U.S. patent application number 17/062702 was filed with the patent office on 2021-01-28 for hinged anterior cervical plate system.
This patent application is currently assigned to FREEDOM INNOVAATIONS, LLC. The applicant listed for this patent is FREEDOM INNOVATIONS, LLC. Invention is credited to Avery M. JACKSON, III.
Application Number | 20210022777 17/062702 |
Document ID | / |
Family ID | 1000005150317 |
Filed Date | 2021-01-28 |
United States Patent
Application |
20210022777 |
Kind Code |
A1 |
JACKSON, III; Avery M. |
January 28, 2021 |
Hinged anterior cervical plate system
Abstract
A folding anterior cervical locking plate system for stabilizing
the cervical spine in a spinal fusion procedure. The plate system
has at least two plate sections hinged together by a hinge
structure at adjacent ends for pivoting movement of the plate
sections relative to one another through at least 90.degree. in
each of two directions. A first hole in each plate section enables
visualization of the underlying graft. A locking plate spans
adjacent ends of the plate sections and holes in the locking plate
are aligned with holes in adjacent plate sections so pedicle screws
inserted through the holes in the locking plates extend through the
holes in the plate sections to secure the system to the vertebral
bodies and stabilizes the cervical spine. In one embodiment the
locking plate slides in guide channels on opposite side edges of
the plate sections.
Inventors: |
JACKSON, III; Avery M.;
(Grand Blanc, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FREEDOM INNOVATIONS, LLC |
Grand Blanc |
MI |
US |
|
|
Assignee: |
FREEDOM INNOVAATIONS, LLC
Grand Blanc
MI
|
Family ID: |
1000005150317 |
Appl. No.: |
17/062702 |
Filed: |
October 5, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15438603 |
Feb 21, 2017 |
10828071 |
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17062702 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 17/7059 20130101;
A61B 17/8057 20130101; A61B 17/8023 20130101 |
International
Class: |
A61B 17/70 20060101
A61B017/70; A61B 17/80 20060101 A61B017/80 |
Claims
1. A folding plate system for stabilizing adjacent vertebral bodies
in a cervical spine, said plate system comprising: at least two
plate sections connected to one another via a uniaxial rotating
hinge, the uniaxial rotating hinge having only a single axis of
rotation which extends parallel to adjacent ends of the at least
two plate sections such that the at least two plate sections are
pivotable out of plane with one another about the single axis of
rotation; a peripherally enclosed visualization hole in each of the
at least two plate sections arranged and disposed for visualization
of an underlying graft site; and a plurality of screw holes through
each of the at least two plate sections for receiving screws
inserted therethrough, each of the plurality of screw holes having
a cross-sectional area less than the visualization hole.
2. The folding plate system of claim 1, wherein the at least two
plate sections are made of titanium.
3. The folding plate system of claim 1, wherein each of the at
least two plate sections measures 2-3 mm in thickness, 6-10 mm in
width, and 20-30 mm in length.
4. The folding plate system of claim 1, further including a locking
plate sized to extend between the at least two plate sections, the
locking plate having a plurality of holes therethrough spaced to
align with at least some of the plurality of screw holes in the at
least two plate sections such that screws inserted through the
plurality of holes in the locking plate and the at least some of
the plurality of screw holes in the at least two plate sections fix
the at least two plate sections so as to resist pivoting movement
of the at least two plate sections relative to one another about
the single axis of rotation.
5. The folding plate system of claim 4, wherein the locking plate
extends across the uniaxial rotating hinge.
6. The folding plate system of claim 4, further including a guide
channel extending longitudinally along each of opposite side edges
of each of the at least two plate sections such that the locking
plate is retained and guided at opposite side edges in the guide
channels for sliding movement in the guide channels from an
unlocked position on top of one of the at least two plate sections
to a locked position spanning the uniaxial rotating hinge
connecting the at least two plate sections.
7. The folding plate system of claim 1, wherein locking plate is
made of titanium.
8. The folding plate system of claim 1, wherein the uniaxial
rotating hinge includes a pair of support arms extending from a
first plate section of the at least two plate sections, a pivot pin
supported by the pair of support arms, and a bore extending
transversely in a second plate section of the at least two plate
sections, the pin being rotatably received in the bore to pivotally
connect together said the plate section and the second plate
section.
9. The folding plate system of claim 8, wherein: a slot extends
longitudinally in the second plate section in angularly offset
relation below a plane of the second plate section, said slot
opening into the bore and enabling the pivot pin to be inserted
endwise into the bore, the slot terminating in spaced relation to
an adjacent side edge of the second plate section, wherein an end
of the slot forms a stop that limits how far the pivot pin may be
inserted into the bore; and notches formed in the second plate
section in spaced locations corresponding to locations of the
support arms on the first plate section when the pivot pin of said
first plate section is fully inserted into the bore of the second
plate section, the notches extending transversely to the slot and
terminating at upper and lower extremities in upper and lower
surfaces, respectively, of the second plate section such that the
plate sections are pivotable up and down relative to one
another.
10. The folding plate system of claim 1, wherein the at least two
plate sections consist of a first plate section and a second plate
section so as to form a two-level system.
11. The folding plate system of claim 1, wherein the at least two
plate section includes a first plate section and a second plate
section connected to one another via the uniaxial rotating hinge
and a third plate section connected to the second plate section via
a second uniaxial rotating hinge so as to form a three-level
system.
12. The folding plate system of claim 1, wherein the at least two
plate sections are pivotable out of plane with one another about
the single axis of rotation via the uniaxial rotating hinge through
at least 90.degree. in each of two directions relative to one
another.
13. The folding plate system of claim 1, wherein at least one of
the at least two plate sections includes an end opposite the
uniaxial rotating hinge which is free of a hinge-forming
structure.
14. The folding plate system of claim 1, wherein the plurality of
screw holes through each of the at least two plate sections
includes four screw holes through each of the at least two plate
sections.
15. The folding plate system of claim 14, wherein the four screw
holes are disposed adjacent to four corners of each of the at least
two plate sections.
16. The folding plate system of claim 1, wherein the visualization
hole is disposed at a center of each of the at least two plate
sections.
17. A method for stabilizing adjacent vertebral bodies in a
cervical spine, comprising: inserting a folding plate system
through an in incision into a position adjacent to an anterior
surface of the cervical spine while the folding plate system is in
a folded configuration, the folding plate system including: at
least two plate sections connected to one another via a uniaxial
rotating hinge, the uniaxial rotating hinge having only a single
axis of rotation which extends parallel to adjacent ends of the at
least two plate sections such that the at least two plate sections
are pivotable out of plane with one another about the single axis
of rotation; a peripherally enclosed visualization hole in each of
the at least two plate sections arranged and disposed for
visualization of an underlying graft site; and a plurality of screw
holes through each of the at least two plate sections for receiving
screws inserted therethrough, each of the plurality of screw holes
having a cross-sectional area less than the visualization hole,
then unfolding the folding plate system to a flattened
configuration by rotating the at least two plate section relative
to one another into a planar relationship; and attaching the
folding plate system to the adjacent vertebral bodies with a
plurality of screws.
18. The method of claim 17, further including positioning a locking
plate extending between the at least two plate sections, and
rotationally fixing the at least two plate sections with the
locking plate so as to resist pivoting movement of the at least two
plate sections relative to one another about the single axis of
rotation.
19. The method of claim 18, wherein the locking plate includes a
plurality of holes therethrough spaced to align with at least some
of the plurality of screw holes in the at least two plate sections,
and rotationally fixing the at least two plate sections with the
locking plate includes inserting screws through the plurality of
holes in the locking plate and the at least some of the plurality
of screw holes.
20. The method of claim 19, wherein the locking plate is sized to
extend across the uniaxial rotating hinge and the at least two
locking plates include a guide channel extending longitudinally
along each of opposite side edges of each of the at least two plate
sections, and positioning the locking plate includes sliding the
locking plate through the guide channel such that the locking plate
is retained at opposite side edges in the guide channels in a
locked position spanning the uniaxial rotating hinge.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of and claims priority to
and all benefit of U.S. patent application Ser. No. 15/438,603,
filed on Feb. 21, 2017, the entire disclosure of which is fully
incorporated herein by reference.
TECHNICAL FIELD
[0002] This invention relates to an implantable plate system for
fixation at the anterior face of the vertebral bodies of the
cervical spine to stabilize adjacent cervical vertebrae as an
adjunct to treatment of spinal disorders. More particularly, the
locking plate system of the invention has hinged together sections
that can be folded relative to one another to facilitate placement
in the area being treated and unfolded in place to span the desired
levels. Different numbers of plats can be quickly and easily
connected together or disconnected when desired to change the
number of levels the plate system spans.
BACKGROUND ART
[0003] The cervical spine comprises seven cervical vertebrae named
by their position in order from C1 adjacent the skull to C7
adjacent the thoracic spine. The C1 vertebra supports the skull and
is named the atlas. The C2 vertebra is named the axis and provides
the axis upon which the skull and atlas rotate when the head is
moved side to side. Intervertebral discs are located between
adjacent vertebra except the first two cervical vertebrae, C1 and
C2. Motion between adjacent vertebrae occurs through the disc and
two facet joints.
[0004] As people age the discs lose some of their water content and
consequently some of their shock absorbing ability. Tears may form
without symptoms in the outer ring or annulus of the disc and heal
by forming scar tissue. Scar tissue is weaker than normal tissue,
and as the disc continues to wear it begins to collapse and the
space between adjacent vertebrae becomes smaller, affecting
alignment of the facet joints in the back of the spine. The change
in the way the bones fit together causes abnormal pressure on the
articular cartilage, and over time this abnormal pressure causes
wear and tear arthritis (osteoarthritis) of the facet joints.
[0005] Other disorders include spinal disc herniation, fractured or
dislocated vertebrae, spinal stenosis, and cervical spondylotic
myelopathy. Most neck pain is due to degenerative changes. Perhaps
the most serious of the problems caused by degeneration of the
spinal segments in the cervical spine is the condition of spinal
stenosis, which typically occurs during the later stages of spinal
degeneration. In the cervical spine this condition is sometimes
called cervical myelopathy.
[0006] In cervical spinal stenosis, the spinal canal narrows and
can squeeze and compress the nerve roots where they leave the
spinal cord, or the spinal cord itself may be compressed. Spinal
stenosis is most common in people older than age 50. The aging
process can cause a bulging of the discs or a thickening of tissues
that connect bones. These disorders can result in nerve
compression, leading to paralysis, numbness, or pain.
[0007] The vast majority of patients who have neck pain will not
require any type of operation. However, in some cases degenerative
changes in the cervical spine can lead to a very serious condition
where there is too much pressure on the spinal cord. When this
condition occurs, the entire spinal cord is in danger.
[0008] One surgical option is to remove the pressure on the spinal
cord by removing the offending disc or discs, called a discectomy,
and to place a bone graft in the space left by removal of the disc.
A fusion surgery is almost always done at the same time as the
discectomy in order to stabilize the cervical segments. Together,
the combined surgery is commonly referred to as an ACDF surgery,
which stands for Anterior Cervical Discectomy and Fusion. It may be
done for one level or for more than one level of the cervical
spine. While this surgery is most commonly done to treat a
symptomatic cervical herniated disc, it may also be done for other
cervical degenerative diseases.
[0009] In the case of a degenerative vertebra, the degenerative
vertebra or vertebrae are removed and replaced with a bone graft to
fill the space left by removal of the degenerative vertebra. This
procedure is called a corpectomy and strut graft. Any bone spurs
pushing on the spinal cord are also removed during a corpectomy
procedure. A corpectomy is often performed in association with some
form of discectomy. In either case, the graft heals over time to
create a spinal fusion where the disc or vertebral body has been
removed.
[0010] Although the cervical spine can be approached from either
the front (anterior approach) or from the back (posterior
approach), the discs are more directly accessible from the front of
the neck and if conditions permit, most surgeons favor an anterior
approach. An anterior approach results in less disruption of the
normal musculature and it is also easier to maintain the normal
alignment of the spine. Many degenerative conditions of the spine
cause a loss of the normal lordosis (gentle curvature of the
spine). By opening up the front of the spine in an anterior
approach, this lordosis can be reestablished.
[0011] The anterior approach provides better access to the spine
because almost the entire cervical spine is accessible. It provides
access to the spine through a relatively uncomplicated pathway, and
there generally is less postoperative pain. In a discectomy, the
discs can be reached without disturbing the spinal cord, spinal
nerves, and neck muscles. All things being equal, the patient tends
to have less incisional pain from this approach than from a
posterior operation. Depending on the particular symptoms, one disc
(single-level) or multiple discs (multi-level) may be removed.
[0012] In performing anterior fusion surgery on the cervical spine,
a cut is made either transversely or longitudinally in the front of
the patient's neck, depending upon the surgeon's training and the
levels of surgical fusion. A transverse incision can be made when a
one or two level fusion is to be made. When more than a two level
fusion is to be made, a longitudinal incision is generally
required. The incision length depends on the size of the person and
the number of levels to be treated.
[0013] In accordance with one procedure for anterior access to the
cervical spine, a transverse incision 2-4 centimeters long,
depending on the size of the patient and the number of levels, is
made just off the midline in the front of the neck, and the
cervical fascia is gently divided in a natural plane, between the
esophagus and carotid sheath. Small retractors and an operating
microscope are used to allow the surgeon to visualize the anterior
vertebral body and discs. The arteries and nerves in the neck are
protected while the muscles and other tissues are moved to the
side.
[0014] After the spinal cord and nerve roots have been decompressed
at the appropriate levels, the portions removed must be
reconstructed so as to support the normal loads of the cervical
spine by inserting either a bone graft within each disc space, or
inserting a longer graft, referred to as a strut graft, to span the
space left by removing one or more vertebral bodies. The intent is
to promote the formation of a living bridge of bone between the
vertebrae above and below the space formed by removal of one or
more vertebrae. The patient's own bone or human cadaver bone may be
used to form the graft, or a synthetic scaffold may be used into
which bone graft is inserted.
[0015] Plating systems have been developed in the prior art to
fixedly connect two or more vertebrae to each other and stabilize
the cervical spine while the fusion heals. These plating systems
typically comprise plates made of titanium and designed to be
secured with screws to the vertebrae above and below the fusion. A
plate spans the gap between two adjacent vertebrae, and the screws
go through holes in the plate and into the vertebrae. Each vertebra
may receive one screw or two or more screws depending on the type
of plate which is utilized.
[0016] The plate system can span one level, i.e. the space between
two adjacent vertebrae, or two levels, i.e. the spaces between
three adjacent vertebrae, or more levels depending upon the
requirements for treating a particular disorder. Once the fusion
bone and cervical plate are in place, the vertebrae are stabilized
and the bony fusion occurs according to biological healing
principles.
[0017] Conventional plates are either pre-assembled by the
manufacturer into multiple level options, or the plate is assembled
by the surgical scrub technicians on the back table then handed to
the surgeon for insertion. Plates are usually provided in sets
having a range of sizes so as to provide for such features as
biological diversity in size, the numbers of segments to be joined,
and the length of the portions of bone to be joined. Plating
systems are typically designed for joining from two to five
vertebrae.
[0018] To place the cervical plates, the tissue in front of the
vertebrae must be moved to one side to expose the vertebrae. This
involves moving the larynx, the pharynx, the esophagus, carotid
artery, several important nerves, and dissecting several muscles.
Swallowing issues can arise after surgery, particularly when
multiple levels are involved, due to the trauma caused when placing
a long rigid plate in a small opening with anatomic structures in
close proximity. Forcing a large plate for a multi-level fusion
into a smaller opening could lead to a dysfunction in esophageal
motility, which can affect the swallowing mechanism and the
voice.
[0019] After gaining access to the prevertebral space and
performing the discectomy and fusion, an anterior plate sized to
span the number of levels involved, e.g. connecting two motion two
vertebrae or one motion segment, is selected. The plate is then
placed with fingers or forceps onto the anterior vertebral body
surface and screws are inserted through the plate and into the
vertebrae to secure the plate to the vertebrae.
[0020] It can be extremely difficult to safely place longer
multi-level plates into the resection bed because it is difficult
to safely retract the soft tissues that must be moved out of the
way to place the longer plate for multilevel constructs. There is a
potential for resultant esophageal tear or stretch injuries and a
risk of causing dysphagia, especially with retraction of the
cephalad oropharyngeal tissues when placing the plate. The plate is
usually larger than the surgical dissection and requires extra
retraction or soft tissue manipulation. Traversing venous or
arterial structures are also at risk when placing longer plates.
Swallowing dysfunction of some degree is likely. A hoarse voice
from injury to the laryngeal nerve or superior thyroid nerve may
occur during plate placement and manipulation.
[0021] One known complication arising from anterior cervical fusion
with conventional plating systems is injury to the esophagus. The
risk goes up as the dimensions of the plate increase. Injury to the
esophagus can result during surgery when a large, rigid prior art
plating system is forced into position through the surgical wound,
leading to erosion through the esophagus.
[0022] Accordingly, there is need for a plate system that in
multi-level fusion surgery avoids the need to force a large plate
through the small surgical opening and past surrounding tissue.
SUMMARY OF THE INVENTION
[0023] The present invention is a folding plate system that avoids
the need to force a large plate into the smaller soft tissue space
when multi-level anterior fusion is being performed. The plating
system of the invention allows the surgeon to avoid soft tissue
injury leading to swallowing dysfunction or vascular injury. The
plate system is folded to its folded configuration and in this form
inserted through the incision and positioned at the anterior
surface of the cervical spine. It is then gently lengthened by
flattening the plate completely from its folded position into its
unfolded final position. This maneuver is performed while the plate
system is sitting on the anterior surface of the cervical
vertebrae. The surgeon does not have to wrestle with multi-level
plates by stretching soft tissues for plate placement. Holes in the
plates provide visualization of the end plates of the underlying
vertebral bodies where the disc spaces are located.
[0024] The multi-link plate system of the invention removes the
risk of esophageal injury because the plate is not forced into the
surgical wound. Instead, it is placed in segments in a modular
fashion or an accordion fashion and then expanded after it is
positioned at the front of the spine below the esophagus and other
soft tissues.
[0025] The plate system of the invention comprises two or more
plate sections that each span a single level. A single plate
section could be used for one level and multiple plate sections
hinged together for multiple levels. Thus, two plate sections are
hinged together for two levels, three plate sections are hinged
together for three levels, and so on. The hinged-together plate
sections can be folded relative to one another to reduce the length
of the system for easier insertion into the space being operated
on, especially in multi-level fusion surgery.
[0026] A locking plate is extended across the hinged connection
between two adjacent plate sections to lock the plate sections
against movement after they are unfolded and secured in place on
the bony anatomy.
[0027] The plate sections are able to be folded enough relative to
one another (120.degree. in either direction in a specific example)
so that the system of hinged together plate sections is
significantly shorter in length when folded than a conventional
one-piece multi-level plate. After insertion, the folded plate
sections can be unfolded internally to place them in position on
the spine. They can be folded up again internally if the plate
system needs to be removed for some reason, e.g. exchanged for
another plate system.
[0028] In a preferred example, each plate section measures 2-3 mm
in thickness, 6-10 mm in width, and 20-30 mm in length. The overall
length of a plate system would depend upon the number of levels
involved. The locking plates preferably are 1-2 mm thick and each
one is sized to overlap the joint between adjacent plate sections.
In a preferred embodiment, the plate sections and locking plate are
made of titanium, but in an alternate embodiment they can be 3-D
printed.
[0029] In one embodiment, guide channels are on opposite side edges
of the top of the plate sections and the locking plate is slidably
guided at its opposite edges in these channels so that it can be
moved from an unlocked position to a locked position in spanning
relationship across the hinge between adjacent plate sections.
Holes in the locking plate can line up with holes in the plate
sections so that screws inserted through the holes secure the
locking plate and the plate sections in position.
[0030] In another embodiment, the guide channels are omitted and
the locking plate is added after the plate sections are in
position. No sliding mechanism is required. In this configuration,
the screws that hold the locking plate in position across the hinge
also hold the plate sections to the vertebral body.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The foregoing as well as other objects and advantages of the
invention will become apparent from the following detailed
description when considered in conjunction with the accompanying
drawings, wherein like reference characters designate like parts
throughout the several views, and wherein:
[0032] FIG. 1 is a schematic front representation of the cervical
spine.
[0033] FIG. 2 is a schematic side representation of the cervical
spine.
[0034] FIG. 3 is a schematic cross sectional view of the cervical
spine, showing a typical bone spur and herniated disc.
[0035] FIG. 4 is a fragmentary schematic front view of a patient's
neck, showing a typical transverse incision made in an anterior
fusion surgery procedure.
[0036] FIG. 5 is an enlarged fragmentary schematic front view of a
patient's neck after retractors have been used to open the incision
and move adjacent tissue aside to gain access to the cervical
spine.
[0037] FIG. 6 is an isometric view of a prior art plate for single
level fusion.
[0038] FIG. 7 is an isometric view of a prior art plate for two
level fusion.
[0039] FIG. 8 is a schematic isometric representation of a prior
art plate for single level fusion.
[0040] FIG. 9 is a schematic isometric representation of a prior
art plate for two level fusion.
[0041] FIG. 10 is a schematic isometric representation of a prior
art plate for three level fusion.
[0042] FIG. 11 is an isometric view of a first form of plate system
according to the invention, wherein two plate sections are hinged
together for use in a two level fusion.
[0043] FIG. 12 is an isometric view of the first form of plate
system, wherein three plate sections are hinged together for use in
a three level fusion.
[0044] FIG. 13 is an enlarged, fragmentary, top isometric view of
one end of one of the plate sections in the first form of the
invention.
[0045] FIG. 14 is an enlarged, fragmentary, bottom isometric view
of the end shown in FIG. 13.
[0046] FIG. 15 is a top isometric view of the opposite end of the
plate section shown in FIGS. 11-14.
[0047] FIG. 16 is a top plan view of one of the plate sections in
FIGS. 11-14.
[0048] FIG. 17 is an enlarged fragmentary sectional view taken
along line 17-17 in FIG. 16.
[0049] FIG. 18 is an enlarged fragmentary sectional view taken
along line 18-18 in FIG. 16.
[0050] FIG. 19 is an exploded, fragmentary, top isometric view
showing how two plate sections are oriented so that they can be
assembled at the hinged ends.
[0051] FIG. 20 is a fragmentary top plan view showing two plate
sections assembled together at the hinged ends.
[0052] FIG. 21 is an enlarged fragmentary view in elevation of two
plate sections hinged together and illustrating the range of
pivoting movement between them.
[0053] FIG. 22 is an exploded top isometric view of one of the
screws and a locking plate that spans the hinged connection between
two hinged together plate sections.
[0054] FIG. 23 is a top plan view of two hinged together plate
sections and a locking plate slidably engaged at its opposite side
edges in the channels on one of the plate sections prior to the
locking plate being moved across the hinged connection between the
two plate sections.
[0055] FIG. 24 is a top plan view showing the locking plate of FIG.
23 moved into operative position across the hinged connection
between the two plate sections.
[0056] FIG. 25 is a fragmentary side view in elevation of the plate
sections and locking plate of FIG. 24.
[0057] FIG. 26 is a schematic isometric view illustrating how three
hinged together plate sections can be folded to shorten the overall
length.
[0058] FIG. 27 is a fragmentary front view of a patient's neck,
showing a transverse incision expanded with retractors and a single
level plate section shown inn full lines in position on the
cervical spine, with an additional plate shown in broken lines for
a two level fusion.
[0059] FIG. 28 is a top isometric view of an alternate form of the
invention for two level fusion, wherein the guide channels are
omitted.
[0060] FIG. 29 is a top isometric view of the form of the invention
shown in FIG. 28, but wherein an additional plate section is added
for three level fusion.
[0061] FIG. 30 is an exploded top isometric view of two hinged
together plate sections in that form of the invention shown in FIG.
28, and a locking plate in position to be secured to the plate
sections in spanning relationship to the hinged connection.
[0062] FIG. 31 is a fragmentary side view of two plate sections and
a locking plate secured to the face of two vertebrae.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0063] A representative front view of a cervical spine CS is shown
in FIG. 1, and the anterior surface A and posterior surface P are
indicated in the side view of FIG. 2.
[0064] A cross section of the cervical spine CS is shown in FIG. 3.
The section is taken through a disc 10 and its associated annulus
11, with the annulus shown ruptured and a herniation 12 of the disc
compressing a nerve 13 leading from the spinal cord 14. A bone spur
15 is also shown compressing the nerve 13.
[0065] A transverse incision 16, offset slightly to one side of the
cervical spine, is made in the front of a patient's neck 17 in FIG.
4. It should be understood that depending upon the requirements of
a particular procedure, the incision can be made either
transversely, as shown, or longitudinally.
[0066] Retractors 18 are being used in FIG. 5 to spread open the
incision and hold other tissue to the side to expose the vertebrae
19 and discs 20 at the anterior surface of the cervical spine.
[0067] FIGS. 6-10 depict prior art devices. A prior art plate for
single level fusion is shown at 21 in FIG. 6, and a prior art plate
for two level fusion is shown at 22 in FIG. 7. The two level plate
22 is a single unitary piece with portions 23 and 24 adapted to be
positioned over adjacent discs, for example.
[0068] FIG. 8 is a schematic illustration of a prior art plate 25
for single level fusion. In this particular example, the plate has
four holes 26 for receiving screws to fasten the plate to vertebral
bodies and a single large hole 27 to enable visualization of the
graft site and end plates.
[0069] FIG. 9 is a schematic illustration of a prior plate 28 for
two level fusion. This plate is of one-piece construction and
comprises two sections 29 and 30 adapted to overlie respective
fusion sites. Each has holes 31 for receiving screws to fasten the
plate to vertebral bodies, and a large centrally located hole 32 to
enable visualization of the graft sites and end plates.
[0070] A prior art plate 33 for three level fusion is shown in FIG.
10. This plate is also of one-piece construction and has three
sections 34, 35 and 36 adapted to overlie respective fusion sites.
In this particular example, each section has four holes for
receiving screws at 37 to fasten the plate to vertebral bodies, and
a large centrally located hole 38 to enable visualization of the
graft sites and end plates.
[0071] A two level plate system according to a first form of the
invention is indicated generally at 40 in FIG. 11. This plate
system comprises two plate sections 41 and 42 hinged together at 43
at adjacent ends for pivoting movement through at least 90.degree.
in each direction, and preferably through 120.degree.. Each plate
section has four holes 44 in the specific example shown for
receiving screws to fasten the plate system to vertebral bodies. A
large central hole 45 is provided to enable visualization of the
graft sites and end plates. Guide channels 46 extend along opposite
side edges of each plate section on the upper surface thereof to
receive and guide a locking plate as described hereinafter.
[0072] A three level plate system according to the first form of
the invention is indicated generally at 50 in FIG. 12. This plate
system comprises three plate sections 51, 52 and 53 hinged together
at 43 at adjacent ends. Each plate section has four holes 44 in the
specific example shown for receiving screws to fasten the plate
system to vertebral bodies, and a large central hole 45 to enable
visualization of the graft sites and end plates. Guide channels 46
extend along opposite side edges of each plate section on the upper
surface thereof to receive and guide a locking plate as described
hereinafter. Additional levels can be added, depending upon the
requirements of a particular procedure. Cervical fusion surgery can
involve up to seven levels.
[0073] It should be understood that a different number of holes 44
could be provided in the forms of invention described above, but
four holes are typical and are illustrated and described in the
specific examples disclosed herein.
[0074] In the forms of the invention shown in FIGS. 11 and 12, the
manufacturer could supply sets of two, three, four, or more plate
sections hinged together and the surgeon would select an
appropriate set, depending upon the number of levels involved. In
an alternate embodiment, some or all of the plate sections could
have hinge-forming structures at both ends and the surgeon or
surgical assistant could assemble as many plate sections as
necessary for a particular procedure.
[0075] Details of the hinged ends are shown in FIGS. 13-19.
Referring first to FIGS. 11, 13, 14, 17 and 18, the ends 60 and 61
of plate sections 41 and 42 are rounded and a cylindrical bore 62
(see FIGS. 13 and 14) extends transversely through end 60 of plate
section 41 from one side of the plate section to the opposite side,
which is optionally closed at 63 (see FIGS. 14 and 16). An annular
groove 64 is formed in the wall of the bore near the open end (see
FIGS. 14 and 20).
[0076] A slot 65 is formed in a lower portion of the rounded end
60, spaced counterclockwise at an angle A of about 30.degree. from
a vertical plane drawn through the longitudinal centerline of the
bore 62 (see FIGS. 14 and 18). The slot opens into the bore 62 over
most of the width of the plate section 41 except for a short
section 66 where the slot terminates short of the closed end of the
bore.
[0077] Notches 67 are formed in the rounded end 60 transversely to
the slot 65 and intersect the slot at two spaced apart locations
along the length of the bore 62. The notches terminate at their
upper end 68 in the top of the plate section and at their lower end
69 in the bottom of the plate section, the terminal ends being
spaced rearwardly at an angle B of about 30.degree. from a vertical
plane drawn through the longitudinal centerline of the bore 62 (see
FIG. 17).
[0078] As seen best in FIGS. 15, 16, 19 and 20, a pair of support
arms 70 extend from the rounded end 61 of plate section 42,
supporting a cylindrically shaped hinge pin 71 in spaced relation
to the end 61. An annular bead 72 on the outer surface of pin 71
near one end engages in groove 64 to restrain pin 71 against axial
movement in the bore 62 when the pin is fully inserted into the
bore. The closed end 63 of the bore limits insertion of the pin
into the bore so that the bead 72 engages in the groove 64 when the
parts are assembled into operative position.
[0079] To assemble the plate sections 41 and 42 or 51, 52 and 53
together, or other multiples of plate sections (not shown), the
plate sections are angled relative to one another as shown in FIG.
19 so that plate section 42, for example, is at an angle A' of
60.degree. below the plane of plate section 41. The pin is inserted
endwise into the bore 62 until one of the support arms 70 engages
the closed end 66 of slot 65 (see FIG. 14), and/or, if provided,
the end of the pin 71 abuts against closed end 63 of bore 62. This
lines up the support arms 70 with notches 67 so that the plates 41
and 42 can be pivoted 120.degree. in either direction (see FIG.
21). This also lines up the bead 72 with groove 64 which when
engaged form a detent to prevent relative axial movement between
pin 71 and bore 62 and prevent the two plate sections from
unintentionally disconnecting from one another but permitting it
when sufficient force is exerted.
[0080] As noted above, when connected the plate sections can pivot
120.degree. in either direction relative to one another as shown in
FIG. 21. This facilitates insertion of the plate system into
position on the cervical spine without having to force it into
surrounding tissue. When the plate system is in position on the
anterior surface of the cervical vertebrae it is secured in place
with screws passed through the holes 44 as explained
hereinafter.
[0081] To lock the pivotally connected plate sections in their
operative unfolded position and stabilize the spine to which they
are attached, a locking plate 80 spans each hinged area 43. The
locking plate is secured with screws 81 extended through openings
82 in the locking plate 80 and through the openings 44 in the plate
sections 41 and 42 and then into the underlying vertebrae. In this
regard, the holes 82 are located so that they line up with the
holes 44 when the locking plate is in the positions shown in FIGS.
23 and 24.
[0082] In that embodiment of the invention shown in FIGS. 11-25,
the locking plate is carried between the opposed pair of channels
46 on one or more of the plate sections, depending upon how many
levels the plate system is intended to span. For a three level
system as shown in FIG. 12, two locking plates would be required.
In the two level plate system shown in FIGS. 11, 23 and 24, one
locking plate 80 would be required and it would normally rest on
either plate section 41 or plate section 42, depending upon how the
plate system is oriented. After the plate sections are in position
on the anterior surface of the cervical spine, the locking plate is
slid across the hinged area 43 in the guide channels 46 and screws
81 are inserted through the openings 82 in the locking plate and
openings 44 in the plate sections and into the vertebrae to secure
all the components in place. Preferably, the locking plate is
positioned at the caudal end of the plate system and pushed
cranially to move it into locking position.
[0083] FIG. 26 is a schematic illustration of how a three level
system 50 can be folded to shorten its length for easier insertion
into place, and FIG. 27 shows the system in position on the
anterior surface of the cervical spine.
[0084] An alternate embodiment of the invention for two level
fusion is indicated generally at 40' in FIG. 28. In this form of
the invention, the guide channels 46 are omitted, and as shown in
FIGS. 30 and 31, the locking plate 80 is placed on top of the plate
sections 41', 42' in spanning relationship to the hinged area 43
after the plate sections are positioned on the anterior face of the
cervical spine. Screws 81 are then inserted through the holes 82 in
the locking plate and through the aligned holes 44 in the plate
sections 41' and 42' and into the vertebral bodies 19. In all other
respects this form of the invention is identical to that form shown
in FIGS. 11-27.
[0085] FIG. 29 shows a three level variation 50' of the system 40'
illustrated in FIGS. 28 and 30. This system is identical to that
shown in FIGS. 28 and 30 except that an additional level is added.
In this regard, it should be understood that additional levels
could similarly be added, depending upon the requirements of the
procedure being performed.
[0086] While particular embodiments of the invention have been
illustrated and described in detail herein, it should be understood
that various changes and modifications may be made to the invention
without departing from the spirit and intent of the invention as
defined by the scope of the appended claims.
* * * * *