U.S. patent application number 14/541281 was filed with the patent office on 2015-03-12 for bone screw retaining and removal system.
This patent application is currently assigned to SPECTRUM SPINE IP HOLDINGS, LLC. The applicant listed for this patent is James C. Robinson. Invention is credited to James C. Robinson.
Application Number | 20150073427 14/541281 |
Document ID | / |
Family ID | 40568070 |
Filed Date | 2015-03-12 |
United States Patent
Application |
20150073427 |
Kind Code |
A1 |
Robinson; James C. |
March 12, 2015 |
BONE SCREW RETAINING AND REMOVAL SYSTEM
Abstract
A bone screw retention system is provided for a plate which
defines a plurality of transversely extending bores that are
configured to receive a hone screw for engaging the plate to the
cervical spine. One or more retention members, having an
elliptical, arcuate, straight, or other shape, can be positioned
therein a cavity of the plate such that portions of the retention
member(s) extend into a portion of an upper region of each bore to
retain a bone screw therein. A bone screw removal device is
provided, having at least one tongue member configured to
selectively displace the one or more retention members to allow the
bone screw to be removed from the respective bore.
Inventors: |
Robinson; James C.;
(Atlanta, GA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Robinson; James C. |
Atlanta |
GA |
US |
|
|
Assignee: |
SPECTRUM SPINE IP HOLDINGS,
LLC
Atlanta
GA
|
Family ID: |
40568070 |
Appl. No.: |
14/541281 |
Filed: |
November 14, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12738217 |
Jul 25, 2011 |
|
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14541281 |
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Current U.S.
Class: |
606/104 |
Current CPC
Class: |
A61B 17/8875 20130101;
A61B 17/8042 20130101; A61B 17/8861 20130101; A61B 2560/0443
20130101; A61B 17/8872 20130101; A61B 17/8052 20130101; A61B 17/92
20130101 |
Class at
Publication: |
606/104 |
International
Class: |
A61B 17/88 20060101
A61B017/88; A61B 17/80 20060101 A61B017/80 |
Claims
1-25. (canceled)
26. A bone screw removal device for removing a bone screw from a
plate, wherein the bone screw is retained in place by at least one
elastically deformable retention member covering at least a portion
of a head of the bone screw, the bone screw removal device
comprising: an inner tubular sleeve having an outer diameter and
defining a conduit extending from an upper end to a lower end of
the inner sleeve, wherein the inner sleeve has at least one
resilient tongue member comprising at least one protrusion
extending outwardly from the lower end of the inner sleeve; and an
outer tubular sleeve having an inner diameter and defining at least
one notch in a lower end of the outer sleeve for complementarily
receiving the at least one protrusion of the inner sleeve; wherein
the inner diameter of the outer sleeve is greater than the outer
diameter of the inner sleeve such that the inner sleeve is
insertable into the outer sleeve, wherein when the inner sleeve is
inserted into the outer sleeve, the at least one tongue member is
movable about and between a first compressed position, in which the
at least one protrusion of the at least one tongue member is
resiliently biased inwardly toward a longitudinal axis of the
conduit of the inner sleeve, and a second relaxed position, in
which at least a portion of the at least one protrusion of the at
least one tongue member of the inner sleeve is complementarity
received therein the at least one notch of the outer sleeve, and
wherein in the second relaxed position, at least a portion of the
at least one protrusion engages a portion of the retention member
and urges the retention member away from the head of the bone
screw.
27. The bone screw removal device of claim 26, wherein in the
second relaxed position, the at least one protrusion of the at
least one tongue member engages a portion of an outer edge of the
at least one retention member.
28. The bone screw removal device of claim 26, wherein in the
second relaxed position, the at least one protrusion of the at
least one tongue member engages an inner edge the at least one
retention member.
29. The bone screw removal device of claim 26, wherein the at least
one resilient tongue member comprises a pair of resilient tongue
members.
30. The bone screw removal device of claim 26, wherein the at least
one resilient tongue members comprises a plurality of resilient
tongue members.
31. The bone screw removal device of claim 30, wherein the at least
one retention member comprises a plurality of retention members and
wherein the number of resilient tongue members is equal to the
number of retention members.
32. The bone screw removal device of claim 26, wherein the at least
one resilient tongue member has a spring constant greater than a
spring constant of the at least one retaining member.
33. The bone screw removal device of claim 26, further comprising a
removal tool, wherein a portion of a distal end of the removal tool
is configured to operatively engage the head of the bone screw.
34. The bone screw removal device of claim 26, further comprising a
removal tool, wherein a portion of a distal end of the removal tool
is configured to engage at least a portion of the at least one
protrusion of the at least one resilient tongue members, thereby
urging the protrusion outwardly away from the longitudinal axis of
the conduit.
35. The bone screw removal device of claim 26, wherein the at least
one protrusion of the at least one resilient tongue member is
configured to be in opposition to the at least one retention
member.
36. The bone screw removal device of claim 26, wherein the diameter
of the conduit of the inner sleeve member is greater than the
diameter of the head of the bone screw.
37. The bone screw removal device of claim 26, wherein, in the
second relaxed position, the at least one protrusion of the at
least one tongue member engages portions of the at least one
retention member thereby medially biasing portions of the at least
one retention member away from the longitudinal axis of the
conduit.
38. The bone screw removal device of claim 26, wherein, in the
second relaxed position, an outer surface of the at least one
protrusion of the at least one tongue member is substantially
co-planar with an exterior surface of the outer sleeve proximate
the at least one notch.
38. The bone screw removal device of claim 26, wherein at least one
longitudinal guide slot is defined in a portion of a body of the
inner sleeve, wherein the at least one longitudinal guide slot is
substantially parallel to the longitudinal axis of the conduit, and
wherein the at least one longitudinal guide slot extends
longitudinally for a predetermined length along the body of the
inner sleeve.
39. The bone screw removal device of claim 38, wherein the at least
one longitudinal guide slot comprises a plurality of longitudinal
guide slots.
39. The bone screw removal device of claim 38, wherein the outer
sleeve comprises at least one longitudinal projection that extends
inwardly from an inner wall of the outer sleeve, wherein the length
of the at least one projection is less than the length of the at
least one longitudinal guide slot, and wherein the at least one
projection is configured to be received therein the at least one
guide slot of the inner sleeve.
40. A method of removing a bone screw from a plate, wherein the
bone screw is retained in place by at least one elastically
deformable retention member covering at least a portion of a head
of the bone screw, the method comprising: providing a bone screw
removal device comprising: an inner tubular sleeve having an outer
diameter and defining a conduit extending from an upper end to a
lower end of the inner sleeve, wherein the inner sleeve has at
least one resilient tongue member comprising at least one
protrusion extending outwardly from the lower end of the inner
sleeve; and an outer tubular sleeve having an inner diameter and
defining at least one notch in a lower end of the outer sleeve for
complementarily receiving the at least one protrusion of the inner
sleeve; wherein the inner diameter of the outer sleeve is greater
than the outer diameter of the inner sleeve such that the inner
sleeve is insertable into the outer sleeve, wherein when the inner
sleeve is inserted into the outer sleeve, the at least one tongue
member is movable about and between a first compressed position, in
which the at least one protrusion of the at least one tongue member
is resiliently biased inwardly toward a longitudinal axis of the
conduit of the inner sleeve, and a second relaxed position, in
which the at least one protrusion of the at least one tongue member
of the inner sleeve is complementarity received therein the at
least one notch of the outer sleeve; positioning the lower end of
the outer sleeve on a shoulder of the bone screw such that the at
least one notch is positioned over a portion of the retention
member; moving the inner sleeve so that the at least one tongue
member is biased from the first compressed position to the second
relaxed position, wherein in the second relaxed position, at least
a portion of the at least one protrusion engages a portion of the
retention member and urges the retention member away from the head
of the bone screw; inserting a removal tool through the conduit of
the inner sleeve to operatively engage the head of the bone screw;
and removing the bone screw.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/980,356, filed on Oct. 16, 2007, and also claims
the benefit of U.S. Provisional Application No. 61/029,771 filed on
Feb. 19, 2008, both of which applications are herein incorporated
by reference in their entirety.
FIELD OF THE INVENTION
[0002] The present invention relates generally to surgical
procedures, most particularly for use in fixation of the cervical
spine. More particularly, the invention pertains to a bone screw
retaining system for use in a plating system for use in a system
for anteriorly fixating the cervical spine and a removal system for
use in removing screws from the plate system.
BACKGROUND OF THE INVENTION
[0003] As with any bony structure, the spine is subject to various
pathologies that compromise its load bearing and support
capabilities. The spine is subject to degenerative diseases, the
effects of tumors and, of course, fractures and dislocations
attributable to physical trauma. In the past, spinal surgeons have
tackled the thorny problems associated with addressing and
correcting these pathologies using a wide variety of
instrumentation and a broad range of surgical techniques. For
example, in spinal surgeries, the fusion of two or more vertebral
bodies is required to secure a portion of the spinal column in a
desired position. Alternatively, the use of elongated rigid plates
has been helpful in the stabilization and fixation of the lower
spine, most particularly the thoracic and lumbar spine.
[0004] The cervical spine can be approached either anteriorly or
posteriorly, depending upon the spinal disorder or pathology to be
treated. Many of the well known surgical exposure and fusion
techniques of the cervical spine are described in Spinal
Instrumentation, edited by Drs. Howard An and Jerome Cotler. This
text also describes instrumentation that has been developed in
recent years for application to the cervical spine, most frequently
from an anterior approach.
[0005] The anterior approach to achieving fusion of the cervical
spine has become the most popular approach. During the early years
of cervical spine fusion, the fusions were performed without
internal instrumentation, relying instead upon external corrective
measures such as prolonged recumbent traction, the use of halo
devices or minerva casts, or other external stabilization. However,
with the advent of the elongated plate customized for use in the
cervical spine, plating systems have become the desired internal
stabilization device when performing stabilization operations.
[0006] It has been found that many plate designs allow for a
uni-corticaly or bi-corticaly intrinsically stable implant. It has
also been found that fixation plates can be useful in stabilizing
the upper or lower cervical spine in traumatic, degenerative,
tumorous or infectious processes. Moreover, these plates provide
the additional benefit of allowing simultaneous neural
decompression with immediate stability.
[0007] During the many years of development of cervical plating
systems, particularly for the anterior approach, various needs for
such a system have been recognized. For instance, the plate must
provide strong mechanical fixation that can control movement of
each vertebral motion segment in six degrees of freedom. The plate
must also be able to withstand axial loading in continuity with
each of the three columns of the spine. The plating system must be
able to maintain stress levels below the endurance limits of the
material, while at the same time exceeding the strength of the
anatomic structures or vertebrae to which the plating system is
engaged.
[0008] Further plating systems also typically require the thickness
of the plate to be small to lower its prominence, particularly in
the smaller spaces of the cervical spine. Additionally, the screws
used to connect the plate to the vertebrae must not loosen over
time or back out from the plate. This requirement, that the bone
screws do not loosen over time or back out from the plate, tends to
complicate implantation of known plating systems. Such bone screw
retention systems generally ensure that the bone screws placed into
the vertebrae through the plating system do not back out
voluntarily from the plate, but typically do not adequately permit
the removal of an associated bone screw when desired by the
surgeon.
[0009] On the other hand, while the plate must satisfy certain
mechanical requirements, it must also satisfy certain anatomic and
surgical considerations. For example, the cervical plating system
must minimize the intrusion into the patient and reduce the trauma
to the surrounding soft tissue. It is known that complications
associated with any spinal procedure, and most particularly within
the tight confines of cervical procedures, can be very devastating,
such as injury to the brain stem, spinal cord or vertebral
arteries. It has also been found that optimal plating systems
permit the placement of more than one screw in each of the
instrumented vertebrae.
[0010] More specifically, it is known that bone screws can be
supported in a spinal plate in either a rigid or semi-rigid
fashion. In a rigid fashion, the bone screws are not permitted any
micro-motion or angular movement relative to the plate. In the case
of a semi-rigid fixation, the bone screw can move somewhat relative
to the plate during the healing process of the spine. It has been
suggested that semi-rigid fixation is preferable for the treatment
of degenerative diseases of the spine. In cases where a graft is
implanted to replace the diseased vertebral body or disk, the
presence of a screw capable of some rotation ensures continual
loading of the graft. This continual loading avoids stress
shielding of the graft, which in turn increases the rate of fusion
and incorporation of the graft into the spine.
[0011] Similarly, rigid screw fixation is believed to be preferable
in the treatment of tumors or trauma to the spine, particularly in
the cervical region. It is believed that tumor and trauma
conditions are better treated in this way because the rigid
placement of the bone screws preserves the neuro-vascular space and
provides for immediate stabilization. It can certainly be
appreciated in the case of a burst fracture or large tumorous
destruction of a vertebra that immediate stabilization and
preservation of the vertebral alignment and spacing is essential.
On the other hand, the semi-rigid fixation is preferable for
degenerative diseases because this type of fixation allows for a
dynamic construct. In degenerative conditions, a bone graft is
universally utilized to maintain either the disc space and/or the
vertebral body itself. In most cases, the graft will settle or be
at least partially resorbed into the adjacent bone. A dynamic
construct, such as that provided by semi-rigid bone screw fixation,
will compensate for this phenomenon.
[0012] Furthermore, known plating systems often do not permit
sufficient angular freedom for bone screws relative to the plate.
Generally, known plating systems have defined bores through which
bone screws are placed at a predefined angle. Therefore, the
operating surgeon often does not have freedom to insert the bone
screws into the vertebrae as to best fit the anatomy of the
individual patient. While some known systems do permit bone screw
angulation, they typically are not adapted to be used with an
easy-to-use bone screw retaining mechanism.
[0013] It remains desirable in the art to provide a bone screw
retaining system and a bone screw removal device for use with a
plating system that addresses the limitations associated with known
systems, including but not limited to those limitations discussed
above.
SUMMARY OF THE INVENTION
[0014] In accordance with the purposes of this invention, as
embodied and broadly described herein, this invention, in one
aspect, relates to a bone screw retention system that includes an
implant having a plate, which defines a plurality of transversely
extending bores that are configured to receive a bone screw for
engaging the plate to the cervical spine. One or more retention
members, having an elliptical, oval, rectangular, square, or other
shape, can be positioned therein a cavity of the plate such that
portions of the retention member(s) extend into a portion of an
upper region of each bore to retain a bone screw therein.
[0015] In another aspect, a bone screw removal device is provided,
having at least one tongue member configured to selectively
displace the one or more retention members to allow the bone screw
to be removed from the respective bore. In one aspect, the bone
screw removal device includes an outer sleeve having at least one
notch extending from a lower surface of the outer sleeve, and an
inner sleeve having at least one tongue member that has a
protrusion extending from a lower portion of the tongue member. In
a further aspect, the inner sleeve is configured to be positioned
within the outer sleeve with the tongue member and protrusion of
the inner sleeve longitudinally aligned with the notch of the outer
sleeve.
[0016] In yet another aspect, a method is provided for removing a
bone screw from a bone screw retention system utilizing exemplary
bone screw removal devices as described herein.
[0017] Additional advantages of the invention will be set forth in
part in the description which follows, and in part will be obvious
from the description, or may be learned by practice of the
invention. The advantages of the invention will be realized and
attained by means of the elements and combinations particularly
pointed out in the appended claims. It is to be understood that
both the foregoing general description and the following detailed
description are exemplary and explanatory only and are not
restrictive of the invention, as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate several
embodiments of the invention and together with the description,
serve to explain the principles of the invention.
[0019] FIG. 1A is a top plan view of an exemplary bone screw
retention system comprising a plate having a plurality of bores
therein and a plurality of bone screws seated therein the
bores.
[0020] FIG. 1B is a perspective view of the bone screw retention
system of FIG. 1A, showing a plurality of bone screws seated
therein the bores of the plate and positioned at desired angles
relative to the plate.
[0021] FIG. 2A is a top plan view of the exemplary bone screw
retention system of FIG. 1A having a plurality of elliptical
ring-shaped retention members.
[0022] FIG. 2B is a partial top plan view of an elliptical
ring-shaped retention member of FIG. 2A in a first relaxed
position, in which portions of the retention member extend over a
portion of the upper region of a bore of the plate.
[0023] FIG. 2C is a partial side cross-sectional view, taken along
line A-A of FIG. 2B, of a bone screw positioned therein a bore of
the plate of the bone screw retention system and retained therein
by an elliptical ring-shaped retention member in the first relaxed
position.
[0024] FIG. 2D is a partial top plan view of an elliptical
ring-shaped retention member of FIG. 2A in a second open position
allowing the bone screw to be removed from the bore.
[0025] FIG. 2E is a partial side cross-sectional view, taken along
line A-A of FIG. 2D, of a bone screw positioned therein a bore of
the plate of the bone screw retention system and an elliptical
ring-shaped member in the second open position allowing the bone
screw to be removed from the bore.
[0026] FIG. 3A is a top plan view of the exemplary bone screw
retention system of FIG. 1A having a respective rectangular
retention member positioned therein each of the bores of the
plate.
[0027] FIG. 3B is a partial top plan view of a rectangular
retention member of FIG. 3A in a first relaxed position in which
two sides of the rectangular retention member extend over a portion
of the upper region of a bore of the plate.
[0028] FIG. 3C is a partial top plan view of the rectangular
retention member of FIG. 3B in a second open position, allowing the
bone screw to be removed from the bore.
[0029] FIG. 4A is a top plan view of the exemplary bone screw
retention system of FIG. 1A having a respective rectangular dual
retention member positioned between a pair of opposing bores of the
plate.
[0030] FIG. 4B is a partial top plan view of a rectangular dual
retention member of FIG. 4A in a first relaxed position in which
one side of the rectangular dual retention member extends over a
portion of the upper region of a first bore of the plate, and an
opposing side extends over a portion of the upper region of a
second bore of the plate.
[0031] FIG. 4C is a partial top plan view of the rectangular dual
retention member of FIG. 4B in a second open position, allowing the
first and second bone screws to be removed from the bore.
[0032] FIG. 5A is a perspective view of an inner sleeve of a bone
screw removal device.
[0033] FIGS. 5B are perspective views of a bone screw removal
device showing, from left to right, the inner sleeve of FIG. 5A
positioned within an outer sleeve, the inner sleeve in a first
raised position with a tongue member of the inner sleeve retained
within the outer sleeve; and the inner sleeve in a second, lowered
position with a tongue member protrusion of the inner sleeve
extending into a notch of the outer sleeve.
[0034] FIGS. 6 are front elevational views of, from left to right,
the inner sleeve of the bone screw removal device of FIG. 5A; the
inner sleeve positioned within the outer sleeve in the first,
raised position; and the inner sleeve in the second, lowered
position with the tongue member of the inner sleeve extending into
the notch of the outer sleeve.
[0035] FIGS. 7A are front cross-sectional views of the bone screw
removal device showing the inner sleeve in the first, raised
position (shown on the left) and the second, lowered position
(shown on the right).
[0036] FIGS. 7B are side cross-sectional views of the bone screw
removal device showing the inner sleeve in the first, raised
position (shown on the left) and the second, lowered position
(shown on the right).
[0037] FIGS. 7C are side elevational views of, from left to right,
the inner sleeve of the bone screw removal device of FIG. 5A,
showing the guide slot formed therein the side of the inner sleeve;
the inner sleeve positioned within the outer sleeve in the first,
raised position; and the inner sleeve in the second, lowered
position with the tongue member of the inner sleeve extending into
the notch of the outer sleeve.
[0038] FIG. 8A is a side cross-sectional view of a bone screw
removal device showing an inner sleeve having a pair of opposing
tongue members, the inner sleeve positioned within an outer sleeve
in a first, raised position.
[0039] FIG. 8B is a side cross-sectional view of the bone screw
removal device of FIG. 8A showing the inner sleeve positioned
within the outer sleeve in a second, lowered position.
[0040] FIGS. 8C are side elevation views of, from left to right,
the inner sleeve of the bone screw removal device of FIG. 8A
showing the pair of opposing tongue members and a guide slot formed
therein the side of the inner sleeve; the inner sleeve positioned
within the outer sleeve in the first, raised position; and the
inner sleeve in the second, lowered position with tongue member
protrusions of the inner sleeve extending into respective notches
of the outer sleeve.
[0041] FIGS. 9 illustrate exemplary downward movement of an inner
sleeve within an outer sleeve, the tongue member protrusion of the
inner sleeve extending therethrough the notch of the outer sleeve
and pushing out a retention member as the inner sleeve is lowered
from a first raised position (shown on the left), through an
intermediate position (middle) to a second lowered position (shown
on the right).
[0042] FIGS. 10 illustrate exemplary downward movement of an inner
sleeve having a pair of opposing tongue members, the tongue member
protrusions extending therethrough a pair of opposing notches of
the outer sleeve and pushing out retention members as the inner
sleeve is lowered from a first raised position (shown on the left),
through an intermediate position (middle), to a second lowered
position (shown on the right).
[0043] FIGS. 11 illustrate exemplary downward movement of an inner
sleeve within an outer sleeve, the tongue member protrusion of the
inner sleeve extending therethrough the notch of the outer sleeve
and pushing out a retention member, and the removal of a bone screw
with a removal tool.
[0044] FIGS. 12 are side cross-sectional view of a bone screw
removal device being used to remove a bone screw retained by a
rectangular retention member.
[0045] FIGS. 13 illustrate exemplary use of a removal tool to push
out at least one tongue member, thereby pushing out at least one
retention member.
[0046] FIG. 14A is a perspective view of a main sleeve of an
exemplary bone screw removal device.
[0047] FIG. 14B is a perspective view of an exemplary bone screw
removal device, showing a removal sleeve positioned around the main
sleeve of FIG. 14A.
[0048] FIG. 14C is a front view of the exemplary bone screw removal
device of FIG. 14B.
[0049] FIG. 14D is a side view of the exemplary bone screw removal
device of FIG. 14B, showing a tongue member of the removal sleeve
in a first, resting position.
[0050] FIG. 14E is a side view of the exemplary bone screw removal
device of FIG. 14B, showing the tongue member in a second, in-use
position.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0051] The present invention may be understood more readily by
reference to the following detailed description of various
embodiments of the invention, examples, figures, and their previous
and following description.
[0052] Before the present system, devices, and/or methods are
disclosed and described, it is to be understood that this invention
is not limited to the specific systems, devices, and/or methods
disclosed unless otherwise specified, as such can, of course, vary.
It is also to be understood that the terminology used herein is for
the purpose of describing particular aspects only and is not
intended to be limiting.
[0053] As used herein, the singular forms "a," "an" and "the"
include plural referents unless the context clearly dictates
otherwise. Thus, for example, reference to a "screw" includes
aspects having two or more screws unless the context clearly
indicates otherwise.
[0054] Ranges may be expressed herein as from "about" one
particular value, and/or to "about" another particular value. When
such a range is expressed, another embodiment includes from the one
particular value and/or to the other particular value. Similarly,
when values are expressed as approximations, by use of the
antecedent "about," it will be understood that the particular value
forms another embodiment. It will be further understood that the
endpoints of each of the ranges are significant both in relation to
the other endpoint, and independently of the other endpoint.
[0055] In this specification and in the claims which follow,
reference will be made to a number of terms which shall be defined
to have the following meanings:
[0056] As used herein, the terms "optional" or "optionally" mean
that the subsequently described event or circumstance may or may
not occur, and that the description includes instances where said
event or circumstance occurs and instances where it does not.
[0057] Reference will now be made in detail to various embodiments
of the present invention, examples of which are illustrated in the
accompanying drawings. Wherever possible, the same reference
numbers are used throughout the drawings to refer to the same or
like parts.
[0058] In one embodiment, and referring to FIGS. 1A and 1B, a plate
system can comprise an implant 150, particularly for the spinal
column, that can have a joining member, such as a plate 152, that
defines a plurality of openings or bores 154, and bone screws 160
capable of being accommodated in the bores. In a further
embodiment, at least one retention member is provided and is
configured for releasably securing the bone screws therein the
bores. The bone screw removal device, in one aspect, provides for
the selective removal of the bone screw or screws from the plate at
the physician's desire.
[0059] In one aspect, the plate 152 defines a plurality of
transversely extending bores 154 that are countersunk at a
predetermined distance. In one exemplary aspect, a head of a bone
screw can be configured to be posteriorly displaceable through a
bore of the plate from an anterior surface 152a to a posterior
surface 152b of the plate and retained within a portion of the bore
between the anterior and posterior surfaces. In one aspect, the
plate 152 can have a generally elongated form whose outline
generally departs from rectangular due to the presences of partial
lobes or lateral projections at the corners and at the center sides
of the plate, as can be seen in FIG. 1A. Each partial lobe has a
rounded outline and, in an exemplary aspect, can define a
respective bore. It is, of course, contemplated that other shapes
of the plate can be employed.
[0060] As noted above, the plate 152 defines a plurality of bores
154 that extend substantially transverse therethrough the plate
between the anterior and posterior surfaces 152a, 152b of the plate
and that are configured for operable receipt of the bone screw(s)
160. In one aspect, the bores extend along a longitudinal axis from
the anterior surface to the bottom, bone-contacting, posterior
surface 152b of the plate. In one aspect, each bore has an upper
region with a first diameter and a lower region that includes a
seat 156 for the bone screw and a posteriorly extending tubular
shaft 158 that extends to an opening on the posterior surface of
the plate, as can be seen in FIG. 2C, for example. In one aspect,
the seat of the bore can have at least a partial spherical shape.
In another aspect, the plate comprises a plurality of pair opposing
bores.
[0061] In a further aspect, such as illustrated in FIG. 2C, the
bone screw 160 has a head 162 with a maximum diameter that is
smaller than the first diameter of the upper region of the bore,
which thereby allows the screw head to pass through that region of
the bore. In one example, the bone screw can be a conventional
self-tapping bone screw. It is, of course, contemplated that
conventional non self-tapping bone screws can be used with the
system of the present invention. Further, it is contemplated that
conventional bone screws with at least partially rotatable heads
can be used if a semi-rigid fixation procedure is desired.
[0062] According to various aspects, the head 162 of each bone
screw 160 can comprise a complementary tapered section that extends
from an upwardly facing shoulder surface 164, which is formed by a
portion of the head of the bone screw, and tapers toward a threaded
shank portion 166 of the bone screw. A portion of the bone screw
above the upwardly facing shoulder surface 164 of the bone screw is
conventionally configured for operative engagement with a driving
tool 150 and has a reduced diameter relative to the diameter of the
shoulder of the head of the bone screw.
[0063] In one aspect, the tubular shaft 158 of the bore is
configured for complementary receipt of the shank of the bone screw
such that the bone screw can be fixed at a predetermined angle with
respect to the plate. Alternatively, the bone screw can be fixed at
an operator selected angle, i.e., be angularly displaceable. In one
aspect, the tapered section of the bone screw can be configured for
complementary rotatable contact with an exemplary spherically
shaped seat of the bore. It is contemplated that the tapered
section of the bone screw can be substantially linear or,
optionally, substantially hemispherical. Further, the shank of the
bone screw can be threaded in any well known fashion and may
include an axial groove to enable the bone screw to be self-boring
and self-tapping.
[0064] In another aspect, the shaft 158 of the bore can have an
operative diameter that is greater than the diameter of the shank
166 of the bone screw intermediate the head of the bone screw and
its distal end. As a result, the bone screw 160 is angularly
displaceable within the shaft of the bore between the seat and the
posterior surface opening. The bone screw can thus be tilted within
the shaft of the bore relative to the longitudinal axis of the bore
to facilitate positioning the bone screw at a desired location in
the bone by advancing the threaded shank portion of the bone screw
within the bone at an angle relative to the posterior surface 152b
of the plate. In one aspect, the bone screw 160 can be angularly
displaced relative to the longitudinal axis of the bore up to an
angle of about 20 degrees. Thus, the physician or surgeon has, at
his disposal, the freedom to orient the bone screw angularly with
respect to the joining member or plate, which allows him to
optimize the anchorage. In one aspect, the bone screw(s) can be
rotatably mounted therein the underlying bone tissue using a
conventional screw driver, a drive socket, and the like.
[0065] According to various embodiments, a retaining system is
provided that is configured to secure a bone screw therein a
respective bore. In one aspect, the retaining system comprises at
least one elastically deformable retention member. In another
aspect, the retention member can have an edge portion. In this
aspect, at least a portion of the at least one retention member can
be positioned therein each at least one cavity of the plate such
that portions of the at least one retention member extend into an
upper region of each of the bores. In a further aspect, the at
least one retention member can be configured to mount therein the
at least one cavity and can be configured to be movable between a
first relaxed position and a second compressed position. In a
further aspect, the at least one elastically deformable retention
member can comprise a plurality of elastically deformable retention
members.
[0066] In the first relaxed position, a portion of the edge portion
of the at least one retention member extends inwardly substantially
transverse to and toward the longitudinal axis of the respective
bore and into the upper region of the bore. As one will appreciate,
an effective inner diameter of the upper region of the bore is
decreased in the first relaxed position. In another aspect, a
portion of the edge portion of the at least one retention member
extends over portions of the upper region of a plurality of bores
of the plate in the first relaxed position.
[0067] In the second compressed position, portions of the at least
one retention member are medially biased outwardly away from the
longitudinal axis of the bore towards an outer wall of the upper
region of the bore, which increases the effective inner diameter of
the upper region of the bore. Thus, it is contemplated that the
illustrate embodiments provides a means for engaging portions of
the edge portion of the at least one retention member thereby
medially biasing portions of the at least one retention member away
from the longitudinal axis of the bore towards an outer wall of the
upper region of the bore increasing the effective inner diameter of
the upper region of the bore.
[0068] In one aspect, the retention system can comprise at least
one retention member having an outer edge. In another aspect, the
at least one retention member can be a resilient, continuous,
ring-shaped member in the first relaxed position. As can be
appreciated, the at least one resilient retention member can have
spring constant K.sub.R. As also can be appreciated, it is
contemplated that the at least one continuous ring-shaped member
can be circular, oval, elliptical, square, rectangular, or any
other continuous geometric shape.
[0069] In one embodiment, a first retention mechanism 270 is
provided that comprises a ring-shaped retention member 272, such as
illustrated in FIGS. 2A-2E. The ring-shaped retention member, in
one aspect, is substantially elliptical in its relaxed position,
such as shown in the top plan view of FIG. 2B. The first retention
mechanism 270, in one aspect, comprises a cavity 276 formed therein
the plate 152, which is configured for receiving the ring-shaped
retention member 272. The cavity can be substantially planar and
substantially circular in the plane (illustrated in FIG. 2B) and
can define a plane that is substantially parallel to the anterior
surface 152a of the plate. The cavity can be formed to extend
inwardly into the plate from an upper portion of the bore 154,
above the seat 156 of the bore, such as shown in FIG. 2C. Thus,
when a retention member is inserted therein the cavity, and a bone
screw 160 is operatively placed therein the bore, the retention
member is positioned proximate, but above the upwardly facing
shoulder 164 of the bone screw.
[0070] When a bone screw 160 is positioned therein the bore 154,
portions of the retention member 272 will extend across portions of
the shoulder 164 of the bone screw, thereby preventing the bone
screw from unseating or backing out of the bore. It is contemplated
that the ring-shaped retention member will be of a selected shape
such that it will remain in this relaxed, retaining position absent
any shear or lateral forces being applied to it. To access the bore
(i.e., to insert or remove a bone screw), a physician can use a
driver/removal tool in combination with a bone screw removal device
(as described further herein below) to flex the retention member
272 into a more rounded, open position. For example, as shown in
FIGS. 2B and 2D, the portions of the ring-shaped retention member
that extend across the shoulder 164 of the bone screw can be flexed
or forced outwardly toward the cavity 276 until they no longer
extend across the shoulder of the bone screw. One skilled in the
art will appreciate that, when the retention member is biased into
the open position (FIGS. 2D and 2E), the bone screw can be removed.
In a further aspect, it is contemplated that means can be provided
to prevent the ring-shaped retention member from rotating within
the cavity, particularly when it is being flexed to access the bone
screw.
[0071] In another embodiment, a second retention mechanism 570 is
provided that comprises a substantially rectangular retention
member 572 having, in a first relaxed position, four substantially
straight sides, such as illustrated in FIGS. 3A-3C. At least one
side of the rectangular retention mechanism, in its relaxed
(unstressed) positions, can extend across a portion of the shoulder
of a respective bone screw. In a further aspect, two opposing sides
of the rectangular retention mechanism can extend across portions
of the shoulder of the respective bone screw, such as shown in FIG.
3B. In order to access the bone screw, the opposing sides can be
flexed or stressed outwardly into an arcuate shape until the bone
screw is unobstructed, such as shown in FIG. 3C. It is contemplated
that the other two opposing sides will be drawn toward each other
and can remain substantially straight as the retaining sides are
bowed outwardly. A cavity 576 can be formed therein the plate to
receive and retain the rectangular retention member. The cavity can
be substantially planar in a plane that is substantially parallel
to the anterior surface of the plate. The cavity can be formed to
extend inwardly into the plate from an upper portion of the bore,
above the seat of the bore. Such a cavity can be similar to that
shown in FIG. 2C, although it can be sized and shaped (i.e.,
rectangular, circular, etc.) to receive and accommodate the
rectangular retention member in its first relaxed position and
second stressed or flexed position.
[0072] According to another aspect, a third retention mechanism 670
is provided that comprises a rectangular dual retention member 672,
such as illustrated in FIGS. 4A-4C. In one aspect, the dual
retention member is configured to be positioned between opposing
bores. Opposing sides of the retention member are configured to
extend across portions of the opposing bores. For example, as
illustrated in FIG. 4B, in one aspect, a first side extends across
a portion of a first bore, and a second, opposing side extends
across a portion of a second bore. Thus, it is contemplated that a
single rectangular dual retention member 672 can be used to secure
at least two bone screws therein respective bores. In their first,
relaxed position, the first and second sides of the retention
member extend across the bores to retain the bone screws therein.
In order to access the bone screw, the first and second sides can
be flexed or stressed inwardly into an arcuate shape until the
respective bone screws are unobstructed, such as shown in FIG. 4C.
As the first and second sides are flexed inwardly, it is
contemplated that the other sides will be drawn toward each other
and can remain substantially straight. A cavity 676, such as that
shown in FIGS. 4B and 4C can be formed therein the plate to receive
and retain the rectangular dual retention member 672. As may be
appreciated, the cavity can be sized and shaped to receive and
retain the retention member. Additionally, it is contemplated that
the at least one elastically deformable retention member can be
positioned therein each at least one cavity such that a center of
the at least one retention member is substantially stationary
geometrically when the at least one retention member is in the
first relaxed position and the second compressed position.
[0073] According to various aspects of the present invention, a
bone screw removal device is provided for removing bone screw(s)
from a bone screw retention system, such as the exemplary bone
screw retention systems described herein. If desired and as may be
appreciated, the bone screw removal device can also be used to
insert a bone screw into a bone screw retention system.
[0074] A bone screw removal device 100 according to one aspect
comprises an outer sleeve and an inner sleeve sized and shaped to
be received within the outer sleeve. In one aspect, the outer
sleeve 102 comprises a substantially cylindrical and hollow body,
such as shown in FIGS. 5B, that has an upper end and an opposing
lower end. An inner sleeve 110 can have a substantially
cylindrical, hollow body with a respective upper end and an
opposing lower end. The inner sleeve defines a conduit therein the
body. A flange 112 can be provided at the upper end of the inner
sleeve, the flange having a larger diameter than the diameter of
the cylindrical body, such as illustrated in FIG. 5A. It is
contemplated that the inner diameter of the outer sleeve is greater
than the outer diameter of the inner sleeve.
[0075] An inner sleeve 110, in one aspect, has a resilient tongue
member 114 that extends longitudinally down a portion of the body
of the inner sleeve. In one aspect, an upper portion of the tongue
member is defined by a portion of the body of the inner sleeve. In
a further aspect, the upper portion of the tongue member can be
spaced at a predetermined distance from the flange 112, such as
illustrated in FIG. 5A. As can be appreciated, the tongue member
can be a leaf spring having a spring constant K.sub.T. A lower
portion of the tongue member 114 can further comprise a protrusion
115 that extends outwardly from the lower portion. In one aspect,
the protrusion can be generally rectangular in shape; optionally
and without limitation, the protrusion can be any other shape, such
as semi-circular, partially circular, semi-elliptical, partially
elliptical, triangular, or other shape.
[0076] According to a further aspect, one or more longitudinal
guide slots 116 can be formed in a portion of the body of the inner
sleeve 110, such as shown in FIGS. 7A and 7C. Thus, the guide
slot(s) can be formed substantially parallel to a longitudinal axis
of the substantially cylindrical body of the inner sleeve. In a
particular aspect, a pair of opposing longitudinal guide slots can
be formed in the body, such that they are positioned approximately
180 degrees apart within the body of the inner sleeve. In a further
aspect, the guide slots can be respectively positioned
approximately 90 degrees from the center of the tongue member. The
guide slots can be formed as open slots that extend fully through
the side wall of the inner sleeve. Optionally, the guide slots 116
can be of a predetermined depth and do not extend fully through the
side wall, such as shown in FIG. 7A. In yet a further aspect, the
guide slots can extend longitudinally for a predetermined distance
along the body, the predetermined distance being less than the
total height of the body. Thus, as shown in FIGS. 7A and 7C, the
guide slot(s) 116 can begin at a spaced distance from the flange
112 and extend longitudinally to a spaced distance from the lower
edge of the inner sleeve. As will be explained further below, the
guide slot(s) are configured to receive a projection 106 of the
outer sleeve 102.
[0077] One or more openings, or notches, 104 can be defined in the
lower end of the outer sleeve. In one aspect, the opening can be a
substantially rectangular notch, such as shown in FIG. 5B.
Optionally, the notch can be semi-circular, partially circular,
semi-elliptical, partially elliptical, triangular, or any other
shape. In a further aspect, the notch 104 can be sized and shaped
to receive at least a portion of the protrusion 115 of the tongue
member 114. Thus, in one exemplary aspect, the protrusion can be
substantially rectangular and the notch has a complementary
rectangular shape to operatively receive the protrusion.
[0078] The outer sleeve 102 can further comprise longitudinal
projections 106 that extend inwardly from the inner wall of the
outer sleeve. In one aspect, the projections are substantially
parallel to the longitudinal axis of the substantially cylindrical
outer sleeve. The projections can be positioned approximately 180
degrees from each other along the inner wall of the outer sleeve.
In a further aspect, the projections can be respectively positioned
approximately 90 degrees from, on either side of, the center of the
notch 104. The projections, in one aspect, extend only partially
along the inner wall of the outer sleeve. Thus, as illustrated in
FIG. 7A for example, the projection(s) 106 can begin at a spaced
distance from an upper edge of the outer sleeve, and can end at a
spaced distance from a lower edge of the outer sleeve. In one
aspect, the length of each of the projections 106 is less than the
length of the guide slots 116 of the inner sleeve. The projections
can be, for example, from 25 to 75% of the length of the guide
slots. It is contemplated that the projections are sized, shaped
and positioned to be received by the guide slots of the inner
sleeve.
[0079] As may be appreciated, in various aspects, a single
retention member can be provided within each bore to retain a bone
screw therein. Optionally, two or more retention members can be
provided to retain a bone screw therein a respective bore.
Similarly, bone screw removal devices can be provided that have the
ability to displace single retention members, as well as dual (or
more) retention members. For example, in a bone screw retention
system in which a single retention member is used to retain each
bone screw, a bone screw removal device having a single tongue
member and protrusion, such as shown in FIGS. 5A-5B, 6, and 7A-7C,
can be provided. Optionally, a dual bone screw removal device
(i.e., having dual opposing tongue members) such as shown in FIGS.
8A-8C can be provided, although it is contemplated that only one
tongue member will be needed to displace the single retention
mechanism. Likewise, in a bone screw retention system having two or
more retention members retaining each bone screw, a bone screw
removal device having at least two tongue members can be
provided.
[0080] In use, the inner sleeve 110 is positioned therein the outer
sleeve 102 with the projections 106 inserted into respective guide
slots 116 such that the tongue member 114 and protrusion 115 are
longitudinally aligned with the notch 104 of the outer sleeve. As
illustrated in FIG. 7A, in one aspect, the projections are formed
within the outer sleeve at a predetermined position to allow the
inner sleeve to move from and between a first position in which the
flange 112 is spaced from the upper edge of the outer sleeve (FIG.
7A, left), to a second position in which the flange substantially
abuts the upper edge of the outer sleeve (FIG. 7A, right). As may
be appreciated, when in the first compressed position, the tongue
member 114 is pushed inwardly toward the inner portion of the inner
sleeve, such as shown in FIG. 7B, due to the presence of the
protrusion 115 at the distal end of the tongue member. As the inner
sleeve is moved toward and to the second relaxed position, the
resilient forces of the tongue member can urge the protrusion to
extend into the notch 104 of the outer sleeve 102. In one aspect
and as shown in the figures, in the second relaxed position, the at
least one protrusion engages an outer edge of the edge portion of
the at least one retention member of the retaining system.
Optionally, in the second relaxed position, the at least one
protrusion engages an inner edge of the edge portion of the at
least one retention member.
[0081] In one aspect, when the protrusion fully extends into the
opening, such as when the inner sleeve is in the second position,
the tongue member extends longitudinally at an angle substantially
parallel to the longitudinal axis of the tongue member. In a
further aspect, the protrusion can comprise an upper surface and an
opposing lower surface separated therefrom the upper surface by a
front surface of the protrusion. As illustrated in FIG. 9, in one
aspect, the upper surface can taper downwardly toward the front
surface of the protrusion so that as the inner sleeve is moved from
the first to the second position, the protrusion can progressively
ease into the notch 104.
[0082] As illustrated in FIGS. 9-12, in use, an exemplary bone
screw removal device can be used to remove a bone screw from a bone
retention system. A removal device can be placed within a bore 154
of an exemplary bone screw retention system until the lower surface
of the outer sleeve substantially abuts or rests on the shoulder
164 of the bone screw 160 positioned therein the bore. It is
contemplated that when the outer sleeve is positioned within the
bore, the inner sleeve is in a first position in which the flange
112 is spaced from the upper edge of the outer sleeve. The outer
sleeve can be positioned within the bore such that an opening or
notch 104 of the outer sleeve is positioned over a retention member
of the bone screw retention system. Thus, the respective retention
member may extend into the inner portion (i.e., the conduit) of the
outer sleeve via the respective notch. For example, as shown in
FIG. 12, an exemplary bone screw removal device 200 can be used to
remove a bone screw 160 retained by a rectangular retention member
572. The bone screw removal device, thus, can have a pair of
opposing notches 204a and 204b extending upwardly from the lower
surface of the outer sleeve.
[0083] The removal device can be positioned within the bore such
that each of the openings 204a and 204b is positioned over a
respective side of the rectangular retention member 572a and 572b.
It is contemplated that the openings can be sized and shaped to
receive the retention members. As shown in FIG. 12, when the outer
sleeve is positioned therein the bore, the retention members extend
inwardly toward the inner conduit of the outer sleeve. After the
outer sleeve is positioned within the bore, the inner sleeve can be
moved from the first position to a second position in which the
flange substantially abuts the upper edge of the outer sleeve. As
the inner sleeve is moved toward the second position, each of the
protrusions 215a and 215b can extend into the respective openings
204a and 204b. As described above, the upper surfaces of the
protrusions may taper downwardly toward the front surfaces of the
protrusions, such that the protrusions can progressively ease into
the openings as the inner sleeve is lowered. As the protrusions
enter the openings, the front surfaces can engage the respective
retention members. As can be appreciated, in one embodiment, if the
spring constant K.sub.T of the tongue members is greater than the
spring constant K.sub.R of the retention members, as the inner
sleeve is moved completely to the second position, as shown in FIG.
12, the retention members will be laterally pushed outwardly away
from the longitudinal axis of the bore by the protrusions, to a
position in which they no longer cover or retain the bone screw.
The progression of the inner sleeve from the first position to the
second position is also illustrated in FIGS. 11.
[0084] In another embodiment, a removal tool 140 can be inserted
into the removal device via the conduit of the inner sleeve.
Exemplary removal tools can comprise screwdrivers having a head
that mates with a portion of the head of the bone screw, or other
tools known in the art. In one aspect, a removal tool can be
configured to engage the at least one tongue member, thereby urging
the protrusion of the at least one tongue member laterally
outwardly away from the longitudinal axis of the bore, such as
shown in FIG. 13. Thus, even if the spring constant K.sub.T of the
at least one tongue member is not greater than the spring constant
K.sub.R of the at least one retention member, a distal portion of
the removal tool can engage the at least one tongue member and push
at least one tongue member, and therefore, the at least one
protrusion laterally outwardly away from the longitudinal axis of
the bore, which also pushes the at least one retention member
laterally outwardly away from the longitudinal axis of the bore to
a position in which the at least one retention member no longer
covers or retains the bone screw.
[0085] With the inner sleeve in the second position (and with the
retention member(s) no longer retaining the bone screw), the
physician or surgeon can use the removal tool to unscrew the bone
screw and thus remove it from the bore. As shown in FIG. 11 (far
right), as the bone screw is removed from the bore, it moves
upward. Because the outer sleeve rests on a portion of the shoulder
164, as the bone screw moves upwardly, the removal device moves
upwardly. Due to the tapered shape of the head of the bone screw,
the retention member can slide or ease into its relaxed, unflexed
position as the bone screw is removed. After use, the bone screw
removal device can be reused. A physician can manually press the
protrusion(s) inwardly and then slightly upwardly so that the inner
sleeve can be returned to its first position.
[0086] FIGS. 14A-14D illustrate another exemplary bone screw
removal device 300. The bone screw removal device can comprise a
main sleeve 302 that is substantially cylindrical and defines a
conduit therein. In a further aspect, the main sleeve has an upper
surface and an opposing lower surface. The main sleeve can define
one or more openings 304 extending upwardly from the lower surface
of the main sleeve. The removal device 300 can further comprise a
removal sleeve 320 comprising a band portion 322 that is
substantially cylindrical and has a diameter greater than a
diameter of the main sleeve 302. The removal sleeve can further
comprise a tongue member 324 that extends downwardly from the band
portion. As shown in FIG. 14C, in one aspect, in its resting (i.e.,
unstressed) position the tongue member extends downwardly from the
band portion at an angle that is less than 90.degree.. For example,
the tongue member can be at an angle of between 45.degree. and
90.degree.. In a further aspect, the tongue member can be at an
angle of between 75.degree. and 90.degree., such as 85.degree.. The
removal sleeve 320 can be positioned around the main sleeve 302
with the tongue member 324 extending downwardly over the opening
304. In this position, the tongue member can extend inwardly into
the main sleeve via the opening, such as shown in FIG. 14C (resting
position).
[0087] In a further aspect, the removal sleeve can be removably
attached to the main sleeve. For example, in one aspect, one or
more indentations can be formed within the exterior surface of the
main sleeve. The band portion of the removal sleeve can have
protrusions extending inwardly from its inner surface. The
protrusions can be sized, shaped and positioned to be received by
the indentations of the main sleeve when the removal sleeve is
placed around the main sleeve. Thus, the removal sleeve can snap
into a desired position for use. In a further aspect, the
indentation(s) can be substantially round, such as, without
limitation, hemispherical, partially spherical, etc. The
protrusion(s) can be similarly shaped to be received by the
indentation.
[0088] Optionally, a circumferential groove can be formed on the
main sleeve that can be sized and shaped to receive the band
portion of the removal sleeve. Thus, the groove can have a height
that is slightly greater than the height of the band portion, and
can have a predetermined depth sufficient to receive the band
portion and substantially prevent it from moving (i.e., up or down)
when it is in use. In another aspect, a plurality of
circumferential flanges can be formed on the main sleeve. The
flanges can be spaced at a predetermined distance from each other
along the main sleeve such that the band portion of the removal
sleeve can be received and secured therebetween. In yet another
aspect, the removal sleeve can be fixedly attached to the main
sleeve in a predetermined position.
[0089] The bone screw removal device 300 can be used by a physician
to remove a bone screw from a bone screw retention system. The main
sleeve 302 can be positioned within a bore, such that the main
sleeve rests on the shoulder of the bone screw. As described above,
the main sleeve can be positioned therein the bore such that the
opening or notch 304 is positioned over a respective retention
member, allowing the retention member to extend inwardly into the
main sleeve via the opening. A removal tool can be inserted into
the conduit of the main sleeve to remove the bone screw. As the
tool is inserted therein the main sleeve, it is contemplated that
it can contact the tongue member and thus force the tongue member
to its in-use position (FIG. 14D). As the tongue member is forced
or moved to its in-use position, it will consequently move the
respective retention member to a position in which it no longer
obstructs or retains the bone screw, and the bone screw can be
removed. It is contemplated that the exemplary bone screw removal
device 300 can comprise more than one opening, and more than one
tongue member, such that multiple retention members of the bone
screw retention system can substantially simultaneously be moved to
non-retaining positions.
[0090] According to various aspects, various components of a bone
screw retention system and bone screw removal device can be formed
from a biocompatible, flexible material such as, but not limited
to, shape-memory alloys, titanium alloy and the like as disclosed
in U.S. Pat. Nos. 4,857,269 and 4,952,236, which are incorporated
in their entirety herein by reference. Further, polymeric materials
such as, for example, ultra-high molecular weight polyethylene can
also be used to form various components of the bone screw retention
and removal system. Such exemplary materials can be used, for
example, to form the exemplary retention members described above.
The materials can also be used to form the tongue members of the
various bone screw removal devices described above. In yet another
aspect, such materials can be used to form all of the components of
the exemplary bone screw removal devices described above.
[0091] It will be apparent to those skilled in the art that various
modifications and variations can be made in the present invention
without departing from the scope or spirit of the invention. Other
embodiments of the invention will be apparent to those skilled in
the art from consideration of the specification and practice of the
invention disclosed herein.
* * * * *