U.S. patent application number 11/633131 was filed with the patent office on 2007-07-12 for flexible elongated chain implant and method of supporting body tissue with same.
Invention is credited to Dominique Messerli.
Application Number | 20070162132 11/633131 |
Document ID | / |
Family ID | 38147568 |
Filed Date | 2007-07-12 |
United States Patent
Application |
20070162132 |
Kind Code |
A1 |
Messerli; Dominique |
July 12, 2007 |
Flexible elongated chain implant and method of supporting body
tissue with same
Abstract
Implants and methods for augmentation, preferably by minimally
invasive procedures and means, of body tissue, including in some
embodiments repositioning of body tissue, for example, bone and,
preferably vertebrae are described. The implant may comprise one or
more chain linked bodies inserted into the interior of body tissue.
As linked bodies are inserted into body tissue, they may fill a
central portion thereof and for example in bone can push against
the inner sides of the cortical exterior surface layer, for example
the end plates of a vertebral body, thereby providing structural
support and tending to restore the body tissue to its original or
desired treatment height. A bone cement or other filler can be
added to further augment and stabilize the body tissue. The
preferred implant comprises a single flexible monolithic chain
formed of allograft cortical bone having a plurality of
substantially non-flexible bodies connected by substantially
flexible links.
Inventors: |
Messerli; Dominique;
(Downingtown, PA) |
Correspondence
Address: |
JONES DAY
222 EAST 41ST STREET
NEW YORK
NY
10017-6702
US
|
Family ID: |
38147568 |
Appl. No.: |
11/633131 |
Filed: |
December 1, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60753782 |
Dec 23, 2005 |
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60810453 |
Jun 2, 2006 |
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Current U.S.
Class: |
623/17.11 |
Current CPC
Class: |
A61B 17/68 20130101;
A61F 2/44 20130101; A61B 2017/00004 20130101; A61F 2/3609 20130101;
A61B 2017/00526 20130101; A61F 2250/0003 20130101; A61F 2002/30593
20130101; A61F 2210/0004 20130101; A61F 2/447 20130101; A61F 2/4465
20130101; A61F 2002/4415 20130101; A61F 2/441 20130101; A61F 2/442
20130101; A61F 2/4455 20130101; A61B 17/7094 20130101 |
Class at
Publication: |
623/017.11 |
International
Class: |
A61F 2/44 20060101
A61F002/44 |
Claims
1. An apparatus for augmentation of body tissue comprising: a
flexible elongated member having a longitudinal length
substantially larger than its height or its width, wherein the
member comprises: a plurality of substantially non-flexible bodies;
and a plurality of substantially flexible links interconnecting the
bodies, the bodies and links connected end-to-end to form the
elongated member, wherein the elongated member is formed of a
biocompatible material.
2. The apparatus of claim 1 wherein the elongated member is formed
as an integral monolithic chain.
3. The apparatus of claim 2 wherein the monolithic chain is formed
of bone.
4. The apparatus of claim 3, wherein the monolithic chain is formed
of allograft bone.
5. The apparatus of claim 4 wherein the flexible links are formed
of bone that has been demineralized to a greater extent than the
bodies.
6. The apparatus of claim 5 further comprising a coating applied to
at least a portion of the elongated member.
7. The apparatus of claim 6 wherein the coating comprises at least
one of the group selected from a therapeutic agent, a bone cement,
an antibiotic, and a bone growth stimulating substance.
8. The apparatus of claim 7 wherein the coating comprising a bone
cement that may be activated upon insertion into the body
tissue.
9. The apparatus of claim 4 wherein at least a portion of the
bodies comprise an outer surface configured to promote bone
in-growth.
10. The apparatus of claim 1, wherein the bodies are larger in size
than the links, and chain is bendable such that adjacent bodies can
touch without breaking or cracking the chain.
11. The implant of claim 1 insertable into bone.
12. The implant of claim 1 insertable between two vertebrae.
13. An apparatus for augmenting a body tissue comprising an
elongated member having a longitudinal length greater than either
its height or width, the elongated member formed of allograft bone
and comprising: a plurality of bodies and a plurality of links
interconnecting the bodies wherein the links are more flexible and
have a greater degree of demineralization than the bodies.
14. The apparatus of claim 13 wherein the bodies have a first
cross-sectional size and the links have a second cross-sectional
size, the first cross-sectional size being larger than the second
cross-sectional size.
15. The apparatus of claim 13 wherein the elongated member has a
length between about 40 mm and about 150 mm, a maximum height
between about 2 mm and about 8 mm, and a maximum width of between
about 3 mm and about 8 mm.
16. The apparatus of claim 13 further comprising a bone cement
coating covering at least a portion of the elongated member wherein
the coating has an active state and inactive state, the bone cement
being user controlled to change from the inactive state to the
active state, the active state permitting the cement to attach to
another surface.
17. A method of treating osteoporotic bone comprising: providing a
monolithic, flexible, elongated member having a longitudinal length
greater than either its height or its width, the elongated member
formed of allograft bone comprising a plurality of bodies connected
together by a plurality of links wherein the links are located
between the bodies and the links have a greater degree of
demineralization and flexibility than the bodies, inserting the
elongated member into the interior of the bone.
18. The method of claim 17 wherein the elongated member is inserted
along its longitudinal length.
19. The method of claim 17 wherein the elongated member is inserted
simultaneously with bone cement that will cure to a hardened state
in situ in the interior of the bone.
20. The method of claim 19 wherein at least a portion of the
elongated member extends from the bone.
21. The method of claim 17 wherein the elongated member is inserted
through a cannula into the interior of a vertebrae.
22. The method of claim 17 wherein the elongated member is inserted
with sufficient force to move at least a portion of the cortical
exterior surface of the bone.
23. The method of claim 17 further comprising: creating an opening
in the cortical exterior surface of a bone; and creating a cavity
within the interior of the bone.
24. The method of claim 23 wherein the step of creating the cavity
comprises compacting bone cells within the bone.
25. The method of claim 17 further comprising inserting at least
one selected from the group of bone chips, therapeutic agents,
bone-stimulating agents and antibiotics into the interior of the
bone.
26. The method of claim 17 further comprising: creating an opening
in the exterior surface of the bone; creating a passageway from the
opening to the interior of the bone; and filling at least one of
the opening and the passageway with a plug of bone cement to
prevent the escape of the elongated member from the interior of the
bone.
27. The method of claim 17 wherein the step of inserting the
elongated member comprises bending the plurality of links so that
the bodies within the interior of the bone contact each other.
28. The method of claim 27 wherein the bodies are larger in size
than the links.
29. The method of claim 28 wherein after the step of inserting the
elongated member into the interior of the bone, the method further
comprises inserting at least one selected from the group of bone
cement, and bone chips.
30. A method of treating the spine comprising: providing a flexible
elongated member having a longitudinal length greater than its
height or width, the elongated member formed of allograft bone
comprising a plurality of bodies connected together by a plurality
of links wherein the links are located between the bodies and the
links have a greater degrees of demineralization and flexibility
than the bodies; and inserting the elongated member between two
adjacent vertebrae.
31. The method of claim 30 further comprising inserting the
elongated member into the annulus of a spinal disc.
32. The method of claim 30 wherein the bodies are larger than the
links.
33. The method of claim 30 wherein at least one elongated member is
formed from a single allograft bone as an integral monolithic
structure.
34. A method of manufacturing an allograft bone implant comprising:
machining from bone an elongated member having a longitudinal
length greater than either its height or width, the elongated
member having a plurality of bodies connected together by a
plurality of links wherein the links are located between the bodies
and the bodies are connected along a line in end-to-end
fashion.
35. The method according to claim 34 wherein the bodies have a
larger volume than the links and the elongated member is formed
from the same bone as one single monolithic implant.
36. The method of claim 35 wherein the step of demineralizing the
elongated member comprising exposing a plurality of the bodies and
a plurality of the links to the same demineralizing solution for
substantially the same amount of time.
37. The method of claim 36 wherein the links are fully
demineralized.
38. The method of claim 34 further comprising: covering the
plurality of bodies to prevent the bodies from being subject to
demineralizing solution, and exposing the links and covered bodies
to demineralizing solution.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application No. 60/753,782, filed Dec. 23, 2005 and U.S.
Provisional Application No. 60/810,453, filed Jun. 2, 2006, the
entirety of each of which is incorporated by reference herein.
FIELD OF THE INVENTION
[0002] The invention relates to implants, and more particularly to
flexible chain implants for augmenting or supporting bones or other
structures, such as, for example vertebral discs.
BACKGROUND OF THE INVENTION
[0003] Vertebral compression fractures, as illustrated in FIG. 1,
represent a generally common spinal injury and may result in
prolonged disability. These fractures involve collapsing of one or
more vertebral bodies 12 in the spine 10. Compression fractures of
the spine usually occur in the lower vertebrae of the thoracic
spine or the upper vertebra of the lumbar spine. They generally
involve fracture of the anterior portion 18 of the affected
vertebra 12 (as opposed to the posterior side 16). Spinal
compression fractures can result in deformation of the normal
alignment or curvature, e.g., lordosis, of vertebral bodies in the
affected area of the spine. Spinal compression fractures and/or
related spinal deformities can result, for example, from metastatic
diseases of the spine, from trauma or can be associated with
osteoporosis. Until recently, doctors were limited in how they
could treat such compression fractures and related deformities.
Pain medications, bed rest, bracing or invasive spinal surgery were
the only options available.
[0004] More recently, minimally invasive surgical procedures for
treating vertebral compression fractures have been developed. These
procedures generally involve the use of a cannula or other access
tool inserted into the posterior of the effected vertebral body,
usually through the pedicles. The most basic of these procedures is
vertebroplasty, which literally means fixing the vertebral body,
and may be done without first repositioning the bone.
[0005] Briefly, a cannula or special bone needle is passed slowly
through the soft tissues of the back. Image guided x-ray, along
with a small amount of x-ray dye, allows the position of the needle
to be seen at all times. A small amount of polymethylmethacrylate
(PMMA) or other orthopedic cement is pushed through the needle into
the vertebral body. PMMA is a medical grade substance that has been
used for many years in a variety of orthopedic procedures.
Generally, the cement is mixed with an antibiotic to reduce the
risk of infection, and a powder containing barium or tantalum,
which allows it to be seen on the X-ray.
[0006] Vertebroplasty can be effective in the reduction or
elimination of fracture pain, prevention of further collapse, and a
return to mobility in patients. However, this procedure may not
reposition the fractured bone and therefore may not address the
problem of spinal deformity due to the fracture. It generally is
not performed except in situations where the kyphosis between
adjacent vertebral bodies in the effected area is less than 10
percent. Moreover, this procedure requires high-pressure cement
injection using low-viscosity cement, and may lead to cement leaks
in 30-80% of procedures, according to recent studies. In most
cases, the cement leakage does no harm. In rare cases, however,
polymethymethacrylate or other cement leaks into the spinal canal
or the perivertebral venous system and causes pulmonary embolism,
resulting in death of the patient.
[0007] More advanced treatments for vertebral compression fractures
generally involve two phases: (1) reposition, or restoration of the
original height of the vertebral body and consequent lordotic
correction of the spinal curvature; and (2) augmentation, or
addition of material to support or strengthen the fractured or
collapsed bone.
[0008] One such treatment, balloon kyphoplasty (Kyphon, Inc.), is
disclosed in U.S. Pat. Nos. 6,423,083, 6,248,110, and 6,235,043 to
Riley et al., each of which is incorporated by reference herein in
its entirety. A catheter having an expandable balloon tip is
inserted through a cannula, sheath or other introducer into a
central portion of a fractured vertebral body comprising relatively
soft cancellous bone surrounded by fractured cortical bone.
Kyphoplasty then achieves the reconstruction of the lordosis, or
normal curvature, by inflating the balloon, which expands within
the vertebral body restoring it to its original height. The balloon
is removed, leaving a void within the vertebral body, and PMMA or
other filler material is then injected through the cannula into the
void as described above with respect to vertebroplasty. The cannula
is removed and the cement cures to augment, fill or fix the
bone.
[0009] Disadvantages of this procedure include the high cost, the
repositioning of the endplates of the vertebral body may be lost
after the removal of the balloon catheter, and the possible
perforation of the vertebral endplates during the procedure. As
with vertebroplasty, perhaps the most feared, albeit remote,
complications concerning kyphoplasty are related to leakage of bone
cement. For example, a neurologic deficit may occur through leakage
of bone cement into the spinal canal. Such a cement leak may occur
through the low resistance veins of the vertebral body or through a
crack in the bone which was not appreciated previously. Other
complications include additional adjacent level vertebral
fractures, infection and cement embolization. Cement embolization
occurs by a similar mechanism to a cement leak. The cement may be
forced into the low resistance venous system and travel to the
lungs or brain resulting in a pulmonary embolism or stroke.
[0010] Another approach for treating vertebral compression
fractures is the Optimesh system (Spineology, Inc., Stillwater,
Minn.), which provides minimally invasive delivery of a cement or
allograft or autograft bone using an expandable mesh graft balloon,
or containment device, within the involved vertebral body. The
balloon graft remains inside the vertebral body after its
inflation, which prevents an intraoperative loss of reposition,
such as can occur during a kyphoplasty procedure when the balloon
is withdrawn. One drawback of this system, however, is that the
mesh implant is not well integrated in the vertebral body. This can
lead to relative motion between the implant and vertebral body, and
consequently to a postoperative loss of reposition. Additional
details regarding this procedure may be found, for example, in
published U.S. Patent Publication Number 20040073308, which is
incorporated by reference herein in its entirety.
[0011] Still another procedure used in the treatment of vertebral
compression fractures is an inflatable polymer augmentation mass
known as a SKy Bone Expander. This device can be expanded up to a
pre-designed size and (Cubic or Trapezoid) configuration in a
controlled manner. Like the Kyphon balloon, once optimal vertebra
height and void are achieved, the SKy Bone Expander is removed and
PMMA cement or other filler is injected into the void. This
procedure therefore entails many of the same drawbacks and
deficiencies described above with respect to kyphoplasty.
[0012] In some cases of fractured or otherwise damaged bones, bone
grafts are used to repair or otherwise treat the damaged area. In
the United States alone, approximately half a million bone grafting
procedures are performed annually, directed to a diverse array of
medical interventions for complications such as fractures involving
bone loss, injuries or other conditions necessitating
immobilization by fusion (such as for the spine or joints), and
other bone defects that may be present due to trauma, infection, or
disease. Bone grafting involves the surgical transplantation of
pieces of bone within the body, and generally is effectuated
through the use of graft material acquired from a human source.
This is primarily due to the limited applicability of xenografts,
transplants from another species.
[0013] Orthopedic autografts or autogenous grafts involve source
bone acquired from the same individual that will receive the
transplantation. Thus, this type of transplant moves bony material
from one location in a body to another location in the same body,
and has the advantage of producing minimal immunological
complications. It is not always possible or even desirable to use
an autograft. The acquisition of bone material from the body of a
patient typically requires a separate operation from the
implantation procedure. Furthermore, the removal of material,
oftentimes involving the use of healthy material from the pelvic
area or ribs, has the tendency to result in additional patient
discomfort during rehabilitation, particularly at the location of
the material removal. Grafts formed from synthetic material have
also been developed, but the difficulty in mimicking the properties
of bone limits the efficacy of these implants.
[0014] As a result of the challenges posed by autografts and
synthetic grafts, many orthopedic procedures alternatively involve
the use of allografts, which are bone grafts from other human
sources (normally cadavers). The bone grafts, for example, are
placed in a host bone and serve as the substructure for supporting
new bone tissue growth from the host bone. The grafts are sculpted
to assume a shape that is appropriate for insertion at the fracture
or defect area, and often require fixation to that area for example
by screws, pins, cement, cages, membranes, etc. Due to the
availability of allograft source material, and the widespread
acceptance of this material in the medical community, the use of
allograft tissues is likely to expand in the field of
musculoskeletal surgery.
[0015] Notably, the various bones of the body such as the femur
(thigh), tibia and fibula (leg), humerus (upper arm), radius and
ulna (lower arm) have geometries that vary considerably. In
addition, the lengths of these bones vary; for example, in an adult
the lengths may vary from 47 centimeters (femur) to 26 centimeters
(radius). Furthermore, the shape of the cross section of each type
of bone varies considerably, as does the shape of any given bone
over its length. While a femur has a generally rounded outer shape,
a tibia has a generally triangular outer shape. Also, the wall
thickness varies in different areas of the cross-section of each
bone. Thus, the use of any given bone to produce an implant
component may be a function of the bone's dimensions and geometry.
Machining of bones, however, may permit the production of implant
components with standardized or custom dimensions.
[0016] As a collagen-rich and mineralized tissue, bone is composed
of about forty percent organic material (mainly collagen), with the
remainder being inorganic material (mainly a near-hydroxyapatite
composition resembling 3Ca.sub.3(PO.sub.4).sub.2Ca(OH).sub.2).
Structurally, the collagen assumes a fibril formation, with
hydroxyapatite crystals disposed along the length of the fibril,
and the individual fibrils are disposed parallel to each other
forming fibers. Depending on the type of bone, the fibrils are
either interwoven, or arranged in lamellae that are disposed
perpendicular to each other.
[0017] Bone tissues have a complex design, and there are
substantial variations in the properties of bone tissues depending
upon the type of bone (i.e., leg, arm, vertebra) as well as the
overall structure. For example, when tested in the longitudinal
direction, leg and arm bones have a modulus of elasticity of about
17 to 19 GPa, while vertebra tissue has a modulus of elasticity of
less than 1 GPa. The tensile strength of leg and arm bones varies
between about 120 MPa and about 150 MPa, while vertebra have a
tensile strength of less than 4 MPa. Notably, the compressive
strength of bone varies, with the femur and humerus each having a
maximum compressive strength of about 167 MPa and 132 MPa
respectively. Again, the vertebra have a far lower compressive
strength usually of no more than about 10 MPa.
[0018] With respect to the overall structure of a given bone, the
mechanical properties vary throughout the bone. For example, a long
bone (leg bone) such as the femur has both compact bone and spongy
bone. Cortical bone, the compact and dense bone that surrounds the
marrow cavity, is generally solid and thus carries the majority of
the load in major bones. Cancellous bone, the spongy inner bone, is
generally porous and ductile, and when compared to cortical bone is
only about one-third to one-quarter as dense, one-tenth to
one-twentieth as stiff, but five times as ductile. While cancellous
bone has a tensile strength of about 10-20 MPa and a density of
about 0.7 g/cm.sup.3, cortical bone has a tensile strength of about
100-200 MPa and a density of about 2 g/cm.sup.3. Additionally, the
strain to failure of cancellous bone is about 5-7%, while cortical
bone can only withstand 1-3% strain before failure. It should also
be noted that these mechanical characteristics may degrade as a
result of numerous factors such as any chemical treatment applied
to the bone material, and the manner of storage after removal but
prior to implantation (i.e. drying of the bone).
[0019] Notably, implants of cancellous bone incorporate more
readily with the surrounding host bone, due to the superior
osteoconductive nature of cancellous bone as compared to cortical
bone. Furthermore, cancellous bone from different regions of the
body is known to have a range of porosities. For example,
cancellous bone in the iliac crest has a different porosity than
cancellous bone in a femoral head. Thus, the design of an implant
using cancellous bone may be tailored to specifically incorporate
material of a desired porosity.
[0020] There remains a need in the art to provide safe and
effective devices and methods for augmentation of fractured or
otherwise damaged vertebrae and other bones, preferably devices
that may be implanted utilizing minimally invasive methods of
implantation.
SUMMARY OF THE INVENTION
[0021] A flexible chain according to one embodiment comprises a
series or other plurality of preferably solid, substantially
non-flexible body portions (also referred to as bodies or beads)
and a series of flexible link portions (also referred to as links
or struts). The preferably solid, substantially non-flexible body
portions preferably are capable of withstanding loads that are
applied in any direction, and the flexible link portions of the
implant preferably are disposed between the substantially
non-flexible body portions and preferably are flexible in any
direction, although they may be flexible in only selected or
desired directions. The bodies may be substantially solid,
semi-solid or hollow and preferable of sufficient strength to
support the loads typical for the body location in which they are
implanted. The link portions may be solid, semi-solid, or hollow
and preferably of sufficient flexibility to allow the adjacent
bodies to touch one another upon bending of the elongate member or
chain. The material of both portions, the flexible link and
non-flexible body portions, preferably is the same and form one
single, flexible monolithic chain (FMC).
[0022] In one aspect of the invention, an apparatus for
augmentation of body tissue, for example bone, comprises a flexible
elongated member, or chain, having a longitudinal length
substantially larger than its height or its width. The flexible
elongated member comprises a plurality of substantially
non-flexible bodies and a plurality of substantially flexible links
interconnecting the bodies. The bodies and links are connected
end-to-end to form the elongated member, wherein the elongated
member is formed of a biocompatible material.
[0023] The bodies may be different sizes and shapes than the links
or they may be the same shape, same size, or both. In addition,
each body and link may be a different size and shape than other
bodies or links. In one embodiment, the beads can be shaped so that
they can fit together to minimize interstial spaces. For example,
the beads may be shaped as cubes or other polyhedrals that can be
stacked together in such a way that there is little space between
beads, or a predetermined percentage range of interstial space.
[0024] The elongated member may be formed as an integral monolithic
chain, which may be formed of bone, such as, for example, allograft
bone. The flexible links may be formed of bone that has been
demineralized to a greater extent than the bodies. Optionally, a
coating may be applied to at least a portion of the elongated
member, e.g. a coating comprising a therapeutic agent, a bone
cement, an antibiotic, a bone growth stimulating substance, bone
morphogenic protein (BMP) or any combination thereof. Therapeutic
agents, or drug agents (e.g., antibodies), or biologics (e.g., one
or more BMPs) can be coated, or attached via peptides, adsorbed,
sorbed or in some other way perfused onto or into the elongated
member; either the bodies, the links or both. In some embodiments,
the coating may comprise a bone cement that may be activated upon
insertion into the bone. In other embodiments, at least a portion
of the bodies comprise an outer surface configured to promote bone
in-growth.
[0025] In another aspect, a flexible chain implant may be impacted
or inserted into a cavity, void or hollow space, e.g., through a
small narrow opening. Such cavities may be, for example, voids in
long bones, intervertebral disc spaces or vertebral bodies. Such
voids may have occurred due to infections, disease, trauma
fractures, degenerative disc disease process, tumors or
osteotomies. In other embodiments, a void may be created by using a
tool to compact or remove cancellous or cortical bone or other
tissue prior to implantation. The chain may thereafter be implanted
to fill the created void. Depending on the insertion or impaction
force and depending on the amount or the length of chain devices
inserted, the device will fill and/or support the tissue structure,
preferably bone structure to a restored size and/or height. In an
alternative embodiment, no void or cavity may be present, and even
if a void or cavity is present the chain implant or elongated
member may be inserted and/or implanted in a manner to compact the
material and bone cells within the bone and to further fill the
bone in a manner that it can better support a load and preferably
fill the bone in a manner to restore its original and/or treated
size and height.
[0026] In another aspect, one or more flexible monolithic chains
may be implanted into diseased, damaged or otherwise abnormal bones
to treat, for example, long bone infections, comminuted complex
fractures, tumor resections and osteotomies. An FMC device may also
be used to treat disease or abnormal pathology conditions in spinal
applications, including, for example, degenerative disc disease,
collapsed intervertebral discs, vertebral body tumor or fractures,
and vertebral body resections. The elongated member or chain device
can be used as a preventive measure to augment a bone, spinal disc
or an implant, e.g., and intervertebral body implant to promote
fusion. The elongated member may be used within a vertebra or
between two vertebra. The elongated member or chain also may be
used for example in an intervertebral body fusion procedure, for
example, as an implant inserted into the disc space between two
vertebra, as an implant inserted into and retained by the disc
annulus, or in combination with an additional implant inserted in
the disc space between two vertebra.
[0027] In another embodiment, a kit comprises various combinations
of assemblies and components according to the present invention. A
kit may include, for example, a package or container comprising an
elongated member, for example an FMC device, and a cannula or other
introducer or device for implanting the elongated member. In other
embodiments, a kit may comprise instruments to create a cavity
(e.g., balloon catheter), an FMC device and a cement or other
filler material and/or a syringe or other apparatus for injecting a
FMC device and/or such filler material into a vertebral body.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The present invention can be better understood by reference
to the following drawings, wherein like references numerals
represent like elements. The drawings are merely exemplary to
illustrate certain features that may be used singularly or in
combination with other features and the present invention should
not be limited to the embodiments shown.
[0029] FIG. 1 is a side view of a portion of a spine with a
vertebral compression fracture.
[0030] FIG. 2A is a side view of a flexible monolithic chain
according to an embodiment of the present invention.
[0031] FIG. 2B is a close-up cross-sectional side view of the
flexible monolithic chain of FIG. 2A taken through line B-B.
[0032] FIGS. 3A-D is an illustration depicting a method of
fabricating a flexible monolithic chain.
[0033] FIGS. 4A-C are perspective views of other embodiments of a
flexible monolithic chain having flexible portions and non-flexible
portions with substantially uniform dimensions.
[0034] FIG. 5 is a perspective, cross-sectional view of another
embodiment of a flexible monolithic chain.
[0035] FIGS. 6A and B are side cross-sectional views of a flexible
monolithic chain being implanted within a fractured vertebral
body.
[0036] FIG. 7 is a cross-sectional top view of a flexible
monolithic chain implanted within a vertebral body.
[0037] FIG. 8A is a cross-sectional side view of a vertebra having
a flexible monolithic chain implanted within a vertebral body.
[0038] FIG. 8B is a cross-sectional side view of a vertebra having
an implanted flexible monolithic chain as in FIG. 8A, showing an
end of the chain extending from the vertebra.
[0039] FIG. 8C is a cross-sectional side view of a vertebra having
an implanted flexible monolithic chain as in FIG. 8A, and further
including a pedicle screw implant.
[0040] FIGS. 9A-D are top views depicting a minimally invasive
method for implanting a flexible monolithic chain within a
vertebral body.
[0041] FIG. 10A is a cross-sectional top view of another method of
implanting a flexible monolithic chain within a vertebral body.
[0042] FIG. 10B is a top view of a flexible monolithic chain that
may be used in the method of FIG. 10A.
[0043] FIG. 10C is a side view of another embodiment of a flexible
monolithic chain that may be used in the method of FIG. 10A.
[0044] FIG. 11A is a side view of a screw device for driving a
chain implant through an introducer.
[0045] FIG. 11B is an end view of a screw device for driving a
chain implant through an introducer.
[0046] FIG. 12 is a side view of a plunger device for driving a
chain implant through an introducer.
[0047] FIG. 13 is a side view of a sprocket device for driving a
chain implant through an introducer.
[0048] FIGS. 14A and B are cross-sectional side views of a flexible
monolithic chain implanted into the head of a femur.
[0049] FIG. 15 is a cross-sectional view of a chain implant
inserted through a cannula into the head of a femur.
DETAILED DESCRIPTION
[0050] Referring to FIG. 2, a chain 200 (sometimes referred to as
an elongated member) comprises one or more bodies 210 (sometimes
referred to as beads). Chain 200 is preferably a monolithic chain,
e.g., formed from a single, common material or type of material
forming an integral structure. Bodies 210 are preferably
substantially non-flexible, and may be solid, semi-solid, porous,
non-porous, hollow, or any combination thereof. Chain 200 may also
comprise one or more linking portions 220, also sometimes referred
to as struts or links 220. Struts 220 may be disposed between each
pair of adjacent bodies 210. Struts 220 are preferably
substantially flexible or semiflexible, e.g. to allow for bending
of the chain 200 between bodies 210.
[0051] Bodies 210 of chain 200 are preferably formed of bone, e.g.,
cortical bone, cancellous bone or both, but preferably cortical
bone. In other embodiments, chain 200 may be comprised of any
biocompatible material having desired characteristics, for example
a biocompatible polymer, metal, ceramic, composite or any
combination thereof. Bodies 210 may be absorbable or resorbable by
the body. For some applications, the bodies 210 preferably have
osteoinductive properties or are made at least partly from
osteoinductive materials. The outer circumferential shape of the
body may be the same as adjacent links. Alternatively or in
addition, the outer circumferential shape of the body may be the
same size as adjacent links. Bodies 210 may be of uniform or
non-uniform size, shape and/or materials, and may be linked in
series, for example by one or more flexible or semi-flexible
linking portions 220, which can form struts of any desired length
between bodies 210. Linking portions are preferably, although not
necessarily, formed of the same material as bodies 210.
[0052] A chain 200 may have any desired number of linked bodies
210, and may have a first end 202 and a second end 204. In other
embodiments, chain 200 may be formed in a loop, ring, or other
configuration having no ends, or may be configured to have multiple
extensions and/or multiple ends, for example like branches of a
tree.
[0053] The one or more linking portions 220 may be comprised of any
biocompatible material having desired characteristics of
flexibility, strength, and the like. In preferred embodiments,
linking portions 220 may be formed, at least in part, of
substantially the same material as bodies 210. In some embodiments,
chain 200, including bodies 210 and/or linking portions 220, may be
resorbable. The bodies 210 may be of uniform or non-uniform size,
and may be spaced by linking portions 220 at uniform or non-uniform
increments.
[0054] FIG. 2B is a close up cross-sectional view of chain 200,
taken at line B-B in FIG. 2A. In this example, chain 200 is a
monolithic chain, with bodies 210 and flexible portions 220 formed
from a uniform material, e.g., bone. Although bodies 210 are shown
as substantially spherical, and linking portions 220 are shown as
substantially cylindrical, numerous other shapes are contemplated.
In fact, chains 200, including body 210 and/or linking portion 220,
may be of any desired shape, such as for example, cylindrical,
elliptical, spherical, rectangular, etc. Body 210 and/or linking
portion 220 may also be of any particular cross sectional shape
such as round hexagonal, square, etc. Bodies 210 and linking
portions 220 may have the same or different shapes. In certain
embodiments the configurations of bodies 210 may vary within a
chain 200, for example as described herein with respect to FIGS. 5
and 10. Alternatively or in addition thereto, the configuration of
links 220 may vary within a chain. In one embodiment, the bodies
can be shaped so that they fit together to minimize interstitial
spacing or provide a predetermined range of interstitial
spacing.
[0055] All dimensional aspects of the chain 200 can be made to fit
any particular anatomy or delivery device. For example, for
applications of vertebral body augmentation, the diameter 230 of
bodies 210, e.g., as shown in FIG. 2B, may be between about 1 mm
and about 15 mm, preferably between about 2 mm and about 8 mm, or
more preferably between about 4 mm and about 6 mm. Preferably, the
non-flexible bodies 210 are larger in shape and size than the
flexible struts 220. For example, height 232 of struts 220 may be
between about 0.5 mm and about 8 mm, preferably between about 0.8
mm and about 4 mm, and may depend in part upon the size of bodies
210. Struts 220 may have any desired length 238, e.g., between
about 0.5 mm and about 5.0 mm, preferably between about 1.5 mm and
3.5 mm, or greater than 5 mm. Similarly, distance 234 between
bodies 210 may be any desired distance, e.g., depending upon the
size of bodies 210 and/or length 238 struts 220. In some
embodiments, for example, distance 234 may be between about 4 mm
and about 15 mm, or between about 6 mm and about 10 mm. The
junctions between bodies 210 and struts 220 may have a radius 236
of any desired dimension, e.g., less than 1.0 mm, between about 1.0
mm and about 2.0 mm, or greater than about 2.0 mm.
[0056] In some embodiments, each of the bodies 210 and struts 220
of a chain may be of the same configuration and/or dimensions as
other bodies 210 and struts within the chain 200. In other
embodiments, bodies 210 and/or struts 220 within a chain may have
different configurations or dimensions. In still other embodiments,
the non-flexible bodies 210 and flexible portions 220 may be of the
same shape and size to form a relatively uniform structure, for
example as shown in FIG. 4.
[0057] A chain 200 may be made as long as practical for a
particular application. For example, an exemplary chain 200 for
implantation into a bone may be about 100 mm in length. In other
embodiments, chain 200 may be of other lengths, for example less
than about 1 mm, between about 1 mm and about 100 mm, or greater
than 100 mm. In some embodiments, two or more chains 200 and/or
other implants may be used in combination with each other. Chain
200 may be connected end to end to form larger chains.
[0058] While the present invention is preferably directed to the
creation of implants from allograft material, the present invention
may also be applied to implants that utilize other materials,
including but not limited to the following: xenograft, autograft,
metals, alloys, ceramics, polymers, composites, and encapsulated
fluids or gels. Furthermore, the implants described herein may be
formed of materials with varying levels of porosity, such as by
combined bone sections from different bones or different types of
tissues and/or materials having varying levels of porosity.
[0059] Also, the implants described herein may be formed of bone
materials with varying mineral content. For example, cancellous or
cortical bone may be provided in natural, partially demineralized,
or demineralized states. Demineralization is typically achieved
with a variety of chemical processing techniques, including the use
of an acid such as hydrochloric acid, chelating agents,
electrolysis or other treatments. The demineralization treatment
removes the minerals contained in the natural bone, leaving
collagen fibers with bone growth factors including bone morphogenic
protein (BMP). Variation in the mechanical properties of bone
sections is obtainable through various amounts of demineralization.
Advantageously, use of a demineralizing agent on bone, e.g.,
cortical or cancellous bone, transforms the properties of the bone
from a stiff structure to a relatively pliable structure.
Optionally, the flexibility or pliability of demineralized bone may
be enhanced when the bone is hydrated. Any desired portions of bone
components, e.g., link portions 220 or any other desired portion,
may be demineralized or partially demineralized in order to achieve
a desired amount of malleability, elasticity, pliability or
flexibility, generally referred to herein as "flexibility". The
amount of flexibility can be varied by varying in part the amount
of demineralization.
[0060] In some embodiments, flexibility of demineralized or
partially demineralized regions may be further enhanced by varying
the moisture content of the implant or portions thereof. Bone
components initially may be provided with moisture content as
follows: (a) bone in the natural state fresh out of the donor
without freezing, (b) bone in the frozen state, typically at
-40.degree. C., with moisture content intact, (c) bone with
moisture removed such as freeze-dried bone, and (d) bone in the
hydrated state, such as when submersed in water. Using the
expansion and contraction properties that can be obtained during
heating and cooling of the bone material, and the concomitant
resorption of moisture along with swelling for some bone material,
permits alternate approaches to achieving a desired flexibility of
an implant within a bone or other region.
[0061] The implants may be formed entirely from cortical bone,
entirely from cancellous bone, or from a combination of cortical
and cancellous bone. While the implants may be created entirely
from all bone material, it is also anticipated that one or more
components or materials may be formed of non-bone material,
including synthetics or other materials. Thus, while the implants
disclosed herein are typically described as being formed primarily
from bone, the implants alternatively may be formed in whole or in
part from other materials such as stainless steel, titanium or
other metal, an alloy, hydroxyapatite, resorbable material,
polymer, or ceramic, and may additionally incorporate bone chips,
bone particulate, bone fibers, bone growth materials, and bone
cement. Also, while solid structures are described herein, the
structure optionally may include perforations or through bores
extending from one outer surface to another outer surface, or
recesses formed in outer surfaces that do not extend through inner
surfaces (surface porosity), or recesses formed internally. Surface
texture such as depressions and/or dimples may be formed on the
outer surface. The depressions and/or dimples may be circular,
diamond, rectangular, irregular or have other shapes.
[0062] The flexible monolithic chain devices described herein may
be used to treat disease and pathological conditions in general
orthopedic applications such as long bone infections, comminuted
complex fractures, tumor resections and osteotomies. Additionally
the device can be used to treat disease and pathological conditions
in spinal applications, such as, for example, degenerative disc
disease, collapsed intervertebral discs, vertebral body tumor or
fractures, vertebral body resections or generally unstable
vertebral bodies. In other embodiments, a flexible monolithic chain
device may be used in maxillofacial applications or in non-fusion
nucleus replacement procedures.
[0063] FIG. 3 shows an example of a method 300 for fabricating a
monolithic chain device 200 out of bone material 310. In this
example, allograft femoral bone 310 is used as a base material,
preferably, cortical allograft bone. Other bones may be used for
forming implants, for example, radius, humerous, tibia, femur,
fibula, ulna, ribs, pelvic, vertebrae or other bones.
[0064] As shown in FIG. 3A, an initial step comprises machining a
rough monolithic chain 200', having a desired general shape, out of
the raw material 310, preferably bone. For example, conventional
milling and/or other fabrication techniques may be used. Device
200, may have any desired shape, for example including generally
elliptical or spherical bodies 210 separated by cylindrical linking
portions 220 as shown. Alternatively, chain 200 may be formed of a
substantially uniform shape as shown, for example, in FIG. 4.
[0065] After machining the general desired shape in step A of FIG.
3, the rough monolithic device 200' may then be removed from the
raw material 310, as shown for example in step B. In this example,
an upper side 312 of the rough device 200' has been fabricated to
have a desired general shape as described above. An opposite side
314, however, may include excess material that was not removed in
step A.
[0066] In step C of the exemplary method of FIG. 3, opposite side
314 is machined to remove excess material, for example using
conventional milling methods. Side 312 may also be further machined
or shaped as desired, in order to form a monolithic chain device
200 having the desired shapes and configurations of bodies 210 and
linking portions 220.
[0067] In step D, the shaped chain 200, if formed of bone, may be
demineralized, e.g., in container 320 containing a demineralizing
solution 322 (e.g., hydrochloric acid) or using another method.
Demineralization may be allowed to occur for a specified amount of
time, for example to allow the smaller, lower volume portions 220
of the device 200 to become more flexible or elastic, while the
larger bodies 210 of the device remain structurally intact and
substantially rigid. The amount of time and/or the concentration or
composition of the demineralizing solution may be varied to provide
the desired amount of flexibility or elasticity.
[0068] In some embodiments, this secondary process of
demineralization can be applied to specific portions of the device
200, e.g., by masking or shielding the portions that do not or
should not be treated. For example, by masking the non flexible
portions 210, the flexible portions 220 can be partially or
entirely demineralized, and the non-flexible portions 210 may
retain their original mineralized state prior to the masking.
Alternatively, an allograft device may be submerged entirely into
demineralization acid without masking any portions of the device.
Due to the relatively smaller shape and size of the flexible
portions 220, including the surface area exposed to the
demineralized agent, and depending for example upon the amount of
exposure to the demineralization acid, the flexible portions 220
may demineralize entirely, or at least substantially more than the
larger portions 210, which may undergo only surface
demineralization. Therefore, the smaller portions 220 may become
flexible and elastic while the larger portions 210 may remain
relatively stiff and substantially non-flexible. For example, FIG.
2B shows regions 240 that are substantially demineralized and
regions 242 that have substantially their natural or original
composition and mineralization content.
[0069] The following Table 1 provides examples of demineralization
times of four monolithic chains having different strut
configurations. Each of the chains were formed of cortical
allograft bone and had body portions 210 that were approximately 5
mm in diameter. Configurations and dimensions of the struts 220
differed between the samples. In all four samples, the struts were
fully demineralized between about 31/2 and 4 hours, while the beads
were demineralized to an extent, but were not fully demineralized
across their entire thickness. Strut dimensions correspond to
distance 238 in FIG. 2B, while strut radius corresponds to radius
236 in FIG. 2B. Full flexibility is considered to be the condition
when the chain can be bent until two adjacent beads contact each
other without the chain cracking or breaking. While the foregoing
is one manner to measure sufficient flexibility, other measures of
flexibility are also contemplated and the invention should not be
limited by such measure of flexibility. For example, less than full
flexibility may be sufficient and desirable for insertion into
vertebrae to augment and support the vertebral end plates.
TABLE-US-00001 TABLE 1 Examples of demineralization times for 5 mm
diameter chains having different strut configurations. Strut
Dimensions Chain Demineral- (w .times. h .times. l, Strut Radius*
Length ization Sample in mm) (mm) (mm) Time** (min.) 1 1.5 .times.
1.5 .times. 3.2 -- 76 210 2 1.5 .times. 1.5 .times. 3.2 1.57 101
255 3 1.0 .times. 1.4 .times. 3.0 1.57 93.35 180 4 1.5 .times. 1.5
.times. 3.0 1.57 101 180 *Radius between body 210 and strut 220 on
top and bottom only **Time in hydrochloric acid 1N solution to
achieve foil flexibility
[0070] Table 2 below provides an example of approximate incremental
changes in flexibility of strut portions 220 of a sample, e.g.,
Sample 1 of Table 1, as a function of duration of exposure to the
hydrochloric acid bath. TABLE-US-00002 TABLE 2 Incremental changes
in flexibility of struts with exposure to acid bath. Exposure Time
Flexibility (min) (% of maximum) 0-5 0 5-10 0 10-15 10 15-20 15
20-30 25 30-45 35 45-90 50 90-140 70 140-200 85 200-240 100
[0071] Of course, other samples will attain different flexibility
in different exposure times depending upon a host of factors,
including concentration of acid bath, chain dimensions,
temperature, original bone sample mineralization and condition,
etc.
[0072] Various other configurations and methods for manufacturing
monolithic or other chain implants may be used. The choice of
methods may depend, at least in part, on the material or materials
to be used in the particular chain device 200. If the device is
made of a biocompatible polymeric material, the device can be
manufactured by using conventional manufacturing methods such as
but not limited to milling and turning. Alternatively, if the chain
device 200 is made out of a biocompatible polymeric material, the
entire device can also be injection molded.
[0073] If the chain 200 is made of a metallic material, it can be
manufactured by using conventional manufacturing methods such as
but not limited to milling and turning. However, the flexible
components may undergo secondary processes such as annealing. The
secondary process can be limited to the flexible portions of the
device only, for example by masking or shielding the non-flexible
portions.
[0074] In some embodiments, a chain implant 200 can be formed of
any type of biocompatible material that will allow for sufficient
flexibility in areas of reduced material sections (e.g., relatively
narrow and flexible portions 220), while having larger sections
(e.g., bodies 210) that are substantially rigid and allow for load
bearing characteristics. The reduced material portions 220 may be
flexible, pliable, or have elastic properties in all directions
preferably without fracturing or breaking. Alternatively, the
reduced material portions 210 may allow for fracture during device
200 insertion, or at another stage in a method, to allow for proper
void filling. Materials may be metallic and include but are not
limited to titanium and steels. Polymeric and alternatively
allograft tissue materials can be used. Instead of or in addition
to bone device 200 may comprise one or more other materials, e.g.,
a metal (titanium, a steel, or other metal), an alloy, or a
polymer. In some embodiments, the material of the device 200 may
have osteoconductive, osteoinductive, and/or osteogenic properties.
In other embodiments, the implant device 200 may be made out of
non-monolithic materials.
[0075] Referring to FIGS. 4A-C, a chain 200 may have any desired
geometric configuration. For example, rigid portions 210 and
flexible portions 220 may have the same or different shapes, such
as cubes, cylinders, any polyhedral shapes, balls, banana or kidney
shaped, or any combination thereof. Portions 210 and/or 220 may
have any desired cross-sectional shape, such as for example
rectangular, circular, elliptical, pentagonal, hexagonal, etc. The
flexible 220 and non-flexible 210 portions may be of the same shape
to form relatively uniform shaped structures as shown in FIGS.
4A-C.
[0076] As shown in FIG. 5, one or more bodies 210 may have cavities
510 or central holes 512. Such holes 512 or cavities 510 may be
empty or may be filled, for example with a cement, bone filler,
adhesive, graft material, therapeutic agent, or any other desired
materials. The filling material may incorporate radiopaque agents
so that the chain, or bodies can be visualized during and after a
procedure. In other embodiments, an implant device 200 may be
coated with different substances that will support and promote bone
healing, reduce infections and/or deliver therapeutic agents to the
treated site. For example, the device 200 or portions thereof may
be coated with antibiotics, BMP, bone growth enhancing agents,
porous or non-porous bone ingrowth agents, therapeutic agents, etc.
The implant may be coated with a material that may incorporate a
radiopaque agent so that the implant may be visualized during or
after implantation. In addition, therapeutic agents, drug agents,
BMPs, tissue growth enhancing agents, osteoinductive agents may be
absorbed, sorbed or other wise perfused onto or into some portion
of the chain implant. Additionally, the solid, non-flexible
portions 210 may have cavities, axial or side holes or a
combination thereof that can be filled with different substances or
agents.
[0077] As shown in FIGS. 6A and 6B, a minimally invasive method 600
of augmenting a damaged vertebral body 12, e.g., following a
vertebral compression fracture, may comprise implanting one or more
chains 200 into an inner portion 612 of a vertebral body 12 between
endplates 614 and 616. Of course, one or more chains 200 may be
implanted as a preventive measure to augment a vertebra before
compression or a compression fracture. A hole may be formed in the
outer coritcal shell of vertebral body 12 by a trocar, drill or
other instrument. Chain 200 may then be implanted, for example,
through a cannula 602 or other introducer inserted into vertebral
body 12. Suitable procedures and materials for inserting a cannula
through which chain 200 may be introduced are known in the art, and
may be similar to those described above for kyphoplasty and other
procedures. For example, cannula 602 may be introduced through the
posterior portion 16 of vertebral body 12, e.g., through pedicle 14
(e.g., transpedicular approach). A chain 200 may be inserted and
may compact the cancellous and osteoporotic bone inside the
vertebral body.
[0078] Prior to insertion of the cannula, a passageway may be
formed into the interior of the vertebral body, for example using a
drill or other instrument. The chain 200 may then be inserted
through the passageway, and may compact or compress the bone
material inside the vertebral body. Alternatively, after the
passageway is formed in the vertebral body, instruments such as,
for example, currettes or balloon catheter may be used to compress
and compact the bone inside the vertebral body to create a cavity.
The instruments may then be removed. Alternatively, the balloon
portion of the catheter may remain within the vertebral body or may
form a container for the implant. The cavity in the vertebral body
also may be formed by removing bone material as opposed to
compacting the bone. For example, a reamer or other apparatus could
be used to remove bone material from the inside of the vertebral
body.
[0079] Whether a cavity is first formed in the bone structure or
the chain(s) are inserted without first creating a cavity, as more
linked bodies 210 of chain 200 are inserted into vertebral body 12,
they may fill central portion 612 and provide structural support to
stabilize a vertebral body. In a vertebra that has collapsed, as
the chain implant 200 fills central portion 612 the implant, and
particularly the linked bodies 210, can push against the interior
or inner sides of endplates 614 and 616, thereby tending to restore
vertebral body 12 from a collapsed height h1 to its original or
desired treated height h2 and provide structural support to
stabilize vertebral body 12. Instead of using the insertion of the
chain implant to restore the height of the vertebra, an instrument
can be inserted through the passageway to restore the height of the
vertebra and plates. For example, a balloon catheter can be
inserted to restore vertebra end plates, or an elongated instrument
that contacts the inside of the end plates and pushes on them may
be utilized. Additionally, the flexibility of one or more portions
220 between bodies 210 may allow bending of chain within space 612,
e.g., in a uniform pattern or in a non-uniform or tortuous
configuration, to aid in ensuring a thorough integration of the
implant 200 within the bone 12. The configuration of bodies 210
attached by flexible portions also may permit bending to
substantially fill the cavity and/or vertebral bone so no large
pockets or voids are created or remain which may result in weak
spots or a weakened bone structure. The flexible links may also
allow the chain to collapse and possibly become entangled so that
it becomes larger than its insertion hole so that it cannon be
easily ejected.
[0080] In other embodiments, chain 200 may be inserted into a bone
such as a vertebral body 12, e.g., through the lumen 604 of a
cannula 602 or other sheath, and such sheath may be removed after
implantation within the bone 12. In such embodiments, chain 200, or
a portion thereof, may remain in vertebral body 12, for example, to
continue augmenting the vertebra and maintain proper lordosis. In
other embodiments, PMMA or another bone cement or filler (for
example bone chips) may be inserted sequentially or simultaneously
into vertebral body 12, e.g., through shaft and/or a cannula 602,
along with bodies 210 to further enhance fixation or repair of the
damaged region. Alternatively, only a plug of bone cement may be
inserted into the hole that was initially formed to insert chains
200 (e.g., plug 812 of FIG. 8A). The plug may cover the insertion
hole to prevent the implant (chains) from being removed or ejected.
In other embodiments, some or all of bodies 210 of chain 200 may be
removed after repositioning the bone, and PMMA or another bone
cement or filler may be injected into a void created by chain 200.
Alternatively a bone growth promoting filler may be inserted into
vertebral body 12 and a plug of bone cement utilized to hold the
linked bodies and filler material in the vertebrae.
[0081] In some embodiments, flexible chain 200 may be coated with
an adhesive, such that chain 200 may be inserted into vertebral
body 12 in a flexible state and may become tangled and/or
convoluted during or after insertion. After insertion, bodies 210
may become attached together by the adhesive so that the flexible
chain becomes a mass that may be locked into the vertebral body, or
otherwise secured such that chain 200 may not be easily removed
through the insertion opening.
[0082] In other embodiments, linked bodies 210 may be coated with
an adhesive and chain may be inserted, with or without becoming
tangled or convoluted, into a vertebral body. During or after
insertion of some or all linking bodies 210 of a chain 200, a
portion of chain 200 may be exposed to an energy source (e.g., an
ultraviolet light, ultrasonic radiation, radio waves, heat,
electric filed, magnetic field), for example to activate the
adhesive, such that the exposed portion of chain 200 becomes joined
to form a mass, or becomes rigid, or both, thereby further
augmenting the vertebral body 12 and/or preventing removal or
ejection of chain 200 through the insertion opening.
[0083] FIG. 7 is a top cross-sectional view illustration of a
vertebral body 12 having one or more chains 200 implanted within
portion 612 of vertebral body 12. The one or more chains 200 may
comprise a plurality of bodies 210, which may be joined in series
by one or more linking portions as described above. One or more
cannulae 602, each for example having a lumen 604 of sufficient
size for passing linked bodies 210, can be used to implant chain
200 into vertebral body. The one or more cannulae 602 may be
inserted into vertebral body 12, preferably through pedicles 14. In
some embodiments, the one or more cannulae 602 may be left within
vertebral body 12, and remain extending from pedicles 14, for
example held in place by sutures (not shown).
[0084] In some embodiments, chains 200 may be implanted completely
within vertebral body 12 as shown in FIG. 8A, and the cannulae or
other introducer may be removed. The chains may remain entirely
within the interior of the bone. A passageway 810 through which
chains 200 were inserted may be filled with a plug 812, e.g., a
bone cement plug. Alternatively, as shown in FIG. 8B, an end 204 of
chain 200 may be left extending through the insertion hole of the
bone, for example through the pedicle 14 of vertebra 12. In other
embodiments, as shown in FIG. 8C, other implants or apparatus, such
as for example a bone screw 800, may be inserted into vertebral
body 12 in conjunction with chain implant 200 to further augment
vertebral body 12. The extended end 204 or additional implant 800
may be used, for example, as an anchoring element for imparting an
eternal force on vertebra to reposition the vertebra 12. Screw 800
may be inserted into the opening used to insert the chains, and may
further serve as a plug to prevent removal or ejection of the
chains. Screw 800 may be hollow or solid, and may be comprised of
stainless steel, a metal alloy, a ceramic, polymer, composite or
any other desired material. In some embodiments, screw 800 may be
hollow, e.g., including a lumen such as lumen 604 of cannula 602,
and used as an introducer to create a passage for passing chain 200
into vertebral body 12. A bone cement or other material may be
injected into vertebral body 12 to further secure implants 200
and/or 800 and augment vertebral body 12. The bone cement or other
material may be inserted through the cannulation of the screw.
[0085] FIGS. 9A-D show another example of a flexible monolithic
chain device being implanted into vertebral body. In FIG. 9A, after
a chain device 200 is unpacked, e.g., from a sterile package or
container, it may be placed into an introducer or delivery device
910 that aids in insertion and/or impaction of the chain 200 to a
desired cavity, void, space or interior of a bone. In this example,
delivery device 910 has an elongated cannula-like shaft 912 having
a lumen through which chain 200 may pass. Device may have a funnel
914 or other structure to facilitate loading of the chain 200
and/or for holding a portion of the chain 200 prior to
implantation. An insertion end 916 of the insertion device 910 may
have a tip 918, which may be blunt, pointed, tapered or otherwise
configured as desired to facilitate insertion of end 916 into a
bone or other structure.
[0086] FIG. 9B shows end 916 of insertion device 910 being inserted
through pedicle 14 of vertebra 12, such that tip 918 enters
interior portion 612 of the vertebral body. An access hole may be
formed in the outer cortical shell of the vertebral body by a
trocar, drill or other instrument to provide a passage through
which introducer 910 device may be inserted. After insertion of end
916 of delivery device 910 into the desired region, e.g., into a
vertebral body 12, preferably through a pedicle, chain 200 may be
inserted.
[0087] FIG. 9C shows first end 202 of a chain 200 being inserted
through the introducer 910 into space 612 of vertebral body 12.
Chain 200 may be forced into vertebral body 12, for example by
manually applying an axial force from opposite end 204 of chain 200
to drive chain 200 through introducer 910. In other embodiments, a
displacement member, sprocket, screw mechanism, or other device is
used to apply an axial force for implanting chain 200, for example
as described below with respect to FIGS. 11-13. In some
embodiments, one long flexible monolithic device 200 may be
inserted and impacted into the surgical site. Alternatively,
multiple shorter or different chain devices 200 and/or other
implants can be impacted or otherwise inserted into the desired
cavity, void or space. The multiple shorter chain devices may be
attached to each other sequentially end to end as they are
inserted. In this manner as one chain is almost inserted, and with
an end extending out of the patient, the leading end of the next
chain is attached to the chain that is partially inserted. FIG. 9D
shows the one or more chains 200 completely inserted into the
central portion 612 of vertebral body 12.
[0088] Other suitable procedures and materials for inserting a
cannula through which an FMC may be introduced are described, for
example, in U.S. Provisional Patent Application No. 60/722,064,
filed Sep. 28, 2005 entitled "Apparatus and Methods for Vertebral
Augmentation using Linked Bodies", which is incorporated by
reference herein in its entirety. A chain or other implant 200 may
compact the cancellous and/or osteoporotic bone inside a collapsed
vertebral body during insertion into the vertebral body.
Alternatively, a tool such as, for example, currettes or balloon
catheter may be used to compress and compact the bone inside the
vertebral body to create a cavity. The cavity in the vertebral body
also may be formed by removing bone material as opposed to
compacting the bone. For example, a reamer or other apparatus could
be used to remove bone material from the inside of the vertebral
body.
[0089] In other embodiments, PMMA or another bone cement or filler
(for example bone chips or material collected from reaming the
bone) may be inserted into vertebral body 12, e.g., through the
introducer 910 or another cannula, sheath, syringe or other
introducer, simultaneously with implant 200 to further enhance
fixation or repair of a damaged region. Alternatively, the PMMA,
bone cement or filler may be inserted into the interior of the bone
after the chains (or portions thereof) have been inserted into the
interior of the bone. Alternatively a bone growth promoting filler
may be inserted into the vertebral body, and a plug of bone cement
may be utilized to hold the implant 200 and filler material in the
vertebrae 12. In this manner, the plug of cement is not inserted
into the interior of the bone, but covers the opening created in
the bone to insert the implant.
[0090] A minimally invasive system for fusion or non-fusion
implants and insertion instruments is shown in FIGS. 10A-C. As
described above, a flexible monolithic chain device 1000 device may
be inserted into a vertebral body 12, e.g., through a cannula 1030
or other introducer inserted through a pedicle 14 as shown in FIG.
10A. Optionally, a guide or other tool 1032 having a curved or
otherwise configured tip 1034 may also be inserted through the
cannula 1030 and serve to distract the end plates of the vertebral
body 12 and/or guide the bodies 1010 of chain 1000 in a desired
direction. As chain 1000 is forced into vertebral body 12, flexible
portions 1020 of chain 1000 may bend or flex to allow chain 1000 to
curve or otherwise convolute in a desired fashion to fill the
central portion 612. The flexible portions allow the implant to
fold and collapse upon itself to substantially fill the interior of
the bone preferably with minimal porosity or open spaces.
[0091] As shown in FIG. 10B, chain 1000 may have flexible portions,
or struts, 1020 and non-flexible portions 1010 of different shapes.
For example, flexible joints 1010 may be narrower than the
non-flexible portions 1020, which may be kidney shaped,
rectangular, or any other shape. Some of the non-flexible bodies
may be a different size or shape than others, for example they may
increase in size from a first non-flexible body 1010-1having a
width Y.sub.1 to a last non-flexible body 1010-5 having a width
Y.sub.2 that is larger than width Y.sub.1. For example, in the
exemplary embodiment of FIG. 10B, width Y1 may be between about 5
mm and about 2 mm or less, and width Y2 may be between about 6 mm
and about 8 mm or less. Similarly, body 1010-1 may have a length
X.sub.1 that is substantially shorter than the length X.sub.2 of
body 1010-5. For example, in the exemplary embodiment of FIG. 10B,
length X.sub.1 may be between about 2 mm and about 6 mm, and length
X.sub.2 may be between about 6 mm and about 14 mm. Overall length
of chain 1000 may vary depending upon the desired application, for
example from about 10 mm to about 150 mm, more preferably from
about 40 mm to about 100 mm. Of course various other sizes and
relative differences in size or configuration of width,
circumference, shape, curvature, or other dimensions of bodies 1010
and/or flexible portions 1020 may be employed without departing
from the scope of the present invention.
[0092] In some embodiments, one or more of the bodies 1010 may have
one or more openings or cavities 1012 or 1014. Such openings or
cavities 1012, 1014 may be empty or may be filled, for example with
a cement, bone filler, adhesive, graft material, therapeutic agent,
or any other desired materials. In other embodiments, an implant
device 1000 may be coated with different substances that will
support and promote bone healing, reduce infections and/or deliver
therapeutic agents to the treated site. Additionally, the
non-flexible or flexible portions may also have porous surfaces
1016, for example to facilitate in growth of bone or other
tissues.
[0093] FIG. 10C shows another embodiment of a chain 1050 having
substantially rectangular or cylindrical bodies 1010-1, 1010-2,
1010-3, 1010-4 and 1010-5, which may be separated by flexible link
portions 1020, and may have the same or different dimensions as
each other. In FIG. 10C all of the bodies 1010-1, 1010-2, 1010-3,
1010-4 and 1010-5 have the same height h but different lengths. The
struts 1020 in FIG. 10C have a different smaller height than the
bodies 1010.
[0094] FIG. 11 is a side view illustration of an insertion device
1100 for implanting a chain 200 into a bone or other desired
structure. For example, insertion device 110 may include an
insertion tube or cannula 1120 having a wall 1122 and a lumen 1223.
Disposed within and extending through at least a portion of lumen
1223 is a rotatable screw mechanism 1110 having spiral threads 1114
surrounding an axial shaft 1112. Threads 1114 preferably extend
from shaft and are dimensioned and spaced to engage chain 200,
e.g., between bodies 210. When screw 1110 is rotated, e.g., by
turning a handle 1130, the threads 1114 engage bodies 210 and force
chain 200 axially through the lumen 1223 of the cannula and into
the desired bone or other region. Such an insertion device may
allow for enhanced insertion force of an implant, for example in
order to move vertebral endplates to restore the height of the end
plates of a vertebra, to compress cancellous bone in a region of
the implant, or to otherwise force the implant into a desired
area.
[0095] FIGS. 12 and 13 show other mechanisms for forcing a chain
200 through an introducer and into a desired region. In particular,
FIG. 12 shows a plunger, pusher or other displacement member 1200
inserted within cannula 1102. Displacement member 1200 may be used
to displace or push bodies 210 of chain through cannula 1102 and
into vertebral body 12. Displacement member 1200 may be driven, for
example, by pressure, e.g., from a syringe, rod, or other apparatus
that forces displacement member 1200 into cannula 1102 and towards
vertebral body 12. In the embodiment of FIG. 13, a sprocket 1300 or
apparatus that may be wheel-like and have teeth, gears or other
extensions 1302 may be configured to engage bodies 210 of chain
200. Sprocket 1300 rotates about a central axis 1304, for example
in a direction shown by arrow 1306, teeth 1302 may engage bodies
210 and force chain 200 through cannula 1102 and into portion 612
of vertebral body 12. In other embodiments, sprocket 1300 may be
rotated in an opposite direction to remove some or all of chain
200, for example after restoring a height of vertebral body 12.
[0096] The flexible monolithic chain devices and/or methods
described herein may be used in conjunction with or instead of
other methods or devices for augmenting vertebral bodies or other
bones, such as, for example are described in U.S. Provisional
Patent Application No. 60/722,064, filed Sep. 28, 2005 entitled
"Apparatus and Methods for Vertebral Augmentation using Linked
Bodies", which is incorporated by reference herein in its
entirety.
[0097] Although the apparatus and methods described herein thus far
have been described in the context of repositioning and augmenting
vertebrae for example in the context of vertebral compression
fractures and deformations in spinal curvature, various other uses
and methods are envisioned. For example, in some embodiments, an
implantable monolithic chain 200 may be used to augment vertebrae
where a compression or a compression fracture has not yet occurred
and thus can be preventative in nature. Also, in some embodiments
the chain can be used in-between two vertebra. For example, the
chain implant can be inserted in the annulus of a spinal disc, or
the disc can be removed and the chain implant inserted in-between
adjacent vertebra to promote fusion of adjacent vertebrae. The
chain implant in some embodiments may be insertable in an
additional implant, such as a cage implanted in-between adjacent
vertebrae. The chain implant may also be used to reposition and/or
augment other damaged bone regions such as a fractured or weakened
proximal femur 1400 as shown in FIG. 14. In such embodiments, for
example, one or more chains 200 may be inserted into a head 1410 of
femur 1400, e.g., through a cannula 1102 or other introducer as
show in FIG. 15. Once inserted, chain 200 may compact material
within head 1410 and provide solid support to augment the head
1410. A bone cement or other filler may also be used to aid
augmentation. In other embodiments, another implant 1420 may be
inserted in addition to or instead of one or more chains 200.
[0098] In some embodiments, the implants and methods described
herein may be used in conjunction with other apparatus and methods
to restore lordosis and augment the vertebral body. For example,
one or more chains 200 may be used in conjunction with known
procedures, e.g., a balloon kyphoplasty, that may be used to begin
repositioning of a vertebral body and/or create a space within the
body for chain 200. In other embodiments, one or more chains 200
may be used in conjunction with other tools or external fixation
apparatus for helping to manipulate or fix the vertebrae or other
bones in a desired position.
[0099] In another embodiment, a kit comprises various combinations
of assemblies and components. A kit may include, for example, a
cannula or other introducer and one or more flexible monolithic
chains 200. The one or more chains 200 may be provided in different
sizes, e.g., different lengths and/or diameters. In other
embodiments, a kit may include an introducer, one or more chains,
and a syringe or other apparatus for injecting a cement or other
filler into a vertebral body or other space. In other embodiments,
a kit may comprise one or more balloon catheters, curettes, and
other instruments and may additionally include anchoring elements,
tensioning members, fixation members, or any combination thereof,
for example as described in U.S. Provisional Patent Application No.
60/722,064, entitled "Apparatus and Method for Vertebral
Augmentation using Linked Bodies", filed Sep. 28, 2005, which is
incorporated by reference herein in its entirety. One skilled in
the art will appreciate that various other combinations of devices,
components and assemblies can be made and are intended to fall
within the scope of the present invention.
[0100] In other embodiments, various minimally invasive implants
and methods for alleviating discomfort associated with the spinal
column may employ anchors and other implants described herein. For
example, a monolithic chain implant within an expandable container
(not shown), may be implanted between spinous processes of adjacent
vertebrae to distract the processes and alleviate pain and other
problems caused for example by spinal stenosis, facet arthropathy,
and the like. For example, augmentation systems described herein
may be used instead of or in addition to expandable interspinous
process apparatus and methods described in U.S. Patent Publication
number 2004/018128 and U.S. Pat. No. 6,419,676 to Zucherman et al.
For example, a cannula may be inserted laterally between adjacent
spinous processes to insert a container that may be filled with the
flexible chains and expand the container and thus keep the adjacent
spinous processes at the desired distance. Alternatively, a balloon
container, with a deflatable balloon portion can be inserted
laterally through adjacent spinous processes and filled with the
flexible chains to expand the balloon to a desired size to hold
adjacent spinous processes at a desired distances. The balloon can
thereafter be sealed and detached from the catheter. Other
materials may be inserted within the balloon volume to supplement
flexible bodies.
[0101] While the foregoing description and drawings represent the
preferred embodiments of the present invention, it will be
understood that various additions, modifications and substitutions
may be made therein without departing from the spirit and scope of
the present invention as defined in the accompanying claims. In
particular, it will be clear to those skilled in the art that the
present invention may be embodied in other specific forms,
structures, arrangements, proportions, and with other elements,
materials, and components, without departing from the spirit or
essential characteristics thereof. The presently disclosed
embodiments are therefore to be considered in all respects as
illustrative and not restrictive, the scope of the invention being
indicated by the appended claims, and not limited to the foregoing
description.
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