensioned to be inserted through said first and second
pairs of openings to rigidly affix said first and second plates to
said first and second bone segments.
18. The system of claim 17, wherein said first and second plates
are hingedly coupled together by engaging said first elongated
hinge element with said second elongated hinge element.
19. The system of claim 17, wherein said bone anchor elements
comprise a plurality of bone engaging screws, each of said screws
including a lower threaded section for affixing said screws within
bone.
20. The system of claim 17, wherein at least one of the first and
second plates can be hingedly rotated away from at least one of
said first and second bone segments during the plate affixation
process.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] The present application is a division of commonly owned and
co-pending U.S. patent application Ser. No. 10/860,850, filed on
Jun. 3, 2004, now issued as U.S. Pat. No. 7,341,590, which is
division of commonly owned and co-pending U.S. patent application
Ser. No. 10/108,287 filed Mar. 27, 2002, now issued as U.S. Pat.
No. 6,764,489, the complete disclosures of which are hereby
incorporated herein by reference in their entireties for all
purposes. Additionally, the present application claims benefit
under 35 U.S.C. .sctn. 119(e) from U.S. Provisional Application
Ser. No. 60/279,157, filed on Mar. 27, 2001, the entire contents of
which are hereby expressly incorporated by reference into this
disclosure as if set forth fully herein.
BACKGROUND OF THE INVENTION
[0002] I. Field of the Invention
[0003] This invention relates generally to devices for use in
spinal surgery, and, in particular, to a hinged anterior
thoracic/lumbar plate which is implantable within a patient for
stabilization of the spine.
[0004] II. Description of the Related Art
[0005] Eighty-five percent of the population will experience low
back pain at some point. Fortunately, the majority of people
recover from their back pain with a combination of benign neglect,
rest, exercise, medication, physical therapy, or chiropractic care.
A small percent of the population will suffer chronic low back
pain. The cost of treatment of patients with spinal disorders plus
the patient's lost productivity is estimated at 25 to 100 billion
dollars annually.
[0006] Seven cervical (neck), 12 thoracic, and 5 lumbar (low back)
vertebrae form the normal human spine. Intervertebral discs reside
between adjacent vertebra with two exceptions. First, the
articulation between the first two cervical vertebrae does not
contain a disc. Second, a disc lies between the last lumbar
vertebra and the sacrum (a portion of the pelvis).
[0007] Motion between vertebrae occurs through the disc and two
facet joints. The disc lies in the front or anterior portion of the
spine. The facet joints lie laterally on either side of the
posterior portion of the spine. The osseous-disc combination of the
spine coupled with ligaments, tendons, and muscles are essential
for spine function. The spine allows movement (flexation, lateral
bending, and rotation), supports the body, and protects the spinal
cord and nerves.
[0008] The disc changes with aging. As a person ages the water
content of the disc falls from approximately 85 percent at birth to
70 percent in the elderly. The ratio of chondroitin sulfate to
keratin sulfate decreases with age. The ratio of chondroitin 6
sulfate to chondroitin 4 sulfate increases with age. The
distinction between the annulus and the nucleus decreases with age.
These changes are known as disc degeneration. Generally disc
degeneration is painless.
[0009] Premature or accelerated disc degeneration is known as
degenerative disc disease. A large portion of patients suffering
from chronic low back pain is thought to have this condition. As
the disc degenerates, the nucleus and annulus functions are
compromised. The nucleus becomes thinner and less able to handle
compression loads. The annulus fibers become redundant as the
nucleus shrinks. The redundant annular fibers are less effective in
controlling vertebral motion. The disc pathology can result in: 1)
bulging of the annulus into the spinal cord or nerves; 2) narrowing
of the space between the vertebrae where the nerves exit; 3) tears
of the annulus as abnormal loads are transmitted to the annulus and
the annulus is subjected to excessive motion between vertebrae; and
4) disc herniation or extrusion of the nucleus through complete
annular tears. Disc herniation can also cause arthritis of the
facet joints, which, in turn, may cause back pain.
[0010] The problems created by disc degeneration, facet arthritis,
and other conditions such as spondylolysis, spondylolisthesis,
scoliosis, fracture, tumor, or infection are frequently treated by
spinal fusion. Such problems may include pain in the back or legs,
nerve injury, risk of future nerve injury, or spinal deformity. The
goal of spinal fusion is to successfully "grow" two or more
vertebrae together. To achieve this, bone from the patient's body
(spine or iliac crest) or from cadavers is grafted between
vertebrae. Alternatively, bone graft substitutes, such as
hydroxyapatite and bone morphogenetic protein, may be used. The
bone graft is placed between the vertebrae in the disc space and/or
over the posterior elements of the vertebrae (lamina and transverse
processes). The surgeon scrapes the vertebrae to create bleeding.
Blood flows into the bone graft. The scraped bone, blood clot
(hematoma), and the bone graft simulates a fracture. As the patient
heals, the "fracture" causes the vertebrae to be fused and heal
together.
[0011] Spinal instrumentation may be placed onto or into the spine
to immobilize the vertebrae that are going to be fused.
Immobilization leads to a higher fusion rate and speeds a patient's
recovery by eliminating movement. The use of spinal fixation plates
or rods for correction of spinal deformities and for fusion of
vertebrae is well known. Typically, a rigid plate is positioned to
span bones or bone segments that need to be immobilized with
respect to one another. Bone screws may be used to fasten the plate
to the bones. Spinal plating systems are commonly used to correct
problems in the lumbar and cervical portions of the spine, and are
often installed posterior or anterior to the spine.
[0012] One technique of treating these disorders is known as
surgical arthrodesis of the spine. This can be accomplished by
removing the intervertebral disk and replacing it with bone and
immobilizing the spine to allow space to connect the adjoining
vertebral bodies together. The stabilization of the vertebrae to
allow fusion is often assisted by a surgically implanted device to
hold the vertebral bodies in proper alignment and allow the bone to
heal, much like placing a cast on a fractured bone. Such techniques
have been effectively used to treat the above described conditions
and in most cases are effective at reducing the patient's pain and
preventing neurologic loss of function.
[0013] Several types of anterior spinal fixation devices are
currently in use. One technique involves placement of screws
completely through the vertebral body, called bicortical purchase.
The screws are placed through a titanium plate but are not attached
to the plate. This device is difficult to place, and
over-penetration of the screws can result in damage to the spinal
cord. The screws can back out of the plate into the surrounding
tissues as they do not fix to the plate. Several newer generation
devices have used a unicortical purchase of the bone, and in some
fashion locking the screw to the plate to provide stability and
secure the screw from backout. Problems have resulted from over
rigid fixation and stress shielding, resulting in nonunion of the
bony fusion, chronic micromotion during healing, resulting in
stress fracture of the fixation device at either the screw to the
plate resulting in screw backout, or inadequate fixation strength
and resultant collapse of the graft and angulation of the
spine.
[0014] Another technique involves formation of a medical construct
using surgical rods and connectors. Such systems include a pair of
rods which are placed on opposite sides of the portion of the spine
which is intended to be fused. Pedicle, lateral, and oblique
mounting means are used to secure the rods relative to the desired
portion of the spine which will be fused by the fixation system.
However, this construct extends outwardly further than a
plate/screw system, potentially affecting the surrounding muscle,
and causing pain to the patient.
[0015] Plates and screws are often placed onto the anteriolateral
portion of the spine to facilitate spinal fusion. Generally, they
are placed across one or two disc spaces in the treatment of
fractures and tumors. Most of the present systems use screws with
nuts for the posterior portion of the vertebrae. The screws with
nuts are commonly called bolts by those skilled in this art.
Screws, without nuts, are placed through the anterior portion of
the plate. The posterior bolts are generally thought to rigidly fix
the plate to the screws. Some surgeons believe that the rigid
bolt/plate construct provides more spinal stability. However, while
screws without nuts are easier to insert, they also are known to
back out, causing potential failure of the fusion. Devices have
been devised to hold the screws within the plate. It is believed
that there are no systems in the marketplace which uses an all bolt
construct.
[0016] A typical device which is used for spinal fixation is taught
in U.S. Pat. No. 4,611,581. This device consists of a simple plate
having a series of openings for receiving threaded portions of
force transmitting members which securely lock in a part of the
bone of the vertebra in which they are mounted and a threaded
portion which projects outwardly from the vertebrae. The vertebra
is pulled into the desired relationship with adjacent vertebrae by
tightening a nut on the outwardly projecting end portion of the
force transmitting member.
[0017] Another typical device used is shown in U.S. Pat. No.
6,306,136. This patent discloses an implant which is used
particularly as an anterior cervical plate, having a solid plate
consisting of two sliding parts, each of which has holes for
anchoring screws in two adjacent vertebrae. The sliding parts are
provided with a screw and slot for limiting the sliding travel
between the parts.
[0018] Another vertebrae connecting plate is taught in U.S. Pat.
No. 5,147,361. This plate has a small thickness, and uses set
screws which are screw engaged in threaded holes within the
connecting plate to prevent any loosening of the screws within the
plate.
SUMMARY OF THE INVENTION
[0019] It is therefore an object of the present invention to
provide a plate system for spinal surgery, which has a low profile
and comfortably fits a patient's anatomy.
[0020] It is a further object of the present invention to provide a
plate system which is easily implanted within a patient.
[0021] It is a further object of the present invention to provide a
plate system which is easily positioned and establishes a secure
connection between vertebrae.
[0022] It is a still further object of the present invention to
provide a plate system which is easily adaptable to the
lumbar/thoracic region of the spine.
[0023] These and other objects and advantages of the present
invention will be readily apparent in the description that
follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a lateral view of a prior art spinal plate
installed in vertebrae of a spine;
[0025] FIG. 2 is an anterior to posterior view of the plate shown
in FIG. 1;
[0026] FIG. 3 is an exploded lateral view of the plate and
associated devices shown in FIG. 1;
[0027] FIG. 4 is an end view of the plate and devices of FIG. 3 in
the assembled position;
[0028] FIG. 5 is a perspective partially assembled view of the
spinal plate of the present invention along with C-rings;
[0029] FIG. 6 is another perspective partially assembled view of
the system of FIG. 5 along with locking nuts;
[0030] FIG. 7 is a perspective view of the spinal plate system of
FIG. 5 in its assembled position;
[0031] FIG. 8 is a lateral view of the plate system of the present
invention with two bolts installed;
[0032] FIG. 9 is a lateral view of the plate system of the present
invention during the installation of two C-rings;
[0033] FIG. 10 is a lateral view of the plate system of the present
invention with the nut installed on the lower posterior bolt;
[0034] FIG. 11 is a lateral view of the plate system with the two
posterior bolts installed;
[0035] FIG. 12 is a lateral view of the plate system with C-rings
for the anterior bolts;
[0036] FIG. 13 is a lateral view of the plate system of the present
invention completely installed;
[0037] FIG. 14 is a sectional view of the system shown in FIG.
13;
[0038] FIG. 15 is a fragmentary view of an anterior hole of plate
of the present invention showing the beveled orientation through
the plate;
[0039] FIG. 16 is a lateral view of the plate system having slotted
holes on the anterior section of the plate;
[0040] FIG. 17 is a lateral view of an alternative embodiment of
the plate system of the present invention;
[0041] FIG. 18 is a side view of the plate shown in FIG. 17 partly
in phantom;
[0042] FIG. 19 is a cross-sectional view of the plate shown in FIG.
17;
[0043] FIG. 20 is a plan view of a plate of the present invention
which is angled for use on a kyphotic spine;
[0044] FIG. 21 is a plan view of a plate of the present invention
which is angled for use on a lordotic spine; and
[0045] FIG. 22 is a plan view of another embodiment of a spine
plate according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0046] Illustrative embodiments of the invention are described
below. In the interest of clarity, not all features of an actual
implementation are described in this specification. It will of
course be appreciated that in the development of any such actual
embodiment, numerous implementation-specific decisions must be made
to achieve the developers' specific goals, such as compliance with
system-related and business-related constraints, which will vary
from one implementation to another. Moreover, it will be
appreciated that such a development effort might be complex and
time-consuming, but would nevertheless be a routine undertaking for
those of ordinary skill in the art having the benefit of this
disclosure. The hinged anterior thoracic/lumbar plate disclosed
herein boasts a variety of inventive features and components that
warrant patent protection, both individually and in
combination.
[0047] Spinal plate systems using a combination of screws and bolts
to attach plates to the posterior portion of vertebrae are well
known and commonly used in the prior art. FIGS. 1-4 depict one such
common prior art method of spinal stabilization system, comprising
a spinal plate 10 placed across several vertebrae 12, 14. Plate 10
contains a series of openings 16 which are intended to receive bone
anchoring hardware. Two openings 16 are positioned against vertebra
12, and two openings 16 are positioned against vertebra 14. A bone
graft 18 positioned between vertebrae 12, 14 acts as a replacement
for a damaged or otherwise removed vertebra. A pair of screws 20,
each having a threaded section 21, are installed through openings
16 on the anterior portion of plate 10, while a pair of bolts 22
are installed through openings 16 on the posterior portion of plate
10. Each bolt 22 consists of a lower threaded section 23 and an
upper threaded post 24 to which a nut 26 is affixed to secure bolt
22 in position. The threaded sections 21, 23 of screws 20 and bolts
22 are anchored in vertebrae 12, 14. When installed in the spine,
bolts 22 and screws 20 converge to resist pull-out, as shown in
FIG. 4. This screw and bolt combination provides increased spinal
stability, as the bolts 22 rigidly affix the spinal plate 10 to the
screws 20, which are much easier to insert in the procedure.
[0048] FIGS. 5-7 show a preferred embodiment of a hinged spinal
plate system 30 of the present invention, ideally suited for use in
the lumbar/thoracic portion of the spine. Plate system 30 includes
a thin plate 32 having two plate elements 32a, 32b which are
removably coupled together along a hinged section 34. Element 32a
contains generally rounded edges 35a, 35b, a cutaway section 35c,
and two generally circular through openings 36 positioned
collinearly along element 32a. Element 32b contains generally
rounded edges 38a, 38b, a cutaway section 38c, and two generally
circular through openings 40 positioned collinearly along element
32b. Although openings 36 on plate element 32a are shown as
circular in this embodiment, and openings 40 on plate element 32b
are shown as elongated slots, openings 36, 40 may be configured in
any suitable combination of circular openings and elongated slots.
Cutaway sections 35c, 38c afford the surgeon a better view of the
bone graft inserted between vertebrae, in part to insure that the
bone graft is not projecting into the spinal cord or nerves. Plate
32 is preferably constructed from an implant grade titanium alloy,
such as Ti-6Al-4V. Alternatively, plate 32 may be constructed from
any number of suitable materials, such as stainless steel ASTM
F138.
[0049] An opening 42 is formed along hinged section 34 of plate
system 30 by a cutout section 42a in element 32a and a cutout
section 42b in element 32b. Opening 42 may be used to accommodate
additional hardware to increase the stability of plate system 30
against the spine. Also, opening 42 may be used if additional
hardware is needed to secure the bone graft in position.
[0050] A series of bolts 50 are inserted through openings 36, 40 to
secure plate 32 to the vertebrae. Bolts 50 contain a lower threaded
portion 52 for threadedly engaging pre-drilled holes in the
appropriate vertebrae of the spine, and an upper threaded portion
54 which extends through plate 32 after it has been installed in
its proper position. Bolts 50 contain an unthreaded middle portion
located between lower threaded portion 52 and upper threaded
portion 54, as such bone-engaging screws are known to and used by
those skilled in the art.
[0051] A series of snap or C-rings 60 are used with bolts 50 to
securely fasten plate 32 in its proper position. Snap or C-rings 60
are clipped onto upper threaded portion 54 of bolts 50 after lower
threaded portion 52 has been anchored within the appropriate
vertebrae but before plate 32 has been fully installed.
Alternatively, snap or C-rings 60 are clipped onto the middle
unthreaded portion of bolt 50 in embodiments of plate system 30
utilizing such a bolt 50. Finally, a series of nuts 62 are threaded
onto upper threaded portion 54 of bolts 50 to secure plate 32 in
its proper position. It is contemplated that alternative
embodiments of plate system 30 may employ ordinary washers in place
of snap or C-rings 60.
[0052] The preferred method of using hinged plate system 30 is
shown in FIGS. 8-13. Referring to FIG. 8, a bone graft 63 is
inserted between vertebrae to serve as a replacement vertebra.
After selecting a plate 32 of suitable size, two bolts 50 are
affixed within the appropriate vertebrae. To accomplish this, a
pair of holes are drilled into the vertebrae at a 15.degree.
anterior angulation using openings 40 as a guide. Bolts 50 are then
screwed into place through plate 32 to ensure placement in the
proper location. Preferably, upper bolt 50 is placed into the
cephalad portion of opening 40 as shown in FIG. 8 to allow for
compression.
[0053] It is conceivable that other fastening systems could be used
to secure plate 32 to the spine. By way of example only, several
two part screw systems having an outer vertebral screw and a
locking inner screw are taught in a patent application entitled
ANATOMIC POSTERIOR LUMBAR PLATE, filed in the name of Bret A.
Ferree on the same day as this application and hereby incorporated
by reference in its entirety. Such screw systems may be used in
place of bolts 50 in the present invention, as these two part
screws create a "bolt" as understood in relation to the present
invention.
[0054] As shown in FIG. 9, the next step involves flipping
posterior element 32b of plate 32 upwardly away from the vertebrae.
In the alternative, posterior element 32b and/or plate 32 may be
removed in its entirety. In any case, snap rings 60 are applied to
upper threaded portion 54 of bolts 50 to secure them in place. As
shown in FIG. 10, posterior element 32b of plate 32 is then
repositioned over the two bolts 50, by either flipping downward
toward the vertebrae or by reconnecting posterior element 32b to
anterior element 32a along hinged element 34. While compressing
bone graft 63 between the vertebrae, nut 62 is then applied to
upper threaded portion 54 of lower bolt 50, and securely tightened
against plate 32. Preferably, the wrench used to tighten nut 62
onto lower bolt 50 is cannulated to allow insertion of a
screwdriver or other suitable tool to prevent rotation of bolt 50
while nut 62 is threaded onto upper threaded portion 54 of bolt
50.
[0055] With continued reference to FIG. 10, a pair of holes are
then drilled into the vertebrae using openings 36 on the anterior
element 32a as a guide. Bolts 50 can then be affixed into place
through element 32a (FIG. 11). As shown in FIG. 12, anterior
element 32a is then flipped upwardly or removed entirely, and snap
rings 60 are secured on upper threaded portion 54 of bolts 50.
Element 32a of plate 32 can now be returned to its proper position,
and nuts 62 are applied to upper threaded portion 54 of bolts 50
and tightened to completely secure plate 32 against the vertebrae,
as shown in FIG. 13. Optionally, another screw 70 may be inserted
through opening 42 into bone graft 63 (or a cage if one has been
inserted).
[0056] FIG. 14 is a sectional view of a vertebra on which a hinged
plate system 30 of the present invention has been installed. Bolts
50 can be seen penetrating the vertebra. The relative angularity
between bolts 50 provides the force necessary to securely hold
plate system 30 in the proper orientation to promote healing. In
addition, hinged section 34 assists to contour plate 32 to the
convexity of the vertebrae, allowing plate 32 to more effectively
contact the vertebral surface.
[0057] It is contemplated that other modifications could be made on
plate 32 in order to simplify the installation process. By way of
example only, openings 40 on element 32b may be beveled such that
element 32a can be lifted slightly while positioned on upper
threaded portion 54 of bolt 50, allowing snap ring 60 to be
inserted below plate 32 onto bolt 50 without substantial
displacement of element 32a (FIG. 15). FIG. 16 shows a plate 32 in
which openings 40 in element 32a are slotted toward rounded edges
35a, 35b such that element 32a can be easily flipped in an upward
direction.
[0058] An alternate embodiment of the spinal plate system of the
present invention is shown in FIGS. 17-22. Referring to FIGS. 17
and 18, a spinal plate system 100 is shown mounted in position on
the spinal column of a patient. A unitary plate 102 having a
plurality of slots 104a-e is fastened by a plurality of bolts 110
as previously described at vertebrae 106, 108. A bone graft 112 has
been inserted between vertebrae 106, 108 to serve as a replacement
vertebra. Plate 102 contains cutaway edge portions 113a, 113b to
allow the surgeon to visualize the bone graft easily. Bolts 110,
which are shown mounted through slots 104a-d, are held in place by
a plurality of snap-rings 114. Central slot 104e located in the
central region of plate 102 may be used for an additional screw or
bolt through a central vertebra or bone graft. In addition, the
bottom surface of plate 102 may contain a friction surface to allow
better contact with the bone structures.
[0059] FIG. 19 shows a cross-sectional view of the plate of FIG.
17. Preferably, plate 102 has a thickness of approximately 7 mm,
and is curved to allow for better contact with the vertebral
surface. Anterior slots 104a, 104b, which each have a preferred
width of approximately 7 mm, are substantially perpendicular to the
upper and lower surfaces of plate 102. Posterior slots 104c, 104d,
which each have a preferred width of approximately 7 mm, are
oriented at approximately a 15.degree. anterior angulation between
the upper and lower surfaces of plate 102. The preferred length of
plate 102 ranges from 60 mm to 100 mm. The preferred width of plate
102 is approximately 20 mm at its widest portion, and approximately
12 mm across cutaway sections 112a, 112b.
[0060] Plate 102 can be shaped to more easily fit the spine when
used in different areas. FIG. 20 shows a plate 102 which is angled
15.degree. in the forward (i.e. anterior) direction to compensate
for kyphotic conditions, while FIG. 21 shows a plate 102 which is
angled 15.degree. in the reverse (i.e. posterior) direction to
compensate for lordotic conditions. Finally, FIG. 22 depicts a
shorter plate 102, which may be used in situations where longer
plates are impracticable or unnecessary.
[0061] While the present invention has been shown and described in
terms of preferred embodiments thereof, it should be understood
that this invention is not limited to any particular embodiment,
and that changes and modifications may be made without departing
from the true spirit and scope of the invention as defined in the
appended claims.
* * * * *