U.S. patent application number 15/224629 was filed with the patent office on 2017-02-02 for odontoid bullet.
The applicant listed for this patent is Intrepid Orthopedics. Invention is credited to Lee A. Strnad.
Application Number | 20170027617 15/224629 |
Document ID | / |
Family ID | 57886699 |
Filed Date | 2017-02-02 |
United States Patent
Application |
20170027617 |
Kind Code |
A1 |
Strnad; Lee A. |
February 2, 2017 |
ODONTOID BULLET
Abstract
Cervical fixation devices, systems and methods for repairing
odontoid fractures to the C2 vertebral body, including an anchoring
feature that crosses the fracture site to be positioned external to
the fractured bone fragment and which provides compressive and
radial forces externally to the bone to immobilize the bone
fragment(s) for fixation to the main bone structure.
Inventors: |
Strnad; Lee A.; (Richfield,
OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Intrepid Orthopedics |
Richfield |
OH |
US |
|
|
Family ID: |
57886699 |
Appl. No.: |
15/224629 |
Filed: |
July 31, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62199961 |
Jul 31, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 17/7059 20130101;
A61B 2017/0409 20130101; A61B 2017/0404 20130101; A61B 17/0401
20130101; A61B 17/7053 20130101; A61B 17/7062 20130101; A61B
2017/0417 20130101 |
International
Class: |
A61B 17/70 20060101
A61B017/70 |
Claims
1. A cervical fixation system, comprising: a first fastening device
for engagement with a first surface portion of a cervical body, the
first fastening device having a generally elongated shape, the
first fastening device having a plurality of openings extending
generally transversely therethrough, at least a first opening of
the plurality of openings positioned proximate to a midpoint of the
generally elongated shape and a second opening of the plurality of
openings positioned proximate to an end of the generally elongated
shape, at least a portion of a side surface of the first fastening
device having a concave shape for engagement with the first surface
portion of the cervical body; a second fastening device having a
side surface for engaging a second surface portion of the cervical
body, the second device having at least one opening formed
therethrough; and a flexible tension member attached between the
first and second fastening devices, the flexible tension member
extending through the first opening of the first fastening device
and the at least one opening of the second fastening device,
wherein when the flexible tension member is tensioned, the first
and second fastening devices apply a compressive force across at
least a portion of the cervical body and an odontoid associated
with the cervical body.
2. The cervical fixation system of claim 1, further comprising a
flexible recovery member attached to the first fastening device,
the flexible recovery member extending through the second opening
in the first fastening device.
3. The cervical fixation system of claim 2, wherein the first
fastening device includes a first end comprising a generally
rounded conical shape.
4. The cervical fixation system of claim 3, wherein the first
fastening device includes a second end comprising a generally
rounded conical shape.
5. The cervical fixation system of claim 1, wherein at least a
portion of a second side surface of the first fastening device
comprises a generally flattened shape.
6. The cervical fixation system of claim 1, wherein the plurality
of openings in the first fastening device further includes a third
opening positioned proximate to a midpoint of the generally
elongated shape, the first and third openings located on opposing
sides of the midpoint of the generally elongated shape.
7. A cervical fixation system, comprising: a first fastening device
for engagement with a first surface portion of a cervical body, the
first fastening device having a generally elongated shape, the
first fastening device having a plurality of openings extending
generally transversely therethrough, at least a first and a second
opening of the plurality of openings positioned proximate to a
central region of the generally elongated shape and a third opening
of the plurality of openings positioned proximate to a first end
region of the generally elongated shape, at least a portion of a
side surface of the first fastening device having surface features
adapted and configured for engagement with the first surface
portion of the cervical body; a second fastening device having a
side surface for engaging a second surface portion of the cervical
body, the second device having at least one opening formed
therethrough; and a flexible tension member attached between the
first and second fastening devices, the flexible tension member
extending through the first and second openings of the first
fastening device and the at least one opening of the second
fastening device, wherein when the flexible tension member is
tensioned, the first and second fastening devices apply a
compressive force across at least a portion of the cervical
body.
8. The cervical fixation system of claim 7, further comprising a
flexible recovery member attached to the first fastening device,
the flexible recovery member extending through the third opening in
the first fastening device.
9. The cervical fixation system of claim 7, wherein the portion of
the side surface of the first fastening device having surface
features adapted and configured for engagement with the first
surface portion of the cervical body comprises a patient-specific
surface.
10. The cervical fixation system of claim 7, wherein an end of the
first fastening device distal from the first end region comprises a
generally blunt rounded shape.
11. The cervical fixation system of claim 7, wherein the first end
region of the first fastening device comprises a rounded tip with
flattened sides.
12. A method of fixating a spinal bone fragment to a spinal bone
comprising: exposing at least a portion of the spinal bone or an
associated patient; placing a guide wire through a portion of the
spinal bone into the spinal bone fragment across a fracture site;
forming a void through at least a portion of the spinal bone and
the spinal bone fragment; inserting a first fastening device and an
attached flexible tension member through the void in the spinal
bone and the spinal bone fragment such that the first fastening
device exits the spinal bone fragment with the first tension member
extending through the void, the first fastening device having a
generally elongated shape and including a plurality of openings
extending generally transversely therethrough, at least a first
opening of the plurality of openings positioned near a midpoint of
the generally elongated shape and a second opening of the plurality
of openings positioned proximate to an end of the generally
elongated shape, at least a portion of a side surface of the first
fastening device shaped for engagement with a surface of the spinal
bone fragment; positioning a second fastening device against the
spinal bone at a location proximate to the void, at least a portion
of the first tension member extending through an opening in the
second fastening device; and tensioning the first tension member to
draw the first fastening device towards the second fastening
device, thereby causing a compressive force to be applied across
the fracture site.
13. The method of claim 12, wherein the spinal bone comprises a C2
cervical body of the patient's spine and the spinal bone fragment
comprises an odontoid bone fragment.
14. The method of claim 12, wherein bi-planer fluoroscopy is
performed to guide placement of at least one of the guide wire and
the first fastening device.
15. The method of claim 12, wherein the first fastening device
further includes a flexible recovery member attached through the
second opening, with at least a portion of the flexible recovery
member extending through the void in the spinal bone and the spinal
bone fragment.
16. The method of claim 15, further comprising the steps of
severing the attached flexible tension member and subsequently
tensioning the flexible recovery member to align a longitudinal
axis of the first fastening device with the void in the spinal bone
and the spinal bone fragment, and drawing the first fastening
device through the void in the spinal bone and the spinal bone
fragment, thereby removing the first fastening device from the
spinal bone and the spinal bone fragment.
17. The method of claim 12, further comprising the steps of:
obtaining a preoperative image of at least a portion of the spinal
bone fragment; and selecting the first fastening device from a kit
containing a plurality of fastening devices of different sizes, the
selected first fastening device including the side surface portion
shaped for engagement with the preoperatively imaged portion of the
spinal bone fragment.
18. The method of claim 13, further comprising the steps of:
obtaining a preoperative image of at least a portion of the
odontoid bone fragment; and selecting the first fastening device
from a kit containing a plurality of fastening devices of different
sizes, the selected first fastening device including the side
surface portion shaped for engagement with the preoperatively
imaged portion of the odontoid bone fragment.
19. The method of claim 13, further including adjusting alignment
of the odontoid to an anatomically desired position.
20. The method of claim 12, further including adjusting alignment
of the spinal bone fragment to an anatomically desired position.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent Application Ser. No. 62/199,961 entitled "ODONTOID BULLET,"
filed Jul. 31, 2015, the disclosure of which is incorporated by
reference herein in its entirety.
TECHNICAL FIELD
[0002] The present invention relates generally to fixation and
anchoring systems for surgical applications and, in particular,
relates to an adjustable retaining system for anchoring bone
fragments in spine surgery.
BACKGROUND
[0003] In order to effect natural healing of a fractured bone, the
fractured portions of the bone must generally be kept together for
a lengthy period of time in order to permit the recalcification and
bonding of the fractured portions to the remaining bone. In many
cases, adjoining portions of a fractured bone can be repositioned
and maintained in an adjacent relationship (to allow healing of the
bone) by being clamped together or otherwise attached to one
another by means of a pin or a screw driven through the rejoined
portions. In various areas of the body, such as in the cranium or
spinal bones, fracture fixation can often experience a host of
special problems and concerns due to the location of the bones,
blood vessels, the spinal cord and other nerve tissues (and other
anatomy) as well as the significant impact any injury can have on
the patient, their rehabilitation and resulting quality of life
issues. These issues can be further impacted by a physician's
desire to remove fixation hardware after healing of the underlying
anatomy has occurred, where the design of the fixation device and
intervening scar tissue formation can potentially complicate and/or
obviate subsequent removal of the device.
SUMMARY OF THE INVENTION
[0004] In accordance with various aspects of the present invention,
devices, systems and methods are disclosed for treating odontoid
fractures of the cervical spine. In various embodiments, a flexible
tension member can be utilized in combination with a distal
rotating anchor block or "bullet" type fastener and proximal anchor
button to desirably compressively secure an odontoid fragment to
the remaining bone of the C2 cervical bone.
[0005] In one exemplary embodiment, a distal bullet fixation device
specifically adapted for treating odontoid fractures is disclosed
herein. Desirably, the bullet device can be advanced through a
passage or channel formed through the C2 body and the odontoid
fragment (desirably crossing the fracture site), and then rotated
to present an enlarged cross-section to the passage. A flexible
fixation member attached to the bullet can then be tensioned,
desirably drawing the odontoid fragment into intimate contact with
the remaining C2 body. If desired, the flexible fixation member can
be secured to a proximal anchor button, which secures and tensions
the fixation member in a desired manner, thereby applying a
compression force across the fracture site.
[0006] One aspect of the invention is directed to a cervical
fixation system including: a "bullet" device having a reduced
profile for advancement through a passage formed in the C2 body and
one or more odontoid fragments. In various embodiments, the bullet
could present a variety of surface profiles towards an odontoid
fragment, including a concave shaped face for contacting an upper
surface of the odontoid fragment. Desirably, the bullet and
associated system components will draw one or more odontoid
fragments towards the C2 vertebral body, fixating the fragment(s)
in a desired fashion and applying compressive and/or radial forces
across the fracture site.
[0007] In various embodiments, the bullet device can include
revisability features that allow the bullet to be removed from the
anatomy after healing of the injury has occurred (and/or if removal
of the implant is desired for a variety of reasons). In at least
one exemplary embodiment, the revisability feature can comprise a
flexible cord or other feature attached proximate to an opening
formed near one end of the bullet, which can be utilized to realign
the longitudinal axis of the bullet with the passage and draw the
bullet back through the passage or channel formed through the C2
body after the flexible fixation member is severed and/or otherwise
de-tensioned.
[0008] In various embodiments, the disclosed devices, systems and
components can be utilized with virtually all manner of odontoid
fractures types, including Type I, Type II (A, B and C) and Type
III. In addition, the disclosed devices can be utilized to treat
odontoid fractures involving significant fracture displacement
and/or angulation, as well as antero-inferior to postero-superior
fractures (Type 2C fractures) that are currently untreatable and/or
are treated using instrumented fusion of C1-C2.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The foregoing and other objects, aspects, features, and
advantages of embodiments will become more apparent and may be
better understood by referring to the following detailed
description of the preferred embodiments, taken in conjunction with
the accompanying drawings, wherein:
[0010] FIG. 1 depicts an exemplary spinal column;
[0011] FIG. 2 depicts an exemplary second cervical vertebrae;
[0012] FIG. 3 depicts interlinked C1 and C2 vertebrae with various
common types of odontoid fractures identified in dotted lines;
[0013] FIGS. 4A and 4B depict front and back perspective views of
one exemplary embodiment of a bullet device;
[0014] FIGS. 4C through 4H depict various plan views of the bullet
device of FIGS. 4A and 4B;
[0015] FIGS. 5A through 5C depict various views of one embodiment
of a button device;
[0016] FIGS. 6A and 6B depict a partial spinal column, depicting
one exemplary embodiment of a placement of a guide wire through a
portion of a C2 cephalad body into an odontoid fragment;
[0017] FIGS. 7A and 7B depict a partial spinal column, depicting
one exemplary embodiment of a passage formed through a portion of a
C2 cephalad body and odontoid fragment;
[0018] FIGS. 8A through 8C depict one embodiment of an insertion
tool and associated bullet and button;
[0019] FIG. 8D depicts a partial cross-sectional view of the
insertion tool and bullet of FIG. 8C;
[0020] FIG. 8E depicts a partial perspective view of the handle and
button of FIG. 8C including flexible members;
[0021] FIGS. 10A through 10F depict various views of one
alternative embodiment of a bullet;
[0022] FIGS. 11A and 11B depict views of another alternative
embodiment of a bullet;
[0023] FIGS. 12A and 12B depict views of another alternative
embodiment of a bullet;
[0024] FIGS. 13A and 13B depict views of another alternative
embodiment of a bullet;
[0025] FIGS. 14A and 14B depict views of another alternative
embodiment of a bullet;
[0026] FIGS. 15A and 15B depict views of another alternative
embodiment of a bullet;
[0027] FIGS. 16A and 16B depict views of another alternative
embodiment of a bullet;
[0028] FIGS. 17A and 17B depict views of another alternative
embodiment of a bullet;
[0029] FIGS. 18A and 18B depict views of another alternative
embodiment of a bullet;
[0030] FIGS. 19A and 19B depict views of another alternative
embodiment of a bullet;
[0031] FIG. 20A depicts a partial plan view of an odontoid fragment
and an associated bullet device;
[0032] FIG. 20B depicts one exemplary motion path of a bullet
during a bullet recovery procedure; and
[0033] FIG. 21 depicts a flowchart of exemplary surgical steps on
one embodiment of an odontoid fixation procedure.
DETAILED DESCRIPTION
[0034] Various features of the present invention include the
recognition of a need for a more effective and versatile system of
fixating and/or securing one or more odontoid bone fragments to an
underlying C2 vertebrae. In addition, various features of the
present invention include components that facilitate removal of
fixation components from treated regions once healing has completed
and/or in the event of implant failure or complications requiring
implant removal and/or retreatment. A variety of configurations,
sizes and shapes of such components and associated tools can be
utilized in diverse anatomical regions, including use in cranial
and/or spinal surgery as well as other anatomical locations. In
various medical applications, the disclosed components and related
surgical tools and techniques can desirably facilitate the
treatment of various types of bone fractures by surgeons, which can
be important to achieve the most accurate and best performance
and/or fit of implant components and well as facilitate patient
recovery.
[0035] This specification describes novel systems, devices and
methods to treat spinal fractures. Aspects of the present invention
will be described with regard to the treatment of vertebral bodies,
e.g., odontoid fractures. It should be appreciated, however, that
various aspects of the present invention may not limited in their
application to odontoid fractures. The systems and methods may be
applicable to the treatment of fractures in diverse bone types.
Embodiments will now be described with reference to the drawings,
wherein like reference numerals are used to refer to like elements
throughout. It should be understood that the figures are not
necessarily to scale.
[0036] FIG. 1 depicts an exemplary spinal column 10 of a human
being. The spinal column 10 includes a number of uniquely shaped
bones, called vertebrae 12, a sacrum 14, and a coccyx 16 (also
called the tail bone). The number of vertebrae 12 that make up the
spinal column 10 depends upon the species of animal. In a human,
there are twenty-four vertebrae, comprising seven cervical
vertebrae 18, twelve thoracic vertebrae 20, and five lumbar
vertebrae 22.
[0037] When viewed from the side, as illustrated in FIG. 1, the
spinal column 10 forms an S-shaped curve. The curve serves to
support the head and upper torso. Each vertebra 12 generally
includes a vertebral body, which extends on the anterior (i.e.,
front or chest) side of the vertebra 12. The vertebral body is
generally in the shape of an oval disk. The vertebral body includes
an exterior formed from compact cortical bone. The cortical bone
encloses an interior volume of reticulated cancellous, or spongy,
bone (also called medullary bone or trabecular bone). A "cushion,"
called an intervertebral disk, is located between the vertebral
bodies. An opening, called the vertebral foramen, is located on the
posterior (i.e., back) side of each vertebra 12. The spinal
ganglion pass through the foramen. The spinal cord passes through
the spinal canal. The vertebral arch surrounds the spinal canal.
The pedicle of the vertebral arch adjoins the vertebral body. The
spinous process extends from the posterior of the vertebral arch,
as do the left and right transverse processes.
[0038] FIG. 2 depicts an exemplary second cervical vertebrae,
referred to as "C2," which forms a pivot upon which the first
cervical vertebra (C1--the atlas--which carries the head) rotates.
A distinctive characteristic of the C2 vertebrae is the strong
odontoid process 50 ("dens"--also referred to herein as
"odontoid"), which rises perpendicularly from the upper surface of
the body.
[0039] FIG. 3 depicts interlinked C1 and C2 vertebrae with various
common types of odontoid fractures identified in dotted lines,
including Type I, Type II and Type III odontoid fractures. In
general, Type I fractures involve a small amount of bone at the tip
of the odontoid process, and these fractures are often treated with
traction and cervical collar immobilization (i.e., using
halo/Minerva fixation), while Type II fractures are most
successfully treated using fixation screws and/or plates. Type III
fractures, which often involve a patient who has sustained multiple
traumatic injuries, can be treated with traction and cervical
collar immobilization, but are often most successfully treated with
cervical fusion of the C1 and C2 levels.
[0040] A Type II odontoid fracture generally occurs at the base of
the odontoid as it attaches to the body of C2. Options for treating
type-2 odontoid fractures include halo stabilization as well as
C1-C2 fusion or internal fixation, but halo stabilization is often
poorly tolerated by patients with these fractures. Similarly, C1-C2
fusion is generally unpopular for these patients, as this type of
surgery typically eliminates at least 50% of cervical rotation. In
most current cases, therefore, anterior screw fixation with single
or dual cannulated screws is the standard internal fixation
technique--however such screw fixation often does not provide
adequate stabilization of the fracture secondary to poor fixation
in the C2 body, and also is less than optimal where the fracture
fragment(s) does not possess adequate structural stability to
accommodate screw-based fixation.
[0041] The various teachings of the present invention provide for
securement and fixation for all varieties of odontoid fractures,
including fractures involving unusually shaped fragments and/or a
plurality of bone fragments. It will be apparent that the various
components, tools and surgical techniques described herein can
provide a number of attendant advantages, including the ability to
fixate odontoid fractures not adequately addressed by conventional
treatment techniques. Moreover, the various treatments described
herein can, for various individuals, restore the load bearing
capability of the odontoid region virtually immediately after
surgery, which can greatly improve patient satisfaction and/or
outcomes measures for the surgery as compared to traditional
treatments.
[0042] In various embodiments, the disclosed devices, systems and
methods can be used as a substitute for existing screw-based
fixation techniques and implants for odontoid fracture surgery,
including various surgical techniques, tools and related implants
described herein. Various embodiments disclose a flexible tether
based compressive fixation system, wherein a first anchor (which
may comprise a relatively rigid, elongated portion or "bullet") is
introduced across a fractured odontoid region, and the flexible
tether is tensioned between the first anchor and a second anchor,
whereby the fracture region is compressed and the odontoid fracture
fragment(s) is desirably immobilized relative to the remaining C2
bone. Properly employed, the disclosed system can secure the
fractured portion(s) of the odontoid to the native remainder of the
vertebral bone structure, thereby fixating and/or "reinforcing" the
fractured portion and facilitating continued normal function of the
patient's anatomy and reduced recovery time. Moreover, the various
system components further allow for minimally-invasive removal of
the odontoid bullet and associated fixation components, in the
event of further fracture, implant failure and/or healing of the
fractured bone portion.
[0043] The present invention desirably provides minimally invasive,
flexible fixation of the odontoid fragment, which in various
embodiments may allow desirable micro-motion at the fracture point.
In various embodiments, there may be no need for routine removal of
the implant and its use should enable patients to ambulate at an
earlier stage that with traditional cervical spine surgery.
[0044] FIGS. 4A and 4B depict front and back perspective views of
one exemplary embodiment of a bullet device 100 for use in
conjunction with the various teachings provided herein. The bullet
100 includes an elongated, generally cylindrical body 110 with a
proximal end 120 and a distal end 130. The proximal end 120
presents a gradually tapered profile, with the proximal end
terminating in a generally blunt proximal tip 140. The distal end
130 similarly presents a gradually tapered profile, with the distal
end terminating in a generally blunt distal tip 150. A plurality of
fixation openings 160 and 170 are formed in the elongated body 110,
through which a flexible fixation member (not shown) can extend for
placement and tensioning of the construct. A recovery opening 180
is also formed in the elongated body near the proximal end 120. The
recovery opening 180 desirably accommodates a flexible recovery
member (not shown), which can be utilized to remove the bullet via
the surgical path through the C2 body when implant removal is
desired and/or warranted.
[0045] As best seen in FIG. 4B, the elongated body 110 also
includes a central recessed region 190 extending beyond the
fixation openings 160 and 170. While the central recessed region
190 is shown as a gently curved concave surface, it should be
understood that other shapes, including shapes having greater
curvatures and/or lesser curvatures (and/or three dimensional
curvatures, if desired), as well as flat surfaces and/or angled
surfaces, could be incorporated. Similarly, in alternative
embodiments the central recessed region 190 could comprise a convex
surface that presents to the underlying bony surface(s), and/or
various combinations of concave, convex, flat and/or angled
surfaces, if desired. FIGS. 4C through 4I depict various plan views
of the device of FIGS. 4A and 4B.
[0046] FIG. 5A depicts a perspective view of one embodiment of a
button 700 for use in securing the odontoid fragment(s) in a
desired position. The button 700 comprises a disc-shaped body 705,
with one or more button openings 710 and 720 (in this embodiment,
two holes) extending there through. Each of the button openings
desirably incorporate rounded or tapered edges 730, which reduce
the likelihood of damaging the flexible members (not shown) which
will extend therein. FIGS. 5B and 5C depict front plan and side
plans views thereof.
[0047] It should be understood that some or all of the openings in
the bullets and/or buttons described herein could be countersunk or
otherwise rounded or tapered so as to allow easier threading
passage of the flexible members and to reduce the potential for
severing and/or fatigue fracture of the flexible members under
loading conditions.
[0048] In various embodiments, a rounded button (such as the
embodiments shown herein) may have any suitable dimension (diameter
and thickness), as well as any suitable number of openings (i.e., 1
or 2 or 3 or 4 or more). For example, a rounded button embodiment
might have a diameter of about 5.5 mm and a thickness of about 1.27
mm. The centers of the apertures could be about 1.27 mm from the
center of the button and the centers of the pair of apertures could
lie substantially along an axis passing through the center of the
button. The apertures of the rounded button can have any shape,
including shapes where each aperture is desirably equidistant from
the center of the rounded body. One preferred embodiment is an
aperture, which is substantially round in plan-view. Another
embodiment could be an egg-shaped or oval aperture.
[0049] Aspects of the invention further relate to methods for
installing the bullet and associated bone fixation system
components in a human patient. Initially, at least a portion of a
cervical spine of an associated patient is exposed to reveal the
vertebral body to be repaired. Access to the vertebral body can be
accomplished from many different directions, depending upon the
targeted location within the vertebral body, the intervening
anatomy, and the desired complexity of the procedure. For example,
access can also be obtained through a pedicle (transpedicular),
outside of a pedicle (extrapedicular), along either side of the
vertebral body (posterolateral), laterally or anteriorly. In
addition, surgical approaches could be used with a closed,
minimally invasive procedure or with an open procedure.
[0050] In at least one exemplary surgical procedure, general
endotracheal anesthesia can be used and the patient may be placed
in the supine position with the patient's head secured by tongs or
some other device or mechanism to allow reduction of the facture.
The head may be secured on a radiolucent operating table with the
mouth held open with a radiolucent bite block, with single and/or
biplane fluoroscopy used throughout the operation to guide the
placement and motion of surgical tools, any desired reduction of
the fracture and/or for placement of one or more components of the
cervical fixation system. The patient's head can be positioned
under lateral fluoroscopic guidance so that the neck could be
extended to permit a trajectory for proper passage creation and/or
insertion of the device.
[0051] In one exemplary embodiment (see FIG. 21), an anterior
exposure to the cervical spine 1000 could be performed. For
example, a left or right incision, depending on the surgeon's
preference, is made longitudinally, inferior to the body of C2.
Such an incision would desirably allow optimal angulation of any
guide wires, drills and/or the bullet device, tension member(s),
recovery member(s) and associated fastening devices. If desired,
the midline antero-inferior aspect of the C2 body can be
identified, such as by cutting a gutter into the anterior body of
C3 and the C2-C3 disk to provide adequate visualization of the
antero-inferior endplate of C2.
[0052] As best shown in FIGS. 6A and 6B, a guide wire 300 is placed
through a portion of a C2 cephalad body into the odontoid 1010. If
desired, a drill guide or other similar tool could be placed on the
antero-inferior lip of C2 in the midline (or other position as
desired by the surgeon). Generally, a C-arm guide or other such
non-invasive imaging device may be used for precise placement of
the guide wire into and through the odontoid and/or the avoidance
of sensitive anatomy such as the spinal cord. For example, under
fluoroscopic control, a 1.2 mm diameter Kirshchner wire (K wire)
could be positioned on the anterior aspect of the inferior endplate
of C2. The K wire could be advanced manually or with aid of a
pneumatic drill so that the tip engages the cortex of the tip of
the dens. If desired, one or more additional guide wires may be
placed in the odontoid and/or through other anatomy in order to
allow for de-rotation or adjusting of the positon of the odontoid
fragment(s). In various instances, the second guide wire or other
surgical tools may be used to allow a surgeon to adjust alignment
of the odontoid to an anatomically desired position prior to,
during and/or after placement of the bullet and associated
structures.
[0053] At some point in the surgical procedure (or preoperatively,
if perioperative imaging has been used), a size, shape and/or
length determination could be made to determine an appropriate size
and/or shape of the bullet and/or button to desirably secure the
odontoid fragment(s) to the C2 body 1020. This selection could
include identification of the bony anatomy proximate to the exit
point of the passage out of the odontoid fragment, which might
influence the physician's choice of bullet size, concavity,
curvature and/or angulation. In various embodiments, a depth gauge
or similar device could be placed over the guide wire 300, or the
characteristics of the fixation device components may be determined
in a variety of ways (e.g., X-rays, CT scans, measuring without the
guide wire, etc.) preoperatively and/or during the surgical
procedure.
[0054] Desirably, a hole or passage can be drilled in a caudal to
cephalad direction through the C2 body and out of the tip of the
odontoid 1030, which may include the use of a cannulated drill
following the guide wire 300, creating a passage 305 (as shown in
FIGS. 7A and 7B). Real time bi-planar fluoroscopy could be used (if
desired) to monitor progress of the drill until the drill bit just
passes through the odontoid tip. In one embodiment, the hole may be
approximately 2.5 to 4.0 mm, with the hole desirably large enough
in diameter to accommodate passage of an appropriately sized and
shaped bullet. One of ordinary skill in the art will appreciate
that the disclosed diameter is exemplary in nature and any
appropriate diameter selected by a surgeon should be within the
scope of the present disclosure. Desirably, the depth of drilling
will match a length determination (of the C2 body and odontoid
fragment) from the previously described measuring step, with the
passage passing through the odontoid fragment.
[0055] Once drilling of the passage is complete, the physician can
select an insertion tool 400, which can desirably be pre-loaded
with appropriate bullet 410 at a distal end 405, a button 420 in a
handle receiver portion 415, flexible fixation members 430
extending between the bullet and button, and a flexible recovery
member 440 extending down through a lumen 460 in the insertion tool
(see FIGS. 8A through 8C). Desirably, the flexible recovery member
440 can be tensioned to draw the bullet into a corresponding
receiving portion of the distal tip, aligning the longitudinal axis
of the bullet with the insertion tool and holding these components
together in a relatively rigid fashion. In various embodiments, the
inner surface of the receiving portion can have a shape that
matches and/or compliments the outer shape of the proximal end 120
of the bullet, which desirably engages with and secures the bullet
so as to allow the bullet to be rotated while advancing and/or
withdrawing the insertion tool into and/or out of the passage (see
FIG. 8B), while in other alternative embodiments the inner surface
of the receiving portion could have a more regular or
frusto-conical shape.
[0056] In various embodiments, the bullet could have one or more
high strength flexible members attached thereto, including suture
tape (preferably a high strength tape formed of ultrahigh molecular
weight polyethylene--sold under the brand name FiberTape.RTM. by
Arthrex, Inc. of Naples, Fla.) or pull-through suture strand
(preferably a high strength suture such as #2 FiberWire.RTM. sold
by Arthrex, Inc. of Naples, Fla.), with the FiberTape or FiberWire
sutures preattached to the device when loaded onto an insertion
tool. One larger suture could comprise a flexible fixation band,
which could be weaved through the center of the device and utilized
as the main tension band between the bullet and the button or base
anchor. A second smaller suture could comprise a removal or
revision band that allows the bullet to easily be removed if
necessary during or after the surgical procedure.
[0057] In use, the physician can insert the distal end 405 of the
insertion tool and attached bullet 410 through the passage formed
in the C2 body and the odontoid fragment. As previously noted, the
relatively rigid engagement between the bullet and the insertion
tool desirably allows the bullet and attached insertion tool to be
advanced/withdrawn and rotated during advancement and/or
retraction, which desirably reduces the forces necessary to
insert/withdraw the bullet. As the bullet advances out of a distal
end of the passage in the odontoid fragment 1040, it may be
desirous to reduce and/or release the tension on the flexible
recovery member 440, which can allow the bullet to move and/or flex
relative to the tip of the insertion tool. Once the bullet 410
begins to leave the passage (or where the bullet has been fully
advanced out of the passage), the flexible fixation wires can be
tensioned to some degree, which will tend to rotate or flip the
bullet 410 within the soft tissue space so as to present an
enlarged profile to the bone passage and/or the surface of the
odontoid fragment 1050. Further tension on the flexible fixation
wires will desirably draw the bullet into intimate contact with the
odontoid fragment, and desirably some portion of the fragment
surface can desirably enter and/or engage with at least a portion
of the concave surface of the central recessed region 190 (see
FIGS. 9A and 9B), such that when the flexible fixation wires are
fully tensioned to a desired level, the bullet will induce the
fragment to engage with the C2 bone, desirably causing a
compressive loading force across the fractured bone region.
[0058] One significant advantage of the present system over prior
art systems is the ability of the present system components to
accommodate unstable bone fragments and/or fragments that are
unable to withstand the internal "hoop stresses" typically induced
by screw-based fixation systems. In prior art fixation systems, the
odontoid fragment desirably has sufficient size and structural
integrity to accommodate the threads of the fixation screw, which
"bite" into the inner bone surface and induce an outward-acting
circumferential force on the fragment (i.e., the "hoop" stresses).
In addition, prior art systems require strong threaded fixation
into the odontoid fragment, which typically requires larger threads
to be screwed into the fragment--again requiring a larger fragment
to accommodate these needs. Moreover, screw-based fixation of
odontoid fragments is contraindicated where there are fractures
into the body of C2 (which do not allow firm screw purchase) or
where oblique odontoid fractures exist that are steeply angled
anteriorly.
[0059] In contrast, the present system does not rely on the
structural integrity of the odontoid fragment and/or its ability to
withstand drilling combined with screw-based fixation to maintain
the fragment in a desired position. Rather the disclosed systems
can be use with all manner of passages, including partially formed
passages and/or "grooves" formed into an odontoid fragment, if
desired. Moreover, the present systems could be used with surgical
tunnels having non-uniform shapes and/or axes (i.e., "bent" or
curved tunnels, which could include circular and/or non-circular
cross sections).
[0060] When the flexible fixation member of the present embodiment
is tensioned, the member desirably pulls the bullet downward onto
the bone fragment, and the concave curvature of the bullet can
induce both an axial compressive force F.sub.A on the fragment
(tending to push the fragment downward into the C2 body) and a
radial compressive force F.sub.C induced by the curved surfaces
(tending to push the sides of the fragment together), which tends
to hold the fragment together rather than push it apart (see FIGS.
9A and 9B). The present system desirably provides compressive
loading to the top of the odontoid (along with radial inward forces
induce by the bullet curvature in contact with the bone), and the
tension member pulls the odontoid into the remaining vertebral
bone, thereby creating an extremely strong bond between the
fragment and the bone, and allowing immediate and/or expedited
loading of the fragment by the patient with significantly reduced
recovery times.
[0061] Moreover, depending upon the selected bullet size and amount
of curvature, a single bullet could potentially be utilized to
secure more than one odontoid fragments, or could be utilized to
treat one or more odontoid fragments of a size, shape and/or
integrity that cannot be fixated using current screw-based
techniques. For example, the curved inner surface of the button can
provide varying amounts of lateral compression to the fragment(s),
which may assist with the control and/or reduction of multi-piece
fragments of the odontoid. In addition, in embodiments where the
anchoring devices are positioned external to the bony anatomy, the
compressive anchor loading occurs primarily on the outer cortex
and/or cortical bone (which is generally considered the stronger
bone type) as compared to the relatively weaker internal cancellous
bone structures primarily relied upon by screw-based fixation
methods.
[0062] In various embodiments, the odontoid bullet could be
anchored via virtually any angle and/or configuration of tunnel
passing in and/or through C2 (including minimally-invasive
approaches and techniques and/or off-axis approaches), which allows
very secure fixation of the odontoid to C2, yet allows for
significant surgical freedom and approach selection.
[0063] FIG. 8D depicts a partial cross-sectional view of the distal
tip 405 of one embodiment of an insertion device 400, with an
associated bullet 410 loaded therein. The flexible fixation member
430 is threaded through the fixation openings 433 and 436, with the
fixation member 430 extending outward of the central recessed
region 409 and extending downward along an outer surface 415 of the
insertion device 400. A flexible recovery member 440 extends
upwards through a lumen 460 within the insertion device 400, loops
through a recovery opening 480 and extends back downward in the
lumen 460. As best seen in FIG. 8E, the flexible fixation member
430 travels along the outside surface of the insertion device 400
and passes up into grooves 480 formed in a handle 490. The fixation
member 430 passes through button openings 710 and 720 in a
securement button 700 and then passes proximate to a fixation
member knob 740 extending outward from the handle. The recovery
member 440, which extends within the lumen 460 in the insertion
device (as previously described), exits the lumen 460 through a
shaft opening 490, with the recovery member 440 extending along the
handle 490 and passing proximate to a recovery member knob 495
extending outward from the handle 490.
[0064] In various alternative embodiments, the bullet and button
could be secured or pre-threaded together by the flexible fixation
member, which could be double looped through the openings in the
bullet and button in a known manner. In other alternative
embodiments, the bullet and/or button could incorporate one-way or
locking fasteners in one or more openings.
[0065] Another significant improvement of various embodiments over
the prior art is the inclusion of one or more recovery openings
formed in the odontoid bullet which, in the event of further bone
fracture, implant failure and/or healing of the fractured bone
portion, facilitates the less-invasive and/or minimally-invasive
removal of the bullet component (and related fixation components)
from the patient. The positioning and placement of the recovery
opening, in conjunction with the attached recovery member,
desirably allows the odontoid bullet to be removed from the C2 body
via the existing surgical passage through the bone. As best shown
in FIGS. 20A and 20B, a tension force TR on the recovery member
(where the previously described fixation members have been
de-tensioned and/or severed) will tend to pull the proximal end 120
of the bullet towards the surgical passage (along path P.sub.R),
while also rotating the distal end 130 of the bullet away from the
passage (along path D.sub.R). Desirably, sufficient tension force
on the recovery member will ultimately align the bullet with the
surgical passage, thereby allowing the bullet to be drawn down the
existing passage with little or no disruption to surrounding
tissues. Once removal of the bullet is completed, the surgical
passage may be utilized for additional procedures (i.e., including
placement of a replacement implant such as a new bullet and/or a
conventional screw-based fixation, if desired) if desired, or the
passage may be filled with bone graft material or other filing
material (i.e., bone cement).
[0066] In one exemplary embodiment, the recovery member can extend
through the surgical tunnel after the implant is installed, with
some portion of the recovery member attached to a caudal portion of
the tunnel (i.e., to a caudad button or other feature), with some
amount of "slack" being desirably provided in the recovery member.
If removal of the bullet is desired, the main tension member (i.e.,
the fixation member extending through one or more of the fixation
openings) can be severed or loosened, and the recovery member
desirably tensioned, which can cause the bullet to relax or "lift
off" from the odontoid fragment to some degree and/or otherwise
permit pulling on the recovery member to realign the bullet with
the surgical tunnel, with the bullet ultimately pulled through the
tunnel for removal from the patient.
[0067] In various embodiments, the described odontoid implant
components and/or various surgical tools described herein could be
provided in a kit containing multiple sizes and/or shapes of
odontoid bullets and/or buttons for selection by the surgeon. In
various alternative embodiments, a series of different sized and/or
shaped bullets could be provided in kit form, with the surgeon
using a properly sized and/or shaped bullet as the cephalad implant
(i.e., at the upper end of the surgical "tunnel"), with larger
and/or other sized/shaped bullets used for a caudad implant (i.e.,
at the lower end of the surgical "tunnel"). Desirably, the kit may
allow the surgeon to place two or more odontoid bullets and/or
buttons in discreet locations that may require different sizes
and/or shapes.
[0068] In one exemplary embodiment, a kit containing a series of
different size bullets could be provided for a surgical procedure,
including one or more of the following size combinations:
TABLE-US-00001 BULLET WIDTH (mm) LENGTH (mm) SEE FIG. 3 .times. 8 3
8 11A and 11B 3 .times. 10 3 10 12A and 12B 3 .times. 12 3 12 13A
and 13B 4 .times. 8 4 8 14A and 14B 4 .times. 10 4 10 15A and 15B 4
.times. 12 4 12 16A and 16B 5 .times. 8 5 8 17A and 17B 5 .times.
10 5 10 18A and 18B 5 .times. 12 5 12 19A and 19B
[0069] In various embodiments, the curved inner surface of the
bullet (or other relevant features of the implant such as the
length, diameter, number and placement of fixation or recovery
holes, etc.) could include patient specific features, including
bullet surface features designed to match or approximate the
surface of the odontoid fragment, which may include use of
non-invasive imaging to create an inner surface that matches or
substantially matches the outer surface of the odontoid fragment
(including the incorporation of three-dimensional and/or spherical
bullet surface features, if desired). If desired, various
manufacturing methods, including Computer Aided Design (CAD) and
3-D printing techniques can be utilized to design and/or
manufacture a desired odontoid button using non-invasive imaging
data, such as MRI and/or CT scans.
[0070] For various medical applications in the spine or for other
bony anatomy, for example, the rounded or curved surfaces may be
configured to mimic the contour of an underlying bony surface to
which the device is attached and/or adjacent to, or the surface may
include features that can prepare the underlying bony surface
(i.e., roughened surfaces) and/or include surface features that can
osseo-integrate with the bone surface, if desired.
[0071] In at least one alternative embodiment, the various fixation
components described herein could be used in conjunction with
screw-based fixation devices for the treatment of odontoid
fractures. For example, the odontoid bullet shown in FIG. 10A could
include a central fixation opening that incorporated internally
threaded features (not shown). Such an embodiment could allow for
placement of the bullet proximate to the odontoid fragment (in a
similar manner as previously described) using a tensioned flexible
fixation member, but with the added step of allowing a fixation
screw to be inserted through the surgical passage and threaded into
the central fixation opening of the bullet, if desired.
[0072] In various alternative embodiments, the bullet and button
components could incorporate one or more bony ingrowth surfaces,
which could allow natural healing and permanent fixation of these
components to the bone. Similarly, the flexible members described
herein could comprise degradable and/or resorbable materials, if
desired.
[0073] Another particularly useful feature of the various
embodiments disclosed herein is the ability of the system to
incorporate components constructed from non-ferrous and/or
non-magnetic materials (i.e., plastics and/or ceramics). Unlike
screw-based fixation, which often requires the use of high strength
metals for the screws and/or related components, the components of
the present invention could be constructed from virtually any
materials, including plastics, ceramics and/or metals, with various
plastic components useful in virtually any environment, even where
the use of ferrous materials and/or magnetic devices is prohibited
(i.e., in high-energy electrical environments and/or near
high-strength magnets such as Magnetic Resonance Imaging machines).
If visualization of such plastic or ceramic components was desired,
such components could include radiopaque elements and/or marker
bands, as is well known in the art. In various exemplary
embodiments, the bullets and buttons described herein could
comprise titanium, stainless steel, PolyEtherEther-Ketone (PEEK) or
Poly-L Lactic Acid (PLLA).
[0074] Another major advantage of the various embodiment disclosed
herein is the ability of the odontoid bullet and button system to
accommodate various patients that are not typical surgical
candidates for odontoid screw fixation because they may have
transverse ligament disruption, anatomical abnormalities and/or
misaligned fractured segment and/or communited fractures. The
flexibility and size of the odontoid bullet and button system
allows it to be used with patients that may not be suitable
surgical candidates for odontoid screw fixation because their
anatomy interferes with the appropriate screw trajectory (e.g.,
short neck and barrel-shaped chest patients). Furthermore, the
flexibility and size of the odontoid bullet and button system
allows it to be used with patients that may not be suitable
surgical candidates for odontoid screw fixation because the
fractured odontoid and remaining C2 body are misaligned or not
horizontal (e.g., the fracture line is not adequately horizontally
aligned). Such misalignment may facilitate the use of two or more
odontoid bullet and/or button systems.
[0075] The embodiments herein describe odontoid fixation components
and tools that are relatively inexpensive and easily formed, and
are particularly robust in their applications. For example, as
described the bullet and button components are unlikely to fail in
their intended loading patterns, and the associated flexible
fixation members are highly resistant to fatigue fracture (unlike
their screw-based counterparts, which can often fracture under
repeated loading). Moreover, even where implant removal is
required, the present systems components can be easily and readily
removed with little or no additional injury to the patient.
[0076] Incorporation By Reference
[0077] The entire disclosure of each of the publications, patent
documents, and other references referred to herein is incorporated
herein by reference in its entirety for all purposes to the same
extent as if each individual source were individually denoted as
being incorporated by reference.
[0078] Equivalents
[0079] The invention may be embodied in other specific forms
without departing from the spirit or essential characteristics
thereof. The foregoing embodiments are therefore to be considered
in all respects illustrative rather than limiting on the invention
described herein. Scope of the invention is thus intended to
include all changes that come within the meaning and range of
equivalency of the descriptions provided herein.
[0080] Many of the aspects and advantages of the present invention
may be more clearly understood and appreciated by reference to the
accompanying drawings. The accompanying drawings are incorporated
herein and form a part of the specification, illustrating
embodiments of the present invention and together with the
description, disclose the principles of the invention.
[0081] Although the foregoing invention has been described in some
detail by way of illustration and example for purposes of clarity
of understanding, it will be readily apparent to those of ordinary
skill in the art in light of the teachings of this invention that
certain changes and modifications may be made thereto without
departing from the spirit or scope of the disclosure herein. What
have been described above are examples of the present invention. It
is, of course, not possible to describe every conceivable
combination of components or methodologies for purposes of
describing the present invention, but one of ordinary skill in the
art will recognize that many further combinations and permutations
of the present invention are possible. Accordingly, the present
invention is intended to embrace all such alterations,
modifications and variations that fall within the spirit and scope
of the appended claims.
* * * * *