U.S. patent application number 10/996996 was filed with the patent office on 2005-09-22 for method for remediation of intervertebral disks.
This patent application is currently assigned to St. Francis Medical Technologies, Inc.. Invention is credited to Hsu, Ken Y., Zucherman, James F..
Application Number | 20050209603 10/996996 |
Document ID | / |
Family ID | 34987337 |
Filed Date | 2005-09-22 |
United States Patent
Application |
20050209603 |
Kind Code |
A1 |
Zucherman, James F. ; et
al. |
September 22, 2005 |
Method for remediation of intervertebral disks
Abstract
A method for the implantation of a device made of bioresorbable
materials between interspinous processes is described. The implant
has a spacer that can be placed between adjacent spinous processes
to limit the movement of the vertebrae. Once inserted between
interspinous processes, the implant acts to limit extension
(backward bending) of the spine without inhibiting the flexion
(forward bending) of the spinal column. The device is used as an
adjunct to remediation of an intervertebral disk.
Inventors: |
Zucherman, James F.; (San
Francisco, CA) ; Hsu, Ken Y.; (San Francisco,
CA) |
Correspondence
Address: |
FLIESLER MEYER, LLP
FOUR EMBARCADERO CENTER
SUITE 400
SAN FRANCISCO
CA
94111
US
|
Assignee: |
St. Francis Medical Technologies,
Inc.
Alameda
CA
|
Family ID: |
34987337 |
Appl. No.: |
10/996996 |
Filed: |
November 23, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60526215 |
Dec 2, 2003 |
|
|
|
60526353 |
Dec 2, 2003 |
|
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Current U.S.
Class: |
606/90 ; 128/898;
606/247; 606/263; 606/279; 606/86A; 606/908; 623/17.11 |
Current CPC
Class: |
A61B 17/7053 20130101;
A61B 2017/00004 20130101; A61B 2017/0256 20130101; A61B 17/7068
20130101 |
Class at
Publication: |
606/090 ;
623/017.11; 606/061; 128/898 |
International
Class: |
A61B 017/88; A61B
017/70; A61F 002/44 |
Claims
What is claimed:
1. A method for remediation of a damaged intervertebral disk,
comprising the steps of: accessing an intervertebral space;
restoring the damaged disk; inserting a bioresorbable device
between spinous processes of the spinal column; and wherein the
steps of restoring and inserting are done in any order.
2. The method of claim 1 further comprising the step of tethering
the spinous processes with a bioresorbable tether.
3. The method of claim 2 wherein the tethering step further
comprises threading the tether around the spinous processes and
fastening the ends together.
4. The method of claim 1, where the step of inserting the device
further comprises: accessing adjacent first and second spinal
processes of the vertebrae; distracting the first and second
spinous processes; implanting the device between said spinous
processes, said device comprising a spacer; and where the
distracting and implanting steps are done in any order or
simultaneously.
5. The method of claim 4, wherein the step of implanting the spacer
between the spinous processes further comprises; assembling the
spacer on an insertion tool with a distal end and proximal end, the
tool comprising; a distraction guide at the distal end of the
insertion tool, a handle at the proximal end of the insertion tool,
a central body proximal to the distraction guide, and a stop
between the central body and the handle; and wherein the spacer
fits over the distraction guide and is disposed between the stop
and the distraction guide; separating tissues and ligaments with
the distraction guide of the insertion tool; urging the spacer into
the space between the spinous processes; removing the insertion
tool, while leaving the spacer in place; and where the distracting
and implanting steps are done in any order or simultaneously.
6. The method of claim 1, where the step of inserting the device
further comprises: accessing adjacent first and second spinal
processes of the vertebrae; distracting the first and second
spinous processes; inserting a device between the spinous processes
of the spinal column using the steps of: a central body with a
distal end and a proximal end, said central body having a
longitudinal axis; a spacer associated with the central body,
wherein said spacer is adapted to be placed between spinous
processes; a tissue expander extending from the distal end of the
body; and where the distracting and inserting steps are done in any
order or simultaneously.
7. The method of claim 1, where the step of inserting the device
further comprises: accessing adjacent first and second spinal
processes of the vertebrae; distracting the first and second
spinous processes; inserting a device between the spinous processes
of the spinal column, the device comprising: a central body with a
distal end and a proximal end, said central body having a
longitudinal axis; a stop located at the proximal end of the
central body; a spacer associated with the central body, wherein
said spacer is adapted to be placed between spinous processes; a
tissue expander extending from the distal end of the body; and
where the distracting and inserting steps are done in any order or
simultaneously.
8. The method of claim 7, wherein the stop is a first wing.
9. The method of claim 8 further comprising tethering the spinous
processes and the device wherein the device already is inserted
between the spinous processes, and wherein the device has a
bioresorbable tether anchored at a first end to the device.
10. The method of claim 9 wherein the tethering step further
comprises using a tool to guide a second end of the tether over an
upper spinous process, through a bore through the tissue expander,
under a lower spinous process, and through a lower bore in the
first wing; and anchoring the second end of the tether to the lower
bore in the first wing, the first end of the tether anchored to an
upper bore in the first wing.
11. The method of claim 9 wherein the tethering step further
comprises using a tool to guide a second end of the tether under a
lower spinous process, through a bore through the tissue expander,
over an upper spinous process, and through an upper bore in the
first wing; and anchoring the second end of the tether to the upper
bore in the first wing, the first end of the tether anchored to a
lower bore in the first wing.
12. The method of claim 8, further comprising a second wing located
at the distal end of the central body, wherein the spacer is
between the stop and the second wing.
13. The method of claim 12 further comprising tethering the spinous
processes and the device wherein the device already is inserted
between the spinous processes, and wherein the device has a
bioresorbable tether anchored at a first end to the device.
14. The method of claim 13 wherein the tethering step further
comprises using a tool to guide a second end of the tether over an
upper spinous process, through a bore through the tissue expander,
under a lower spinous process, and through a lower bore in the
first wing; and anchoring the second end of the tether to the lower
bore in the first wing, the first end of the tether anchored to an
upper bore in the first wing.
15. The method of claim 13 wherein the tethering step further
comprises using a tool to guide a second end of the tether under a
lower spinous process, through a bore through the tissue expander,
over an upper spinous process, and through an upper bore in the
first wing; and anchoring the second end of the tether to the upper
bore in the first wing, the first end of the tether anchored to a
lower bore in the first wing.
16. A method for remediation of a damaged intervertebral disk,
comprising: accessing the intervertebral space; inserting a device
between the spinous processes of the spinal column using the steps
of: accessing adjacent first and second spinal processes of the
vertebrae; distracting the first and second spinous processes;
implanting the device between the spinous processes; and where the
distracting and implanting steps are done in any order or
simultaneously; and replacing the intervertebral disk; and wherein
the steps of inserting and replacing are done in any order.
17. A method for remediation of a damaged intervertebral disk,
comprising: accessing the intervertebral space; inserting a device
between the spinous processes of the spinal column using the steps
of: accessing adjacent first and second spinal processes of the
vertebrae; distracting the first and second spinous processes;
implanting the device between the spinous processes; and where the
distracting and implanting steps are done in any order or
simultaneously; and repairing the intervertebral disk; and wherein
the steps of inserting and repairing are done in any order.
18. In a method for remediation of an intervertebral disk, the
improvement including the step of temporarily distracting spinous
processes with the implantation of a bioresorbable spacer between
the spinous processes.
19. In a method for remediation of an intervertebral disk, the
improvement including the step of temporarily maintaining a minimum
spacing between the spinous processes with the implantation of a
bioresorbable spacer between the spinous processes.
20. The method of claim 16 wherein the inserting step includes
inserting a bioresorbable device.
21. The method of claim 17 wherein the inserting step includes
inserting a bioresorbable device.
22. A method for remediation of a damaged intervertebral disk,
comprising the steps of: accessing an intervertebral space;
restoring the damaged disk; inserting a device between spinous
processes of the spinal column; and wherein the steps of restoring
and inserting are done in any order.
23. The method as in claim 22 further comprising the step of
tethering the spinous processes with a bioresorbable suture after
the inserting step.
24. The method as in claim 22 further comprising the step of
tethering the spinous processes and the device with a bioresorbable
suture after the inserting step.
25. In a method for remediation of an intervertebral disk, the
improvement including the step of temporarily distracting spinous
processes with the implantation of a spacer between the spinous
processes.
26. In a method for remediation of an intervertebral disk, the
improvement including the step of temporarily maintaining a minimum
spacing between the spinous processes with the implantation of a
spacer between the spinous processes.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to U.S. patent application Ser.
No. 10/230,505, filed Aug. 29, 2002, entitled "DEFLECTABLE SPACER
FOR USE AS AN INTERSPINOUS PROCESS IMPLANT AND METHOD," U.S.
Provisional Application Ser. No. 60/421,921, filed Oct. 29, 2002,
entitled "INTERSPINOUS PROCESS APPARATUS AND METHOD WITH A
SELECTABLY EXPANDABLE SPACER," and U.S. patent application Ser. No.
10/684,847, filed Oct. 14, 2003, entitled "INTERSPINOUS PROCESS
APPARATUS AND METHOD FOR SELECTABLY EXPANDABLE SPACER," which are
incorporated herein by reference. This application also is related
to U.S. patent application Ser. No. ______ filed ______ entitled,
"BIORESORBABLE INTERSPINOUS PROCESS IMPLANT FOR USE WITH
INTERVERTEBRAL DISK REMEDIATION OR REPLACEMENT IMPLANTS AND
PROCEDURES," incorporated herein by reference. This application is
also related to U.S. patent application Ser. No. 10/037,236, filed
Nov. 9, 2001, entitled "INTER-SPINOUS PROCESS IMPLANT AND METHOD
WITH DEFORMABLE SPACER," which is related to U.S. patent
application Ser. No. 09/799,215, filed Mar. 5, 2001, entitled
"SPINE DISTRACTION IMPLANT," which is related to U.S. patent
application Ser. No. 09/473,173, filed Dec. 28, 1999, entitled
"SPINE DISTRACTION IMPLANT," now U.S. Pat. No. 6,235,030, which is
related to U.S. patent application Ser. No. 09/179,570, filed Oct.
27, 1998, entitled "SPINE DISTRACTION IMPLANT," now U.S. Pat. No.
6,048,342, which is related to U.S. patent application Ser. No.
09/474,037, filed Dec. 28, 1999, entitled "SPINE DISTRACTION
IMPLANT," now U.S. Pat. No. 6,190,387, which is related to U.S.
patent application Ser. No. 09/175,645, filed Oct. 20, 1998,
entitled "SPINE DISTRACTION IMPLANT," now U.S. Pat. No. 6,068,630,
and U.S. application Ser. No. 10/694,103, filed Oct. 27, 2003,
entitled "INTERSPINOUS PROCESS IMPLANT WITH RADIOLUCENT SPACER AND
LEAD-IN TISSUE EXPANDER." All of the above are incorporated herein
by reference. This application is also related to U.S. patent
application Ser. No. 10/684,669, filed Oct. 14, 2003, entitled
"ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH TRANSLATING
PIVOT POINT AND METHOD," U.S. Provisional Patent Application Ser.
No. 60/526,724, filed Dec. 2, 2003, entitled "ARTIFICIAL VERTEBRAL
DISK REPLACEMENT IMPLANT WITH TRANSLATING PIVOT POINT AND LATERAL
IMPLANT METHOD," U.S. patent application Ser. No. 10/684,668, filed
Oct. 14, 2003, entitled "ARTIFICIAL VERTEBRAL DISK REPLACEMENT
IMPLANT WITH CROSSBAR SPACER AND METHOD," U.S. Provisional
Application Ser. No. 60/517,973, filed Nov. 6, 2003, entitled
"ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH CROSSBAR SPACER
AND LATERAL IMPLANT METHOD," U.S. patent application Ser. No.
10/685,011, filed Oct. 14, 2003, entitled "ARTIFICIAL VERTEBRAL
DISK REPLACEMENT IMPLANT WITH A SPACER AND METHOD," and U.S.
Provisional Application Ser. No. 60/524,350 filed Nov. 21, 2003,
entitled "ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH A
SPACER AND LATERAL IMPLANT METHOD," all of which are also
incorporated herein by reference.
CLAIM OF PRIORITY
[0002] U.S. Provisional Patent Application Ser. No. 60/526,215
entitled: METHOD FOR REMEDIATION OF INTERVERTEBRAL DISKS, by
Zucherman et al., filed Dec. 2, 2003 (Attorney Docket No.
KLYCD-01082US0), and U.S. Provisional Patent Application Ser. No.
60/526,353 entitled BIORESORBABLE INTERSPINOUS PROCESS IMPLANT FOR
USE WITH INTERVERTEBRAL DISK REMEDIATION OR REPLACEMENT IMPLANTS
AND PROCEDURES, by James F. Zucherman et al., filed Dec. 2, 2003
(Attorney Docket No. KLYCD-01082US 1) both which are incorporated
herein by reference.
BACKGROUND
[0003] This field of art of this disclosure is an interspinous
process implant.
[0004] The spinal column is a biomechanical structure composed
primarily of ligaments, muscles, vertebrae and intervertebral
disks. The biomechanical functions of the spine include: (1)
support of the body, which involves the transfer of the weight and
the bending movements of the head, trunk and arms to the pelvis and
legs, (2) complex physiological motion between these parts, and (3)
protection of the spinal cord and the nerve roots.
[0005] As the present society ages, it is anticipated that there
will be an increase in adverse spinal conditions which are
characteristic of older people. By way of example, with aging comes
an increase in spinal stenosis (including, but not limited to,
central canal and lateral stenosis), and facet anthropathy. Spinal
stenosis typically results from the thickening of the bones that
make up the spinal column and is characterized by a reduction in
the available space for the passage of blood vessels and nerves.
Pain associated with such stenosis can be relieved by medication
and/or surgery.
[0006] In addition, to spinal stenosis, and facet anthropathy, the
incidence of damage to the intervertebral disks due to injury or
degeneration is also common. The primary purpose of the
intervertebral disk is as a shock absorber. The disk is constructed
of an inner gel-like structure, the nucleus pulposus (the nucleus),
and an outer rigid structure comprised of collagen fibers, the
annulus fibrosus (the annulus). At birth, the disk is 80% water,
and then gradually diminishes, becoming stiff. With age, disks may
degenerate, and bulge, thin, herniate, or ossify. Additionally,
damage to disks may occur as a result spinal cord trauma or
injury.
[0007] Given an increasing need, there is increasing attention
currently focused on devices and methods for remediation of
conditions of the spine. Remediation includes replacement or
repair, or both of an affected part or parts of the spine, as will
be discussed in more detail subsequently. Regarding the evolution
of remediation of damage to intervertebral disks, rigid fixation
procedures resulting in fusion are still the most commonly
performed, though trends suggest a move away from such procedures.
Currently, areas evolving to address the shortcomings of fusion for
remediation of disk damage include technologies and procedures that
preserve or repair the annulus, that replace or repair the nucleus,
and that utilize technology advancement on devices for total disk
replacement. The trend away from fusion is driven by both issues
concerning the quality of life for those suffering from damaged
intervertebral disks, as well as responsible health care
management. These issues drive the desire for procedures that are
minimally invasive, can be tolerated by patients of all ages,
especially seniors, and can be performed preferably on an out
patient basis.
[0008] Accordingly, there is a need in the art for innovation in
technologies and methods that advance the art in the area of
minimally invasive intervertebral disk remediation, thereby
enhancing the quality of life for those suffering from the
condition, as well as responding to the current needs of health
care management.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIGS. 1A-1F. FIG. 1A is a front plan view of an embodiment
of an assembled the disclosed device; FIG. 1B is a left side view
of what is shown in FIG. 1A, and FIG. 1C is a front plan view of
FIG. 1A including a distraction guide, spacer, a central body and a
first wing; FIG. 1D is a left side view of the second wing of FIG.
1A; FIG. 1E is a front plan view of the second wing of FIG. 1A;
FIG. 1F is an end view of the spacer of FIG. 1A.
[0010] FIG. 2 is a front plan view of a second embodiment of the
disclosed device, including an end piece, a spacer, and a
distraction guide.
[0011] FIG. 3 is a front plan view of a third embodiment of the
disclosed device, which is an implant system including an insertion
tool comprised of a distraction guide, a central body, a stop and a
handle, with a spacer around the central body.
[0012] FIGS. 4A and 4B depict the use of the embodiment of FIG. 1A
for distraction between vertebrae.
[0013] FIG. 5 depicts a further embodiment of the apparatus of the
invention based on the embodiment in FIG. 2.
[0014] FIG. 6 depicts a further embodiment of the appratus of the
invention based on the embodiment in FIG. 1C.
[0015] FIG. 7 depicts a further embodiment of the apparatus of the
invention based on the embodiment in FIG. 1A.
[0016] FIG. 8 depicts an embodiment of the method of the present
invention.
DETAILED DESCRIPTION
[0017] What is disclosed herein is a device that limits spinal
extension without limiting spinal flexion. More specifically, the
embodiments of the device disclosed herein act to limit extension
(backward bending) of the spine without inhibiting the flexion
(forward bending) of the spinal column.
[0018] The disclosed device is made in part or entirely from
bioresorbable materials. The device is used to distract the spinous
processes of adjacent vertebrae in order to increase the volume of
the spinal canal, and concomitantly relieve intervertebral load. In
this regard, the bioresorbable device may be used in procedures
where temporary increase in spinal canal volume and relief of
intervertebral load is indicated for remediation of an adverse
spinal cord condition. Such distraction as a part of surgical
remediation of spinal disorders may be performed either before or
after the remediation procedure is performed. Remediation includes
replacement or repair, or both of an affected part or parts of the
spine. For example, remediation of the intervertebral disk may
include either disk replacement or disk repair, as well as repair
of one part of the disk; the annulus for example, and replacement
of another; the nucleus for example. One feature of a bioresorbable
device is that it does not require an additional surgery for
removal after temporary use.
[0019] A bioresorbable material is a material that is broken down
by natural processes, and removed thereby. Classes of materials
that are useful as bioresorbable materials include polymers,
ceramics, and glasses. Polymers of interest include polyesters,
polyether esters, polycarbonates, polysaccharides, polyanhydrides,
polyurethanes, and polyamide, including copolymers, composites, and
blends thereof, as well as composites and blends with ceramics,
glasses, and graphite, and the like. A copolymer is a polymer
derived from more than one species of monomer. A polymer composite
is a heterogeneous combination of two or more materials, wherein
the constituents are not miscible, and therefore exhibit an
interface between one another. A polymer blend is a macroscopically
homogeneous mixture of two or more different species of polymer,
the constituents of which are in principle separable by physical
means. Fillers, which are solid extenders, may be added to a
polymer, copolymer, polymer blend, or polymer composite. Fillers
are added to modify properties, such as mechanical, optical, and
thermal properties. For bioresorbable materials, it may be
desirable to add a filler that would reinforce the material
mechanically to enhance strength for certain uses, such as load
bearing devices. Bioresorbable ceramics, glasses, and graphite are
examples of classes of materials that are desirable for use as
fillers to enhance polymer material strength. It may be desirable
to add reinforcement elements to a bioresorbable polymer matrix
that have the same chemical composition as the polymer matrix. In
this instance, the material is referred to as self-reinforced
("SR").
[0020] Polyesters are a diverse class of polymers with a number of
bioresorbable materials of interest. Poly ether esters are a
closely related group, and due to the ester functionality, share
many of the same properties of members of the polyester class.
Since esters are a condensation polymer, they are easily degraded
by hydrolytic processes. Moreover, the materials of interest are
also biocompatible materials, meaning that they cause no untoward
effect to the host; e.g., excessive inflammation, thrombosis, and
the like. Additionally, these bioresorbable polyesters are readily
broken down in vivo and eventually excreted in a biocompatible
fashion.
[0021] Polyesters meeting the criteria of biocompatible,
bioresorbable materials include polymers made from monomers of
hydroxy acids such as the .alpha.-hydroxylactic acid,
.alpha.-hydroxyglycolidic acid, .beta.-hydroxybutyric acid,
.gamma.-hydroxycaprolic acid, and .delta.-hydroxvaleric acid.
Fumaric acid and hydroxyalkanes, such as propylene glycol, butylene
glycol, etc., form copolymers that are also candidate bioresorbable
polyesters. An example of a biodegradable poly ether ester is
poly(dioxanone).
[0022] Frequently, the starting materials are condensation products
of the free acids, producing cyclized structures used as the
monomer starting materials. Poly(dioxanone) is formed from the
cyclized monomer, p-dioxanone. For the lower molecular weight
hydroxy acids, two molecules of hydroxy acid may be condensed to
form a cyclized monomer. In the case of lactic acid, the
corresponding cyclized condensation product of two lactic acid
molecules is referred to commonly as a lactide. In the case of
glycolic acid, the resultant molecule is referred to commonly as a
glycolide. In this regard, whether one starts with lactic acid, or
forms thereof, or with lactide, the resultant polymer is a
homopolymer of lactic acid. Similarly, in the case of glycolic
acid, or forms thereof, and glycolide, regardless of the starting
monomer, the resultant polymer is a homopolymer of glycolidic acid.
The higher molecular weight hydroxy acids can undergo an internal
cyclization to form lactones that may be used as starting monomers,
as can the uncyclized monomer forms. Examples of these include
caproic acid, which forms .epsilon.caprolactone, and valeric acid,
which forms .delta.-valerolactone. Again, whether the cyclized
monomer, or the free acid monomer, or forms thereof are used as
starting materials, homopolymers of the corresponding acids will
result. In terms of the common nomenclature for designating these
polymers, either form of the starting material may be used to refer
to the polymer formed thereby. Hence, reference to polylactide is
equivalent to polylactate, since both are homopolymers of lactic
acid.
[0023] Stereoisomers of the lactic acid, and lactide exist. The
properties of the copolymers formed from the stereoisomers of
lactide may vary considerably. Interestingly, there is no linear
relationship between properties of homopolymers, and their
corresponding copolymers. In that regard, a 70:30 copolymer of
poly-L-lactide with poly-D,L-lactide produces a material that has a
degradation time of thirty-six months, while the degradation time
of poly-D,L-lactide is about twelve months and that of
poly-L-lactide is greater than twenty-four months. As another
example, a 50:50 copolymer blend of glycolide with D,L lactide
produces a material that degrades in about two months, while the
degradation of poly-D,L-lactide and polyglycolide is about twelve
months.
[0024] Major suppliers of bulk biodegradable polyester materials
include Boehringer Ingelheim, Purac, and Dow. Boehringer
Ingelheim's extensive RESOMER.RTM. line includes a variety of
medical grade poly(L-lactide), poly(D,L-lactide),
poly(L-lactide-co-D,L-lactide), poly(L-lactide-co-glycolide),
poly(L-lactide-co-.epsilon.-caprolactone),
poly(L-lactide-co-trimethylene carbonate), and poly(dioxanone)
resins for fabrication of the disclosed device. Similarly, Purac's
PURASORB.RTM. line includes lactide and glycolide monomers, as well
as polylactide, polyglycolide, and polylactide/glycolide copolymer
resins. Dow's Tone.TM. products include high molecular weight
polycaprolactone resins of high crystallinity. Metabolix Inc. is a
supplier of a family of poly(hydroxybutryate-co-valerate) copolymer
resins under the trade name Biopol.
[0025] Polycarbonates have strength properties desirable for
biocompatible, bioresorbable load bearing implants. The
copolymerization of lactide or glycolide with trimethylene
carbonate produces poly(lactide-co-trimethylene carbonate) and
poly(glycolide-co-trimethylen- e carbonate), respectively. These
copolymers have been used to make a range of products from sutures
to tacks and screws. Tyrosine derived polycarbonates such as
poly(desaminotyrosyl-tyrosine ethyl carbonate) and
poly(desaminotyrosyl-tyrosine hexyl carbonate) have also been used
in orthopedic applications, such as bone pins and screws. As
mentioned above, Boehringer Ingelheim is a bulk supplier of a
poly(L-lactide-co-trimethylene carbonate) resin, RESOMER.RTM. LT
706. Additionally, Integra Life Sciences is a supplier of tyrosine
polycarbonates.
[0026] Other examples of biocompatible, bioresorbable classes of
polymers are polysaccharides and polyanhydrides. Polysaccharides
are a diverse class and include glucans and glycosaminoglycans.
Glucans are any homopolymer of glucose, and include celluloses,
starches, and dextroses. Starch blends have properties desirable
for load-bearing biocompatible, bioresorbable implants. Blends
exhibiting good strength characteristics include starch/cellulose
acetate blends, starch/polycaprolactone blends, as well as starch
blended with copolymers of ethylene and vinyl alcohol.
Glucosaminoglycans includes hyaluronates, dermatan sulfates,
chondroitin sulfates, heparins, keratans, chitins, and chitosans.
The glucosaminoglycans are a ubiquitous class polysaccharides
occurring naturally as structural materials, and show potential for
as polymers and copolymers for biocompatible, bioresorbable
implants. Polyanhydrides are formed by the condensation of diacid
molecules. One example of a bioresorbable polyanhydride copolymer
is the condensation of sebacic acid ("SA") with hexanedecandioic
acid ("HAD") to form poly ("SA-co-HAD") anhydride.
[0027] It should be noted that there are two important phases of
the process of bioresorption: time to complete loss of strength of
the material, and time to complete resorption. There are several
factors that affect the rate of degradation of bioresorbable
materials, and hence both the time to complete loss of strength,
and time to complete resorption. In general, reduction in strength
follows the reduction in molecular weight of a polymeric material
as it degrades. Factors that affect degradation of bioresorbable
polymers include the crystalline nature of the starting material,
the hydrophilic nature of the polymer backbone, whether or not the
polymer has a reinforcing filler, the initial molecular weight of
the polymer, the degree of porosity of the polymer material, the
surface area to mass ratio of the device, and the degree of stress
on the implanted device.
[0028] An example of how the crystalline vs. amorphous nature of
the starting material impact degradation is illustrated in the
comparing the properties of poly-L-lactide vs. poly-D,L-lactide.
The time to complete loss of strength of poly-D,L-lactide is about
6 months, while that of poly-L-lactide is more than 12 months.
Recalling from the above, poly-D,L-lactide degrades more rapidly
(12 months) than poly-L-lactide (24 months). The racemic mixture of
the stereoisomer produces significantly amorphous powders, which
yield lower strength materials degrading more rapidly than polymers
made from their highly crystalline counter part. Still another
example of how the crystalline versus amorphous nature of a
material affects degradation time comes from the previously given
example of a 50:50 copolymer blend of glycolide with D,L lactide.
This copolymer exhibits a highly amorphous state, and produces a
material that degrades significantly faster (two months) than the
degradation of poly-D,L-lactide and polyglycolide (twelve
months).
[0029] Concerning the hydrophilic nature of the polymer backbone,
an example of how this property impacts degradation is demonstrated
through the comparison of the stability of poly-L-lactide against
polyglycolide. Poly-L-lactide has an increased hydrophobic nature
(decreased hydrophilic nature) compared with polyglycolide, due to
the methyl group in the backbone structure, and is therefore less
susceptible to hydrolysis. The time to complete loss of strength of
poly-L-lactide is greater than twelve months, while that of
polyglycolide is about two months. The comparative degradation
times for poly-L-lactide and polyglycolide are twenty-four months
versus about six to twelve months, respectively.
[0030] The impact of reinforcing filler on increasing material
strength can be understood by comparing poly-L-lactide to SR
poly-L-lactide properties. Time to complete loss of strength for
poly-L-lactide is greater than twelve months, while for SR
poly-L-lactide is about eighteen months, while the degradation
times are about twenty-four months and seventy-two months,
respectively. Other types of reinforcing fillers include ceramics,
glasses, and graphite fibers. Ceramics including hydroxyapaptite
and tricalcium phosphate, and blends thereof are commonly used
reinforcing bioresorbable materials. Bioglasses are silicate
glasses containing sodium, calcium, and phosphate as the main
components. Ceramics, bioglasses, and bioglass/ceramic compositions
have been used in numerous polymer and copolymer bioresorbable
material blends to add strength to these materials. The
bioresorption of the inorganic ceramic and glass materials follows
as the dissolution of the ions, and bioresorption thereof.
[0031] In addition to the molecular properties influencing material
properties that impact degradation, bulk properties of the
material, such as the porosity of material, as well as properties
of the device, such as the surface area to mass ratio, affect
degradation time, as well. As previously mentioned, there are two
phases to the degradation process: time to complete loss of
strength and time to complete resorption. These two phases of
degradation correlate to two distinct processes: (1) water
penetration into the material, with initial degradation of polymer
chains, referred to as the hydrolysis phase; and (2) degradation of
material strength and fragmentation, and procession of enzymatic
attack, phagocytosis, and metabolism. This phase is referred to as
metabolism or bulk erosion. Increased porosity of a device and
increased relative surface area to mass of a device will enhance
the hydrolysis phase, and hence tend to hasten the overall
degradation process.
[0032] Regarding the impact of degradative processes on the site of
the implant, as loss of strength proceeds, the implant will begin
to fragment. Increased stress on the implant, and increased
vascularization may increase the degradation time. Stress may have
a role in decreasing structural integrity, and the increase in the
rate of water absorption thereby, and hence affect the rate of bulk
erosion. Once the polymer has fragmented into small pieces, in vivo
processes, such as phagocytosis, and enzymatic activity speeding up
the hydrolysis process may proceed to hasten in the bioresorption
process. Such in vivo processes are enhanced by increased
vascularization. The presence of the small particles, as well as a
local drop in tissue pH in the case of ester hydrolysis due to
increased levels of free acid, induces an inflammatory response in
the tissue. When bioresorption is complete, the inflammatory
response subsides. In that regard, it may be desirable, depending
on the use of the device, to fabricate devices from polymers that
take longer to complete loss of strength, and have slower rates of
degradation.
[0033] By what is disclosed of molecular properties, bulk material
properties, device design, and factors at the site of implantation,
it is therefore possible to design devices from selected materials
accordingly.
[0034] The following description is presented to enable any person
skilled in the art to make and use the disclosed device. Various
modifications to the embodiments described will be readily apparent
to those skilled in the art, and the principles defined herein can
be applied to other embodiments and applications without departing
from the spirit and scope of the present disclosure as defined by
the appended claims. Thus, the present disclosure is not intended
to be limited to the embodiments shown, but is to be accorded the
widest scope consistent with the principles and features disclosed
herein.
[0035] An embodiment of an implant 100 of the disclosed device is
depicted in FIG. 1A. This implant 100 includes a first wing 104 and
a spacer 150 and a lead-in tissue expander or distraction guide
110. This embodiment further can include, as required, a second
wing 132. As can be seen in FIG. 1A, a central body 102 extends
from the first wing 104 and is the body that connects the first
wing 104 to the tissue expander or distraction guide 110. Also, as
can be seen in FIG. 1A and 1B, the distraction guide 110 in this
particular embodiment acts to distract the soft tissue and the
spinous processes when the implant 100 is inserted between adjacent
spinous processes. In this particular embodiment, the distraction
guide 110 has an expanding cross-section from the distal end 111 to
the area where the second wing 132 is secured to the distraction
guide 110. In this embodiment the distraction guide 110 is
wedge-shaped.
[0036] Additionally, as can be seen in FIGS. 1A, and 1F, the spacer
150 is elliptical shaped in cross-section. The spacer 150 can have
other shapes such as circular, oval, ovoid, football-shaped, and
rectangular-shaped with rounded comers and other shapes, and be
within the spirit and scope of what is disclosed. In this
embodiment, spacer 150 includes a bore 152 which extends the length
of spacer 150. The spacer 150 is received over the central body 102
of the implant 100 and can rotate thereon about the central body
102. In these embodiments, the spacer 150 can have minor and major
dimensions as follows:
1 MINOR DIMENSION (116A) MAJOR DIMENSION (116 B) 6 mm 13.7 mm 8 mm
14.2 mm 10 mm 15.2 mm 12 mm 16.3 mm 14 mm 17.8 mm
[0037] The advantage of the use of the spacer 150 as depicted in
the embodiment of FIG. 1A is that the spacer 150 can be rotated and
repositioned with respect to the first wing 104, in order to more
optimally position the implant 100 between spinous processes. It is
to be understood that the cortical bone or the outer bone of the
spinous processes is stronger at an anterior position adjacent to
the vertebral bodies of the vertebra than at a posterior position
distally located from the vertebral bodies. Also, biomechanically
for load bearing, it is advantageous for the spacer 150 to be close
to the vertebral bodies. In order to facilitate this and to
accommodate the anatomical form of the bone structures, as the
implant is inserted between the spinous processes and/or urged
toward the vertebral bodies, the spacer 150 rotates relative to the
wings, such as wing 104, so that the spacer 150 is optimally
positioned between the spinous processes, and the wing 104 is
optimally positioned relative to the spinous processes. Further,
the broad upper and lower surfaces of the spacer 150 helps spread
the load that the spinous processes place on the spacer 150.
[0038] As may be required for positioning the implant 100 between
the spinous processes, implant 100 can also include a second wing
132 (FIG. 1E) which fits over the distraction guide 110 and is
secured by a bolt 130 (FIG. 1A) placed through aperture 134
provided in a tongue 136 of second wing 132 (FIG. 1E). The bolt 130
is received and secured in the threaded bore 112 located in
distraction guide 110. As implanted, the first wing 104 is located
adjacent to first sides of the spinous processes and the second
wing 132 is located adjacent to second sides of the same spinous
processes.
[0039] In another embodiment, the spacer 150 has a cross-section
with a major dimension and a minor dimension, wherein the major
dimension is greater than the minor dimension and, for example,
less than about two times the minor dimension.
[0040] Implant 200 is depicted in FIG. 2. This implant is similar
to the implants 100 of FIG. 1, except that this implant does not
have either first or second wings. Implant 200 includes a
distraction guide 210, spacer 220 which surrounds a central body
just as central body 102 of implant 100 in FIG. 1, and endpiece
230. The distraction guide 210 in this preferred embodiment is
cone-shaped, and is located at one end of the central body (not
shown). At the other end is an endpiece 230. Endpiece 230 is used
to contain the other end of the spacer 220 relative to the central
body. This embodiment is held together with a bolt (not shown).
[0041] FIG. 3 depicts an implant system 300. Implant system 300
includes an insertion tool 310. Insertion tool 310 includes a
distraction guide 320 which in a preferred embodiment is
substantially cone-shaped. Distraction guide 320 guides the
insertion of the spacer 330 and the insertion tool 360 between
adjacent spinous processes. The insertion tool 310 further includes
a central body 340, a stop 350, and a handle 360. The distraction
guide 320 at its base has dimensions which are slightly less than
the internal dimensions of the spacer 330 so that the spacer can
fit over the distraction guide 320 and rest against the stop 350.
The tool 310 with the distraction guide 320 is used to separate
tissues and ligaments and to urge the spacer 330 in the space
between the spinous processes. Once positioned, the distraction
guide insertion tool 310 can be removed leaving the spacer 330 in
place.
[0042] For the implants 200 of FIG. 2 and 300 of FIG. 3, such
devices would be appropriate where the anatomy between the spinous
processes was such that it would be undesirable to use either a
first or second wing. However, these embodiment afford all the
advantageous described hereinabove (FIGS. 1A-1F) with respect to
the distraction guide and also with respect to the dynamics of the
spacer.
[0043] Additionally, for the embodiments shown in FIGS. 2 and 3,
the device may be secured in place via bioresorbable sutures or
screws. The degradation times of sutures made from bioresorbable
polymers are influenced by both the suture size and type of
polymer. Suture products such as Maxon (Davis and Geck), a
polyglyconate based suture material, and PDS (Ethicon), a
polydioxanone based suture material, maintain tensile strength for
four to six weeks, and may take up to six months to be resorbed
completely. Depending on the material used, as detailed above,
screws may have total time to resorption from six months to five
years. Biologically Quite (Instrument Makar), a
poly(D,L-lactide-co-glyco- lide) screw degrades in about six
months, while Phusiline (Phusis), a poly(L-lactide-co-D,L lactide)
copolymer degrades in about five years, and Bioscrew (Linvatec), a
ploy(L-lactide) screw degrades in the range of two to three
years.
[0044] In FIGS. 4A, 4B, what is shown is the view of the device 100
inserted between the spinous processes, so as to distract the two
vertebrae 410, 420, thereby increasing the volume of the spinal
canal, and concomitantly relieving the intervertebral load. The
anterior direction is denoted "A," and the posterior direction is
denoted "P."
[0045] The implants described also can be used with other elements
that further stabilize the spine and the implant's 100 location in
the spine as it functions to increase temporarily the volume of the
spinal canal and to relieve the intervertebral load. For example,
the implants 100, 200, and 300 can be used with a tether or suture
which is fitted and secured around adjacent spinous processes. The
tether or suture (these terms to be used interchangeably herein)
can be made of biocompatible, bioresorbable material(s) described
above and as such, the tether need not be explanted, sparing the
patient from additional surgery.
[0046] A first use of a tether is depicted in FIG. 5. In this
embodiment 400, an implant such as implant 100 or 200 can be
positioned between a upper spinous process 710 and a lower spinous
process 720, and a tether 470 can loop around the upper spinous
process 710 and the lower spinous process 720. The tether 470 need
not interact with the implant 100, 200, or 300; that is, there need
not be a fastening mechanism to connect the implant 100, 200, or
300 with the tether 470. Instead, the ends of tether 470 can be
fastened together in a loop by any suitable mechanism.
Alternatively, the ends can be knotted or stitched to fasten them
through the bores.
[0047] A further use of the tether is depicted in FIG. 6. In this
embodiment 500, based upon implant 100, the tether 570 fastens to
an upper bore 505 of the first wing 504, and loops around the upper
spinous process 710 to be threaded through a bore 515 through the
distraction guide 510. The tether 570 then continues to loop around
by passing around the lower spinous process 720 and fastens to a
lower bore 507 in the first wing 504. The tether 570 can be
fastened at the upper bore 505 and lower bore 507 of the first wing
504 by an appropriate fastening means, such as a cuff made of
biocompatible, bioresorbable material. Alternatively, the ends of
the tether 570 fastened to the upper bore 505 and lower bore 507
can be knotted or tied off, or sewn with sutures.
[0048] As depicted in FIG. 7, a tether also can be used in
conjunction with implant 100 where implant 100 has a second wing
632. The tether 670 need not pass through or connect with the
second wing 632. Instead, the tether 670 fastens with an upper bore
605 in a first wing 604 and passes around an upper spinous process
710 and can then pass through a bore 615 in the distraction guide
610. The tether 670 then passes under the lower spinous process 720
and fastens with a lower bore 607 through the first wing 604. The
tether 670 can be fastened at the upper bore 605 and lower bore 607
of the first wing 604 by an appropriate fastening means, such as a
cuff made of biocompatible, bioresorbable material. Alternatively,
the ends of the tether 670 fastened to the upper bore 605 and lower
bore 607 can be knotted or tied off, or sewn with sutures.
[0049] One use contemplated for such devices is implantation in
conjunction with intervertebral disk remediation, either implanting
a disk replacement device or performing surgical repair on an
intervertebral disk. Devices and methods suitable for disk
replacement have been described in U.S. patent application Ser. No.
10/685,134, filed Oct. 14, 2003, entitled "TOOLS FOR IMPLANTING AN
ARTIFICIAL VERTEBRAL DISK AND METHOD," U.S. patent application Ser.
No. 10/684,669, filed Oct. 14, 2003, entitled "ARTIFICIAL VERTEBRAL
DISK REPLACEMENT IMPLANT WITH TRANSLATING PIVOT POINT AND METHOD,"
U.S. Provisional Patent Application Ser. No. 60/526,724, filed Dec.
2, 2003, entitled "ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT
WITH TRANSLATING PIVOT POINT AND LATERAL IMPLANT METHOD," U.S.
patent application Ser. No. 10/684,668, filed Oct. 14, 2003,
entitled "ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH
CROSSBAR SPACER AND METHOD," U.S. Provisional Application No.
60/517,973, filed Nov. 6, 2003, entitled "ARTIFICIAL VERTEBRAL DISK
REPLACEMENT IMPLANT WITH CROSSBAR SPACER AND LATERAL IMPLANT
METHOD," U.S. patent application Ser. No. 10/685,011, filed Oct.
14, 2003, entitled "ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT
WITH A SPACER AND METHOD," and U.S. Provisional Application Ser.
No. 60/524,50, filed Nov. 21, 2003, entitled "ARTIFICIAL VERTEBRAL
DISK REPLACEMENT IMPLANT WITH A SPACER AND LATERAL IMPLANT METHOD,"
and are incorporated herein by reference. In addition to the total
disk replacement devices described in the aforementioned
applications, polymer-filled implants based on a biomimetic
approach to disk repair and replacement may be used for
remediation. Devices and methods describing the use of such
implants are found in U.S. Pat. No. 6,416,766, issued Jul. 9, 2002,
entitled "BIOLOGICAL DISK REPLACEMENT BONE MORPHOGENIC PROTEIN
(BMP) CARRIERS AND ANTI-ADHESION MATERIALS," and U.S. patent
application Ser. No. 09/815,387, filed Mar. 22, 2001, entitled
"IMPLANTABLE PROSTHETIC OR TISSUE EXPANDING DEVICE," both
incorporated herein by reference.
[0050] FIG. 8 is a flowchart showing an embodiment of the method of
the present invention. Regarding the disclosed devices used in
conjunction with disk remediation implants and procedures like
those described by the aforementioned incorporated references, load
relief of the vertebral disks, either before or after a disk
remediation procedure is done 820, is indicated either to assist in
the process of disk remediation, or to allow for effective recovery
of the surgical procedure, or both. Moreover, the disclosed
devices, made in part or completely from the biocompatible,
bioresorbable materials described in this disclosure, require no
additional surgical procedure for removal after recovery is
complete.
[0051] The bioresorbable load relief/spinal distraction devices
disclosed above can be inserted laterally. The implanting physician
after accessing the intervertebral space 810 optionally can
distract the spinous process before inserting the device 830, 840.
Alternatively, the tissue expander can be used to distract the
spinous processes while inserting the device 830, 840.
[0052] The spinous processes can be further stabilized by the use
of a bioresorbable tether together with the resorbable distracting
device adapted to accept the tether 855, or with a bioresorbable
device which does not have wings and need not be adapted to accept
the tether 850. If the device does not have a first or second wing,
the tether is looped around the spinous processes and fastened,
after the implant is positioned between the spinous processes
850.
[0053] Certain of the bioresorbable devices are adapted to accept
the tether so that the tether binds not only the spinous processes
but also the implant, to maintain temporarily a minimum spacing
between the spinous processes 855. The adaptations include an upper
bore and a lower bore on the first wing, and a bore through the
distraction guide. During the implantation, the device is inserted
between the spinous processes with one first of the tether attached
to the upper bore of the first wing. A curved needle or other tool
can then be used to lead the second end of the tether over an upper
spinous process, through the bore in the tissue expander, under a
lower spinous process, and through the lower bore of the first
wing, to fasten the second end to the lower bore of the first wing.
The tether is tightened to the desired degree to maintain a minimal
distraction of the spinous processes and the ends of the tether are
fastened 860.
[0054] It is within the scope of the present invention to fasten
the first end of the tether to the lower bore of the first wing,
and to use a curved needle or other implement to lead the second
end of the tether below the lower spinous process, through the bore
in the tissue expander, over the upper spinous process, and through
the upper bore on the first wing, to fasten the second end of the
upper bore of the first wing.
[0055] Where the implant has a second wing, the same method is
followed as for an implant with one wing, as the second wing need
not engage the tether.
[0056] The foregoing description of embodiments of the present
disclosure has been provided for the purposes of illustration and
description. It is not intended to be exhaustive or to limit the
disclosure to the precise forms disclosed. Many modifications and
variations will be apparent to the practitioner skilled in the art.
The embodiments were chosen and described in order to best explain
the principles of this disclosure and its practical application,
thereby enabling others skilled in the art to understand various
embodiments and with various modifications that are suited to the
particular use contemplated. It is intended that the scope of this
disclosure be defined by the following claims and its
equivalence.
* * * * *