U.S. patent application number 10/866219 was filed with the patent office on 2005-12-15 for method and apparatus for filling a cavity.
Invention is credited to Zwirkoski, Paul A..
Application Number | 20050278023 10/866219 |
Document ID | / |
Family ID | 35461526 |
Filed Date | 2005-12-15 |
United States Patent
Application |
20050278023 |
Kind Code |
A1 |
Zwirkoski, Paul A. |
December 15, 2005 |
Method and apparatus for filling a cavity
Abstract
An implant for filling and/or distracting a body region,
particularly a non-soft tissue cavity, has a plurality of segments
wherein at least two of the segments are flexibly connected. The
segments have a crush-strength sufficient to create and/or maintain
the distraction of two or more non-soft tissue body surfaces, and
to maintain the stability of the body region. The implant may be
inserted into a cavity by an applicator having a cannula with a
distal opening, and a rotary driver for applying force to move the
implant within the cannula.
Inventors: |
Zwirkoski, Paul A.;
(Pinckney, MI) |
Correspondence
Address: |
MORRISON & FOERSTER LLP
755 PAGE MILL RD
PALO ALTO
CA
94304-1018
US
|
Family ID: |
35461526 |
Appl. No.: |
10/866219 |
Filed: |
June 10, 2004 |
Current U.S.
Class: |
623/11.11 |
Current CPC
Class: |
A61F 2/46 20130101; A61F
2002/444 20130101; A61F 2/4425 20130101; A61B 17/8635 20130101;
A61F 2002/30331 20130101; A61F 2002/30663 20130101; A61F 2002/2835
20130101; A61F 2002/30462 20130101; A61F 2/30749 20130101; A61F
2/442 20130101; A61F 2002/302 20130101; A61F 2002/443 20130101;
A61B 17/686 20130101; A61F 2/4611 20130101; A61F 2002/30495
20130101; A61B 17/7097 20130101; A61B 17/8863 20130101; A61F
2002/30604 20130101; A61F 2002/30383 20130101; A61B 17/7094
20130101; A61F 2002/30662 20130101; A61F 2002/4415 20130101 |
Class at
Publication: |
623/011.11 |
International
Class: |
A61F 002/02 |
Claims
What is claimed as new and desired to be protected by Letters
Patent of the United States is:
1. A segmented implant for introduction into a body region that is
at least partially surrounded by non-soft body tissue, comprising a
plurality of implant segments, wherein at least two of the
plurality of implant segments are flexibly connected and wherein at
least a portion of the segments provide implant segment
distractibility to the body region and form stability to a body
region into which the segments have been introduced.
2. The segmented implant of claim 1 wherein at least a portion of
the implant segments are configured to be introduced into the body
region by engaging a rotating introducer member.
3. The segmented implant of claim 1 wherein at least a portion of
the flexibly connected implant segments are configured to be
introducible into the body region by engaging a rotating introducer
member.
4. The segmented implant of claim 1 wherein at least a portion of
the segments are comprised of one or more materials having
sufficient material strength to provide implant segment
distractibility to the body region.
5. The segmented implant of claim 4 wherein the material strength
is crush strength.
6. The segmented implant of claim 1 wherein at least a portion of
the segments have one or more shapes and are comprised of one or
more materials having material strength and the one or more shapes
cooperate with the material strength of the materials to provide
implant segment distractibility to the body region.
7. The segmented implant of claim 6 wherein the material strength
is crush strength.
8. The segmented implant of claim 1 wherein at least a portion of
the segments have one or more shapes and are comprised of one or
more materials having material strength and the one or more shapes
cooperate with the material strength of the materials to provide
form stability to a body region into which the segments have been
introduced.
9. The segmented implant of claim 8 wherein the material strength
is crush strength.
10. The segmented implant of claim 1 wherein more than two of the
plurality of implant segments are flexibly connected.
11. The segmented implant of claim 1 wherein the majority of
implant segments are flexibly connected.
12. The segmented implant of claim 1 wherein the implant segments
are configured to provide distractibility and form stability to a
body region comprising a bone cavity.
13. The segmented implant of claim 1 wherein the implant segments
are configured to provide distractibility and form stability to a
body region comprising a void between tissue surfaces.
14. The segmented implant of claim 1 wherein the implant segments
comprise pellets.
15. The segmented implant of claim 1 wherein the at least two of
the plurality of implant segments that are flexibly connected are
connected by a filament.
16. The segmented implant of claim 1 wherein the at least two of
the plurality of implant segments that are flexibly connected are
connected by a fiber.
17. The segmented implant of claim 1 wherein the at least two of
the plurality of implant segments that are flexibly connected are
within a flexible tube.
18. The segmented implant of claim 1 wherein the at least two of
the plurality of implant segments that are flexibly connected are
within a flexible tube comprised of a woven material.
19. The segmented implant of claim 1 further comprising a settable
fluent material.
20. The segmented implant of claim 19 wherein the fluent material
is a bone cement.
21. The segmented implant of claim 1 wherein at least a portion of
the implant segments comprise shapes configured to cooperate in
enhancing segment packing.
22. The segmented implant of claim 1 wherein at least a portion of
the implant segments are different sizes than at least one other
implant segment of the plurality of implant segments.
23. The segmented implant of claim 1 wherein at least some of the
segments are movably connected along an axis of the implant.
24. The segmented implant of claim 1 wherein the implant segments
are selectively severable.
25. The segmented implant of claim 24 wherein the implant segments
are remotely severable by a user.
26. The segmented implant of claim 24 wherein the implant segments
are mechanically severable.
27. The segmented implant of claim 24 wherein the implant segments
are chemically severable.
28. The segmented implant of claim 24 wherein the implant segments
are thermally severable.
29. The segmented implant of claim 24 wherein the implant segments
are electrically severable.
30. The segmented implant of claim 1 wherein said at least one of
the segments comprises a radiopaque material.
31. The segmented implant of claim 1 wherein at least some of the
segments comprise a biodegradable material.
32. The segmented implant of claim 1 wherein at least some of the
segments comprise a material that is not substantially
biodegradable.
33. The segmented implant of claim 1 wherein at least some of the
segments comprise a polymer.
34. The segmented implant of claim 1 wherein at least some of the
segments comprise a metal.
35. The segmented implant of claim 1 wherein at least some of the
segments comprise a composite material.
36. The segmented implant of claim 1 wherein at least one of the
segments comprise a medicinal.
37. The segmented implant of claim 1 wherein at least some of the
segments comprise a coating.
38. The segmented implant of claim 37 wherein the coating is a
medicinal coating.
39. The segmented implant of claim 37 wherein the coating is a
cross-linker.
40. An implant assemblage for filling a non-soft tissue cavity
comprising: an implant comprising a plurality of flexibly connected
segments configured for insertion into a bone cavity; wherein said
segments have a crush strength sufficient to maintain the
distraction of two or more bone surfaces and further wherein said
implant assemblage is configured to maintain a shape within the
cavity.
41. An applicator for inserting an implant into a tissue cavity
comprising: a cannula having a distal end and proximal end and a
distal opening and a proximal opening; a feed guide connected to
the proximal end of said cannula so that the proximal opening of
said cannula is in fluid connection with said feed guide; and a
driver at least partially within said feed guide for applying force
to at least one portion of an implant wherein said force is applied
by rotating at least a region of said driver in contact with the
implant.
42. The applicator of claim 41 wherein said tissue cavity is a
non-soft tissue cavity.
43. The applicator of claim 41 further comprising a force gauge
configured to detect the force applied by said driver.
44. The applicator of claim 43 further comprising a display
configured to show the force detected by said force gauge.
45. The applicator of claim 41 further comprising a trocar located
at the distal end of said cannula.
46. The applicator of claim 41 further comprising a fluent material
source configured to connect to said cannula for delivering a
fluent material.
47. The applicator of claim 41 wherein said implant comprises one
or more loose pellets.
48. The applicator of claim 41 further comprising a gripper located
distally on the cannula.
49. The applicator of claim 41 wherein said implant is a segmented
implant comprising a plurality of flexibly connected segments.
50. The applicator of claim 49 further comprising a cutter
configured to sever a connection between at least two of said
flexibly connected segments.
51. The applicator of claim 50 wherein said cutter is a mechanical
cutter.
52. The applicator of claim 51 further comprising an actuator for
activating said cutter by a user.
53. The applicator of claim 41 wherein said driver comprises a
rotatable auger.
54. The applicator of claim 53 wherein said auger is located at
least partially in said cannula.
55. The applicator of claim 41 wherein said driver comprises at
least one cog.
56. The applicator of claim 41 further comprising a controller for
controlling said driver.
57. The applicator of claim 56 wherein said controller is
configured to control the force applied by said driver.
58. The applicator of claim 56 wherein said controller is
configured to control the direction of rotation of said driver so
as to allow both insertion and removal of said implant.
59. The applicator of claim 56 wherein said controller is manually
controlled.
60. The applicator of claim 41 wherein said feed guide comprises a
cartridge pre-loaded with said implant.
61. The applicator of claim 41 wherein said distal opening of said
cannula is at least partly on a side perpendicular to the long axis
of said cannula.
62. The applicator of claim 41 wherein said distal opening of said
cannula opens at an angle perpendicular to the long axis of said
cannula.
63. An applicator for inserting and removing an implant into a
tissue cavity comprising: a cannula having a distal end and
proximal end and a distal opening and a proximal opening; a driver
at least partially within said cannula for applying force to at
least one portion of an implant wherein said force is applied by
rotating at least a region of said driver in contact with the
implant.
64. An applicator for inserting and removing a bone filler into a
bone cavity comprising: a cannula having a distal end and proximal
end and a distal opening and a proximal opening; and a rotatable
auger configured to fit at least partly into said cannula to propel
a bone filling material out of said distal end of said cannula.
65. An applicator for inserting and removing a bone filler into a
bone cavity comprising: a cannula having a distal end and proximal
end and a distal opening and a proximal opening; and a rotatable
cog configured to fit at least partly into said cannula to propel a
bone filling material out of said distal end of said cannula.
66. A method of distracting a non-soft tissue cavity comprising:
providing an implant for filling a non-soft tissue cavity
comprising a plurality of flexibly connected segments wherein said
segments have a crush strength capable of distraction of two or
more tissue surfaces; inserting the flexibly connected segments
into the cavity.
67. The method of claim 66 wherein the implant segments are
inserted into the cavity by applying force to at least one segment
of the implant.
68. The method of claim 67 further comprising measuring the applied
force.
69. The method of claim 66 wherein said non-soft tissue cavity is a
bone cavity.
70. The method of claim 69 wherein the bone cavity is a fractured
vertebral body.
71. The method of claim 70 further comprising inserting the
segmented implant into the fractured vertebral body until the
normal height of the vertebra is substantially attained.
72. The method of claim 71 further comprising severing the implant
behind the last segment inserted.
73. The method of claim 69 further comprising the step of providing
fluent bone filler within the bone cavity.
74. The method of claim 66 wherein the implant segments are
inserted into the cavity through a cannula.
75. The method of claim 66 wherein the implant segments are
inserted into the tissue cavity using an auger.
76. The method of claim 69 further comprising providing a
closure.
77. The method of claim 76 wherein the closure is a screw
closure.
78. The method of claim 76 further comprising closing the cavity
using the closure.
79. The method of claim 66 further comprising compacting the
flexibly connected pellets.
80. A method of distracting a bone cavity comprising: providing a
segmented implant comprising a plurality of flexibly connected
segments wherein said segments have a crush strength sufficient to
maintain the distraction of two or more bone surfaces; inserting
one or more implant segments into the bone cavity.
81. A method of filling a tissue cavity comprising: providing an
implant for filling a cavity; providing an applicator for
introducing the implant into the cavity, wherein the applicator
comprises a cannula configured to pass at least a region of the
implant, and a rotary driver at least partially within said
cannula; and introducing the implant into the cavity by rotating
the driver.
82. A method of filling a tissue cavity comprising: providing an
implant for filling a tissue cavity comprising a plurality of
flexibly connected segments; providing an applicator for
introducing the implant into the cavity, wherein the applicator
comprises a cannula configured to pass at least a region of the
implant, and a rotary driver at least partially within said
cannula; and inserting the implant into the cavity by rotating the
driver.
83. A method of filling a non-soft tissue cavity comprising:
providing an implant for filling a tissue cavity comprising a
plurality of flexibly connected segments; providing an applicator
for introducing the implant into the cavity, wherein the applicator
comprises a cannula configured to pass at least a region of the
implant, and a rotary driver at least partially within said
cannula; and inserting the implant into the cavity by rotating the
driver; providing a closure configured to close the cavity; and
closing the cavity with the closure.
84. A kit for filling a non-soft tissue cavity comprising: a
segmented implant comprising a plurality of segments wherein at
least two of the segments are flexibly connected; and an applicator
configured for inserting a segmented implant into cavity wherein
the applicator comprises a cannula configured to pass at least a
region of the implant, and a rotary driver at least partially
within said cannula configured to apply force to at least a region
of the implant.
85. The kit of claim 84 further comprising a fluent material.
86. The kit of claim 84 further comprising a feed guide.
87. The kit of claim 84 further comprising a gauge.
88. The kit of claim 87 wherein the gauge is a force gauge.
89. The kit of claim 84 further comprising a display.
90. The kit of claim 84 further comprising a closure.
91. The kit of claim 84 further comprising a compaction device.
92. A segmented implant for introduction into a body region that is
at least partially surrounded by non-soft body tissue, comprising a
plurality of implant segments, wherein at least two of the
plurality of implant segments are flexibly connected wherein the
segments have a shape, size, and spacing with respect to other
segments; and wherein at least a portion of the segments provide
form stability to a body region into which the segments have been
introduced.
93. The segmented implant of claim 92 wherein at least one segment
is a substantially cubic shape with rounded edges.
94. The segmented implant of claim 92 wherein at least one segment
has two or more faces.
95. The segmented implant of claim 92 wherein a plurality of the
segments can interlock with other segments.
96. The segmented implant of claim 92 wherein at least one segment
is configured to engage non-adjacent segments.
97. The segmented implant of claim 92 wherein at least one segment
is a substantially solid shape.
98. The segmented implant of claim 92 wherein at least one segment
is a substantially hollow shape.
99. The segmented implant of claim 92 wherein at least one segment
is configured to have passages therethrough.
100. The segmented implant of claim 92 wherein at least one segment
is a substantially different shape than at least one other
segment.
101. The segmented implant of claim 100 wherein the different
segment shapes are located adjacent to each other in a repeating
pattern.
102. The segmented implant of claim 92 wherein at least one segment
is a different size than at least one other segment.
103. The segmented implant of claim 102 wherein segments of
different sizes are arranged adjacent to each other in a repeating
pattern.
104. The segmented implant of claim 92 wherein at least one segment
has a polygonal cross-section.
105. The segmented implant of claim 104 wherein at least one
segment has a triangular cross-section.
106. The segmented implant of claim 104 wherein at least one
segment has a rectangular cross-section.
107. The segmented implant of claim 92 wherein the distance between
at least two adjacent segments is different than the distance
between other adjacent segments.
108. The segmented implant of claim 92 wherein at least one segment
is substantially slideable with respect to adjacent segments.
Description
FIELD
[0001] Described here are non-soft tissue cavity implants, implant
applicators, delivery devices, and methods for using them. In
particular, the description relates to implants having a plurality
of flexibly connected segments having a strength sufficient to
support, to fill, to create, to maintain, or to distract a bone
cavity such as might be found in a fractured vertebral body, and
methods and devices for inserting implants into non-soft tissue
cavities such as bone cavities.
BACKGROUND
[0002] Proper treatment of orthopedic conditions such as trauma,
fractures, non-unions, tumors, cysts, and certain fusion procedures
may involve filling a cavity that has been created by the pathology
itself or by the action of a surgeon. Often the cavities are
compressed, and require that the surfaces of the cavity be
distracted from one another and then supported to return the bone
structure to its anatomic position and form. Furthermore, because
non-soft tissues such as bone have a structural and support role in
the body, it is critical that such cavities be repaired to allow
reliable strength and support.
[0003] Compression fractures are one type of hard tissue injuries
belonging to a class of conditions that may be treated using
devices and methods for separating, distracting, and supporting a
fractured bone. For example, vertebral compression fractures are
crushing injuries to one or more vertebra. A vertebral compression
injury may be the result of a trauma to the spine, an underlying
medical condition, or a combination of a trauma and an underlying
condition. Osteoporosis and metastatic cancers are common medical
conditions that also contribute to vertebral compression fractures
because they weaken spinal bone, predisposing it to compressive
injury.
[0004] Osteoporosis is a degenerative disease that reduces bone
density, and makes bone more prone to fractures such as compression
fractures. An osteoporosis-weakened bone can collapse during even
normal activity. According to the National Institute of Health,
vertebral compression fractures are the most common type of
osteoporotic fractures.
[0005] Vertebral fractures may be painful and may deform the shape
of the spine, resulting in unhealthy pressure on other parts of the
body, loss of height, and changes in the body's center of gravity.
Untreated, such changes and the resulting discomfort can become
permanent, since the bone heals without expanding the
compression.
[0006] Existing methods of treating bone injuries such as
compression fractures and bone voids may involve highly invasive or
inadequate treatments. For example, one method of treatment is
percutaneous vertebroplasty. Vertebroplasty involves injecting bone
filler (such as bone cement) into the collapsed vertebra to
stabilize and strengthen the crushed bone. In vertebroplasty,
physicians typically insert a small diameter guide wire or needle
along the pedicle path intended for the bone filler delivery
needle. The guide wire is advanced into the vertebral body under
fluoroscopic guidance to the delivery point within the vertebrae.
The access channel into the vertebra may be enlarged to accommodate
the delivery tube. In some cases, the delivery tube is placed
directly into a vertebral body and forms its own opening. In other
cases, an access cannula is placed over the guide wire and advanced
into the vertebral body. In both cases, a hollow needle or similar
tube is placed into the vertebral body and used to deliver the bone
filler into the vertebra.
[0007] When filling a bone cavity with bone filler using
traditional vertebroplasty, fillers with lower viscosities may
leak. Further, even fillers having low viscosities may require the
application of a high pressure to disperse the bone filler
throughout the vertebral body. However, application of high
pressure also increases the risk of bone filler extravasation from
the vertebral body. Conversely, injecting a bone filler having a
higher viscosity may provide an even greater risk of "leaking" bone
filler into sensitive adjacent body areas. Leaks or extrusion of
the bone filler may be dangerous to a patient's health. For
example, posterior extravasation from a vertebral body may cause
spinal cord trauma, perhaps resulting in paralysis. Risk of leakage
is even more acute when a bone filler is applied under pressure to
expand a compression fracture, especially if the fracture has begun
healing and requires substantial force to distract the cavity
surfaces.
[0008] Furthermore, most bone cements and bone fillers are
difficult to remove or to adjust. Removal and adjustment may be
important when distracting a bone cavity. For example, removing a
precise amount of bone filler may allow a surgeon to adjust the
level of distraction of a vertebral compression fracture and
correct the shape of the compressed bone. Many bone cements, once
set, are difficult or impossible to remove without further, highly
invasive, surgery. Even if the removal is attempted prior to the
expiration of the setting time, the materials may have
non-Newtonian flow characteristics requiring a substantial removal
vacuum to achieve an initial and sudden movement.
[0009] The implant could be utilized in any area of non-soft tissue
where the filling of a cavity with stability and control is
desired, for example, intervetebral disc repair, hip, tibia, and
other areas of bone displacement.
[0010] In addition to traditional bone cements, a handful of other
bone cavity filling materials have been suggested. In particular,
biodegradable and/or bioabsorbable bone-filling devices have been
suggested. For example, U.S. Pat. No. 5,756,127 to Grisoni et al.
describes a bioresorbable string of calcium sulfate hemihydrate
(Plaster of Paris) beads and a means for producing these beads.
However, the Grisoni device is not intended for distracting a
non-soft tissue cavity, and has many disadvantages. Calcium sulfate
hemihydrate (Plaster of Paris) and similar materials have low crush
strength, making them unreliable as materials to distract and later
support a bone cavity, particularly during the early stages of the
healing process. Filling materials that are readily compressed or
crushed, may shift within, or exit the bone cavity altogether,
leading to detrimental changes in the shape of the corrected bone.
Materials with low crush strength (particularly those materials
having crush strengths less than that of normal bone) are poor
choices in withstanding the stress of distracting the bone
surfaces, and may be unable to maintain the distracted shape of the
bone after filling a bone cavity. Similar materials are the
subjects of U.S. Pat. No. 6,579,533 to Tormala et al.
[0011] U.S. Pat. No. 5,702,454 to Baumgartner describes an implant
made of an elastic plastic for implanting into an intervertebral
disk. Because the Baumgartner implant is elastic, it may be less
effective for filling and distracting body cavities benefiting from
implants having some stiffness, such as non-soft tissue cavities.
This is particularly true where sustained distraction is
desired.
[0012] U.S. Pat. No. 6,595,998 to Johnson et al. describes a tissue
distraction device in which wafers are inserted to distract a
tissue cavity by forming a wafer stack within the cavity. However,
Johnson's column of wafers is not amenable to providing uniform
support to all surfaces of a bone cavity, when such support is
needed. For example, a tissue cavity supported or distracted on all
sides of the cavity may be more stable.
[0013] U.S. Pat. No. 5,958,465 to Klemm et al. describes a method
and apparatus for making a drug containing implants in the form of
a string of beads comprising chains of small drug-containing
plastic bodies arranged in series on a surgical wire or thread.
Similar drug implanted beads-on-a-string are described in U.S. Pat.
No. 6,183,768 to Harle and German Patents 2320373 to Klemm and
2651441 to Heusser. The Klemm, Harle, and Heusser implants are
designed for drug delivery, and are embedded with one or more drugs
which are released from the plastic (e.g. PMMA) beads (also called
"corpuscles"). Thus, these implants may be limited in strength and
durability because of the inclusion of a releasable drug, as well
as the properties and shape of the implant beads.
[0014] In any event, none of the cited documents show the device
and methods disclosed below.
BRIEF SUMMARY
[0015] Broadly, described here are segmented implants for filling a
non-soft tissue cavity, applicators for inserting implants, and
methods of using the segmented implants and applicators to fill
and/or distract tissue cavities. In particular, the implants
described here may be used for filling and/or distracting non-soft
tissue cavities such as a bone cavity. Generally, the segmented
implants described here comprise a plurality of segments, where at
least two of the segments are flexibly connected, and configured
for insertion into a body region. The segments provide implant
segment distractibility to the body region, and stability to the
body region into which they are introduced. In some variations of
the implant described herein, the segments have sufficient material
strength to distract two or more non-soft tissue surfaces. In some
versions, the material strength is crush strength, so that the
segments of an implant have sufficient crush strength to allow and
sustain the distraction of non-soft tissue surfaces. Thus, the
implant is inserted into a cavity to distract, to expand, to
reduce, or to support the cavity, typically filling the cavity and
maintaining a desired shape.
[0016] At least a portion of the segments of the implant may be
configured so that the implant may be introduced into a body region
by engaging a rotating introducer member. For example, a rotatable
driver may be used to introduce the segments of the implant into a
body region using an applicator as described herein. In some
versions, the segments are configured as pellets.
[0017] The implant may also include a fluent material (such as bone
cement). Thus, for example, the fluent material may be added to a
bone cavity that has been distracted by the flexibly connected
segments of the implant. The segments may also include a channel or
channels to facilitate the passage of a fluent material, for
example a bone cement that may eventually harden.
[0018] Two or more of the implant segments may be connected in any
way allowing sufficient flexibility so that the implant may be
introduced into body region such as a bone hollow. The implant
segments may include a connection material for connecting segments
of the implant. Connection material may comprise, for instance, a
string, fiber or wire, variously of single or multiple strands. The
connecting string, fiber or wire may be flexible to allow the
segments to be inserted into the chosen treatment site. Suitable
examples of fibers include those used as suture materials,
biodegradable or not, e.g., polylactic acids, polyglycolic acids,
mixtures and copolymers of polylactic and polyglycolic acids (PGLA
such as "Vicryl" from Ethicon and "Dexon" from Davis & Geck),
polydioxanone, various Nylons, polypropylene, silk, etc.). In this
variation, the segments may comprise pellets with openings for
stringing or be made adherent to a string, fiber or wire by means
of manufacturing, glue, adhesive, or the like, or by simply placing
the glue between the pellets. The wires may comprise one or more
filaments comprising suitably biocompatible metals or alloys, e.g.,
stainless steels or superelastic alloys.
[0019] The segments may be connected by placement within a flexible
tube, variously a solid or continuous walled tube, a solid or
continuous walled tube having openings in the wall, or a netting
woven from string or fiber. The flexible tube may comprise one or
more membranes, optionally an expandable or a stretchable material.
Suitable materials include polymers, (e.g., polyfluorocarbons such
as the various Teflons (including PTFE and expanded PTFE--ePTFE
such as is sold as GORETEX), polypropylene, polyethylene,
polyoxymethylene, polycarbonate, polyesters (including polyamides
such as the Nylons), polyphenylene oxide, and polyurethane) or
elastomeric polymers (e.g. various Silicones, natural rubber,
butadiene-styrene rubber, carboxylic butadiene-styrene,
butadiene-acrylonitrile rubber, carboxylic butadiene-acrylonitrile
rubber, chlorobutadiene rubber, polybutadiene rubber, silicone
rubbers, and acrylate rubbers, perhaps vulcanized, and other
elastomeric materials) or a composite material. The expandable
membrane may optionally be filled, for example with a fluent
material or a bone cement, before or after the implant has been
inserted into the bone cavity. The flexible tube may comprise a
woven or non-woven material of non-synthetic materials (e.g.
cotton, silk, and the like), polymers such as those listed above,
and blends or mixtures of the previously mentioned materials. The
segments may also be connected by a string, fiber, or wire in
addition to the flexible tube.
[0020] The segments may be connected by adhesives or glues, such as
solvent- or catalyst-curable materials including silicone glues,
rubbery epoxies, and adhesives suitable for the materials forming
the segments.
[0021] The segments of the implant may be severable, singly or in
groups, such as by severing the connection between the segments.
The implant may be severed remotely by a user. The implant may be
severed mechanically, chemically, thermally, or electrically. The
implant may be severed while inserting it into a non-soft tissue
cavity or after the implant has been inserted into a cavity. In one
version, the connection material connecting flexibly connected
segments may be removed from one or more segments without severing
the material. For example, when a flexible joining material
connecting the segments is a fiber, the fiber may be removed from
the flexibly connected segments (e.g. pellets) after they have been
inserted.
[0022] The implant may include segments that are movably connected
along the axis of the implant. The segments may be slideably
positioned within a flexible tube. The segments may be slidably
connected on one or more stings, fibers, or wires. Some of the
segments may be held in a fixed location while others are movable
along the axis of the implant.
[0023] The implant may include segments of different sizes. The
implant may include segments of different shapes, such as
substantially spherical, substantially cubic, faceted or shaped to
facilitate space packing within a cavity, or of random shapes. The
segments may be cooperatively shaped to interlock or to
interconnect to other nearby segments.
[0024] The implant may comprise coated segments. The segments may
have a medicinal coating. The segments may include pellets with a
coating that allows them to crosslink with each other. The segments
may be porous or solid. The segments may be imbedded or infused
with any compound, for example a therapeutic or medicinal compound
so long as the segments provide distractability and stability to
the body region into which they are inserted, e.g. a bone
cavity.
[0025] In some variations of the implant, the segments have a crush
strength sufficient to maintain the distraction of two or more
surfaces of a bone cavity. In such variation, the segments comprise
a material selected to have a minimum adequate crush strength. In
any case, the segments may comprise one or more polymers, one or
more metals or alloys, and one or more inorganic materials such as
ceramics and inorganic oxides and phosphates. The segments may
comprise a variety of composite materials, e.g., layered, mixed,
etc. The segment materials may comprise either or both of
biodegradable and non-biodegradable materials. The implant may
include segments of different compositions. In one version, at
least one of the segments includes a radiopaque material to help in
visualizing the implant assembly (e.g., during insertion).
[0026] Also described herein are implants for filling hard tissue
cavities having a plurality of connected segments wherein at least
two of the segments are flexibly connected. The segments are
configured for insertion and packing into a hard tissue cavity and
have a material strength allowing them to distract two or more of
the hard tissue surfaces. In one version, the material strength is
compressive strength. In one version, the segments have a
compressive strength of greater than about 20 MPa. In one version,
the segments of the implant assemblage have a compressive strength
less than cortical bone. In one version, the segments of the
implant assemblage have a compressive strength of between about 20
MPa and about 160 MPa. In one version, the segments of the implant
have a compressive strength of between about 100 and 160 MPa.
[0027] In one version, an implant assemblage for filling a non-soft
tissue cavity comprises an implant including a plurality of
flexibly connected segments configured for insertion into a bone
cavity. The implant segments have a crush strength sufficient to
maintain the distraction of two or more bone surfaces and also to
maintain a selected shape within the cavity. In one version, the
implant segments have a sufficient crush strength to maintain the
distraction and/or shape of a non-soft tissue cavity over time.
Thus, the implant may be used to stabilize a body region after
filling and/or distracting. In one version, the implant is intended
for long-term use in a body region (e.g. hard tissue cavity).
[0028] Also described herein are applicators for introducing or
inserting an implant into a tissue cavity comprising a cannula with
a distal end that can be inserted into the cavity. A region at or
near the distal end of the cannula is open to allow the passage of
an implant into the cavity. The applicator can connect to a feed
guide at the proximal end of the cannula so that an implant (for
example, an implant comprising a plurality of flexibly connected
segments) may be moved within the cannula from the feed guide using
a rotating driver to apply force to at least one region of the
implant (e.g. one region of an implant segment). The rotary driver
may be located at least partly in the feed guide. The rotary driver
may be located at least partly in the cannula.
[0029] Implants compatible with this applicator include particles,
fluent material, pellets, and particularly linear arrays of
material (e.g. a segmented implant). In one version, the implant
applied by the applicator is the segmented implant assembly
described herein. In one version, an implant compatible with the
applicator is a loose pellet or segment. In one version, an implant
compatible with the applicator is a quantum of any solid material
desired to be packed into a tissue cavity.
[0030] The applicator may also include a force gauge configured to
indicate the force applied by the driver to move the implant. In
one version, the applicator includes a display. The display may
indicate force applied, volume (cc) inserted, amount of implant
inserted, and/or amount of implant material remaining in the
applicator, for example.
[0031] The applicator may also include a trocar at the distal end
of the cannula. The application may also include a gripper at the
distal end of the cannula for gripping the bone, therefore
resisting `back out` once the implant material (e.g. implant
segments) pack and exhibit resisting force to implant material
advancement. The gripper may be engageable by a user.
[0032] The applicator may also include a switch-able gripper to
resist implant material motion in either direction per user choice.
The applicator may also include a cutter for cutting the implant,
particularly when using the applicator with implants having
severable segment connections, thereby severing the connection
between the connected segments. The cutter may be a mechanical
cutter, an electrical cutter, a chemical cutter or a thermal
cutter. The cutter may be activated by an actuator controllable by
a user.
[0033] The driver of the applicator may include any driver which
actuates movement of the implant (or a part of the implant) by
rotating a region of the driver that contacts at least a region of
the implant. In one version, the rotating driver of the applicator
includes an auger. For example, an applicator can insert or remove
a segmented implant assembly by engaging at least one region of a
segment of the implant. Rotating the auger one direction drives the
implant forward (towards the distal end of the cannula), while
rotating the auger in the opposite direction drives the implant
backwards (towards the proximal end of the cannula). The auger may
be at least partly located in the cannula of the applicator.
[0034] The applicator driver may comprise a cog configured to
engage an implant. Rotating the cog one direction drives an implant
forward (towards the distal end of the cannula), while rotating the
cog in the opposite direction urges the implant back towards the
proximal end of the cannula (removing them from the tissue cavity).
In one version, the cog is a friction wheel.
[0035] The applicator may also include a controller for controlling
the driver. The controller may be configured to activate the
driver. The controller may be configured to determine the direction
of force applied by the driver (in the distal or proximal direction
down the cannula). Applying force down the cannula in the distal
direction moves an implant out of the distal end of the cannula
(e.g. inserting an implant into a bone cavity); applying force down
the cannula in the proximal direction moves an implant in the
proximal direction (e.g., withdrawing an implant from a non-soft
tissue cavity). The controller may also be configured to determine
the amount of force applied by the driver. The controller may be
configured to be manually operated by a user.
[0036] The feed guide of the implant may include a cartridge
pre-loaded with an implant. The driver may engage the distal-most
portion of an implant (e.g. a segment) of the preloaded implant and
apply force to drive the implant distally down the cannula. The
driver may also be configured to apply force in the proximal
direction to withdraw the implant.
[0037] The applicator's distal cannula opening may be located on
the distal end. The distal opening of the cannula may be located
more proximally than the distal tip of the cannula to aid in
inserting an implant in a cavity. In one version the distal opening
of the cannula is located on an angle from the distal tip of the
cannula. The distal opening of the cannula may be located on a side
perpendicular to the long axis of the cannula.
[0038] Methods of distracting a non-soft tissue cavity (including a
bone cavity) are described. A method of distracting a non-soft
tissue cavity includes providing an implant for filling a bone
cavity comprising a plurality of flexibly connected segments, where
the segments have a crush strength sufficient to maintain the
distraction of two or more tissue cavity surfaces. The method of
distracting a non-soft tissue cavity further includes inserting the
flexibly connected segments into the bone cavity.
[0039] Methods of filling a tissue cavity are described. A method
of filling a tissue cavity includes providing an implant for
filling a cavity, and providing an applicator for introducing the
implant into the cavity. The applicator includes a cannula
configured to pass at least a region of the implant, and a rotary
driver at least partly within the cannula. The method further
includes inserting the flexibly connected segments into the bone
cavity. The methods of filling and/or distracting a bone cavity may
also include using a rotating auger to drive the implant into the
bone cavity.
[0040] The method of filling and/or distracting a non-soft tissue
cavity may also include applying force to the implant to insert the
implant within the bone cavity. The method of filling or
distracting a bone cavity may also include measuring the force
applied.
[0041] The method of filling and/or distracting a non-soft tissue
cavity may also include removing the implant once a void is created
within a non-soft tissue and/or a desired elevation or expansion of
a cavity has been achieved.
[0042] The method of filling and/or distracting a non-soft tissue
cavity may be performed where the bone cavity is a fractured
vertebral body. This method may further include inserting the
implant into the bone cavity until the normal height or shape of
the vertebral body is substantially attained.
[0043] The method of filling and/or distracting a non-soft tissue
cavity may include providing a fluent filler (e.g. a bone cement)
within the cavity. In one version, the non-soft tissue cavity is a
hard tissue cavity. In one version the non-soft tissue cavity is a
bone cavity.
[0044] The method of filling and/or distracting a non-soft tissue
cavity may also include providing a closure. Suitable closures
include, but are not limited to, screw-type closures, particularly
screw-closures. Suitable closures may also have a compaction
enhancer, such as a spring element, to aid compaction and/or
securing of the implant. The method of filling and/or distracting a
non-soft tissue cavity may also include closing the soft-tissue
cavity with a closure.
[0045] Also described herein are kits for filling a hard tissue
cavity including an implant and an applicator. Implants appropriate
for the kit include implant assemblages comprising a plurality of
segments wherein at least two of the segments are flexibly
connected and the implant segments are capable of distracting and
providing stability to a non-soft tissue body region. Applicators
appropriate for the kit comprise a cannula configured to pass at
least a region of the implant and a rotary driver at last partly
within the cannula configured to apply force to at least a region
of the implant. The kits may also include fluent material (e.g.
bone cement), one or more gauges (e.g. force gauge), and/or a
display configured to show the status of the implant insertion. The
display might show the force applied to an implant, the length of
the implant inserted, the volume filled, etc. The kits may also
include compaction tools, e.g., vibrational probes, tamps, etc.
Kits may also include closures, e.g., screws, compaction screws,
etc.
BRIEF DESCRIPTION OF THE DRAWINGS
[0046] Embodiments or variations are now described by way of
example with reference to the accompanying drawings.
[0047] FIGS. 1A to 1E show variations of the described implant;
[0048] FIGS. 2A to 2F show variations of the described implant;
[0049] FIGS. 3A to 3E, 3G, 31 to 3T show variations of the
described implant;
[0050] FIGS. 3F, 3H, 3W and 3X illustrate variations of
interlocking segments of the described implant;
[0051] FIGS. 4A to 4D show variations of the described implant;
[0052] FIG. 5 illustrates a variation of an applicator for the
implant;
[0053] FIGS. 6A to 6C illustrate variations of the distal cannula
tip of an applicator;
[0054] FIGS. 7A and 7B show one variation of an applicator
driver;
[0055] FIG. 7C shows another variation of an applicator driver;
[0056] FIG. 7D shows the relationship between an applicator and
variations of the driver;
[0057] FIGS. 8A to 8C show insertion of an implant into a vertebral
body;
[0058] FIGS. 9A and 9B show a screw closure compatible with the
implants and applicators described herein. FIG. 9B is a schematic
cross-section of the screw closure shown in FIG. 9A taken along the
longitudinal plane A-A.
[0059] FIG. 10 shows a cutter for cutting segments of the implant
as described herein.
DETAILED DESCRIPTION
[0060] In the drawings, reference numeral 10 generally denotes an
exemplary embodiment of a segmented implant for distracting,
filling, creating, or maintaining a cavity in a non-soft tissue.
The implant, applicator, and methods of use may be used for
distracting, supporting, filling, creating and maintaining the size
of virtually any non-soft tissue cavity, particularly hard tissue
cavities, including but not limited to: bone separations, fractures
(including compression fractures), non-unions, removed tumors,
removed cysts, in conjunction with joint replacement implants, and
certain fusion procedures. Although example of implants, implant
applicators, combinations of implants and applicators and methods
of using the implants are described in the context of treating a
vertebral compression fracture, the devices and methods of use
described are not intended to be limited to vertebral compression
fractures.
[0061] The implants, applicators and methods described herein are
particularly relevant to insertion into body regions such as
non-soft tissue cavities. Non-soft tissue cavities include hard
tissues cavities such as cavities or voids such as bones, as well
as cartilage, and bone connected to ligament and/or muscle, scar
tissues, and other mineralized (e.g. calcified) tissues. Non-soft
tissue cavities also include tissues cavities having at least one
hard surface, including tissues having mixed compositions. For
example, non-soft tissue cavities include cavities abutting bone,
or cavities surrounded by bone, such as cavities within the spinal
disk space, cavities within the bone marrow, and cavities adjacent
to bone or bone and ligament.
[0062] FIGS. 1A to 1E illustrate variations of implants for
distracting or filling a tissue cavity. The implant 10 in each of
FIGS. 1A to 1E includes a plurality of segments (illustrated as
pellets) that are flexibly joined. Segments of the segmented
implants may include one or more pellets. A perspective view of an
implant is shown in FIG. 1A. The segments 12 are shown as spherical
pellets that are connected by a centrally located wire, string, or
fiber 16. The joined pellets form a connected construct seen as a
flexible linear array that may be inserted into a cavity to
distract the cavity walls, to fill the cavity, or to provide
continuing support to the cavity. As used herein, unless the
context makes clear otherwise, "distract" or "distracting" refers
to the process of separating (or enlarging) the walls of a cavity,
particularly a bone cavity.
[0063] Crush Strength
[0064] An implant may be used to distract, to fill, to create or to
maintain the size or shape of a hard tissue body cavity such as a
bone cavity. In one version, the described implant's segments 12
have crush strength adequate to withstand the forces required to
distract and support the cavity without substantial compression or
breaking of the segments. Crush strength is defined as average
crush load per unit cross-sectional area at which the structure
will break or crack, and may be expressed in pounds per square inch
or megaPascals (MPa). Of course, the shape of a segment has both
individual and group effects upon the crush strength of the implant
after installation. The crush strength of an individual segment
pellet, however, is a consideration for distracting a cavity. For
roughly spherical pellets, force can be approximated as acting at
discrete points on the surface of the sphere, so crush force may be
approximated as the total force applied to crack the sphere. One
factor effecting crush strength is compressible strength of the
material.
[0065] Compressibility
[0066] It may be beneficial that the segments comprise any solid
material having an appropriate compressible strength so that the
implant assemblage is able to distract, fill and support a tissue
cavity without substantially deforming. The segments preferably
comprise biocompatible solids with high compressive strength.
Compressibility and incompressibility generally describe the
ability of molecules in a solid to be compacted or compressed (made
more dense) under an applied force and/or their ability to return
to their original density after removing the applied force.
Compressibility of a solid may also be quantified by the bulk
modulus of the substance (bulk modulus is the inverse of
compressibility, and is the change in volume of a solid substance
as the pressure on it is changed). A relatively incompressible
material will have a higher bulk modulus than a more compressible
material.
[0067] The compressive strength of cortical bone is approximately
166 MPa, and the compressive strength of cancellous (spongy) bone
is approximately 4 MPa. In one version, the implant should have a
compressive strength of greater than approximately 20 MPa. In one
version, the implant should have a compressive strength less than
cortical bone. In one version, the implant has a compressive
strength between about 20 and about 160 MPa. In one version, the
implant has a compressive strength between about 91 and about 160
MPa. In one version, the implant has a compressive strength between
about 100 and about 160 MPa. As a reference, the compressive
strength of calcium sulfate is approximately 11 MPa.
[0068] Segment Materials
[0069] The crush strength of the implant depends to a large extent,
on the segment crush strength, which is a function of the
composition, and to a lesser degree, the shape of the segment.
[0070] Materials with appropriate crush strength include, but are
not limited to, metals, alloys, ceramics, certain inorganic oxides
and phosphates, polymers, bone derived material, and combinations
of these materials. The following descriptions of segment materials
represent versions of the implant, and are not intended to limit
the scope of the implant or segment materials. The implant segment
may comprise, consist of, or consist essentially of the materials
identified herein.
[0071] Bioabsorbable (or bioerodible) and non-bioabsorbable (or
non-bioerodible) material may be used in the implant separately or
in combination. Typically, the non-absorbable (or non-bioerodible)
materials noted elsewhere provide segments and implants exhibiting
a sustainable crush strength adequate to maintain the distraction
of the cavity surfaces (e.g. bone cavity surfaces) over a long
period of time. On the other hand, bioabsorbable (or bioerodible)
segments exhibit a reduction in crush strength over time, as the
material is acted upon by the body. However, bioabsorbable
materials may also permit substantial tissue in-growth, allowing
tissue to replace implant material while maintaining the
distraction and supporting the filled cavity. In applications in
which the likelihood of tissue re-growth is small, for example
osteoporotic repair, a nonabsorbable implant may be desirable.
Materials that are too rapidly bioabsorbed (for example, calcium
sulfate hemihydrate) are generally inappropriate as segment
materials, because they do not maintain the cavity structure and/or
distraction.
[0072] Metals that may be used as segment materials include, but
are not limited to, biocompatible metals and alloys, such as
stainless steels, gold, silver, tantalum, cobalt chromium,
titanium, platinum, rhodium, rhenium, ruthenium, and other alloys
thereof, combinations thereof, or other equivalent materials.
[0073] Ceramic materials that may be used in the segments may
include, but are not limited to, alumina, carbon or tricalcium
phosphate or sintered masses or single crystals of hydroxyapatite.
Ceramics capable of high crush strengths may be particularly
relevant. Also useful are refractory metal and semi-metal oxides
(tantalum oxides, aluminum oxides), phosphates (calcium
phosphates), phosphides, borides (niobium borides, tungsten
borides), carbides (aluminum carbides, boron carbides, niobium
carbides, silicon carbides, tantalum carbides, titanium carbides,
tungsten carbides, vanadium carbides, zirconium carbides), nitrides
(boron nitrides, chromium nitrides, silicon nitrides, tantalum
nitrides, titanium nitrides, zirconium nitrides), silicides
(tantalum silicides, tungsten silicides, zirconium silicides),
their mixtures, variously sintered as porous particulates or as
solid formations.
[0074] Inorganic materials that may be used as segment materials
include, but are not limited to, hardened glasses including oxides
of silicon, sodium, calcium and phosphorous and combinations
thereof.
[0075] Polymers that may be used as segment materials include, but
are not limited to, elastomers (natural and synthetic rubbers,
silicone rubbers), polymethyl methacrylate (PMMA),
polyetheretherketone (PEEK), polymethymethacrylate (PMMA),
polyglycolic acid and/or polylactic acid compounds,
polyvinylchloride (PVC), polyethylene (PE, HDPE, UHMWPE, etc.),
polystyrene (PS), polyesters (PET, polycaprolacton, polyglycolied,
poylactide, poly-p-dixanone, poly-hydroxy-butylate), polyamides
(Nylons, aromatic polyamides), polypropylene (PP), fluorocarbon
polymers (PTFE, PTFCE, PVF, FEP) and other biocompatible materials.
Other suitable polymers include: collagen and/or collagen
derivative preparations alone or in combination with other
biomaterials, chitin and chitosan preparations.
[0076] Bone derived materials that may be used as segment materials
include, but are not limited to, bone autografts, bone allografts,
bone xenografts, bone-derived tissue, bone-derived collagen, and
the like.
[0077] Any combinations of these materials may be used as a segment
material. Segments may include pellets of any of these materials,
or combinations thereof. Finally, suitable known materials
acceptable for use as hard tissue implant materials include various
osteogenic and osteoinductive compositions, and combinations
thereof. Certain glassy carbon forms are also quite useful.
[0078] Segment materials may also comprise radiopaque materials to
enhance visualization of the implant, or the segments may
incorporate a radiopaque material as a part of a segment (e.g.,
coatings, dispersed, or core materials). Examples of radiopaque
materials include but are not limited to, barium sulfate, tungsten,
bismuth compounds, tantalum, zirconium, platinum, gold, silver,
stainless steel, titanium, alloys thereof, combinations thereof, or
other equivalent materials for use as radiographic agents.
[0079] Coatings
[0080] Segments may include coatings to modify the surface
properties of the segments, to have a biological effect, and/or to
facilitate the insertion or removal of the implant. The coatings
may be of any thickness. In one version, the segment comprises
layers of materials. In one version, the segment has a hollow
core.
[0081] In one version of the implant described herein, a segment or
segments may be coated with a therapeutic or medicinal material,
such as an antibiotic. Additional medicinal materials may include,
but are not limited to, anticoagulants and bone-growth promoting
agents. In one version of the implant, the segments may be coated
with a cross-linking or bonding compound that could facilitate
adhesion either between the segments, with the body region, or
both. In one version the segments are coated with a cross-linker
that can be activated after insertion into the bone cavity, for
example, by adding an activating compound, by time delay, or by
temperature. In one version the segments are coated with a
lubricant.
[0082] The segments may comprise one or more therapeutic or
medicinal materials situated away from the surface, e.g., in pores
within the segments.
[0083] Drug Delivery Using the Implant
[0084] The segments may also be embedded with one or more
therapeutic or medicinal materials. For example, embedding the
segments with an additional material may be particularly useful
when the segment comprises a bioabsorbable (bioerodible) material.
Thus, the segments may be used to deliver any drug or therapy.
Drugs which are particularly useful may include, but are not
limited to, growth factors and/or growth promoters (e.g. bone
derived growth factors (BDGF), bone morphogenetic protein (BMP),
etc.), antibacterials, antivirals, vascularizing agents,
analgesics, anticoagulants, cell and/or gene therapies, etc.
[0085] In one version an implant including a drug is inserted at or
near a wound site. After an appropriate time the implant is
removed. Thus, the implant may serve as a removable wound packing
material. In one version, the implant may be inserted with a
removable drain. In one version, the implant functions as a
removable drain.
[0086] Any portion of the implant may be coated with, implanted
with, embedded with, or made from a therapeutic or medicinal
material, including but not limited to those described herein.
[0087] Flexible Joining Material
[0088] The implant segments are connected in the implant as
installed. The segments may be linked together in such a way that
each segment in the implant is adjacent, perhaps directly adjacent
or in contact with at least one other segment. Generally, each
segment in the implant is adjacent, perhaps directly adjacent or in
contact with at most two other segments. In some variations, the
assembled segments form a linear array. In the version of the
implant shown in FIGS. 1A to 1E, the segments are linked in a
linear array by attachment to a wire, filament, or string 16. The
filament connecting the segments may comprise a separate,
independent filament between each segment, or it may be a single
continuous filament. The filament may comprise different materials,
and may be different lengths. In one version of the implant, the
filament comprises one or more monofilaments. In another version of
the implant, the filament comprises one or more fibers. In a
version of the implant, the filament comprises one or more wires.
The filament may comprise a bioabsorbable material. The filament
may be rapidly bioabsorbable because (unlike the segments) the
filament is not typically load bearing in supporting the
cavity.
[0089] In one version, the implant segments are connected in any
way allowing sufficient flexibility to the resulting implant
constrict so that it may be introduced into a cavity such as a bone
hollow. In one version, the implant segments are flexibly connected
so that a segment may contact another segment upon being planted
into a body region such as a bone hollow.
[0090] The connection material may comprise, for instance, a
string, fiber or wire, variously of single or multiple strands. The
connecting string or fiber may be flexible and allow the segments
to be inserted into the treatment site. Suitable filament materials
include virtually any biocompatible material, including but not
limited to: natural materials (e.g. cottons, silks, collagen, etc),
rubbers (e.g. natural and synthetic rubbers), composite yarns (e.g.
carbon fiber yarns, ceramic fibers, metallic fibers), polymers
(e.g. polyethylene, polyester, polyolefine, polyethylene
terephthalate, polytetrafluoroethylene, polysulfone, nylons,
polylactic acids, polyglycolic acids, mixtures and copolymers of
polylactic and polyglycolic acids (PGLA such as "Vicryl" from
Ethicon and "Dexon" from Davis & Geck), polydioxanone, various
Nylons, polypropylene, etc., and the like). Suture material
(natural and synthetic materials) are examples of particularly
appropriate materials.
[0091] In one variation, the segments are adapted to connect to the
filament, string or wire, for example, by having holes (through
which the flexible joining material is threaded), by having
attachment sites (to which the flexible joining material could be
tied or otherwise attached), or by having a track or groove (which
mate to the flexible joining material). In one variation the
segments are adherent to the string or filament by a glue,
adhesive, or the like.
[0092] In one variation, the segments are connected by adhesives or
glues, such as solvent- or catalyst-curable materials including
Silicone glues, rubbery epoxies, and adhesives suitable for the
materials forming the segments. In one variation the segments are
connected only by adhesives or glues such as those mentioned
above.
[0093] The joining material does not itself have to be flexible, so
long as it allows flexibly joined segments of an implant to "flex."
In one version of the implant, the segments are linked together by
a solid linker. The implant is made flexible by incorporating a
joint (e.g. socket type joins) between the solid linker and the
segment. Solid linkers may be composed of the same material as the
segments. Solid linkers may be wires made of one or more filaments
comprising suitably biocompatible metals or alloys, e.g., stainless
steels or superelastic alloys.
[0094] In the version of the implant shown in FIG. 1E, the segments
are linked together in linear array because they are held within a
flexible tube 19. A flexible tube may be made of virtually any
material, so long as the final implant is adequately flexible to
allow bending of the implant. The flexible tube comprises a solid
or continuous walled tube, a solid or continuous walled tube having
openings in the wall, or a netting woven from string or fiber. The
flexible tube may comprise one or more membrane, optionally made of
an expandable or a stretchable material.
[0095] In one version, the implant segments are linked by an
expandable membrane. The expandable membrane material may be a
fabric that has pores allowing passage of fluids and bone growth
through it. For example, the membrane could be formed of a flexible
polymeric fabric e.g., high molecular weight polyethylene. The
flexible tube may be any material (e.g. woven, non-woven, extruded,
etc) that is adequately flexible. In one version of the implant the
segments within the flexible tube are also linked by a filament,
wire or string.
[0096] The flexible joining material may comprise any suitable
materials including but not limited to: polymers, (e.g.,
polyfluorocarbons such as the various Teflons (including PTFE and
expanded PTFE--ePTFE such as is sold as GORETEX), polypropylene,
polyethylene, polyoxymethylene, polycarbonate, polyesters
(including polyamides such as the Nylons), polyphenylene oxide, and
polyurethane) or elastomeric polymers (e.g. various Silicones,
natural rubber, butadiene-styrene rubber, carboxylic
butadiene-styrene, butadiene-acrylonitrile rubber, carboxylic
butadiene-acrylonitrile rubber, chlorobutadiene rubber,
polybutadiene rubber, silicone rubbers, and acrylate rubbers,
perhaps vulcanized, and other elastomeric materials) or a composite
material.
[0097] The material used to join the segments may also have
additional biological or mechanical properties. For example, the
material may incorporate a therapeutic or medicinal agent for
release (e.g., timed release). Examples of therapeutic agents
include, but are not limited to, antibiotics, analgesics,
anticoagulants, bone growth enhancing agents, cells or gene
therapies, etc. The material may also incorporate other agents and
materials, for example, radiopaque materials to aid visualizing the
implant.
[0098] The joining material may also be severable. It may be
desirable to have implants of certain lengths (e.g. a certain
number of segments). It may also be desirable to have implants that
are continuous, and allow the user to select their length by
removing or cutting the connection between any two segments. For
example, the joining material may be severable by mechanical,
thermal, chemical, or electrical means.
[0099] In one version, the joining material is removable from some
or all of the segments during or after insertion into the
cavity.
[0100] Segment Dimension
[0101] FIGS. 1A to 4D show different variations of the segments 12
compatible with the implant 10. In FIG. 1 the segments are all
shown as spherical pellets. FIG. 1B shows that the pellet size may
vary. FIG. 1C shows that the spacing of the segments on the joining
material (shown as a filament 16) may vary. The lengths of the
implant (e.g. number of pellets) may also vary. Larger 14 segments
and smaller 18 segments are arranged in the linear array. Virtually
any combination of segment sizes and shapes may be used in the
implant. Varying the size as shown in FIG. 1B may change the manner
that the implant "packs" within a bone cavity. For example, packing
of different sized segments may allow different spacing between the
segments, and therefore different opportunities for tissue
in-growth into the implant, different structural properties, and
different loading patterns of adjacent structures.
[0102] Segmented implants may be configured so that the implant is
securely packed into the body region (e.g. non-soft tissue cavity).
Size, shape, and spacing all contribute to the packability of the
implant within the body region. For example, the same implant may
have segments of different sizes, shapes and spacing in order to
optimize packing. Additional factors such as the ability of one or
more segments to move along the linear axis of the implant may also
contribute to packing.
[0103] The size of the segments may be selected to optimize the
insertion into the cavity and use of the implant applicator
described below. Thus, the segments may describe a range of sizes
suitable for use with an applicator and/or suitable for insertion
into a bone cavity of given dimensions. In one version the segments
are between 1 to 40 mm in diameter. In one version the segments are
between 1 to 37 mm in diameter. In one version the segments are
between 1 and 10 mm in diameter. In one version, the segments are
between 1 and 6 mm in diameter. In one version the segments are
approximately 3 mm in diameter. In one version the segment diameter
is an average segment diameter. In one version, the segment
diameter is the maximum diameter of a segment.
[0104] The implant may have different inter-segment spacing. FIG.
1C shows implant segments 12 arranged in a linear array in which
there are larger 20 gaps and smaller 22 gaps between adjacent
segments. Different arrangements of segments along the linear array
may also have desirable effects on the packing behavior of the
implant and the severability of the implant. FIG. 1D shows a
version of the implant in which the spacing between segments is
extremely small 24, potentially reducing the flexibility of the
implant. However, implant flexibility may also be increased by
using more elastic joining materials and potentially allow greater
packing.
[0105] The segments may also be slideable (or partially slideable)
in one (e.g. the long or linear) axis of the implant. In one
version of the implant some of the segments are slideable and some
of the segments are fixed to the joining material. In at least one
version of the implant, the slideable segments allow the implant to
be "tensioned" by tightening the joining material, tending to
stiffen the implant, perhaps to aid in anchoring the implant or
distracting a bone separation, or in anchoring another implant or
device.
[0106] The segments of the implant may also have different shapes,
allowing different packing and implantation properties. FIG. 2
shows examples of segments with different shapes. FIGS. 2A and 2B
show a schematic and perspective view of cubic segment 202 shapes
with rounded edges. The parallel faces of these segments 204 allow
closer packing between adjacent segments. FIG. 2C is also an
implant with cubic segments 206. FIG. 2D shows an implant with
rectangular-shaped segments 208. FIG. 2E shows an implant with
cylindrical segments 210. FIG. 2F shows an implant with a slightly
more complex segment shape having more than six faces. Virtually
any shape that will allow the implant to fill a cavity to distract
a cavity, create a cavity, and/or tighten or secure another
implant, may be used. As used herein, unless the context makes it
clear otherwise, "fill" means that the bone cavity is supported in
three dimensions.
[0107] The implant assemblage described herein describes
space-filling implants (for filling, distracting, void creation,
etc.). Thus, implant segments may be adapted specifically to fill
three dimensional spaces.
[0108] The implant may have segments of different shapes, including
shapes that are configured to communicate with each other, for
example, to interlock. Several examples of interlocking shapes are
shown in FIG. 3A to 3X. In FIG. 3A to 3G, the bullet-shaped 302
segments have a front end 306 and a back end 304, and at least some
of them may slide along the axis of the linear array of the implant
10. The back end of one segment can engage with the front end of an
adjacent segment as shown 310.
[0109] The segments may also be shaped to engage non-adjacent
segments, for example, by having side faces that engage with other
segments. The segments may also be shaped to engage with the walls
of the cavity.
[0110] In FIG. 3E to 3G, the segments have a bullet shape with a
conical nose 320, a cylindrical body 322, a conical recessed rear
324, with linear and rotational inner-locking features, 326. FIG.
3F shows a frontal view of two segments interlocked; FIGS. 3E and
3G show linked segments. The external surface has an advancing
helical ramp 330 for assistance in advancement of a segment
relative to adjacent segments when an axial load and rotational
load are simultaneously applied to the implant. These features aid
in compacting and elevating the hard tissue around the cavity being
filled. The flexible rear extension 334 with external round 332
increase the likelihood of interstitial placement.
[0111] In FIGS. 3H to 3K, the implant comprises common segment
shapes that have six over-lapping male spherical ball geometries
creating a complex external multiply spherical surface 340. FIG. 3H
shows three segments interacting. FIGS. 31 to 3K show linked
segments. These segments may interlock because of the spheres
nesting within the adjacent segments' depression created by the
curved (e.g., semi-spherical) segment surfaces creating multiple
coincident mating tangency points 342. The segments can be arranged
along the connective member in a common entry and exit orientation
344 as in FIGS. 31 and 3K or an alternating pattern 346 as in FIG.
3J.
[0112] In FIGS. 3L and 3M, the implant 10 consists of two different
segment shapes alternating and repeating along the connective
member. The first segment 350 is similar to the segment described
in FIGS. 3H to 3K consisting of six over-lapping male spherical
ball geometries 340. The second segment 352 is a segment that has
six female spherical recesses 354 that will enable tight
interlocking and packing of the implant within the cavity.
[0113] In FIGS. 3N and 3P the implant 10 consists of two different
segment shapes alternating and repeating along the connective
member. The first segment 352 is similar to the segment in FIGS. 3L
and 3M. The second segment 356 is spherical. The configuration of
this implant affords a tight packing with numerous mating
receptacles open to accept the spherical segments and thus may be
less dependent on packing order than other versions.
[0114] In FIG. 3Q, the implant 10 consists of two different segment
shapes alternating and repeating along the connective member. The
first segment 360 is arrowhead-shaped with front 361 and rear faces
362 pointed and made up of two angled faces. The second segment 365
is an elongated arrowhead with otherwise similar front and rear
faces. The segments can be arranged in a manner that will allow a
control of the desired mating and direction that the segments will
follow once the segments leave the delivery cannula and meet
resistance within the cavity. The direction change will be dictated
by slight angular differences between the mating arrowheads.
[0115] In FIG. 3R the implant comprises common segments shaped like
coins 370 with conical spikes 372 protruding from the faces of the
coins. The coin faces 374 have holes through them 376 that
facilitates stacking of the coins, and the spikes are conically
shaped to facilitate the self-centering stacking of the segments.
The stacked coins create common tangency points 180 degrees opposed
from each other that create two parallel planes of support.
[0116] In FIG. 3W the segments have a cross-sectional area that is
rectangular with various previously described front and rear
geometries.
[0117] In FIG. 3X the segment cross-section is triangular with
various previously described front and rear geometries. In some
versions, the segments can have polygonal cross-sections, for
example, hexagonal, octagonal, etc.
[0118] The aspect ratio of the segments' length relative to the
segments' height and width can be varied in order to allow
variations of stacking, packing, steering or elevating, depending
on the desired result.
[0119] Many of the implant segments shown (e.g. FIGS. 1, 2 and
3A-3K and 3Q-3T) are illustrated as substantially `solid.` Implant
segments may also be hollow or have passages for either the joining
material or additional material such as a fluent material (e.g.
cement). Implant segments may also be porous, for example, to
facilitate tissue in-growth, or reduce overall segment weight.
FIGS. 4A and 4B show an implant that has passages 402. FIGS. 4C and
4D show an implant with pores, or hollow spaces, 404 that do not
span the length of the segment. In one version the pores 404 are
dimples.
[0120] Implant segments may also be used with a fluent material.
Examples of fluent materials include cements (e.g. bone cements,
synthetic bone graft cements, etc.), therapeutics (e.g. bone
morphogenic proteins, cells or gene therapies, bone growth
factors), or combinations or substitutions thereof. In one version
the fluent material is applied into the cavity after the implant
has been inserted. In one version the fluent material is added
before the implant. In one version, the fluent material is added
concurrent with insertion of the implant. In one version the fluent
material is inserted into the flexible joining material (e.g. a
flexible tube around the implant segments). The flexible tube may
be impermeable to the fluent material, keeping it substantially
contained within the bone cavity.
[0121] Applicator
[0122] An applicator may be provided to insert a material such as
the implant into a cavity to fill or distract the cavity, and/or to
create or expand a cavity. The applicators described herein may be
used to insert or remove an implant described herein. The
applicators described herein may be used with any compatible
material, including but not limited to individual pellets, fluent
materials, and linear arrays of any materials desirable for
insertion or removal from the body.
[0123] FIG. 5 shows an applicator 50 useful for inserting an
implant into a cavity (e.g. a bone cavity). The applicator has a
cannula 502 having a distal and a proximal end and a lumen 506 with
a handle 505 to aid in controlling the distal end orientation of
the cannula. An implant 10 can be inserted into a bone cavity from
the distal end of the cannula through an opening at the distal end
508. A feed guide 504 connects to the proximal end of the cannula.
The feed guide can insert or withdraw the implant in and out of the
lumen of the cannula through an opening in the proximal end of the
cannula. An applicator may also have a handle 510 or a feed chamber
to store implant material.
[0124] Cannula
[0125] The cannula may be an elongated tubular member having a
lumen or passage to facilitate the movement of an implant through
the cannula. The inner lumen of the cannula may be configured to
bold and allow the passage of an implant. The inner surface of the
lumen may be size-matched to the diameter of the implant.
Alternatively, the size of the implant (e.g. segment size) may be
limited by the inner diameter of the applicator cannula. The inner
surface of the cannula may include a material that facilitates the
movement of an implant (for example, a friction-reducing coating or
a lubricant). The cannula may also allow the passage of a secondary
filling material (e.g. a fluent material) before, after and/or
during the insertion of an implant. An applicator cannula may be
flexible or rigid.
[0126] The cannula may also have a fastener towards the distal end
to hold the cannula in place on the outer surface of the bone being
treated. A fastener or gripper near the distal end of the cannula
may be used to aid the user in holding an applicator steady while
inserting the implant to distract a bone cavity. In one version the
distal end of the cannula is threaded to facilitate insertion into,
for example, the pedicle of a vertebra. The threads may further
serve as a fastener or gripper.
[0127] The distal end of an applicator cannula may be adapted to
aid in penetrating and/or distracting a bone cavity. In one
version, the distal end of the cannula includes a trocar. In one
version, the distal end of the cannula includes a spreader to
separate bone surfaces and aid insertion of an implant.
[0128] The distal opening of an applicator cannula may be located
at the distal-most part of the cannula, or it may be located all or
partly on the perpendicular axis of the cannula (e.g. on the side
of the cannula, or at an angle), allowing more directional filling
of a bone cavity by an applicator. FIG. 6A shows the distal end of
an applicator cannula in which the distal opening is the extreme
distal end of the cannula. The implant 10 exits the applicator 502
through the cannula's distal opening 508, and begins to fill the
bone cavity 602, as shown.
[0129] FIG. 6B shows the distal end of an applicator cannula in
which the distal opening 508 is at a 45.degree. angle from the long
axis of the cannula. Thus the implant 10 is inserted into the bone
cavity 602 at a 45.degree. angle relative to the cannula. FIG. 6C
shows the distal end of an applicator cannula in which the distal
opening 508 is at a 90.degree. angle from the long axis of the
cannula. Thus the implant 10 is inserted into the bone cavity 602
perpendicular to the cannula.
[0130] The outer surface of the cannula may have graduated indicia
that provide depth of penetration information during insertion by
the user.
[0131] An applicator may be operated with a guide cannula. In one
version, an applicator cannula fits into the lumen of a guide
cannula; the guide cannula is used to locate and prepare the bone
cavity for insertion of the implant by an applicator. In one
version, an applicator cannula locks into a guide cannula and the
guide cannula is secured to the bone that is being operated
upon.
[0132] An applicator may also include a cutter configured to sever
the implant by removing the connection between two of the segments
in the linear array of an implant. An example of a cutter 1001 is
shown in FIG. 10. The cutter may be located at least partly at the
distal end of the cannula. The cutter may be located at least
partly within a region of the inner lumen of the cannula. In one
version the cutter is located at an outer surface 509 of the distal
end of an applicator cannula, adjacent to the distal opening 508.
Rotating an external sheath drives a cutting edge across the
cannula's distal opening thereby severing the connection between
implant segments. In this version the cutter is actuated by
rotating the external sheath 510. As illustrated in FIG. 10, the
cutter may be a mechanical cutter capable of applying force to
sever the implant. Additional examples of mechanical cutters
include but are not limited to, a blade, a scissor-like cutter, and
the like. The cutter may be an electrical cutter capable of
applying electrical energy to sever the implant. The cutter may be
a chemical cutter capable of chemically severing the implant, for
example, by applying a compound that reacts with the joining
material of the implant. The cutter may be a thermal cutter which
acts, for example, by heating the material connecting the segments
causing it to release. The cutter may be any combination of
mechanical, electrical, chemical and thermal cutter. The cutter may
be controlled by a cutting controller. The cutting controller may
be controlled directly by the user, or as part of a system.
[0133] Driver
[0134] An applicator may further comprise a driver for applying
force to the implant in order to move the implant within the
cannula to insert the implant into or withdraw the implant from a
bone cavity. An applicator may be a mechanical drive (e.g. linear
driver, a rotary driver, etc.), a pneumatic driver, hydraulic
driver, a magnetic driver, an electric driver, or any combination
thereof. Examples of drivers include, but are not limited to,
rotating auger drivers, and rotating cog drivers. The driver is
preferably a rotatable driver. Force generated by the driver is
transferred to the implant (or a part of the implant), moving the
implant within the cannula, in either the proximal or distal
direction. In one version, the driver is located at least partly
within the cannula. In one version the driver is located at least
partly within the feed guide. An introducer member may comprise a
driver as described here.
[0135] Applicator drivers engage at least a region of an implant.
FIGS. 7A and 7B illustrate a cog driver 702 engaging at least part
of an implant 10. As the cog is rotated about its central axis 708,
in the direction indicated by the arrows (704 and 706), the implant
is moved in the complimentary direction because segments of the
implant 12 have engaged with the cog teeth 712 and are pulled or
pushed in the direction of the rotation as shown. Because the
segments of the implant are connected, movement of at least one of
the segments results in moving the implant. An applicator driver
may comprise more than one cog, or a cog and other driver
components. FIGS. 7A and 7B also show the driver (a cog) at least
partly in the lumen 506 of the applicator cannula 502.
[0136] In one version, the cog is a friction wheel. In one version,
an outer surface of the friction wheel driver engages one or more
regions of an implant (e.g. a segment). When the cog is a friction
wheel, it may not have "teeth" which engage the implant.
[0137] FIG. 7C shows a rotating auger driver. In one version, the
auger is a continuously threaded rod 720; the implant's segments 12
fit within the threading gaps 722. In one version, the rotating
auger is located at least partly within the cannula. At least some
of the implant segments are seated in the auger and are prevented
from rotating around the long axis of the auger, for example by the
geometry of the cannula or chamber surrounding the auger. Rotating
the auger forces the segments (and thus the implant) to move down
the long axis of the rod. Reversing the direction of rotation of
the auger changes the direction that the implant moves. An
applicator driver may comprise more than one auger, or an auger and
other driver components.
[0138] A driver may also be at least partially within the cannula.
In one embodiment the cannula lumen contains a rotatable auger. In
one version the driver is entirely located within the cannula.
[0139] A driver may be located at the proximal end of the
applicator cannula, as indicated in FIG. 7D. Force applied by the
driver moves an implant within the cannula, into or out of the bone
cavity 602. The driver may be capable of moving an implant into or
out of a bone cavity by changing the direction that force is
applied to the implant. An applicator driver may be attached to,
integral to, or coupled to a feed guide.
[0140] Feed Guide
[0141] An applicator may include a feed guide 504 for loading the
applicator cannula with an implant. A feed guide may be coupled to
the proximal end of the cannula as shown in FIG. 5. A feed guide
may comprise a chamber, a cartridge, a track, or other such
structure in which an implant can be held. The feed guide may
orient the implant for inserting or withdrawing from the cannula.
The feed guide may also assist in engaging an implant with a
driver.
[0142] In one version, a feed guide is preloaded with an implant.
For example, it may be advantageous to have the feed guide be a
pre-loaded cartridge holding an implant. Such a feed guide may be
separately sterilized and interchangeable between applicators.
[0143] In one version, the feed guide includes a track configured
to guide an implant. A track may keep the implant from jamming or
tangling within the applicator. A track may further allow a long
implant to be stored compactly. The feed guide may also help
regulate the amount of force needed to move the implant.
[0144] In one version the feed guide may be configured to engage an
implant into a driver. In one version a driver is at least partly
contained within the feed guide. In one version the feed guide
attaches to a driver. In one version the feed guide is configured
as an opening in the cannula into which an implant may be manually
inserted.
[0145] Controller
[0146] An applicator for inserting an implant may also include a
controller for controlling the applicator driver. A controller may
be manually or automatically operated. A controller may control the
force applied by the driver. The controller may control the rate of
insertion/withdrawal of an implant. A controller may control the
direction that force is applied (e.g. forward/reverse). A
controller may be operated by a user.
[0147] An applicator may also include detectors or indicators for
registering implant and applicator parameters. In one version an
applicator includes a detector for determining and/or indicating
the force applied by the applicator to insert or withdraw an
implant. When a cavity is being filled, and particularly when a
bone cavity is being distracted, an implant may be applied using a
force adequate to insure that the implant is properly positioned
within the cavity. Thus it may be important to monitor force and
pressure applied to the implant or volume of implants, and/or the
tissue. Feedback mechanisms may also be used to regulate the
actions of the applicator, including the force applied by the
applicator.
[0148] An applicator may also include detectors or indicators for
indicating the status of the implant. For example, a sensor may
indicate the amount of implant inserted, the amount of implant left
in the applicator, and/or the position of the implant within the
applicator or the bone cavity. In one version, the applicator
includes a force gauge for detecting the force applied by the
applicator on the implant being inserted. The applicator may also
include a display capable of indicating a status. Examples of the
kinds of status that the display could indicate include, but are
not limited to, force applied, total volume, linear feed rate,
volume feed rate, amount of implant material inserted, and/or
amount of implant material remaining in the applicator.
[0149] Implants Compatible with the Applicator
[0150] The application described herein may be used with any
compatible implant, including but not limited to discrete (loose)
pellets or segments of any material (including segments or pellets
as described herein), fluent materials (e.g. cements, bone fillers,
etc.), and any implant, particularly those comprising a linear
array of elements. Such applicators may also be useful for filling
and distracting bone cavities. In one version the applicator
comprises a cannula and a driver where the driver further comprises
an auger or a cog. The auger or cog propels the discrete pellet,
fluent material, or combination of implants, discrete pellets
and/or fluent material, down the cannula in order to fill or
distract the cavity into which the cannula has been inserted. It
may be particularly advantageous to use the applicator with
flexibly connected implants, including those described herein,
because the applicator may be used to controllably insert and
remove flexibly connected implants.
[0151] Additional exemplary applications of the applicator and/or
implants as described herein are given below. These examples are
intended only to illustrate various embodiments of the implant,
applicator, and methods of use, and are not intended to be in any
way limiting.
EXAMPLES
[0152] In general, the implants and/or applicators described herein
may be used to distract an existing body region. In one version,
the body region is a non-soft tissue cavity. In one version, the
body region is a hard tissue cavity, such as a bone cavity arising
from a tumor, injury or surgery.
[0153] FIG. 8A to 8C shows an example of inserting an implant into
a bone cavity 602. In this example, the bone cavity is part of a
vertebral compression fracture. Other examples of bone disorders
and fractures which may be distracted include, but are not limited
to, tibial plateau fractures, femoral head necrosis, osteonecrosis
of the hip, knee injury, etc. FIG. 8A shows an applicator 502
inserted into a vertebral compression fracture 804 through the
vertebral pedicle 808; the applicator is inserting an implant 10
into the collapsed region. The implant is shown as a linear array
of pellets 12. These segments of the implant may be continuously
added to the bone cavity to first fill and pack within the cavity.
Once the cavity is filled, adding further segments elevates the
collapsed bone. FIG. 8B shows the bone cavity after it has been
distracted by application of the implant. While some of the
individual segments of the implant remain joined and connected to
the applicator, the user may adjust the amount of distraction by
removing and/or adding segments of the implant until the shape of
the collapsed vertebra has been set to an optimal shape. In one
version, the optimal shape is the natural (uncompressed)
position.
[0154] Compaction of the Implant within a Cavity
[0155] Once an implant is inserted, it may be compacted within the
body cavity by packing the individual segments. Any appropriate
device or method may be used to compact the implant segments. These
include utilizing vibration (e.g. ultrasonics, through the delivery
of a second cannula or probe, for example, through the second
pedicle) or physical compaction (e.g. using a curved probe or tamp
through a pedicle path or with an internal or external sheath.
Compaction may be particularly useful when filling hard tissue
cavities such as bone cavities.
[0156] Closing the Filled Cavity
[0157] A cavity opening through which an implant was inserted may
be closed and/or sealed to maintain the compaction, and to prevent
the loss of implant material from the cavity. After filling and/or
distracting a cavity, a user may cut the implant and remove the
applicator cannula. FIG. 8C shows that the user may also block 802
or otherwise close the opening into the bone cavity, for example,
by the local application of a cement material through the cannula
(or another cannula). Other methods for closing the void may
include tapered pins, screws with blunt head and tip, or even
screws with compressible tip members such as a spring to absorb,
minimize, or prevent settling of the implant.
[0158] FIG. 9 shows an example of a screw closure 900 for use with
an implant that comprises a spring 903 for applying pressure to an
implant within a cavity. The screw includes threads 905. After
distracting and/or filling a hard tissue cavity as described, the
screw closure is screwed into the opening through which the implant
was inserted. The spring-loaded tip 910 of the screw is blunt, and
applies pressure onto the inserted implant. Thus, the screw can
minimize any settling or further compaction that may occur after
the insertion of the implant by applying pressure to help keep the
implant compacted.
[0159] In general, implants and applicators as described herein may
be used for filling cavities that do not require distraction.
[0160] A secondary filling material may also be used. For example,
when filling a bone cavity, fluent bone filler may also be used to
fill the cavity in addition to the solid implant. The combination
of hard segment and fluid filler may provide added stability. The
fluent material (e.g. cement) may also harden into a solid. In
addition, the implant segments may reduce leakage of additional
bone filler (such as bone cement) by blocking openings in the
cavity that fluent filler would otherwise leak through. Less fluent
filler may be needed if it is used after the solid implant, further
reducing the risk of harmful leakage. In one version, secondary
filling material may be applied in conjunction with an expandable
membrane around the implant segments, preventing any substantial
leakage from the bone cavity.
[0161] In general, the implants and/or applicators described herein
may be used to distract a cavity without being left in the cavity
after distraction. For example, an implant may be used to create or
enlarge a cavity. In one example, an implant may be inserted into a
body region void to expand the void. The surfaces of the body
region void will be compressed by the implant, causing it to
expand. After removing the implant, the cavity may remain expanded,
facilitating further procedures (e.g. insertion of additional
devices or materials, etc). Similarly, a hard tissue cavity such as
a bone cavity may be enlarged or reshaped by inserting an implant
which can then be removed or left within the non-soft tissue
cavity.
[0162] It may be desirable to leave the implant in the tissue for
an extended period of time, up to and including the lifetime of the
patient. In one version, the implant is a permanent implant for
filling and/or distracting body regions to provide long-term
support and shape to the body region. In one version, the implant
is intended to be used for a period of at least six months. In one
version, the implant is intended to be used for a period of at
least a year. In one version, the implant is intended to be used
for a period of many years. Implants intended for long-term use may
be made of materials which do not lose a significant amount of
their strength or shape over time after implantation.
[0163] In general, the implants and/or applicators described herein
may be used to secure another implant. For example, a bone screw
may be inserted into an implant filling a bone cavity. This may be
particularly useful when it is desirable to use a bone screw in
weakened (e.g. osteoporotic or necrotic) bone tissue. In another
version, the implant described herein may be inserted to secure an
existing implant.
[0164] In summary, the described implants, applicators and methods
of using them may be used to fill and/or distract a non-soft tissue
including a bone cavity, in particular a vertebral compression
fracture. The implant may achieve many advantages not realized with
other devices intended to fill and/or distract a bone cavity. In
particular, the implant described herein substantially reduces the
chance of harmful leakage of bone filler material and provides
three-dimensional support to the bone cavity.
[0165] Although the above examples have described primarily the
filling of bone cavities, and particularly vertebral compression
fractures, the implant, applicator and methods described herein may
be used on any tissue cavity, including but not limited to those
arising from trauma, fractures, non-unions, tumors, cysts, created
by a pathology or by the action of a surgeon. It will be
appreciated by persons skilled in the art that numerous variations
and/or modifications may be made to the described device as
specifically shown here without departing from the spirit or scope
of that broader disclosure. The various examples are, therefore, to
be considered in all respects as illustrative and not
restrictive.
* * * * *