U.S. patent application number 16/730174 was filed with the patent office on 2020-09-10 for spinal stabilization devices, systems, and methods.
The applicant listed for this patent is SPINAL KINETICS, INC.. Invention is credited to Michael L. Reo, Shigeru Tanaka.
Application Number | 20200281631 16/730174 |
Document ID | / |
Family ID | 1000004853265 |
Filed Date | 2020-09-10 |
United States Patent
Application |
20200281631 |
Kind Code |
A1 |
Reo; Michael L. ; et
al. |
September 10, 2020 |
Spinal Stabilization Devices, Systems, and Methods
Abstract
This specification describes spinal stabilization devices that
may be introduced into the spine via surgical procedures. In
particular, this specification describes an inter-spinous process
spacer having a core chosen, in one variation, to provide a
kyphotic or lordotic angle to the device. The specification also
describes systems including the described devices and methods of
introducing the devices and systems into the spine to provide
effective stabilization.
Inventors: |
Reo; Michael L.; (Redwood
City, CA) ; Tanaka; Shigeru; (Half Moon Bay,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SPINAL KINETICS, INC. |
SUNNYVALE |
CA |
US |
|
|
Family ID: |
1000004853265 |
Appl. No.: |
16/730174 |
Filed: |
December 30, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12434515 |
May 1, 2009 |
10517650 |
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16730174 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 17/7062
20130101 |
International
Class: |
A61B 17/70 20060101
A61B017/70 |
Claims
1. An interspinous spinal stabilization device implantable between
upper and lower spinous processes of adjacent vertebrae in a spine,
the spine having a spinal axis that is substantially parallel with
the spinal cord in the spine, the device comprising: an upper end
plate configured to attach to an upper spinous process with a first
fixation structure, and further configured with a cavity situated
opposite from the first fixation structure, the cavity
substantially conforming in shape to a compressible, elastic,
polymeric core member; a lower end plate configured to attach to a
lower spinous process with a second fixation structure, and further
configured with a cavity situated opposite from the second fixation
structure, the cavity substantially conforming in shape to the
compressible, elastic, polymeric core member; one or more flexible
members selected from the group consisting of fibers, ribbons, and
membranes extending between the upper end plate and the lower end
plate and associating movement in one end plate with movement in
the other end plate; and said compressible, elastic, polymeric core
member having a core axis along a core length, the core member
having dimensions perpendicular to the core length that are all
shorter than the core length, the core axis forming an included
angle with the spinal axis greater than about 35.degree. to and
including 90.degree..
Description
[0001] This specification describes spinal stabilization devices
that may be introduced into the spine via surgical procedures. In
particular, this specification describes an inter-spinous process
spacer having a core chosen, in one variation, to provide a
kyphotic or lordotic angle to the device. The specification also
describes systems including the described devices and methods of
introducing the devices and systems into the spine to provide
effective stabilization.
BACKGROUND
[0002] The spine is made up of twenty-four vertebrae that are
stacked one upon the other to form the spinal column. The spine
provides strength and support to allow the body to stand and to
move with some flexibility. Each vertebra includes an opening
through which the spinal cord passes. The collection of vertebrae
thus protects the spinal cord. The spinal cord includes thirty-one
pairs of nerve roots that branch from either side of the spinal
cord off to other parts of the body. Those nerve roots extend
through spaces between the vertebrae or in the vertebrae known as
the neural foramen.
[0003] Between each pair of the adjacent vertebrae is an
intervertebral disc. The disc is made up of three component
structures: (1) the nucleus pulposus; (2) the annulus fibrosus; and
(3) the vertebral endplates. The disc serves several purposes,
including absorbing shock, relieving friction, and handling
pressure exerted between the superior and inferior vertebral bodies
associated with the disc. The disc also absorbs stress between the
vertebral bodies, which stress would otherwise lead to degeneration
or fracture of the vertebral bodies.
[0004] Disorders of the spine are some of the costliest and most
debilitating health problems facing the populations of the United
States and the rest of the world, costing billions of dollars each
year. Moreover, as the population continues to age, the incidence
of spinal disorders continues to grow, including those caused by
disease, trauma, genetic disorders, and other causes.
[0005] Spine disorders are treated in a number of different ways.
Medicinal treatments, exercise, and physical therapy are typical
conservative treatment options. Less conservative treatment options
include surgeries, such as microdiscectomy, kyphoplasty,
laminectomy, dynamic stabilization, disc arthroplasty, and spinal
fusion. Traditionally, these treatment options are used in
isolation, rather than in combination, and the most conservative of
the treatment options utilized to provide a desired result.
[0006] U.S. patent application Ser. No. 11/281,205, entitled
"Prosthetic Intervertebral Discs," ("the '205 application"), was
filed Nov. 15, 2005, was published as Publication 2007/0050033 on
Mar. 1, 2007 and is assigned to Spinal Kinetics, Inc., the assignee
of this application. The '205 application describes, inter alia, a
treatment option that combines a prosthetic intervertebral disc
with a dynamic stabilization system. The '205 application (and its
provisional predecessor 60/713,671, filed Sep. 1, 2005) are
incorporated by reference.
[0007] In 1992, Dr. Manohar Panjabi introduced a model of a dynamic
spinal stabilization system that describes the interaction between
structures that stabilize the spine and defined spinal instability
as a region of laxity around the neutral resting position of a
spinal segment, identified as the "neutral zone." Panjabi, M M.,
"The Stabilizing System of the Spine. Part II. Neutral Zone and
Instability Hypothesis." J Spinal Disord 5 (4): 390-397, 1992b.
There is some evidence that the breadth of the neutral zone
increases as a result of intervertebral disc degeneration, spinal
injury, and spinal fixation. Id. Panjabi has subsequently described
dynamic stabilization systems that provide increased mechanical
support in the neutral zone and decreased support away from the
neutral zone. See, US Patent Publication No. 2004/0236329, dated
Nov. 25, 2004, which is hereby incorporated by reference
herein.
SUMMARY
[0008] The present invention, spinal stabilization components,
systems, and methods for their use. The spinal stabilization
components--in particular, inter-spinous process spacers--are
suitable for use in isolation, with other spinal stabilization
components, with one or more replacement disc components, with one
or more replacement disc nucleus components, and in other
systems.
[0009] Other spinal stabilization devices are used for facet joint
augmentation and replacement, facet joint implants, lateral spinal
stabilization devices, anterior spinal stabilization devices, and
the like. One variation of a system containing an inter-spinous
stabilization member comprises a combination with one or more
pedicle-based stabilization members such as those functioning by
biasing a pair of adjacent vertebral bodies apart. The combined
action of the inter-spinous spacer and the pedicle based members
creates a moment arm that relieves pressure from the disc.
[0010] Specifically, a dynamic stabilization device is comprised of
a posterior spacer member located between a pair of spinous
processes on adjacent vertebral bodies and provides a combination
of stabilizing forces to one or more spinal units to assist in
bearing spinal loads, whether in compression, tension, or torsion,
and in transferring or sharing those loads between vertebrae. The
posterior spacer maintains spacing between the pair of adjacent
vertebral bodies while allowing their relative motion.
[0011] The posterior spacer includes a generally compliant,
compressible, elastic material core situated within the device in a
position that is not collinear with the localized spinal axis. The
core may have: a.) a circular cross-section and be cylindrical,
tapering, barrel-shaped, etc., b.) an oval cross section and be
cylindrical, tapering, barrel-shaped, etc., or c.) a square,
rectangular, or other trapezoidal cross-section. The tapering cores
may provide a lordotic or kyphotic angle, as desired. The core may
be supported by upper and lower support structures having concave
shapes adjacent the core that generally correspond to the shape of
the adjacent compliant core. The upper and lower support structures
may be configured to attach directly to the spinous processes and
may be configured to attach to fixing structures that in turn
fixedly attach directly to the spinous processes.
[0012] The device may further comprise at least one fiber that
associates the movement of the upper and lower support structures,
e.g., by passage of that fiber (or fibers) between the upper and
lower support structures. That relationship created by the fiber or
fibers may be the result of any of a number of structural features.
For instance, the fiber or fibers may be wound through openings,
e.g., circular openings, oval openings, slots, etc., generally
placed in the upper and lower support structures laterally to the
core. The device may comprise one or more fibers wound in single
layers or multiple layers. The fibers themselves may be
monofilament or multifilament. In another variation, one or more
ribbons associating the upper and lower support structures may be
used.
[0013] The device may be configured in a number of different ways
for introduction into the inter-spinous-process space. The device
may be configured for introduction into the inter-spinous-process
space as an assembled structure. The device may be configured such
that the core in isolation is assembled into the remainder of the
device after the core-less device has been introduced into the
inter-spinous-process space. The device may be configured such that
the core and the support structures are assembled into two
previously sited fixing structures. The device may be configured
such that the core, perhaps conical or tapered in shape, adjusts
spacing or taper between the two adjacent vertebrae during
placement of the device. These devices may be introduced to the
spine using posterior or lateral approaches or a combination of the
two.
[0014] The spacer device itself may take other shapes or forms,
however, depending upon the size and shape of the spinal treatment
site and may be configured for post-operative adjustment of height
or angle relative to the core and support structures together or
individually and may engage spinal structures in a number of
orientations or configurations to achieve the desired physiological
result as described herein.
[0015] The device components may be formed from known materials
suitable for physiological implants and support structures. As
noted elsewhere, the core may comprise an elastic, compliant
material or materials, e.g., a polyurethane, polysiloxane
("Silicone"), or an appropriate elastomer. The upper and lower
support members and the attachment structures may be formed of
suitably stiff materials, e.g., stainless steels, superelastic
alloys such as nitinol, titanium and titanium alloys,
cobalt-chromium, polymeric materials such as polycarbonates, PEEK,
or an appropriate engineering polymers.
[0016] Finally, the invention includes systems comprising our
inter-spinous process spacer and an prosthetic intervertebral disc
or dynamic stabilizing devices to obtain desired therapeutic
results.
BRIEF DESCRIPTION OF THE FIGURES
[0017] The Figures are not necessarily drawn to scale. Some
components and features have been exaggerated for clarity.
[0018] FIG. 1 is a lateral view of a pair of adjacent vertebral
bodies, including representation of the foramen and nerve roots
traversing the foramen, the intervertebral disc, the spinous
processes, etc.
[0019] FIG. 2 is an exploded view of a variation of the
inter-spinous process spacers.
[0020] FIG. 3 provides three views of one of the support structures
of the inter-spinous process spacers.
[0021] FIGS. 4-8 provide side views of several variations of our
inter-spinous process spacers.
[0022] FIG. 9 is a side view of a variation of the inter-spinous
process spacer depicting one placement of fibers between upper and
lower support structures.
[0023] FIG. 10 is a side view, partial cutaway, exploded view of a
variation of the inter-spinous process spacer having a threaded,
constant diameter core.
[0024] FIG. 11 is a side view, partial cutaway, exploded view of a
variation of the inter-spinous process spacer having a threaded,
tapered core.
[0025] FIG. 12 provides a perspective views of a molded variation
of the inter-spinous process spacers.
[0026] FIG. 13 is a perspective, partially exploded view of a
variation of the inter-spinous process spacer in which the core is
installed after the fixation members are joined to the spinous
processes.
[0027] FIG. 14 provides a perspective view of a variation of the
inter-spinous process spacer after placement between adjacent
spinous processes.
DESCRIPTION
[0028] FIG. 1 illustrates a pair of adjacent vertebrae, including a
superior or upper vertebral body (100) and an inferior or lower
vertebral body (102). Upper vertebral body (100) includes a pair of
transverse processes (104a, 104b) and a spinous process (106)
extending generally posteriorly. Lower vertebral body (102)
includes a pair of transverse processes (105a,105b) and a spinous
process (107). A disc (108) is located between the superior
vertebral body (100) and the inferior vertebral body (102). The
spinal cord (110) extends through a central passage formed by the
spinal column, and nerve roots (112) transverse the foramenal space
(114) defined by the pair of vertebral bodies.
[0029] When the disc is damaged due to trauma, disease, or other
disorder, the superior vertebral body (100) and inferior vertebral
body (102) tend to collapse upon each other, thereby decreasing the
amount of space formed by the foramen (114). This result also
commonly occurs when the vertebral bodies are afflicted with
disease or are fractured or otherwise damaged. When the foramenal
space is decreased, the vertebral bodies (100, 102) may impinge
upon the nerve root (112), causing discomfort, pain, and possible
damage to the nerve root. The inter-spinous process spacers
described herein are intended to alleviate this problem by
maintaining or restoring the spacing between the adjacent vertebrae
and protect the nerve root from impingement by those vertebrae.
[0030] FIG. 2 shows a partially exploded, perspective view of one
variation of an inter spinous process spacer (150). This variation
includes a core (152) that is generally cylindrical in shape and
formed of a resilient, compliant, elastic material. The core member
(152) may comprise a hydrogel, gel, elastomer, polyurethane, or
other polymeric material suitable for providing the shock absorbing
and spacing functions necessary to stabilize the intervertebral
joint.
[0031] Examples of suitable block copolymer type thermoplastic
elastomers (TPE) products include Styroflex (BASF), Kraton (Shell
chemicals) styrene-butadiene-styrene block copolymer, Pellethane
(Dow chemical), Pebax, Arnitel (DSM), and Hytrel (Du Pont).
Alloy-type TPE's such as Santoprene (Monsanto), Geolast (Monsanto),
and Alcryn (Du Pont) as well as TPE's such as metallocene-catalyzed
polyolefin plastomers and elastomers and reactor-made thermoplastic
polyolefin elastomers are also suitable.
[0032] Of special interest are the polycarbonate-polyurethane and
silicone-urethane TPE's.
[0033] In the variation shown in FIG. 2, the device (150) includes
an upper end plate (154) and a lower end plate (156). In some
variations discussed elsewhere, the end plates (154, 156) are split
into two components for ease of placement: a support structure for
cradling the core (152) and a fixing structure for attachment to
the spinous process of the vertebra.
[0034] However, in this variation, each of the end plates (154,
156) includes a concave opening or area (158) that substantially
conforms in shape to the core (152). Also seen in this variation
are a number of openings (160) used for the filaments (not shown in
this drawing, but see 200 in FIG. 9) that contribute (with the core
152)) to associating the movement of the upper end plate (154) with
that of the lower end plate (156).
[0035] Each of the end plates (154, 156) includes a pair of tabs
(162) that, in turn, include openings (164) for affixing the device
(150) to a spinous process. As should be apparent, but in any case
is shown in FIG. 12, the extended spinous process fits between the
two tabs (162).
[0036] The openings (164) may be used in conjunction with bone
screws, pins, adhesives, filaments or cordage, etc. as fixing
devices.
[0037] The specific sizes of the end plates (154, 156) are chosen
with at least two criteria in mind: comparatively larger devices
(and endplates) are introduced into lumbar region intervertebral
spaces than the comparatively smaller devices introduced into the
cervical region intervertebral spaces and the end plates, after
implantation of the device, must not interfere with each other
during spinal flexing. As a practical matter, if a device such as
shown in FIG. 2 has a substantially circular cross-section, the gap
at each side of the device allowing such freedom from interference
may be 15.degree. or more on each side of the circular
cross-section.
[0038] The end plates (154, 156) shown in FIG. 2, as well as any of
the other components shown here (other than the core and the
filaments, sheets, and membranes) may comprise one or more of the
following physiologically acceptable materials having appropriate
mechanical properties: titanium, titanium alloys, stainless steel,
cobalt/chromium, polymers such as ultra high molecular weight
polyethylene (UHMW-PE), polyether ether ketone (PEEK), etc.;
ceramics; graphite; etc. The tabs (162) on the endplates (154, 156)
may be treated in various ways to encourage bone growth, e.g., by
roughening the surface or spraying metallic granular titanium onto
the surface of the tabs (162)--at least where the tabs comprise a
titanium or titanium alloy. Certain calcium phosphate treatments
may encourage bone growth as well.
[0039] This spacer design, having openings (160) for the fibers at
the periphery of the end plates (154, 156), allows the physician a
great deal of flexibility in selecting a core (e.g., 152)--with a
particular shape or size to remedy problems with a particular
patient's anatomy or to remedy a disease. The end plates may first
be affixed to the spinous processes without a core but (perhaps)
with the filaments loosely in place. A core "trial"--an instrument
(or collection of instruments) used to select an appropriately
sized core by introducing a number of core-substitutes into the
empty inter spinous process spacer until a desired result is
achieved, e.g., appropriate height or appropriate intervertebral
angle--may be used to select the optimum core. The filaments may
then be pulled tight and the core captured in the device. Fixing
the free ends of the filaments may be by tying or other similar
method.
[0040] FIG. 3 shows three views (end, side, and top views) of
another variation of our integrated end plate (170) also having
tabs (172) for affixing the end plate (170) to the spinous process.
The end plate (170) has a cavity (178) that substantially conforms
to the shape of the core that will be inserted there. This
variation includes a pair of stops (180) that tend to maintain the
core in an appropriate site in the completely assembled device.
[0041] FIG. 4 shows a single end plate (190) and its corresponding
core member (192). The core (192) is tapered and engages with the
cavity (194) in the endplate (190). This relationship may provide a
non-angular relationship between the two adjacent vertebrae.
[0042] FIG. 5 shows an end plate (200) and a core (202). The core
(202) is barrel-shaped and the endplate (200) has a cavity (206)
corresponding to the core (202) shape.
[0043] FIG. 6 shows an end plate (210) and a core (212) from still
another variation of our inter spinous process spacer. In this
instance, the core (212) has a curved thimble shape corresponding
to the cavity (214) in that end plate.
[0044] FIG. 7 shows an end plate (220) having a generally symmetric
shape in its cavity (214). Two cores (224, 226) are shown as
alternatives to provide a kyphotic or lordotic angle to the
device.
[0045] FIGS. 8 and 9 show two alternatives in associating the
movement of the upper and lower end plates.
[0046] FIG. 8 shows an end plate (250) having a pair of open-ended
slots (252, 254) into which specifically sized ribbons (256, 258)
may be placed to hold the assembled device with its pair of end
plates (250) and core in position.
[0047] FIG. 9 shows an assembled device (260) having an upper end
plate (262), a lower end plate (264), and a core (266). Also shown
in FIG. 9 are filaments (200) that pass through openings (268) in
each of the end plates (262, 264) and, after implantation,
influence the movements of the two end plates (262, 264).
[0048] The movement of one vertebral body with respect to an
adjacent vertebral body is quite complex. Movement of a lower
vertebral body with respect to an upper vertebral body in flexion,
in extension, laterally, and twisted about its axis is not a
circular rotation or linear movement. The effects of the
positioning (or geometry) of the facet joints with respect to the
intervertebral disc, their respective compressibilities, and other
related anatomical features all mandate a responsive motion of the
upper vertebral body that is quite complex.
[0049] Additionally, the adjacent intervertebral disc has a measure
of compressibility. The value for a healthy natural cervical disc
is 737 N/mm+/-885 N/mm.
[0050] The responsive motions in flexion, extension, and lateral
flexion are generally rotational in nature. However, each such
rotation includes a moving or instantaneous center or axis of
rotation. The viscous and elastic nature of the disc and varying
effect of the facet joints on the vertebral body movement
contributes to this complexity. Our prosthetic inter-spinous
process device, whether used in isolation or when used in
conjunction with a prosthetic intervertebral disc such as shown in
U.S. Pat. No. 7,153,325, contribute to the natural movement of the
spinal joint in response to external forces or moments. In the
implant described herein, the specific responsive movements are due
to the choice of materials, their compositions, certain of their
physical parameters (compressibility, the disclosed geometry,
etc.), and, in some cases, the manner in which the core is attached
to the assembly.
[0051] FIG. 10 is a side view, partial cutaway, exploded view of a
variation (270) of our inter-spinous process spacer having a
threaded, constant diameter core (272). The variation includes an
upper end plate (274) and a lower end plate (276) having
cooperating grooves (278) in each end plate (272, 274) that match
grooves (280) in the core (272). The core (272) may be screwed into
the upper end plate (274) and the lower end plate (276) after the
end plates are introduced into the space between the adjacent
inter-spinous processes. The end plates (272, 274) include
attachment structures (282, 284) having a support function as well.
A filament or filaments may be passed through the openings (285) as
discussed with regard to other variations.
[0052] FIG. 11 is a side view, partial cutaway, exploded view of a
variation (286) of our inter-spinous process spacer having a
threaded, tapered core (288). The variation includes an upper end
plate (290) and a lower end plate (292) having cooperating grooves
(294) in each end plate (286, 288) that match grooves (296) in the
core (288). The core (288) may be screwed into the upper end plate
(290) and the lower end plate (292) after the end plates are
introduced into the space between the adjacent inter-spinous
processes. Since the core (288) is tapered, this feature may be
used to change the spacing between the upper end plate (290) and
the lower end plate (292). A filament or filaments may be passed
through the openings (285) as discussed with regard to other
variations.
[0053] FIG. 12 shows a variation (300) of our device, without
fibers for clarity, comprising an upper end plate (302) and a lower
end plate (304). The core (306) rests in a cavity (308), the shape
of which conforms to the shape of the core (306). The openings
(310) for filaments are situated farther than the axis of the core
(306) than are the devices described elsewhere. The wider hole
(310) spacing provides a significantly different geometry for
between the end plates (302, 304). The movement of one end plate
affects the movement of the other with a controlled interaction and
consequently causes a controlled reaction between the adjacent
spinous processes.
[0054] FIG. 13 shows an exploded perspective view of a variation of
our device (320) where the upper end plate is made up of a support
structure (322) and a fixation structure (324) for affixing the
device to an upper spinous process. Similarly, the functional lower
end plate is made up of a support structure (326) and a fixation
structure (328) for affixing the device to a just lower spinous
process. In FIG. 13, the upper support structure (322) and the
lower support structure (326) surround a core (330) that is
assembled with one or more filaments (332) forming a central core
assembly (334). The central core assembly (334) is shown to have
longitudinal sliding dovetails (336, 338) that slide into matching
keyways (340, 342) in the upper fixation structure (324) and the
lower fixation structure (328).
[0055] Simply, during implantation, upper fixation structure (324)
and lower fixation structure (328) may be affixed to spinous
processes on adjacent vertebrae and, after determining the proper
size, angle, etc. of the central core assembly (334), the
longitudinal sliding dovetails (336, 338) of the chosen core
assembly (334) is introduced posteriorly into the matching keyways
(340, 342) in the upper fixation structure (324) and the lower
fixation structure (328).
[0056] The mating or cooperating dovetails and keyways may be
configured in various of the components so that the core assembly
is made to enter the fixation structures laterally or at an angle
posterio-laterally.
[0057] Finally, FIG. 14 depicts our inter spinous process spacer
(400) after implantation in a spine, specifically between an upper
spinous process (402) and a lower spinous process (404).
[0058] As noted above, U.S. patent application Ser. No. 11/281,205,
entitled "Prosthetic Intervertebral Discs," ("the '205
application"), was filed Nov. 15, 2005, was published as
Publication 2007/0050033 on Mar. 1, 2007 and is assigned to Spinal
Kinetics, Inc., the assignee of this application. The '205
application describes, inter alia, a treatment option that combines
a prosthetic intervertebral disc with a dynamic stabilization
system. The '205 application (and its provisional predecessor
60/713,671, filed Sep. 1, 2005) are incorporated by reference. Our
inter spinous process spacer is also suitable for use in
combination with the prosthetic intervertebral discs such as those
described in U.S. patent application Ser. No. 10/903,276, filed
Jul. 30, 2004, ("the '276 application"), published as Publication
2005/0228500 on Oct. 13, 2005, which is also incorporated by
reference herein.
Conventions
[0059] This description is not limited to the specifically
described variations. It is also to be understood that the
terminology used is solely for the purpose of describing
particulars of the devices and methods. The terminology is not
limited and the scope of the present invention is limited only by
the appended claims.
[0060] Where a range of values is provided, the description
specifically includes each intervening value, to at least the tenth
of the unit of the lower range limit unless the context clearly
dictates otherwise, found between the upper and lower range limits
of that range and any other stated or intervening value in that
stated range.
[0061] Unless defined otherwise, all technical and scientific terms
have the same meaning as commonly understood by one of ordinary
skill in the art to which the described device and methods belong.
All publications mentioned herein are incorporated herein by
reference for the purpose of disclosing and describing the methods
and/or materials in connection with which the publications are
cited.
[0062] Singular forms "a", "an," and "the" include plural referents
unless the context clearly dictates otherwise.
[0063] As will be apparent to those of skill in the art upon
reading this disclosure, each of the described device and method
has discrete components and features that may be readily separated
from or combined with the features of any of the other several
devices and methods.
[0064] It is to be understood that the described devices and
processes that are the subject of this patent application are not
limited to the particular described variations, as such may, of
course, vary. In particular, our description is meant to include
implanted or implantable combinations of two or more of the
specific devices described herein, to the extent that the devices
are compatible with one another.
* * * * *