U.S. patent application number 12/986995 was filed with the patent office on 2011-06-16 for devices and methods using an expandable body with internal restraint for compressing cancellous bone.
This patent application is currently assigned to KYPHON S RL. Invention is credited to Cesar Ico, Mark A. Reiley, Paul Reiss, Arie Scholten, Karen D. Talmadge.
Application Number | 20110144688 12/986995 |
Document ID | / |
Family ID | 21934626 |
Filed Date | 2011-06-16 |
United States Patent
Application |
20110144688 |
Kind Code |
A1 |
Reiss; Paul ; et
al. |
June 16, 2011 |
DEVICES AND METHODS USING AN EXPANDABLE BODY WITH INTERNAL
RESTRAINT FOR COMPRESSING CANCELLOUS BONE
Abstract
Devices and methods compress cancellous bone. In one
arrangement, the devices and methods make use of an expandable body
that includes an internal restraint coupled to the body. The
internal restraint directs expansion of the body. In one
arrangement, a method for treating bone inserts the device having
the internal restraint inside bone and causes directed expansion of
the body in cancellous bone. Cancellous bone is compacted by the
directed expansion.
Inventors: |
Reiss; Paul; (Bernardsville,
NJ) ; Ico; Cesar; (San Francisco, CA) ;
Talmadge; Karen D.; (Los Altos Hills, CA) ; Reiley;
Mark A.; (Piedmont, CA) ; Scholten; Arie;
(Manteca, CA) |
Assignee: |
KYPHON S RL
Neuchatel
CH
|
Family ID: |
21934626 |
Appl. No.: |
12/986995 |
Filed: |
January 7, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11827120 |
Jul 10, 2007 |
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12986995 |
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10863727 |
Jun 8, 2004 |
7241303 |
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11827120 |
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|
10044843 |
Jan 11, 2002 |
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10863727 |
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10054736 |
Oct 24, 2001 |
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10044843 |
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09754451 |
Jan 4, 2001 |
6899719 |
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10054736 |
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|
08871114 |
Jun 9, 1997 |
6248110 |
|
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09754451 |
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08659678 |
Jun 5, 1996 |
5827289 |
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08871114 |
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08485394 |
Jun 7, 1995 |
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08659678 |
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08188224 |
Jan 26, 1994 |
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08485394 |
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Current U.S.
Class: |
606/192 |
Current CPC
Class: |
A61F 2002/30113
20130101; A61B 2050/0065 20160201; A61F 2/44 20130101; A61F
2002/2871 20130101; A61F 2002/30225 20130101; A61M 29/02 20130101;
A61F 2310/00353 20130101; A61F 2/4611 20130101; A61F 2/2846
20130101; A61F 2002/30313 20130101; A61F 2230/0015 20130101; A61F
2230/0071 20130101; A61M 2025/1072 20130101; A61B 2050/3015
20160201; A61B 17/8805 20130101; A61F 2002/30245 20130101; A61F
2230/0069 20130101; A61F 2/4601 20130101; A61B 10/025 20130101;
A61B 2017/0256 20130101; A61B 17/02 20130101; A61F 2/28 20130101;
A61F 2002/2832 20130101; A61F 2002/2892 20130101; A61F 2/3601
20130101; A61F 2002/2853 20130101; A61F 2220/005 20130101; A61M
25/10 20130101; A61F 2002/30133 20130101; A61F 2230/0006 20130101;
A61F 2250/0063 20130101; A61M 2210/02 20130101; A61M 2210/1003
20130101; A61B 2017/00544 20130101; A61B 17/00234 20130101; A61F
2002/30462 20130101; A61F 2002/30909 20130101; A61F 2230/0013
20130101; A61B 50/33 20160201; A61B 2017/00539 20130101; A61F
2002/30115 20130101; A61F 2002/30586 20130101; A61F 2002/30228
20130101; A61F 2002/30242 20130101; A61F 2/441 20130101; A61F
2002/30125 20130101; A61F 2310/0097 20130101; A61F 2230/0076
20130101; A61F 2002/30599 20130101; A61F 2002/30308 20130101; A61F
2002/302 20130101; A61F 2230/0065 20130101; A61M 2025/1059
20130101; A61B 2017/00557 20130101; A61B 17/8855 20130101; A61F
2002/2828 20130101; A61B 17/72 20130101; A61F 2002/4217 20130101;
A61F 2002/2835 20130101; A61F 2002/30285 20130101; A61F 2002/3611
20130101; A61F 2002/4685 20130101; A61F 2230/0063 20130101; A61F
2310/00293 20130101; A61M 25/1006 20130101; A61F 2002/30131
20130101; A61B 17/7275 20130101; A61F 2002/30253 20130101; A61F
2220/0075 20130101; A61B 2010/0258 20130101; A61B 90/94 20160201;
A61F 2002/2817 20130101; A61B 17/7097 20130101; A61F 2/389
20130101; A61B 90/39 20160201; A61M 25/1009 20130101; A61F
2230/0008 20130101; A61F 2002/30288 20130101; A61B 17/8866
20130101; A61F 2002/30448 20130101; A61F 2002/30686 20130101; A61F
2002/4062 20130101; A61M 25/1011 20130101; A61F 2002/3625 20130101;
A61F 2002/30581 20130101; A61M 25/1002 20130101; A61F 2002/2825
20130101; A61F 2002/30677 20130101; A61F 2002/4627 20130101; A61F
2002/4635 20130101 |
Class at
Publication: |
606/192 |
International
Class: |
A61M 29/00 20060101
A61M029/00 |
Claims
1. A device for compressing cancellous bone, the device comprising:
an inflatable element; a first elongate element for delivering an
inflation fluid to the inflatable element, a distal tip of the
first elongate element being connected to a proximal end of the
inflatable element; and a second elongate element, the second
elongate element being substantially aligned with at least a
portion of the first elongate element, wherein a distal tip of the
second elongate element extends past the distal tip of the first
elongate element, and wherein expansion of a distal end of the
inflatable element is not restrained by the distal tip of the
second elongate element.
2. The device of claim 1 further comprising a radiopaque marker
positioned inside the inflatable element.
3. The device of claim 1 wherein the proximal end of the inflatable
element extends over the distal tip of the first elongate
element.
4. The device of claim 1 wherein the distal tip of the first
elongate element is connected to the proximal end of the inflatable
element by heat bonding.
5. The device of claim 1 wherein the distal tip of the first
elongate element is connected to the proximal end of the inflatable
element by an adhesive.
6. The device of claim 1 wherein the distal tip of the second
elongate element extends distally beyond the distal end of the
inflatable element.
7. The device of claim 1 wherein the distal tip of the second
elongate element is located proximally of the distal end of the
inflatable element.
8. The device of claim 1 wherein the second elongate element is
attached to the first elongate element.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of co-pending application
Ser. No. 10/863,727 filed on 8 Jun. 2004, which is continuation of
co-pending application Ser. No. 10/044,843, filed Jan. 11, 2002,
which is a divisional of application Ser. No. 10/054,736, filed
Oct. 24, 2001, now abandoned, and which is also a
continuation-in-part of application Ser. No. 09/754,451, filed Jan.
4, 2001, which is a continuation of application Ser. No.
08/871,114, filed Jun. 9, 1997, now U.S. Pat. No. 6,248,110, which
is a continuation-in-part of application Ser. No. 08/659,678, filed
Jun. 5, 1996, now U.S. Pat. No. 5,827,289, which is a
continuation-in-part of application Ser. No. 08/485,394, filed Jun.
7, 1995, row abandoned, which is a continuation-in-part of
application Ser. No. 08/188,224, filed Jan. 26, 1994, now
abandoned.
FIELD OF THE INVENTION
[0002] This invention relates to the treatment of bone conditions
in human and other animals.
BACKGROUND OF THE INVENTION
[0003] When cancellous bone becomes diseased, for example, because
of osteoporosis, avascular necrosis, or cancer, the surrounding
cortical bone becomes more prone to compression fracture or
collapse. This is at least in part because the cancellous bone no
longer provides interior support for the surrounding cortical bone.
The bone disease may also affect the strength and integrity of the
surrounding cortical bone, further disposing the bone to fracture
and/or collapse.
[0004] There are 2 million fractures each year in the United
States, of which about 1.3 million are caused by osteoporosis
alone. There are also other bone diseases involving infected bone,
poorly healing bone, or bone fractured by severe trauma. Moreover,
the use of various drugs, such as steroids, tobacco and/or the
excessive intake of alcohol, can significantly degrade bone
quality. Any of these conditions, if not successfully addressed,
can result in fracture and/or collapse of bone, causing
deformities, chronic complications, and an overall adverse impact
upon the quality of life.
[0005] U.S. Pat. Nos. 4,969,888 and 5,108,404 disclose apparatus
and methods for the fixation of fractures or other conditions of
human and other animal bone systems, both osteoporotic and
non-osteoporotic. Among other inventions, these patents disclose
devices and methods that employ an expandable body to compress
cancellous bone and/or create an interior cavity within the
targeted bone. The cavity receives a filling material, which
hardens and provides renewed interior structural support for
cortical bone.
[0006] The better and more efficacious treatment of bone disease
that these patents promise can be more fully realized with improved
systems and methods for making and deploying expandable bodies in
bone.
SUMMARY OF THE INVENTION
[0007] One aspect of the invention provides devices and methods for
compressing cancellous bone. In one arrangement, the devices and
methods make use of an expandable body that includes an internal
restraint coupled to the body. The internal restraint directs
expansion of the body. In one arrangement, a method for treating
bone inserts the device having the internal restraint inside bone
and causes directed expansion of the body in cancellous bone.
Cancellous bone is compacted by the directed expansion.
[0008] Another aspect of the invention provides devices and methods
for compacting cancellous bone. In one arrangement, the devices and
methods make use of a body adapted to be inserted into bone and
undergo expansion in cancellous bone to compact cancellous bone.
The body includes material that, during the expansion in cancellous
bone, applies a force capable of moving fractured cortical bone,
and further includes an interior membrane to constrain the
expansion in cancellous bone. In one arrangement, a method for
treating bone inserts the device having the internal membrane
inside bone and causes restrained expansion of the body in
cancellous bone. Cancellous bone is compacted by the restrained
expansion.
[0009] Features and advantages of the invention are set forth in
the following Description and Drawings, as well as in the appended
Claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a perspective view of a first embodiment of a
balloon constructed in accordance with the teachings of the present
invention, the embodiment being in the shape of a stacked doughnut
assembly;
[0011] FIG. 2 is a vertical section through the balloon of FIG. 1
showing the way in which the doughnut portions of the balloon of
FIG. 1 fit into a cavity of a vertebral body;
[0012] FIG. 3 is a schematic view of another embodiment of the
balloon of the present invention showing three stacked balloons and
string-like restraints for limiting the expansion of the balloon in
various directions of inflation;
[0013] FIG. 4 is a top plan view of a spherical balloon having a
cylindrical ring surrounding the balloon;
[0014] FIG. 5 is a vertical section through the spherical balloon
and ring of FIG. 4;
[0015] FIG. 6 shows an oblong-shaped balloon with a catheter
extending into the central portion of the balloon;
[0016] FIG. 6A is a perspective view of one way in which a catheter
can be arranged relative to the inner tubes for inflating the
balloon of FIG. 6;
[0017] FIG. 7 is a suction tube and a contrast injection tube for
carrying out the inflation of the balloon and removal of debris
caused by expansion from the balloon itself;
[0018] FIG. 8 is a vertical section through a balloon after it has
been deflated and as it is being inserted into the vertebral body
of a human;
[0019] FIGS. 9, 9A, and 9B are side elevational view of a cannula
showing how the protective sleeve or guard member can expand when
leaving the cannula;
[0020] FIG. 10 is a perspective view of another embodiment of a
balloon of the present invention formed in the share of a kidney
bean;
[0021] FIG. 11 is a perspective view of the vertebral bone showing
the kidney shaped balloon of FIG. 10 inserted in the bone and
expanded;
[0022] FIG. 12 is a top view of a kidney shaped balloon formed of
several compartments by a heating element or branding tool;
[0023] FIG. 13 is a cross-sectional view taken along line 13-13 of
FIG. 12 but with two kidney shaped balloons that have been
stacked;
[0024] FIG. 14 is a view similar to FIG. 11 but showing the stacked
kidney shaped balloon of FIG. 13 in the vertebral bone;
[0025] FIG. 15 is a top view of a kidney balloon showing outer
tufts holding inner strings in place interconnecting the top and
bottom walls of the balloon;
[0026] FIG. 16 is a cross-sectional view taken along line 16-16 of
FIG. 15;
[0027] FIG. 17A is a dorsal view of a humpback banana balloon in a
right distal radius;
[0028] FIG. 17B is a cross-sectional view of FIG. 17A taken along
line 17B-17B of FIG. 17A;
[0029] FIG. 18 is a spherical balloon with a base in a proximal
humerus viewed from the front (anterior) of the left proximal
humerus;
[0030] FIG. 19A is the front (anterior) view of the proximal tibia
with the elliptical cylinder balloon introduced beneath the medial
tibial plateau;
[0031] FIG. 19B is a three-quarter view of the balloon of FIG.
19A;
[0032] FIG. 19C is a side elevational view of the balloon of FIG.
19A;
[0033] FIG. 19D is a top plan view of the balloon of FIG. 19A;
[0034] FIG. 20 is a spherically shaped balloon for treating
avascular necrosis of the head of the femur (or humerus) as seen
from the front (anterior) of the left hip;
[0035] FIG. 20A is a side view of a hemispherically shaped balloon
for treating avascular necrosis of the head of the femur (or
humerus);
[0036] FIG. 21 is a balloon for preventing and/or treating hip
fracture as seen from the anterior (front) of the left hip;
[0037] FIGS. 22A-C are schematic illustrations of a representative
method and system for delivering a therapeutic substance to a bone
according to the present invention; and
[0038] FIG. 23 is another embodiment of an expandable structure
incorporating an internal expansion restraint;
[0039] FIGS. 24A-C are cross-sectional views of the expandable
structure of FIG. 23 undergoing expansion in air;
[0040] FIG. 25A is a front view of another embodiment of an
expandable structure for use in compressing cancellous bone and/or
displacing cortical bone;
[0041] FIG. 25B is a side view of the structure of FIG. 25A;
[0042] FIG. 25C is a perspective view of the structure of FIG. 25A;
and
[0043] FIG. 26A is side view of a cavity forming device carrying an
expandable structure of the type shown in FIGS. 23 and 24A to
24C;
[0044] FIG. 268 is a perspective view of the distal end of the
cavity forming device shown in FIG. 26A, showing the assembly of
the proximal end of the expandable structure to the distal end of
the outer catheter body of the device;
[0045] FIG. 26C is a perspective view of the distal end of the
cavity forming device shown in FIG. 26A, after the proximal and
distal ends of the expandable structure have been secured,
respectively, to the distal end of the outer catheter body and the
distal end of the inner catheter body of the device;
[0046] FIG. 27 is another embodiment of an expandable structure;
and
[0047] FIG. 28 is a side view of the distal tip of a cavity-forming
device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
I. Balloons for Anatomical Structures
[0048] The present invention is directed to a balloon that can be
used to treat bones predisposed to fracture or collapse. These
balloons comprise one or more inflatable balloon bodies for
insertion into said bone. The body has a preferred shape and size
when substantially inflated sufficient to compress at least a
portion of the inner cancellous bone to create a cavity in the
cancellous bone and/or to restore the original position of the
outer cortical bone, if fractured or collapsed. In various
embodiments, the balloon body is restrained to create said
preferred shape and size so that the fully inflated balloon body is
desirably inhibited from applying substantial pressure to a single
point on the inner surface of the outer cortical bone if said bone
is unfractured or uncollapsed.
[0049] In addition to the shape of the inflatable device itself,
another important aspect is the construction of the wall or walls
of the balloon such that the proper inflation of the balloon body
is achieved to provide for optimum compression of the cancellous
bone. The material of the balloon is also desirably chosen so the
balloon can be inserted quickly and easily into a bone through a
cannula, yet can also withstand high pressures when inflated. For
example, the material could be chosen to facilitate folding of the
balloon. Alternatively, the material could desirably allow plastic,
elastic and/or semi-elastic deformation of the balloon during
inflation. The material will also desirably resist abrasion and/or
puncture of the balloon when in contact with cortical and/or
cancellous bone during introduction and inflation of the balloon.
The balloon can also include optional ridges or indentations which
are imparted to the cavity, desirably remaining in the cavity walls
after the balloon has been removed, to enhance the stability of the
bone void filler. Also, the inflatable device can be made to have
an optional, built-in suction catheter. This may be used to remove
any fat or fluid extruded from the bone during balloon inflation in
the bone. Also, the balloon body can be protected from puncture (by
the surrounding bone or cannula) by being covered while inside the
cannula and/or bone with an optional protective sleeve of suitable
materials, such as Kevlar.RTM. fiber products or polyethylene
tetraphthalate (PET) or other polymer or substance that can protect
the balloon. This covering material may also provide the additional
advantage of reducing friction between the balloon and cannula, or
it can incorporate a lubricating material, such as silicone, to
reduce friction. One important purpose of the inflatable device,
therefore, is the forming or enlarging of a cavity or passage in a
bone, especially in, but not limited to, vertebral bodies.
[0050] In one aspect, the invention provides an improved,
balloon-like inflatable device for use in carrying out a surgical
protocol of cavity formation in bones to enhance the efficiency of
the protocol, to minimize the time required to performing the
surgery for which the protocol is designed, and to improve the
clinical outcome. If desired, these balloons may approximate the
inner shape of the bone they are inside of in order to maximally
compress cancellous bone. They may also have additional design
elements to achieve specific clinical goals. In various
embodiments, they are made of inelastic, semi-elastic, elastomeric
or plastically deformable materials and kept in their defined
configurations when inflated, by various restraints, including, but
not limited to, use of inelastic, semi-elastic, elastomeric or
plastically deformable materials in conjunction with the balloon
body, seams in the balloon body created by bonding or fusing
separate pieces of material together, or by fusing or bonding
together opposing sides of the balloon body, woven material bonded
inside or outside the balloon body, strings or bands placed at
selected points in the balloon body, and stacking balloons of
similar or different sizes or shapes on top of each other by gluing
or by heat fusing them together. Optional ridges or indentations
created by the foregoing structures, or added on by bonding
additional material, can increase stability of the bone void
filler. The ridges or indentations may also help keep the bone
filler material in a desired position during subsequent loading
and/or healing of the treated bone. Optional suction devices,
preferably placed so that if at least one such device is located
approximate the lowest point of the cavity being formed, will
desirably allow the cavity to be cleaned and/or permit fluid or
solids to be removed from and/or introduced into the cavity before
filling.
[0051] Among the various embodiments of the present invention are
the following:
[0052] 1. A doughnut (or torus) shaped balloon with an optional
built-in suction catheter to remove fat and other products extruded
during balloon expansion.
[0053] 2. A balloon with a spherical outer shape surrounded by a
ring-shaped balloon segment for body cavity formation.
[0054] 3. A balloon which is kidney bean shaped in configuration.
Such a balloon can be constructed in a single layer, or several
layers stacked on top of each other. This embodiment can also be a
square or a rectangle instead of a kidney bean.
[0055] 4. A spherically shaped balloon approximating the size of
the head of the femur (i.e. the proximal femoral epiphysis). Such a
balloon can also be a hemisphere.
[0056] 5. A balloon in the shape of a humpbacked banana or a
modified pyramid shape approximating the configuration of the
distal end of the radius (i.e. the distal radial epiphysis and
metaphysis).
[0057] 6. A balloon in the shape of a cylindrical ellipse to
approximate the configuration of either the medial half or the
lateral half of the proximal tibial epiphysis. Such a balloon can
also be constructed to approximate the configuration of both halves
of the proximal tibial epiphysis.
[0058] 7. A balloon in the shape of a sphere on a base to
approximate the shape of the proximal humeral epiphysis and
metaphysis with a plug to compress cancellous bone into the
diaphysis, sealing it off. Such an embodiment can also be a
cylinder.
[0059] 8. A balloon in the shape of a boomerang to approximate the
inside of the femoral head, neck and lesser trochanter, allowing a
procedure to prevent hip fracture.
[0060] 9. A balloon in the shape of a cylinder to approximate the
size and shape of the inside of the proximal humerus or of the
distal radius.
[0061] 10. A balloon in the shape of a peanut or hourglass with an
internal membrane to constrain expansion preferentially along one
or more axes.
[0062] 11. A balloon in the shape of a disk.
[0063] 12. A balloon device with an optional suction device.
[0064] 13. Protective sheaths to act as puncture guard members
optionally covering each balloon inside its catheter.
[0065] The present invention, therefore, provides improved,
inflatable devices for creating or enlarging a cavity or passage in
a bone wherein the devices are inserted into the bone. In various
embodiments, the configuration of each device can be defined by the
surrounding cortical bone and adjacent internal structures, and is
designed to occupy up to 70-90% of the volume of the inside of the
bone, although balloons that are as small as about 40% (or less)
and as large as about 99% are workable for fractures. In various
other embodiments, the inflated balloon size may be as small as 10%
of the cancellous bone volume of the area of bone being treated,
such as for the treatment of avascular necrosis and/or cancer, due
to the localized nature of the fracture, collapse and/or treatment
area. The fully expanded size and shape of the balloon is desirably
regulated by material in selected portions of the balloon body
whose resistance to expansion creates a restraint as well as by
either internal or external restraints formed in the device
including, but not limited to, mesh work, webbing, membranes,
partitions or baffles, a winding, spooling or other material
laminated to portions of the balloon body, continuous or
non-continuous strings across the interior of the balloon held in
place at specific locations by bonding to the inside of the balloon
(by glue, welding, etc.) or by threading these strings through to
the outside, and seams in the balloon body created by bonding two
pieces of body together or by bonding opposing sides of a body
through glue or heat. Aside from the use of different materials,
the objectives of the present invention could similarly be
accomplished by utilizing different thicknesses of materials to
regulate the expansion of the balloon body. Moreover, the use of
similar materials of differing elasticity, for example a
polyurethane plastic balloon having discrete sections that are
cross-linked by gamma radiation exposure and which are thus less
prone to expansion, could accomplish the objectives of the present
invention as well.
[0066] Spherical portions of balloons may be restrained by using
inelastic, semi-elastic, elastic and elastomeric materials in the
construction of the balloon body, or may be additionally restrained
as just described. The material of the balloon can be a non-elastic
material, such as polyethylene tetraphthalate (PET), nylon,
Kevlar.RTM. or other patented or nonpatented medical balloon
materials. It can also be made of semi-elastic materials, such as
silicone, rubber, thermoplastic rubbers and elastomers or elastic
materials such as latex or polyurethane, if appropriate restraints
are incorporated. The restraints can be continuous or made of
discrete elements of a flexible, inelastic high tensile strength
material including, but not limited to, the materials described in
U.S. Pat. No. 4,706,670, which is incorporated herein by reference.
The thickness of the balloon wall is typically in the range of
2/1000ths to 25/1000ths of an inch, although other thicknesses that
can withstand increased pressures, such as 250-400 psi or greater,
even up to 500, 1000 or 2000 psi, may be used.
[0067] One important goal of percutaneous vertebral body
augmentation of the present invention is to provide a balloon which
can create a cavity inside the vertebral body whose configuration
is optimal for supporting the bone. Another important goal is to
move the top and bottom of the vertebral body (otherwise known as
the upper and lower endplates) toward a more normal anatomical
position to restore height where possible. Both of these
objectives, however, are desirably achieved without significantly
altering the outer dimensions of the sides of the vertebral body,
either by fracturing the cortical sidewalls of the vertebral body
or by moving already fractured bone in the sidewalls.
[0068] The present invention satisfies these goals through the
design of inflatable devices to be described. Inflating such a
device desirably creates a cavity within the calcium-containing
soft cancellous bone (such as by compressing the cancellous bone)
and/or desirably displaces surrounding cortical bone towards a more
normal anatomical position.
[0069] In one embodiment, the balloon body desirably recreates the
shape of the inside of an unfractured vertebral body, and optimally
grows no more than a maximum of 70 to 90% of the inner volume. The
balloons of these embodiments are inelastic, so designed such that
maximally inflating them will desirably recreate the predetermined
shape and size. However, conventional balloons become spherical
when inflated. Spherical shapes do not typically permit the
hardened bone void filler to support the spine adequately, because
they can create a generally spherical cavity which, when filled
with filler material, makes single points of contact on the
vertebral body surfaces (the equivalent of a circle inside a
square, or a sphere inside a cylinder). In contrast, various
embodiments of the balloons of the present invention more generally
recreate the flat surfaces of the vertebral body by incorporating
restraints that maintain the balloon in desired shapes. These
desired shapes create cavities which, when filled with filler
material, desirably distribute the load transferred from the
vertebral body surfaces to the bone void fillers, which ultimately
strengthens the spine. In addition, the volume of bone void filler
that fills these cavities desirably creates a thick mantle of
cement (for example a thickness of 4 mm or greater), which
increases the compressive strength of the filler material. Another
useful feature of various embodiments is the incorporation of
ridges in the balloons which can leave one or more imprints in the
walls of the cavity created within the compressed cancellous bone.
The resulting bone void filler "fingers" which will ultimately fill
these imprints can provide enhanced stability, and reduce the
opportunity for the filler material to shift or displace within the
vertebral body under compressive loading of the spine.
[0070] Balloons which can optimally compress cancellous bone in
vertebral bodies include the balloons listed as balloon types 1-3,
10 and 12 above. Some of these balloons are desirably configured to
approximate the shape of the vertebral body. Since the balloon can
be chosen to occupy less than the total inner volume (prior to
fracture) of the targeted vertebral body, inflation of the balloon
will desirably not exert undue pressure on the surrounding cortical
sidewalls of the vertebral body (the sidewalls of the vertebral
body will desirably not be expand beyond their existing
size--either fractured or unfractured). However, since the upper
and lower end plates of the vertebral body are typically depressed
in a compression fracture, and the balloon can be approximately the
height of an unfractured vertebral body, inflation of the balloon
can move the top and bottom end plates back towards their
pre-fractured position and/or orientation. Moreover, a plurality of
individual balloons can be utilized inside the vertebral body, such
as by being stacked, and stacks containing any of the disclosed
balloon types can be mixed in shape and/or size to provide greater
flexibility and/or control.
[0071] A primary goal of percutaneous femoral (or humeral) head
augmentation (balloon type 4), percutaneous distal radius
augmentation (balloon type 5), percutaneous proximal tibial
augmentation (balloon type 6), and percutaneous proximal humeral
augmentation (balloon type 7) is to create a cavity whose
configuration is optimal to support the bone to be treated. Another
important goal is to compress avascular (or aseptic) necrotic bone
or to support avascular necrotic bone. Yet another important goal
is to help realign the fracture fragments. These goals are
generally achieved by exerting pressure primarily on the cancellous
bone which may be transferred to the surrounding cortical bone.
Pressure directly on a small section of the cortical bone could
conceivably cause worsening of the fracture, which, while not
precluded, is desirably avoided. The design of various embodiments
of the inflatable devices approximates the shape of the bone to be
treated. The approximate volume of the cavity made by the
inflatable devices) can be as much as 70 to 90% of the volume of
the bone to be treated. In the case of avascular necrosis,
depending upon the extent of the avascular necrosis, a smaller or
larger cavity inside bone will be formed. In some cases, if the
area of avascular necrosis is small, a small balloon will be
utilized which might create a cavity only 10 to 15% of the total
volume. If larger areas are involved with avascular necrosis, then
one or more larger balloons could be utilized which might create a
much larger cavity, including cavities as large as 80 to 90% of the
volume of the bone (or greater). The present invention satisfies
these goals through the design of the inflatable devices to be
described.
[0072] For example, percutaneous hip augmentation (as shown in
connection with balloon type 8) is designed to prevent and/or treat
hip fracture by compacting weak cancellous bone in the femur where
hip fractures occur and replacing it with an appropriate supporting
material. The present invention satisfies this goal through the
design of the inflatable devices to be described.
[0073] The present invention discloses improved systems for
deployment in bone comprising structures adapted to assume expanded
geometries having a desired configuration when used. These
expandable structures include material that allows the structure to
differentially expand when under internal pressure. These
structures, when in use, are able to expand preferentially along
one or more axes so as to deliver a greater force and/or
displacement of cancellous bone towards one direction versus
another. Furthermore, such structures, when distended, can
generally match the geometry of the interior bone space in which
the structure deployed, if desired. For example, such structures
could optimally expand to a desired shape rather than simply
towards areas of lowest bone density, i.e. expansion of the
structure is can be controlled even when encountering areas in the
bone of varying resistance.
[0074] Moreover, the exposure of the expandable structure to
cancellous bone also typically requires materials having
significant resistance to surface abrasion, puncture and/or tensile
stresses. For example, structures incorporating elastomer
materials, e.g., polyurethane, which have been preformed to a
desired shape, e.g., by exposure to heat and pressure, can undergo
controlled expansion and further distention in cancellous bone,
without failure, while exhibiting resistance to surface abrasion
and puncture when contacting cancellous bone.
[0075] The present invention further discloses inflatable devices
that have one or more biased directions of inflation. For example,
inflatable devices having reduced lateral growth may provide
improved fracture reduction because such devices can exert a
greater vertical force and/or displacement within the treated bone.
Such inflatable devices may also protect the lateral and
anterior/posterior sidewalls of the vertebral body by minimizing
expansion towards these sidewalls and directing expansion to a
greater degree along the longitudinal axis of the spine. In
situations where a surgical procedure is terminated when the
inflatable device contacts a lateral cortical wall of the targeted
bone, such biased expansion could permit improved fracture
reduction prior to reaching this procedure endpoint.
[0076] Due to the nature of the injury, disease or other
treatments, as well as the health and age of the patient suffering
from these injuries, it may be preferable to treat a bone with the
devices of this invention during an open or semi-open surgical
procedure. In addition, a goal of the surgery may be to replace the
diseased or injured bone with materials (such as bone fillers or
certain drugs) which do not flow, and which thus are not well
suited for a more minimally invasive procedure.
[0077] A. Balloons for Vertebral Bodies
[0078] A first embodiment of the balloon (FIG. 1) constructed in
accordance with the teachings of the present invention is broadly
denoted by the numeral 10 and includes a balloon body 11 having a
pair of hollow, inflatable parts 12 and 14 comprised of flexible
material, including (but not limited to) non-elastic materials such
as PET, mylar or Kevlara, elastic materials such as polyurethane,
latex or rubber, semi-elastic materials such as silicone, or other
materials. Parts 12 and 14 have a suction tube 16 therebetween for
drawing fats and other debris by suction into tube 16 for transfer
to a remote disposal location. Catheter 16 has one or more suction
holes so that suction may be applied to the open end of tube 16
from a suction source (not shown).
[0079] In this embodiment, the parts 12 and 14 are connected
together by an adhesive which can be of any suitable type for
adhering such materials as well as by bonding, i.e. thermal bonding
(laser, radio-frequency (RF)/induction, heated dies), ultrasonic
welding, solvent bonding, etc. Parts 12 and 14 are doughnut-shaped
as shown in FIG. 1 and have tubes 18 and 20 which communicate with
and extend away from the parts 12 and 14, respectively, to a source
of inflating fluid under pressure (not shown). The inflating fluid
is preferably a liquid. The liquid inflates the balloon 10,
particularly parts 12 and 14 thereof after the balloon has been
inserted in a collapsed condition (FIG. 8) into a bone to be
treated, such as a vertebral bone 22 in FIG. 2. The above-mentioned
U.S. Pat. Nos. 4,969,888 and 5,108,404, which are incorporated
herein by reference, disclose the use of a guide pin and cannula
for inserting the balloon into bone to be treated when the balloon
is deflated and has been inserted into a tube and driven by the
catheter into the cortical bone where the balloon is inflated.
[0080] FIG. 8 shows a deflated balloon 10 being inserted through a
cannula 26 into bone. The balloon in cannula 26 is deflated and is
forced through the cannula by exerting manual force on the catheter
21 which extends into a passage 28 extending into the interior of
the bone. The catheter is slightly flexible but is sufficiently
rigid to allow the balloon to be forced into the interior of the
bone where the balloon is then inflated by directing fluid into the
tube 88 whose outlet ends are coupled to respective parts 12 and
14.
[0081] In use, the balloon 10 is initially deflated and, after the
bone to be filled with the balloon has been prepared to receive the
balloon such as by punching, drilling or otherwise displacing a
small amount of the cancellous bone directly beyond the opening of
the cannula), the deflated balloon is advanced into the bone in a
collapsed condition through the cannula 26. (The bone is shown in
FIG. 2.) In this embodiment, the balloon is oriented preferably in
the bone such that the balloon expansion permits minimum pressure
to be exerted on the cortical bone if there were no fracture or
collapse of the bone. Where such fracture or collapse has not
occurred, such pressure would desirably compress the bone marrow
and/or cancellous bone against the inner wall of the cortical bone,
thereby compacting the bone marrow of the bone to be treated and to
further enlarge the cavity in which the bone marrow is to be
replaced by a biocompatible, flowable bone material.
[0082] The balloon is inflated to compact the bone marrow and/or
cancellous bone in the cavity and, after compaction of the bone
marrow and/or cancellous bone, the balloon is deflated and removed
from the cavity. While inflation of the balloon and compaction
occurs, fats and other debris may be removed from the space between
and around parts 12 and 14 by applying a suction force to catheter
tube 16, if desired. Following this, and following the compaction
of the bone marrow, the balloon is deflated and pulled out of the
cavity by applying a manual pulling force to the catheter tube
21.
[0083] Another embodiment of an inflatable device constructed in
accordance with the teachings of the present invention is broadly
denoted by the numeral 60 and is shown in FIGS. 4 and 5. The
balloon 60 includes a central spherical part 62 which is hollow and
which receives an inflating liquid under pressure through a tube
64. The spherical part is provided with a spherical outer surface
66 and has an outer periphery which is surrounded substantially by
a ring shaped part 68 having tube segments 70 for inflation of part
68. A pair of passages 69 interconnect parts 62 and 68. A suction
tube segment 72 draws liquid and debris from the bone cavity being
formed by the balloon 60.
[0084] Provision can be made for a balloon sleeve 71 for the
balloon 60 as well as for all balloons disclosed herein. A balloon
sleeve 71 (FIG. 9) is shiftably mounted in an outer tube 71a and
can be used to insert the balloon 60 when deflated into a cortical
bone. The sleeve 71 has resilient fingers 71b which bear against
the interior of the entrance opening 71c of the vertebral bone 22
(FIGS. 9A and 9B) to prevent rearing or bunching of the balloon 60.
Upon removal of the balloon sleeve, liquid under pressure will be
directed into the tube 64 which will inflate parts 62 and 68 so as
to compact the bone marrow within the cortical bone. Following
this, the balloon 60 is deflated and removed from the bone
cavity.
[0085] FIGS. 6 and 6A show views of a modified doughnut shape
balloon 80 of the type shown in FIGS. 1 and 2, with one difference
being the doughnut shapes of the balloon 80 are not stitched onto
one another. In FIG. 6, the balloon 80 has a pear-shaped outer
convex surface 82 which is made up of a first hollow part 84 and a
second hollow part 85. A tube 88 is provided for directing liquid
into the two parts along branches 90 and 92 to inflate the parts
after the parts have been inserted into the medullary cavity of a
bone. A catheter tube 16 is inserted into the space 96 between two
parts of the balloon 80. An adhesive bonds the two parts 84 and 85
together at the interface thereof.
[0086] FIG. 6A shows one way in which the catheter tube 16 is
inserted into the space or opening 96 between the two parts of the
balloon 80.
[0087] FIG. 7 shows the tube 88 of which, after directing inflating
liquid into the balloon 80, can inject contrast material into the
balloon 80 so that x-rays can be taken of the balloon with the
inflating material therewithin to determine the proper placement of
the balloon. Alternatively, the inflation liquid could comprise a
radiopaque inflation liquid, such as Conray.RTM. contrast medium
(commercially available from Mallinckrodt Inc. of St. Louis, Mo.),
such that inflation and visualization can be done currently,
allowing monitoring of the balloon position and condition during
the inflation step. Tube 16 is also shown in FIG. 6, it being
attached in some suitable manner to the outer side wall surface of
tube 88.
[0088] Still another embodiment of the invention is shown in FIG.
3, which is similar to FIG. 1 (although one difference it that it
is not a doughnut) and includes an inflatable device 109 having
three balloon units 110, 112 and 114 which are inflatable and which
have string-like restraints 117 which limit the expansion of the
balloon units in a direction transverse to the longitudinal axes of
the balloon units. If desired, the restraints can comprise the same
or a similar material as the balloon, or the restraints can
comprise a material having a reduced, little or no substantial
expansion capability.
[0089] A tube system 115 can be provided to direct liquid under
pressure into the balloon units 110, 112 and 114 so that liquid can
be used to inflate the balloon units when placed inside the bone in
a deflated state. Following the proper inflation and compaction of
the bone marrow, the balloon(s) can be removed by deflating it/them
and pulling it/them outwardly of the bone being treated. The
restraints desirably keep the opposed sides 77 and 79 substantially
flat and parallel with respect to each other.
[0090] In FIG. 10, another embodiment of the inflatable balloon is
shown. The device comprises a kidney shaped balloon body 130 having
a pair of opposed kidney shaped side walls 132 which are adapted to
be collapsed and to cooperate with a continuous end wall 134 so
that the balloon 130 can be forced into a bone 136 shown in FIG.
11. A tube 138 is used to direct inflating liquid into the balloon
to inflate the balloon and cause it to assume the dimensions and
location shown in the vertebral body 136 in FIG. 11. The balloon
130 will desirably compress the cancellous bone if there is no
fracture or collapse of the cortical bone. The restraints for this
action are principally due to the side and end walls of the
balloon.
[0091] FIG. 12 shows a balloon 140 which is also kidney shaped and
has a tube 142 for directing an inflatable liquid into the tube for
inflating the balloon. The balloon is initially formed in a single
chamber bladder but the bladder can subsequently be branded and/or
melted along curved lines or strips 141 to form attachment lines
144 which take the shape of side-by-side compartments 146 which are
kidney shaped as shown in FIG. 13. The branding desirably causes a
welding and/or bonding of the two sides of the bladder--the
material can be standard medical balloon material, which is
typically plastic that can be formed and/or bonded using heat.
[0092] FIG. 14 is a perspective view of a vertebral body 147
containing the balloon of FIG. 12, showing a double stacked balloon
140 when it is inserted in vertebral tone 147.
[0093] FIG. 15 is a view similar to FIG. 10 except that tufts 155,
which can be string-like restraints or other structures between the
opposing inner walls of the balloon, extend between and are
connected to the side walls 152 of the inflatable device 150 and
limit the expansion of the side walls with respect to each other.
In this embodiment, the tufts desirably render the side walls
generally parallel with each other. Of course, tufts which merely
limit and/or reduce the displacement between opposing walls of the
balloon will similarly accomplish various objectives of the present
invention to some degree. Tube 88 is used to fill the kidney shaped
balloon with an inflating liquid in the manner described above.
[0094] The dimensions for a vertebral body balloon can vary across
a broad range, depending upon the size, location, and condition of
the targeted vertebral body as well as the objectives of the
treatment. For example, the height (H, FIG. 11) of a vertebral body
balloon for both lumbar and thoracic vertebral bodies can typically
range from 0.5 cm to 3.5 cm. The anterior to posterior (A, FIG. 11)
vertebral body balloon dimensions for both lumbar and thoracic
vertebral bodies can typically range from 0.5 cm to 3.5 cm. The
side to side (L, FIG. 11) vertebral body dimensions from thoracic
vertebral bodies will often range from 0.5 cm to 3.5 cm. The side
to side vertebral body dimensions for lumbar vertebral bodies will
typically range from 0.5 cm to 5.0 cm. Of course, depending upon
the objectives of the treatment and the actual dimensions of the
patient's bones, the use of balloons having larger or smaller
dimension than these disclosed ranges may be appropriate.
[0095] The eventual selection of the appropriate balloon for, for
instance, a given vertebral body is based upon several factors. One
major factor affecting the choice of balloon size is the objectives
of the treatment. For example, if the principal treatment objective
is simply the repair and/or augmentation of a collapsed vertebral
body, then the appropriate balloon size (and desired cavity size)
may be a balloon which approximates the size of the interior of the
vertebral body in an unfractured and/or uncollapsed condition.
Alternatively, two or more balloons could be used concurrently
within a single vertebral body, which together create a desired
size cavity within the vertebral body. As another alternative, if
the objective of treatment is more localized within the bone, such
as the creation of a smaller cavity to augment and/or repair a
smaller section of the bone, then the use of a smaller balloon size
(and desired cavity size) may be desirous. Similarly, where the
cancellous bone is relatively strong and/or resistant to
compression, the use of a smaller balloon may be warranted to
accomplish the objective of displacing cortical bone (to reduce the
fracture) without significantly compressing the cancellous bone
(thus creating a smaller cavity). Moreover, smaller balloons may
also be suited for use in the treatment of bone tumors, etc., where
the balloon can be used to create a small cavity adjacent to the
tumor--this small cavity will simplify the use of other minimally
invasive tools to directly visualize the treatment area as well as
morselize and/or excise the tumor from the bone.
[0096] The anterior-posterior (A-P) balloon dimension is measured
from the internal cortical wall of the anterior cortex to the
internal cortical wall of the posterior cortex of the vertebral
body. In general, for augmentation and/or reinforcement of a
collapsed vertebral body, the appropriate A-P balloon dimension
will often be approximately 5 to 7 millimeters less than this
measurement.
[0097] The appropriate side to side balloon dimensions for a given
vertebral body is selected from the CT scan or from a plain film
x-ray view of the vertebral body to be treated. The side to side
distance can be measured from the internal cortical walls of the
side of the vertebral bone. In one embodiment, the appropriate side
to side balloon dimension may be 5 to 7 millimeters less than this
measurement. In alternate embodiments, the appropriate side to side
balloon dimensions may be significantly smaller, such as where
multiple balloons are introduced into a single vertebral body or
where the displacement of cortical bone is a primary objective of
the treatment. In general, lumbar vertebral bodies tend to be much
wider in their side to side dimension than in their A-P dimension.
In contrast, thoracic vertebral bodies are typically approximately
equal in their the side to side dimensions and their A-P
dimensions.
[0098] The height dimensions of the appropriate vertebral body
balloon for a given vertebral body may be chosen by the CT scan or
x-ray views of the vertebral bodies above and below the vertebral
body to be treated. The height of the vertebral bodies above and
below the vertebral body to be treated can be measured and
averaged. This average may be used to determine the appropriate
height dimension of the chosen vertebral body balloon. Of course,
as previously mentioned, various other balloon sizes may be
desirous based upon the objectives of the treatment, as well as the
actual patient's anatomy.
[0099] B. Balloons for Long Bones
[0100] Long bones which can be treated with the use of balloons of
the present invention include (but are not limited to) the distal
radius (larger arm bone at the wrist), the proximal tibial plateau
(leg bone just below the knee), the proximal humerus (upper end of
the arm at the shoulder), and the proximal femoral head (leg bone
in the hip).
[0101] C. Distal Radius Balloon
[0102] For the distal radius, one embodiment of a balloon 160 is
shown in the distal radius 152 has a shape which approximates a
pyramid but more closely can be considered the shape of a
humpbacked banana in that it substantially fills the interior of
the space of the distal radius to force cancellous bone 154 against
the inner surface 156 or cortical bone 158.
[0103] The balloon 160 has a lower, conical portion 159 which
extends downwardly into the hollow space of the distal radius 152,
and this conical portion 159 increases in cross section as a
central distal portion 161 is approached. The cross section of the
balloon 160 is shown at a central location (FIG. 17B) and this
location is near the widest location of the balloon. The upper end
of the balloon, denoted by the numeral 152, converges to the
catheter 88 for directing a liquid into the balloon for inflating
the same to compress the cancellous bone and/or force the
cancellous bone against the inner surface of the cortical bone. The
shape of the balloon 160 is desirably predetermined and can be
restrained by tufts formed by string restraints 165, as well as
various other types of restraints described herein. These
restraints are optional and provide additional strength to the
balloon body 160, but are not absolutely required to achieve the
desired configuration. The balloon is placed into and taken out of
the distal radius in the same manner as that described above with
respect to the vertebral bone.
[0104] The dimensions of the distal radius balloon vary as
follows:
[0105] The proximal end of the balloon (i.e. the part nearest the
elbow) is cylindrical in shape and will vary from 0.5'0.5 cm to
1.8'1.8 cm.
[0106] The length of the distal radius balloon will vary from 1.0
cm to 12.0 cm.
[0107] The widest medial to lateral dimension of the distal radius
balloon, which occurs at or near the distal radio-ulnar joint, will
measure from 1.0 cm to 2.5 cm.
[0108] The distal anterior-posterior dimension of the distal radius
balloon will vary from 0.5 cm to 3.0 cm.
[0109] In an alternate embodiment also suited for use in treating a
distal radius fracture, a balloon can take the shape of a toroidal
or disk-like shape, such as shown in FIGS. 25A-25C.
[0110] D. Proximal Humerus Fracture Balloon
[0111] The selection of the appropriate balloon size to treat a
given fracture of the distal radius will often depend on the
radiological size of the distal radius and the location of the
fracture, as well as the treatment goals.
[0112] In the case of the proximal humerus 169, one embodiment of a
balloon 166 shown in FIG. 18 is spherical and has a base design. It
can optimally compact the cancellous bone 168 in a proximal humerus
169. A mesh 170, embedded, laminated and/or wound, may be used to
form a neck 172 on the balloon 166, and a second mesh 170a may be
used to conform the bottom of the base 172a to the share of the
inner cortical wall at the start of the shaft. These restraints
provide additional strength to the balloon body, but the
configuration can be achieved through various methods, including
molding of the balloon body or various other restraints described
herein. This embodiment desirably compresses the cancellous bone to
create a compacted region surrounding the balloon 166 as shown in
FIG. 18. The cortical bone 173 is desirably relatively wide at the
base 174 and is thin-walled at the upper end 175. The balloon 166
has a feed tube 177 into which liquid under pressure is forced into
the balloon to inflate it to compact tae cancellous bone in the
proximal humerus. The balloon is inserted into and taken out of the
proximal humerus in the same manner as that described above with
respect to the vertebral bone.
[0113] In this embodiment, the dimensions of the proximal humerus
fracture balloon vary as follows:
[0114] The spherical end of the balloon will vary from 1.0'1.0 cm
to 3.0'3.0 cm.
[0115] The neck of the proximal humeral fracture balloon will vary
from 0.8'0.8 cm to 3.0'3.0 cm.
[0116] The width of the base portion or distal portion of the
proximal humeral fracture balloon will vary from 0.5'0.5 cm to
2.5'2.5 cm.
[0117] The length of the balloon will vary from 4.0 cm to 14.0
cm.
[0118] The selection of the appropriate balloon to treat a given
proximal humeral fracture depends on the radiologic site of the
proximal humerus and the location of the fracture as well as the
treatment goals.
[0119] E. Proximal Tibial Plateau Fracture Balloon
[0120] The tibial fracture is shown in FIG. 19A in which one
embodiment of a balloon 180 is placed in one side 182 of a tibia
183. Desirably, the balloon, when inflated, compacts the cancellous
bone in the layer 184 surrounding the balloon 180. A cross section
of this embodiment of a balloon is shown in FIG. 19C wherein the
balloon has a pair of opposed sides 185 and 187 which are
interconnected by restraints 188 which can be in the form of
strings or flexible members of any suitable construction. In this
embodiment, the restraints desirably maintain the sides 185 and 187
substantially parallel with each other and non-spherical. A tube
190 is coupled to the balloon 180 to direct inflation liquid into
and out of the balloon. The ends of the restraints are shown in
FIGS. 19B and 19D and denoted by the numeral 191. The balloon is
inserted into and taken out of the tibia in the same manner as that
described above with respect to the vertebral bone. FIG. 19B shows
a substantially circular configuration for the balloon; whereas,
FIG. 19D shows a substantially elliptical version of the
balloon.
[0121] The dimensions of this embodiment of a proximal tibial
plateau fracture balloon vary as follows:
[0122] The thickness or height of the balloon will vary from 0.5 cm
to 5.0 cm.
[0123] The anterior-posterior (front to back) dimension will vary
from 1.0 cm to 6.0 cm.
[0124] The side to side (medial to lateral) dimension will vary
from 1.0 cm to 6.0 cm.
[0125] The selection of the appropriate balloon to treat a given
tibial plateau fracture will depend on the radiological size of the
proximal tibial and the location of the fracture, as well as the
treatment goals.
[0126] F. Femoral Head Balloon
[0127] In the case of the femoral head, one embodiment of a balloon
200 is shown as having been inserted inside the cortical bone 202
of the femoral head which is thin at the outer end 204 of the femur
and which can increase in thickness at the lower end 206 of the
femur. The cortical bone surrounds the cancellous bone 207 and this
bone is desirably compacted by the inflation of the balloon 200.
The tube for directing liquid for inflation purposes into the
balloon is denoted by the numeral 209. It extends along the femoral
neck and is directed into the femoral had which is generally
spherical in configuration. FIG. 20A shows that the balloon,
denoted by the numeral 200a, can be hemispherical as well as
spherical, as shown in FIG. 20. The balloon 200 is inserted into
and taken out of the femoral head in the same manner as that
described with respect to the vertebral bone. The hemispherical
shape is maintained in this example by bonding overlapping portions
of the bottom, creating pleats 200b as shown in FIG. 20A.
[0128] The dimensions of the femoral head balloon may vary as
follows--the diameter of the femoral head balloon will vary from
1.0 cm to up to 4.5 cm or greater. The appropriate size of the
femoral head balloon to be chosen depends on the radiological or CT
scan size of the head of the femur and the location and size of the
avascular necrotic bone. The dimensions of the hemispherical
balloon are similar to those of the spherical balloon, except that
approximately one half of the balloon is provided.
[0129] G. Prevention of Hip Fracture
[0130] FIG. 21 illustrates one embodiment of a "boomerang" balloon
210 adapted for preventing and/or treating hip fracture. When
inflated, the "boomerang" balloon 210 is a cylinder which gradually
bends in the middle, like a boomerang, and extends from about 0.5
cm from the end of the femoral head 211 through the femoral neck
212 and down into the proximal femoral diaphysis 213 about 5-7 cm
past the lesser trochanter 214. This embodiment of a balloon 210
preferably maintains its shape by rings of inelastic material (215
is one of them) held closer together on one side by attachment to a
shorter inelastic band 216 running the length of the side of
balloon and further apart by attachment to a longer inelastic band
217 bonded on the opposite side, although various other restraints
disclosed herein would also suffice.
[0131] After and prior to inflation, the balloon 210 may be folded
back (shown in dotted lines at 218) against the inflation tube 219.
Prior to inflation the balloon 210 can also be rolled up and held
against the inflation tube with loose attachments that break when
the balloon is inflated. To insert the balloon on its inflation
tube into the hip, the surgeon can use a power drill under
radiographic guidance to create a cavity 220 that is usually 4-6 mm
wide starting at the lateral femoral cortex 221 and proceeding into
the femoral head 211. Inflation of the balloon 210 into the greater
trochanteric region 222 instead of down the femoral diaphysis 213
is less desirable and is typically avoided by proper choices in the
shape of the balloon as well as by its placement and correct
orientation the deflated balloon desirably facing the lesser
trochanter). After the balloon 210 has been inflated within the
cavity 220 (see the dotted lines in FIG. 21), the predetermined
size and shape of the balloon biases the proximal portion of the
balloon downward into the lesser trochanter. Optionally, a second
cavity can be drilled down into the diaphysis, starting from the
same entry point or from the other side.
[0132] Patients with bone density in the hip below a threshold
value are at increased risk of hip fracture, and lower densities
create greater risk. Patient selection may be done through a bone
density scan or other methods of determining bone quality well
known in the art. Such selection could also result from a previous
and/or concurrent fracture of the other hip, or some other type
and/or location of osteoporotic fracture. The balloon length can be
chosen by the surgeon to extend about 0.5 cm from the end of the
femoral head, through the femoral neck and into the proximal
femoral diaphysis, usually about 4-8 cm below the lesser
trochanter. The balloon diameter can be chosen by measuring the
inner cortical diameter of the femoral neck (the most narrow area)
and subtracting 0.5 cm. The preferred dimensions of the "boomerang"
balloon are a total length of 10-20 cm and a diameter of 1.0-2.5
cm. (A "humpback banana" balloon with appropriate length may also
be useful in hip fracture prevention, where the "humpback" width
does not exceed the desired femoral neck dimensions.)
[0133] Patients having the lowest bone densities in the femoral
head may require greater compacting in the femoral head, which may,
for example, be provided by using two balloons, one after the
other: the "boomerang" followed by the femoral head balloon
(inserted at the same point and expanded prior to inserting any
supporting material.) Alternatively, the "boomerang" balloon may be
adapted to have a distal portion that approximates the shape of the
femoral head balloon.
[0134] The various balloons described herein could also be used in
conjunction with the replacement of various structures within human
and animal bodies. For example, the balloons described herein could
be used to compress cancellous bone in a femur in preparation for
the implantation of an artificial hip stem. Similarly, the balloons
described herein could be used in conjunction with various other
joint replacement procedures, including artificial knee and ankle
joints.
[0135] H. All Balloons
[0136] It should be understood that the various embodiments of
balloons disclosed herein are by no means limited in their utility
to use in a single treatment location within the body. Rather,
while each embodiment may be disclosed in connection with an
exemplary treatment location, these embodiments can be utilized in
various locations within the human body, depending upon the
treatment goals as well as the anatomy of the targeted bone. For
example, the embodiment of a balloon previously disclosed as useful
in treating a fracture of the distal radius could similarly be used
in the treatment of fractures in various other areas within the
body, including but not limited to fractures and/or impending
fractures of the femur, the radius, the ulna, the tibia, the
humerus, the calcaneus or the spine. Similarly, the various other
disclosed embodiments can be utilized throughout the body, with
varying results depending upon treatment goals and/or the anatomy
of the targeted bone.
II. The Inflatable Device
[0137] A. Complex Expandable Structures
[0138] Sometimes it can be difficult to achieve a desired
uniformity and area of compaction within a given cancellous bone
region using an expandable body having a single expansion region.
FIG. 27 shows a complex preformed structure 280 which includes
expanded segmented regions 282 and 284 spaced along its length. The
structure 280 provides a longer profile along which volume can be
increased.
[0139] The complex expandable structure is created by extruding or
molding a tube 286 of polyurethane plastic or other elastomer
material. In a preferred embodiment, the tube is comprised of
polyurethane plastic material. The tube has a normal extruded wall
thickness (T5) and a normal extruded outside diameter (D5) (as
shown in FIG. 27).
[0140] The segmented shaped regions 282 and 284 are created by
exposing an intermediate region of the tube to heat, positive
interior pressure and/or stretching inside a fixture or mold (not
shown). In one embodiment, the fixture could possess two cavity
regions separated by a reduced diameter region or intermediate
channel. The cavity regions and the channel can be exposed to a
source of heat, to soften the material of the region. When
heat-softened (in the manner previously described), the interior of
the tube 286 is stretched and subjected to positive pressure from a
source. The material in the region 288 will desirably expand or
extend within the cavities and the channel.
[0141] Once cooled and removed from the fixture, the structure 280
can be attached to the distal end of an outer catheter tube 250.
(See FIG. 28.) The structure of the outer catheter tube 250 (as
well as the inner catheter tube 258) can vary, and the outer
catheter tube 250 can comprise various flexible materials,
including medical grade plastic materials like vinyl,
polyethylenes, ionomer, polyurethane, and polytetrapthalate (PET)
as well as less flexible materials such as Kevlar.RTM., PEBAX.TM.,
stainless steel, nickel-titanium alloys, and other metals and/or
ceramics. The outer catheter tube 250 desirably incorporates an
interior bore 260, into which an inner catheter tube 258 extends.
It should be appreciated that the outer catheter tube 250 can have
one or more interior lumens. In the illustrated embodiment, the
inner catheter tube 258 extends through the interior bore 260 and
beyond the distal end 254 of the catheter tube 250. A distal end
region of the structure 280 is secured to the to the distal end
region 254 of the outer catheter tube 250, while a proximal end
region of the structure 280 is secured to the distal end region 262
of the inner catheter tube 258. The end regions can be secured,
e.g., using adhesive or thermal bonding, etc.
[0142] The structure 280 possesses, in an open air environment, a
normal expanded shape, having diameter D7 (shown in phantom lines
of FIG. 27). The normal shape and diameter D7 for the regions 282
and 284 generally correspond with the shape and dimension of the
cavities, respectively.
[0143] When an interior vacuum is drawn, removing air and/or fluid
from the structure 280, the structure 280 assumes a substantially
collapsed, and not inflated, geometry, shown as lines D6 in FIG.
27. Due to the application of heat and pressure upon the
intermediate region 288, the diameter D6 for each region 282 and
284 is larger than the normally extruded or molded outside diameter
D5 of the original extruded tube.
[0144] The regions 282 and 284 are separated by a tubular neck 298,
which segments the structure 280 into two expandable regions 282
and 284. When substantially collapsed under vacuum or not inflated,
the structure 280 exhibits a low profile, ideal for the insertion
into and/or removal from the targeted cancellous bone region.
[0145] The introduction of fluid volume back into the tube 286 will
cause each region 282 and 284 to return from the collapsed diameter
D6 to the normal, enlarged, but not distended, geometry, having the
shape and diameter shown in phantom lines D7 in FIG. 27.
[0146] In the illustrated embodiment, the first and second shaped
regions 282 and 284 have generally the same radius of expansion and
thus the same non-distended shape and diameter D7. Alternatively,
each region 282 and 284 can have a different radius of expansion,
and thus a different-non-distended shape and diameter. Regardless,
when in the normal, non-distended diameter D7, the material of the
structure 280 in the region 288 is not significantly stretched or
stressed, because the regions 282 and 284 have been expanded in a
stress-relieved condition into these geometries in the
cavities.
[0147] As before explained in conjunction with the structure, the
regions 282 and 284 can be shaped by heat and/or interior pressure
within different cavities to assume different geometry's, e.g.,
cylindrical or elliptical geometry, or a non-spherical,
non-cylindrical, or non-elliptical geometry, with either uniform or
complex curvature, and in either symmetric or asymmetric forms. Of
course, more than two segmented regions 282 and 284 can be formed
along the length of the tube. In addition, the normally expanded
shape characteristics of the structure can be achieved by other
techniques. For example, and not by way of limitation, the
structure can be formed by dipping, lost wax casting, or injection
molding.
[0148] Each shaped region 282 and 284 possesses a minimum wall
thickness (designated T7 in FIG. 27) when in the normally enlarged
but not distended geometry D7. Due to expansion of heat-softened
material under pressure in the cavities, the wall thickness is not
uniform, i.e., T7 is less than the normal extruded or molded wall
thickness 75 of the tube. The minimum wall thickness T7 for the
regions 282 and 284 can be the same or different.
[0149] When in the enlarged, but not distended geometry, the neck
region 298 has an outside diameter (designated D9 in FIG. 27),
which is equal to or greater than the normal extruded or molded
diameter D5 of the tube. The size of the channel in the fixture
determines the magnitude of the diameter D9. Due to expansion of
heat-softened material in the adjacent regions 282 and 284 under
pressure in the cavities, the neck region 298 (which expands under
pressure in the channel) has a wall thickness (designated T9 in
FIG. 27) which is less than or equal to the normal extruded or
molded wall thickness T5 of the tube 285, but still greater than
the minimum wall thickness r7 of either fully shaped region 282 or
284.
[0150] The formed complex structure 280 thus possesses regions of
non-uniform minimum wall thickness along its length; that is,
T5.gtoreq.T9.gtoreq.T7. The formed complex structure 280 also
provides multiple expandable regions 282 and 284 of the same or
different enlarged outside diameters D7), segmented by a neck
region 298, in which D6>D5; D7>D6; and D7>D9.
[0151] By continuing to apply fluid volume at a constant pressure
at a threshold amount P(t), and thereby increasing the volume
within the structure 280, the shaped regions 282 and 284 of the
structure 280 will continue to enlarge beyond diameter D7 to a
distended shape and geometry, designated D8 in FIG. 27. The wall
thickness T7 further decreases and approaches T8. As the regions
282 and 284 approach diameter D8, the diameter D9 of the neck
region 298 will likewise increase toward diameter D10, as FIG. 27
shows, providing more uniform, elongated surface contact with
cancellous bone.
[0152] Enlargement of the structure 280 beyond diameter D7
stretches the material in the regions 282, 284 and 298 beyond their
stress-relieved condition, although the distended geometry of the
regions 282 and 284 will, in important respects, maintain the
preformed shape dictated by the cavities.
[0153] The degree of stretching at a substantially constant
incremental pressure condition car be tailored to achieve a
desired, fully distended diameter D8. The final, fully distended
diameter D8 can be selected to match the dimensions of the targeted
cancellous bone region. The controlled stretching of the segmented
regions 282 and 284 in tandem can provide an equal volume
compression of cancellous bone with a major diameter that is less
than a single non-segmented region (i.e., one without the neck
region 298). Stated another way, segmented regions 282 and 284,
when expanded to a given inflation volume, have a diameter less
than a sphere expanded to an equal inflation volume.
[0154] While expanding in the region between D7 and 08, the
structure 280, when inside bone, assumes an increasingly larger
surface area and volume, thereby compacting surrounding cancellous
bone. Inflation in cancellous bone may occur at the same threshold
pressure P(t) as outside bone. However, an increase in the
threshold pressure P(t) inside bone is typically required, due to
the density of the cancellous bone and resistance of the cancellous
bone to compaction.
[0155] B. Assembly of an Expandable Balloon Device with an Internal
Membrane
[0156] FIGS. 23 and 24A-24C depict cross-sectional views of another
alternate embodiment of a cavity-forming device constructed in
accordance with the teachings of the present invention. Because
many of the features of this embodiment are similar to those
described in connection with the previous embodiment, like
reference numerals will be used to describe similar components.
[0157] In this embodiment the cavity-forming device incorporates a
balloon 300 comprising a section of dual lumen tubing having an
outer wall 310 and an internal membrane 320. The balloon 300 will
desirably comprises a material that is commonly used for balloon
catheters including, but not limited to, polyethylene, mylar,
rubber or polyurethane. Even more desirably, the balloon 300 will
comprise an elastomer material, which also possess the capability
of being preformed, i.e., to acquire a desired shape by exposure,
e.g., to heat and pressure, e.g., through the use of conventional
thermoforming, blow molding and/or dip coating techniques.
Candidate materials that meet this criteria include polyurethane,
silicone, thermoplastic rubber, nylon, and thermoplastic elastomer
materials.
[0158] In the illustrated embodiment, the balloon 300 comprises
TEXIN.RTM. 5290 polyurethane plastic material (commercially
available from Bayer Corp.). This material can be processed and
extruded in a tubular shape, which can then be cut into individual
lengths for further processing. The balloon 300 can be formed by
exposing a cut tube length to heat and then enclosing the heated
tube within a mold while positive interior pressure is applied to
the tube length. For example, one embodiment of a balloon can be
formed by heating a length of extruded tubing (incorporating an
internal membrane 320) to 320.degree. F. for approximately 220
seconds, and then stretching the tubing by 10 mm while the tubing
is blown at 100 psi in a mold for 45 seconds. The mold can of
course be part of a conventional balloon forming machine
[0159] In the present embodiment, after the balloon is formed the
proximal end of the balloon 300 can be attached to the distal end
of an outer catheter body 250 and the distal end of the balloon 300
can be attached to the distal end of an inner catheter body 258.
The outer and inner catheters may each comprise extruded tubing
made, e.g., from TEXIN.RTM. polyurethane plastic material, and each
can extruded in a tubular shape using, e.g., a screw type extrusion
machine, with a GENCA.TM. head, using suitable screens.
[0160] In assembling the cavity-forming device, the proximal end of
the balloon 300 is desirably bonded to the distal end of an outer
catheter body 250, as FIG. 26A shows. In one preferred embodiment
(as FIG. 26B shows), a razor blade or other cutting instrument can
be used to split approximately 5 mm of the distal end of the outer
catheter body 250, creating a pair of slots 360, as best shown by
"A" in FIG. 26B. The proximal end of the balloon 300 can then be
slid over the distal end of the outer catheter body 250. with the
outer wall 310 positioned around the distal tip of the outer
catheter body 250 and the internal membrane 320 positioned within
the slots 360 (as FIG. 26C shows). To maintain the flow channels
(for the inflation fluid) through the outer catheter body 250 and
into the balloon 300, a pair of mandrels or inserts (not shown) can
be introduced into the outer catheter body and balloon in a manner
well known in the art. The distal end of the outer catheter body
250 and the proximal end of the balloon 300 can then be bonded
together using various means including heat bonding, adhesives, or
the like. After the bond is formed, the mandrels can be removed.
Desirably, the splitting of the outer catheter body 250 increases
the mechanical strength of the bond between the catheter body 250
and the balloon 300 and permits the balloon to be more securely
bonded to the outer catheter body 250, reducing the opportunity for
a proximal bond failure of the balloon 300.
[0161] The distal end of the balloon 300 is also bonded to the
distal end of an inner catheter body 258. If desired, the distal
end of the inner catheter body 258 may be split in a similar manner
to increase the mechanical strength of the distal bond. Desirably,
the inner catheter body 258 will extend through the outer catheter
body 250 and the balloon 300 along one side the internal membrane
320.
[0162] As FIG. 26A shows, the proximal end of the outer catheter
body 250 can be secured to a distal end of a y-shaped luer fitting
400. The inner catheter body 258 desirably extends through an inner
lumen of the luer fitting 400, and may be bonded to a proximal end
of the fitting 400. Desirably, an inflation fitting 402 of the
y-shaped luer fitting 400 will be in fluid communication with the
lumen 404 (see FIG. 26C) formed between the inner and outer
catheter bodies 250 and 258, which will in turn be in fluid
communication with the interior of the balloon 300, such that an
inflation fluid introduced into the inflation fitting 402 will
inflate the balloon 300.
[0163] Desirably (as FIGS. 26A to 26C show), the outer catheter
body 250 and/or y-shaped luer fitting 400 will incorporate a marker
406 or other externally viewable indicia which shows a physician
the orientation of the internal membrane 320 when the balloon 300
is in a desired position within the patient. Such indicia could
include colored markers or stripes 406, indentations and/or
protrusions on the outer catheter body 250 or y-shaped luer fitting
400 as well as the orientation of the luer fitting itself. By
utilizing such indicia 406, the physician can easily rotate the
balloon 300 to a desired orientation within the vertebral body.
Because the materials used in constructing medical balloons are
typically radio-lucent, it would be difficult to gage the
orientation of the internal membrane 320 once the balloon 300 is in
position within the targeted bone. Alternatively, or in combination
with external indicia 406, the internal membrane 320 could
incorporate one or more marker bands or other radiopaque substances
408 (see FIG. 26C) to depict the orientation of the membrane 320
within the targeted vertebral body.
[0164] Various materials can be selected for the component parts of
the cavity-forming device. Furthermore, the dimensions of the
component parts of the cavity-forming device can also vary,
according to its intended use. It should also be understood that,
while one described embodiment incorporates dual lumen tubing,
various other embodiments could incorporate other types of
multi-lumen tubing (including, but not limited to triple,
quadruple, etc., lumen tubing), as well as could incorporate
membrane(s) having varying orientations and/or positions within the
tubing (e.g., symmetrical or asymmetrical).
[0165] The following table lists preferred component materials and
dimensions, which are well suited for a cavity-forming device
(incorporating dual lumen tubing) that can be deployed for use in a
vertebral body:
TABLE-US-00001 Component Material Dimension Outer catheter
Polyurethane Outside Diameter: 0.124'' body Plastic Inside
Diameter: 0.102'' Inner catheter Polyurethane Outside Diameter:
0.035'' body Plastic Inside Diameter: 0.025'' Expandable Structure:
Extruded Tubing: Polyurethane Outer Diameter: 0.164'' Plastic Outer
Wall Thickness: 0.028'' Membrane Thickness: 0.030'' Longitudinal
Length of Balloon 0.600'' to 0.949''
[0166] C. Exemplary Performance Features of the Expandable
Balloon
[0167] FIGS. 24A, 248 and 24C show cross-sectional views of the
previously-described embodiment of a balloon 300 during its
deployment in air. Desirably, the balloon 300 will expand in a
similar fashion within the targeted bone such as a vertebral
body.
[0168] FIG. 24A depicts a cross-sectional view of the balloon 300
when filled with a small amount of inflation fluid, such that the
balloon desirably assumes the approximate size and shape of the
mold in which the balloon was previously formed, with minimal
stresses experienced by the internal membrane 320. In this
condition, the expansion of the balloon is substantially circular
in cross-section. Accordingly, the vertical and horizontal
dimensions of the cross-section of the expanded balloon 300 are
approximately equal, or DX1=DY1.
[0169] FIG. 24B depicts the balloon 200 of FIG. 24A when further
filled with a pressurized inflation fluid. In this figure, the
balloon 300 has assumed a further distended shape, with the wall
material of the balloon 300 typically undergoing elastic and/or
plastic deformation to assume this enlarged geometry. The balloon
300 desirably does not assume a completely circular cross-sectional
shape, principally because the internal membrane resists lateral
expansion of the outer walls 310. While some elongation of the
internal membrane 320 typically occurs (due to elastic and/or
plastic deformation of the membrane), the resulting cross-sectional
shape is generally ovoid or somewhat similar to a figure-8. The
balloon 300, however, is not as significantly restrained from
growing in the vertical direction. This combination of restraints
results in a balloon which substantially expands or grows more in
the vertical direction than in the horizontal direction.
Accordingly, the vertical dimension of the expanded balloon 300 is
larger than the horizontal dimension of the balloon 300, or
DX2>DY2.
[0170] FIG. 24C depicts the balloon 300 of FIGS. 24A and 248 when
further filled with a pressurized inflation liquid. In this figure,
the balloon 300 has assumed an even more distended shape, with the
wall material typically having undergone both elastic and
significant plastic deformation in order to assume this enlarged
geometry. At this point, the balloon 300 is clearly in a
non-circular shape, with the internal membrane 320 significantly
resisting lateral growth of the balloon (although some additional
elastic stretching and/or plastic deformation of the membrane 320
has likely occurred). Accordingly, the vertical dimension of the
expanded balloon 300 is significantly larger than the horizontal
dimension of the balloon 300, or DX3>>DY3.
[0171] For the above-described embodiment, an experimental
inflation of the balloon with inflation fluid with volumes of 0 cc
to 2 cc and 2 cc to 4 cc produced the following results:
0 cc
[0172] Balloon Minor diameter (DX1-width): 7.7 mm [0173] Balloon
Major diameter (DY1-height): 7.7 mm
Inflation to 2 cc (Fluid)
[0173] [0174] Balloon Minor diameter (DX2-width): 9.2 mm [0175]
Increase in minor (horizontal) diameter: 1.5 mm (width)-(19.5%
total increase) [0176] Balloon Major diameter (DY2-height): 10.9 mm
[0177] Increase in major (vertical) diameter: 2.2 mm
(height)-(28.6% total increase)
Inflation to 4 cc (Fluid)
[0177] [0178] Balloon Minor diameter (DX3-width): 12.7 mm [0179]
Increase in minor (horizontal) diameter: 5 mm (width)-(65% total
increase) [0180] Balloon Major diameter (DY3-height): 15.4 mm
[0181] Increase in major (vertical) diameter: 7.7 mm (height)-(100%
total increase)
[0182] In addition to axial growth of the balloon 300 as the
balloon expands (as previously described), the longitudinal length
of a balloon also tends to increase during inflation. This is
because the stresses experienced by the balloon material are
typically acting in more than one dimension (resulting in material
deformation along more than a single axis), causing the overall
longitudinal length of the balloon 300 to expand in response to the
increased internal pressure. In the present embodiment, however,
the internal membrane 320 also tends to reduce the longitudinal
growth of the balloon during inflation. For example, for the
previously described embodiment of a balloon 300, a volumetric
increase from 2 cc to 4 cc results in a longitudinal length
increase for the balloon of only 27.1%. For a similarly constructed
balloon that does not incorporate an interior membrane, a
volumetric increase from 2 cc to 4 cc results in a longitudinal
length increase of 37.1%. Accordingly, the interior membrane 320 of
the present invention restrains not only certain aspects of
circumferential expansion, but also restrains aspects of
longitudinal expansion as well.
[0183] The internal membrane 320 of the present embodiment also
significantly reduces the opportunity for the balloon 300 to
experience a complete radial failure and/or fragment within the
patient. During a surgical procedure, if the balloon is punctured
or torn, the balloon failure may propagate through a significant
amount of the balloon material. If this failure propagates around
the entire radius of the balloon, then the distal section of the
balloon is in danger of becoming completely separated from the
proximal end of the balloon, with only the inner catheter, body 258
connecting the distal section of the balloon to the cavity-forming
device. In such a case, upon removal of the cavity forming device
from the patient, it is possible for the inner catheter body 258 to
fail, leaving the distal section and any balloon fragments in the
patient.
[0184] The internal membrane 320 of the present embodiment
desirably reduces any opportunity for a complete radial failure of
the balloon 300, and also significantly reduces the opportunity for
balloon fragments to separate from the cavity-forming device where
the interior membrane 320 joins the expandable wall, the geometry
and/or additional thickness of balloon material at this junction
410 (see FIG. 26C) significantly increases the balloon's resistance
to fracture at his location. A fracture which propagates towards
such a junction 410 will typically be redirected by the
junction--typically the fracture will either terminate, will
rebound from the junction and/or will be redirected along the
junction.
[0185] In the disclosed embodiment, a radial fracture which
propagates towards the junction 410 will generally be redirected
towards the longitudinal axis of the balloon 300. Moreover, the
interior membrane 320 serves to connect the proximal and distal
ends of the balloon 300, which will reinforce the inner catheter
body 258 in the unlikely event of a complete radial failure of the
balloon. Accordingly, because the present embodiment incorporates
at least two longitudinally extending junctions (i.e., the internal
membrane 320 of the balloon 300 and the inner catheter body 258 to
which the distal end of the balloon 300 is secured), a fracture of
this embodiment is unlikely to result in a complete radial tear of
the balloon material and/or fragmentation of the cavity forming
device.
III. Implant Creation and Performance
[0186] Once the balloon 300 is in a desired position within a
targeted bone (in this example a vertebral body), an inflation
medium can be introduced into the balloon, which desirably expands
the balloon within the targeted bone. The balloon will desirably
assume a similar shape within the targeted bone as it would in air,
thereby creating a cavity within the bone that is substantially the
same shape and size as the inflated balloon. It must be understood,
however, that variations in cancellous bone density and quality may
distort the final expanded size and shape of the inflated balloon,
such that the expanded balloon may be significantly different in
size and shape than it would be when expanded in air.
[0187] While the restraints described herein may not absolutely
guarantee that the final shape and size of the balloon (and thus
the cavity) will be identical to the shape and size of the balloon
in air, the restraints described herein significantly increase the
potential for creating an optimally sized and shaped cavity to
achieve one or more desired treatment goals. For example, if the
desired treatment goal is the reinforcement and/or repair of a
targeted vertebral body, a balloon may be chosen that incorporates
restraints to maximize vertical growth of the balloon (in this
context, the vertical orientation can be assumed to be parallel to
the longitudinal axis of the spine) while minimizing horizontal
and/or longitudinal growth of the balloon. If desired, this balloon
could also incorporate restraints that reduce and/or minimize
balloon expansion along its longitudinal axis.
[0188] Alternatively, a physician may desire a balloon that
incorporates restraints to maximize horizontal growth of the
balloon (in this context, horizontal growth can be assumed to be
transverse to the longitudinal axis of the spine) while minimizing
vertical growth of the balloon. Such a balloon (which could simply
be the previously described embodiment when rotated 90.degree.
about its longitudinal axis) could be used to initially create a
cavity extending across substantially the entire vertebral body.
After removal of the first balloon, a second balloon (of the same
or different design) could subsequently be introduced into the
horizontal cavity and expanded. If desired, the second balloon
could substantially fill the horizontal cavity prior to inflation
(thereby maximizing the surface area of the balloon facing the
upper and lower endplates) and, when expanded, could maximize the
vertical forces which ultimately act on the endplates of the
vertebral body (in an attempt to displace the surrounding cortical
bone).
[0189] If desired, a balloon chosen for treatment of a vertebral
body may further incorporate restraints that cause the balloon to
expand into an irregular shape. In one embodiment disclosed herein,
best shown in FIG. 23, the balloon desirably expands to a
"peanut-like" shape when viewed from the side. This embodiment will
desirably create a cavity that is similarly "peanut-shaped", with
the cavity essentially comprising a pair of enlarged cavity lobes
that are separated by a region of reduced cavity size--in other
words, the cavity is dumb-bell shaped. Desirably, the filler
material which occupies this cavity will harden, set and/or
solidify into an implant having substantially the shape of the
cavity into which it was introduced. By forming the implant into
this dumb-bell shape, the region of reduced width of the implant
will desirably help to anchor the implant within the cancellous
bone, thereby reducing the opportunity for the implant to displace
along the longitudinal axis of the implant and/or migrate within or
outside the treated bone.
[0190] Furthermore, if desired a balloon used for treatment of a
vertebral body could incorporate additional restraints that alter
the outer shape of the expanded balloon to further reduce the
opportunity and/or tendency of an implant to migrate within and/or
outside of a treated bone. For example, in one embodiment described
above, the balloon incorporates an internal membrane which
desirably causes the expanded balloon to assume an indented or
elongated "figure-8" shape in cross-section (see FIG. 24c). This
shape, if formed into the cavity walls and ultimately assumed by
the filler material, will desirably create an implant of similar
cross-section. By forming the implant into this figure-8 shape, the
implant will desirably be anchored within the cancellous bone,
thereby reducing the opportunity for the implant to rotate about
the longitudinal axis of the implant and/or migrate within or
outside the treated bone.
[0191] In addition to creating a desired shape and size to the
cavity, which will desirably act as a mold to bound and shape the
filler material, the physician can further customize the shape of
the implant in various ways. For example, after the initial cavity
formation, but prior to the introduction of the filler material,
the physician could use other surgical instruments to alter the
shape and/or size of the cavity, such as by removing additional
cancellous bone and/or scoring the compressed cancellous bone along
the walls of the cavity. Similarly, prior to introducing the filler
material the physician could introduce one or more additional
balloons into the cavity to alter the existing cavity dimensions
and/or create additional cavities of unique and/or desired shape.
The physician could alternatively choose to introduce two or more
different bone filler materials into a single cavity, with
different materials occupying different portions of the cavity
and/or being intertwined, mixed or separated in some manner, if
desired. In addition, after the filler material has filled the
entire cavity, the physician could continue introducing an
additional amount of bone filler material, which would desirably
cause small amounts of the bone filler material to interdigitate or
flow into various gaps and/or cracks in the walls of the cavity,
thereby further anchoring the resulting implant within the
cancellous bone. For example, the injection of an additional 1/2
cc, 1 cc or 11/2 cc of bone filler material (beyond the volume of
the cavity created within the cancellous bone) can significantly
increase the interdigitation of bone filler material with the
surrounding cancellous bone matrix.
IV. Other Uses, Methods and Balloons
[0192] The cavity created by the balloon can be filled with a
medically-appropriate formulation of a drug or a growth factor. As
an example of delivering a drug, a typical dose of the antibiotic,
gentamicin, to treat a local osteomyelitis (bone infection), is 1
gram (although the therapeutic range for gentamicin can be far
greater, from 1 nanogram to 100 grams, depending on the condition
being treated and the size of the area to be covered). A
medically-suitable gel formulated with appropriate gel materials,
such a polyethylene glycol, can contain 1 gram of gentamicin in a
set volume of gel, such as 10 cc. A balloon with this volume whose
shape and size is appropriate for the site being treated (that is,
the balloon desirably will not break the cortical bone when
inflated at the chosen site) can be used to compact the infected
cancellous bone. This creates a space that can be filled with the
antibiotic gel in an open or minimally invasive procedure. This
places and holds the required amount of drug right at the site
needing treatment, and protects the drug from being quickly washed
away by blood or other fluids. Not only can the dose be optimized,
but additional doses can be applied at later times without open
surgery, enhancing the therapeutic outcome. If the required cavity
for the optimal drug dose weakens the bone, the bone can be
protected from future fractures with a cast or with current
internal or external metal or plastic fixation devices. The
therapeutic substance put into bone may be acting outside the bone
as well. A formulation containing chemotherapeutic agent could be
used to treat local solid osteosarcoma or other tumor near that
bone.
[0193] As an alternative, to deliver therapeutic substances,
balloons can be dipped in a medical formulation (often a dry
powder, liquid or gel) containing a medically-effective amount of
any desired antibiotic, bone growth factor or other therapeutic
agent to coat the balloon with the above-mentioned substance before
it is inserted into a bone being treated. Optionally, the balloon
can be wholly or partially inflated with air or liquid before the
coating is performed. Optionally, the coated balloon can be dried
with air or by other means when the applied formulation is wet,
such as a liquid or a gel. The balloon is refolded as required and
either used immediately or stored, if appropriate and desired.
Coated on the balloon, therapeutic substances can be delivered
while cancellous bone is being compressed, or with an additional
balloon once the cavity is made.
[0194] The methods described above can also be used to coat
Gelfoam.RTM. absorbable gelatin powder or other agents onto the
balloon before use. Such agents may also comprise substances that
desirably promote coagulation and/or thickening of body fluids.
Inflating a Gelfoam-coated balloon inside bone may further fill any
cracks in fractured bone not already filled by the compressed
cancellous bone.
[0195] FIGS. 22A-C schematically illustrate one system and method
for delivering a therapeutic substance to the bone according to the
present invention. As shown in FIG. 22A, an inflated balloon 229
attached to an inflating tube 230 is stabilized with a clip 231
that couples tube 230 to a wire 232. As shown in FIG. 228, a
measured amount of gel formulation containing the desired amount of
substance 233 is uniformly dispensed from a container 234,
preferably in thin lines 235, onto the outer surface of a balloon
236. As shown in FIG. 22C, the coated balloon 23 is then deflated
and allowed to dry until the gel sets. The coated balloon 237 is
then ready for packaging for use by the surgeon. Of course, the
balloon can also be coated without prior inflation. In addition,
the coating substance can be the desired compound alone in its
natural state (solid, liquid or gas) or in an appropriate
formulation, including a dry powder, an aerosol or a solution. The
optional drying time will, of course, depend on the nature of the
compound and its formulation.
[0196] Delivering a therapeutic substance on the outside of the
balloon used to compact the bone or with a second (possibly
slightly larger) balloon after the bone is compacted, is
qualitatively different than putting formulated drug into the
cavity. When delivered while compressing the bone, the substance
becomes incorporated into the compacted bone. This can serve as a
way to instantly formulate a slow release version of the substance.
It simultaneously allows the surgeon to fill the cavity with an
appropriate supporting material, like acrylic bore cement or
biocompatible bone substitute, so no casting or metal fixation is
required. Such a combination allows the surgeon, for example, to
percutaneously fix an osteoporotic fracture while delivering a
desired therapeutic substance (like an antibiotic, bone growth
factor or osteoporosis drug) to the site. Thus, casts or metal
fixation devices may not be required in such instances.
[0197] Medically-effective amounts of therapeutic substances are
typically defined by their manufacturers or sponsors and are
generally in the range of 10 nanograms to 50 milligrams per site,
although more or less may be required in a specific case. Typical
antibiotics include gentamicin and tobramycin. Typical bone growth
factors are members of the bone morphogenetic factor, osteogenic
protein, fibroblast growth factor, insulin-like growth factor, and
transforming growth factor alpha and beta families.
Chemotherapeutic and related agents include compounds such as
cisplatin, doxorubicin, daunorubicin, methotrexate, taxol and
tamoxifen. Osteoporosis drugs include estrogen, calcitonin,
diphosphonates, and parathyroid hormone antagonists.
[0198] The balloons described in this invention can be used in open
surgical procedures at the sites discussed above to provide an
improved space for inserting orthopedic implants, bone graft, bone
substitutes, bone fillers or therapeutic substances. The size and
shape of balloon chosen will be determined depending upon the site
being treated as well as the size, shape or amount of material that
the surgeon wants to insert into the remaining bone. Square and
rectangular balloons can be used at any site for the placement of
bone substitutes like hydroxyapatites which are available in those
shapes. Balloons would desirably be made to match those
predetermined sizes, and the surgeon would chose the balloon to fit
the size of material chosen.
[0199] To insert materials which do not flow into the balloon-made
cavity, like hydroxyapatite granules or bone mineral matrix, the
surgeon can push them down a tube with a long pin whose diameter is
slightly more narrow than the inner diameter of the cannula through
procedures in which the minimally-invasive procedure is taking
place. During open surgery, the surgeon can approach the bone to be
treated as if the procedure is percutaneous, except that here is no
skin and other tissues between the surgeon and the bone being
treated. This desirably keeps the cortical bone as intact as
possible. If the material to be inserted does not flow and should
not be pushed into the cavity through a cannula (as in the case of
the hydroxyapatite block, because that may result in significant
damage to the patient), the surgeon can make the cavity using the
"minimally invasive" approach, then punch a hole using standard
tools (such as a punch, gouge or rasp) into one side of the
cortical bone to allow insertion of the block. This same approach
can be used for implanting a metal prosthesis, such as the metal
tibial component of a total knee replacement system.
[0200] Different sizes and/or shapes of balloons may be used at
sites not specified above, such as the jaw bones, the midshaft of
the arm and leg bones, the cervical vertebral bodies, the foot and
ankle bones, the ribs and the like. One of the keys to choosing
balloon shape and size in treating or preventing bone fracture is
the teaching of this application that, optimally, up to 70-90% (or
greater) of the cancellous bone can be compacted in cases where the
bone disease causing fracture (or the risk of fracture) is the loss
of cancellous bone mass (as in osteoporosis). Compacting less than
70-90% of the cancellous bone at the site being treated could
possibly leave an extensive amount of the diseased cancellous bone
at the treated site. The diseased cancellous bone could remain weak
and later collapse, causing fracture despite treatment. With this
principle, the allowed shapes and minimum sizes for any chosen bone
are explained and defined.
[0201] Of course, there are many exceptions to this 70-90% cavity
size, as generally described in this specification. One exception
is when the bone disease being treated is localized, as in
avascular necrosis, where local loss of blood supply is killing
bone in a limited area. In that case, the balloons can be smaller,
because the disease area requiring treatment is often smaller. A
second exception is in the use of the devices to improve insertion
of solid materials in defined shapes, like hydroxyapatite and
components in total joint replacement. In these cases, the balloon
shape and size is generally defined by the shape and size of the
material being inserted. Another exception is the delivery of
therapeutic substances. In this case, the cancellous bone may or
may not be affected. If it is not, some of the cancellous bone can
be sacrificed by compacting it to improve the delivery of a drug or
growth factor which has an important therapeutic purpose. In this
case, the bone with the drug inside is supported while the drug
works and then the bone heals through casting or current fixation
devices. Another exception can involve the treatment of bone
tumors, where the creation of a small cavity in cancellous bone
adjacent the tumor could facilitate the minimally invasive
manipulation and/or removal of the tumor. Another exception could
be where the quality of the cancellous bone is generally good, but
the bone has fractured and/or collapsed in some manner. In such a
case, the creation of a small cavity within the stronger cancellous
bone may displace the cortical bone fragments to a position at or
near the fragments' normal anatomic positions without significantly
compressing the cancellous bone.
[0202] Another key to choosing balloon shape and size is one
teaching of this invention--that inelastic, elastic and/or
semi-elastic balloon restraints can be utilized and that inelastic
or semi-elastic balloon materials are often preferred. Such
materials can safely and easily prevent the balloon from expanding
beyond its predetermined shape and size which can be defined by the
limits of the normal dimensions of the outside edge of the
cancellous bone (which is inside of the cortical bone). A balloon
which expands too much, for example, can create the risk of
immediate fracture, so in one embodiment this defines the upper
limits of balloon sizes at each site. With many typical angioplasty
balloons, surgeons usually rely on monitoring pressure (instead of
the balloon design features of this invention) to prevent their
balloons from inflating too much. This often requires greater
surgical skill than the teachings of the present application, which
are to take an X-ray of the site to be treated and measure the
important dimensions as described herein. In addition, in bone
treatment, relying on pressure can often result in an inferior
clinical outcome. The surgeon generally will not know in advance
what pressure is required to completely compact the cancellous
bone, because this varies depending on the thickness of the
cancellous bone and the extent to which it has lost density due to
its disease. The surgeon is often likely to under inflate the
balloon to avoid the potential consequences of overinflation and/or
cortical bone fracture.
[0203] Another teaching of this application is that, while maximal
pressures equally exerted in all directions can typically compress
the weakest areas of cancellous bone, the use of restraints in a
balloon body will desirably control balloon expansion to some
degree. If the balloon design does not incorporate restraints, it
may not compress cancellous bone in an optimal manner for
reinforcement and/or repair of a fractured vertebral. The shape of
the cancellous bone to be compressed, and the local structures that
could be harmed if bone were moved inappropriately, are generally
understood by medical professionals using textbooks of human
skeletal anatomy along with their knowledge of the site and its
disease or injury. Ranges of shapes and dimensions are defined by
the site to be treated. Precise dimensions for a given patient can
be determined by X-ray of the site to be treated, the therapeutic
goal and safety constraints at the site. For diseased bone,
replacement of most of the cancellous bone may be desired, so a
balloon whose shape and size will compress around 70-90% (or
greater) of the volume of the cancellous bone in the treated region
can be chosen. However, as previously noted balloons that are
smaller or larger may be appropriate, particularly where localized
bone treatments and/or delivery of a therapeutic substance is the
main goal. If desired, the balloon size can be chosen by the
desired amount of therapeutic substance, keeping in mind that the
balloon should desirably not displace the cortical bone beyond its
normal unfractured dimensions.
[0204] While the new devices and methods have been more
specifically described in the context of the treatment of human
vertebrae, it should be understood that other human or animal bone
types can be treated in the same or equivalent fashion. By way of
example, and not by limitation, the present systems and methods
could be used in any bone having bone marrow therein, including the
radius, the humerus, the vertebrae, the femur, the tibia or the
calcaneus. In addition, other embodiments and uses of the invention
will be apparent to those skilled in the art from consideration of
the specification and practice of the invention disclosed herein.
All documents referenced herein are specifically and entirely
incorporated by reference. The specification and examples should be
considered exemplary only with the true scope and spirit of the
invention indicated by the following claims. As will be easily
understood by those of ordinary skill in the art, variations and
modifications of each of the disclosed embodiments can be easily
made within the scope of this invention as defined by the following
claims.
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