U.S. patent application number 14/687231 was filed with the patent office on 2015-08-06 for composite spinal rod.
The applicant listed for this patent is STRYKER EUROPEAN HOLDINGS I, LLC. Invention is credited to Hyun Bae, Charanpreet S. Bagga.
Application Number | 20150216569 14/687231 |
Document ID | / |
Family ID | 41316876 |
Filed Date | 2015-08-06 |
United States Patent
Application |
20150216569 |
Kind Code |
A1 |
Bae; Hyun ; et al. |
August 6, 2015 |
COMPOSITE SPINAL ROD
Abstract
A spinal rod including an elongated flexible component and a
reinforcing component, the reinforcing component being resistant to
damage from compressive forces and disposed circumferentially
around at least a portion of the flexible component so as to define
at least one compression slot.
Inventors: |
Bae; Hyun; (Santa Monica,
CA) ; Bagga; Charanpreet S.; (Basking Ridge,
NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
STRYKER EUROPEAN HOLDINGS I, LLC |
Kalamazoo |
MI |
US |
|
|
Family ID: |
41316876 |
Appl. No.: |
14/687231 |
Filed: |
April 15, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12454187 |
May 13, 2009 |
9017384 |
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14687231 |
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61053001 |
May 13, 2008 |
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Current U.S.
Class: |
606/255 |
Current CPC
Class: |
A61B 17/7028 20130101;
A61B 17/7031 20130101; A61B 17/701 20130101; A61B 17/7005 20130101;
A61B 17/7026 20130101; A61B 17/7014 20130101 |
International
Class: |
A61B 17/70 20060101
A61B017/70 |
Claims
1. (canceled)
2. A spinal rod, comprising: an elongated flexible component having
an outer surface and extending along a first longitudinal axis; and
a plurality of elongated reinforcing components each extending
along a respective second longitudinal axis and each at least
partially exposed at the outer surface of the flexible component,
the second longitudinal axes of the reinforcing components being
parallel to the first longitudinal axis of the flexible component,
and the reinforcing components forming a circumferential
arrangement around the first longitudinal axis of the flexible
component.
3. The spinal rod of claim 2, wherein the reinforcing components
are asymmetrically circumferentially arranged around the first
longitudinal axis of the flexible component.
4. The spinal rod of claim 2, further comprising two or more
collars disposed around the flexible component uniformly along the
first longitudinal axis of the flexible component.
5. The spinal rod of claim 4, wherein the two or more collars
extend outward from the outer surface of the flexible component,
each of the two or more collars having beveled edges that contact
the flexible component.
6. The spinal rod of claim 4, wherein an external diameter of the
flexible component is smaller than an internal diameter of each of
the two or more collars.
7. The spinal rod of claim 2, wherein an embedded portion of at
least one of the reinforcing components includes retention elements
configured to resist outward movement of the reinforcing component
with respect to the flexible member.
8. The spinal rod of claim 2, wherein a perimeter of a
cross-section of the spinal rod varies along a length of the spinal
rod.
9. The spinal rod of claim 2, wherein a perimeter of a
cross-section of the flexible component is uniform along a length
of the spinal rod, and the flexibility of the flexible component
varies along the length of the spinal rod.
10. The spinal rod of claim 2, wherein the flexible component is
comprised of at least one of PEEK and carbon fiber reinforced PEEK,
and the reinforcing component is comprised of at least one of
titanium, titanium alloy, another metal, and ceramic.
11. The spinal rod of claim 10, wherein the flexible component
includes carbon fibers circumferentially wound around the first
longitudinal axis of the flexible component.
12. The spinal rod of claim 2, wherein a maximum length of the
elongated flexible component along the first longitudinal axis
thereof is substantially equal to a maximum length of each of the
plurality of elongated reinforcing components along the respective
second longitudinal axes thereof.
13. A method for connecting and stabilizing adjacent vertebrae, the
method comprising: connecting at least two pedicle screws to
adjacent vertebrae; and connecting the spinal rod of claim 2 to the
pedicle screws.
14. A kit for use in connecting and stabilizing adjacent vertebrae,
the kit comprising: the spinal rod of claim 2; at least one pedicle
screw.
15. The kit of claim 14, wherein the at least one spinal rod is
multiple spinal rods and the at least one pedicle screw is multiple
pedicle screws, the kit further comprising at least one instrument
or tool associated with the use of the spinal rods and the pedicle
screws.
16. A spinal rod, comprising: an elongated flexible component
having an outer surface and extending along a longitudinal axis; a
reinforcing component at least partially exposed at the outer
surface of the flexible component; and a protective end cap
covering an end of the flexible component.
17. The spinal rod of claim 16, wherein the flexible component
includes an internally disposed closed spiral configuration at the
outer surface, and the reinforcing component is an open spiral
having a complementary shape and size to the infernally disposed
closed spiral configuration of the flexible component.
18. The spinal rod of claim 16, wherein the reinforcing component
is a flat metal spring disposed within a complementary shaped
groove in the outer surface of the flexible component.
19. The spinal rod of claim 16, wherein the reinforcing component
is a protective mesh circumferentially disposed around the flexible
component.
20. A spinal rod, comprising: a first elongated flexible component
having an outer surface and extending along a longitudinal axis; a
second elongated flexible component having an outer surface and
extending along a longitudinal axis; and a reinforcing component at
least partially exposed at the outer surface of the first and
second flexible components and configured to connect the first and
second flexible components together.
21. The spinal rod of claim 20, wherein the reinforcing component
includes at least two pins, each of the pins being disposed through
a different one of the first and second flexible components.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S. patent
application Ser. No. 12/454,187, filed on May 13, 2009, which
claims the benefit of the filing date of U.S. Provisional Patent
Application No. 61/053,001 filed May 13, 2008, the disclosures of
which are hereby incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present technology relates to orthopedic surgery. In
particular, the present technology relates to a spinal rod formed
of a reinforcing component and a flexible component so as to
provide a combination of flexibility, strength, and resistance to
localized compressive forces. More particularly, the present
technology provides a titanium and polyetheretherketone (PEEK)
composite rod that can be manufactured in a variety of
configurations designed to provide different degrees of flexibility
and stiffness as desired.
BACKGROUND OF THE INVENTION
[0003] Spinal or vertebral rods are often used in the surgical
treatment of spinal disorders such as degenerative disc disease,
disc herniation, scoliosis or other curvature abnormalities or
fractures. Spinal rods, which may be mechanically anchored to
sequentially aligned pedicle screw assemblies connected to
vertebral bodies, serve to provide rigidity to portions of the
spinal column to encourage the vertebral bodies to fuse after
spinal-fusion surgery. Fusion results in the permanent
immobilization of one or more of the intervertebral joints between
vertebral bodies. To achieve spinal fusion the spinal rods selected
are typically uniform along the entire length of the rod and
manufactured from a single or integral piece of relatively
inflexible material having a uniform diameter and sized to provide
substantially rigid support to the spinal construct.
[0004] Fusion, however, can have some very undesirable side
effects. Spinal fusion by design results in immobilization of a
portion of the spine and thus can severely limit the natural motion
of the subject. Further, although fusion can result in a
strengthened portion of the spine, it may also result in more rapid
degeneration and even hyper-mobility and collapse of other portions
of the spine that are adjacent to the portion of the spine being
fused.
[0005] An alternative to the use of rigid spinal rods is the use of
flexible or dynamic spinal rods to create a more normal loading
pattern in flexion, extension, distraction, compression, side
bending and torsion. The efforts to provide a dynamic spinal rod
conventionally involve the use of flexible materials that are
capable of providing the needed bending and twisting dynamics, but
these materials can lack the necessary strength to avoid the damage
that can result from the compressive forces of bone screw
attachments to the spinal rods.
[0006] Recent attempts to provide dynamic spinal rods typically
include the use of a rod formed of flexible plastic material, such
as polyurethane, UHMW polyethylene, PEEK or Teflon. Efforts to
include a measured degree of reinforcement to such flexible rods
have employed longitudinally aligned reinforcing components that
extend internally through the length of the flexible rods, the
reinforcing components being formed of materials such as Kevlar,
polyethylene, polyurethane, Teflon fiber, carbon fiber, or
stainless steel. Common to all current attempts to provide a
flexible spinal rod is the potential failure of such rods to
provide flexibility while being sufficiently strong and resistant
to the damaging compressive forces of attached bone screws.
[0007] There exists therefore a need to provide a flexible spinal
rod that is capable of being secured with conventional bone screws
without being susceptible to damage from the compressive forces at
the attachment point of the bone screws.
BRIEF SUMMARY OF THE INVENTION
[0008] The present technology meets the above identified need by
providing a spinal rod that may be sufficiently flexible to provide
a dynamic connecting rod between adjacent vertebrae while
maintaining sufficient surface strength to avoid damage from the
normal compressive forces associated with the attachment of bone
screws to the rod.
[0009] Also provided is a spinal rod having a composite
construction that may include flexible materials allowing for
dynamic control of the spine and may also include compressive force
resistant materials that are sufficiently provided in the composite
rod at the surface of the rod so as to be the contact point for any
attachments or bone screws.
[0010] Also provided is a spinal rod of composite construction that
may include a flexible material component and an embedded
reinforcing component disposed at least partially on the surface of
the spinal rod at points where bone screws can be attached. The
flexible component may be a material such as PEEK and the
reinforcing component material may be a metallic compression
resistant material such as titanium.
[0011] Also provided is a composite construction spinal rod wherein
compressive forces applied to the surface of the rod may be
transferred transversely through the rod by compressive force
resistant reinforcing materials so as to protect the flexible
component of the rod from damage.
[0012] Also provided is a spinal rod having a flexible core
material with embedded compression resistant reinforcing components
at least partially exposed on the surface of the spinal rod at
locations for bone screw attachment. The reinforcing components may
extend transversely through the flexible core so as to connect the
surfaced exposed reinforcing material on one side of the spinal rod
to the surface exposed reinforcing material on at least one other
side of the spinal rod.
[0013] Also provided is a spinal rod constructed of a combination
of a flexible component and a reinforcing component, wherein the
reinforcing component may be provided at multiple levels of the
spinal construct.
[0014] Also provided is a spinal rod constructed of a combination
of a flexible component and a reinforcing component, wherein the
flexible component may be manufactured to have a selected gradient
flexibility along the length of the spinal rod.
[0015] Also provided is a spinal rod constructed of a combination
of a flexible component and a reinforcing component, wherein the
reinforcing component may be configured to also provide a
connecting function between two separate flexible rod components
aligned end to end, the two separate flexible rod components being
of the same construction or of different construction and thereby
having the same flexibility or different flexibilities one to the
other.
[0016] Also provided is a spinal rod with reinforcing components
exposed on at least a portion of the surface of the flexible
component and connecting pins extending transversely through the
flexible component core so as to closely approach but not directly
contact the undersurface of at least one of the opposing surface
exposed reinforcing components to define a compression space
therebetween. Thus, compressive forces on one of the surface
exposed reinforcing components may first serve to close the
compression space and cause contact of that reinforcing component
to the underlying connecting pin so as to transfer the compressive
force through the connecting pin to the reinforcing component on
the opposing side of the rod.
[0017] Also provided is a method of implanting a spinal construct
that allows a degree of flexibility and controlled motion between
adjacent vertebrae while maintaining sufficient strength on the
surface of the spinal connecting rod to avoid damage from the
compressive forces exerted by conventional bone screw
attachments.
[0018] Also provided is a kit containing at least one spinal rod
having both flexible characteristics and surface strength needed to
avoid damage from the externally applied compressive forces and at
least two bone screws.
[0019] One aspect of the technology provides a spinal rod including
an elongated flexible component and a reinforcing component, the
reinforcing component being resistant to damage from compressive
forces. The reinforcing component may be disposed circumferentially
around at least a portion of the flexible component so as to define
at least one compression slot.
[0020] In one embodiment, the spinal rod reinforcing element of the
spinal rod may be disposed circumferentially around at least a
portion of the flexible component so as to define a space between
the flexible component and the reinforcing component. Furthermore,
the reinforcing component may include a screw contact surface
configured to facilitate contact with an attachment. The contact
surface may be treated so as to facilitate contact with a pedicle
screw.
[0021] In addition, the reinforcing component of the spinal rod may
be at least two separate reinforcing elements and may be at least
partially embedded in the surface of the flexible component.
Furthermore, the flexible component may have a gradient of
flexibility along at least a portion of its length. In addition or
alternatively, the flexible component may have a plurality of
sections where the flexibility of one section differs from the
flexibility of at least one other section.
[0022] Another aspect of the technology provides a spinal rod that
includes an elongated flexible component and a reinforcing
component, where the reinforcing component being resistant to
damage from compressive forces. In addition, the reinforcing
element may comprise an upper bracket, an opposing lower bracket,
and a connecting pin extending therebetween.
[0023] In one embodiment, the connecting pin may be disposed
transversely through the flexible component, each end of the
connecting pin being directed toward the upper bracket or the lower
bracket, with at least one of the upper bracket and the connecting
pin or the lower bracket and the connecting pin defining a
compression space. Furthermore, at least one of the upper bracket
and the lower bracket may be at least partially embedded in the
surface of the flexible component.
[0024] In a further embodiment, at least one edge of the upper and
lower bracket may be tapered, and the tapered edge may create a
gradient of compressive stress shielding for the underlying
flexible component. Furthermore, the flexible component may have a
gradient of flexibility along at least a portion of its length.
Still further, the reinforcing component may be at least two
separate reinforcing elements and the flexible component may have a
plurality of sections, where the flexibility of one section differs
from the flexibility of at least one other section.
[0025] A further aspect of the present technology provides a method
for connecting and stabilizing adjacent vertebrae, the method
including the steps of providing the a spinal rod of the present
technology, providing a surgical field of view for insertion of the
spinal rod, and connecting the spinal rod to adjacent vertebrae.
Furthermore, the connecting step may further include connecting
pedicle screws to vertebrae and connecting the pedicle screws to
the spinal rod. The pedicle screws may be connected to the spinal
rod at a position on the spinal rod where compressive forces
imposed by the pedicle screws on the spinal rod are transferred via
the reinforcing component transversely across the flexible
component, wherein the reinforcing component provides stress
shielding for the flexible component.
[0026] Yet another aspect of the present technology provides a kit
for use in connecting and stabilizing adjacent vertebrae, the kit
including at least one spinal rod according to the present
technology and at least one pedicle screw. In the kit, the at least
one spinal rod may be multiple spinal rods and the at least one
pedicle screw may be multiple pedicle screws. In addition, the kit
may further include at least one instrument or tool associated with
the use of the spinal rods and the pedicle screws.
[0027] An alternative embodiment of the present technology provides
a spinal rod, the spinal rod including an elongated flexible
component and a reinforcing component, the reinforcing component
being resistant to damage from compressive forces. Furthermore, a
portion of the reinforcing component may be circumferentially
disposed on the surface of the flexible component and a portion of
the reinforcing component may extend transversely through the
flexible component to connect opposing sides of the
circumferentially disposed reinforcing component one to the other,
wherein the reinforcing component is capable of stress shielding
the flexible component from compressive force damage by
transferring externally applied compressive forces transversely
across the elongated flexible component to the opposing side of the
spinal rod. This portion of the reinforcing component of this
embodiment may be multiple portions. In addition, the reinforcing
component may be configured as a plurality of circumferentially
disposed rings, at least one of the rings having multiple portions
extending transversely through the flexible component. Furthermore,
the multiple transversely extending portions may be symmetrically
disposed passing transversely through the flexible component.
Alternatively, the multiple transversely extending portions may be
asymmetrically and selectively disposed so as to make the spinal
rod capable of greater flexibility in selected planes of movement
of the flexible component.
[0028] Another embodiment of the present technology provides a
spinal rod including an elongated flexible component and a
reinforcing component, where the reinforcing component may be
resistant to damage from compressive forces and wherein the
reinforcing element is configured on the flexible component as a
circumferentially disposed spiral extending along at least a
portion of the elongated flexible component of the spinal rod.
[0029] Yet another embodiment provides a spinal rod including an
elongated flexible component and a reinforcing component, with the
reinforcing component being resistant to damage from compressive
forces and wherein the reinforcing component may be configured to
provide a protective end cap on at least one end of the elongated
flexible component.
[0030] Alternatively, an embodiment of the present technology may
provide a spinal rod including an elongated flexible component and
a reinforcing component, with the reinforcing component being
resistant to damage from compressive forces and wherein the
reinforcing component is configured as a plurality of elongated
reinforcing elements disposed on the surface of the elongated
flexible component and extending parallel to the longitudinal axis
of the elongated flexible component.
[0031] One embodiment of the present technology provides a spinal
rod including an elongated flexible component and a reinforcing
component, with the reinforcing component being resistant to damage
from compressive forces and wherein the flexible component
comprises a carbon fiber reinforcing structure. The carbon fiber
may be chopped or wound. Furthermore, the carbon fiber may be
selectively disposed in the flexible component so as to create a
gradient of flexibility in the elongated flexible component. The
selective disposition of carbon fiber may consist of increased or
decreased concentration of chopped carbon fibers, wherein portions
of the flexible component having increased chopped carbon fibers
may be stiff relative to portions of the flexible component having
decreased concentrations of carbon fibers. Furthermore, the
selective disposition of carbon fiber may be increased or decreased
numbers of winds of wound carbon fibers, wherein portions of the
flexible component having increased winds of carbon fibers may be
stiff relative to portions of the flexible component having
decreased winds of carbon fibers.
[0032] One embodiment of the present technology includes a spinal
rod, the spinal rod including an elongated flexible component and a
reinforcing component, the reinforcing component being resistant to
damage from compressive forces and comprising a mesh
circumferentially disposed on at least a portion of the surface of
the flexible component. In an alternative embodiment, the
reinforcing component may comprise a connecting bracket having an
upper bracket and an opposing lower bracket, the connecting bracket
being configured to connect two separate, longitudinally aligned
elongated flexible components to each other end-to-end.
[0033] In an alternative embodiment, the spinal rod may include an
elongated flexible component, a reinforcing component, and a
connecting bracket, the reinforcing component being resistant to
damage from compressive forces, and the connecting bracket
including at least two transversely disposed connecting pins, each
of the pins passing respectively through the flexible component of
a respective elongated flexible component of a separate spinal
rod.
[0034] In yet another embodiment, the spinal rod may have an
elongated flexible component and a reinforcing component, the
reinforcing component being resistant to damage from compressive
forces. In addition, the reinforcing component may be disposed
adjacent to at least a portion of the flexible component so as to
define at least one compression slot and the reinforcing element
may comprise an upper bracket, an opposing lower bracket, and a
connecting pin extending therebetween.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] The foregoing and other features of the disclosed technology
will become apparent to one skilled in the art to which the present
technology relates upon consideration of the following description
of exemplary embodiments with reference to the accompanying
drawings, wherein:
[0036] FIG. 1A shows the spinal rod having a flexible component
with a generally circular cross section and a plurality of
partially embedded rigid reinforcing components;
[0037] FIG. 1B shows the spinal rod of FIG. 1A having an
asymmetrical disposition of partially embedded rigid reinforcing
components;
[0038] FIG. 1C shows the spinal rod of FIG. 1A having concentric
reinforcing component connecting rings partially embedded at each
end of the elongate spinal rod;
[0039] FIG. 2A shows the spinal rod having a flexible component
with a generally circular cross section and a plurality of
partially embedded rigid reinforcing components disposed in a
generally uniform and parallel manner circumferentially along the
longitudinal axis of the rod. Also shown is an alternative element
of inwardly directed cross members that may bisect each of the
reinforcing component rings;
[0040] FIG. 2B shows the spinal rod having a similar construction
to that of FIG. 2A with the reinforcing rings elongated and
disposed along the longitudinal axis of the rod at select locations
where bone screw attachment is to be made. This configuration can
alternatively also include the element of inwardly directed cross
members described and shown in FIG. 2A;
[0041] FIG. 2C shows a variation of the spinal rod of FIG. 2B,
having reinforcing rings configured to be elevated above the
surface of the flexible portion of the spinal rod. Also shown is an
alternative element of a compression slit defined in the
reinforcing ring;
[0042] FIG. 2D shows the spinal rod of FIG. 2C wherein the elevated
reinforcing component ring is flattened on an upper surface to
facilitate contact with the locking set screw of a conventional
bone screw which may be attached at that position. Also shown is an
alternative element of a compression slit defined in the
reinforcing ring;
[0043] FIG. 3A shows a transparent isometric view of an alternative
configuration of the reinforcing component ring portion of the
spinal rod, the ring having at least one compression slit;
[0044] FIG. 3B shows the spinal rod with a plurality of the
reinforcing component rings configured as shown in FIG. 3A;
[0045] FIG. 3C shows an alternative flexible component of the
spinal rod that may be used in place of the flexible portion shown
in FIG. 3B;
[0046] FIG. 4A shows an alternative reinforcing component ring
portion of the spinal rod. The reinforcing component ring may be
provided with at least one compression slit and as shown may have a
flattened upper surface to facilitate contact with the locking set
screw of a conventional bone screw that may be attached at that
position.
[0047] FIG. 4B shows the alternative reinforcing component ring of
FIG. 4A partially embedded in a flexible component of the spinal
rod, the rod being configured to have a flattened upper surface and
a curved lower surface;
[0048] FIG. 4C shows an alternative configuration of the spinal rod
shown in FIG. 4B with the reinforcing component ring disposed in an
elevated position over the surface of the flexible portion of the
rod;
[0049] FIG. 4D shows an alternative configuration of the
reinforcing component ring wherein the upper and lower portions are
curved so as to conform to the curved upper and lower surfaces of
the flexible portion of the rod;
[0050] FIG. 4E-F show respectively an alternative reinforcing
component ring having upper and lower portions that are curved, the
upper curved portion being partially flattened to facilitate
attachment of a set screw locking a bone screw to the rod and, in
FIG. 4F, a pair of the same alternative reinforcing component rings
mounted in an elevated position over the surface of the flexible
portion of the rod;
[0051] FIG. 5 shows the use of rigid reinforcing components
positioned at multiple levels along the flexible portion of the
rod;
[0052] FIG. 6 shows the spinal rod having a flexible component that
has a gradient of flexibility along all or at least a portion of
its entire length;
[0053] FIG. 7 shows the spinal rod having an alternative embodiment
of the rigid reinforcing component, wherein the reinforcing
component is configured to serve as a connector between two
longitudinally aligned flexible components of a rod, the two
connected flexible components having the same or different degrees
of flexibility;
[0054] FIG. 8A-B show respectively a flexible portion and a
reinforcing component portion of an alternative embodiment of the
spinal rod, wherein the two portions are configured to have a
corresponding spiral slit and spiral ridge that can engage when the
two portions of the rod are assembled together;
[0055] FIG. 9 shows an alternative embodiment of the spinal rod,
wherein the reinforcing component is configured in a coil spring
like manner and overlaid around the circumference for the full
length of the flexible portion of the rod. Alternatively, the
flexible portion of the rod may be configured with corresponding
recesses on the surface of the flexible portion;
[0056] FIG. 10A-B show an alternative reinforcing component of the
spinal rod configured as a tubular mesh and in FIG. 10B disposed
around the surface the flexible portion of the rod;
[0057] FIG. 10C shows the alternative reinforcing component and
flexible portion of FIG. 10B, wherein the reinforcing component
mesh is disposed and partially embedded in only the end portions of
the spinal rod;
[0058] FIG. 10D shows an example of different alternative
embodiments of the reinforcing component partially embedded in
different portions of the same flexible portion of the rod.
DETAILED DESCRIPTION
[0059] Preferred embodiments of the present invention are disclosed
herein; however, it is understood that the following description
and each of the accompanying figures are provided as being
exemplary of the invention herein, which may be embodied in various
forms without departing from the scope of the claims. Thus, the
specific structural and functional details provided in the
following description are nonlimiting, but serve merely as a basis
for the invention as defined by the claims provided herewith. The
device described below can be modified as needed to conform to
further development and improvement of materials without departing
from the invention as claimed.
[0060] Referring now to the drawings, wherein like reference
numerals indicate similar features, the spinal rod, generally shown
at 10 in FIGS. 1A-C, 2A-D, 3B, 4B-D, 4F, 5, 6, 7, 9 and 10B
includes an elongate flexible component 12 and at least one rigid
reinforcing component 14, the at least one rigid reinforcing
component 14 being at least partially exposed on at least a portion
of the outer surface 16 of the flexible component 12.
[0061] The spinal rod 10 in accordance with the present invention
may be used in connection with any suitable components in
connection with fusion or other spinal or orthopedic procedures.
Such components include pedicle screw assemblies such as those
described in U.S. Pat. Nos. 6,261,287; 6,537,276; 6,858,030; and
7,128,743; the disclosures of each being incorporated herein by
reference as if fully set forth herein.
[0062] As shown in FIGS. 1A-C, 2A-C, 3B, 4B-D, 4F, 5, 6, 7, 9 and
10B, the reinforcing component 14, while at least partially exposed
on the surface of the flexible component 12 may also be at least
partially embedded in the flexible component 12 of the spinal rod
10. The reinforcing component 14 may be manufactured of titanium or
titanium alloy. However, the reinforcing component 14 may be made
of any metal or other suitable material (e.g., ceramic) that is
biocompatible and possess sufficient strength to resist damage from
the compressive forces associated with the attachment of
conventional bone screws to spinal rods. As shown in FIGS. 1A-C,
the embedded portion of the reinforcing component 14 may be
configured to include retention elements 18, which may serve to
support the integrity of the composite construction of the spinal
rod 10. As shown in FIG. 1C, the spinal rod 10 may be provided with
an end collar 20 or, as shown in FIG. 9, an end cap 22.
[0063] The spinal rod 10 may benefit from the bendable nature of
the flexible component 12 so as to provide a flexible or dynamic
spinal rod as an alternative to the conventional rigid rods
typically used in spinal fusion procedures. The flexibility of such
a dynamic rod allows selectively controlled articulation of the
spine while providing a necessary degree of control for a diseased
or injured part of the spine. The reinforcing components 14 may be
disposed within the composite spinal rod 10 in a variety of
configurations and, as demonstrated in FIG. 1B can be
asymmetrically arranged or skewed so as to influence or limit the
amount of flexibility along one or more planes about which the
vertebrae normally may articulate.
[0064] The spinal rod 10 may also be manufactured using a variety
of materials, diameters, number, position, and design of
reinforcing components 14 to plan and control the degree of
flexibility permitted. Indeed, it is not necessary that the spinal
rod 10 be cylindrical. Other shapes, such as a hexagonal profile,
an oval profile, or any other suitable profile, are also
contemplated. There may be a varying of profiles along the length
of the spinal rod 10 as well. This can be for many purposes,
including variability of stiffness or accommodation of different
materials along the length.
[0065] In addition, the reinforcing components 14, being at least
partially exposed on the outer surface 16 of the flexible component
12, may provide the protection for the spinal rod 10 from the
compressive forces that are normally exerted against a spinal rod
by the attachment of pedicle bone screws to the rod. Conventional
flexible spinal rods, some of which are composed of fragile,
flexible, polyurethane, PEEK, or similar materials, typically are
damaged and crushed under the compressive forces of the locking set
screws used in pedicle or bone screws. Conventional spinal rods
having internal reinforcing components may also be subject to the
compressive force damage caused by pedicle screw attachment to the
external surface of such flexible spinal rods. The damage done to
conventional flexible spinal rods in this manner may quickly
compromise the integrity of the spinal rod and thus compromise the
desired outcome of the original surgical procedure.
[0066] The spinal rod 10 may be manufactured using a wide variety
of configurations to achieve the goal of providing a flexible or
dynamic spinal rod that is not subject to structural damage as a
result of the attachment of bone screws. While it is possible to
manufacture the flexible component 12 of the spinal rod 10 from a
variety of flexible materials known in the art, it may be
advantageous to manufacture the flexible component 12 from any of
several grades of PEEK. The spinal rod 10 may thus be manufactured
to have a wide variance of flexibility to meet the specific needs
for the patient. It is also within the concept of the technology to
employ carbon fiber reinforced PEEK to increase the strength and
durability of the flexible component 12. With PEEK and similar
materials, the flexibility of the rod can be varied along the
length of a given rod, with or without reinforcing or other
components, such that a portion or portions are more flexible than
another portion or other portions. For example, the middle of a rod
may be made more stiff than the ends.
[0067] As shown in FIG. 2A, the design of the rod may be a
generally circular cross section of the flexible component 12
having a plurality of partially embedded rigid reinforcing
components 14 that are arranged in a generally uniform and
substantially parallel manner circumferentially around the long
axis of the spinal rod. Any variation of such a circumferentially
disposed array or spiral of reinforcing components 14 may provide
protection for the underlying flexible component 12 by hoop stress
transfer around the circumference of the spinal rod 10.
[0068] To further facilitate the transfer of compressive forces
from any bone screw attached to the spinal rod 10, the reinforcing
component rings may be provided with inwardly directed cross
members 24 that transversely bisect the flexible component along at
least one plane. Such internally directed cross members 24 may
function much like supporting trusses to provide axial stress
transfer from a reinforcing component 14 portion on one side of the
spinal rod 10 to the opposing side of the spinal rod 10. As shown
in FIG. 2A, the spinal rod 10 may be provided with multiple cross
members 24, that may be perpendicularly arranged relative to each
other or alternatively can be of any relative angle to each other.
Such variances in relative angle of multiple cross members 24, in
addition to providing protection for the internally disposed
flexible component 12, may also be advantageously used to
strengthen the spinal rod along selected planes to help control the
degree and direction of flexibility of the rod 10. Reinforcing
components may also be modified to achieve desired strength and
stiffness by, for example, connecting the reinforcing components 14
together.
[0069] There are contemplated a variety of alternative embodiments
that may employ reinforcing components configured as collars 26.
Nonlimiting examples of different types of collars 26 are shown in
FIGS. 2A-D, 3A-B, and 10D. The collars 26 may be uniformly disposed
along the longitudinal axis of the spinal rod 10, as demonstrated
in FIG. 2A. Alternatively, the collars 26, as shown in FIG. 2B, may
be manufactured so as to be positioned only at those points along
the length of the spinal rod 10 where the compressive forces of set
screws for bone screw attachment to the spinal rod 10 will be
exerted.
[0070] Further, the collars 26 may be partially embedded into the
flexible component 12, as shown in FIG. 2B or they may be imposed
on top of the surface of the flexible component 12, as shown in
FIG. 2C, giving an elevated appearance to the collar 26. When
positioned on the outer surface 16 of the flexible component 12,
the reinforcing component, such as a collar 26, may be provided
with a beveled edge 28 along any edge of the reinforcing component
14 that may come into repeated and dynamic contact with the
flexible component 12. Failure to provide a smoother beveled edge
28 could eventually subject the flexible rod 10 to unnecessary wear
and material fatigue. An alternative embodiment of any of the
possible collar 26 designs for the reinforcing component 14 may
include a compression slit 30, which may effectively absorb a
portion of the compressive forces exerted on the reinforcing
component 14 that may result from the tightening of the set locking
screw of the bone screw against the reinforcing component 14.
[0071] Alternatively, any of the embodiments of the composite
spinal rod having the reinforcing component 14 disposed on the
outer surface of the flexible component 12 may be manufactured such
that the diameter of the flexible component 12 is slightly smaller
than the internal diameter of the circumferentially positioned
reinforcing component 14. In such an embodiment, the slight
physical separation of the two components may provide additional
protection of the flexible component 12 from the compressive forces
placed against the external surface of the reinforcing component 14
when mechanical attachments such as pedicle screws are added.
[0072] Also contemplated are reinforcing components 14 that may be
manufactured and incorporated into the composite spinal rod 10 in a
configuration that is a combination of the longitudinally disposed
reinforcing members 14, such as shown in FIG. 1A, and the
circumferentially disposed reinforcing components 14. Such a
combined configuration could present as a checkerboard, lattice, or
matrix type array on the surface 16 of the flexible component 12.
The capacity to manufacture the spinal rod 12 with a wide variety
of reinforcing component 14 dispositions is advantageous because
the manufactured configurations may be purposely varied so as to
affect the functional characteristics of the spinal rod 10.
[0073] Further, as graphically illustrated by the hash marks of
greater frequency 42 or lesser frequency 44 in FIG. 6, the spinal
rod may be manufactured so as to provide a flexible component 12
that is more stiff 42 or more flexible 44 at any selected position
along the length of the rod 10. This alternative feature of the
spinal rod 10 may thus provide a gradient of stress protection in
selected sections of the rod. This may be accomplished by a variety
of manufacturing techniques that affect the flexible component 12,
the reinforcing component 14, or both in the same composite spinal
rod 10. One means of creating a gradient of stress protection
within the flexible component 12 is to manufacture the flexible
component 12 to include short or chopped filament carbon fiber
reinforcement in measured degrees only in those areas of the rod
where such additional support is desired. Alternatively, carbon
fibers may be circumferentially wound around the longitudinal axis
of the spinal rod and structurally incorporated into the flexible
component 12. The stress gradient can be varied by the introduction
of additional winds of the carbon filaments in some areas as
compared to other areas having fewer winds of the filaments and
thus more flexibility.
[0074] A gradient of flexibility may be provided by varying the
composition chemical formulation of the flexible component to
provide either more stiffness or more flexibility as desired for
different portions of the spinal rod 10.
[0075] A gradient of compressive stress protection may also be
provided by manufacturing the outwardly positioned reinforcing
component 14 as a tapered structure that is thicker in those areas
where additional stress protection is desired and relatively
thinner in those areas where more flexibility is desired and less
stress protection is required.
[0076] FIGS. 4A-F show non-limiting examples of a further
embodiment of the reinforcing component 14 of the spinal rod 10.
These reinforcing components 14 may be described as reinforcing
brackets 32. Common to any of the reinforcing brackets 32 shown in
these figures is an upper bracket 34 and an opposing lower bracket
36, which are connected one to another by a connecting pin 38 that
may pass transversely through the body of the flexible component
12. As with any of the reinforcing components 14 that were above
discussed, the reinforcing bracket 32 may serve to protect the
flexible component 12 from the compressive forces of the set screws
that lock the spinal rod into the groove of a conventional bone
screw. The connecting pin 38 may serve to transmit any such
compressive forces from the upper bracket 34, which may be in
contact with the set screw of the bone screw, to the lower bracket
36, thus protecting the internally disposed flexible component 12
from damage.
[0077] As shown in FIGS. 4A-B, the reinforcing bracket 32 may be
configured to have a flat upper bracket 34, which may be better
suited to receiving contact with a locking device of a pedicle
screw. One non-limiting example of a well known locking device is
the locking set screw of a pedicle screw. The area of the
reinforcing component 14 where the pedicle screw locking device may
make contact with the reinforcing component 14 of the spinal rod 10
may be textured, brazed, dimpled, cross-hatched, chemically treated
or machined in any way commonly known in the art to provide a
roughened surface that will facilitate the contact hold of the
pedicle screw locking device on the surface of the spinal rod 10. A
benefit to improving the frictional hold between the locking device
and the surface of the reinforcing component 14 may be that the
same effective hold may be achieved with a lessened level of
compressive force of the locking device against the spinal rod 10.
Thus, the provision of this alternative feature of a roughened
surface may in addition to improving the holding power of the
locking device against the spinal rod 10, may also serve to protect
the flexible component 12 of the spinal rod 10 from greater levels
of compressive force.
[0078] As shown in FIG. 4B, the reinforcing bracket may be
partially embedded in the flexible component 12 to provide an
appearance of being flush mounted on the outer surface 16 of the
flexible component 14. Alternatively, the reinforcing bracket 32,
as shown in FIG. 4C, 4D, and 4F, may extend above the outer surface
16 on the flexible component 12. Another variation of the
reinforcing bracket 32 is shown in FIGS. 4E-F as having curved
upper bracket 34 with a flattened apex that may best be described
as an upper bracket platform 40. Any of these exemplary variations
of the bracket-type reinforcing component 14 may be employed to
meet the specific needs of the surgeon without departing from the
basic concept of providing a flexible composite spinal rod that is
protected from damage from the compressive forces associated with
attachment to a pedicle screw.
[0079] As shown in FIGS. 5, 6 and 7, the rigid reinforcing
components 14 may be positioned at multiple levels. Such a
multi-level construct may be provided with a consistent degree of
flexibility and compressive stress resistance or it may be provided
with any or a combination of the alternative configurations and
compositions discussed above. In manufacturing the spinal rod 10,
the gradient of flexibility in the flexible component 12 may be
provided as varying or consistent at any specific portion of the
spinal rod as required by the functional needs of the
construct.
[0080] Further, as shown in FIG. 7, the reinforcing component 14
may be configured to provide an end-to-end connection function
between two or more separate flexible components 12 of the spinal
rod 10. To provide protection against compressive forces and to
strengthen the connection function embodiment 46, the reinforcing
component 14 may be provided with multiple connecting pins 38A, 38B
that pass transversely through the body of each of the two flexible
component rods 10A, 10B to be connected end-to-end. As graphically
illustrated by the hash marks 42 on flexible component rod 10B, the
so connected flexible component rods 10A and 10B can have different
compositions or functional characteristics. For example, one may
have greater flexibility than the other due to its composition
formulation or it may have differently configured internally
disposed reinforcing components. Any of the exemplary embodiments
discussed herein may be so connected one to the other as necessary
to obtain the functional characteristics required for the spinal
construct. FIGS. 8A-B show an additional embodiment of the spinal
rod 10 wherein the reinforcing component 14 is configured as an
open spiral having a complementary shape and size to the internally
disposed closed spiral configuration of the flexible component 12.
The spiral or thread design of the two components may facilitate
the process of threading the two together to form the completed
composite spinal rod 10. As with other embodiments, any other
suitable manufacturing technique, such as extrusion of the PEEK
into the reinforcing component 14, may also be employed. By varying
the width of the grooves in the open spiral of the reinforcing
component 14, or by varying the thickness of the reinforcing
component 14 spiral, the manufacturing process can also be used to
selectively determine the degree of stiffness and flexibility of
the resulting spinal rod 10.
[0081] FIGS. 9 and 10A-D provide additional non-limiting examples
of preferred embodiments. FIG. 9 demonstrates the possible use of a
flat metal spring design for the reinforcing component 14. Within
the spring design of the reinforcing component 14 the flexible
component 12 may be allowed flexibility and protection from
compressive forces as in other embodiments discussed herein. The
spring-type reinforcing component 14 may be positioned with a
complementary shaped groove in the outer surface 16 of the flexible
component 12 or alternatively like on the surface of the flexible
component 12. Even if a metal reinforcing component 14 is wound
over flexible component 12, the outer diameter of the reinforcing
component 14 may be greater than the diameter of the flexible
component 12 so that only metal contacts the pedicle screw or other
associated mechanism. In addition, the rod need not be round, as
shown in FIG. 9, but may be a different shape, such as, for
example, oval, octagonal or hexagonal. The use of metal end caps 22
are also shown in FIG. 9. In practice, end caps 22 may be attached
to any of the embodiments of the present technology.
[0082] FIGS. 10A-D show another embodiment of the reinforcing
component 14 in the form of a protective mesh that is
circumferentially disposed around the flexible component 12. The
stiffness of the mesh reinforcing component 14 may be matched to
the stiffness of the PEEK material selected for use in the flexible
component 12, thus creating a uniform spinal rod 12. This matching
and careful selection of manufacturing materials for all exemplary
embodiments discussed herein may be employed to provide a
customized composite spinal rod for a wide variety of applications.
For example, as shown in FIG. 10D, multiple embodiments of the
reinforcing component may be used on the same rod for optimal
clinical applications.
[0083] The material strength of the spinal rod 10 may be used as a
basis to determine with precision what degree of torque and
downward pressure of the set screw is needed to firmly hold the
spinal rod 10 in place in a pedicle screw without imposing
excessive and potentially damaging compressive forces. For each
construct, such a force determination may be made and then
subsequently applied to the insertion tool used to attach the
spinal rod to a pedicle screw.
[0084] The spinal rod 10 may be manufactured as integral components
by methods known in the art, to include, for example, molding,
casting, forming, extruding, or machine processing. The components
may be manufactured using materials having sufficient strength,
resiliency, and biocompatibility as is well known in the art for
such devices. By way of example only, suitable materials may
include implant grade metallic materials such as titanium, cobalt
chromium alloys, stainless steel, or other suitable materials for
this purpose. Flexible component 12 materials may be PEEK, carbon
fiber reinforced PEEK, or any other suitable flexible and
biocompatible material known in the art.
[0085] In another embodiment of the invention a kit may be
provided. A kit may include at least one of the spinal rod and at
least two pedicle screws. Spinal rods 10 of different lengths,
diameters, and cross sectional shapes may be provided in the kit to
permit selection and substitution as deemed necessary.
Additionally, a kit may include tools and/or instruments suitable
to facilitate implanting the spinal rod 10. Such a kit may be
provided with sterile packaging to facilitate opening and immediate
use in an operating room.
[0086] Although the invention herein has been described with
reference to particular embodiments, it is to be understood that
these embodiments are merely illustrative of the principles and
applications of the present invention. It is therefore to be
understood that numerous modifications may be made to the
illustrative embodiments, and that other arrangements may be
devised, without departing from the spirit and scope of the present
invention as defined by the appended claims.
* * * * *