U.S. patent application number 11/491450 was filed with the patent office on 2008-01-24 for expandable vertebral implant and methods of use.
Invention is credited to Jason A. Edie.
Application Number | 20080021556 11/491450 |
Document ID | / |
Family ID | 38972451 |
Filed Date | 2008-01-24 |
United States Patent
Application |
20080021556 |
Kind Code |
A1 |
Edie; Jason A. |
January 24, 2008 |
Expandable vertebral implant and methods of use
Abstract
An implant for insertion between vertebral body endplates
includes first and second end members, each with a respective
endplate contact surface. The implant further includes a
collapsible intermediate section disposed between the first and
second end members and an inflatable member contained within the
intermediate section. The intermediate section may be expandable
upon the introduction of a substance into the inflatable member
between a first size to space the first and second end members a
first distance apart and a second enlarged size to space the first
and second end members a second greater distance apart. The
inflatable member may increase in size from a compressed size in
which the inflatable member will pass through an opening in the
intermediate section and an expanded size in which the inflatable
member will not pass through the opening and is thereby captively
retained within the intermediate section.
Inventors: |
Edie; Jason A.; (Memphis,
TN) |
Correspondence
Address: |
COATS & BENNETT, PLLC
1400 Crescent Green, Suite 300
Cary
NC
27518
US
|
Family ID: |
38972451 |
Appl. No.: |
11/491450 |
Filed: |
July 21, 2006 |
Current U.S.
Class: |
623/17.11 |
Current CPC
Class: |
A61F 2002/30584
20130101; A61F 2/30742 20130101; A61F 2002/3052 20130101; A61F
2002/3055 20130101; A61F 2230/0013 20130101; A61F 2002/30133
20130101; A61F 2002/4693 20130101; A61F 2220/0075 20130101; A61F
2/4611 20130101; A61F 2002/30588 20130101; A61F 2002/30113
20130101; A61F 2002/30131 20130101; A61F 2002/4495 20130101; A61F
2002/30772 20130101; A61F 2220/0025 20130101; A61F 2002/30841
20130101; A61F 2230/0006 20130101; A61F 2002/30092 20130101; A61F
2230/0065 20130101; A61F 2/44 20130101; A61F 2002/2835 20130101;
A61F 2002/30476 20130101; A61F 2002/30601 20130101; A61F 2210/0085
20130101; A61F 2002/2817 20130101; A61F 2210/0014 20130101; A61F
2002/302 20130101; A61F 2002/30462 20130101; A61F 2230/0015
20130101; A61F 2002/30583 20130101 |
Class at
Publication: |
623/17.11 |
International
Class: |
A61F 2/44 20060101
A61F002/44 |
Claims
1. An implant for insertion between vertebral body endplates in a
patient, the implant comprising: a first end member including a
first endplate contact surface; a second end member including a
second endplate contact surface; a collapsible intermediate section
disposed between the first and second end members; and an
inflatable member contained within the intermediate section, the
intermediate section being expandable upon the introduction of a
substance into the inflatable member, the intermediate section
being expandable between a first size to space the first and second
end members a first distance apart and a second enlarged size to
space the first and second end members a second greater distance
apart.
2. The implant of claim 1 wherein the collapsible intermediate
section is flexible.
3. The implant of claim 1 wherein the collapsible intermediate
section comprises a plurality of tethers secured about a perimeter
of the first and second end members.
4. The implant of claim 1 wherein the collapsible intermediate
section comprises a single tether coupled between a perimeter of
the first and second end members.
5. The implant of claim 4 wherein the single tether is coupled to
the first and second end members with the tether disposed beneath
the first and second endplate contact surfaces.
6. The implant of claim 1 wherein the collapsible intermediate
section comprises a mesh member secured about a perimeter of the
first and second end members.
7. The implant of claim 1 wherein the collapsible intermediate
section maintains the first size to space the first and second end
members the first distance apart when the inflatable member is not
expanded through the introduction of the substance.
8. The implant of claim 1 wherein the collapsible intermediate
section comprises attachment members slidably engaged to permit
movement of the end members in an expansion direction, the
attachment members including position locks at predetermined
heights to stabilize the implant.
9. An implant for insertion between vertebral body endplates in a
patient, the implant comprising: a first end member including a
first endplate contact surface; a second end member including a
second endplate contact surface; a collapsible intermediate section
disposed between the first and second end members, the intermediate
section including an opening; and an interior member positionable
within the intermediate section, the interior member inflatable
between a compressed size in which the interior member will pass
through the opening and an expanded size in which the interior
member will not pass through the opening.
10. The implant of claim 9 wherein the collapsible intermediate
section is flexible.
11. The implant of claim 9 wherein the collapsible intermediate
section comprises a plurality of tethers secured about a perimeter
of the first and second end members, the distance between adjacent
tethers forming the opening.
12. The implant of claim 9 wherein the collapsible intermediate
section comprises a single tether coupled between a perimeter of
the first and second end members in a plurality of runs, the
distance between adjacent runs forming the opening.
13. The implant of claim 12 wherein the single tether is coupled to
the first and second end members with the tether disposed beneath
the first and second endplate contact surfaces.
14. The implant of claim 9 wherein the collapsible intermediate
section comprises a mesh member secured about a perimeter of the
first and second end members.
15. The implant of claim 9 wherein when the interior member is at
the compressed size, the first and second end members are a first
distance apart and when the interior member is at the expanded
size, the first and second end members are a second greater
distance apart.
16. The implant of claim 15 wherein the collapsible intermediate
section maintains the first and second end members the first
distance apart when the interior member is at the compressed
size.
17. The implant of claim 9 wherein the collapsible intermediate
section comprises attachment members slidably engaged to permit
movement of the end members in an expansion direction, the
attachment members including position locks at predetermined
heights to stabilize the implant.
18. A method of supporting vertebral bodies, the method comprising
the steps of: positioning an implant between endplates of the
vertebral members while the implant is in a first orientation
having a first height; inserting an inflatable member through an
opening in the implant; introducing a substance into the inflatable
member; inflating the inflatable member to an expanded size in
which the inflatable member is captively retained within the
implant; and separating first and second end members and increasing
a height of the implant.
19. The method of claim 18 wherein the substance includes a bone
growth promoting substance.
20. The method of claim 18 wherein the step of separating first and
second end members and increasing a height of the implant comprises
forcing a bone-contact surface of the first and second end members
into contact with the endplates of the vertebral members.
21. The method of claim 18 wherein the step of separating first and
second end members and increasing a height of the implant comprises
extending a collapsible intermediate section that is coupled
between the end members.
22. The method of claim 18 wherein the step of separating first and
second end members and increasing a height of the implant comprises
extending a tether that is coupled between the end members.
23. A method of supporting vertebral members, the method comprising
the steps of: coupling first and second end members with a
collapsible intermediate section; positioning an inflatable member
within the collapsible intermediate section; inserting an amount of
a substance into the inflatable member; filling the inflatable
member with the substance and causing the inflatable member to
contact faces of the first and second end members; exerting an
expansion force at the faces and expanding the collapsible
intermediate section and separating the first and second end
members to an increased height; and further expanding the first and
second members into contact with the vertebral members.
24. The method of claim 23 wherein the substance includes a bone
growth promoting substance.
25. The method of claim 23 wherein prior to filling the inflatable
member with the substance and causing the inflatable member to
contact faces of the first and second end members, the inflatable
member is sized to pass through an opening in the collapsible
intermediate section.
26. The method of claim 23 wherein the step of exerting an
expansion force at the faces and expanding the collapsible
intermediate section comprises extending a tether that is coupled
between the first and second end members.
Description
BACKGROUND
[0001] Spinal implants are often used in the surgical treatment of
spinal disorders such as degenerative disc disease, disc
herniations, scoliosis or other curvature abnormalities, and
fractures. Many different types of treatments are used, including
the removal of one or more vertebral bodies and/or intervertebral
disc tissue. In some cases, spinal fusion is indicated to inhibit
relative motion between vertebral bodies. In other cases, dynamic
implants are used to preserve motion between vertebral bodies. In
yet other cases, relatively static implants that exhibit some
degree of flexibility may be inserted between vertebral bodies.
[0002] Regardless of the type of treatment and the type of implant
used, surgical implantation tends to be a difficult for several
reasons. For instance, access to the affected area may be limited
by other anatomy. Further, a surgeon must be mindful of the spinal
cord and neighboring nerve system. The size of the implant may
present an additional obstacle. In some cases, a surgeon may
discover that an implanted device has an inappropriate size for a
particular application, which may require removal of the implant
and insertion of a different implant. This trial and error approach
may increase the opportunity for injury and is certainly
time-consuming. Expandable implants are becoming more prevalent as
a response to some of these concerns. However, the expansion
mechanism in these devices tends to be complex and large.
Consequently, existing devices do not appear to address each of
these issues in a manner that improves the ease with which the
device may be surgically implanted.
SUMMARY
[0003] Illustrative embodiments disclosed herein are directed to an
implant for insertion between vertebral body endplates. The implant
may include first and second end members, each with a respective
endplate contact surface. The implant may further include a
collapsible intermediate section disposed between the first and
second end members and an inflatable member contained within the
intermediate section. The collapsible intermediate section may be
flexible and may be implemented using, for example, a continuous
threaded tether, multiple tethers, or a mesh member. The
collapsible intermediate section may be compliant or semi-rigid and
naturally assume a compressed, but expandable insertion height. The
intermediate section may be expandable upon the introduction of a
substance into the inflatable member between a first size to space
the first and second end members a first distance apart and a
second enlarged size to space the first and second end members a
second greater distance apart. The inflatable member may increase
in size from a compressed size in which the inflatable member will
pass through an opening in the intermediate section and an expanded
size in which the inflatable member will not pass through the
opening and is thereby captively retained within the intermediate
section.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a side elevation view of a vertebral implant
according to one embodiment positioned between vertebral
bodies;
[0005] FIG. 2 is a section view of the vertebral implant according
to the section lines in FIG. 1;
[0006] FIG. 3 is a perspective view of an exploded vertebral
implant assembly according to one embodiment;
[0007] FIGS. 4-6 illustrate a sequence of implantation steps to
obtain a desired vertebral body spacing, each Figure depicting a
lateral view of a vertebral implant according to one or more
embodiments shown relative to vertebral bodies;
[0008] FIG. 7 is a side view of a vertebral implant assembly
according to one embodiment;
[0009] FIG. 8 is a top view of a vertebral implant assembly
according to one embodiment;
[0010] FIG. 9 is a perspective view of one embodiment of a
vertebral implant; and
[0011] FIG. 10 is a side view of a vertebral implant assembly
according to one embodiment.
DETAILED DESCRIPTION
[0012] The various embodiments disclosed herein are directed to
vertebral implants that are characterized by at least one
expandable portion. The expandable portion may be assume a
compressed first state during installation of the implant and may
be expanded once the implant is positioned within the body. An
exemplary implant 10 for supporting vertebral bodies is illustrated
in FIG. 1. In one embodiment, the implant 10 is a vertebrectomy or
corpectomy cage assembly positionable within an intervertebral
space to span one or more vertebral levels along the longitudinal
axis of the spinal column. Although the illustrated embodiment of
the implant 10 spans one vertebral level, it should be understood
that the implant 10 may be configured to span multiple vertebral
levels.
[0013] FIGS. 1-3 illustrate that the implant 10 generally includes
a first end member 22, a second end member 24, and one or more
expandable portions 26 between the first and second end members 22,
24. In one embodiment, the end members 22, 24 are formed of a
biocompatible material, such as, for example, a carbon fiber
material, or non-metallic substances, including polymers or
copolymers made from materials such as PEEK and UHMWPE. In further
embodiments, the end members 22, 24 may be formed of other suitable
materials, such as, for example, stainless steel, titanium,
cobalt-chrome, and shape memory alloys or other biocompatible
metals.
[0014] The end members 22, 24 are adapted to engage the endplates
of upper and lower vertebral bodies V1, V2. The expandable portion
26 is engaged between the end members 22, 24 to maintain an
intervertebral axial space S between the upper and lower vertebral
bodies V1, V2 following the removal of one or more vertebral levels
(shown in phantom in FIG. 1). Generally, the expandable portion 26
includes a collapsible portion 41 and an inflatable portion 35. In
the embodiment shown, the collapsible portion 41 includes a series
of cords or tethers 42 and the inflatable portion 35 includes a
balloon-like structure 36. A plurality of tethers 42 may extend
around the perimeter 52 of the end members to form a cage. To
facilitate insertion of the implant 10, the expandable portion 26
may be collapsed relative to the extended state shown in FIG. 1.
Further details regarding process steps for insertion of the
implant 10 are provided below.
[0015] The expandable portion 26 is expandable in a direction that
is substantially transverse to the bone contact surfaces 32, 34 of
the end members 22, 24. The bone contact surfaces 32, 34 of the end
members 22, 24 may be planar or define surface features and/or a
number of anchor elements 80 adapted for engagement with the
vertebral endplates to inhibit movement of the end members 22, 24
relative to the vertebral bodies V1, V2. For example, in one
embodiment, the bone contact surfaces 32, 34 may be roughened, such
as, for example, by knurling and/or etching (e.g., photochemical
etching). In other embodiments, various types of projections or
protrusions may extend from the bone contact surfaces 32, 34, such
as, for example, a number of spikes, ridges, teeth, axial grooves,
checkerboard-type grooves, or any other type of anchoring element
80 that would occur to one of skill in the art. Although the bone
contact surfaces 32, 34 of the end members 22, 24 are illustrated
in FIGS. 1 and 3 as being arranged substantially planar, it should
be understood that the bone contact surfaces 32, 34 may be tapered
or curved to more closely conform with the anatomical curvature of
the vertebral bodies V1, V2 at the surgical site.
[0016] In one or more embodiments, the implant 10 may be expanded
through the introduction of an injectable substance that fills an
inflatable balloon-like member 36, thereby causing the end members
22, 24 to move opposite one another. The number 90 in FIG. 2
identifies the injectable substance, which fills the balloon-like
member 36. In the embodiment shown, the balloon-like member 36
includes a size and shape to fit within the end members 22, 24.
Further, the balloon-like member 36 includes a compressed size (see
dimension B) that is small enough to fit between adjacent tethers
42 (see dimension T) and an expanded size that is larger than the
spacing between adjacent tethers 42. Accordingly, the expanded
balloon-like member 36 is captively retained between the end
members 22, 24 and inside the tethers 42.
[0017] The end members 22, 24 include similar shapes, which permits
the end members 22, 24 to fit the vertebral bodies V1, V2 in a
similar manner. The end members 22, 24 generally include respective
bone contact surfaces 32, 34 and an opposing surface 54 facing
opposite the bone-contact surfaces 32, 34, and a peripheral wall 52
extending therebetween. In the illustrated embodiment, the end
members 22, 24 include a kidney shape, though other shapes may be
used. In further embodiments, the end members 22, 24 may take on
other types of configurations, such as, for example, a circular
shape, semi-oval shape, bean-shape, D-shape, elliptical-shape,
egg-shape, or any other shape that would occur to one of skill in
the art. In other embodiments, the end members 22, 24 could also be
described as being annular, U-shaped, C-shaped, V-shaped,
horseshoe-shaped, semi-circular shaped, semi-oval shaped, or other
similar terms defining an implant including at least a partially
open or hollow construction. Thus, end members 22, 24 may be
constructed for use in a variety of procedures, including but not
limited to those requiring an anterior approach, a lateral
approach, a posterior approach, or a trans-foraminal approach.
[0018] It should further be appreciated that the size and/or
configuration of the end members 22, 24 may be specifically
designed to accommodate any particular region of the spinal column
and/or any particular vertebral level. For example, in embodiments
associated with the upper thoracic or cervical region of the spine,
the end members 22, 24 may be designed to have a D-shaped
configuration, whereas embodiments associated with the lumbar
region of the spine may be configured to have a horseshoe-shape, a
U-shape, or other types of open-sided configurations.
[0019] In one embodiment, the end members 22, 24 have an outer
profile that is substantially complementary to the size and shape
of the peripheral portion or outlying region of the vertebral
bodies V1, V2, such as the cortical rim or the apophyseal ring of
the vertebral endplates. For example, as illustrated in FIG. 2, the
outer perimeter of the end member 24 is preferably disposed
generally above the inner edge of the cortical rim R of the
vertebral body V1. In this manner, at least a portion of the end
members 22, 24 is engaged against the cortical region of the
vertebral endplates, thereby minimizing the likelihood of
subsidence into the relatively softer cancellous region of the
vertebral bodies V1, V2 following insertion of the implant 10
within the intervertebral space S.
[0020] Additionally, each of the bone contact surfaces 32, 34 may
include one or more apertures or recesses 50 formed by an inner
surface 82. The recess 50 is open at the bone contact surfaces 32,
34 and provided to enhance bony fusion between the end members 22,
24 and vertebral bodies V1, V2. The recesses 50 may be blind holes
in that they do not extend through the end members 22, 24. The
recesses 50 may be through-holes in that they do extend through the
end members 22, 24. In one or more implementations, the implant 10
may be inserted in conjunction with bone growth materials that may
include, for example, bone graft, bone morphogenetic protein (BMP),
allograft, autograft, and various types of cement, growth factors
and mineralization proteins. In a further embodiment, the bone
growth promoting materials may be provided in a carrier (not
shown), such as, for example, a sponge, a block, a cage, folded
sheets, or paste. The bone growth materials may be loaded into the
apertures 50 or generally applied to the bone-contact surfaces 32,
34.
[0021] The tethers 42 may be constructed of a complaint
biocompatible material, such as a resin or polymer that may include
materials such as nylon, polyethylene, polyurethane, silicone,
polyethylene, polypropylene, polyimide, polyamide, and
polyehteretherketone (PEEK). Further, the tethers 42 may be
constructed of a wide variety of woven or nonwoven fibers, fabrics,
metal mesh such as woven or braided wires, polymeric fibers,
ceramic fibers, and carbon fibers. Biocompatible fabrics or sheet
material such as ePTFE and Dacron.RTM., Spectra.RTM., and
Kevlar.RTM. may also be used. The tethers 42 may be cable-like,
with a circular cross section or tape-like with a flattened cross
section. Other cross sections may be possible or desirable,
including for example, triangular, rectangular, polygonal,
elliptical, or other cross sections. Furthermore, the tethers 42
may be secured to one or both of the end members 22, 24 using a
variety of methods, including for example, tying, adhering,
welding, or other methods that would occur to one skilled in the
art.
[0022] The tethers 42 may be compliant in that they assume a shape
that is determined by the spacing between the end members 22, 24.
That is, the tethers 42 may be similar to a rope or thread and
assume a random shape when the end members 22, 24 are brought in
proximity to one another. In one embodiment, the tethers 42 are
semi-rigid in that they assume a particular bent, curved, or
splined shape to maintain a compressed height between the end
members 22, 24. However, as the end members 22, 24 are pushed
apart, such as by inflating the balloon-like structure 36, the
tethers 42 will straighten to allow the end members 22, 24 to
separate. Those skilled in the art will comprehend that a
semi-rigid characteristic may be obtained through the use of
flexible resin or composite materials or through the use of a thin
metal filament, rod, or spring (not explicitly shown).
[0023] The balloon-like structure 36 may be constructed of a
complaint biocompatible material, such as a resin or polymer that
may include materials such as nylon, polyethylene, polyurethane,
silicone, polyethylene, polypropylene, polyimide, polyamide, and
polyehteretherketone (PEEK). The balloon-like structure 36 may be
formed from materials that are used in other conventionally known
biomedical applications, such as balloon angioplasty. Further, the
balloon-like structure 36 may be reinforced with concentric layers
of similar or dissimilar materials and/or fabrics (not specifically
shown). For instance, a reinforcing structure may be constructed of
a wide variety of woven or nonwoven fibers, fabrics, metal mesh
such as woven or braided wires, polymeric fibers, ceramic fibers,
and carbon fibers. Biocompatible fabrics or sheet material such as
ePTFE and Dacron.RTM., Spectra.RTM., and Kevlar.RTM. may also be
used. Furthermore, the balloon-like structure 36 may be a separate
member or may be secured to one or both of the end members 22,
24.
[0024] In one embodiment, the balloon-like structure 36 includes
permeable end surfaces 39. That is, the end surfaces 39 include a
perforated, grated, or mesh-like structure that allows the
injectable substance 90 to pass from within the balloon-like
structure 36 and through the apertures 50 to contact the
corresponding vertebral bodies V1, V2 (see e.g., FIG. 1). In one
embodiment, most or all of the balloon-like structure 36 is
permeable in a similar manner. In one embodiment, no portion of the
balloon-like structure is permeable (i.e., the injectable substance
is substantially contained therein). The permeable nature of at
least the end surfaces 39 makes it advantageous to include bone
growth promoting materials within the injectable substance 90.
Accordingly, as the injectable substance 90 is inserted into the
balloon-like structure 36, the end members 22, 24 will expand under
the influence of the expanding balloon-like structure 36.
Additionally, some of the injectable substance 90 will exit the
permeable end surfaced 39 and enter the apertures 50. Consequently,
growth-promoting materials contained therein are positioned to
enhance bone growth from adjacent vertebral bodies V1, V2 into the
implant 10. In one embodiment, the permeable end surfaces 39 may be
configured to contain the injectable substance 90 until a certain
internal pressure is obtained. Beyond that pressure, obtained
through introducing additional injectable substance 90, the
injectable substance 90 will exit the end surfaces 39 and enter the
apertures 50.
[0025] Various techniques may be used to introduce an injectable
substance 90 into the balloon-like structure 36. In the embodiment
shown, a fill port 52 is provided on the balloon-like structure 36.
Notably, while only one fill port 52 is depicted, additional ports
52 may be used. Further, the port 52 may be located in different
locations depending on a particular implementation and angle of
approach. The fill port 52 may be attached to a syringe or other
pumping mechanism (see FIGS. 4-6) to fill the balloon-like
structure 36. An injectable substance may flow through the fill
port 52 into the interior volume of the balloon-like structure 36.
As the injectable substance fills the balloon-like structure 36,
the ends 39 of the balloon-like structure 36 extend to contact the
end members 22, 24 and may expand to fill the recesses 50 formed
within the end members 22, 24. As the ends 39 of the balloon-like
structure 36 expand, they exert a displacement force F that causes
the end members 22, 24 to separate from one another. Furthermore,
fill port 52 may include a self-sealing valve (not specifically
shown) that prevents the injectable substance from flowing in one
direction or another once the balloon-like structure 36 is
filled.
[0026] A variety of injectable substances may be inserted into the
balloon-like structure 36 to cause the end members 22, 24 to
separate. In one embodiment, the injectable substance is a fluid,
such as a gas or a liquid. In one embodiment, the injectable
substance is a solid, such as a powder. In one embodiment, the
injectable substance is a curable liquid that solidifies after a
predetermined amount of time or under the influence of an external
catalyst. For instance, an injectable liquid may cure under the
influence of heat or light, including ultraviolet light. Some
examples of in situ curable liquids include epoxy, PMMA,
polyurethane, and silicone. A curable substance may cure to a
substantially rigid state or to a flexible, but relatively
incompressible state.
[0027] The implant 10 may be inserted into a patient according to
the process steps illustrated in FIGS. 4-6. In FIG. 4, the implant
10 is inserted in a compressed first state including a first height
H1 and positioned within an intervertebral space formed after the
removal of one or more vertebrae or discs. Once the implant 10 is
positioned as shown in FIG. 4, the inflation tool 100 or other
injection instrument is used to position the balloon-like structure
36 and inject the injectable substance into the fill port 52 on the
balloon-like structure 36. As suggested above, the balloon-like
structure 36 is collapsed and is able to fit between end members
22, 24 through the spacing T1 between tethers 42. Note that in the
collapsed first state with a height H1, the tethers 42 may be
compliant and may be separated to insert the balloon-like member
36.
[0028] In one embodiment, a single tool 100 is used to position and
fill the balloon-like structure. In one embodiment, the
balloon-like structure is positioned between the end members 22, 24
using a different tool (not shown) than the inflation tool 100. In
one embodiment, the balloon-like member 36 is pre-positioned
between the end members 22, 24 and inserted into the intervertebral
space along with the end members 22, 24.
[0029] The inflation tool 100 may be implemented as a syringe-like
structure including a reservoir portion 102 and a delivery portion
104. The delivery portion 104 is configured to engage the fill port
52 to transfer the injectable substance from the reservoir portion
102 into the balloon-like structure 36. Other delivery mechanisms
are certainly appropriate. For instance, pneumatic or hydraulic
fittings may be appropriate. The delivery portion 104 may be
implemented as a needle, as tubing, or other cannulated devices. In
any event, as the injectable substance is introduced into the
implant 10, the end members 22, 24 are forced apart due to the
expansion of the contained balloon-like structure 36. Ultimately,
the implant 10 is expanded to an expanded second state including a
second height H2 as shown in FIG. 6. In the expanded second state
with a height H2, the tethers 42 may pulled somewhat taught and the
spacing T2 between adjacent tethers is sufficiently maintained to
captively retain the balloon-like member 36.
[0030] FIG. 7 depicts a top (or bottom) view of an exemplary end
member 22A or 24A for use in the vertebral implant 10. In previous
embodiments, the end members 22, 24 included an open recess 50. In
the embodiment illustrated in FIG. 7, the recess 50 is covered by a
permeable member 60 that provides a physical barrier to expansion
by the balloon-like structure but that permits fluid flow and bony
ingrowth. The permeable member 60 may be constructed of a braided
or mesh-like biocompatible material, such as a resin or polymer
that may include materials such as nylon, polyethylene,
polyurethane, silicone, polyethylene, polypropylene, polyimide,
polyamide, and polyehteretherketone (PEEK). Further, the permable
member 60 may be reinforced with layers of similar or dissimilar
materials and/or fabrics (not specifically shown). For instance, a
reinforcing structure may be constructed of a wide variety of woven
or nonwoven fibers, fabrics, metal mesh such as woven or braided
wires, polymeric fibers, ceramic fibers, and carbon fibers.
Biocompatible fabrics or sheet material such as ePTFE and
Dacron.RTM., Spectra.RTM., and Kevlar.RTM. may also be used.
[0031] In embodiments described above, the expandable portion 26
included a collapsible portion 41 comprised of a series of cords or
tethers 42. In the embodiment shown in FIG. 8, the collapsible
portion 41 includes a mesh-like member 142 that is secured to end
members 22B, 24B. The mesh-like member 142 is generally compliant
and may be collapsed and extended to permit the overall implant 10B
to assume compressed and extended heights H1, H2 as shown in FIGS.
4 and 6. The mesh-like member 142 may be constructed from materials
disclosed herein or using a variety of other biocompatible
materials known to those skilled in the art. The mesh-like member
142 is provided with an opening 144 through which the balloon-like
member 36 may be inserted. As with the previously-described tethers
42, the opening 144 is advantageously sized to permit a collapsed
balloon-like member 36 to pass, but small enough to prevent an
inflated balloon-like member 36 from escaping.
[0032] FIG. 9 depicts an embodiment of an implant 10C similar to
the embodiments depicted in FIGS. 1-3. However, in the present
embodiment, the tether 42A is provided as a continuous member that
is threaded through and between the illustrated end members 22C,
24C. Note that the single tether 42A is threaded through the end
members 22C, 24C with individual runs 43 of the tether 42A
functioning as the separate tethers 42 in above-described
embodiments. The illustrated tether 42A may be implemented as a
continuous member, passing through tether holes 200 and at least
partially passing through tether channels 202 in the end members
22C, 24C. Notably, the channels 202 may be recessed below the
bone-contact surfaces 32C, 34C to allow the bone-contact surfaces
32C, 34C to directly contact the corresponding endplates on the
vertebral bodies. The ends of the tether 142 may be secured to each
other using a variety of methods, including for example, tying,
adhering, crimping, soldering, welding, or other methods that would
occur to one skilled in the art.
[0033] FIG. 10 depicts an embodiment of an implant 10D in which the
collapsible portion 41 includes sliding and telescoping attachment
members 170, 172, respectively. In one embodiment, the attachment
members 170, 172 are rigid and capable of axially sliding relative
to one another according to the arrows labeled M. Further, because
the attachment members 170, 172 are rigid, the end members 22D, 24D
are maintained in a predetermined alignment relative to each other.
In one embodiment, attachment members 170, 172 are flexible members
that are capable of axially sliding relative to one another as well
as lateral bending. Consequently, the end members 22D, 24D remain
coupled, but are movable relative to each other in multiple
directions.
[0034] In certain implementations, where the injectable substance
remains fluid or takes an extended period of time to cure, the end
members 22D, 24D are provided with position locks 156, 158. In one
embodiment, attachment member 172 includes protruding features 156
and attachment member 170 includes recessed features 158 disposed
at various heights about the interior thereof. Thus, when the
attachment members 170, 172 are joined to one another, the
protruding features 156 engage the recessed features 158 to provide
a locked height that prevents compression of the implant 10D. That
is, as the balloon-like structure 36 is filled with an injectable
substance, the end members 22D, 24D will separate and expand to a
position where a protrusion 156 engages a recess 158. At this
point, introducing additional injectable substance will force the
protrusion 156 to disengage from the recess 158 and ultimately
engage a next higher recess 158. The protrusions 156 and/or the
recesses 158 may be angled, tapered, or oriented to permit
expansion of the implant 10D but not compression in the reverse
direction. Those skilled in the art will comprehend a variety of
ways to implement this type of unidirectional locking. The
protruding features 156 may be implemented using a variety of
features, including but not limited to ball plungers, expanding
pegs, protruding stops, and shape-memory alloys. In the latter
case, the protruding features 156 may be positioned in a first
retracted position and then, upon the application of elevated
temperatures (which may be provided by body temperatures), the
protruding feature 156 will expand to engage a recess 158
corresponding to a desired implant height.
[0035] Spatially relative terms such as "under", "below", "lower",
"over", "upper", and the like, are used for ease of description to
explain the positioning of one element relative to a second
element. These terms are intended to encompass different
orientations of the device in addition to different orientations
than those depicted in the figures. Further, terms such as "first",
"second", and the like, are also used to describe various elements,
regions, sections, etc and are also not intended to be limiting.
Like terms refer to like elements throughout the description.
[0036] As used herein, the terms "having", "containing",
"including", "comprising" and the like are open ended terms that
indicate the presence of stated elements or features, but do not
preclude additional elements or features. The articles "a", "an"
and "the" are intended to include the plural as well as the
singular, unless the context clearly indicates otherwise.
[0037] The present invention may be carried out in other specific
ways than those herein set forth without departing from the scope
and essential characteristics of the invention. For instance, the
embodiments disclosed herein have contemplated a single implant
positioned between vertebral bodies V1, V2. In other embodiments,
two or more smaller implants may be inserted between the vertebral
bodies V1, V2. The present embodiments are, therefore, to be
considered in all respects as illustrative and not restrictive, and
all changes coming within the meaning and equivalency range of the
appended claims are intended to be embraced therein.
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