U.S. patent application number 13/317504 was filed with the patent office on 2012-02-09 for dynamic stabilization medical implant assemblies and methods.
Invention is credited to Roger P. Jackson.
Application Number | 20120035663 13/317504 |
Document ID | / |
Family ID | 37906483 |
Filed Date | 2012-02-09 |
United States Patent
Application |
20120035663 |
Kind Code |
A1 |
Jackson; Roger P. |
February 9, 2012 |
Dynamic stabilization medical implant assemblies and methods
Abstract
Bone screw assemblies include longitudinal connecting members
that provide for dynamic stabilization, some including non-uniform
portions that are configured to flex, contract or expand. Composite
longitudinal connecting members include longitudinal segments made
from different materials having different flexibilities. Polyaxial
bone screw assemblies include change-out receivers for cooperating
with replacement longitudinal connecting members having a different
flexibility. Bone screw shanks for cooperating with one or more
open receivers include treatment or coating to provide biologically
active interface with bone.
Inventors: |
Jackson; Roger P.; (Prairie
Village, KS) |
Family ID: |
37906483 |
Appl. No.: |
13/317504 |
Filed: |
October 19, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11509386 |
Aug 24, 2006 |
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13317504 |
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10958743 |
Oct 5, 2004 |
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11509386 |
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10409935 |
Apr 9, 2003 |
6964666 |
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10958743 |
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10818555 |
Apr 5, 2004 |
8052724 |
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10409935 |
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10464633 |
Jun 18, 2003 |
6716214 |
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10818555 |
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10996349 |
Nov 23, 2004 |
7621918 |
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10464633 |
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60722300 |
Sep 30, 2005 |
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Current U.S.
Class: |
606/266 ;
606/308 |
Current CPC
Class: |
A61B 17/7037 20130101;
A61F 2/0077 20130101; A61B 17/8625 20130101; A61B 17/7004 20130101;
A61B 17/7091 20130101; A61B 17/7031 20130101; A61B 17/7005
20130101; A61B 2090/037 20160201; A61B 17/7032 20130101; A61B
17/7082 20130101; A61B 17/7026 20130101 |
Class at
Publication: |
606/266 ;
606/308 |
International
Class: |
A61B 17/86 20060101
A61B017/86; A61B 17/70 20060101 A61B017/70 |
Claims
1. A bone screw comprising: a) a shank including a threaded lower
portion adapted to be screwed into a bone and an upper portion with
a capture structure and a central upwardly projecting domed
structure; b) a retaining structure including a partially spherical
outer surface; the retainer structure being releasably matable with
the capture structure of the shank upper portion; and c) first and
second interchangeable receivers; each of the receivers having a
rod-receiving channel wherein the rod-receiving channels are shaped
to receive rods having different widths; the shank being received
in the receiver and then held in the receiver by the retainer.
2. The bone screw according to claim 1, in combination with at
least a first rod sized to be received in the rod-receiving channel
of the first receiver.
3. The bone screw according to claim 2, in combination with at
least a second rod sized to be received in the rod-receiving
channel of the second receiver.
4. The bone screw according to claim 1, including: a) a third
interchangeable receiver with a rod-receiving channel shaped to
receive a rod having a width different from the widths of the rods
associated with the first and second interchangeable receivers.
5. The bone screw according to claim 1, each of the receivers
including: a) an inner cavity with a partially spherical inner
surface cooperatively slidingly mateable with the outer surface of
the retaining structure, so as to allow for a wide range of pivotal
movement between the shank and the receiver; wherein b) when the
retaining structure is releasably mated with the capture structure
of the shank upper portion, the domed structure extends into the
rod-receiving channel so as to receive direct downward force from
the rod received in the rod-receiving channel during locking of a
position of the shank relative to the receiver.
6. The bone screw according to claim 1, wherein: a) the shank domed
structure includes an engagement surface on the top thereof.
7. The bone screw according to claim 1 wherein: a) the shank domed
structure includes a tool receiving surface adapted to receive a
tool for rotating the shank into a bone.
8. The bone screw according to claim 7, in combination with at
least a first rod sized to be received in the rod-receiving channel
of the first receiver and a closure threadedly receivable in the
first receiver so as to block the rod-receiving channel and apply
downward force against the rod when locking the position of the rod
relative to the receiver.
9. A bone anchor assembly comprising: a) a shank including a
threaded lower portion adapted to be screwed into a bone and an
upper portion with a spline capture structure and a central
upwardly projecting domed structure; b) a retaining structure
including a partially spherical outer surface and a spline engaging
structure releasably fixedly mateable with the spline capture
structure; and c) a plurality of interchangeable receivers, each of
the receivers including i) an upper channel adapted to receive one
of a plurality of rods differing from each other in at least one of
structure, fabrication material, flexibility and elasticity, and
ii) an inner cavity with a partially spherical inner surface
cooperatively slidingly mateable with the retaining structure outer
surface so as to allow for a wide range of pivotal movement between
the shank and the receiver; wherein d) when the spline engaging
structure is releasably mated with the spline capture structure,
the domed structure extends into the upper channel so as to receive
a direct downward force from the rod in the channel during locking
of a position of the shank relative to the receiver.
10. The assembly according to claim 9, including a plurality of
rods differing from each other in at least one of structure,
fabrication material, flexibility and elasticity.
11. A bone screw comprising: a) a shank including a threaded lower
portion adapted to be screwed into a bone and an upper portion with
a capture structure; and b) at least two interchangeable receivers
adapted to receive and capture the shank upper portion capture
structure, each of the receivers having a rod-receiving channel,
wherein each of the channels is shaped to receive a rod having a
different width.
12. A bone screw according to claim 11, wherein: a) the shank upper
portion capture structure is a helical guide and advancement
structure adapted to cooperatively engage a complementary receiver
guide and advancement structure such that the shank upper portion
is rotatably received within the receiver.
13. A bone screw according to claim 11, further comprising: a) a
retaining structure adapted to cooperatively mate with the shank
upper portion capture structure within the receiver.
14. A bone screw according to claim 13, wherein: a) the shank upper
portion capture structure includes at least one spline capture
structure; and b) the retaining structure includes a mating
spline-engaging recess.
15. A bone screw comprising: a) a shank including a threaded lower
portion adapted to be screwed into a bone and an upper portion with
a capture structure; b) a retaining structure releasably matable
with the capture structure of the shank upper portion; and c) first
and second interchangeable receivers; each of the receivers having
a rod-receiving channel wherein the rod-receiving channels are
shaped to received rods having different widths; the shank being
received in the receiver and then held in the receiver by the
retainer.
16. A bone anchor assembly comprising: a) a shank including a
threaded lower portion adapted to be screwed into a bone and an
upper portion with a spline capture structure and a central
upwardly projecting domed structure; b) a retaining structure
including a partially spherical outer surface and a spline engaging
structure releasably fixedly mateable with the spline capture
structure; and c) a plurality of interchangeable receivers, each of
the receivers including i) an upper channel adapted to receive one
of a plurality of rods differing from each other in at least one of
structure, fabrication material, flexibility and elasticity, and
ii) an inner cavity with a partially spherical inner surface
cooperatively slidingly mateable with the retaining structure outer
surface so as to allow for a wide range of pivotal movement between
the shank and the receiver; wherein d) when the spline engaging
structure is releasably mated with the spline capture structure,
the domed structure is positioned so as to receive a direct
downward force from above during locking of a position of the shank
relative to the receiver.
17. A bone screw comprising: a) a shank including a lower portion
adapted to be screwed into a bone and an upper capture structure
having a first threaded portion; and b) first and second
interchangeable receivers; each of the receivers having a
rod-receiving channel wherein the rod-receiving channels are shaped
to receive rods having different widths; the shank being received
in the receiver through a second threaded receiver lower opening.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 11/509,386, filed Aug. 24, 2006 which claimed the benefit of
U.S. Provisional Application No. 60/722,300 filed Sep. 30, 2005,
both of which are incorporated by reference herein. This
application is also a continuation-in-part of U.S. patent
application Ser. No. 10/958,743 filed Oct. 5, 2004, which is a
continuation-in-part of U.S. patent application, Ser. No.
10/409,935 filed Apr. 9, 2003, now U.S. Pat. No. 6,964,666, both of
which are incorporated by reference herein. This application is
also a continuation-in-part of U.S. patent application Ser. No.
10/818,555, filed Apr. 5, 2004, which is a continuation of U.S.
patent application Ser. No. 10/464,633 filed Jun. 18, 2003, now
U.S. Pat. No. 6,716,214, both of which are incorporated by
reference herein. This application is also a continuation-in-part
of U.S. patent application Ser. No. 10/996,349 filed Nov. 23, 2004,
which is incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to apparatuses and methods for
use in performing spinal surgery and, in particular, to structural
members for use in spinal surgery including dynamic stabilization
longitudinal connecting members and cooperating polyaxial bone
screw assemblies providing protected motion in a non-fusion
procedure. Certain flexible elongate connecting members or rods
used in methods according to the invention have a substantially
uniform shape, while other longitudinal connecting members
according to the invention have flexible non-uniform portions with
varied cross-section that preserve spinal motion, providing for
flexure and/or compression and extension, in a dynamic
stabilization method and structure. Bone screws according to the
invention have a receiver for capturing and clamping a longitudinal
connecting member that can swivel about a shank of the bone screw,
allowing the receiver to be positioned in any of a number of
angular configurations relative to the shank. Receivers according
to the invention also include a change out feature, allowing for
removal of a flexible longitudinal connecting member and
cooperating receiver without removing the threaded shank that has
been implanted into bone, and then replacing the receiver with a
second receiver for accommodating a more rigid longitudinal
connecting member of a different size.
[0003] Many spinal surgery procedures require securing various
implants to bone and especially to vertebrae along the spine. For
example, elongate longitudinal connecting members are often
required that extend along a portion of the spine to provide
support to vertebrae that have been damaged or weakened due to
injury, disease or the like. Such longitudinal connecting members
must be supported by certain vertebra and support other vertebra.
The most common mechanism for providing such structure is to
implant bone screws into certain bones which then in turn support
the longitudinal connecting member or are supported by the
longitudinal connecting member. Bone screws typically have a shank
that is threaded and adapted to be implanted into a vertebral body
of a vertebrae. Such bone screws also include a receiver designed
to extend beyond the vertebrae and include a channel for receiving
a longitudinal connecting member or other elongate member. The
receiver may be open, swiveling with respect to the shank,
providing ease in placement of the longitudinal connecting member
within the receiver channel prior to clamping of the longitudinal
connecting member within the channel and locking the longitudinal
connecting member with respect to the receiver and the shank in a
particular desired angle with respect to the shank, utilizing a
closure member that also is inserted in the receiver channel.
[0004] Historically, it has been common to fuse adjacent vertebrae
that are placed in fixed relation by the installation therealong of
bone screws or other bone anchors and cooperating longitudinal
connecting members or other elongate members. Fusion results in the
permanent immobilization of one or more of the intervertebral
joints. Because the anchoring of bone screws, hooks and other types
of anchors directly to a vertebra can result in significant forces
being placed on the vertebra, and such forces may ultimately result
in the loosening of the bone screw or other anchor from the
vertebra, fusion allows for the growth and development of a bone
counterpart to the longitudinal connecting member that can maintain
the spine in the desired position even if the implants ultimately
fail or are removed. Because fusion has been a desired component of
spinal stabilization procedures, longitudinal connecting members
have been designed that are of a material, size and shape to
largely resist flexure, extension and compression, and thus
substantially immobilize the portion of the spine that is to be
fused. Thus, longitudinal connecting members are typically uniform
along an entire length thereof, and usually made from a single or
integral piece of material having a uniform diameter of a size to
provide substantially rigid support.
[0005] Fusion, however, has some undesirable side effects. One
apparent side effect is the immobilization of a portion of the
spine. Furthermore, although fusion may result in a strengthened
portion of the spine, it also has been linked to more rapid
degeneration and even hyper mobility of spinal motion segments that
are adjacent to the portion of the spine being fused, reducing or
eliminating the ability of such spinal joints to move in a more
normal relation to one another. In certain instances, fusion has
also failed to provide pain relief.
[0006] An alternative to fusion and the use of rigid longitudinal
connecting members or other rigid structure has been a "soft"
stabilization approach in which a flexible C- or U-shaped member or
coil is utilized as a spring member fixed between a pair of pedicle
screws in an attempt to create, as much as possible, a normal
loading pattern between the vertebrae, both in flexion and
extension. Such devices allow for some natural movement or flex.
However, such devices may be undesirable as they extend upwardly
and outwardly from the bone screw or anchor, creating an implant
with a profile much larger than those using a traditional
cylindrical longitudinal connecting member. Larger profile implants
are almost always undesirable for placement in a human body and may
limit the working space afforded to the surgeon during an implant
procedure.
[0007] Another concern that arises when more flexible structure is
utilized in a spinal medical implant is that of adequate fatigue
strength or endurance limit. The concept of strength may be defined
as the highest stress a material can withstand before it completely
fails to perform structurally. Typically, the concept of strength
takes into account the influence of a force upon a cross-sectional
area of a material that ultimately causes a material to fail.
Specifically, fatigue strength has been defined as the repeated
loading and unloading of a specific stress on a material structure
until it fails. Fatigue strength can be tensile, compression,
shear, bending, or a combination of these. The dynamic conditions
associated with spinal movement therefore provide quite a challenge
for the design of elongate structural members that exhibit an
adequate fatigue strength to provide stabilization and protected
motion of the spine, without fusion, and allow for some natural
movement of the portion of the spine being reinforced by the
elongate structural member.
SUMMARY OF THE INVENTION
[0008] Dynamic medical implant assemblies and methods according to
the invention include various longitudinal connecting members. One
such member has first, second and third integral and substantially
coaxial portions. The first and second portions are substantially
uniform and are sized and shaped to be receivable in an open
receiver of a bone attachment structure. The third portion is
non-uniform and is disposed between the first and second portions.
In one embodiment, the third portion includes first and second
substantially parallel axially spaced sides and a plurality of
curved strips, each curved strip being integral with both the first
side and the second side at either end thereof. The third,
non-uniform portion therefore being both compressible and
expandable in an axial direction. The third portion is hollow and
appears substantially spheroidal when in an extended
orientation.
[0009] Another longitudinal connecting member of the invention
includes first, second and third integral portions, the first
portion being substantially uniform and having a first diameter,
the second portion being substantially uniform and having a second
diameter and the third portion being solid and disposed between the
first and second portions. The first and second portions are
illustrated herein as being cylindrical in form with equal
diameters. The third portion has a first width defined by a first
longitudinal cross-section and a second width defined by a second
cross-section disposed perpendicular to the first longitudinal
cross-section. In the illustrated embodiments, the first width of
the non-uniform portion is larger than the diameters of the first
and second portions and the second width is smaller than the
diameters of the first and second portions.
[0010] A further longitudinal connecting member according to the
invention has a substantially uniform cross section, but is divided
longitudinally into at least first and second segments wherein the
first segment is substantially more flexible in comparison to the
second section. Each section may be sized and shaped to be received
by at least a pair of bone anchors, allowing for dynamic
stabilization along one portion of the spine and rigid
stabilization along a second portion of the spine by a single
longitudinal connecting member. Such longitudinal connecting
members may have at least a portion of the first segment being
constructed of material different from the second segment. Stitch
longitudinal connecting members may include first and second
segments that are both made from a solid material.
[0011] Dynamic medical implant assemblies according to the
invention that provide dynamic, protected motion of the spine
further include bone anchors, such as polyaxial bone screw
assemblies, that may include bone screw shanks that are treated to
provide for a roughened or textured surface, such as by plasma
cleaning or coating. Furthermore, such treatment may include
coating with a material such as hydroxyapatite. Such treatments and
coatings provide for bone bonding and in certain cases a bioactive
interface between the bone attachment structure and the
vertebra.
[0012] Further apparatus and methods according to the invention
include providing a first assembly for use with a flexible
longitudinal connecting member or a longitudinal connecting member
with flexible portions, and also providing replacement receivers
for receiving longitudinal connecting members of different
diameters, for example, for implanting at a later time when a more
rigid assembly may be required. Specifically, polyaxial bone screw
assemblies are described herein that include a first receiver for
cooperating with a first longitudinal connecting member, such as
flexible, dynamic stabilization connecting member and also a second
receiver for cooperating with a second longitudinal connecting
member having a different diameter and flexibility. Both the first
and second receivers are attachable and detachable to a bone screw
shank, both prior to implantation and after the shank is implanted
in a vertebra. Such allows for a fusionless initial attachment of
the bone screw shank, first receiver and dynamic stabilization
connecting member to the spine. Thereafter, if needed, during a
procedure in which the bone screw shank remains implanted, the
first receiver may be replaced with the second receiver and the
dynamic stabilization connecting member replaced with another
longitudinal connecting member having a different flexibility and a
different diameter, for example, a solid rod having a smaller
diameter, but greater rigidity. In some instances, it may be
desirable to replace a first longitudinal connecting member with a
second, more flexible connecting member having a greater or lesser
diameter than the first longitudinal member. In all such dynamic
stabilization procedures that do not include fusion, one aspect of
the invention is to provide bone screw shanks that have had surface
treatment or coating to provide a biologically active interface
with the bone or at least some component of bone bonding on or bone
ingrowth into the bone screw shank.
[0013] In an embodiment of the present invention, a bone screw with
a shank including a threaded lower portion adapted to be screwed
into a bone and an upper portion with a capture structure and a
central upwardly projecting domed structure; a retaining structure
including a partially spherical outer surface; the retainer
structure being releasably matable with the capture structure of
the shank upper portion; and first and second interchangeable
receivers; each of the receivers having a rod-receiving channel
wherein the rod-receiving channels are shaped to received rods
having different widths; the shank being received in the receiver
and then held in the receiver by the retainer is provided.
[0014] In a further embodiment, the bone screw includes at least a
first rod sized to be received in the rod-receiving channel of the
first receiver. In certain embodiments, the bone screw includes at
least a second rod sized to be received in the rod-receiving
channel of the second receiver.
[0015] In a further embodiment, the bone screw includes a third
interchangeable receiver with a rod-receiving channel shaped to
receive a rod having a width different from the widths of the rods
associated with the first and second interchangeable receivers.
[0016] In a further embodiment, each of the receivers includes an
inner cavity with a partially spherical inner surface cooperatively
slidingly mateable with the outer surface of the retaining
structure, so as to allow for a wide range of pivotal movement
between the shank and the receiver; wherein when the retaining
structure is releasably mated with the capture structure of the
shank upper portion, the domed structure extends into the
rod-receiving channel so as to receive direct downward force from
the rod received in the rod-receiving channel during locking of a
position of the shank relative to the receiver.
[0017] In some embodiments, the shank domed structure includes an
engagement surface on the top thereof. In some embodiments, the
shank domed structure includes a tool receiving surface adapted to
receive a tool for rotating the shank into a bone. In a further
embodiment, the bone screw includes at least a first rod sized to
be received in the rod-receiving channel of the first receiver and
a closure threadedly receivable in the first receiver so as to
block the rod-receiving channel and apply downward force against
the rod when locking the position of the rod relative to the
receiver.
[0018] In another embodiment, a bone anchor assembly is provided,
the assembly having a shank including a threaded lower portion
adapted to be screwed into a bone and an upper portion with a
spline capture structure and a central upwardly projecting domed
structure; a retaining structure including a partially spherical
outer surface and a spline engaging structure releasably fixedly
mateable with the spline capture structure; and a plurality of
interchangeable receivers, each of the receivers including an upper
channel adapted to receive one of a plurality of rods differing
from each other in at least one of structure, fabrication material,
flexibility and elasticity, and an inner cavity with a partially
spherical inner surface cooperatively slidingly mateable with the
retaining structure outer surface so as to allow for a wide range
of pivotal movement between the shank and the receiver; wherein
when the spline engaging structure is releasably mated with the
spline capture structure, the domed structure extends into the
upper channel so as to receive a direct downward force from the rod
in the channel during locking of a position of the shank relative
to the receiver. In a further embodiment, the assembly includes a
plurality of rods differing from each other in at least one of
structure, fabrication material, flexibility and elasticity.
[0019] In yet another embodiment, a bone screw is provided, the
bone screw including a shank including a threaded lower portion
adapted to be screwed into a bone and an upper portion with a
capture structure; and at least two interchangeable receivers
adapted to receive and capture the shank upper portion capture
structure, each of the receivers having a rod-receiving channel,
wherein each of the channels is shaped to receive a rod having a
different width.
[0020] In a further embodiment, the bone screw shank upper portion
capture structure is a helical guide and advancement structure
adapted to cooperatively engage a complementary receiver guide and
advancement structure such that the shank upper portion is
rotatably received within the receiver.
[0021] In another further embodiment, the bone screw further
includes a retaining structure adapted to cooperatively mate with
the shank upper portion capture structure within the receiver. In a
still further embodiment of the bone screw, the shank upper portion
capture structure includes at least one spline capture structure;
and the retaining structure includes a mating spline-engaging
recess.
[0022] In yet another embodiment, a bone screw with a shank
including a threaded lower portion adapted to be screwed into a
bone and an upper portion with a capture structure; a retaining
structure; the retainer structure being releasably matable with the
capture structure of the shank upper portion; and first and second
interchangeable receivers; each of the receivers having a
rod-receiving channel wherein the rod-receiving channels are shaped
to received rods having different widths; the shank being received
in the receiver and then held in the receiver by the retainer is
provided.
OBJECTS AND ADVANTAGES OF THE INVENTION
[0023] Therefore, it is an object of the present invention to
overcome one or more of the problems with polyaxial bone screw
assemblies described above. An object of the invention is to
provide dynamic medical implant stabilization assemblies and
methods for spinal surgery that include bone screws having an
affinity to bone and further include connecting members and/or
receiver members that may be removed and replaced to provide for
the implantation of flexible, semi-rigid or rigid connecting
members. Another object of the invention is to provide dynamic
medical implant stabilization assemblies having longitudinal
connecting members with portions having various configurations for
providing flexible, dynamic stabilization. Additionally, it is an
object of the invention to provide a lightweight, reduced volume,
low profile polyaxial bone screw and longitudinal connecting member
assembly. Furthermore, it is an object of the invention to provide
apparatus and methods that are easy to use and especially adapted
for the intended use thereof and wherein the tools are
comparatively inexpensive to make and suitable for use.
[0024] Other objects and advantages of this invention will become
apparent from the following description taken in conjunction with
the accompanying drawings wherein are set forth, by way of
illustration and example, certain embodiments of this
invention.
[0025] The drawings constitute a part of this specification and
include exemplary embodiments of the present invention and
illustrate various objects and features thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is an exploded perspective view of a polyaxial bone
screw assembly according to the present invention having a shank
with a capture structure at an end thereof, a first receiver, and a
closure structure.
[0027] FIG. 2 is an enlarged and fragmentary view of the assembly
of FIG. 1, showing the first receiver in cross-section, taken along
the line 2-2 of FIG. 1, and illustrating the shank in front
elevation prior to the insertion of the shank capture structure
into the receiver according to a method of the invention.
[0028] FIG. 3 is a reduced and fragmentary cross-sectional view
similar to FIG. 2 showing the shank capture structure being
installed in the first receiver.
[0029] FIG. 4 is an enlarged and fragmentary cross-sectional view
of the first receiver taken along the line 2-2 of FIG. 1 and the
shank taken along the line 4-4 of FIG. 1, illustrating the shank
capture structure fully installed in the receiver and swivelable
therein.
[0030] FIG. 5 is a reduced and fragmentary cross-sectional view of
the first receiver and attached shank of FIG. 4, and further
showing the shank being implanted into a vertebra using a driving
tool mounted on the shank capture structure, the driving tool shown
in front elevation.
[0031] FIG. 6 is an enlarged and fragmentary cross-sectional view,
similar to FIG. 5, also showing the driving tool in cross
section.
[0032] FIG. 7 is a reduced and fragmentary cross-sectional view of
the first receiver and vertebra, similar to FIG. 5, showing the
shank in front elevation and showing a longitudinal connecting
member, in cross-section, disposed in the receiver, and further
illustrating the insertion of the closure structure of FIG. 1 using
a driver, the closure structure and driver shown in front
elevation.
[0033] FIG. 8 is a reduced and fragmentary front-elevational view
of the assembly of FIG. 1, shown with a longitudinal connecting
member in cross-section, the shank implanted in the vertebra and
with the closure structure fully installed.
[0034] FIG. 9 is a reduced and exploded front elevational view of
the shank of FIG. 1 shown implanted in a vertebra, shown with the
first receiver and the longitudinal connecting member of FIG. 1 and
also shown with a replacement receiver and a second, larger
cooperating longitudinal connecting member.
[0035] FIG. 10 is a front elevational view similar to FIG. 9
showing the replacement receiver and the second longitudinal
connecting member with the shank of FIG. 1.
[0036] FIG. 11 is a generally schematic side elevational view of a
patient's spine, showing four tools manipulating four bone screws
with receivers holding a flexible longitudinal connecting
member.
[0037] FIG. 12 is a generally schematic side elevational view of a
patient's spine, showing the four bone screw shanks of FIG. 11 now
installed with replacement receivers and a larger replacement
longitudinal connecting member.
[0038] FIG. 13 is an exploded perspective view of a second bone
screw assembly according to the invention including a shank, a
receiver and a retaining structure.
[0039] FIG. 14 is an exploded and side elevational view of the
embodiment of FIG. 13 also shown with a longitudinal connecting
member and further with a replacement receiver, retaining structure
and longitudinal connecting member of greater rigidity.
[0040] FIG. 15 is a perspective view of a non-uniform longitudinal
connecting member for use according to the invention.
[0041] FIG. 16 is a partial perspective view of a second embodiment
of a non-uniform longitudinal connecting member.
[0042] FIG. 17 is a partial side elevational view of the
longitudinal connecting member of FIG. 16.
[0043] FIG. 18 is a partial top plan view of the longitudinal
connecting member of FIG. 16 shown with a schematic bone screw in
phantom to illustrate orientation when implanted.
[0044] FIG. 19 is a cross-sectional view taken along the line 19-19
of FIG. 17.
[0045] FIG. 20 is a partial perspective view of a third embodiment
of a non-uniform longitudinal connecting member.
[0046] FIG. 21 is a partial side elevational view of the
longitudinal connecting member of FIG. 20.
[0047] FIG. 22 is a partial top plan view of the longitudinal
connecting member of FIG. 20 shown with a schematic bone screw in
phantom to illustrate orientation when implanted.
[0048] FIG. 23 is a partial perspective view'of a fourth embodiment
of a non-uniform longitudinal connecting member.
[0049] FIG. 24 is a partial side elevational view of the
non-uniform longitudinal connecting member of FIG. 23 shown with a
schematic bone screw in phantom to illustrate orientation when
implanted.
[0050] FIG. 25 is a partial top plan view of the longitudinal
connecting member of FIG. 23.
[0051] FIG. 26 is a partial perspective view of a fifth embodiment
of a non-uniform longitudinal connecting member.
[0052] FIG. 27 is a partial side elevational view of the
non-uniform longitudinal connecting member of FIG. 26.
[0053] FIG. 28 is a partial top plan view of the longitudinal
connecting member of FIG. 26 shown with a schematic bone screw in
phantom to illustrate orientation when implanted.
[0054] FIG. 29 is a partial perspective view of a sixth embodiment
of a non-uniform longitudinal connecting member.
[0055] FIG. 30 is a partial side elevational view of the
longitudinal connecting member of FIG. 29.
[0056] FIG. 31 is a partial top plan view of the non-uniform
longitudinal connecting member of FIG. 29 shown with a schematic
bone screw in phantom to illustrate orientation when implanted.
[0057] FIG. 32 is a cross-sectional view taken along the line 32-32
of FIG. 30.
[0058] FIG. 33 is a partial perspective view of a seventh
embodiment of a non-uniform longitudinal connecting member.
[0059] FIG. 34 is a partial side elevational view of the
longitudinal connecting member of FIG. 33.
[0060] FIG. 35 is a partial top plan view of the longitudinal
connecting member of FIG. 33 shown with a schematic bone screw in
phantom to illustrate orientation when implanted.
[0061] FIG. 36 is a partial perspective view of an eighth
embodiment of a non-uniform longitudinal connecting member.
[0062] FIG. 37 is a partial side elevational view of the
longitudinal connecting member of FIG. 36.
[0063] FIG. 38 is a cross-sectional view taken along the line 38-38
of FIG. 37.
[0064] FIG. 39 is a partial perspective view of a ninth embodiment
of a non-uniform longitudinal connecting member.
[0065] FIG. 40 is a partial side elevational view of the
longitudinal connecting member of FIG. 39.
[0066] FIG. 41 is a cross-sectional view taken along the line 41-41
of FIG. 40.
[0067] FIG. 42 is a partial perspective view of an tenth embodiment
of a non-uniform longitudinal connecting member.
[0068] FIG. 43 is a partial side elevational view of the
longitudinal connecting member of FIG. 42.
[0069] FIG. 44 is a cross-sectional view taken along the line 44-44
of FIG. 43.
[0070] FIG. 45 is a partial perspective view of an eleventh
embodiment of a non-uniform longitudinal connecting member.
[0071] FIG. 46 is a perspective view of a mono-axial bone
screw.
[0072] FIG. 47 is a partial front elevational view showing the
longitudinal connecting member of FIG. 45 received in a receiver of
the bone screw of FIG. 46 shown implanted in a vertebra.
DETAILED DESCRIPTION OF THE INVENTION
[0073] As required, detailed embodiments of the present invention
are disclosed herein; however, it is to be understood that the
disclosed embodiments are merely exemplary of the invention, which
may be embodied in various forms. Therefore, specific structural
and functional details disclosed herein are not to be interpreted
as limiting, but merely as a basis for the claims and as a
representative basis for teaching one skilled in the art to
variously employ the present invention in virtually any
appropriately detailed structure.
[0074] With reference to FIGS. 1-10, the reference number 1
generally represents a polyaxial bone screw apparatus or assembly
according to the present invention. The assembly 1 includes a shank
4, a first receiver 6 and a second or replacement receiver 7. The
shank 4 further includes a body 8 integral with an upper portion 9
having a capture structure 10. The shank 4 and the receiver 6 are
often assembled prior to implantation of the shank body 8 into a
vertebra 13, as seen in FIG. 5. However, in an alternative method,
the shank body 8 may be first implanted in the vertebra 13,
followed by joining the receiver 6 to the shank 4. Furthermore, as
will be described in greater detail herein, the first receiver 6
may be removed from an implanted shank body 8 and the second
receiver 7 joined to the shank 4 without the removal of the shank
body 8 from the vertebra 13.
[0075] FIG. 1 further shows a closure structure 16 of the invention
for biasing a longitudinal member such as a longitudinal connecting
member 19 or a longitudinal connecting member 20 against the shank
upper portion 9 which in turn biases the capture structure 10 into
fixed frictional contact with the receiver 6 or 7, so as to fix the
longitudinal connecting member 19 or 20 relative to the vertebra
13. The receiver 6 or 7 and the shank 4 cooperate in such a manner
that the receiver 6 or 7 and the shank 4 can be secured at any of a
plurality of angles, articulations or rotational alignments
relative to one another and within a selected range of angles both
from side to side and from front to rear, to enable flexible or
articulated engagement of the receiver 6 or 7 with the shank 4
until both are locked or fixed relative to each other near an end
of an implantation procedure.
[0076] With reference to FIGS. 1 and 2, the shank 4 is elongate,
with the shank body 8 having a helically wound bone engaging thread
24 extending from near a neck 26 located adjacent to the capture
structure 10 to near a tip 28 of the body 8 and projecting radially
outwardly therefrom. To provide a biologically active interface
with the bone, an outer surface 29 the shank body 8 that includes
the thread 24 and extends between the neck 26 and the tip 28 is
coated, perforated or otherwise treated 30. The treatment 30 may
include, but is not limited to a plasma spray coating, a
hydroxyapatite (HA) or tricalcium phosphate (TCP) coating, or other
type of roughening, perforation or indentation in the surface 29,
such as by sputtering, sand blasting or acid etching, that allows
for bony ingrowth. Such treatments have been utilized, for example,
on titanium dental implants in order to roughen the implant surface
and to provide an enduring bond between confronting or interfacing
surfaces of the dental implant and the host bone. Coating with
hydroxyapatite, a bio-ceramic calcium phosphate coating, is
desirable as hydroxyapatite is chemically similar to bone with
respect to mineral content and has been identified as being
bioactive and thus supportive of bone ingrowth in dental and
maxillofacial applications.
[0077] During use, rotation of the body 8 utilizes the thread 24
for gripping and advancement in the bone and is implanted into the
vertebra 13 leading with the tip 28 and driven down into the
vertebra 13 with an installation or driving tool 31, so as to be
implanted in the vertebra 13 to near the neck 26, as shown in FIG.
5 and as is described more fully in the paragraphs below.
[0078] The shank 4 has an elongate axis of rotation generally
identified by the reference letter A. It is noted that any
reference to the words top, bottom, up and down, and the like, in
this application refers to the alignment shown in the various
drawings, as well as the normal connotations applied to such
devices, and is not intended to restrict positioning of the
assembly 1 in actual use.
[0079] The neck 26 extends axially outwardly and upwardly from the
shank body 8 to a base 34 of the capture structure 10. The neck 26
generally has a reduced radius as compared to an adjacent top 36 of
the shank body 8. Further extending axially and outwardly from the
neck 26 is the capture structure 10 that provides a connective or
capture apparatus disposed at a distance from the body top 36 and
thus at a distance from the vertebra 13 when the shank body 8 is
implanted in the vertebra 13.
[0080] The capture structure 10 is configured for connecting the
shank 4 to the receiver 6 or 7 and then capturing the shank 4 in
the receiver 6 or 7. The capture structure 10 has an outer
partially spherically shaped surface 40 extending from the base 34
to a top portion 44. The illustrated base 34 has a smooth surface,
but it is foreseen that the base 34 may have a high-friction or
roughened surface, such as a scored or knurled surface. Formed on
an upper part 46 of the surface 40 is a helical guide and
advancement structure 48. The guide and advancement structure 48
retains the substantially spherical outer shape of the surface 40
at a crest thereof, but may be otherwise described as a
substantially square thread form, sized and shaped to mate with a
cooperating guide and advancement structure 50 disposed on an inner
surface 52 of the receiver 6 disposed adjacent to and defining an
opening 54 of a lower end or bottom 56 of the receiver 6.
Preferably, the guide and advancement structure 48 is relatively
thick and heavy to give strength to the thread and prevent the
thread from being easily bent or deformed when axial pressure is
applied to the shank 4 to maintain the capture structure 10 in the
receiver 6, as described further below. The second or replacement
receiver 7 also includes an inner guide and advancement structure
(not shown), substantially identical to the guide and advancement
structure 50 for mating with the guide and advancement structure
48.
[0081] The guide and advancement structure 48 winds about the upper
portion 46 in a generally helical pattern or configuration that is
typical of threads and can have various pitches, be clockwise or
counterclockwise advanced, or vary in most of the ways that
conventional square threads vary. The guide and advancement
structure 48 has a leading surface or flank 58 and a trailing
surface or flank 59. As used herein, the terms leading and trailing
refer to the direction of advancement of the capture structure 10
into the guide and advancement structure 50 of the receiver 6
aligning the axis A of the shank 4 with an elongate axis of
rotation B of the receiver 6 and directing the capture structure 10
toward the receiver 6, as shown by the straight arrow C illustrated
in FIGS. 2 and 3.
[0082] The leading surface 58 has an inner edge 62 and an outer
edge 63. The trailing surface 59 has an inner edge 66 and an outer
edge 67. As is typical of square threads, a root surface 69 between
the inner edges 62 and 66 is parallel to the axis of rotation A and
has an axial length that remains substantially constant throughout
the threadform. Likewise, an axial distance between the outer edges
63 and 67 remains substantially constant, while the size of a crest
or connecting surface 70 between the edges 63 and 67 varies, due to
the spherical form of the crest surface 70. As can be seen, for
example, in FIG. 4, the root surface 69 is disposed substantially
perpendicular to the leading surface 58 and the trailing surface
59.
[0083] Although the substantially square threadform 48 is described
herein, it is foreseen that other thread types, such as V-threads,
inverted thread types, such as inverted buttress threads, other
thread-like or non-thread-like guide and advancement structures,
such as flange form helically wound advancement structures may be
utilized according to the invention.
[0084] Advancement of the capture structure 10 into the receiver 6
is accomplished by rotating the shank 4 in a counterclockwise
direction about the axes A and B and into the receiver 6 as
illustrated in FIG. 3. As will be described more fully below, the
connecting crest surface 70 is a loading surface after the capture
structure 10 is fully disposed in the receiver 6. Also as will be
described in more detail below, although discontinuous, the
spherical surface 70 has an outer radius that is approximately
equal to a radius of an inner seating surface of the receiver 6 or
7, allowing for slidable mating contact between the surface 70 and
an inner seating surface of the receiver 6 or 7.
[0085] In the embodiment shown, the shank 4 further includes a
longitudinal connecting member and tool engagement structure 74
projecting upwardly from the top portion 44 of the capture
structure 10. The tool engagement structure 74 has a hexagonally
shaped head 76 with a substantially domed top 78. The structure 74
is coaxial with both the threaded shank body 8 and the capture
structure 10. The head 76 is sized and shaped for engagement with
the driving tool 31 shown in FIGS. 5 and 6 that includes a driving
and mating structure in the form of a socket. The tool 31 is
configured to fit about the head 76 so as to form a socket and
mating projection for both operably driving and rotating the shank
body 8 into the vertebra 13.
[0086] In the embodiment shown, to provide further mechanical
advantage during installation of the shank 4 into the vertebra 13,
the capture structure 10 includes a counter-sunk portion 80 formed
in the top 44, the portion 80 adjacent to and surrounding the head
76. The portion 80 includes a planar seating surface 82 disposed
perpendicular to the axis A and spaced from the top portion 44.
Contiguous to both the surface 82 and the top 44 are faces 84 that
are disposed parallel to the axis A and thus are substantially
perpendicular to the surface 82. The faces 84 form a hex-shaped
outer periphery of the counter-sunk portion 80. The tool 31
includes an outer surface portion 90 sized and shaped to mate with
the bottom and both side walls of the counter-sunk portion 80, such
that a bottom 91 of the tool 31 seats on the surface 82 and the
outer surface portion 90 is adjacent to and engaging the faces 84
when the tool 31 is disposed about and engaging with the
hexagonally shaped head 76.
[0087] The domed top end surface 78 of the shank 4 is preferably
convex, curved or dome-shaped as shown in the drawings, for
positive engagement with the longitudinal connecting member 19 when
the bone screw assembly 1 is assembled, as shown in FIGS. 8 and 10,
and in any alignment of the shank 4 relative to the receiver 6 or
7. While not required for the practice of the invention, in the
embodiment shown in the drawings, the top end surface 78 is scored
or knurled to further increase frictional engagement between the
surface 78 and the longitudinal connecting member 19. It is
foreseen that in certain embodiments, the surface 78 may be smooth.
The dome 78 may be radiused so that the dome 78 engages the
longitudinal connecting member 19 slightly above a longitudinal
connecting member receiving channel in the receiver 6 or 7, even as
the receiver 6 or 7 is swivelled relative to the shank 4 so that
pressure is always exerted on the dome surface 78 by the
longitudinal connecting member 19 when the assembly 1 is fully
assembled. It is foreseen that in other embodiments the dome 78 can
have other shapes which may include off-axis apertures for driving
the shank with a mating tool. The dome can also involve one or more
arched sections with flat external surfaces which can mate with a
driving tool.
[0088] The shank 4 shown in the drawings is cannulated, having a
small central bore 92 extending an entire length of the shank 4
along the axis A. The bore 92 is defined by an inner substantially
cylindrical wall 95 of the shank 4 and has a first circular opening
96 at the shank tip 28 and a second circular opening 98 at the top
domed surface 78. The bore 92 is coaxial with the threaded body 8
and the capture structure 10. The bore 92 provides a passage
through the shank 4 interior for a guide pin or length of wire 103
inserted into a small pre-drilled bore 105 in the vertebra 13 prior
to the insertion of the shank body 8, the pin 103 providing a guide
for insertion of the shank body 8 into the vertebra 13.
[0089] The receiver 6 is partially cylindrical in external profile
and includes a base portion 110 extending from the end 56 to a
V-shaped surface 111 disposed at a periphery of a longitudinal
connecting member seating surface 112 and extending radially
outwardly and downwardly therefrom. The base 110 is integral with a
pair of upstanding and spaced arms 114. The surface 112 and the
arms 114 forming a U-shaped channel 116 between the arms 114 and
having an upper opening 119. The lower surface 110 defining the
channel 116 preferably has substantially the same radius as the
longitudinal connecting member 19. In operation, the longitudinal
connecting member 19 preferably is located just above the channel
lower surface 112, as shown in FIG. 8.
[0090] Each of the arms 114 has an interior surface 122 that
defines an inner cylindrical profile and includes a discontinuous
helically wound guide and advancement structure 124 beginning at a
top 125 of the receiver 6 and extending downwardly therefrom. The
guide and advancement structure 124 is a partial helically wound
flange-form configured to mate under rotation about the axis B with
a similar structure disposed on the closure structure 16, as
described more fully below. However, it is foreseen that the guide
and advancement structure 124 could alternatively be a V-shaped
thread, a buttress thread, a square thread, a reverse angle thread
or other thread-like or non-thread-like helically wound guide and
advancement structure for operably guiding under rotation and
advancing the closure structure 16 between the arms 114, as well as
eventual torquing when the closure structure 16 abuts against the
longitudinal connecting member 19.
[0091] The receiver 6 includes external apertures or grip bores 128
disposed on each of the arms 114 for positive engagement by holding
tools to facilitate secure gripping of the receiver 6 during
assembly of the receiver 6 with the shank 4. Furthermore, the grip
bores 128 may be utilized to hold the receiver 6 during the
implantation of the shank body 8 into the vertebra 13. The bores
128 are centrally located on the respective arms 114 and
communicate with upwardly projecting hidden recesses 129 to further
aid in securely holding the receiver 6, for example, to an end
guide or holding tool 130 or an intermediate guide or holding tool
131 illustrated in FIG. 11, the guide tools 130 and 131 having
structure (not shown) for communicating both with the bores 128 and
recesses 129. The guide tools 130 and 131 have channels or slots
(not shown) for alignment with the U-shaped channel 116 of the
receiver 6 and sized and shaped to receive a longitudinal
connecting member 19 or other elongate structure therethrough. The
guide tools 130 and 131 are preferably further equipped with
elongate channels extending along lengths thereof for the placement
of closure structures 16 and other tools therein, utilized to press
and lock a longitudinal connecting member 19 or other elongate
structure within the receiver 6. It is foreseen that the bores 128
and recesses 129 may be configured to be of a variety of sizes,
shapes and locations along outer surfaces of the arms 114 for
cooperation with one or more holding tools.
[0092] Communicating with the U-shaped channel 116 of the receiver
6 is a chamber or cavity 136 substantially defined by a partially
spherical inner surface 138 that is disposed primarily in the base
portion 110 of the head beneath the interior cylindrical surface
122 of the arms 112 and 114 and extending into the inner surface 52
that is further defined by the guide and advancement structure 50.
The cavity 136 communicates with both the U-shaped channel 116 and
a bore 140 that also is defined by the guide and advancement
structure 50, that in turn communicates with the opening 54 at the
bottom 56 of the receiver 6.
[0093] The guide and advancement structure 50 includes a leading
surface 152 and a trailing surface 156. Similar to what is
described herein with respect to the guide and advancement
structure 48 of the capture structure 10, the guide and advancement
structure 50 is preferably of a square thread type as such
structure provides strength and stability to the assembly 1, with
the leading surface 152 and the trailing surface 156 being
substantially parallel. A crest surface 157 spanning between the
leading surface 152 and the trailing surface 156 is curvate, having
a radius the same or substantially similar to a radius of the
cavity spherical wall 138. As with the guide and advancement
structure 48, it is foreseen that other types of threaded and
non-threaded helical structures may be utilized in accordance with
the present invention for the receiver 6.
[0094] A juncture of the interior surface 122 and the cavity inner
surface 138 forms an opening or neck 158 that has a radius
extending from the Axis B that is smaller than a radius extending
from the Axis B to the inner surface 138. Also, a radius from the
lower opening 54 to the Axis B is smaller than the radius extending
from the Axis B to the inner surface 138 and the inner surface
portion 52 defining the guide and advancement structure 50. Thus,
the cavity or chamber 136 is substantially spherical, widening and
opening outwardly and then inwardly in a direction toward the lower
opening 54. However, it is foreseen that other shapes, such as a
cone or conical shape, may be utilized for a head inner cavity
according to the invention. Also, a cylindrical head inner cavity
with a retainer ring located approximate the lower opening 54 could
be utilized according to the invention.
[0095] After the guide and advancement structure 48 of the capture
structure 10 is mated and rotated to a position within the cavity
136 and further upwardly and axially into non-engagement beyond the
trailing surface 156 of the guide and advancement structure 50, the
capture structure 10 is rotatable or swingable within the cavity
136 until later frictionally locked in place, and cannot be removed
from the receiver 6 through the upper neck 158 or through the lower
bore 140 without reversing the assembly process with the components
in axial alignment. As shown in FIG. 4, the capture structure 10 is
held within the cavity 136 from above by the partially spherical
surface 138 and from below by the threaded inner surface 52. Stated
in another way, the thick strong threadform 50 having the curvate
surface 157 of the receiver 6 disposed along the surface 52, and
the slidingly mated curvate surface 70 of the thick strong
threadform 48 of the capture structure 10, prevent the capture
structure 10 from being pushed or pulled from the chamber 136,
unless the capture structure 10 is rotated and unscrewed therefrom
again through the bore 140 in axial alignment. If there is no
pressure from above, the cavity or chamber 136 allows the structure
10 to freely rotate in the chamber 136 to a position or orientation
desired by a surgeon. In this manner, the receiver 6 is able to
swivel or swing about the shank 4 until subsequently locked in
place.
[0096] The illustrated second or replacement receiver 7 is
substantially identical to the receiver 6 in form and function,
constructed for engagement with the capture structure 10 as
previously described herein with respect to the receiver 6,
therefore the disclosure herein with respect to the receiver 6 is
incorporated by reference with respect to the receiver 7. The
receiver 7 differs from the receiver 6 in that the receiver 7 is
sized to snugly receive the longitudinal connecting member or
longitudinal member 20 that is of a different size diameter or
width than the longitudinal connecting member 19. In the embodiment
illustrated in FIG. 9, the receiver 7 has a U-shaped channel 160
having a lower seating surface 161, the channel 160 being wider
than the channel 116 of the receiver 6. The channel 160 is sized
and shaped to receive the longitudinal connecting member 20 that
has a diameter or cross-sectional width larger than a diameter or
cross-sectional width of the longitudinal connecting member 19.
[0097] The elongate longitudinal connecting members or longitudinal
members, such as the longitudinal connecting members 19 and 20 that
are utilized with the assembly 1 can be any of a variety of
implants utilized in reconstructive spinal surgery, but are
typically elongate structures with substantially uniform
cylindrical portions for placement within the receivers 6 and 7
respectively. The illustrated longitudinal connecting member 19 has
a smaller diameter than a diameter of the illustrated longitudinal
connecting member 20, providing an initial flexible structural
connection between bone screw assemblies 1, that may then be
replaced with a more rigid connection, if necessary, utilizing the
replacement receiver 7 and the longitudinal connecting member 20,
as will be described in greater detail below. As will also be
described in greater detail below with respect to FIGS. 15-43,
dynamic stabilization longitudinal connecting members according to
the invention, such as the longitudinal connecting member 19 may be
of a variety of configurations along a length thereof, some with
uniform portions and others with non-uniform portions that are
positioned between implanted spinal anchors, such as bone screws
and hooks, providing structure for flexible, yet strong, dynamic
stabilization medical implant assemblies.
[0098] The longitudinal connecting member portions that are
received by the receiver 6 or 7 include cylindrical surfaces 162 or
163, respectively. The illustrated surfaces 162 and 163 are smooth
but they could be textured. The longitudinal connecting members 19
and 20 are also preferably sized and shaped to snugly seat near the
bottom of the U-shaped channels 116 and 160 of respective receivers
6 and 7, and, during normal operation, are positioned slightly
above the bottom of the channels 116 and 160, respectively, near,
but spaced from, respective lower surfaces 112 and 161. The
longitudinal connecting member cylindrical surfaces 162 or 163
normally directly or abutingly engage the shank top surface 78, as
shown in FIGS. 8 and 10 and are biased against the dome shank top
surface 78, consequently biasing the shank 4 downwardly in a
direction toward the base of the receiver 6 or 7 when fully
assembled with the longitudinal connecting member 19 or 10 and a
closure member, such as the closure member 16. For this to occur,
the shank top surface 78 must extend at least slightly into the
space of the channel 116 or 160, above the respective surface 112
or 161 when the capture structure 10 is snugly seated in the lower
part of the receiver cavity. The pressure placed on the capture
structure 10 by the longitudinal connecting member 19 or 20 and a
closure member may also cause a spreading or expansion of the
capture structure 10, causing some interlocking or interdigitation
between the guide and advancement structure 48 and the guide and
advancement structure on the receiver 6 or 7. The shank 4 and the
capture structure 10 are thereby locked or held in position
relative to the receiver 6 or 7 by the longitudinal connecting
member 19 or 20 respectively, firmly pushing downward on the shank
domed surface 78.
[0099] With reference to FIGS. 1, 7 and 8, the closure structure or
closure top 16 can be any of a variety of different types of
closure structures for use in conjunction with the present
invention with suitable mating structure on the upstanding arms 114
of the receiver 6. The closure top 16 is rotated between the spaced
arms 114 and closes the top of the channel 116 to capture the
longitudinal connecting member 19 therein. Likewise, a similar
closure top (not shown) may be utilized to close the channel 160 of
the receiver 10 to capture the longitudinal connecting member 20
therein.
[0100] The illustrated closure top 16 has a generally cylindrically
shaped body 170, with a helically wound guide and advancement
structure 172 that is sized, shaped and positioned so as to engage
the guide and advancement structure 124 on the receiver arms 114 to
provide for rotating advancement of the closure structure 16 into
the receiver 6 when rotated clockwise and, in particular, to cover
the top or upwardly open portion of the U-shaped channel 116 to
capture the longitudinal connecting member 19, preferably without
splaying of the arms 114. The body 170 further includes a base or
bottom 174 having a pointed longitudinal connecting member engaging
projection or point 175 extending or projecting axially beyond a
lower rim 176. However, it is foreseen that the bottom could be
flat and smooth and/or flat and knurled. The closure structure 16,
with the projection 175 frictionally engaging and abrading the
longitudinal connecting member surface 162, thereby applies
pressure to the longitudinal connecting member 19 under torquing,
so that the longitudinal connecting member 19 is urged downwardly
against the shank domed surface 78 that extends into the channel
116. Downward biasing of the shank surface 78 operably produces a
frictional engagement between the longitudinal connecting member 19
and the surface 78 and also urges the capture structure 10 toward
the base 110 of the receiver 6, as will be described more fully
below, so as to frictionally seat the capture structure buttress
thread 48 and/or lower portion 72 against the threaded inner
surface 52 of the receiver 6, also fixing the shank 4 and capture
structure 10 in a selected, rigid position relative to the receiver
6.
[0101] The illustrated closure structure 16 further includes a
substantially planar top surface 178 that has a centrally located,
hexalobular internal driving feature 180 formed therein (sold under
the trademark TORX), which is characterized by an aperture with a
6-point star-shaped pattern. It is foreseen that paired off-axis
apertures, on-axis multi-lobular and other driving features or
apertures, such as slotted, hex, tri-wing, spanner, and the like
may also be utilized according to the invention. With reference to
FIG. 7, a driving/torquing tool 181 having a cooperating
hexalobular driving head is used to rotate and torque the closure
structure 16. The tool 181 may also be utilized for removal of the
closure structure 16, if necessary.
[0102] It is foreseen that a closure structure according to the
invention may be equipped with a break-off feature or head, the
closure structure sized and shaped to include a break-way region
that breaks at a preselected torque that is designed to properly
seat the closure structure in the receiver 6. Such a closure
structure would include removal tool engagement structure, such as
a pair of spaced apart apertures or bores, a countersunk hex-shaped
aperture, a left hand threaded bore, or the like, fully accessible
after the break-off head feature breaks away from a base of the
closure structure.
[0103] In use, prior to the polyaxial bone screw assembly 1 being
implanted in a vertebra according to the invention, the shank
capture structure 10 is typically pre-loaded by insertion or
bottom-loading into the receiver 6 through the opening 54 at the
bottom end 56 of the receiver 6. The capture structure 10 is
aligned with the receiver 6, with the axes A and B aligned so that
the guide and advancement structure 48 of the capture structure 10
is inserted into and rotatingly mated with the guide and
advancement structure 50 on the receiver 6. The shank 4 is rotated
in a counter-clockwise direction to fully mate the structures 48
and 50, as shown in FIG. 3, and the counter-clockwise rotation is
continued until the guide and advancement structure 48 disengages
from the guide and advancement structure 50 and the capture
structure 10 is fully disposed in the receiver cavity 136.
[0104] In the position shown in FIG. 4, the shank 4 is in slidable
and rotatable engagement with the receiver 6, while the capture
structure 10 is maintained in the receiver 6 with the shank body 8
in rotational relation with the receiver 6. The shank body 8 can be
rotated through a substantial angular rotation relative to the
receiver 6, both from side to side and from front to rear so as to
substantially provide a universal or ball joint wherein the angle
of rotation is restricted by the lower receiver opening 54.
[0105] With reference to FIGS. 5 and 6, the assembly 1 is then
typically screwed into a bone, such as the vertebra 13, by rotation
of the shank body 8 using the driving tool 31 that operably drives
and rotates the shank 8 by engagement thereof with the hexagonally
shaped extension head 76 of the shank 4.
[0106] Preferably, when the driving tool 31 engages the head 76
during rotation of the driving tool 31, the outer portion 90 also
engages the faces 84 and the bottom 91 of the tool 31 is fully
seated upon and frictionally engages with the planar surface 82
disposed in the counter-sunk portion 80 of the capture structure
10. It is foreseen that in other embodiments according to the
invention, the counter-sunk portion may be defined by more or fewer
engaging surfaces, or the counter-sunk portion could be
eliminated.
[0107] It is foreseen that in an alternative method according to
the invention, the shank 4 is first implanted into the vertebra 13
by rotation of the shank 8 into the vertebra 13 using the driving
tool 31 that operably drives and rotates the shank 8 by engagement
thereof with the hexagonally shaped extension head 76 of the shank
4. As already described herein, when the driving tool 31 engages
the head 76 during rotation of the driving tool 31, the outer
portion 90 also engages the faces 84 and a bottom of the tool 31 is
fully seated upon and frictionally engages with the planar surface
82 disposed in the counter-sunk portion 80 of the capture structure
10. It may be desirable to only partially implant the shank 8 into
the vertebra 13, with the capture structure 10 extending proud to
provide space for the attachment of the receiver 6 to the shank 4.
The receiver 6 is then attached to the shank 4 by inserting the
receiver 6 onto the capture structure with the axes A and B aligned
and mating the thread 48 with the thread 50 by rotating the
receiver 6 in a clockwise direction. The head is then rotated until
the thread 48 disengages with the thread 50 and the capture
structure 10 is freely rotatably disposed in the head cavity 136.
Then, the shank body the shank 4 can be further driven into the
vertebra 13, if necessary, utilizing the driving tool 31 as already
described herein. The remainder of the implant assembly includes
elements that have been previously described.
[0108] With particular reference to FIGS. 5, 6 and 11, a procedure
may begin by forming a relatively small incision in the skin for
each bone screw shank 8 to be implanted. The incisions are
stretched into a round shape with a circumference equal to or just
slightly larger than the guide tools 130 and 131. The skin is
relatively flexible and allows the surgeon to move the incision
around relative to the spine to manipulate the various tools and
implants, as required. The vertebra 13 may be pre-drilled with the
small tap bore 105 to minimize stressing the bone and thereafter
have the guide wire or pin 103 inserted therein to provide a guide
for the placement and angle of the shank 4 with respect to the
vertebra 13. A further bore (not shown) may be made with the guide
pin 103 as a guide. Then, the assembly 1 is threaded onto the guide
pin 103 utilizing the cannulation bore 92 by first threading the
pin 103 into the bottom opening 96 and then out of the top opening
98. A receiver 6 is attached to a guide tool 130 or 131 and the
shank body 8 is then driven into the vertebra 13, using the pin 103
as a placement guide.
[0109] With reference to FIGS. 7 and 11, the longitudinal
connecting member 19 is eventually positioned within the head
U-shaped channel 116 by inserting the longitudinal connecting
member 19 diagonally through a skin incision near an end tool 130
so that a first longitudinal connecting member end passes through
channels (not shown) in any intermediate guide tools 131 and into
the channel (not shown) of the other end guide tool 130. Back
muscle tissue separates easily here to allow the upper insertion of
the longitudinal connecting member 19 and can be further separated
by finger separation or cutting through one of the incisions if
required. In a preferred method, once the longitudinal connecting
member 19 is positioned within channels of the guide tools 130 and
131, the closure structure or top 16 is inserted into each of the
tools 130 and 131 and advanced so as to bias or push against the
longitudinal connecting member 19, pressing the longitudinal
connecting member 19 to the bone screw receiver 6 and into the
channel 116 by rotation of the closure top 16 between the arms 114.
The closure structure 16 is rotated, utilizing the tool 181 in
engagement with the driving feature or aperture 180 until an
appropriate torque is achieved, for example 90 to 120 inch pounds,
to urge the longitudinal connecting member 19 downwardly.
[0110] With reference to FIG. 8, the shank top domed surface 78,
because it is rounded to approximately equally extend upward into
the channel 116 approximately the same amount no matter what degree
of rotation exists between the shank 8 and the receiver 6 and
because the surface 78 is sized to extend upwardly into the
U-shaped channel 116, the surface 78 is engaged by the longitudinal
connecting member 19 and pushed downwardly toward the base 110 of
the receiver 6 when the closure structure 16 biases downwardly
toward and onto the longitudinal connecting member 19.
[0111] Downward pressure on the shank 4 in turn urges the capture
structure 10 base 34 and spherical crest surface 70 downward toward
the receiver inner spherical surface 138 and crest surface 157. As
the closure structure 16 presses against the longitudinal
connecting member 19, the longitudinal connecting member 19 presses
against the shank 4, and the capture structure 10 becomes
frictionally and rigidly attached to the receiver 6. If the
pressure is such that the capture structure 10 expands, a meshing
and/or interlocking of the guide and advancement structure 48 and
the guide and advancement structure 50 may occur, further fixing
the shank body 8 in a desired angular configuration with respect to
the receiver 6 and the longitudinal connecting member 19.
[0112] FIG. 8 illustrates the polyaxial bone screw assembly 1 with
the longitudinal connecting member 19 and the closure structure 16
positioned in a vertebra 13. The axis A of the bone shank 8 is
illustrated as not being coaxial with the axis B of the receiver 6
and the shank body 8 is fixed in this angular locked configuration.
Other angular configurations can be achieved, as required during
installation surgery due to positioning of the longitudinal
connecting member 19 or the like.
[0113] According to a method of the invention, the bone screw
assembly 1 and the longitudinal connecting member 19 are implanted
as shown in FIGS. 8 and 11 to provide for a dynamic stabilization
of a portion of the spine. In such a procedure, vertebrae are not
prepared for fusion and the longitudinal connecting member 19 is
not rigid, thus allowing for some flexible movement along the
portion of the spine supported by the longitudinal connecting
member 19. If, after time, further damage or weakness of the spine
occurs, a method according to the invention allows for replacement
of the flexible longitudinal connecting member 19 with the more
rigid longitudinal connecting member 20, without removal of the
bone screw shank 8 from the vertebra 13. With reference to FIGS. 9,
10 and 12, in such a procedure, partial disassembly is accomplished
by using the driving tool 181 that is received in and mates with
the driving feature 180 and then turned counterclockwise to rotate
the closure structure 16 and reverse the advancement thereof in the
receiver 6. Then, the longitudinal connecting member 19 may be
removed in a percutaneous fashion in reverse order to the procedure
described previously herein for assembly. The receiver 6 is then
removed from the bone screw shank 4 by aligning the axis B of the
receiver 6 with the axis A of the shank 4 and rotating the receiver
in a counter-clockwise fashion with respect to the shank 4, the
guide and advancement structure 50 aligned and rotatably mated with
the guide and advancement structure 48 until the receiver 6 is
detached from the shank 4.
[0114] If desired, selected vertebrae are abraded or otherwise
prepared in a manner known in the art, including tissue removal,
the addition of bone chip or other bone material, and/or bone
growth promoting material, to result in fusion of the portion or
portions of the spine being more rigidly fixed in place by the
replacement receivers 7 and the longitudinal connecting member 20.
Each replacement receiver 7 is then mounted on a capture structure
10, and rotated in a clockwise fashion, mating a guide and
advancement structure on the inner surface of the receiver 7 (not
shown) with the guide and advancement structure 48, the receiver 7
being rotated to fully mate the guide and advancement structures
until the guide and advancement structure 48 is disengaged and the
capture structure 10 is disposed in the receiver 7, the receiver 7
being freely rotatable with respect to the capture structure 10.
The same procedure is followed along the spine to replace each
receiver 6 with a receiver 7.
[0115] With reference to FIG. 12, the more rigid longitudinal
connecting member 20 is installed in the receivers 7 similarly to
what has been described previously herein with respect to the
installation of the longitudinal connecting member 19 into the
receivers 6. A closure structure (not shown), similar to the
closure structure 16 is installed into each of the receivers 7,
also as previously described herein.
[0116] With reference to FIGS. 13 and 14, a second embodiment of a
bone screw assembly according to the invention, generally 201,
includes a shank 204, a first receiver 206 and a second or
replacement receiver 207. The shank 204 also includes a body 208
integral with an upper portion 209 having a spline capture
structure 210. The assembly 201 further includes a retaining
structure 211 adapted for fixed mating engagement with the spline
capture structure 210 within the receiver 206 or 207. The spline
capture connection between the capture structure 210 and the
retaining structure 211 is described in detail in U.S. Pat. No.
6,716,214 and incorporated by reference herein. Also as described
in the '214 patent, the retaining structure 211 includes a
partially spherical surface 214 that is slidingly mateable with a
cooperating inner surface of the receiver 206 or 207, allowing for
a wide range of pivotal movement between the shank 204 and the
receiver 206 or 207. In addition to what is described in U.S. Pat.
No. 6,716,214, to provide a biologically active interface with the
bone, an outer surface 216 of the shank body 208 that includes the
thread is textured, coated, perforated or otherwise treated 218 as
illustrated by a speckled surface on the drawing figures. The
treatment 218 may include, but is not limited to a plasma spray
coating, a hydroxyapatite (HA) coating, or other type of
roughening, perforation or indentation in the surface 216, such as
by sputtering, sand blasting or acid etching, that allows for bony
on growth or ingrowth.
[0117] It is foreseen that other types of capture connections may
also be used in bone screws according to the invention, including,
but not limited to, conical, spherical, threaded, and frictional
connections and retaining rings.
[0118] With reference to FIG. 13, the shank 204, the retaining
structure 211 and the receiver 206 are typically assembled prior to
implantation of the shank body 208 into a vertebra 213 by uploading
the shank 204 into the receiver 206 and upwardly through the
retaining structure 211 and then mating the spline capture
structure 210 with the retaining structure 211 by rotating the
capture structure 210 about a central axis of the shank 204 to
about 60 degrees relative to the receiver, followed by downward
movement, with splines of the capture structure 210 entering
recesses in the retaining structure 211, as more fully described in
U.S. Pat. No. 6,716,214. In an alternative method, the shank body 8
may be first implanted in the vertebra 13, followed by joining the
receiver 6 to the shank 4 by mating the capture structure 210 with
the retaining structure 211. Furthermore, as will be described in
greater detail herein, the first receiver 6 may be removed from an
implanted shank body 8 and the second receiver 7 joined to the
shank 4 without the removal of the shank body 8 from the vertebra
13.
[0119] As illustrated in FIG. 14, the first receiver 206 is adapted
to cooperate with a flexible longitudinal connecting member 219 of
uniform diameter that is similar or identical to the longitudinal
connecting member 19 described herein with respect to the assembly
1, and the second receiver 207 is adapted to cooperate with a more
rigid longitudinal connecting member 220 (similar or identical to
the longitudinal connecting member 20 of the assembly 1), the
longitudinal connecting member 220 having a uniform diameter
greater than a diameter of the flexible longitudinal connecting
member 219. The shank upper portion 209 includes a curved or domed
top surface 222 for contacting the longitudinal connecting member
219 or 220 in the same manner described previously herein with
respect to the domed top 78 of the shank 4 and the longitudinal
connecting members 19 or 20.
[0120] The longitudinal connecting member 219 is implanted into an
assembly 201 having the first receiver 206 in a manner similar or
identical to the implantation procedure previously described herein
with respect to the longitudinal connecting member 19 and the
assembly 1 having the receiver 6. It is foreseen that the shank 204
may or may not be cannulated and that the assembly 201 may further
include a closure structure similar to the closure top 16 or other
types of closure structure, for example, as described in U.S. Pat.
No. 6,716,214, for advancement into the receiver 206 and biasing
against the flexible longitudinal connecting member 219.
[0121] Similar to the procedure previously described herein with
respect to the receiver 6 and the longitudinal connecting member
19, if, after time, further damage or weakness of the spine occurs,
a method according to the invention allows for replacement of the
flexible longitudinal connecting member 219 with the more rigid
longitudinal connecting member 220, without removal of the bone
screw shank 208 from the vertebra 213. In such a procedure, partial
disassembly is accomplished by using a driving tool to remove the
closure structures (not shown) from receivers 206, followed by
removal of the longitudinal connecting member 219, preferably in a
percutaneous fashion. The receiver 206 is then removed from the
bone screw shank 204 by aligning the retaining structure/bone shank
combination coaxially with the receiver 206 and then placing
downward pressure on the retaining structure 211, causing the
spline capture structure 210 to move upwardly toward the U-shaped
channel of the receiver 206, disengaging the retaining structure
211 from the capture structure 210. The retaining structure 211 is
then rotated about a central axis of the shank 204 about 60
degrees, aligning the splines of the capture structure 210 with
axially aligned through-channels in the retaining structure 211,
followed by upward movement of the receiver 206, with splines of
the capture structure 210 entering the axial through-channels,
allowing the receiver 206 and the retaining structure 211 to be
disengaged and removed from the bone screw shank 204.
[0122] If desired, selected vertebrae are abraded or otherwise
prepared in a manner known in the art, including but not limited to
tissue removal, the addition of bone chip or other bone material,
and/or bone growth promoting material to result in fusion of the
portion or portions of the spine being more rigidly fixed in place
by the replacement receivers 207 and the cooperating longitudinal
connecting member 220. Each replacement receiver 207 with
cooperating retaining structure 211 therein is then mounted on a
capture structure 210 by placing the receiver 207 and aligned
retaining structure 211 downwardly on the shank 204 until the
capture structure 210 extends beyond the retaining structure 211.
Then, the capture structure 210 is mated with the retaining
structure 211 by rotating the retaining structure 211 about a
central axis thereof about 60 degrees, followed by downward
movement of the retaining structure, with splines of the capture
structure 210 entering recesses in the retaining structure 211 as
described in U.S. Pat. No. 6,716,214. The same procedure is
followed along the spine to replace each receiver 206 with a
receiver 207.
[0123] With reference to FIG. 12, the more rigid longitudinal
connecting member 220 is installed, preferably percutaneously, in
the receivers 207, similarly to what has been described previously
herein with respect to the installation of the longitudinal
connecting member 19 into the receivers 6. A closure structure (not
shown), similar to the closure structure 16 or as described in U.S.
Pat. No. 6,716,214, is installed into each of the receivers 7, also
as previously described herein. It is noted that although the
illustrated embodiments show replacing a smaller diameter rod with
a larger diameter rod, in certain circumstances a larger diameter
or width connecting member may be replaced by a member with a
smaller width or cross-section. This may be desirable depending
upon the materials chosen and other properties or geometries of the
initially implanted connecting member and the replacement
connector.
[0124] With reference to FIG. 15, in an alternative, non-uniform
embodiment according to the invention, a longitudinal connecting
member 250 may be used with the receiver 7, 207, or other receiver
sized and shaped to receive the longitudinal connecting member 250,
to provide a more flexible dynamic stabilization than that provided
by the more rigid, uniform diameter longitudinal connecting members
20 or 220. The longitudinal connecting member 250 includes larger
diameter sections 252 and smaller diameter sections 254, the
sections 252 each having an axial length L of sufficient size to be
fully received within a receiver, such as the receiver 7 or 207.
The smaller diameter sections 254 may be of the same or varied
lengths, and same or varied diameters, sized to extend between bone
screw receivers of bone screws implanted to selected vertebra. In
the embodiment illustrated in FIG. 15, there are four larger
diameter sections 252 providing for the attachment of up to four
bone screws or other bone anchors along a portion of a spine at
varied distances corresponding to the various axial lengths-of the
smaller diameter sections 254. The longitudinal connecting member
250 may be made from a single piece of material and may include
annular tapered portions 256, providing a diagonal bridge between
each of the smaller diameter sections 254 and adjacent larger
diameter sections 252. If circumstances require change-out to a
more rigid, uniform diameter longitudinal connecting member, the
longitudinal connecting member 250 may be removed from cooperating
bone screws and a uniform diameter longitudinal connecting member,
such as the longitudinal connecting member 20 or the longitudinal
connecting member 220 may be inserted in the same receiver, making
unnecessary the removal or change-out of receivers described
previously herein with respect to the replacement of the
longitudinal connecting member 19 with the longitudinal connecting
member 20 or the longitudinal connecting member 219 with the
longitudinal connecting member 220. The smaller diameter sections
254 that are designed to extend between bone screws may be sized to
provide a more flexible, protected motion of the portions of the
spine being repaired.
[0125] The longitudinal connecting member 250 also may be made of
different materials (metal and non-metal) along the length thereof.
For example, with respect to FIG. 15, one of the sections 254A may
be made of a material exhibiting greater stiffness than the other
sections 254 of similar (or varied) diameter. This would result in
variable stiffness or flexibility along different segments or
sections of the member 250. For example, a composite rod is
possible, with the segment or section 254A made of a material with
greater stiffness for promoting fusion (such as a metallic rod) and
one or more connected or adjacent segments 254 of a different, more
flexible material (such as a plastic or different metallic rod or
non-uniform section as described in greater detail below with
respect to FIGS. 16-43), could be used to provide protected
movement of the one or more segments 254 that are connected to the
segment 254A. The segments 254 and 254A may be attached to the
sections 252 in a variety of ways, including, but not limited to
fusing, welding, molding, casting, forging or other forms of
adhering attachment to result in an integral relationship between
the sections and/or segments. It is also foreseen that longitudinal
connecting member portions of the same diameter, but made of
different materials (different metals, different non-metals and
combination of metal and non-metal) may be bonded, braided, molded,
fused or otherwise adhered to one another, to result in an integral
relationship therebetween. For example, a stiffer longitudinal
connecting member portion made from a first material may be used
for promoting fusion with the spine along a first selected length
of the connecting member, while a more flexible, compressible and
stretchable longitudinal connecting portion made from a second
material, integral with the first portion, may be used to provide
protected movement of the spine along a second selected length of
the connecting member.
[0126] As previously discussed herein, a concern that arises in
non-fusion dynamic stabilization procedures is the fatigue strength
and thus the longevity of longitudinal connecting members and other
structural members used in such procedures. In the apparatus and
methods described thus far herein, the more flexible longitudinal
connecting members 19, 219 and 250 may be changed out, when need
arises, and replaced with identical replacement longitudinal
connecting members 19, 219 or 250, respectively; with a more rigid
longitudinal connecting member 20 or 220; or with a composite
connecting member made from two or more different materials along a
length thereof. Further embodiments according to the invention are
shown in FIGS. 16-43 that include non-uniform portions that have an
increased cross-sectional area. Increasing cross-sectional area
increases fatigue strength and may further increase flexibility, at
least in certain directions, thus providing some longevity to such
longitudinal connecting members as well as increased protected
motion of portions of the spine stabilized by such longitudinal
connecting members in a non-fusion procedure. Such connecting
members that include non-uniform portions, may also include
portions made with different materials, e.g., a composite rod
consisting, for example, of metallic and non-metallic
materials.
[0127] With reference to FIGS. 16-19, a second non-uniform
longitudinal connecting member embodiment for use in apparatus and
methods of the invention, generally 260 includes at least first and
second uniform diameter cylindrical segments or portions 262 and
264, and at least one non-uniform portion or segment 266. The
portions, 262, 264 and 266 are integral and substantially coaxial.
In the illustrated embodiment the portion 262 has a diameter equal
to a diameter of the portion 264; however, it is foreseen that
portions 262 and 264 may have different diameters and
cross-sectional shapes. The portions 262 and 264 are each
receivable in a bone screw receiver, such as the receivers 6, 7,
206 and 207 previously described herein. The non-uniform portion
266 is designed for placement between bone screw receivers and is
solid and substantially cuboid or parallelepiped in form, having a
pair of substantially parallel surfaces 268 and a pair of
substantially parallel grooved surfaces 270 disposed substantially
perpendicular to the surfaces 268. A width or thickness of the
portion 266 measured along an entire length of the surface 270
running between the parallel surfaces 268 is larger than the
diameter of either of the uniform portions 262 and 264. A width or
thickness of the portion 266 measured between the surfaces 270 is
approximately equal to the diameter of the uniform portions 262 and
264. Each surface 270 includes a pair of open U-shaped grooves 272
running along an entire length thereof in a direction perpendicular
to a longitudinal axis of the connecting member 260. A thinning of
the portion 266 provided by the grooves 272, allows for increased
flexing of the connecting member 260 at the non-uniform portion 266
as compared to the uniform portions 262 and 264. Also, because of
the increased width measured between the surfaces 266, the
non-uniform portion 266 is of increased cross-sectional area as
compared to the uniform portions 262 and 264, providing for
improved fatigue strength at the grooves 272. With reference to
FIG. 18, a bone screw shank 4 and pivotally attached receiver 7 are
shown schematically in phantom to provide a reference as to how the
connecting member 260 is oriented with respect to such bone screw
assembly when implanted in a vertebra. Although only one
non-uniform portion 266 is shown in the drawing figures, it is
foreseen that a plurality of portions 266 may be disposed on the
connecting member 260, similar to what is shown, for example, with
respect to a connecting member embodiment illustrated in FIG. 45 to
be discussed in greater detail below.
[0128] With reference to FIGS. 20-22, a third non-uniform
longitudinal connecting member embodiment for use in apparatus and
methods of the invention, generally 280 includes at least first and
second uniform diameter cylindrical segments or portions 282 and
284, and at least one non-uniform portion or segment 286. The
portions 282, 284 and 286 are integral and substantially coaxial.
In the illustrated embodiment the portion 282 has a diameter equal
to a diameter of the portion 284; however, it is foreseen that
portions 282 and 284 may have different diameters. The portions 282
and 284 are each receivable in a bone screw receiver, such as the
receivers 6, 7, 206 and 207 previously described herein. The
non-uniform portion 286 is designed for placement between bone
screw receivers and is substantially solid and somewhat cuboid or
parallelepiped in form, having a pair of substantially parallel
surfaces 288 and a pair of substantially parallel surfaces 290
disposed substantially perpendicular to the surfaces 288 with a C-
or U-shaped groove 292 carved into a substantial portion of each of
the surfaces 290. A width or thickness of the portion 286 measured
along an entire length of the surface 290 running between the
parallel surfaces 288 is larger than the diameter of either of the
uniform portions 282 and 284. A width or thickness of the portion
286 measured between the surfaces 290 is approximately equal to the
diameter of the uniform portions 282 and 284. The groove 292 on
each surface 290 runs along an entire length thereof in a direction
perpendicular to a longitudinal axis of the connecting member 280.
A thinning of the portion 286 caused by the grooves 292, allows for
increased flexing of the connecting member 280 at the non-uniform
portion 286 as compared to the uniform portions 282 and 284. Also,
because of the increased width measured between the surfaces 288,
the non-uniform portion 286 is of increased cross-sectional area as
compared to the uniform portions 282 and 284, providing for
improved fatigue strength at the grooves 292. With reference to
FIG. 22, a bone screw shank 4 and pivotally attached receiver 7 are
shown schematically in phantom to provide a reference as to how the
connecting member 280 is oriented with respect to such bone screw
assembly when implanted in a vertebra. Although only one
non-uniform portion 286 is shown in the drawing figures, it is
foreseen that a plurality of portions 286 may be disposed on the
connecting member 280, similar to what is shown, for example, with
respect to a connecting member embodiment illustrated in FIG.
45.
[0129] With reference to FIGS. 23-25, a fourth non-uniform
longitudinal connecting member embodiment for use in apparatus and
methods of the invention, generally 300 includes at least first and
second uniform diameter cylindrical segments or portions 302 and
304, and at least one non-uniform portion or segment 306. The
portions 302, 304 and 306 are integral and substantially coaxial.
In the illustrated embodiment the portion 302 has a diameter equal
to a diameter of the portion 304; however, it is foreseen that
portions 302 and 304 may have different diameters. The portions 302
and 304 are each receivable in a bone screw receiver, such as the
receivers 6, 7, 206 and 207 previously described herein. The
non-uniform portion 306 is designed for placement between bone
screw receivers and is somewhat cuboid or parallelepiped in form,
having a pair of substantially parallel surfaces 308 and a pair of
substantially parallel surfaces 310 disposed substantially
perpendicular to the surfaces 308 with an aperture or through bore
312 extending between the surfaces 310, hollowing out a substantial
part of the non-uniform portion 306. A width or thickness of the
portion 306 measured along an entire length of the surface 310
running between the surfaces 308 is larger than the diameter of
either of the uniform portions 282 and 284. A width or thickness of
the portion 306 measured between the surfaces 310 is approximately
equal to the diameter of the uniform portions 302 and 304. The
through bore 312 runs parallel to the surfaces 308 in a direction
perpendicular to a longitudinal axis of the connecting member 300.
The hollowing out of the portion 306 caused by the bore 302, allows
for compression and extension of the connecting member 300 at the
non-uniform portion 306. Furthermore, at either side of the portion
306 are tapered necks 314, each having a diameter smaller than the
diameter of the uniform portions 302 and 304. The tapered necks 314
provide space for deformation of the portion 306 when under
compression and further provide for some flexibility or bending
movement as compared to the uniform portions 302 and 304. With
reference to FIG. 24, a bone screw shank 4 and pivotally attached
receiver 7 are shown schematically in phantom to provide a
reference as to how the connecting member 260 may be oriented with
respect to such bone screw assembly when implanted in a vertebra.
However, it is noted that because the portion 306 allows for
compression and extension rather than bending, the portion 306 may
be oriented in other directions also, for example, with the
surfaces 310 rotated ninety degrees from what is shown in FIG. 24
with respect to the receiver 7. Although only one non-uniform
portion 306 is shown in the drawing figures, it is foreseen that a
plurality of portions 306 may be disposed on the connecting member
300, similar to what is shown, for example, with respect to a
connecting member embodiment illustrated in FIG. 45.
[0130] With reference to FIGS. 26-28, a fifth non-uniform
longitudinal connecting member embodiment for use in apparatus and
methods of the invention, generally 320 includes at least first and
second uniform diameter cylindrical segments or portions 322 and
324, and at least one non-uniform portion or segment 326. The
portions 322, 324 and 326 are integral and substantially coaxial.
In the illustrated embodiment the portion 322 has a diameter equal
to a diameter of the portion 324; however, it is foreseen that
portions 322 and 324 may have different diameters. The portions 322
and 324 are each receivable in a bone screw receiver, such as the
receivers 6, 7, 206 and 207 previously described herein. The
non-uniform portion 326 is designed for placement between bone
screw receivers and is substantially solid and cuboid or
parallelepiped in form, having a pair of substantially parallel
surfaces 328 and a pair of substantially parallel surfaces 330
disposed substantially perpendicular to the surfaces 328. A width
or thickness of the portion 326 measured along an entire length of
the surface 330 running between the parallel surfaces 328 is larger
than the diameter of either of the uniform portions 322 and 324. A
width or thickness of the portion 326 measured between the surfaces
330 is smaller than the diameter of the uniform portions 322 and
324, thus providing for increased flexing of the connecting member
320 at the non-uniform portion 326 as compared to the uniform
portions 322 and 324. Also, because of the increased width measured
between the surfaces 328, the non-uniform portion 326 is of
increased cross-sectional area as compared to the uniform portions
322 and 324, providing for improved fatigue strength as the portion
326 bends at the surfaces 330. With reference to FIG. 28, a bone
screw shank 4 and pivotally attached receiver 7 are shown
schematically in phantom to provide a reference as to how the
connecting member 320 is oriented with respect to such bone screw
assembly when implanted in a vertebra. Although only one
non-uniform portion 326 is shown in the drawing figures, it is
foreseen that a plurality of portions 326 may be disposed on the
connecting member 320, similar to what is shown, for example, with
respect to a connecting member embodiment illustrated in FIG.
45.
[0131] With reference to FIGS. 29-32, a sixth non-uniform
longitudinal connecting member embodiment for use in apparatus and
methods of the invention, generally 340 includes at least first and
second uniform diameter cylindrical segments or portions 342 and
344, and at least one non-uniform portion or segment 346. The
portions 342, 344 and 346 are integral and substantially coaxial.
In the illustrated embodiment the portion 342 has a diameter equal
to a diameter of the portion 344; however, it is foreseen that
portions 342 and 344 may have different diameters. The portions 342
and 344 are each receivable in a bone screw receiver, such as the
receivers 6, 7, 206 and 207 previously described herein. The
non-uniform portion 346 is designed for placement between bone
screw receivers and is substantially solid, having a pair of
surfaces 348 that curve outwardly oppositely in one plane and a
pair of substantially parallel surfaces 350 disposed substantially
perpendicular to the surfaces 348. Relatively flat, sloping
triangular surfaces 352 extend between the uniform portions 342 and
344 and the flat surfaces 350. Curved surfaces 352 slope outwardly
from the cylindrical portions 342 and 344 to the curved surfaces
348. A width or thickness of the portion 346 measured along a
length of the surface 350 running between the curved surfaces 348
is larger than the diameter of either of the uniform portions 342
and 344. A width or thickness of the portion 346 measured between
the surfaces 350 is smaller than the diameter of the uniform
portions 342 and 344, thus providing for increased flexing of the
connecting member 340 at the non-uniform portion 346 as compared to
the uniform portions 342 and 344. Also, because of the increased
width measured between the surfaces 348, the non-uniform portion
346 is of increased cross-sectional area as compared to the uniform
portions 342 and 344, providing for improved fatigue strength as
the portion 346 bends at the surfaces 350. With reference to FIG.
31, a bone screw shank 4 and pivotally attached receiver 7 are
shown schematically in phantom to provide a reference as to how the
connecting member 340 is oriented with respect to such bone screw
assembly when implanted in a vertebra. Although only one
non-uniform portion 346 is shown in the drawing figures, it is
foreseen that a plurality of portions 346 may be disposed on the
connecting member 340, similar to what is shown, for example, with
respect to a connecting member embodiment illustrated in FIG.
45.
[0132] With reference to FIGS. 33-35, a seventh non-uniform
longitudinal connecting member embodiment for use in apparatus and
methods of the invention, generally 360 includes at least first and
second uniform diameter cylindrical segments or portions 362 and
364, and at least one non-uniform portion or segment 366. The
portions 362, 364 and 366 are integral and substantially coaxial.
It is noted that the longitudinal connecting member 360 is somewhat
curved in form rather than following a straight longitudinal axis.
Any or all of the connecting members described herein may be
straight or curved, depending upon requirements and desired outcome
of a particular surgical application. In the illustrated embodiment
the portion 362 has a diameter equal to a diameter of the portion
364; however, it is foreseen that portions 362 and 364 may have
different diameters. The portions 362 and 364 are each receivable
in a bone screw receiver, such as the receivers 6, 7, 206 and 207
previously described herein. The non-uniform portion 366 is
designed for placement between bone screw receivers and is
substantially solid, having a pair of surfaces 368 that curve
outwardly oppositely and a pair of substantially parallel surfaces
370 disposed substantially perpendicular to the surfaces 368. A
pair of oppositely oriented ribs or ridges 371 are located
centrally on the surfaces 370 and extend between the curved
surfaces 368. Relatively flat, sloping triangular surfaces 372
extend between the uniform portions 362 and 364 and the flat
surfaces 370. Curved surfaces 372 slope outwardly from the
cylindrical portions 362 and 364 to the curved surfaces 368. A
width or thickness of the portion 366 measured along a length of
the surface 370 running between the curved surfaces 368 is larger
than the diameter of either of the uniform portions 362 and 364. A
width or thickness of the portion 366 measured between the surfaces
370 is smaller than the diameter of the uniform portions 362 and
364, thus providing for increased flexing of the connecting member
360 at the non-uniform portion 366 as compared to the uniform
portions 362 and 364. Also, because of the increased width measured
between the surfaces 368, the non-uniform portion 366 is of
increased cross-sectional area as compared to the uniform portions
362 and 364, providing for improved fatigue strength as the portion
366 bends at the surfaces 360, the rib 371 also providing
additional stability. With reference to FIG. 35, a bone screw shank
4 and pivotally attached receiver 7 are shown schematically in
phantom to provide a reference as to how the connecting member 360
is oriented with respect to such bone screw assembly when implanted
in a vertebra. Although only one non-uniform portion 366 is shown
in the drawing figures, it is foreseen that a plurality of portions
366 may be disposed on the connecting member 360, similar to what
is shown, for example, with respect to a connecting member
embodiment illustrated in FIG. 45.
[0133] With further reference to FIG. 35, a longitudinal connecting
member portion, length or segment 364A may also be made from a
different material than a remainder length of the connecting member
360, resulting in a composite connecting member that varies in
flexibility along the length of the entire longitudinal connecting
member. For example, similar to what was described previously
herein with respect to the segment 254A of the connecting member
250 illustrated in FIG. 15, the section, length or segment 364A may
be made of a material of greater stiffness than an adjacent section
364 disposed on an opposite side of the bone screw shank 4, the
section 364A being formed, fused, welded or otherwise adhered to be
integral with the section 364, the stiffer section or segment 364A
for promoting fusion along a length of the section or segment 364A
between the illustrated implanted bone screw shank 4 and another
bone screw (not shown) spaced from the shank 4 that is also
attached to the section 364A. The segment 364A is preferably of a
length sufficient to be received between a pair of bone anchors. In
the illustrated embodiment, the sections or segments 362, 364, and
364A are of uniform cross-section, thus receivable in the
same-sized bone anchor. Furthermore, each of the segments may be
made from a substantially solid material.
[0134] With reference to FIGS. 36-38, an eighth non-uniform
longitudinal connecting member embodiment for use in apparatus and
methods of the invention, generally 380 includes at least first and
second uniform diameter cylindrical segments or portions 382 and
384, and at least one non-uniform cage-like portion or structure
386. The illustrated portions 382, 384 and 386 are integral and
substantially coaxial. In the illustrated embodiment the portion
382 has a diameter equal to a diameter of the portion 384; however,
it is foreseen that portions 382 and 384 may have different
diameters. Furthermore, the portions 382, 384 and 386 may be made
from different materials exhibiting different levels of stiffness
or flexibility. The portions 382 and 384 are each receivable in a
bone screw receiver, such as the receivers 6, 7, 206 and 207
previously described herein and similar to what is shown in FIG.
47. The non-uniform portion 386 is designed for placement between
bone screw receivers and is substantially hollow, having a pair of
substantially parallel sides 388, each side disposed substantially
perpendicular to a longitudinal axis of the connecting member 380.
Extending between and connecting the sides 388 are a plurality of
strip-like segments or panels 390. Each of the segments 390 are
integral with the sides 388, the portion 386 as well as the uniform
portions 382 and 384 preferably being machined from a single piece
of metal or non-metallic material. Although not shown in FIGS.
36-38, the structure 386 is hollowed out in a manner identical to
that illustrated in FIGS. 41 and 44 for similar cage-like
structures to be discussed in more detail below. The segments 390
are substantially U- or C-shaped and are uniformly spaced with
respect to the longitudinal axis of the connecting member 380,
forming a cage-like structure that is both compressible and
expandable with openings between each of the segments 390. The
compression and expansion occurs primarily at the U-shaped segments
390, but the sides 388 also move toward and away from one another
in response to compression and tension. As previously stated, when
in a neutral state or position (no compression and no expansion),
the sides 388 of the structure 386 are substantially parallel. When
the structure 386 is under tension and thus stretched, the
structure 386 becomes somewhat ellipsoid in form. When compressed,
the sides 388 are pressed toward one another, narrowing a width
between legs of the U-shaped segments 390 and moving the segments
390 slightly radially outwardly. In the embodiment illustrated in
FIGS. 36-38, there are eight segments 390, generally disposed at
every 45 degrees as best shown in FIG. 38. At either side 388 of
the cage-like structure 386 are tapered neck portions 392 that
connect the structure 386 with the uniform portions 382 and 384.
When the structure 386 is compressed due to movement of the uniform
portions 382 and 384 toward one another, the neck portions move
toward and into the structure 386, causing the sides 388 to move
outwardly toward the uniform portions 382 and 384. The neck
portions 392 of reduced diameter provide a relief or space for the
sides 388 and the U-shaped segments 390 to move into, allowing for
slightly increased movement of the connector 380 in an axial
direction during compression. Although only one non-uniform portion
386 is shown in the drawing figures, it is foreseen that a
plurality of portions 386 may be disposed on the connecting member
380, similar to what is shown, for example, with respect to a
connecting member embodiment illustrated in FIG. 45. It is also
noted that the non-uniform portion or portions of this and other
longitudinal connecting member embodiments described herein may be
sheathed, coated or otherwise covered by an inner or outer sleeve
made from plastic or other flexible material so that bone and soft
tissue growth does not occur between the portion segments that
would inhibit the flexibility of the non-uniform portion.
[0135] With reference to FIGS. 39-41, a ninth non-uniform
longitudinal connecting member embodiment for use in apparatus and
methods of the invention, generally 400 is substantially similar in
structure and function to the connecting member 380 previously
described herein and thus the discussion of the connecting member
380 is incorporated by reference herein with respect to the
connecting member 400. The connecting member 400 includes at least
first and second uniform diameter cylindrical segments or portions
402 and 404, and at least one non-uniform cage-like portion or
structure 406. The portions 402, 404 and 406 are integral and
substantially coaxial, with the portion 406 being hollow as
illustrated in FIG. 41. The non-uniform portion 406 is designed for
placement between bone screw receivers and is substantially similar
to the portion 386, having a pair of substantially parallel sides
408, similar to the sides 388 and a plurality of U-shaped segments
410 connecting the sides 408, the segments 410 similar to the
segments 390 with the exception that the segments 410 further
include a slit or slot 412 disposed centrally in each segment 410
and extending from one side 408 to the other side 408. The slits
412 thus dividing each segment 410 into two strips 414 and 415,
providing for increased compression and extension of the cage-like
structure 406.
[0136] FIG. 45 illustrates two cage-like structures 406 mounted on
a longitudinal connector, generally 416. FIG. 47 further shows the
longitudinal connecting member 416 attached to a mono-axial or
fixed bone screw 417. The bone screw 417 is discussed in detail in
U.S. Pat. No. 6,726,687, incorporated by reference herein. In
addition to what is described in U.S. Pat. No. 6,726,687, to
provide a biologically active interface with the bone, the bone
screw 417 includes a treated shank body 418 (illustrated as
speckling on FIGS. 46 and 47). The shank body 418 treatment may
include, but is not limited to a plasma spray coating, a
hydroxyapatite (HA) coating, or other type of roughening,
perforation or indentation in the surface 418, such as by
sputtering, sand blasting or acid etching, that allows for bony on
growth and ingrowth.
[0137] Although the longitudinal connecting member 416 is shown
with the fixed bone screw 417, it is noted that the connector 416
and all other longitudinal connecting members 19, 20, 250, 260,
280, 300, 320, 340, 360, 380, 400 and 420 described in this
application may be received in a variety of open bone screws,
including, but not limited to, polyaxial, hinged and fixed bone
screws as well as hooks and other types of bone anchors. It is
further noted that all of the longitudinal connecting members
described in this application may be made from metal or
non-metallic materials as well as composites of such materials.
[0138] With reference to FIGS. 42-44, a tenth non-uniform
longitudinal connecting member embodiment for use in apparatus and
methods of the invention, generally 420 is substantially similar in
structure and function to the connecting members 380 and 400
previously described herein and thus the discussion of the
connecting members 380 and 400 are incorporated by reference herein
with respect to the connecting member 420. The connecting member
420 includes at least first and second uniform diameter cylindrical
segments or portions 422 and 424, and at least one non-uniform
cage-like portion or structure 426. The portions 422, 424 and 426
are integral and substantially coaxial, with the portion 426 being
hollow as illustrated in FIG. 44. The non-uniform portion 426 is
designed for placement between bone screw receivers and is
substantially similar to the portion 406, having a pair of
substantially parallel sides 428, similar to the sides 408 and a
plurality of U-shaped segments 430 connecting the sides 428, the
segments 430 similar to the segments 390 and 410 with the exception
that the segments 430 each include two slits or slots 432 one
disposed in each side 428 and running into the segment 430, but not
completely therethrough. Each slit 432 terminating at a central
portion 434 of each segment 430, providing an area of additional
strength when the segment 430 bends due to compressive forces.
[0139] It is to be understood that while certain forms of the
present invention have been illustrated and described herein, it is
not to be limited to the specific forms or arrangement of parts
described and shown.
* * * * *