U.S. patent application number 16/267198 was filed with the patent office on 2019-06-06 for radiolucent screw with radiopaque marker.
The applicant listed for this patent is INNOVASIS, INC.. Invention is credited to Brent A. Felix, David A. Hershgold, David N. McKean.
Application Number | 20190167310 16/267198 |
Document ID | / |
Family ID | 41354042 |
Filed Date | 2019-06-06 |
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United States Patent
Application |
20190167310 |
Kind Code |
A1 |
Felix; Brent A. ; et
al. |
June 6, 2019 |
RADIOLUCENT SCREW WITH RADIOPAQUE MARKER
Abstract
A bone screw includes an elongate shaft extending longitudinally
between a proximal end and an opposing distal end. The shaft bounds
a first passageway at least partially extending between the
proximal end and the distal end. The shaft is comprised of a
radiolucent material. A core is disposed within the first
passageway of the shaft. The core can be comprised of a radiolucent
or radiopaque material. A head is either integrally formed with or
secured to the proximal end of the shaft or the proximal end of the
core. The head can also bound a second passageway that extends
through the head and is aligned with the first passageway. The core
can also be disposed within the second passageway.
Inventors: |
Felix; Brent A.; (Sandy,
UT) ; McKean; David N.; (Bountiful, UT) ;
Hershgold; David A.; (Draper, UT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INNOVASIS, INC. |
Salt Lake City |
UT |
US |
|
|
Family ID: |
41354042 |
Appl. No.: |
16/267198 |
Filed: |
February 4, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13063605 |
Mar 11, 2011 |
10194950 |
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PCT/US09/56508 |
Sep 10, 2009 |
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16267198 |
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12208986 |
Sep 11, 2008 |
9408649 |
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13063605 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 2017/0088 20130101;
A61B 17/866 20130101; A61B 17/7032 20130101; A61B 17/864 20130101;
A61B 2017/0092 20130101; A61B 90/39 20160201; A61B 2017/00955
20130101; A61B 17/7037 20130101; A61B 17/8685 20130101; A61B
17/8625 20130101; A61B 2090/3966 20160201 |
International
Class: |
A61B 17/70 20060101
A61B017/70; A61B 17/86 20060101 A61B017/86 |
Claims
1. A bone screw comprising: an elongate shaft extending
longitudinally between a proximal end and an opposing distal end,
the shaft bounding a first passageway at least partially extending
between the proximal end and the distal end, the shaft being
comprised of a radiolucent material; and a core disposed within the
first passageway of the shaft, the core being comprised of a
radiopaque material.
2. The bone screw as recited in claim 1, wherein the shaft
comprises an exterior surface having a radially outwardly
projecting helical thread formed thereon.
3. The bone screw as recited in claim 1, further comprising a head
or a collar rigidly secured to the proximal end of the shaft.
4. The bone screw as recited in claim 3, wherein the head or the
collar is comprised of a radiopaque material.
5. The bone screw as recited in claim 3, wherein the head or the
collar is comprised of a metal.
6. A bone screw comprising: an elongate shaft extending
longitudinally between a proximal end and an opposing distal end,
the shaft bounding a first passageway at least partially extending
between the proximal end and the distal end, the shaft being
comprised of a radiolucent material; a core disposed within the
first passageway of the shaft, the core being comprised of a
radiopaque material that comprises a metal, that shaft being
comprised of a pre-fabricated sheet comprised of the one or more
radiolucent fibers and an adhesive that encircles the radiopaque
core so that the one or more radiolucent fibers radially encircling
the core; an enlarged head disposed at an end of the core and being
comprised of the same radiopaque material as the core, the core and
the head being integrally formed as a single, one piece, unitary
member, the enlarged head having a maximum diameter that is larger
than a maximum diameter of the core; and a helical thread recessed
into the pre-fabricated sheet encircling the radiopaque core.
7. The bone screw as recited in claim 6, wherein the head is
secured to the proximal end of the shaft.
8. The bone screw as recited in claim 6, wherein the first
passageway extends completely through the shaft.
9. The bone screw as recited in claim 6, wherein the core has an
outer surface with a projection projecting therefrom.
10. The bone screw as recited in claim 6, wherein the head and the
core have an interior surface that bound a passageway that
longitudinally extends through the core and the head.
11. The bone screw as recited in claim 6, wherein the head
comprises an annular shoulder, an annular head portion, and a neck
formed therebetween, the neck inwardly constricting relative to the
annular shoulder and the annular head.
12. The bone screw as recited in claim 6, wherein the shaft
encircles the core but does not encircle the head.
13. The bone screw as recited in claim 6, wherein the core extends
the entire length of the shaft.
14. A method of manufacturing a bone screw, the method comprising:
forming an elongated shaft about a core, an enlarged head being
integrally formed on an end of the core, the shaft having a
longitudinal axis extending between a proximal end and an opposing
distal end with a first passageway that extends completely through
the shaft along the longitudinal axis, the core being disposed
within the first passageway and extending along the longitudinal
axis, the shaft being comprised of a radiolucent material that
includes one or more radiolucent fibers that radially encircles the
core, the core and head being comprised of a radiopaque material,
wherein the shaft is formed by: winding the one or more radiolucent
fibers having an adhesive thereon about the radiopaque core; or
winding a sheet comprised of the one or more radiolucent fibers and
an adhesive about the radiopaque core; and forming a helical thread
on an exterior surface of the shaft by removing a portion of the
exterior surface of the shaft.
15. The bone screw as recited in claim 14, wherein the one or more
radiolucent fibers radially encircle the core in a helical pattern
that extends along a length of the core.
16. The bone screw as recited in claim 14, wherein the radiopaque
material of the core is comprised of titanium, stainless steel,
tungsten, cobalt based alloys, cobalt chrome alloys, nickel
titanium alloys, platinum, iridium, gold, barium and alloys
thereof.
17. The method as recited in claim 14, wherein the step of removing
a portion of the exterior surface of the shaft is accomplished
through the use of a grinder, lathe or cutting tool.
18. The method as recited in claim 14, wherein the one or more
radiolucent fibers radially encircle the core in a helical pattern
that extends along a length of the core.
19. The method as recited in claim 14, wherein the core and the
head are comprised of a metal.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 13/063,605, filed Mar. 11, 2011, which is a US nationalization
of PCT/US2009/056508, filed Sep. 10, 2009, which is a CIP of U.S.
application Ser. No. 12/208,968, filed Sep. 11, 2008, now U.S. Pat.
No. 7,922,788, issued Apr. 12, 2011, which are hereby incorporated
by reference in their entirety.
BACKGROUND OF THE INVENTION
1. The Field of the Invention
[0002] The present invention relates to polyaxial and fixed bone
screws and components thereof that can be used for stabilizing
adjacent vertebrae of the spine or otherwise fixing to bone.
2. The Relevant Technology
[0003] Polyaxial and fixed bone screws (often referred to as
pedicle screws) are commonly used in spinal operations for
adjusting or stabilizing adjacent vertebrae. For example, in one
conventional procedure a first bone screw is screwed into a first
vertebra while a second bone screw is screwed into an adjacent
second vertebra. A stabilizing rod is then secured between the bone
screws so as to fix the adjacent vertebrae relative to each other.
Bone screws can be positioned on each side of each vertebra and can
be positioned in any number of consecutive vertebrae with one or
more stabilizing rods extending between the different bone
screws.
[0004] A conventional bone screw comprises a threaded screw portion
having a collar either fixedly or pivotably mounted on the end
thereof. The screw portion is threaded into the bone and the
stabilizing rod is received within the collar and secured therein.
Other conventional bone screws are used for purposes such as
securing a bone plate over a facture, fixing a cranial plate,
attaching ligaments, mounting an implant and the like. To be strong
enough to handle the stresses placed upon them, the bone screws are
typically made of titanium or some other biocompatible metal. Being
made of metal allows the doctor to view the bone screws using X-ray
photographs during and after implantation.
[0005] However, because the bone screws are made of metal, the bone
screws block X-rays passing through the body, in effect obscuring
adjacent bone and other X-ray viewable internal structures
surrounding the area and thereby preventing the surgeon from
viewing those structures on an X-ray photograph. The metal bone
screws can also disrupt MRI and other types of images. This can
limit a surgeon's ability to ensure proper placement of the bone
screws and diagnose and treat problems that arise near the location
of the bone screws after the bone screws have been implanted.
[0006] Accordingly, what is needed are polyaxial and fixed bone
screws that overcome some or all of the above disadvantages.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Various embodiments of the present invention will now be
discussed with reference to the appended drawings. It is
appreciated that these drawings depict only typical embodiments of
the invention and are therefore not to be considered limiting of
its scope.
[0008] FIG. 1 is a perspective view of a spinal stabilizing system
incorporating a polyaxial bone screw according to one embodiment of
the present invention;
[0009] FIG. 2 is an exploded perspective view of the polyaxial bone
screw shown in FIG. 1;
[0010] FIG. 3 is a perspective view of the assembled screw portion
of the bone screw shown in FIG. 2;
[0011] FIG. 4 is a perspective view of the shaft portion of the
screw portion shown in FIG. 3;
[0012] FIG. 5 is a top perspective view of the head of the screw
portion shown in FIG. 3;
[0013] FIG. 6 is a bottom perspective view of the head of the screw
portion shown in FIG. 3;
[0014] FIG. 7 is a bottom plan view of the assembled screw portion
shown in FIG. 3;
[0015] FIGS. 8A-8C are perspective views of alternative embodiments
of cores;
[0016] FIGS. 9A-9D are cross-sectional bottom views of alternative
embodiments of screw portions of bone screws;
[0017] FIG. 10 is a cross sectional side view of an assembled screw
portion according to one embodiment having a positioning ring
disposed within the shaft;
[0018] FIG. 11 is a perspective view of an assembled screw portion
according to one embodiment having a ring layer painted
thereon;
[0019] FIG. 12 is a perspective view of the collar shown in FIG.
2;
[0020] FIG. 13 is a cross sectional side view of a portion of the
assembled polyaxial bone screw shown in FIG. 1;
[0021] FIG. 14 is a perspective view of impregnated fibers being
wound on the core shown in FIG. 2;
[0022] FIG. 15 is a perspective view of sheets of fibers being
wound on the core shown in FIG. 2;
[0023] FIG. 16 is a perspective view of a blank that is formed
during manufacture of the screw portion shown in FIG. 3 according
to one embodiment;
[0024] FIG. 17 is a perspective view of the screw portion shown in
FIG. 3 in a partially assembled state;
[0025] FIG. 18 is an exploded perspective view of an alternative
embodiment of the screw portion shown in FIG. 17 wherein the head
and the shaft of the screw portion are integrally formed as a
unitary member;
[0026] FIG. 19 is a perspective view of an alternative embodiment
of an assembled screw portion of a bone screw according to the
present invention;
[0027] FIG. 20 is a perspective view of the screw portion shown in
FIG. 19 in a partially assembled state;
[0028] FIG. 21 is a bottom perspective view of the head of the
screw portion shown in FIG. 20;
[0029] FIG. 22 is a bottom perspective view of an alternative
embodiment of the head of the screw portion shown in FIG. 20;
[0030] FIG. 23 is a partial top perspective view of an alternative
embodiment of the shaft of the screw portion shown in FIG. 20;
[0031] FIG. 24 is a top perspective view of a portion of another
alternative embodiment of the shaft of the screw portion shown in
FIG. 20;
[0032] FIG. 25 is a perspective view of an alternative embodiment
of an assembled screw portion of a bone screw according to the
present invention;
[0033] FIG. 26 is a perspective view of a portion of the screw
portion shown in FIG. 25;
[0034] FIG. 27 is a bottom perspective view of the head of the
screw portion shown in FIG. 25;
[0035] FIG. 28 is one embodiment of a fixed bone screw wherein a
collar is rigidly secured to the end of the shaft;
[0036] FIG. 29 is an exploded view of the bone screw shown in FIG.
28;
[0037] FIG. 30 is a perspective bottom view of the collar shown in
FIG. 29;
[0038] FIG. 31 is an exploded perspective view of an alternative
embodiment of the fixed bone screw shown in FIG. 28 wherein the
collar and the shaft of the bone screw are integrally formed as a
unitary member;
[0039] FIG. 32 is a exploded perspective view of an alternative
embodiment of a spinal stabilizing system;
[0040] FIG. 33 is an exploded perspective view of the screw portion
of the spinal stabilizing system shown in FIG. 32;
[0041] FIG. 34 is a cross sectional side view of the core and
integral head of the screw portion shown in FIG. 33;
[0042] FIG. 35A is a top perspective view of the saddle shown in
FIG. 32;
[0043] FIG. 35B is a bottom perspective view of the saddle shown in
FIG. 35A;
[0044] FIG. 36 is an exploded perspective view of the fastener
shown in FIG. 32;
[0045] FIG. 37 is a cross sectional side view of the assembled
spinal stabilizing system shown in FIG. 32;
[0046] FIG. 38 is a perspective view of an alternative embodiment
of the saddle shown in FIG. 35A;
[0047] FIG. 39 is an exploded perspective view of an alternative
embodiment of a screw portion having a modified core;
[0048] FIG. 40 is an exploded perspective view of another
alternative embodiment of a screw portion having a modified
core;
[0049] FIG. 41 is an exploded perspective view of a bone screw
having a modified head; and
[0050] FIG. 42 is an exploded perspective view of another bone
screw having a modified head.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0051] Depicted in FIG. 1 is a spinal stabilizing system 101
incorporating features of the present invention. Spinal stabilizing
system 101 can be used for stabilizing adjacent vertebrae of a
spine as part of a procedure for fusing together the adjacent
vertebrae. Spinal stabilizing system 101 can also be used for
stabilizing a series of consecutive vertebrae for manipulation of
the spine to correct spinal deformities such as scoliosis. It is
appreciated that spinal stabilizing system 101 and/or discrete
elements thereof can also be used in other procedures for
anchoring, manipulating, and/or stabilizing various bones.
[0052] As depicted in FIG. 1, stabilizing system 101 includes a
polyaxial bone screw 100 comprising an elongated screw portion 102
and a collar 104 pivotally mounted thereon. Stabilizing system 101
also includes a fastener 106 that is selectively engageable with
collar 104 to secure polyaxial bone screw 100 to a stabilizing rod
107. The above identified components of polyaxial screw 100 and
their relative interaction will now be discussed in greater
detail.
[0053] As shown in FIGS. 2 and 3, screw portion 102 of bone screw
100 comprises an elongated shaft 108 having a head 110 disposed
thereon with a core 112 extending longitudinally through shaft 108
and head 110.
[0054] Turning to FIG. 4, shaft 108 is elongated and has a proximal
end 114 and a spaced apart distal end 116 with a central
longitudinal axis 118 extending therebetween. Shaft 108 comprises
an elongated shaft body 113 and an attachment member 126 formed at
the proximal end thereof. Shaft body 113 has an exterior surface
122 that extends between proximal end 114 and distal end 116. One
or more threads 120 helically encircle and radially outwardly
project from exterior surface 122 of shaft body 113 along the
length thereof. The one or more threads 120 can have a variety of
different pitches and configurations, and, if desired, can be
self-tapping. Proximal end 114 of shaft body 113 terminates at an
end face 132 while distal end 116 of shaft body 113 terminates at a
tapered tip 124. End face 132 is typically planar and disposed
orthogonal to central longitudinal axis 118, although this is not
required. Tapered tip 124 has a substantially conical configuration
for ease in penetration into a bone or predrilled hole. A cutting
edge 125 can also be disposed on the tapered portion of tip 124 to
aid in cutting the bone in bone screw embodiments that are
self-tapping.
[0055] Attachment member 126 centrally projects from end face 132
of shaft body 113. As discussed below in greater detail, attachment
member 126 is used to engage and secure head 110 (FIG. 2) to shaft
108. As such, attachment member 126 is sized and shaped so as to
fit within a complementary attachment recess 128 disposed on head
110 (see FIG. 6). In the embodiment depicted, attachment member 126
has an encircling side wall 130 that proximally extends from end
face 132 of shaft body 113 to a terminal end face 134. End faces
132 and 134 are depicted as being substantially parallel with each
other and orthogonal to longitudinal axis 118, although this is not
required. Side wall 130 is depicted as being substantially parallel
to longitudinal axis 118, but this is also not required.
[0056] In the depicted embodiment, side wall 130 of attachment
member 126 comprises a substantially cylindrical portion 135 and a
flat 136. Flat 136 in effect removes a portion of the rounded side
of the cylinder portion 135. In an alternative embodiment side wall
130 is formed without a flat. Other cross sectional attachment
shapes can alternatively be used. For example, side wall 130 of
attachment member 126 can be oval, polygonal, star shaped,
irregular, or the like. Other shapes are also possible.
[0057] Continuing with FIG. 4, shaft 108 includes an internal
surface 138 that bounds a first passageway 140 extending
longitudinally through shaft 108 between proximal end 114 and
distal end 116. First passageway 140 extends along central
longitudinal axis 118, through terminal end face 134 of attachment
member 126 and through tapered tip 124. In the embodiment depicted,
first passageway 140 has a substantially circular cross-sectional
shape. Other cross-sectional shapes can alternatively be used for
first passageway 140. For example, first passageway 140 can be oval
shaped, star shaped, polygonal shaped, irregular or the like. First
passageway 140 can also be symmetrically or non-symmetrically
shaped. In alternative embodiments, first passageway 140 need not
extend the full length of shaft 108. For example, first passageway
140 need not extend through tip 124.
[0058] Shaft 108 can be comprised of a radiolucent material that
will allow viewing of adjacent bone or other internal structures on
an X-ray photograph that are in the viewing path of shaft 108.
Using radiolucent material for the shaft 108 will also minimize
scattering caused by commonly used metallic or other radiopaque
shafts in X-Rays, CAT scans, MRI's, and other types of imaging
systems.
[0059] One example of a radiolucent material that can be used in
shaft 108 is a radiolucent biocompatible fiber and adhesive matrix.
In this embodiment, an adhesive is applied to one or more elongated
biocompatible fibers that are then wound about core 112, a rod, or
other object to form shaft 108. This is typically done by winding
two or more layers of fibers about core 112 or other object. The
fibers can be wound one fiber at a time or multiple fibers at a
time in a fiber bundle or tow. The fibers are typically of
indefinite length and are wound from a spool or other carrier and
then cut when the winding is completed. Alternatively, the fibers
can comprise one or more shorter fibers that are wound or otherwise
disposed within shaft 108. In still other embodiments, the fibers
can be included in a sheet or other structure and then wound about
core 112 or other object in one or two or more layers. Various
winding patterns and fiber orientation can also be used. Methods of
manufacturing the shaft 108 are discussed in more detail below
[0060] Many different types of biocompatible fibers and adhesives
can be used to form radiolucent shaft 108. For example, the fibers
can be comprised of carbon, fiberglass, poly paraphenylene
terephthalamide (PPTA, more commonly known as Kevlar.RTM.), other
aramids, and ceramics. Other radiolucent, biocompatible fibers
having desired properties can also be used.
[0061] Although fibers having multiple different properties can be
used, typical fibers have a diameter in a range between about 5
microns to about 18 microns with about 5 microns to about 7 microns
being more common and a tensile strength in a range between about
300 ksi to about 1000 ksi with about 600 ksi to about 1000 ksi
being more common. Other diameters and tensile strengths can be
used. The fibers can be sized or unsized. By "unsized," it is meant
that the fibers have not been coated with a material to improve
adhesion of the resin or adhesive. If the fibers are sized,
biocompatibility of the sizing needs to be considered. When bundles
of fibers are used, the tow of the fibers (i.e., the number of
fibers per bundle) can range from about 1 k to about 72 k with
about 3 k to about 24 k being more common. Other tow ranges can
also be used. In one specific embodiment, the fibers comprise a
continuous high strength, PAN based carbon fiber, 34-700, 12 k
(tow), "unsized". In another specific embodiment, the fibers
comprise a continuous high strength, PAN based carbon fiber,
34-700, 3 k (tow), sized.
[0062] Examples of biocompatible adhesives that can be used with
the fibers include thermoplastic materials, thermoset materials and
ceramics. Examples of thermoplastic materials that can be used
include polyester, vinylester, polycarbonate, polyetheretherketone
(PEEK), polyaryletherketone (PAEK), polyethylene, polyurethane, and
polyamide. Examples of thermoset materials that can be used include
epoxies and polyimides. Exemplary biocompatible epoxies include the
Master Bond Inc. epoxies EP42HT-2 and EP45HT MED and the Epotek
epoxies 301-2 and 375. Examples of ceramics that can be used
include alumina and zirconia. Other epoxies, ceramics, plastics and
resins that are implantable, biocompatible, sterilizable, and have
the desired strength properties can also be used. In an alternative
embodiment, the radiolucent material used in shaft 108 can simply
comprise the adhesive materials as discussed above without the
fibers. If desired, other additives and fillers can be combined
with the adhesive materials.
[0063] Returning to FIGS. 2 and 3, head 110 is disposed on proximal
end 114 of shaft 108 so as to engage with attachment member 126. As
shown in FIG. 3, head 110 comprises a rounded substantially
semi-spherical bottom portion 150 that can bias and rotate against
collar 104. Bottom portion 150 has a first end 142 on which a face
144 is formed and a second end 146. A top portion 152 centrally
projects from face 144 and is shaped to allow a tool to engage and
rotate screw portion 102. An annular neck 154 extends from the
second end 146 of bottom portion 150 of head 110 to a bottom
surface 156 (see FIG. 6). Neck 154 has an encircling exterior
surface 155 having a substantially concave transverse cross
section. In the depicted embodiment, top portion 152 has an
encircling sidewall 158 that extends from face 144 to a top surface
160. Sidewall 158 typically has a polygonal shape so that it can
mate with a driver or other tool for tightening and loosening bone
screws. Other shapes, such as oval or irregular, can also be used.
Alternatively, a socket can be formed within top surface 160 or on
face 144 of bottom portion 150 for engaging a tool.
[0064] Turning to FIG. 5, head 110 includes a central longitudinal
axis 162 extending through head 110 between top surface 160 of top
portion 152 and bottom surface 156 of neck 154. When screw portion
102 is assembled, axis 118 of shaft 108 (see FIG. 4) and axis 162
of head 110 can be aligned with each other.
[0065] An engagement slot 164 is formed on head 110. Engagement
slot 164 comprises a pair of opposing side walls 166 and 168 that
are generally disposed in parallel planes and extend to a rounded
floor 170 and a back wall 172. Back wall 172 typically intersects
with floor 170 at a right angle while back wall 172 is disposed
generally parallel to central longitudinal axis 162 at a distance
spaced apart therefrom. In alternative embodiments, floor 170 need
not be rounded but can be flat, V-shaped, or have other
configurations. It is appreciated that engagement slot 164 can have
a variety of different configurations and merely needs to be sized,
shaped, and oriented to permit the desired pivoting of collar 104
and rotation of screw portion 102 as discussed below in greater
detail.
[0066] Turning to FIG. 6, attachment recess 128 is formed in bottom
surface 156 of head 110 to mate with attachment member 126 of shaft
108 (FIG. 4). As such, attachment recess 128 is sized and shaped so
as to receive attachment member 126. For example, in the depicted
embodiment, attachment recess 128 is bounded by an encircling side
wall 174 that extends from bottom surface 156 to a floor 176.
Attachment recess 128 has a straight section 178 of side wall 174
corresponding to flat 136 of side wall 130 of attachment member
126. (FIG. 4) In an alternative embodiment, attachment member 126
is disposed on head 110 and attachment recess 128 is formed on
shaft 108. It is appreciated that attachment member 126 and
attachment recess 128 can have a variety of different
configurations and merely need to be sized, shaped, and oriented to
permit attachment member 126 and attachment recess 128 to
selectively mate with each other when head 110 and shaft 108 are
secured together, as discussed below in greater detail.
[0067] Returning to FIG. 5 in conjunction with FIG. 6, similar to
shaft 108, head 110 includes an internal surface 180 bounding a
second passageway 182 that extends through head 110. Second
passageway 182 extends along central longitudinal axis 162, between
top surface 160 and attachment recess 128 (or attachment member
126, if attachment member 126 is disposed on head 110). Second
passageway 182 can be of the same cross-sectional shape as first
passageway 140 or can be of a different shape. For example, in the
depicted embodiment, second passageway 182 has a substantially
circular cross sectional shape except for a straight portion 184 on
one of the sides. Other shapes can also be used.
[0068] Head 110 can comprise a radiolucent material, such as any of
those listed above for shaft 108. In one embodiment, head 110
comprises the same or different radiolucent material as shaft 108.
Alternatively, head 110 can comprise a radiopaque material in place
of or in addition to a radiolucent material. Examples of radiopaque
metals that can be used in head 110 are titanium, stainless steel,
tungsten, cobalt based alloys, cobalt chrome alloys, nickel
titanium alloys such as Nitinol, platinum/iridium, gold, barium and
alloys thereof. Other radiopaque materials that can be used include
cortical bone and synthetic bone. The radiopaque material may also
comprise the radiolucent materials discussed above having a
radiopaque filler disposed therein. Other biocompatible metals and
other radiopaque materials having desired properties can also be
used.
[0069] Applicant notes that due to the electric potential between
carbon and titanium, corrosion may occur between the two surfaces
in the presence of an electrolyte. However, because the electron
potential is small, the corrosion would be very small, if it occurs
at all. Furthermore, the adhesive used in the matrix acts as an
insulator. To combat any corrosion that may occur, anodization or
passivation of the metals can be performed before assembly.
[0070] Returning to FIG. 2, core 112 comprises a slender rod having
an encircling outer surface 198 that extends between a proximal end
200 and an opposing distal end 202. Core 112 is designed to be
disposed within first and second passageways 140 and 182 of
assembled shaft 108 and head 110, respectively. As discussed below,
this can be accomplished by forming the shaft 108 about core 112 or
by inserting core 112 into passageway 140 after the passageway 140
has been formed. It is appreciated that core 112 need not extend
all the way through shaft 108 but can be disposed only along a
portion thereof. Thus, both core 112 and first passageway 140 can
extend only along a portion of shaft 108.
[0071] Core 112 comprises a head portion 204 at proximal end 200
and a shaft portion 206 at distal end 202. Head portion 204 of core
112 is shaped to be disposed within second passageway 182 of head
110 and shaft portion 206 is shaped to be disposed within first
passageway 140 of shaft 108. For example, in the embodiment
depicted, shaft portion 206 has a substantially circular cross
section (see FIG. 7) to match the circularly shaped first
passageway 140, and head portion 204 has a substantially circular
cross section with a segment removed to form a straight section 208
so as to match the shape of second passageway 182. In some
embodiments, the cross-sectional shapes of head portion 204 and
shaft portion 206 comprise the same shape.
[0072] Other variations can also be incorporated into the head
portion 204 and/or the shaft portion 206 of core 112. For example,
one or more channels or projections can be incorporated into core
112 to increase engagement between core 112 and shaft 108 or head
110, thereby minimizing the potential for separation therebetween.
In FIG. 8A, a core 112a includes two channels 400a and 400b
longitudinally spaced apart from each other. Each channel 400 is
bounded by an encircling side wall 402 having a substantially
circular cross section with a diameter less than the diameter of
outer surface 198. As such, channels 400 are also bounded by a
first end face 404 and a second end face 406 that extend between
the outer surface 198 and the sidewall 404 at either end of
channels 400. The end faces can be substantially orthogonal to the
outer surface 198 (as shown), or form some other angle with the
outer surface 198. Although FIG. 8A shows two channels 400, it is
appreciated that one or three or more channels 400 can
alternatively be used.
[0073] Furthermore, instead of or in conjunction with channels 400,
one or more projections can be formed along core 112a. The
projections can comprise a flange 401a that encircles or partially
encircles core 112a, one or more ribs 401b that extend along core
112a, knobs, or projections having a variety of other
configurations. Instead of having a diameter less than the diameter
of outer surface 198, the projections 401 have a diameter greater
than the diameter of outer surface 198. As such, the projections
extend out from outer surface 198.
[0074] The sizes and locations of channels 400 or projections 401
can vary widely. In some embodiments, the locations of the channels
or projections are chosen so as to provide a length indicator when
the core 112a is viewed on an X-ray. That is, when viewed on an
X-ray, the channel or projection can identify to the doctor a
predefined length of the core 112a.
[0075] FIG. 8B shows another surface shape variation incorporated
into a core 112b to help minimize the potential for separation from
shaft 108 or head 110. In FIG. 8B, a helical thread 408 is formed
on outer surface 198. If the first and second passageways 140 and
182 are likewise threaded, the shaft 108 and/or the head 110 can be
threaded onto the core 112 during manufacturing and assembly, if
desired. The size, shape, and pitch of the helical thread can
vary.
[0076] FIG. 8C shows another variation incorporated into a core
112c. In FIG. 8C, core 112c has a cannula 410 that longitudinally
extends completely through core 112c between proximal end 200 and
distal end 202. Cannula 410 can be used during implantation to pass
a guidewire or other surgical device through is assist in
positioning bone screw 100 and/or can be used for performing other
surgery techniques. The cross sectional size and shape of cannula
410 can vary, depending on the cross-sectional size and shape of
core 112c.
[0077] It is appreciated that any of the core variations described
above can be combined, if desired, in the same core 112. For
example, in one embodiment, a cannula and one or more channels or
projections could be included in the same core, while in another
embodiment a cannula could be included in a threaded core. Other
combinations are also possible.
[0078] Various geometric cross sectional shapes can alternatively
be used for the head portion 204 and/or the shaft portion 206 of
core 112. For example, FIGS. 9A-9D disclose various embodiments of
shaft portion 206 having different cross sectional shapes. FIG. 9A
shows an embodiment in which shaft portion 206a is oval shaped.
FIG. 9B shows an embodiment in which shaft portion 206b is
generally star shaped. FIG. 9C shows an embodiment in which shaft
portion 206c is generally polygonal shaped. In some embodiments
head portion 204 and/or shaft portion 206 have a symmetrical cross
sectional shape, such as shaft portion 206c shown in FIG. 9C; in
other embodiments head portion 204 and/or shaft portion 206 have a
non-symmetrical cross sectional shape, such as shaft portion 206d
shown in FIG. 9D. Head portion 204 and/or shaft portion 206 can
also use a combination of curved and linear segments, such as head
portion 204 shown in FIG. 2. It is appreciated that the
aforementioned core shapes are exemplary only and that other
shapes, that are typically non-circular, can alternatively be used.
It is appreciated that the passageways in shaft 108 and head 110 in
which core 112 is received can have the same complementary
configuration as core 112. One benefit of producing core 112 with a
non-circular configuration is that greater engagement can be formed
between core 112 and screw portion 102, thereby minimizing the
potential for separation therebetween.
[0079] Core 112 typically has a maximum outer diameter in a range
between about 1 mm to about 3.5 mm, with about 2 mm to about 3 mm
being common. In one embodiment, core 112 has a maximum diameter
that is less than about 3 millimeters and more commonly less than
about 2 millimeters. Other diameters can also be used.
[0080] Core 112 is typically comprised of a radiopaque material,
such as those previously discussed with regard to head 110. Core
112 can be comprised of the same radiopaque material as head 110 or
can be comprised of a different radiopaque material. One advantage
of using a radiopaque material in core 112 while using a
radiolucent material in shaft 108 is that only the thin core 112
will be seen on an X-ray during and after implantation of screw
portion 102. This aids the surgeon in positioning screw portion 102
when implanting screw portion 102, yet allows other internal body
structures to be viewed by X-ray during and after screw portion 102
implantation. Where core 112 is comprised of a radiopaque material,
core 112 comprises a marker for screw portion 102.
[0081] In alternative embodiments, core 112 can be comprised of a
radiolucent material, such as those previously discussed with
regard to shaft 108. For example, core 112 can comprise an adhesive
as discussed with regard to shaft 108 that is free of fibers or
that that has elongated or chopped fibers embedded therein. In
these embodiments, screw portion 108 can be completely free of any
radiopaque markers or, alternatively, one or more radiopaque
markers can be added thereto, as discussed below. In some
embodiments, core 112 is comprised of the same material as shaft
108. In still other embodiments, core 112 can be comprised of both
radiolucent and radiopaque materials. For example, small pieces of
radiopaque material, such as small pieces of metal, i.e., metal
particles, fibers, and/or spheres, can be embedded within or spaced
between a matrix of a radiolucent material such as an epoxy.
[0082] In one method of manufacture, the radiolucent fibers and
adhesive can be wound around a removable rod. Once shaft portion
108 is formed by the radiolucent material about the rod, the rod is
removed leaving passageway 140. Passageway 140 can then be
backfilled with a radiolucent material as discussed above or a
combination of radiolucent and radiopaque materials. As a result,
if desired, radiopaque material can be positioned at a defined
location or at select, spaced apart locations along passageway 140
to form one or more defined markers under X-ray.
[0083] Based on the foregoing, it is appreciated that inventive
screw portion 102 can be comprised of a radiolucent shaft 108 with
a radiopaque core 112; a radiolucent shaft 108 with a radiolucent
core 112; and/or a radiolucent shaft 108 with a core 112 having
both radiolucent and radiopaque sections. Other material
combinations can also be used. In combination with each of the
above three alternative designs, it is appreciated that radiopaque
markers can be formed on or along the radiolucent shaft 108. Such
markers can further aid the surgeon in the implantation and
positioning of screw portion 102.
[0084] One example of a radiopaque marker is an encircling marker
disposed within or on shaft 108 such that the marker is spaced
apart or is disposed directly against core 112. For example, FIG.
10 shows an embodiment of a screw portion 102 in which a
biocompatible positioning marker 147A is embedded within shaft 108
between proximal end 114 and distal end 116. In the depicted
embodiment, positioning marker 147A can comprise a ring that
completely encircles passageway 140 or a partial ring that
partially encircles passageway 140. In other embodiments,
positioning marker 147A can be linear or any other desired shape.
Each positioning marker 147A can be positioned so as to be exposed
on the exterior surface of shaft 108 (such as positioning marker
147A), completely embedded within shaft 108 (such as positioning
marker 147B), positioned against core 112 (such as positioning
marker 147C), or can extend between core 112 and the exterior
surface of shaft 108. Furthermore, a positioning marker 147D, such
as in the form of a ring or other structure, can be disposed on the
exterior surface 122 of shaft 108. This can be accomplished by
welding, crimping, adhering, or otherwise securing positioning
marker 147D on exterior surface 122. Other configurations and
placement of positioning markers 147 can also be used. For example,
a positioning marker can form a helix that spirals in one or more
partial or complete revolutions about passageway 140 or can form a
linear strand that extends along the length of shaft 108.
[0085] Positioning markers 147 are comprised of a radiopaque
material so as to be viewable on an X-ray photograph. As such,
positioning markers 147 can be comprised of the same types of
radiopaque materials discussed above with regard to head 110.
During implantation and positioning of screw portion 102, the X-ray
image of positioning markers 147 can help the physician determine
the position and orientation of screw portion 102.
[0086] In one embodiment, a positioning marker 147 is positioned
about midway between proximal end 114 and distal end 116 of shaft
108. In other embodiments, a positioning marker 178 is positioned
substantially closer to proximal end 114 or distal end 116 or at
any desired location. In some embodiments, as shown in FIG. 10, it
is appreciated that two or more positioning markers 147 can be
positioned along shaft 108 at spaced apart locations.
[0087] Depicted in FIG. 11 is another embodiment of a positioning
marker 147E. Positioning marker 147E is again comprised of a
radiopaque material but in this embodiment is in the form of paint
or ink that is painted or printed onto exterior surface 122 of
shaft 108. Positioning marker 147E can be used in place of or in
combination with one or more additional positioning markers as
discussed above. Positioning marker 147E can form a continuous ring
that encircles shaft 108 or can be any other type of configuration
such as linear, semi-circular, helical configuration or the like.
For example, positioning marker 147E can be painted on a single
helical revolution of threads 120. Furthermore, a single or two or
more spaced apart positioning markers 147E can be formed along
shaft 108.
[0088] It is appreciated that radiopaque markers can be any desired
shape and be located at any position or orientation that will
produce a desired marking. For example, in other embodiments,
pieces of radiopaque material can be embedded within the shaft
matrix as radiopaque positioning markers. These pieces can comprise
small or large particles that are placed within the shaft matrix
during manufacture either randomly or in a particular pattern. Many
different shapes and patterns can be used for these radiopaque
positioning markers. Also, these pieces of radiopaque material can
be used with or without any of the other types of positioning
markers discussed above.
[0089] Turning to FIG. 12, collar 104 comprises a tubular side wall
220 having an interior surface 222 and an exterior surface 224 that
each extend between a first end 226 and an opposing second end 228.
First end 226 terminates at a terminal end face 230. Interior
surface 222 bounds a longitudinal passage 232 that longitudinally
extends through collar 104. Internal threads 233 are formed on
interior surface 222 at or toward first end 226.
[0090] Side wall 220 is formed having a pair of channels 234 and
236 that are disposed on opposing sides of side wall 220 and that
transversely extend through side wall 220. In the embodiment
depicted, channels 234 and 236 each have a substantially U-shaped
configuration. Each channel 234 and 236 has an open mouth 238 that
extends through end face 230 and an opposing floor 240 that is
rounded. Each channel 234 and 236 is configured so that stabilizing
rod 107 (FIG. 1) can be received therein. In alternative
embodiments, floor 240 need not be rounded but can be flat,
V-shaped, or have other configurations. Each of channels 234 and
236 is also bounded by opposing side surfaces 242 and 244. Although
side surfaces 242 and 244 are shown as being in substantially
parallel alignment, in alternative embodiments side surfaces 242
and 244 can be designed to diverge or converge as they project away
from floor 240. Other configurations can also be used. Channels 234
and 236 form a portion of a transverse passage that transversely
extends through collar 104, as identified by arrow 246 (see FIG.
1).
[0091] As shown in FIG. 12, collar 104 further comprises a shoulder
248 that downwardly and radially inwardly projects from second end
228 of side wall 220. Shoulder 248 terminates at an inside edge 247
that bounds an opening 249. Opening 249 forms part of a
longitudinal passage that also extends through collar 104, as
identified by arrow 232, and that orthogonally intersects with
transverse passage 246 (FIG. 1).
[0092] Shoulder 248 has a tapered interior surface that forms an
annular seat 250. As discussed below in greater detail, bottom
portion 150 of head 110 of screw portion 102 (FIG. 3) rests against
seat 250 so that collar 104 can pivot relative to screw portion
102. In this regard, as depicted in FIG. 13, bottom portion 150 of
head 110 has a maximum diameter larger than opening 249 of collar
104 so that head 110 cannot pass therethrough. It is also noted
that when head 110 is received within opening 249, top surface 160
of head 110 projects slightly above floor 240 of channels 234 and
236 of collar 104. As a result, as discussed further below, when
stabilizing rod 170 (FIG. 1) is received within channels 234 and
236, stabilizing rod 170 biases against top surface 160 of head 110
so as to wedge head 110 within opening 249 and thereby lock screw
portion 102 relative to collar 104.
[0093] As also depicted in FIG. 13, a pin hole 252 transversely
extends through side wall 220 and/or shoulder 248 at second end 228
of side wall 220. Although not required, pin hole 252 is typically
disposed orthogonal to transverse passage 246. As also discussed
below in greater detail, pin hole 252 is adapted to receive a pin
254 which has a first end 256 and an opposing second end 258.
Collar 104 and pin 254 are typically comprised of a radiopaque
material such as those previously discussed with regard to core
112. In alternative embodiments, however, collar 104 and/or pin 254
can be comprised of a radiolucent material, such as those
previously discussed with regard to shaft 108.
[0094] Returning to FIG. 1, fastener 106 comprises a locking screw
270 having an encircling side wall 272 that extends between a top
end face 274 and an opposing bottom end face 276. Optionally,
movably attached to bottom end face 276 of locking screw 270 is an
alignment cap 278 having a substantially U-shaped channel 280
extending transversally therethrough. Channel 280 is bounded by two
side surfaces 286 and 288. Alignment cap 278 is rotatably attached
to locking screw 270 so that as locking screw 270 is rotated,
alignment cap 278 can remain rotationally stationary so as to bias
against rod 107.
[0095] Radially outwardly projecting from side wall 272 of locking
screw 270 so as to encircle locking screw 270 are one or more
helical threads 282. Threads 282 of locking screw 270 are
configured to threadedly engage with internal threads 233 of collar
104 (FIG. 12). Recessed on top surface 274 of locking screw 270 is
a polygonal socket 284 adapted to receive a driver. Accordingly,
once stabilizing rod 107 is disposed within transverse passage 246
of collar 104, locking screw 270 can be screwed into longitudinal
passage 232 of collar 104 so that fastener 106 biases stabilizing
rod 107 against head 110 of screw portion 102. If alignment cap 278
is used, surfaces 286 and 288 of the U-shaped channel 280 bias
against stabilizing rod 107; otherwise bottom end face 276 of
locking screw 270 biases against stabilizing rod 107. In this
configuration, stabilizing rod 107 is secured from unwanted
movement by being compressed between fastener 106 and head 110 of
screw portion 102 and/or between fastener 106 and floor 240 of
channels 234 and 236. Furthermore, as stabilizing rod 107 pushes
against head 110, head 110 is wedged against seat 250 of collar
104, thereby also locking collar 104 relative to screw portion
102.
[0096] Collar 104 and fastener 106 are simply one example of a
collar and fastener that can be used with screw portion 102
described herein. Other collars and associated fasteners can
alternatively be used, such as the collars and fasteners described
in U.S. patent application Ser. No. 11/863,133, filed Sep. 27,
2007, the entirety of which reference is incorporated herein by
specific reference.
[0097] Methods of manufacturing and assembling the screw portion
102 and bone screw 100 will now be discussed. It is appreciated
that while reference is made to screw portion 102 and its
corresponding components, the methods of manufacturing and assembly
given below can also be used with the other embodiments disclosed
herein or otherwise encompassed by the invention. To manufacture
screw portion 102, core 112 is formed from a radiopaque material, a
radiolucent material, or a combination of such materials. Examples
of such materials are discussed above. Core 112 can be formed by
any conventional method known in the art.
[0098] Shaft 108 is then formed about shaft portion 206 of core 112
to produce a blank 292, as shown in FIGS. 14-16. Blank 292 can be
formed in a number of ways. For example, blank 292 can be formed by
winding a fiber and adhesive mixture about core 112 to produce a
fiber and adhesive matrix. For example, in the embodiment depicted
in FIG. 14, a filament winding process is used as is known in the
art. In this process, filaments or fibers 294 are wound under
tension over the shaft portion 206 of core 112. Core 112 rotates
while a carriage (not shown) moves back and forth along the
longitudinal direction of core 112, laying down fibers 294 in a
desired pattern. Fibers 294 are coated with an adhesive as the
fibers 294 are wound about core 112. Many types of biocompatible
fibers and adhesives can be used, as discussed above. If
positioning marker 147 (such as marker 147A-C in FIG. 10) is used,
the positioning marker 147 can be positioned in its desired
location during the filament winding process so that positioning
marker 147 becomes enveloped by the outer layers of fibers 294. The
marker can also be positioned before or after the winding process.
The winding process continues until the diameter of the blank 292
is equal to or greater than the desired diameter of the finished
shaft 108 of screw portion 102. Blank 292 is then allowed to cure
or harden. If required, blank 292 can be placed in an oven during
the curing process.
[0099] In an alternative embodiment, blank 292 is formed using a
roll wrap or table wrap process, as depicted in FIG. 15. In this
process, one or more sheets 296 of fiber are coated with the
adhesive. Many types of biocompatible fibers and adhesives can be
used, as discussed above. If required, the coated sheet or sheets
296 are then allowed to partially cure. Once the desired amount of
partial curing has been obtained, the sheet or sheets 296 are then
wrapped about the shaft portion 206 of core 112 to produce a fiber
and adhesive matrix. Again, if a positioning marker 147 (FIG. 11)
is used, it can be positioned in its desired location during the
wrapping process so that positioning marker 147 becomes enveloped
by the outer layers of sheets 296. That is, multiple different
layers can be wrapped on top of each other. The marker can also be
positioned before or after the wrapping. The wrapping continues
until the diameter of the blank 292 is greater than or equal to the
desired diameter of the finished shaft 108 of screw portion 102.
Blank 292 is then allowed to cure in a similar manner to the
filament winding process, described previously.
[0100] It is also appreciated that non-winding methods can also be
used for forming blank 292 about core 112. For example,
compression, injection, rotational and other molding processes can
be used to mold an adhesive, a fiber/adhesive mixture, or a mixture
of an adhesive and other types of fillers about core 112. In this
embodiment, the fibers can be short or chopped fiber pieces that
are distributed throughout the adhesive. As another alternative,
shaft 108 can be formed about core 112 by a direct or indirect
extrusion process, where the fiber/adhesive matrix or other
adhesive matrix is extruded about core 112. Other known methods can
alternatively be used to form blank 292.
[0101] As the fibers 294 or sheets 296 are only wound around shaft
portion 206 of core 112, the head portion 204 of core 112 remains
open and uncovered, as shown in FIG. 16. To allow for a better bond
between core 112 and the wound fiber and adhesive matrix, the
surface of core 112 can be etched or otherwise abraded before the
fibers 294 or sheets 296 are wound thereon. This can be
accomplished by sand blasting, rubbing with sandpaper, chemical
etching, or other known roughening process, if desired.
[0102] Once the blank 292 has been formed and allowed to cure, a
grinder or other finishing process can be used, if desired, to
smooth out or cut down any sharp edges remaining on the exterior
surface 298 of the blank 292 to form the exterior surface 122 of
shaft 108. Attachment member 126 and helical threads 120 (FIG. 4)
are then formed on the exterior surface 298 of the blank 292 to
further form shaft 108. This can be accomplished by removing a
portion of the exterior surface 298 of the blank 292 by using a
grinder, lathe, or other cutting tool as is known in the art. Other
methods of forming attachment member 126 and threads 120 can
alternatively be used. If positioning marker 147D or 147E is used
(FIGS. 10 and 11), it is positioned or painted on the exterior
surface 122 of shaft 108 after blank 292 has been processed.
[0103] Tapered tip 124 (FIG. 4) can also be formed at the distal
end of the shaft 108, if desired. In one embodiment, tapered tip
124 is formed by removing a portion of the exterior surface 298 of
the blank 292. Any other features, such as those needed for self
tapping, can also be formed if desired.
[0104] In an alternative method of manufacturing stabilizing screw
portion 102, shaft 108 can initially be formed by winding a
radiolucent fiber/adhesive matrix about a removable core. In
contrast to prior embodiments, however, removable core is then slid
out of shaft 108. The remaining passageway 140 can then be
backfilled by injecting a radiolucent material, such as an epoxy or
other adhesive, or a combined radiolucent and radiopaque material
into passageway 140. Alternatively, a radiolucent core can be slid
into the passageway and secured in place by an adhesive or other
method of securing. As a result, the entire shaft and core are
radiolucent. Again, any number or type of radiopaque positioning
marker can be used.
[0105] Turning to FIG. 17, once attachment member 126 and threads
120 have been formed on the shaft 108, head 110, which has been
previously formed, is then attached to the threaded shaft 108. To
do this, bottom surface 156 of head 110 is positioned adjacent head
portion 204 of core 112 so that second passageway 182 of head 110
aligns with core 112. Head 110 is then advanced toward shaft 108 so
that head portion 204 of core 112 is received within second
passageway 182. Head 110 is further advanced along core 112 until
attachment member 126 is received within attachment recess 128.
Head 110 is then rigidly secured to core 112 and to shaft 108 by a
securing method known in the art, such as by adhesive, laser
welding, and/or other known method. For example, in addition to
using an adhesive between head 110 and shaft 108 and between head
110 and core 112, if desired, the exposed end of core 112 can be
directly welded to head 110. Any portion of core 112 that extends
out of second passageway 182 and past top surface 160 of head 110
can be cut off, if desired.
[0106] In an alternative method of manufacturing screw portion 102,
after core 112 has been formed, blank 292 is configured so that
both head portion 204 and shaft portion 206 can be formed
therefrom. Specifically, depicted in FIG. 18, screw portion 102 is
shown as being comprised of a body 290 and core 112 that is
positioned therein. Body 290 comprises shaft 108 and head 110.
However, in contrast to the prior embodiment where head 110 is
attached to shaft 108, in this embodiment shaft 108 and head 110
are integrally formed as a single, unitary structure. That is, both
shaft 108 and head 110 are milled, cut or otherwise formed from a
single blank that is formed about core 112. As such, in this
embodiment the entire body 290 is comprised of a radiolucent
material, such as those previously discussed with regard to shaft
108, while core 112 is typically comprised of a radiopaque material
but can also be comprised of a radiolucent material or combination.
As with other embodiments, the positioning markers 147 (FIGS. 10
and 11) can also be used with body 290.
[0107] In one similar method of manufacture, body 290 can initially
be formed by winding a radiolucent fiber/adhesive matrix about a
removable core as discussed above. The removable core can then be
slid out of body 290. The remaining passageway can then be
backfilled by injecting a radiolucent material such as an epoxy or
other adhesive within the passageway. Alternatively, a radiolucent
or radiopaque core can be slid into the passageway and secured in
place by an adhesive, welding or other method of securing. As a
result, the entire body and core can be radiolucent. Again, to help
facilitate placement, positioning marks 147 (FIGS. 10 and 11) can
be used with the radiolucent body.
[0108] Once screw portion 102 has been manufactured and assembled
as described above, the polyaxial bone screw 100 can be assembled
with screw portion 102 as one of its components. For example,
turning to FIG. 13, to assemble polyaxial bone screw 100, shaft 108
of assembled screw portion 102 is passed down through longitudinal
passage 232 and opening 249 of collar 104. Head 110 of screw
portion 102, however, has a maximum diameter that is greater than
the minimum diameter of opening 249 extending through seat 250 of
collar 104. As such, head 110 of screw portion 102 rests on seat
250 of collar 104 and is prevented from passing through opening
249. As a result of the rounded configuration of bottom portion 150
of head 110 and the tapered sloping of seat 150, head 110 can
freely slide on seat 250 such that screw portion 102 and collar 104
can freely pivot relative to each other.
[0109] Once screw portion 102 is seated within collar 104, pin 254
is advanced into pin hole 252. First end 256 of pin 254 is secured
within pin hole 252 such as by welding, adhesive, press fit, or
other mechanical engagement, such as threaded engagement. In this
position, second end 258 of pin 254 projects into engagement slot
164 of screw portion 102. It is noted that pin 254 is spaced apart
above floor 170 of engagement slot 164. As a result, screw portion
102 and collar 104 can continue to freely pivot relative to each
other. However, because pin 254 extends over floor 170, head 110 is
prevented from passing back up through collar 104. Pin 254 also
functions to couple screw portion 102 and collar 104 together so
that rotation of collar 104 or screw portion 102 also facilitates
rotation of the other of the collar 104 or screw portion 102. As
such, screw portion 102 can be implanted or removed simply by
rotating collar 104. In alternative embodiments, it is appreciated
that pin 62 can come in a variety of different configurations and
can be mounted at a variety of different orientations and
locations. Pin 62 can also be comprised of a radiolucent or
radiopaque material.
[0110] In an alternative embodiment, head 110 is mounted on the
collar 104 using pin 254, as described above, before head 110 is
attached and secured to core 112 and shaft 108.
[0111] Depicted in FIG. 19 is an alternative embodiment of a screw
portion 350 incorporating features of the present invention that
can be used with polyaxial bone screw 100. Like elements between
screw portion 350 and other screw portions described herein are
identified by like reference characters.
[0112] As depicted in FIG. 20 and similar to screw portion 102,
screw portion 350 comprises an elongated shaft 352 having a head
354 disposed thereon with a core 356 extending longitudinally
through shaft 352 and head 354.
[0113] Screw portion 350 is similar to screw portion 102 except for
the attachment structure between shaft 352 and head 354. For
example, instead of attachment member 126 of shaft 108 having a
flat 136 and projecting from an end face 132 of shaft body 113,
attachment member 358 of shaft 352 is simply an extension of shaft
body 113 having the same diameter as shaft body 113. That is,
attachment member 358 projects from shaft body 113 in such a manner
that no end face 132 is formed. In other words, attachment member
358 has an encircling exterior surface 360 that is aligned with
exterior surface 122 of shaft body 113 at proximal end 114.
Exterior surface 360 extends to terminal end face 134.
[0114] Correspondingly, head 354 is similar to head 110 except that
head 354 further comprises a shoulder 362 extending from the outer
perimeter of bottom surface 156. As shown in FIG. 21 in conjunction
with FIG. 20, shoulder 362 comprises an encircling perimeter wall
364 having an inner surface 366 and an opposing outer surface 368
extending from bottom surface 156 to a terminal end face 370. Inner
surface 366 of perimeter wall 364 bounds an attachment recess 372
that is sized and shaped so as to snugly fit over attachment member
358. As such, attachment recess 372 is substantially cylindrical in
shape in the depicted embodiment, having a mouth 373 defined by
terminal end face 370. Because of attachment recess 364, no
attachment recess is necessary within bottom surface 156, although
attachment recess 364 could also extend into bottom surface 156 if
so desired.
[0115] Because of the size and shape of attachment member 358 and
attachment recess 372, the amount of surface area that can be used
for bonding the two together is increased over other embodiments.
This can allow for a stronger bond that can withstand more
torque.
[0116] Similar to head 110, head 354 also includes a second
passageway 374. Second passageway 374 is similar to second
passageway 182 except second passageway 374 has a substantially
circular cross-sectional shape without a straight portion 184.
[0117] Core 356 is similar to core 112, except that head portion
204 remains substantially circular in cross section to match the
shape of second passageway 364. However, any of the cores described
herein or contemplated by the invention can be used with screw
portion 350, and first and second passageways will reflect this.
Furthermore, flats or other surface structures can be formed on
attachment member 358 and inner surface 366 of head 354.
[0118] As with screw portion 102, shaft 352, head 354, and core 356
can respectively be comprised of the same materials as discussed
above regarding shaft 108, head 110, and core 112. Also, screw
portion 350 can be manufactured and assembled similar to that
described above with regard to screw portion 102. One small
difference from assembled screw portion 102 is that, as shown in
FIG. 19, when screw portion 350 is assembled, shoulder 362 extends
slightly further away from the longitudinal axis 118 then exterior
surface 122 as extension 362 fits over attachment member 358.
[0119] Furthermore, it is appreciated that many of the alternative
design features as previously discussed with regard to screw
portion 102 are also applicable to screw portion 350. For example,
to aid in the implantation of screw portion 350, positioning
markers 147 (FIGS. 10 and 11), as previously discussed, can again
be formed on or within shaft 352. Likewise, as with screw portion
102, by forming shaft 352 out of a radiolucent material while core
356 is formed from a radiopaque material, screw portion 350 can be
properly positioned while limiting unwanted obstructions.
Specifically, the thin core 356 can be easily viewed by X-ray to
determine proper positioning of the screw portion 350 but the
larger shaft 352 is radiolucent so as to not obstruct surrounding
structure.
[0120] To increase the bonding strength and ability to transfer
torque, one or more keyed splines and corresponding grooves can be
disposed within attachment recess 372 and attachment member 358.
For example, FIG. 22 shows a spline 378 projecting into attachment
recess 372 from the inner surface 366 of perimeter wall 364. Spline
378 comprises a sidewall 380 that extends longitudinally from a
first end 382 disposed at or near bottom surface 156 to a spaced
apart second end 384 disposed at or near the mouth 373 of the
attachment recess 372.
[0121] Turning to FIG. 23, a corresponding groove 386 is formed in
exterior surface 360 of attachment member 358. Groove 386 is
bounded by a sidewall 388 that extends longitudinally from terminal
end face 134 to a spaced apart end wall 390. Groove 386 is sized
and shaped so as to snugly receive spline 380 when attachment
member 358 is received within attachment recess 372. As shown in
the depicted embodiment, spline 380 is substantially parallel to
longitudinal axis 162 of head 354 and groove 386 is substantially
parallel to longitudinal axis 118 of shaft 352 so as to be aligned
when assembled. Other matching shapes can alternatively be used.
For example, spline 380 and groove 386 can be helical in nature, if
desired. In that case, head 354 would be screwed onto shaft 352
during assembly. Other mating shapes are also possible. For
example, attachment member 358 can be formed with one more flats or
can be formed into a polygonal, oval, irregular or other
non-circular shape. Attachment recess 372 would have a
complementary configuration.
[0122] It is appreciated that more than one spline and groove can
be used in the present invention. For example, in FIG. 24, four
grooves 386a-d are formed in exterior surface 360 of attachment
member 358. Although not shown, it is appreciated that a head 354
incorporating four splines 378 that mate with grooves 386a-d would
correspondingly be used. In the depicted embodiment, the grooves
386a-d are similar to each other and equidistant from each other,
although this is not necessary. Grooves 386 and splines 378 can
alternatively be spaced with respect to each other so as to form a
sort of key. In this manner heads 354 will only attach to certain
shafts 352 in a particular orientation depending on the keyed fit.
Alternatively, one or more of the grooves 386 can be shaped
differently than the other grooves so as to also form a key. Of
course, head 354 will incorporate splines 378 that match the keyed
grooves 386, so as to attach to shaft 352 in the particular
orientation.
[0123] It is appreciated that more or less splines and grooves can
be used with the present invention. For example, screw portion 350
can comprise two or three or more splines and grooves.
[0124] Depicted in FIG. 25 is another alternative embodiment of a
screw portion 420 incorporating features of the present invention
that can be used with polyaxial bone screw 100. Like elements
between screw portion 420 and other screw portions described herein
are identified by like reference characters.
[0125] Screw portion 420 is similar to screw portion 350 (FIG. 20)
except that the shoulder 362 of head 354 includes an extension of
the threads 120 that are formed on the exterior surface 122 of
shaft body 113.
[0126] As shown in FIG. 26, attachment member 358 of shaft 352 is
sized so as to have a smaller diameter than the exterior surface
122 of shaft body 113. As a result, similar to end face 132, an end
face 422 is formed on shaft body 113 between the exterior surface
360 of attachment member 358 and exterior surface 122 of shaft body
113. End face 422 is generally planar and orthogonal to
longitudinal axis 118 of shaft 352, but this is not required.
Attachment member 358 centrally projects from this end face 422 to
terminal end face 134. Because of the smaller diameter of
attachment member 358, shoulder 362 can correspondingly have a
smaller diameter. Again, if desired one or more flats, grooves,
splines, threads, or other structures can be formed on attachment
member 358 with a complementary structure being formed on head
354.
[0127] As shown in FIG. 27, the end face 370 of shoulder 362 of
head 354 is shaped so as to match the shape of end face 422 and
inner surface 366 is dimensioned with a smaller diameter so as to
snugly receive the smaller diameter attachment member 358. Due to
the smaller dimensions, when assembled the outer surface 368 of
shoulder 362 and the exterior surface 122 of shaft body 113 are
aligned, as shown in FIG. 25. Also as shown in FIG. 25, one or more
threads 424 helically encircle and radially outwardly project from
outer surface 368 of shoulder 362. The threads 424 are configured
to align with the threads 120 of shaft body 113 so that as the
screw portion 420 is threaded into the bone, the threads 424 will
also engage the bone.
[0128] Because the threads extend onto the shoulder 362, the shaft
body 113 can be shorter so that the attachment member 358 and the
shoulder 362 can be longer than in screw portion 350, thereby
providing even more surface area for bonding between the head 354
and shaft 352. This results in a stronger bond. Furthermore, the
threads 424 on the shoulder 362 cause a better bone-to-screw
connection when threads 424 are threaded into cortical bone.
[0129] Depicted in FIG. 28 is one embodiment of a fixed bone screw
300 incorporating features of the present invention. In general,
fixed bone screw 300 comprises a collar rigidly secured to or
formed on the end of a threaded shaft so that the collar cannot
pivot relative to the shaft. Like elements between bone screw 300
and the prior discussed embodiments are identified by like
reference characters.
[0130] As depicted in FIG. 29, in one embodiment bone screw 300
comprises shaft 108, core 112, and a collar 302. Core 112 is
secured within first passageway 140 of shaft 108. The previously
discussed materials, configurations, methods of manufacture and
alternatives thereof of shaft 109 and core 112 are also applicable
to bone screw 300.
[0131] As depicted in FIGS. 29 and 30, collar 302 comprises a base
304 that extends from a first end 306 to a floor 308. Base 304 has
an interior surface 309 that bounds an attachment recess 310
extending from floor 308 to a first end face 311 at first end 306.
Attachment recess 310 thus has the configuration of a blind socket.
Interior surface 309 has a substantially circular transverse cross
section with a flat 314 formed thereon. Attachment recess 310 has a
configuration complementarily to and is configured to receive and
secure to attachment member 126 of shaft 108 in the same manner
that attachment member 126 is received and secured within
attachment recess 128 of head 110 (FIG. 6).
[0132] Floor 308 also has an interior surface 316 that bounds a
second passageway 312 that extends through floor 308 so as to
communicate with attachment recess 310. Interior surface 316 also
has a substantially circular transverse cross section with a flat
318 formed thereon.
[0133] Second passageway 312 is positioned so that when attachment
member 126 is secured within attachment recess 310, first
passageway 140 of shaft 108 is aligned with second passageway 312.
It is also appreciated that second passageway 312 is also
configured to receive and secure to head portion 204 of core 112 in
the same manner that head portion 204 is received and secured
within second passageway 182 of head 110 (FIG. 6).
[0134] A pair of spaced apart arms 320 and 321 project from
opposing sides of base 304 in substantially parallel alignment.
Each arm 320 and 321 has an interior surface 322. The opposing
interior surfaces bound a substantially U-shaped channel 323 in
which stabilizing rod 107 (FIG. 1) can be received. Furthermore,
each interior surface 322 has a thread portion 324 formed thereon.
Thread portions 324 enable locking screw 270 (FIG. 1) or an
alternative embodiment thereof to threadedly engage with arms 320
and 321 so as to secure stabilizing rod 107 within channel 323. It
is appreciated that many of the alternative design features as
previously discussed with regard to collar 104 are also applicable
to collar 302. Likewise, collar 302 can be comprised of the same
materials as previously discussed with regard to collar 104.
[0135] To aid in the implantation of bone screw 300, positioning
markers 147 (FIGS. 10 and 11), as previously discussed, can again
be formed on or within shaft 108. Likewise, as with screw portion
102, by forming shaft 108 out of a radiolucent material while core
112 and collar 302 are formed from a radiopaque material, bone
screw 300 can be properly positioned while limiting unwanted
obstructions. Specifically, the thin core 112 can be easily viewed
by X-ray to determine proper positioning of the bone screw but the
larger shaft 108 is radiolucent so as to not obstruct surrounding
structure.
[0136] Depicted in FIG. 31 is an alternative embodiment of bone
screw 300 incorporating features of the present invention wherein
like element are identified by like reference characters. In this
embodiment, bone screw 300 is shown as being comprised of a body
330 and core 112 that is positioned therein. Body 330 comprises
shaft 108 and collar 302. However, in contrast to the prior
embodiment where collar 302 is secured to shaft 108, in this
embodiment shaft 108 and collar 302 are integrally formed as a
single unitary structure. That is, both shaft 108 and collar 302
are milled, cut or otherwise formed from a single blank that is
formed about core 112. As such, in this embodiment the entire body
330 is comprised of a radiolucent material, such as those
previously discussed with regard to shaft 108, while core 112 is
typically comprised of a radiopaque material but can also be
comprised of a radiolucent material. As with other embodiments, one
or more positioning markers 147 (FIGS. 10 and 11) can also be used
with body 330. Furthermore, as discussed in prior embodiments, core
112 can be removed and replaced with an adhesive or an alternative
core.
[0137] Depicted in FIG. 32 is another alternative embodiment of a
spinal stabilizing system 450 wherein like elements are identified
by like reference characters. Stabilizing system 450 includes a
polyaxial bone screw 452 comprising an elongated screw portion 454,
a collar 456 pivotally mounted thereon and a saddle 458 that is
disposed within collar 456. Stabilizing system 450 also includes a
fastener 460 that is selectively engageable with collar 456 to
secure polyaxial bone screw 452 to stabilizing rod 107.
[0138] As depicted in FIG. 33, screw portion 454 of bone screw 452
comprises a shaft 462, an elongated core 464 that extends within
shaft 462, and a head 466 formed on an end of core 464. Shaft 462
is substantially identical to shaft body 113 discussed with regard
to FIGS. 3 and 4 and thus like reference characters reference like
elements. Shaft 462 can be made from the same radiolucent materials
and with the same methods and alternatives as discussed with regard
to shaft body 113. Furthermore, the various markers as discussed
herein can be used in association with shaft 462.
[0139] In contrast to the embodiment shown in FIG. 2 wherein head
110 and core 112 are formed as separate discrete elements, in the
present embodiment head 466 and core are integrally formed as a
single, unitary structure. In other embodiments, head 466 and core
464 can be rigidly fixed together such as by welding, press fit, or
other connection techniques. Core 464 has an exterior surface 468
extending between a proximal end 469 and an opposing distal end
470. Core 464 is secured within passageway 140 of shaft 462 using
the methods previously discussed. In this embodiment, however, a
helical thread 472 is formed on exterior surface 468 and extends
along a length of core 464. Helical thread 472 has a thread
orientation opposite that of thread 120 on shaft 462. As a result,
core 464 further engages shaft 462 when bone screw 452 is being
backed out of a bone, thereby helping to prevent separation between
core 464 and shaft 462. In alternative embodiments, core 464 can
have the other shapes and/or protrusions as discussed with regard
to the other cores herein.
[0140] Head 466 comprises an annular shoulder 474 that extends
between a flat bottom end face 475 and a recessed annular neck 476.
Core 464 extends from bottom end face 475. Upwardly and outwardly
extending from neck 476 is an annular, rounded head portion 477
that terminates a flat top face 478. If desired, texture, such as
micro grooves or other patterns can be formed on the exterior
surface of head portion 477 to facilitate locking between head 466
and collar 456 as discussed below in greater detail. As depicted in
FIG. 34, an engagement socket 480 is recessed on top face 478.
Engagement socket 480 is bounded by an encircling sidewall and
typically has a polygonal or other non-circular transverse cross
section so that a driver can engage with socket 480 for rotating
bone screw 452. As also shown in FIG. 34, core 464 and head 466
each have an interior surface 482 that bounds a cannula 483
extending from engagement socket 480 through distal end 470 of core
464. Again, cannula 483 can be used to receive a guide wire for
implanting bone screw 452 and/or can be used for other surgical
techniques. In other embodiments, cannula 483 can be eliminated.
Head 466 and core 464 can be made from the same radiopaque
materials, such as radiopaque metals, as discussed with regard to
the other heads and cores disclosed herein. During manufacture,
shaft 462 is formed on or otherwise secured to core 464 so that
shaft 462 is disposed against bottom face 475 of head 466.
[0141] Returning to FIG. 32, collar 456 comprises a tubular side
wall 522 having an interior surface 524 and an exterior surface 526
that each extend between a first end 528 and an opposing second end
530. Interior surface 524 bounds a longitudinal passage 532 that
longitudinally extends through collar 456. Internal threads 534 are
formed on interior surface 524 at or toward first end 528.
[0142] Side wall 522 is formed having a pair of channels 536 and
538 that are disposed on opposing sides of side wall 522 and that
transversely extend through side wall 522. In the embodiment
depicted, channels 536 and 538 each have a substantially U-shaped
configuration. Other channel shapes can also be used. Channels 536
and 538 form a portion of a transverse passage that transversely
extends through collar 456 so as to intersect with the longitudinal
passage 532 that also extends through collar 456. Each channel 536
and 538 is configured so that stabilizing rod 107 can be received
therein as stabilizing rod 107 is placed within the transverse
passage.
[0143] As depicted in FIG. 37, collar 456 further comprises a
shoulder 541 that radially inwardly projects from second end 530 of
side wall 522 so as to encircle longitudinal passage 532. Shoulder
541 has a tapered interior surface that forms an annular seat 542.
In alternative embodiments, seat 542 need not completely encircle
passage 532. Seat 542 can also comprise two or more spaced apart
portions.
[0144] During assembly of bone screw 452, shaft 462 is passed down
through longitudinal passage 532 of collar 456. Head 466, however,
has a maximum diameter that is greater than the minimum diameter of
longitudinal passage 132 extending through seat 542 of collar 456.
As such, head 466 rests on seat 542 of collar 456 and is prevented
from passing through collar 456 as shown in FIG. 37. As a result of
the spherical configuration of head 466 and the tapered sloping of
seat 542, head 466 can freely slide on seat 542 such that shaft 462
and collar 456 can freely pivot relative to each other.
[0145] As shown in FIG. 32, fastener 460 can be used to secure
stabilizing rod 107 to bone screw 452. Fastener 460 comprises a
locking screw 600 having an encircling side wall 602 that extends
between a top end face 604 and an opposing bottom end face 606.
Radially outwardly projecting from side wall 602 of locking screw
600 so as to encircle locking screw 600 are one or more helical
threads 608. Threads 608 of locking screw 600 are configured to
threadedly engage with internal threads 534 of collar 456. A socket
610 or other type of engaging member or recess adapted to receive a
driver can be disposed on top surface 604 of locking screw 600.
[0146] Fastener 460 is threaded into threads 534 formed on interior
surface 524 of collar 456 to secure stabilizing rod 107 to bone
screw 452 within channels 536 and 538 of collar 456. That is, once
stabilizing rod 107 is disposed within the transverse passage of
collar 456, locking screw 600 is screwed into collar 456 so that
bottom end face 606 of locking screw 200 presses against
stabilizing rod 107, which in turn causes stabilizing rod 107 to
press against head 466. As a result, head 466 is pressed within
seat 542 of collar 456 which locks screw portion 454 relative to
collar 456.
[0147] Although not required, saddle 458 can be used to provide a
seat for stabilizing rod 107 so as to reduce localized stress
points. More specifically, without saddle 458, stabilizing rod 107
sits directly over engagement socket 480 on head 466 (FIG. 34). The
perimeter edge of engagement socket 480 produces localized stress
points on stabilizing rod 107 which can damage stabilizing rod 107
and/or distort engagement socket 480. Saddle 458 separates
stabilizing rod 107 from the perimeter edge of engagement socket
480 and more uniformly distributes the clamping forces around
stabilizing rod 107. For example, as depicted in FIG. 37, saddle
458 can be positioned between head 466 and stabilizing rod 107 such
that when fastener 460 is threaded into collar 456, stabilizing rod
107 presses against saddle 458, which in turn presses against head
466. Again, as a result, head 466 is pressed within seat 542 of
collar 456 which locks screw portion 454 relative to collar
456.
[0148] To be able to retain saddle 458 within passage 532 in a
particular positioning arrangement, collar 456 can also include one
or more channels or lips. For example, the embodiment depicted in
FIG. 32 includes collar 456 having a channel 548 formed on interior
surface 524. Channel 548 is generally aligned with longitudinal
passage 532 and is designed to receive a key formed on saddle 458,
as discussed in more detail below. Furthermore, collar 456 can also
includes an inwardly projecting annular lip 618 formed on interior
surface 524 that at least partially encircles longitudinal passage
532. Lip 618 is sized so as to have a slightly smaller diameter
than the general diameter of interior surface 524.
[0149] Turning to FIGS. 35A and 35B, saddle 458 has a top surface
622 and an opposing bottom surface 624 with an encircling outer
side wall 626 extending therebetween. An internal side wall 628
also extends between top and bottom surfaces 622 and 624 so as to
bound a central opening 630 that extends all the way through saddle
458. Opening 630 is generally circular and is sized so as to allow
a driver tool to access the socket 480 on the head 466 (FIG. 37)
when saddle 458 is disposed against head 466. The opening 630
causes saddle 458 to be generally ring shaped when viewed from a
direction generally normal to the top and bottom surfaces 622 and
624.
[0150] A substantially U-shaped channel 632 is formed on top
surface 622 that extends transversally through saddle 458 so as to
intersect the opening 630. Channel 632 is bounded by a curved side
surface 634 sized so as to snugly receive stabilizing rod 107. As
discussed in more detail below, when locking screw 600 is screwed
into collar 456 (see FIG. 37), surface 634 of the U-shaped channel
632 presses against stabilizing rod 107. Although depicted as being
substantially smooth, the channel surface 634 can be textured for
improved gripping. Examples of the types of texture that can be
used on channel surface 634 include: ribs, grooves, a waffle
pattern, and an abrasive pattern. Other types of textures can also
be used. See, e.g., the waffle-like texture shown in FIG. 38.
[0151] A generally concave cavity 636 is formed on bottom surface
624 of saddle 458 so as to encircle opening 630. Cavity 636 is
bounded by an annular curved side surface 638 sized so as to snugly
receive head 466 (see FIG. 37). As such, when locking screw 600 is
screwed into collar 456, side surface 638 presses against head 466.
As noted above, however, opening 630 in saddle 458 still allows
access to socket 480 of head 466 when saddle 458 presses against
head 466.
[0152] Saddle 458 has an outside diameter that is generally the
same as the inner diameter of longitudinal passage 532 extending
through collar 456. In some embodiments, a slit is formed in saddle
458 to allow saddle 458 to be able to be flexed for insertion into
collar 456. For example, as shown in the depicted embodiment, a
slit 640 is formed in saddle 458 that extends all the way between
top and bottom surfaces 622 and 624 and between outer and internal
side walls 626 and 628.
[0153] Slit 240 is bounded by side surfaces 642 and 644 that face
each other across the slit 640. The slit 640 causes the saddle 620
to be generally "C" shaped, with the slit 640 being the mouth of
the "C." As a result of the slit 640, the portions of saddle 458 on
either side of slit 640 can be flexed toward each other, causing
the diameter of saddle 458 to slightly decrease, thereby allowing
saddle 458 to be inserted into longitudinal passage 132 of collar
456 and past lip 618 during assembly (see FIG. 37). Once positioned
therein, the saddle 458 resiliently springs back to its original
diameter and is retained within the passage 532 by the lip 618,
which has a diameter that is slightly less then that of saddle
458.
[0154] To help keep saddle 458 oriented in a desired position
within collar 456, a key 646 is also positioned thereon. Key 646
comprises a spline projecting out from outer side wall 626 and
extending generally orthogonally between top and bottom surfaces
622 and 624. In the depicted embodiment, key 646 is positioned on
the opposite side of saddle 458 as slit 640, although this is not
required; key 646 can be positioned anywhere along the outer side
wall 626. As noted above, key 646 is designed to fit within
corresponding channel 648 formed on interior surface 524 of collar
456 (see FIG. 32). Other types of keys can alternatively be used,
or, if desired, saddle 458 can be formed without a key. In some
alternative embodiments the key 646 outwardly projects from the
interior surface 524 of collar 456 and the corresponding channel
648 is formed on the outer side wall 626 of saddle 458. Saddle 458
is typically comprised of a radiopaque material such as those
previously discussed with regard to head 110. However, other high
strength, biocompatible materials can also be used.
[0155] Returning to FIG. 32, fastener 460 can also include an
alignment cap 650 movably attached to bottom end face 606 of
locking screw 600 to further distribute the clamping forces around
stabilizing rod 107. More specifically, as shown in FIG. 36,
alignment cap 650 has a generally planar, circular top surface 652
with an encircling perimeter sidewall 654 extending downward
therefrom. A post 656 extends upward from the center of top surface
652. Post 656 is designed to fit within a corresponding hole 658 on
bottom end face 606 of locking screw 600. Alternatively, post 656
can be positioned on locking screw 600 and hole 658 can be formed
on alignment cap 650
[0156] Similar to saddle 458, alignment cap 650 has a substantially
U-shaped channel 662 extending transversally therethrough. Channel
662 is bounded by a curved side surface 664 sized so as to snugly
receive stabilizing rod 107. Alignment cap 650 is rotatably
attached to locking screw 600 by inserting post 656 into hole 658
so that as locking screw 600 is rotated, alignment cap 650 can
remain rotationally stationary so as to press against stabilizing
rod 107. Once inserted through hole 658, the end of post 656 can be
splayed or otherwise spread apart so as to prevent the post 656
from being pulled back through hole 658, while still allowing
locking screw 600 to rotate with respect to alignment cap 650. When
locking screw 600 is screwed into collar 456, surface 664 of the
U-shaped channel 662 presses against stabilizing rod 107. Similar
to channel surface 634 of saddle 458, the channel surface 664 of
alignment cap 650 can be substantially smooth or textured for
improved gripping. Examples of some of the types of textures that
can be used on channel surface 664 are as listed above regarding
saddle 458.
[0157] Alignment cap 650 can be comprised of the same type of
materials discussed above regarding saddle 458. Furthermore,
alignment cap 650 can be comprised of the same material as saddle
458 or a different material.
[0158] FIG. 37 shows how the saddle 458 and alignment cap 650
combine to secure stabilizing rod 107 within collar 456. As
discussed above, when locking screw 600 is screwed into collar 456
while stabilizing rod 107 is disposed within channels 536 and 538
(FIG. 32), surface 664 of alignment cap 650 presses against
stabilizing rod 107. This pressure causes stabilizing rod 107 to,
in turn, press against surface 634 of saddle 458, which causes
surface 638 of saddle 458 to press against head 466. As a result,
stabilizing rod 107 is rigidly attached to bone screw 452 while the
clamping forces are distributed around stabilizing rod 107 by
saddle 458 and alignment cap 650.
[0159] As can be appreciated, saddle 458 and alignment cap 650 can
be used together, as shown in FIG. 37 or separately. That is,
saddle 458 and alignment cap 650 are not reliant on each other and
thus can be used with or without the other, as desired.
Furthermore, the surfaces 634, 654, and 656 of channels 632 and 648
can be textured the same or have different textures from each
other. Alternatively, a texture may be used on only one or more of
the surfaces or, of course, all of the surfaces can be free of any
texturing.
[0160] FIG. 38 shows an alternative embodiment of a saddle 670 that
can be used in the current invention. Saddle 670 is similar to
saddle 458, except that there is no opening or slit extending
through the saddle. Instead, a closed end cavity 636 is formed on
bottom surface 624 that is configured to receive head 466 (FIG.
37). Saddle 670 also includes a waffle-like texture 672 on side
surface 634. Of course, as discussed above, other types of textures
can also be used.
[0161] Depicted in FIG. 39 is another alternative embodiment of a
screw portion 680 that can be used as part of a polyaxial bone
screw. Screw portion 680 is similar to screw portion 102 shown in
FIG. 2 and thus like elements are identified by like reference
characters. Screw portion 680 includes shaft 108 and head 110 as
previously discussed. However, in contrast to core 112, screw
portion 680 includes a core 682. Core 682 comprises an elongated
solid, inner core 684 in the form of a pin. Inner core 684 can have
substantially the same configuration as core 112 previously
discussed but can be made of a radiolucent material, such as those
previously discussed with regard to shaft 108 or can be made of a
radiopaque material, such as those previously discussed with regard
to head 110.
[0162] Core 682 also includes an outer core that extends over at
least a portion of inner core 684. In one embodiment an elongated,
tubular outer core 686A is provided. Outer core 686A is comprised
of a metal wire or ribbon that is coiled into the tubular
configuration so as to bound a passage 688A longitudinally
extending therethrough. The material for outer core 686A is
selected so that outer core 686A is resiliently flexible like a
coiled spring. For example, in one embodiment the wire or ribbon of
outer core 686A is comprised of Nitinol and is heat treated when in
the coiled configuration so that it obtains a coiled memory. Other
metals can also be used. The wire or ribbon can be coiled directly
around inner core 684 or can be separately coiled and then placed
over inner core 684. Alternatively, an elongated, tubular outer
core 686B can positioned over inner core 684. Outer core 686B
comprises a solid tubular sleeve that bound a passage 688B
longitudinally extending therethrough. Outer cores 686A and B can
be comprised of a radiolucent material such as the radiolucent
metals previously discussed with regard to head 110. It is
appreciated that inner core 684 can be fabricated and then the
outer core secured thereto. Alternatively, the outer core can first
be formed and then inner core 684 can be formed by back filling,
such as by injection, a material into the passage extending through
inner core 684.
[0163] Outer cores 686A and B can be secured to inner core 684 by
an epoxy, other adhesives or by other fastening techniques. Outer
cores 686A and B can cover all or substantially all of inner core
684 so that the outer core is received within and is secured to
head 110. Alternatively, the outer core can be sized to cover only
a portion inner core 684. For example, the outer core can be sized
to cover the portion of the inner core 684 within shaft 108 but not
cover the portion of inner core 684 within head 110. To that end,
the outer core can cover not more than 75% and more commonly not
more than 85% of the length of inner core 684. It is appreciated
that the physical properties of the bone screw can be adjusted by
forming the core from different materials and elements.
[0164] Depicted in FIG. 40 is another alternative embodiment of a
screw portion 690 that can be used as part of a polyaxial bone
screw. Screw portion 690 is similar to screw portion 680 except
that inner core 682 has been eliminated. Thus, screw portion 690
comprises a core which is either outer core 686A or outer core 686B
as discussed above. The cores are secured to shaft 108 and head 110
in the same manner that core 112 is secured to these elements as
previously discussed. By having the core formed from a coiled
and/or tubular member, flexible properties of the bone screw can be
adjusted.
[0165] The bone screws previously disclosed herein have primarily
been designed as polyaxial or fixed bone screws for use with spinal
stabilization systems. It is appreciated, however, that the bone
screws of the present invention need not be designed as a polyaxial
or fixed bone screw for use with spinal stabilization systems but
can be configured like any number of conventional bone screws that
are used for applications such as securing bone plates over a
facture, attaching cranial plates, securing joint or other implants
to bone, fixing ligaments and other soft tissue to bone, and the
like.
[0166] By way of example and not by limitation, depicted in FIG. 41
is an exploded bone screw 700 incorporating features of the present
invention wherein like elements are identified by like reference
characters. Bone screw 700 comprises shaft 108, core 112 and a head
702. Head 702 is configured similar to a conventional screw head.
Specifically, head 702 has a side wall 703 that extends between a
proximal end 704 and an opposing distal end 706. Distal end 706
terminates at a bottom end face on which attachment recess 128
(FIG. 6) is formed. Attachment recess 128 permits head 702 to
engage with attachment member 126 of shaft 108 in the manner
previously discussed.
[0167] Side wall 703 flares outwardly as it extends from distal end
706 to proximal end 704. Proximal end 706 terminates at a
substantially flat top end face 708. In one embodiment of the
present invention, means are provided for engaging a driver to the
inventive bone screws. The drivers can then be used for rotating
the bone screws for implanting of the bone screws. By way of
example and not by limitation, an engagement socket 710 is formed
on top end face 708. Engagement socket 710 can be of any desired
configuration such as polygonal, irregular or other non-circular
configuration that permits a driver to engage engagement socket 710
for rotating bone screw 700. Engagement socket 710 can also be in
the form of one or more slots such as are commonly used for
engaging a driver such as a screw driver. In other embodiments, the
means for engaging a driver can comprise top portion 152 as shown
in FIG. 3 or other forms of projections to which a driver having a
complementary socket can engage. Other locking structures commonly
used for engaging a driver can also be used. It is appreciated that
each of the different bone screws as disclosed herein can include
such means for engaging a driver.
[0168] Second passageway 183 (FIG. 6) can be formed on the floor of
attachment recess 128 and extend to or toward engagement socket
710. Second passageway 183 permits head 702 to engage with core 112
in the manner previously discussed. It is appreciated that the
alternative materials, methods of manufacture, use of markers and
other alternatives as previously discussed with regard to the
shaft, core and head of screw portion 102 are also applicable to
the shaft, core and head of bone screw 700.
[0169] It is appreciated that head 702 can have a variety of
different configurations and that it can be integrally formed with
the core. By way of example, depicted in FIG. 42 is an exploded
view of a bone screw 720 incorporating features of the present
invention wherein like elements are identified by like reference
characters. Similar to screw portion 454 shown in FIG. 33, bone
screw 700 comprises shaft 462, core 464 and a head 722. Core 464
and head 722 are integrally formed as a single, unitary structure
or can be rigidly fixed together such as by welding, press fit or
other securing techniques. Head 722 comprises a cylindrical stem
724 that terminates at a bottom end face 726. Bottom end face 726
is designed to position against top end face 132 of shaft 462.
Formed on the opposing end of stem 724 is a substantially
semi-spherical head portion 728. Head portion 728 has a flat bottom
surface that radially outwardly projects from stem 724 and has a
top crown on which engagement socket 710 is formed. Again,
engagement socket 710 can also be in the form of one or more slots
for engaging a driver such as a screw driver. It is appreciated
that the alternative materials, methods of manufacture, use of
markers and other alternatives as previously discussed with regard
to the shaft, core and head of screw portion 454 are also
applicable to the shaft, core and head of bone screw 720.
[0170] In many of the foregoing embodiments, it is discussed that
the core can be comprised of a radiopaque material while the shaft
is comprised of a radiolucent material. In each of the embodiments,
however, it is also appreciated that that both the core and the
shaft can be comprised of a radiolucent material. For example, in
each of the embodiments, the core can be comprised of a ceramic or
rigid thermoplastic that may include fibers or other fillers while
the shaft is comprised of an epoxy fiber matrix. Thus, in some
embodiments, the core and the shaft can be comprised of different
radiolucent materials. In still other embodiments, the core and
shaft can be made of the same radiolucent material. In each
embodiment, however, the various makers discussed herein can be
used with the core and/or shaft.
[0171] A number of different methods and embodiments are disclosed
herein. It is appreciated that the different methods and components
from the different embodiments can be mixed and matched to produce
a variety of still other different embodiments.
[0172] The present invention may be embodied in other specific
forms without departing from its spirit or essential
characteristics. The described embodiments are to be considered in
all respects only as illustrative and not restrictive. The scope of
the invention is, therefore, indicated by the appended claims
rather than by the foregoing description. All changes which come
within the meaning and range of equivalency of the claims are to be
embraced within their scope.
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