U.S. patent application number 13/305501 was filed with the patent office on 2012-09-20 for systems for delivering bone fill material.
This patent application is currently assigned to DFINE, INC.. Invention is credited to John H. Shadduck, Csaba Truckai.
Application Number | 20120239049 13/305501 |
Document ID | / |
Family ID | 38054492 |
Filed Date | 2012-09-20 |
United States Patent
Application |
20120239049 |
Kind Code |
A1 |
Truckai; Csaba ; et
al. |
September 20, 2012 |
SYSTEMS FOR DELIVERING BONE FILL MATERIAL
Abstract
The present invention relates in certain embodiments to medical
devices, systems and methods for use in osteoplasty procedures,
such as vertebral compression fractures. One system for delivering
a bone fill material to a bone includes an elongated introducer
configured for insertion into a bone and having a channel sized to
allow a flow of bone fill material therethrough. The introducer has
at least one outlet opening in communication with the channel for
delivering the bone fill material into the bone. A thermal energy
emitter is coupled to the introducer and configured to apply
thermal energy to the bone fill material flowing through the
introducer. A hydraulic pressure source is operatively coupled to
the introducer and configured to apply a force on the bone fill
material to provide a pressurized flow of bone fill material
through the introducer.
Inventors: |
Truckai; Csaba; (Saratoga,
CA) ; Shadduck; John H.; (Menlo Park, CA) |
Assignee: |
DFINE, INC.
San Jose
CA
|
Family ID: |
38054492 |
Appl. No.: |
13/305501 |
Filed: |
November 28, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11469752 |
Sep 1, 2006 |
8066712 |
|
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13305501 |
|
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60762611 |
Jan 27, 2006 |
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60788755 |
Apr 3, 2006 |
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Current U.S.
Class: |
606/94 |
Current CPC
Class: |
A61B 2090/064 20160201;
A61B 17/8811 20130101; A61B 17/8822 20130101; A61B 2017/00022
20130101; A61B 17/8836 20130101; A61B 2017/00084 20130101; A61F
2/4601 20130101; A61F 2/44 20130101 |
Class at
Publication: |
606/94 |
International
Class: |
A61B 17/58 20060101
A61B017/58 |
Claims
1. (canceled)
2. A system for delivering a bone fill material to a vertebra,
comprising: an elongated introducer configured for insertion into a
vertebral body and for delivery of bone fill material into the
vertebral body, the introducer defining a channel therethrough; a
stylet having a sharp tip, the stylet and introducer configured
such that the stylet is to be positioned within the channel in the
introducer during insertion of the introducer into the vertebral
body and the stylet is to be removed from the channel prior to
delivery of bone fill material into the vertebral body; a container
of bone fill material; a piston positioned within the container to
force bone fill material out of the container and through the
introducer; a thermal energy emitter configured to apply thermal
energy to the bone fill material after it is ejected out of the
container; a handle having an electrical outlet for connecting a
power source to the thermal energy emitter and having an inlet for
connection with the container of bone fill material thereby
providing communication between the channel and the container; and
a pressure source coupled to the container and configured to apply
a force on the piston.
3. The system of claim 2, further comprising an electrical cable
detachably coupled to the handle at the electrical outlet via a
male-female plug.
4. The system of claim 3, further comprising an energy source
coupled to the thermal energy emitter through the electrical
cable.
5. The system of claim 2, wherein the handle is integrally formed
with the introducer.
6. The system of claim 2, wherein the pressure source comprises a
hydraulic pressure source coupled to the container and configured
to apply a force on the bone fill material in the container to
force bone fill material out of the container into the
introducer.
7. The system of claim 2, further comprising a sensor to measure a
parameter of the bone fill material.
8. The system of claim 7, wherein the parameter comprises at least
one of temperature, impedance, capacitance, conductivity, pressure,
viscosity, a flow parameter, volume, reflectance, an optical
parameter, a mechanical parameter, and an acoustical parameter.
9. The system of claim 7, further comprising a computer controller
configured to receive data from the sensor and to control, based at
least in part on the data, the thermal energy applied to the flow
of bone fill material.
10. The system of claim 9, wherein the computer controller is
configured to control, based at least in part on the data, the
force from the pressure source applied to the bone fill material,
the computer controller thereby configured to control both the
increase in viscosity of the bone fill material and the flow of
bone fill material.
11. A system for delivering a bone fill material to a bone,
comprising: an elongated introducer configured for insertion into a
bone, the introducer defining a channel sized to allow a flow of a
bone fill material therethrough, the introducer having at least one
opening in communication with the channel for delivering the bone
fill material into the bone; a stylet positionable within the
channel of the introducer; a container of bone fill material; a
piston within the container of bone fill material to transfer bone
fill material to the introducer; a thermal energy emitter
configured to apply thermal energy to the bone fill material within
the system; a handle having a connection for electrically coupling
a power source to the thermal energy emitter and having an inlet
for receiving bone fill material from the container; and a pressure
source configured to apply a force on the bone fill material
through the piston to provide a pressurized flow of bone fill
material through the introducer.
12. The system of claim 11, further comprising an electrical cable
detachably coupled to the handle at the connection via a
male-female plug.
13. The system of claim 11, wherein the thermal energy emitter is
disposed in the channel of the introducer proximally spaced from at
least one opening of the introducer.
14. The system of claim 11, wherein the handle is integrally formed
with the introducer.
15. The system of claim 11, further comprising a sensor to measure
a parameter of the bone fill material.
16. The system of claim 15, further comprising a computer
controller configured to receive data from the sensor.
17. The system of claim 11, wherein the thermal energy emitter is
selected from the group consisting of an electromagnetic energy
emitter, a resistive heat emitter, a radiofrequency energy emitter,
a light energy emitter, a microwave emitter, an inductive heat
emitter and an ultrasound source.
18. A system for delivering a bone cement into a bone, comprising:
a cement introducer system having an introducer configured for
insertion into a bone, the introducer defining a channel for
carrying the bone cement, the introducer having at least one
opening in communication with the channel for delivering the bone
cement into the bone; a stylet to be positioned within the channel
in the introducer during insertion of the introducer into the bone
and to be removed from the channel prior to delivery of bone fill
material into the bone; a container of bone fill material; a piston
within the container to force bone fill material out of the
container and through the introducer; a thermal energy emitter
configured to apply thermal energy to the bone fill material within
the system; a handle having a connector that allows for releasable
connection with an electrical connector coupled to an energy source
and having an inlet for connection with the container of bone fill
material thereby providing communication between the channel and
the container; and a pressure source coupled to the container and
configured to apply a force on the piston.
19. The system of claim 18, wherein the pressure source comprises a
hydraulic pressure mechanism comprising a hydraulic line and the
piston, the hydraulic pressure mechanism coupled to the cement
introducer system and configured to hydraulically drive the piston
by a liquid within the hydraulic line to apply a force on the bone
cement and to eject bone cement from the cement introducer
system.
20. The system of claim 18, wherein the sensor is configured to
measure a parameter of the bone fill material that is within the
system.
21. The system of claim 18, further comprising the electrical
connector coupled to the energy source.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of application Ser. No.
11/469,752, filed Sep. 1, 2006, now U.S. Pat. No. 8,066,712, which
claims the benefit of U.S. Provisional Patent Application No.
60/762,611, filed Jan. 27, 2006, and of U.S. Provisional
Application No. 60/788,755, filed Apr. 3, 2006, the entire contents
of which are hereby incorporated by reference and should be
considered a part of this specification.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates in certain embodiments to
medical devices for osteoplasty treatment procedures, such as
vertebral compression fractures. More particularly, embodiments of
the invention relate to systems for delivering a bone fill material
into a bone, such as a vertebral body.
[0004] 2. Description of the Related Art
[0005] Osteoporotic fractures are prevalent in the elderly, with an
annual estimate of 1.5 million fractures in the United States
alone. These include 750,000 vertebral compression fractures (VCFs)
and 250,000 hip fractures. The annual cost of osteoporotic
fractures in the United States has been estimated at $13.8 billion.
The prevalence of VCFs in women age 50 and older has been estimated
at 26%. The prevalence increases with age, reaching 40% among
80-year-old women. Medical advances aimed at slowing or arresting
bone loss from aging have not provided solutions to this problem.
Further, the population affected will grow steadily as life
expectancy increases. Osteoporosis affects the entire skeleton but
most commonly causes fractures in the spine and hip. Spinal or
vertebral fractures also cause other serious side effects, with
patients suffering from loss of height, deformity and persistent
pain which can significantly impair mobility and quality of life.
Fracture pain usually lasts 4 to 6 weeks, with intense pain at the
fracture site. Chronic pain often occurs when one vertebral level
is greatly collapsed or multiple levels are collapsed.
[0006] Postmenopausal women are predisposed to fractures, such as
in the vertebrae, due to a decrease in bone mineral density that
accompanies postmenopausal osteoporosis. Osteoporosis is a
pathologic state that literally means "porous bones". Skeletal
bones are made up of a thick cortical shell and a strong inner
meshwork, or cancellous bone, of with collagen, calcium salts and
other minerals. Cancellous bone is similar to a honeycomb, with
blood vessels and bone marrow in the spaces. Osteoporosis describes
a condition of decreased bone mass that leads to fragile bones
which are at an increased risk for fractures. In an osteoporosis
bone, the sponge-like cancellous bone has pores or voids that
increase in dimension making the bone very fragile. In young,
healthy bone tissue, bone breakdown occurs continually as the
result of osteoclast activity, but the breakdown is balanced by new
bone formation by osteoblasts. In an elderly patient, bone
resorption can surpass bone formation thus resulting in
deterioration of bone density. Osteoporosis occurs largely without
symptoms until a fracture occurs.
[0007] Vertebroplasty and kyphoplasty are recently developed
techniques for treating vertebral compression fractures.
Percutaneous vertebroplasty was first reported by a French group in
1987 for the treatment of painful hemangiomas. In the 1990's,
percutaneous vertebroplasty was extended to indications including
osteoporotic vertebral compression fractures, traumatic compression
fractures, and painful vertebral metastasis. Vertebroplasty is the
percutaneous injection of PMMA (polymethylmethacrylate) into a
fractured vertebral body via a trocar and cannula. The targeted
vertebrae are identified under fluoroscopy. A needle is introduced
into the vertebrae body under fluoroscopic control, to allow direct
visualization. A bilateral transpedicular (through the pedicle of
the vertebrae) approach is typical but the procedure can be done
unilaterally. The bilateral transpedicular approach allows for more
uniform PMMA infill of the vertebra.
[0008] In a bilateral approach, approximately 1 to 4 ml of PMMA is
used on each side of the vertebra. Since the PMMA needs to be is
forced into the cancellous bone, the techniques require high
pressures and fairly low viscosity cement. Since the cortical bone
of the targeted vertebra may have a recent fracture, there is the
potential of PMMA leakage. The PMMA cement contains radiopaque
materials so that when injected under live fluoroscopy, cement
localization and leakage can be observed. The visualization of PMMA
injection and extravasion are critical to the technique--and the
physician terminates PMMA injection when leakage is evident. The
cement is injected using syringes to allow the physician manual
control of injection pressure.
[0009] Kyphoplasty is a modification of percutaneous
vertebroplasty. Kyphoplasty involves a preliminary step consisting
of the percutaneous placement of an inflatable balloon tamp in the
vertebral body. Inflation of the balloon creates a cavity in the
bone prior to cement injection. The proponents of percutaneous
kyphoplasty have suggested that high pressure balloon-tamp
inflation can at least partially restore vertebral body height. In
kyphoplasty, some physicians state that PMMA can be injected at a
lower pressure into the collapsed vertebra since a cavity exists,
when compared to conventional vertebroplasty.
[0010] The principal indications for any form of vertebroplasty are
osteoporotic vertebral collapse with debilitating pain. Radiography
and computed tomography must be performed in the days preceding
treatment to determine the extent of vertebral collapse, the
presence of epidural or foraminal stenosis caused by bone fragment
retropulsion, the presence of cortical destruction or fracture and
the visibility and degree of involvement of the pedicles.
[0011] Leakage of PMMA during vertebroplasty can result in very
serious complications including compression of adjacent structures
that necessitate emergency decompressive surgery. See "Anatomical
and Pathological Considerations in Percutaneous Vertebroplasty and
Kyphoplasty: A Reappraisal of the Vertebral Venous System", Groen,
R. et al, Spine Vol. 29, No. 13, pp 1465-1471 2004. Leakage or
extravasion of PMMA is a critical issue and can be divided into
paravertebral leakage, venous infiltration, epidural leakage and
intradiscal leakage. The exothermic reaction of PMMA carries
potential catastrophic consequences if thermal damage were to
extend to the dural sac, cord, and nerve roots. Surgical evacuation
of leaked cement in the spinal canal has been reported. It has been
found that leakage of PMMA is related to various clinical factors
such as the vertebral compression pattern, and the extent of the
cortical fracture, bone mineral density, the interval from injury
to operation, the amount of PMMA injected and the location of the
injector tip. In one recent study, close to 50% of vertebroplasty
cases resulted in leakage of PMMA from the vertebral bodies. See
Hyun-Woo Do et al, "The Analysis of Polymethylmethacrylate Leakage
after Vertebroplasty for Vertebral Body Compression Fractures",
Jour. of Korean Neurosurg. Soc. Vol. 35, No. 5 (May 2004) pp.
478-82, (http://www.jkns.or.kr/htm/abstract.asp?no=0042004086).
[0012] Another recent study was directed to the incidence of new
VCFs adjacent to the vertebral bodies that were initially treated.
Vertebroplasty patients often return with new pain caused by a new
vertebral body fracture. Leakage of cement into an adjacent disc
space during vertebroplasty increases the risk of a new fracture of
adjacent vertebral bodies. See Am. J. Neuroradiol. 2004 February;
25(2):175-80. The study found that 58% of vertebral bodies adjacent
to a disc with cement leakage fractured during the follow-up period
compared with 12% of vertebral bodies adjacent to a disc without
cement leakage.
[0013] Another life-threatening complication of vertebroplasty is
pulmonary embolism. See Bernhard, J. et al, "Asymptomatic diffuse
pulmonary embolism caused by acrylic cement: an unusual
complication of percutaneous vertebroplasty", Ann. Rheum. Dis.
2003; 62:85-86. The vapors from PMMA preparation and injection also
are cause for concern. See Kirby, B, et al., "Acute bronchospasm
due to exposure to polymethylmethacrylate vapors during
percutaneous vertebroplasty", Am. J. Roentgenol. 2003;
180:543-544.
[0014] In both higher pressure cement injection (vertebroplasty)
and balloon-tamped cementing procedures (kyphoplasty), the methods
do not provide for well controlled augmentation of vertebral body
height. The direct injection of bone cement simply follows the path
of least resistance within the fractured bone. The expansion of a
balloon applies also compacting forces along lines of least
resistance in the collapsed cancellous bone. Thus, the reduction of
a vertebral compression fracture is not optimized or controlled in
high pressure balloons as forces of balloon expansion occur in
multiple directions.
[0015] In a kyphoplasty procedure, the physician often uses very
high pressures (e.g., up to 200 or 300 psi) to inflate the balloon
which crushes and compacts cancellous bone. Expansion of the
balloon under high pressures close to cortical bone can fracture
the cortical bone, typically the endplates, which can cause
regional damage to the cortical bone with the risk of cortical bone
necrosis. Such cortical bone damage is highly undesirable as the
endplate and adjacent structures provide nutrients for the
disc.
[0016] Kyphoplasty also does not provide a distraction mechanism
capable of 100% vertebral height restoration. Further, the
kyphoplasty balloons under very high pressure typically apply
forces to vertebral endplates within a central region of the
cortical bone that may be weak, rather than distributing forces
over the endplate.
[0017] There is a general need to provide bone cements and methods
for use in treatment of vertebral compression fractures that
provide a greater degree of control over introduction of cement and
that provide better outcomes. Embodiments of the present invention
meet this need and provide several other advantages in a novel and
nonobvious manner.
SUMMARY OF THE INVENTION
[0018] Certain embodiments of the invention provide systems and
methods for treating bone, such as a vertebra, by delivering bone
fill material into the interior of the vertebra. One embodiment
utilizes Rf energy or other energy sources to controllably elevate
the temperature of bone fill material flows as the flows exit the
working end of an introducer. A computer controller controls the
bone fill material flow parameters and energy delivery parameters
for selectively polymerizing the fill material inflow plume to
thereby control the direction of flow and the ultimate geometry of
a flowable, in-situ hardenable bone fill material. The system and
method further includes means for sealing tissue in the interior of
a vertebra to prevent migration of monomers, fat or emboli into the
patient's bloodstream.
[0019] In another embodiment, a controller is provided to control
all parameters of bone fill material injection. For example, the
controller can control bone fill material inflow parameters from,
for example, a hydraulic mechanism. The controller can also control
the sensing system and energy delivery parameters for selectively
heating tissue or polymerizing bone fill material at both the
interior and exterior of the introducer. The workload on a
physician during an osteoplasty procedure can thus advantageously
be reduced.
[0020] In one embodiment, a system for delivering a bone fill
material to a vertebra is provided. The system comprises an
elongated introducer configured for insertion into a vertebral body
and delivery of bone fill material through a channel of the
introducer into the vertebral body. The system also comprises a
container of bone fill material coupleable to the introducer and a
thermal energy emitter coupled to the introducer, the thermal
energy emitter configured to apply thermal energy to the bone fill
material flowing through the introducer. The system further
comprises a hydraulic pressure source coupled to the container and
configured to apply a force on the bone fill material in the
container to eject bone fill material from the container into the
introducer.
[0021] In another embodiment, a system for delivering a bone fill
material to a bone is provided. The system comprises an elongated
introducer configured for insertion into a bone. The introducer
defines a channel sized to allow a flow of a bone fill material
therethrough. The introducer also has at least one opening in
communication with the channel for delivering the bone fill
material into the bone. The system also comprises a thermal energy
emitter coupled to the introducer and configured to apply thermal
energy to the bone fill material flowing through the introducer.
The system further comprises a hydraulic pressure source
operatively coupled to the introducer and configured to apply a
force on the bone fill material to provide a pressurized flow of
bone fill material through the introducer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] In order to better understand the invention and to see how
it may be carried out in practice, some preferred embodiments are
next described, by way of non-limiting examples only, with
reference to the accompanying drawings, in which like reference
characters denote corresponding features consistently throughout
similar embodiments in the attached drawings.
[0023] FIG. 1 is a schematic side view of a spine segment showing a
vertebra with a compression fracture and an introducer, in
accordance with one embodiment disclosed herein.
[0024] FIG. 2A is a schematic perspective view of a system for
treating bone, in accordance with one embodiment.
[0025] FIG. 2B is a schematic perspective view of a working end of
the introducer of FIG. 2A.
[0026] FIG. 3A is a schematic perspective view of a working end of
an introducer, in accordance with one embodiment.
[0027] FIG. 3B is a schematic perspective view of a working end of
an introducer, in accordance with another embodiment.
[0028] FIG. 3C is a schematic perspective view of a working end of
an introducer, in accordance with yet another embodiment.
[0029] FIG. 4 is a schematic cross-sectional side view of one
embodiment of a working end of a probe, in accordance with one
embodiment.
[0030] FIG. 5A is a schematic side view of an introducer inserted
into a vertebral body and injecting flowable fill material into the
vertebral body.
[0031] FIG. 5B is a schematic side view of the introducer in FIG.
5A injecting a relatively high viscosity volume of flowable fill
material into the vertebral body, in accordance with one embodiment
of the present invention.
[0032] FIG. 6 is a schematic perspective view of a system for
treating bone, in accordance with another embodiment.
[0033] FIG. 7A is a schematic sectional view of a fill material, in
accordance with one embodiment.
[0034] FIG. 7B is a schematic sectional view of a fill material, in
accordance with another embodiment.
[0035] FIG. 8A is a schematic perspective view of a system for
treating bone, in accordance with another embodiment.
[0036] FIG. 8B is a schematic perspective view of the system in
FIG. 8A, injecting an additional volume of fill material into a
vertebral body.
[0037] FIG. 9A is a schematic cross-sectional view of one step in a
method for treating bone, in accordance with one embodiment.
[0038] FIG. 9B is a schematic cross-sectional view of another step
in a method for treating bone, in accordance with one
embodiment.
[0039] FIG. 9C is a schematic cross-sectional view of still another
step in a method for treating bone, in accordance with one
embodiment.
[0040] FIG. 10A is a schematic cross-sectional view of a step in a
method for treating bone, in accordance with another
embodiment.
[0041] FIG. 10B is a schematic cross-sectional view of another step
in a method for treating bone, in accordance with another
embodiment.
[0042] FIG. 11A is a schematic perspective view of a system for
treating bone, in accordance with another embodiment.
[0043] FIG. 11B is a schematic perspective view of the system in
FIG. 11A, applying energy to a fill material.
[0044] FIG. 12 is a schematic perspective view of a system for
treating bone, in accordance with another embodiment.
[0045] FIG. 13 is a schematic view of another embodiment of a bone
cement delivery system together with an aspiration source.
[0046] FIG. 14A is a sectional view of a working end of an
introducer as in FIG. 13 showing the orientation of a cement
injection port in a vertebra.
[0047] FIG. 14B is a sectional view of the working end of FIG. 14A
showing an initial inflow of bone cement.
[0048] FIG. 14C is a sectional view of the working end of FIG. 14B
showing an additional inflow of bone cement to reduces a vertebral
fracture.
[0049] FIG. 15A is a sectional view of a vertebra depicting a first
mode of operation wherein an initial flow of bone cement is
provided under selected flow parameters that allow cement
interdigitation into cancellous bone.
[0050] FIG. 15B is a sectional view of a vertebra similar to FIG.
15A depicting a second mode of operation wherein cement flows are
provided in a high acceleration pulse that disallows cement
interdigitation into cancellous bone.
[0051] FIG. 16 is a sectional schematic view of another embodiment
of a bone cement delivery system.
[0052] FIG. 17 is a schematic perspective view of another
embodiment of a bone cement delivery system for treating
osteoporotic bone or a fractured vertebra.
[0053] FIG. 18A is a sectional view of a vertebra showing one step
of a method for delivering bone cement to a vertebra, in accordance
with one embodiment.
[0054] FIG. 18B is a sectional view of the vertebra of FIG. 18A
showing another step of the method for delivering bone cement to a
vertebra.
[0055] FIG. 18C is a sectional view similar to FIGS. 18A-18B
showing another step of the method for delivering bone cement to a
vertebra.
[0056] FIG. 19 is a perspective schematic view of another
embodiment of a bone cement delivery system.
[0057] FIG. 20 is a perspective schematic view of another
embodiment of an injector with a thin wall sleeve and a sensor
system.
[0058] FIG. 21 is a perspective schematic view of another
embodiment of a bone cement delivery system.
[0059] FIG. 22 is a perspective schematic view of another
embodiment of a bone cement delivery system.
[0060] FIG. 23A is a sectional view of one embodiment of a bone
cement injector having an energy emitter.
[0061] FIG. 23B is a sectional view of another embodiment of a bone
cement injector having an energy emitter.
[0062] FIG. 24 is a perspective schematic view of another
embodiment of a bone cement delivery system.
[0063] FIG. 25 is a sectional schematic view of another embodiment
of a bone cement injector.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Definitions
[0064] "Bone fill material, infill material or composition"
includes its ordinary meaning and is defined as any material for
infilling a bone that includes an in-situ hardenable material, such
as bone cement. The fill material also can include other "fillers"
such as filaments, microspheres, powders, granular elements,
flakes, chips, tubules and the like, autograft or allograft
materials, as well as other chemicals, pharmacological agents or
other bioactive agents.
[0065] "Flowable material" includes its ordinary meaning and is
defined as a material continuum that is unable to withstand a
static shear stress and responds with an irrecoverable flow (a
fluid)--unlike an elastic material or elastomer that responds to
shear stress with a recoverable deformation. Flowable material
includes fill material or composites that include a fluid (first)
component and an elastic or inelastic material (second) component
that responds to stress with a flow, no matter the proportions of
the first and second component, and wherein the above shear test
does not apply to the second component alone.
[0066] An "elastomer" includes its ordinary meaning and is defined
as material having to some extent the elastic properties of natural
rubber wherein the material resumes or moves toward an original
shape when a deforming force is removed.
[0067] "Substantially" or "substantial" mean largely but not
necessarily entirely. For example, substantially may mean about 10%
to about 99.999%, about 25% to about 99.999% or about 50% to about
99.999%.
[0068] "Osteoplasty" includes its ordinary meaning and means any
procedure wherein fill material is delivered into the interior of a
bone.
[0069] "Vertebroplasty" includes its ordinary meaning and means any
procedure wherein fill material is delivered into the interior of a
vertebra.
Systems and Methods of Infill Material Delivery and Energy
Application
[0070] For the purpose of understanding the principles of the
invention, reference will now be made to the embodiments
illustrated in the drawings and accompanying text that describe the
invention. Further details on systems and methods for the delivery
of bone cement can be found in U.S. patent application Ser. No.
11/165,652, filed Jun. 24, 2005, now U.S. Pub. No. 2006-0122623;
U.S. application Ser. No. 11/196,045, filed Aug. 2, 2005, now U.S.
Pub. No. 2006-0122624; U.S. application Ser. No. 11/208,448, filed
Aug. 20, 2005, now U.S. Pub. No. 2006-0122621; and U.S. application
Ser. No. 11/209,035, filed Aug. 22, 2005, now U.S. Pub. No.
2006-0122625, the entire contents of which are hereby incorporated
by reference and should be considered a part of this
specification.
[0071] FIG. 1 illustrates one embodiment of the invention for
treating a spine segment in which a vertebral body 90 has a wedge
compression fracture indicated at 94. In one embodiment, the
systems and methods are directed to safely introducing a bone fill
material into cancellous bone of the vertebra without extravasion
of fill material in unwanted directions (i) to prevent micromotion
in the fracture for eliminating pain, and (ii) to support the
vertebra and increase vertebral body height. Further, systems and
methods are provided for sealing cancellous bone (e.g., blood
vessels, fatty tissues etc.) in order to prevent monomers, fat,
fill material and other emboli from entering the venous system
during treatment.
[0072] FIG. 1 illustrates a fractured vertebra and bone infill
system 100 which includes probe 105 having a handle end 106
extending to an elongated introducer 110A and working end 115A,
shown in FIG. 2A. The introducer is shown introduced through
pedicle 118 of the vertebra for accessing the osteoporotic
cancellous bone 122 (See FIG. 2A). The initial aspects of the
procedure are similar to conventional percutaneous vertebroplasty
wherein the patient is placed in a prone position on an operating
table. The patient is typically under conscious sedation, although
general anesthesia is an alternative. The physician injects a local
anesthetic (e.g., 1% Lidocaine) into the region overlying the
targeted pedicle or pedicles as well as the periosteum of the
pedicle(s). Thereafter, the physician uses a scalpel to make a 1 to
5 mm skin incision over each targeted pedicle. Thereafter, the
introducer 110A is advanced through the pedicle into the anterior
region of the vertebral body, which typically is the region of
greatest compression and fracture. The physician confirms the
introducer path posterior to the pedicle, through the pedicle and
within the vertebral body by anteroposterior and lateral X-Ray
projection fluoroscopic views. The introduction of infill material
as described below can be imaged several times, or continuously,
during the treatment depending on the imaging method.
[0073] It should be appreciated that the introducer also can be
introduced into the vertebra from other angles, for example, along
axis 113 through the wall of the vertebral body 114 as in FIG. 1 or
in an anterior approach (not shown). Further, first and second
cooperating introducers can be used in a bilateral transpedicular
approach. Additionally, any mechanism known in the art for creating
an access opening into the interior of the vertebral body 90 can be
used, including open surgical procedures.
[0074] Now referring to FIGS. 2A and 2B, the end of introducer 110A
is shown schematically after being introduced into cancellous bone
122 with an inflow of fill material indicated at 120. The
cancellous bone can be in any bone, for example in a vertebra. It
can be seen that the introducer 110A and working end 115A comprise
a sleeve or shaft that is preferably fabricated of a metal having a
flow channel 118 extending therethrough from the proximal handle
end 106 (see FIG. 1). In one embodiment, the introducer shaft is a
stainless steel tube 123 having an outside diameter ranging between
about 3.5 and 4.5 mm, but other dimensions are possible. As can be
seen in FIGS. 2A and 3A, the flow channel 118 can terminate in a
single distal opening or outlet 124a in the working end 115A, or
there can be a plurality of flow outlets or ports 124b arranged
angularly about the radially outward surface of the working end
115A, as shown in FIG. 3B. The outlets in the working end thus
allow for distal or radial ejection of fill material, or a working
end can have a combination of radial and distal end outlets. As can
be seen in FIG. 3C, the distal end of working end 115A also can
provide an angled distal end outlet 124c for directing the flow of
fill material from the outlet by rotating the working end 115A.
[0075] In FIGS. 2A and 2B, it can be seen that system 100 includes
a remote energy source 125A and a controller 125B that are
operatively coupled to an energy emitter 128 in the working end
115A of the introducer 110A for applying energy to the fill
material 120 contemporaneous with and subsequent to ejection of the
fill material 120 from the working end 115A. In one preferred
embodiment, the energy source 125A is a radiofrequency (Rf) source
known in the art that is connected to at least one electrode (132a
and 132b in FIG. 2B) in contact with injected fill material 120,
which preferably carries a radiosensitive composition therein. It
is equally possible to use other remote energy sources and emitters
128 in the working end 115A which fall within the scope of the
invention, such as (i) an electrical source coupled to a resistive
heating element in the working end, (ii) a light energy source
(coherent or broadband) coupled to an optical fiber or other light
channel terminating in the working end; (iii) an ultrasound source
coupled to an emitter in the working end; or a (iv) microwave
source coupled to an antenna in the working end. In still another
embodiment, the energy source 125A can be a magnetic source. The
fill material 120 preferably includes an energy-absorbing material
or an energy-transmitting material that cooperates with energy
delivered from a selected energy source. For example, the
energy-absorbing or energy-transmitting material can be a
radiosensitive or conductive material for cooperating with an Rf
source, chromophores for cooperating with a light source,
ferromagnetic particles for cooperating with a magnetic source, and
the like. In one embodiment, the fill material 120 can include a
composition having an energy-absorbing property and an
energy-transmitting property for cooperating with the remote energy
source 125A. For example, the composition can absorb energy from
the remote energy source 125A for polymerizing the composite or
transmit energy for heating tissue adjacent to the composite.
[0076] As can be understood from FIGS. 2A and 2B, the exemplary
introducer 110A is operatively coupleable to a source 145 of bone
fill material 120 together with a pressure source or mechanism 150
that operates on the source of fill material 145 to deliver the
fill material 120 through the introducer 110A into a bone (see
arrows). The pressure source 150 can comprise any type of pump
mechanism, such as a piston pump, screw pump or other hydraulic
pump mechanism. In FIG. 2B, the pump mechanism is shown as a piston
or plunger 152 that is slidable in the channel 118 of introducer
110A. In one embodiment, the pressure source 150 includes a
controller 150B that controls the pressure applied by the pressure
source 150. For example, where the pressure source 150 is a piston
pump or screw pump that is motor driven, the controller 150B can
adjust the motor speed to vary the pressure applied by the pressure
source 150 to the inflow of the bone fill material 120. In one
embodiment, the controller 150B also controls the volume of the
bone fill material 120 that is introduced to a bone portion. In
another embodiment, the controller 150B, or a separate controller,
can also control the volume of bone fill material 120 introduced
into the bone portion. For example, the controller 150B can operate
a valve associated with the bone fill source 145 to selectively
vary the valve opening, thus varying the volume of bone fill
material 120 introduced to the bone portion.
[0077] As shown in FIGS. 2A and 2B, the introducer 110A preferably
has an electrically and thermally insulative interior sleeve 154
that defines the interior flow channel 118. The sleeve can be any
suitable polymer known in the art such as PEEK, Teflon.TM. or a
polyimide. As can be seen in FIG. 2B, interior sleeve 154 carries
conductive surfaces that function as energy emitter 128, and more
particularly comprise spaced apart opposing polarity electrodes
132a and 132b. The electrodes 132a and 132b can have any spaced
apart configuration and are disposed about the distal termination
of channel 118 or about the surfaces of outlet 124a. The electrode
configuration alternatively can include a first electrode in the
interior of channel 118 and a second electrode on an exterior of
introducer 110A. For example, the metallic sleeve 123 or a distal
portion thereof can comprise one electrode. In a preferred
embodiment, the electrodes 132a and 132b are connected to the Rf
energy source 125A and controller 125B by an electrical cable 156
with (+) and (-) electrical leads 158a and 158b therein that extend
through the insulative sleeve 154 to the opposing polarity
electrodes. In one embodiment, the electrical cable 156 is
detachably coupled to the handle end 106 of probe 105 by
male-female plug (not shown). The electrodes 132a and 132b can be
fabricated of any suitable materials known to those skilled in the
art, such as stainless steels, nickel-titanium alloys and alloys of
gold, silver platinum and the like.
[0078] In one embodiment, not shown, the working end 115A can also
carry any suitable thermocouple or temperature sensor for providing
data to controller 125B relating to the temperature of the fill
material 120 during energy delivery. One or more thermocouples may
be positioned at the distal tip of the introducer, or along an
outer surface of the introducer and spaced from the distal end, in
order to provide temperature readings at different locations within
the bone. The thermocouple may also be slideable along the length
of the introducer. In another embodiment, the working end can have
at least one side port (not shown) in communication with a coolant
source, the port configured to provide the coolant (e.g., saline)
therethrough into the cancellous bone 122 to cool the cancellous
bone in response to a temperature reading from the temperature
sensor.
[0079] Now turning to FIG. 4, the sectional view of working end
115A illustrates the application of energy to fill material 120 as
it is being ejected from outlet 124a. The fill material 120 in the
proximal portion of channel 118 is preferably a low viscosity
flowable material such as a two-part curable polymer that has been
mixed (e.g., PMMA) but without any polymerization having, for
example, a viscosity of less than about 50,000 cps. Such a low
viscosity fill material allows for simplified lower pressure
injection through the introducer 110A. Further, the system allows
the use of a low viscosity fill material 120 which can save great
deal of time for the physician.
[0080] In a preferred embodiment, it is no longer necessary to wait
for the bone cement to partly polymerize before injection. As
depicted in FIG. 4, energy delivery at selected parameters from
electrodes 132a and 132b to fill material 120 contemporaneous with
its ejection from outlet 124a selectively alters a property of fill
material indicated at 120'. In one embodiment, the altered flow
property is viscosity. For example, the viscosity of the fill
material 120' can be increased to a higher viscosity ranging from
about 100,000 cps or more, 1,000,000 cps or more, to 2,000,000 cps
or more. In another embodiment, the flow property is Young's
modulus. For example, the Young's modulus of the fill material 120'
can be altered to be between about 10 kPa and about 10 GPa. In
still another embodiment, the flow property can be one of
durometer, hardness and compliance.
[0081] Preferably, the fill material 120 carries a radiosensitive
composition for cooperating with the Rf source 125A, as further
described below. At a predetermined fill material flow rate and at
selected Rf energy delivery parameters, the altered fill material
120' after ejection can comprise an increased viscosity material or
an elastomer. At yet another predetermined fill material flow rate
and at other Rf energy delivery parameters, the altered fill
material 120' after ejection can comprise a substantially solid
material. In the system embodiment utilized for vertebroplasty as
depicted in FIGS. 2A and 5B, the controller 125B is adapted for
delivering Rf energy contemporaneous with the selected flow rate of
fill material 120 to provide a substantially high viscosity fill
material 120' that is still capable of permeating cancellous bone.
In other osteoplasty procedures such as treating necrosis of a
bone, the system controller 125B can be adapted to provide much
harder fill material 120' upon ejection from outlet 124a. Further,
the system can be adapted to apply Rf energy to the fill material
continuously, or in a pulse mode or in any selected intervals based
on flow rate, presets, or in response to feedback from temperature
sensors, impedance measurements or other suitable signals known to
those skilled in the art.
[0082] In one embodiment, the controller 125B includes algorithms
for adjusting power delivery applied by the energy source 125A. For
example, in one embodiment the controller 125B includes algorithms
for adjusting power delivery based on impedance measurements of the
fill material 120' introduced to the bone portion. In another
embodiment, the controller 125B includes algorithms for adjusting
power delivery based on the volume of bone fill material 120
delivered to the bone portion. In still another embodiment, the
controller 125B includes algorithms for adjusting power delivery
based on the temperature of the bone fill material 120' introduced
to the bone portion.
[0083] FIGS. 5A and 5B are views of a vertebra 90 that are useful
for explaining relevant aspects of one embodiment of the invention
wherein working end 110A is advanced into the region of the
fracture 94 in the cancellous bone 122. FIG. 5A indicates system
100 being used to inject flow material 120' into the vertebra with
the flow material having a viscosity similar to conventional
vertebroplasty or kyphoplasty, for example having the consistency
of toothpaste. FIG. 5A depicts the situation wherein high pressure
injection of a low viscosity material can simply follow paths of
least resistance along a recent fracture plane 160 to migrate
anteriorly in an uncontrolled manner. The migration of fill
material could be any direction, including posteriorly toward the
spinal canal or into the disc space depending on the nature of the
fracture.
[0084] FIG. 5B illustrates system 100 including actuation of the Rf
source 125A by the controller 125B to contemporaneously heat the
fill material to eject altered fill material 120' with a selected
higher viscosity into cancellous bone 122, such as the viscosities
described above. With a selected higher viscosity, FIG. 5B depicts
the ability of the system to prevent extravasion of fill material
and to controllably permeate and interdigitate with cancellous bone
122, rather than displacing cancellous bone, with a plume 165 that
engages cortical bone vertebral endplates 166a and 166b. The fill
material broadly engages surfaces of the cortical endplates to
distribute pressures over the endplates. In a preferred embodiment,
the fill material controllably permeates cancellous bone 122 and is
ejected at a viscosity adequate to interdigitate with the
cancellous bone 122. Fill material with a viscosity in the range of
between about 100,000 cps to 2,000,000 cps may be ejected, though
even lower or higher viscosities may also be sufficient. The Rf
source may selectively increase the viscosity of the fill material
by about 10% or more as it is ejected from the introducer 115A. In
other embodiments, the viscosity may be increased by about 20%,
50%, 100%, 500% or 1000% or more.
[0085] Still referring to FIG. 5B, it can be understood that
continued inflows of high viscosity fill material 120' and the
resultant expansion of plume 165 will apply forces on endplates
166a and 166b to at least partially restore the vertebral height of
the vertebra 90. It should be appreciated that the working end 115A
can be translated axially between about the anterior third of the
vertebral body and the posterior third of the vertebral body during
the injection of fill material 120', as well as that the working
end 115A, which can be any of the types described above and shown
in FIGS. 3A-3C, can be rotated.
[0086] FIG. 6 is a schematic view of an alternative embodiment of
system 100 wherein the Rf source 125A and the controller 125B are
configured to multiplex energy delivery to provide additional
functionality. In one mode of operation, the system functions as
described above and depicted in FIGS. 4 and 5B to alter flow
properties of flowable fill material 120' as it is ejected from
working end 115A. As can be seen in FIG. 6, the system further
includes a return electrode or ground pad 170. Thus the system 100
can be operated in a second mode of operation wherein electrodes
132a and 132b (see FIG. 2B) are switched to a common polarity (or
the distal portion of sleeve 123 can comprise such an electrode) to
function in a mono-polar manner in conjunction with the ground pad
170. This second mode of operation advantageously creates high
energy densities about the surface of plume 165 to thereby
ohmically heat tissue at the interface of the plume 165 and the
body structure.
[0087] In FIG. 6, the ohmically heated tissue is indicated at 172,
wherein the tissue effect is coagulation of blood vessels,
shrinkage of collagenous tissue and generally the sealing and
ablation of bone marrow, vasculature and fat within the cancellous
bone. The Rf energy levels can be set at a sufficiently high level
to coagulate, seal or ablate tissue, with the controller delivering
power based, for example, on impedance feedback which will vary
with the surface area of plume 165. Of particular interest, the
surface of plume 165 is used as an electrode with an expanding
wavefront within cancellous bone 122. Thus, the vasculature within
the vertebral body can be sealed by controlled ohmic heating at the
same time that fill material 120' is permeating the cancellous
bone. Within the vertebral body are the basivertebral
(intravertebral) veins which are paired valveless veins connecting
with numerous venous channels within the vertebra (pars
spongiosa/red bone marrow). These basivertebral veins drain
directly into the external vertebral venous plexus (EVVP) and the
superior and inferior vena cava. The sealing of vasculature and the
basivertebral veins is particularly important since bone cement and
monomer embolism has been frequently observed in vertebroplasty and
kyphoplasty cases (see "Anatomical and Pathological Considerations
in Percutaneous Vertebroplasty and Kyphoplasty: A Reappraisal of
the Vertebral Venous System", Groen, R. et al, Spine Vol. 29, No.
13, pp 1465-1471 2004). It can be thus understood that the method
of using the system 100 creates and expands a "wavefront" of
coagulum that expands as the plume 165 of fill material expands.
The expandable coagulum layer 172, besides sealing the tissue from
emboli, contains and distributes pressures of the volume of infill
material 120' about the plume surface.
[0088] The method depicted in FIG. 6 provides an effective means
for sealing tissue via ohmic (Joule) heating. It has been found
that passive heat transfer from the exothermic reaction of a bone
cement does not adequately heat tissue to the needed depth or
temperature to seal intravertebral vasculature. In use, the mode of
operation of the system 100 in a mono-polar manner for ohmically
heating and sealing tissue can be performed in selected intervals
alone or in combination with the bi-polar mode of operation for
controlling the viscosity of the injected fill material.
[0089] In general, one aspect of the vertebroplasty or osteoplasty
method in accordance with one of the embodiments disclosed herein
allows for in-situ control of flows of a flowable fill material,
and more particularly comprises introducing a working end of an
introducer sleeve into cancellous bone, ejecting a volume of
flowable fill material having a selected viscosity and
contemporaneously applying energy (e.g., Rf energy) to the fill
material from an external source to thereby increase the viscosity
of at least portion of the volume to prevent fill extravasion. In a
preferred embodiment, the system increases the viscosity by about
20% or more. In another preferred embodiment, the system increases
the viscosity by about 50% or more.
[0090] In another aspect of one embodiment of a vertebroplasty
method, the system 100 provides means for ohmically heating a body
structure about the surface of the expanding plume 165 of fill
material to effectively seal intravertebral vasculature to prevent
emboli from entering the venous system. The method further provides
an expandable layer of coagulum about the infill material to
contain inflow pressures and distribute further expansion forces
over the vertebral endplates. In a preferred embodiment, the
coagulum expands together with at least a portion of the infill
material to engage and apply forces to endplates of the
vertebra.
[0091] Of particular interest, one embodiment of fill material 120
as used in the systems described herein (see FIGS. 2A, 4, 5A-5B and
6) is a composite comprising an in-situ hardenable or polymerizable
cement component 174 and an electrically conductive filler
component 175 in a sufficient volume to enable the composite to
function as a dispersable electrode (FIG. 6). In one type of
composite, the conductive filler component is any biocompatible
conductive metal. In another type of composite, the conductive
filler component is a form of carbon. The biocompatible metal can
include at least one of titanium, tantalum, stainless steel,
silver, gold, platinum, nickel, tin, nickel titanium alloy,
palladium, magnesium, iron, molybdenum, tungsten, zirconium, zinc,
cobalt or chromium and alloys thereof. The conductive filler
component has the form of at least one of filaments, particles,
microspheres, spheres, powders, grains, flakes, granules, crystals,
rods, tubules, nanotubes, scaffolds and the like. In one
embodiment, the conductive filler includes carbon nanotubes. Such
conductive filler components can be at least one of rigid,
non-rigid, solid, porous or hollow, with conductive filaments 176a
illustrated in FIG. 7A and conductive particles 176b depicted in
FIG. 7B.
[0092] In a preferred embodiment, the conductive filler comprises
chopped microfilaments or ribbons of a metal as in FIG. 7A that
have a diameter or a cross-section dimension across a major axis
ranging between about 0.0005'' and 0.01''. The lengths of the
microfilaments or ribbons range from about 0.01'' to 0.50''. The
microfilaments or ribbons are of stainless steel or titanium and
are optionally coated with a thin gold layer or silver layer that
can be deposited by electroless plating methods. Of particular
interest, the fill material 120 of FIG. 7A has an in situ
hardenable cement component 174 than has a first low viscosity and
the addition of the elongated microfilament conductive filler
component 175 causes the composite 120 to have a substantially high
apparent viscosity due to the high surface area of the
microfilaments and its interaction with the cement component 174.
In one embodiment, the microfilaments are made of stainless steel,
plated with gold, and have a diameter of about 12 microns and a
length of about 6 mm. The other dimensions provided above and below
may also be utilized for these microfilaments.
[0093] In another embodiment of bone fill material 120, the
conductive filler component comprises elements that have a
non-conductive core portion with a conductive cladding portion for
providing electrosurgical functionality. The non-conductive core
portions are selected from the group consisting of glass, ceramic
or polymer materials. The cladding can be any suitable conductive
metal as described above that can be deposited by electroless
plating methods.
[0094] In any embodiment of bone fill material that uses particles,
microspheres, spheres, powders, grains, flakes, granules, crystals
or the like, such elements can have a mean dimension across a
principal axis ranging from about 0.5 micron to 2000 microns. More
preferably, the mean dimension across a principal axis range from
about 50 microns to 1000 microns. It has been found that metal
microspheres having a diameter of about 800 microns are useful for
creating conductive bone cement that can function as an
electrode.
[0095] In one embodiment, a conductive filler comprising elongated
microfilaments wherein the fill material has from about 0.5% to 20%
microfilaments by weight. More preferably, the filaments are from
about 1% to 10% by weight of the fill material. In other
embodiments wherein the conductive filler comprises particles or
spheres, the conductive filler can comprise from about 5% of the
total weight to about 80% of the weight of the material.
[0096] In an exemplary fill material 120, the hardenable component
can be any in-situ hardenable composition such as at least one of
PMMA, monocalcium phosphate, tricalcium phosphate, calcium
carbonate, calcium sulphate or hydroxyapatite.
[0097] Referring now to FIGS. 8A and 8B, an alternative method is
shown wherein the system 100 and method are configured for creating
asymmetries in properties of the infill material and thereby in the
application of forces in a vertebroplasty. In FIG. 8A, the pressure
mechanism 150 is actuated to cause injection of an initial volume
or aliquot of fill material 120' that typically is altered in
viscosity in working end 115A as described above--but the method
encompasses flows of fill material having any suitable viscosity.
The fill material 120' is depicted in FIGS. 8A and 8B as being
delivered in a unilateral transpedicular approach, but any
extrapedicular posterior approach is possible as well as any
bilateral posterior approach. The system in FIGS. 8A-8B again
illustrates a vertical plane through the fill material 120' that
flows under pressure into cancellous bone 122 with expanding plume
or periphery indicated at 165. The plume 165 has a three
dimensional configuration as can be seen in FIG. 8B, wherein the
pressurized flow may first tend to flow more horizontally that
vertically. One embodiment of the method of the invention includes
the physician translating the working end 115A of the introducer
110A slightly and/or rotating the working end 115A so that flow
outlets 124a are provided in a selected radial orientation. In a
preferred embodiment, the physician intermittently monitors the
flows under fluoroscopic imaging as described above.
[0098] FIG. 8B depicts a contemporaneous or subsequent
energy-delivery step of the method wherein the physician actuates
the Rf electrical source 125A and controller 125B to cause Rf
current delivery from the at least one electrode emitter 128 to
cause ohmic (Joule) heating of tissue as well as internal heating
of the inflowing fill material 120'. In this embodiment, the
exterior surface of sleeve 123 is indicated as electrode or emitter
128 with the proximal portion of introducer 110A having an
insulator coating 178. The Rf energy is preferably applied in an
amount and for a duration that coagulates tissue as well as alters
a flowability property of surface portions 180 of the initial
volume of fill material proximate the highest energy densities in
tissue.
[0099] In one preferred embodiment, the fill material 120 is
particularly designed to create a gradient in the distribution of
conductive filler with an increase in volume of material injected
under high pressure into cancellous bone 122. This aspect of the
method in turn can be used advantageously to create asymmetric
internal heating of the fill volume. In this embodiment, the fill
material 120 includes a conductive filler of elongated conductive
microfilaments 176a (FIG. 7A). The filaments are from about 2% to
5% by weight of the fill material, with the filaments having a mean
diameter or mean sectional dimension across a minor axis ranging
between about 0.001'' and 0.010'' and a length ranging from about 1
mm to about 10 mm, more preferably about 1 mm to 5 mm. In another
embodiment, the filaments have a mean diameter or a mean dimension
across a minor axis ranging between about 1 micron and 500 microns,
more preferably between about 1 micron and 50 microns, even more
preferably between about 1 micron and 20 microns. It has been found
that elongated conductive microfilaments 176a result in resistance
to flows thereabout which causes such microfilaments to aggregate
away from the most active media flows that are concentrated in the
center of the vertebra proximate to outlet 124a. Thus, the
conductive microfilaments 176a attain a higher concentration in the
peripheral or surface portion 180 of the plume which in turn will
result in greater internal heating of the fill portions having such
higher concentrations of conductive filaments. The active flows
also are controlled by rotation of introducer 110A to eject the
material preferentially, for example laterally as depicted in FIGS.
8A and 8B rather that vertically. The handle 106 of the probe 105
preferably has markings to indicate the rotational orientation of
the outlets 124b.
[0100] FIG. 8A depicts the application of Rf energy in a monopolar
manner between electrode emitter 128 and ground pad 170, which thus
causes asymmetric heating wherein surface portion 180 heating
results in greater polymerization therein. As can be seen in FIG.
8A, the volume of fill material thus exhibits a gradient in a
flowability property, for example with surface region 180 having a
higher viscosity than inflowing material 120' as it is ejected from
outlet 124a. In one embodiment, the gradient is continuous. Such
heating at the plume periphery 165 can create an altered, highly
viscous surface region 180. This step of the method can transform
the fill material to have a gradient in flowability in an interval
of about 5 seconds to 500 seconds with surface portion 180 being
either a highly viscous, flowable layer or an elastomer that is
expandable. In preferred embodiments, the interval of energy
delivery required less than about 120 seconds to alter fill
material to a selected asymmetric condition. In another aspect of
the invention, the Rf energy application for creating the gradient
in flowability also can be optimized for coagulating and sealing
adjacent tissue.
[0101] The combination of the viscous surface portion 180 and the
tissue coagulum 172 may function as an in-situ created stretchable,
but substantially flow-impervious, layer to contain subsequent high
pressure inflows of fill material. Thus, the next step of the
method is depicted in FIG. 8B which includes injecting additional
fill material 120' under high pressure into the interior of the
initial volume of fill material 120 that then has a highly viscous,
expandable surface. The viscous, expandable surface desirably
surrounds cancellous bone so that the subsequent injection of fill
material can expand the fill volume to apply retraction forces on
the vertebra endplates 166a and 166b to provide vertical jacking
forces, distracting cortical bone, for restoring vertebral height,
as indicated by the arrows in FIG. 8B. The system can generate
forces capable of breaking callus in cortical bone about a
vertebral compression fracture when the fracture is less than
completely healed.
[0102] In one embodiment, the method includes applying Rf energy to
create highly viscous regions in a volume of fill material and
thereafter injecting additional fill material 120 to controllably
expand the fill volume and control the direction of force
application. The scope of the method further includes applying Rf
energy in multiple intervals or contemporaneous with a continuous
flow of fill material. The scope of the method also includes
applying Rf energy in conjunction with imaging means to prevent
unwanted flows of the fill material. The scope of the invention
also includes applying Rf energy to polymerize and accelerate
hardening of the entire fill volume after the desired amount of
fill material has been injected into a bone.
[0103] In another embodiment, the method includes creating Rf
current densities in selected portions of the volume of fill
material 120 to create asymmetric fill properties based on
particular characteristics of the vertebral body. For example, the
impedance variances in cancellous bone and cortical bone can be
used to create varied Rf energy densities in fill material 120 to
create asymmetric properties therein. Continued injection of fill
material 120 are thus induced to apply asymmetric retraction forces
against cortical endplates 166a and 166b, wherein the flow
direction is toward movement or deformation of the lower viscosity
portions and away from the higher viscosity portions. In FIGS.
9A-9C, it can be seen that in a vertebroplasty, the application of
Rf energy in a mono-polar manner as in FIG. 6 naturally and
preferentially creates more highly viscous, deeper "altered"
properties in surfaces of the lateral peripheral fill volumes
indicated at 185 and 185' and less viscous, thinner altered
surfaces in the superior and inferior regions 186 and 186' of fill
material 120. This effect occurs since Rf current density is
localized about paths of least resistance which are predominantly
in locations proximate to highly conductive cancellous bone 122a
and 122b. The Rf current density is less in locations proximate to
less conductive cortical bone indicated at 166a and 166b. Thus, it
can be seen in FIG. 9B that the lateral peripheral portions 185 and
185' of the first flows of fill material 120 are more viscous and
resistant to flow and expansion than the thinner superior and
inferior regions. In FIG. 9C, the asymmetrical properties of the
initial flows of fill material 120 allows the continued flows to
apply retraction forces in substantially vertical directions to
reduce the vertebral fracture and increase vertebral height, for
example from VH (FIG. 9B) to VH' in FIG. 9C.
[0104] FIGS. 10A and 10B are schematic views that further depict a
method corresponding to FIGS. 9B and 9C that comprises expanding
cancellous bone for applying retraction forces against cortical
bone, e.g., endplates of a vertebra in a vertebroplasty. As can be
seen in FIG. 10A, an initial volume of flowable fill material 120
is injected into cancellous bone wherein surface region 180 is
altered as described above to be highly viscous or to comprise and
elastomer that is substantially impermeable to interior flows but
still be expandable. The surface region 180 surrounds subsequent
flows of fill material 120' which interdigitate with cancellous
bone. Thereafter, as shown in FIG. 10B, continued high pressure
inflow into the interior of the fill material thereby expands the
cancellous bone 122 together with the interdigitated fill material
120'. As can be seen in FIG. 10B, the expansion of cancellous bone
122 and fill material 120' thus applies retraction forces to move
cortical bone endplates 166a and 166b. The method of expanding
cancellous bone can be used to reduce a bone fracture such as a
vertebral compression fracture and can augment or restore the
height of a fractured vertebra. The system thus can be used to
support retract and support cortical bone, and cancellous bone. The
method can also restore the shape of an abnormal vertebra, such as
one damaged by a tumor.
[0105] After utilizing system 100 to introduce, alter and
optionally harden fill material 120 as depicted in FIGS. 9A-9C and
10A-10B, the introducer 110A can be withdrawn from the bone.
Alternatively, the introducer 110A can have a release or detachment
structure indicated at 190 for de-mating the working end from the
proximal introducer portion as described in co-pending U.S. patent
application Ser. No. 11/130,843, filed May 16, 2005, now U.S. Pub.
No. 2006-0100706, the entirety of which is hereby incorporated by
reference and should be considered a part of this
specification.
[0106] Another system 200 for controlling flow directions and for
creating asymmetric properties is shown in FIGS. 11A and 11B,
wherein first and second introducers 110A and 110B similar to those
described above are used to introduce first and second independent
volumes 202a and 202b of fill material 120 in a bilateral approach.
In this embodiment, the two fill volumes function as opposing
polarity electrodes in contact with electrodes 205a and 205b of the
working ends. Current flow between the electrodes thus operates in
a bi-polar manner with the positive and negative polarities
indicated by the (+) and (-) symbols. In this method, it also can
be seen that the highest current density occurs in the three
dimensional surfaces of volumes 202a and 202b that face one
another. This results in creating the thickest, high viscosity
surfaces 208 in the medial, anterior and posterior regions and the
least "altered" surfaces in the laterally outward regions. This
method is well suited for preventing posterior and anterior flows
and directing retraction forces superiorly and inferiorly since
lateral flow are contained by the cortical bone at lateral aspects
of the vertebra. The system can further be adapted to switch ohmic
heating effects between the bi-polar manner and the mono-polar
manner described previously.
[0107] Now referring to FIG. 12, another embodiment is shown
wherein a translatable member 210 that functions as an electrode is
carried by introducer 110A. In a preferred embodiment, the member
210 is a superelastic nickel titanium shape memory wire that has a
curved memory shape. The member 210 can have a bare electrode tip
212 with a radiopaque marking and is otherwise covered by a thin
insulator coating. In FIG. 12, it can be seen that the introducer
can be rotated and the member can be advanced from a port 214 in
the working end 115A under imaging. By moving the electrode tip 212
to a desired location and then actuating RF current, it is possible
to create a local viscous or hardened region 216 of fill material
120. For example, if imaging indicates that fill material 120 is
flowing in an undesired direction, then injection can be stopped
and Rf energy can be applied to harden the selected location.
[0108] FIG. 13 illustrates another embodiment of the introducer
110A which includes a transition in cross-sectional dimension to
allow for decreased pressure requirements for introducing bone
cement through the length of the introducer 110A. In the embodiment
of FIG. 13, the proximal handle end 106 is coupled to introducer
110A that has a larger diameter proximal end portion 218a that
transitions to a smaller diameter distal end portion 218b
configured for insertion into a vertebral body. The distal end
portion 218b includes exterior threads 220 for helical advancement
and engagement in bone to prevent the introducer 110A from moving
proximally when cement is injected into a vertebral body or other
bone, for example to augment vertebral height when treating a VCF.
The bore that extends through the introducer 110A similarly
transitions from larger diameter bore portion 224a to smaller
diameter bore portion 224b. The embodiment of FIG. 13 utilizes a
bore termination or slot 225 in a sidewall of the working end 115A
for ejecting bone cement at a selected radial angle from the axis
226 of the introducer for directing cement outflows within a
vertebral body.
[0109] Still referring to FIG. 13, the introducer 110A is coupled
to bone cement source 145 and pressure source 150 as described
previously that is controlled by controller 125B. Further, an
energy source 125A (e.g., Rf source) is coupled to an energy
delivery mechanism in the working end 115A for applying energy to a
cement flow within bore 224b. In the embodiment of FIG. 13, the
introducer 110A can be fabricated of a strong reinforced plastic
such a polymide composite with a sleeve electrode 228 in bore 224b
and inward of the bore termination slot 225, similar to electrode
128 depicted in FIG. 3A. The electrode 228 in FIG. 13 is coupled to
Rf source 125A for operating in a mono-polar manner in cooperation
with the return ground pad 170. The controller 125B again is
operatively connected to the Rf source 125A to adjust energy
delivery parameters in response to feedback from a thermocouple 235
in the bore 124b or in response to measuring impedance of the
cement flow. In FIG. 13, the controller 125B further is
operationally connected to an aspiration source 240 that is coupled
to a needle-like introducer sleeve 242 that can be inserted into a
bone to apply suction forces to the interior of vertebra for
relieving pressure in the vertebra and/or extracting fluids, bone
marrow and the like that could migrate into the venous system. The
use of such an aspiration system will be described further
below.
[0110] In FIG. 13, the introducer 110A has a larger diameter bore
224a that ranges from about 4 mm to 10 mm, and preferably is in the
range of about 5 mm to 6 mm. The smaller diameter bore 224b can
range from about 1 mm to 3 mm, and preferably is in the range of
about 1.5 mm to 2.5 mm. The exterior threads 220 can be any
suitable height with single or dual flights configured for gripping
cancellous bone. The thread height and length of the reduced
diameter section 218b are configured for insertion into a vertebra
so that the port 225 can be anteriorly or centrally located in the
vertebral body. The working end 115A further carries a radiopaque
marking 244 for orienting the radial angle of the introducer and
bore termination port 225. In FIG. 13, the radiopaque marking 244
is elongated and surrounds port 225 in the introducer sidewall. The
handle 106 also carries a marking 245 for indicating the radial
angle of port 225 to allow the physician to orient the port by
observation of the handle.
[0111] Now referring to FIGS. 14A-14C, the working end 115A of the
introducer of FIG. 13 is shown after being introduced into
cancellous bone 122 in vertebra 90. FIG. 14A illustrates a
horizontal sectional view of vertebra 90 wherein the bore
termination port 225 is oriented superiorly to direct cement
inflows to apply forces against cancellous bone 122 and the
superior cortical endplate 248 of the vertebra. A method of
delivering bone cement comprises providing a flow source 250 (the
pressure source 150 and cement source 145, in combination, are
identified as flow source 250 in FIG. 13) for bone cement inflows
and a controller 125B for control of the bone cement inflows, and
inflowing the bone cement into a vertebral body wherein the
controller 125B adjusts an inflow parameter in response to a
measured characteristic of the cement. In one embodiment, the
measured characteristic is temperature of the bone cement measured
by thermocouple 235 in the working end 115A. The controller 125B
can be any custom computerized controller. In one embodiment, the
system can utilize a commercially available controller manufactured
by EFD Inc., East Providence, R.I. 02914, USA for flow control,
wherein either a positive displacement dispensing system or an
air-powered dispensing system can be coupled to the flow source
250. In response to feedback from thermocouple 235 that is received
by the controller 125B, any inflow parameter of the bone cement
flow can be adjusted, for example cement injection pressure, the
inflow rate or velocity of the bone cement flows or the
acceleration of a bone cement flow. The controller 125B also can
preferably vary any inflow parameter with time, for example, in
pulsing cement inflows to thereby reduce a vertebral fracture, or
move cancellous or cortical bone (see FIGS. 14A-14B). The cement
120 can be introduced in suitable volumes and geometries to treat
fractures or to prophylactically treat a vertebra.
[0112] In another method corresponding to the invention, the flow
source 250, controller 125B and Rf energy source 125A are provided
as shown in FIG. 13. The controller 125B again is capable of
adjusting any bone cement delivery parameter in response to
impedance and/or temperature. The controller 125B adjusts at least
one cement delivery parameter selected from cement volume,
pressure, velocity and acceleration of the inflowing cement. The
controller 125B also can vary pressure of the inflowing cement or
pulse the cement inflows. In this embodiment, the controller 125B
also is capable of adjusting energy delivered from Rf energy source
125A to the inflowing cement 120 in response to impedance,
temperature, cement viscosity feedback or cement flow parameters to
alter cement viscosity as described above. Cement viscosity can be
calculated by the controller 125B from temperature and pressure
signals. The controller 125B also is capable of being programmed
with algorithms to ramp-up and ramp down power in one or more
steps, or can be programmed to pulse power delivery to the bone
cement 120 (FIGS. 14A-14BA).
[0113] As can be seen in FIGS. 14B and 14C, the inflowing cement
120 can be directed to apply forces against cancellous bone 122 and
the superior cortical endplate 248 of the vertebra, or the working
end can be rotated to introduce cement 120 and apply forces in
other directions. In this embodiment, the extension of the working
end 115A in cancellous bone serves as a support for causing
expansion pressures to be directed substantially in the direction
of cement flows. The method of treating the vertebra includes
translating (by helical advancement) and rotating the introducer
110A to thereby alter the direction of cement introduction. In
another embodiment (not shown), the introducer 110A can comprise an
assembly of first and second concentric sleeves wherein the outer
sleeve has threads 220 for locking the assembly in bone and the
inner sleeve is rotatable to adjust the angular direction of port
225 wherein the sleeves are locked together axially. This
embodiment can be used to intermittently angularly adjust the
direction of cement outflows while helical movement of the outer
sleeve adjusts the axial location of port 225 and the cement
outflows.
[0114] In another method of the invention, referring back to FIG.
14A, the aspiration introducer sleeve 242 can be inserted into the
vertebral body 90, for example through the opposing pedicle. The
controller 125B can be programmed to alter aspiration parameters in
coordination with any bone cement inflow parameter. For example,
the cement inflows can be pulsed and the aspiration forces can be
pulsed cooperatively to extract fluids and potentially embolic
materials, with the pulses synchronized. In one method, the cement
inflows are pulsed at frequency ranging between about 1 per second
and 500 per second with an intense, high acceleration pulse which
causes bone marrow, fat, blood and similar materials to become
susceptible to movement while at the same time the aspiration
pulses are strong to extract some mobile marrow etc into the
aspiration sleeve 242. In FIG. 14A, the aspiration sleeve 242 is
shown with single port in it distal end. It should be appreciated
that an aspiration sleeve 242 that has a plurality of inflow ports
along the length of the sleeve, a sleeve that is curved or can be
of a shape memory alloy (e.g., Nitinol) for introduction in a
curved path in the anterior of posterior region of a vertebral body
as indicated by lines 260 and 260' in FIG. 14A, can also be used.
In another embodiment, the aspiration sleeve can extend through the
introducer 110A or can comprise an outer concentric sleeve around
the introducer 110A.
[0115] FIGS. 15A and 15B illustrates another embodiment of a method
for delivering bone fill material wherein the controller 125B and
pressure source 150 are configured to introduce a flowable cement
into the interior of a vertebra under widely varying velocities and
rates of acceleration to optionally (i) provide first slow flow
rates to allow cement flow and interdigitation into and through
cancellous bone, and (ii) provide second higher flow rates that
disallow cement interdigitation and flow into and through
cancellous bone. At suitable high acceleration and flow velocity,
for example in a pulse of cement flow into bone, the accelerated
flow apply forces to bone substantially across the surface of the
cement plume which can displace cancellous bone rather than
allowing the cement to flow into the cancellous bone.
[0116] FIG. 15A illustrates the system of FIG. 13 in a method of
use wherein the controller 125B and pressure source 150 are
actuated to cause a volume of cement 120 to flow into cancellous
bone 122 under a suitable low pressure to allow the cement to
interdigitate with, and flow into, the cancellous bone. The flow of
cement depicted in FIG. 15A can be accompanied by the application
of aspiration forces as described above.
[0117] FIG. 15B illustrates another aspect of the method wherein
the controller 125B and pressure source 150 are actuated to flow
cement with a high acceleration rate and velocity that disallows
the cement from having time to flow into pores of the cancellous
bone. The acceleration and velocity are selected to disallow cement
interdigitation, which thereby causes the application of force to
bone across the surface of the cement plume 265 (FIG. 15B). The
application of such forces across the surface of cement plume 265
is further enabled by providing a suitable high viscosity cement as
described above, which includes selectively increasing cement
viscosity by means of energy delivery thereto. The method of the
invention can include one or more sequences of flowing cement into
the bone to first cause cement interdigitation (FIG. 15A) and then
to apply expansion forces to the bone by at least one high
acceleration flow (FIG. 15B). Of particular interest, the method of
using high acceleration flows, for example in pulses, causes the
cement volume to apply forces to bone akin to the manner is which a
mechanical expander or balloon expander would apply forces to bone.
That is, expansion forces are applied across the entire surface of
cement plume 265 similar to the manner in which mechanical
instruments apply expanding forces across the bone engaging surface
of the instrument. The methods are adapted for reducing a vertebral
fracture and for selectively applying forces to move cancellous
bone and cortical bone.
Retrograde Sensing Systems and Methods
[0118] FIG. 16 illustrates another embodiment of an introducer 110A
for safe introduction of bone cements into a vertebra that
incorporates a sensing system 280. The sensing system 280 includes
the introducer or cannula 110A with at least one distal port 225
for injection of bone cement into a vertebra 90, as described
previously with respect to FIGS. 13-15B. This sensing system 280
further includes at least one electrode carried about an otherwise
insulative exterior surface 278 of the cannula or introducer 110A.
In the illustrated embodiment, the sensing system 280 has three
electrodes or sensors 280a, 280b, 280c disposed about a surface of
the introducer 110A, but it can be appreciated that more or fewer
such electrodes can be used. In the illustrated embodiment, the
electrodes 280a, 280b, 280c are ring electrodes, however other
configurations are possible. Preferably, the electrodes 280a, 280b,
280c are independently coupled to a low voltage power source 285,
which can be a DC or AC source, and to a controller 286 that allows
for measurement of impedance between a pair of the electrodes 280a,
280b, 280c or between the electrodes 280a, 280b, 280c and another
electrode 288 (in phantom) located in a more proximal location on
the introducer 110A that contacts tissue, or between electrodes
280a, 280b, 280c and a ground pad. Such impedance measurements can
advantageously provide the physician with instant feedback that
indicates whether there in a flow 290 of bone cement 120 along the
cannula 110A (e.g., a retrograde flow). Retrograde flows of cement
can be seen by imaging means, but imaging is typically not
performed continuously during vertebroplasty. Further, the cannula
itself may obscure clear imaging of a cement flow. Such retrograde
cement flows, if unnoticed, could leak through a fracture to
contact nerves and/or the spinal cord. Though the sensors 280a,
280b, 280c in the illustrated embodiment are adapted to measure
impedance, the sensors 280a, 280b, 280c can be adapted to measure
other suitable electrical, chemical or mechanical parameters, such
as temperature, voltage, and reflectance.
[0119] In FIG. 16, it can be seen that the retrograde flow 290 of
bone cement 120 along the cannula 110A passes by, and in one
embodiment may contact, first and second electrodes 280a and 280b,
which will alter the impedance (or other sensed parameter) measured
between the first and second electrodes 280a, 280b from the normal
tissue impedance. The control algorithms advantageously create a
signal to notify the physician of the variation in impedance
measurement. The signal can be a tone, a visual signal such as a
light and or a tactile signal such as a vibrator in the handle of
the introducer 110A. The controller 286 can preferably switch
sensing between various electrodes (e.g., adjacent electrodes or
non-adjacent electrodes) to indicate the location of any migrating
cement. The cement delivery system may use a conductive bone
cement, as described in U.S. application Ser. No. 11/209,035 filed
Aug. 22, 2005, which will have a significantly different impedance
than tissue to allow for easy detection of cement flows. It should
be appreciated that any conventional bone cement will have a
different impedance than bone tissue so that a retrograde flow 290
of conventional bone cement can be detected. The controller 286
algorithms can be configured for any type of bone cement, wherein
each type has a known impedance, reflectance, etc. For example, a
bone cement formula can be provided for use with the controller 286
to measure impedance and detect variations in impedance due to bone
cement flow. In one embodiment, the controller 286 preferably
compares the sensed parameter (e.g., impedance) of the retrograde
flow bone cement with a known value or value range for said
parameter in bone tissue (e.g., vertebral tissue). The known values
for the parameter can be stored in an algorithm or formulas stored
in the controller 286 or in a separate memory. In another
embodiment, the controller 286 can measure impedance (or other
parameter values) of vertebral tissue adjacent at least one of the
electrodes 280a, 280b and compare said measured impedance to a
measured impedance of retrograde bone cement flow adjacent another
of the electrodes 280a, 280b.
[0120] In another embodiment, the feedback from the sensing system
280 of FIG. 16 can be further adapted for actuating a control
mechanism relating to operation of the vertebroplasty system. In
one embodiment, as described in FIGS. 13-15B, the flow of bone
cement is controlled by a controller 125B and pressure source 150.
Feedback from the sensors 280a, 280b, 280c to the controller 286,
which are used to measure impedance, can be used to adjust or
terminate the flow of bone cement from the pressurized source of
bone cement 145.
[0121] In another embodiment, the feedback from the sensing system
280 of FIG. 16 can be adapted to expand an expansion structure 295
(in phantom) about the surface of the cannula to prevent further
bone cement migration. The expansion structure can be a fluid
filled balloon, a thermally expandable polymer that has resistive
or Rf energy applied thereto, or an elastomeric structure that can
be expanded by axially or rotationally moving concentric cannula
sleeves.
[0122] In another embodiment, the sensing system 280 can include a
thermocouple 282 for measuring temperature of media proximate the
exterior surface 278 of the cannula 110A. Such a temperature sensor
can be well insulated from the interior bore of the cannula which
will carry exothermic cement. The sensor system 280 can also
include a light sensor system that can measure and compare a tissue
parameter and a bone cement parameter. For example, a fiber optic
can be provided to emit and/or receive light at the electrode
locations in FIG. 16. Various parameters are possible such as
reflectance. Alternatively, the bone cement can be configured with
signaling compositions to cooperate with light emitted from a light
source.
[0123] While the sensing system 280 has been described with the
sensors being proximal to the cement injection port 225 of the
cannula 110A, the sensors also can be elsewhere along the cannula
110A, for example at the distal end of the cannula 110A, to detect
cement flow in that direction, such as in an anterograde
direction.
[0124] FIG. 17, shows another embodiment of a bone fill introducer
or injector system 310A for treatment of the spine, such as in a
vertebroplasty procedure. Introducer system 310A is used for
placement a fill material from source 145, wherein injection of the
fill material is carried out by the pressure mechanism or source
150. The pressure mechanism 150 can be a manually operated syringe
loaded with bone fill material, or a non-manual pressurized source
of fill material. The source 145 of fill material preferably
includes a coupling or fitting 314 for sealable locking to a
corresponding fitting 315 at a proximal end 316 of an elongated
introducer sleeve or cannula 320. In one embodiment, the source of
fill material 145 is coupled directly to fitting 315 with a
threaded coupling, a Luer lock or the like. In another embodiment
as in FIG. 17, a flexible tube 318 (phantom view) is used to couple
the source 145 to the introducer 320.
[0125] With continued reference to FIG. 17, the bone fill
introducer system 310A includes the elongated sleeve 320 with
interior channel 322 extending along axis 324, wherein the channel
322 terminates in an outlet opening 325. In the illustrated
embodiment, the outlet opening 325 is disposed proximal the distal
end of the elongated sleeve 320 and faces a side of the sleeve 320.
In the illustrated embodiment, the outlet opening 325 is a single
opening. In other embodiments, a plurality of outlet openings can
be disposed on an outward surface 328 of the sleeve 320 about a
circumference of the sleeve 320. In another embodiment, an outlet
opening can be provided at the distal tip 330. In one embodiment,
the distal tip 330 is blunt. In another embodiment, the distal tip
can be sharp as with a chisel-like tip.
[0126] As can be seen in FIG. 17, the exterior surface 328 of the
introducer sleeve 320 carries at least one sensor system 344
adapted to sense the flow or movement of a fill material 345 (see
FIGS. 18A-18C) proximate to the sensor system 344. The introducer
sleeve 320 and sensor system 344 are particularly useful in
monitoring and preventing extravasion of a fill material 345 in a
vertebroplasty procedure. In the illustrated embodiment, the sensor
system 344 comprises a plurality of spaced apart electrodes or
sensors 354a, 354b, 354c coupled to the electrical source 125A via
an electrical connector 356 preferably disposed at the proximal end
of the introducer 320. The electrodes 354a, 354b, 354c are
preferably spaced apart about the circumference of the introducer
320, as well as axially along the length of the introducer 320. The
electrical source 125A preferably carries a low voltage direct
current, such as an Rf current, between the opposing potentials of
spaced apart electrodes. The voltage is preferably between about
0.1 volts to about 500 volts, or from between about 1 volt to about
5 volts, and preferably creates a current path through the tissue
between a pair of electrodes. The current can be continuous,
intermittent and/or multiplexed between different electrode pairs
or groups of electrodes.
[0127] In one embodiment and method of use, referring to FIGS.
18A-18C, the introducer sleeve 320, as shown in FIG. 17, is used in
a conventional vertebroplasty procedure with a single pedicular
access through a vertebra 350. Alternatively, a bi-pedicular access
can be used. The fill material 345 is preferably a bone cement,
such as PMMA, that is injected into cancellous bone 346 within the
interior of a cortical bone surface 348 of the vertebra 350.
[0128] FIGS. 18A-18B show a progressive flow of cement 345 that
exits the introducer sleeve 320 through outlet 325 and into the
interior of the vertebra 350. FIG. 18C depicts a situation that is
known to occur where bone is fractured along the entry path of the
introducer 320, or where the pressurized cement finds the path of
least resistance to be retrograde along the surface of introducer
320. The retrograde flow of cement, as in FIG. 18C, if allowed to
continue, could lead to cement extravasion into the spinal canal
352. In one embodiment, the sensor system 344 is actuated when the
bone cement 345 comes into contact with at least one of the sensors
354a, 354b, 354c of the sensor system 344. In another embodiment,
the sensor system 344 continually monitors the impedance adjacent
the sensors 354a, 354b, 354c of the sensor system 344.
[0129] The arrangement of electrodes 354a, 354b, 354c can be spaced
apart angularly and axially as shown in FIG. 17, or the electrodes
can be ring electrodes (see FIG. 16), helically spaced electrodes,
or the electrodes can be miniaturized electrodes as in
thermocouples, MEMS devices or any combination thereof. The number
of sensors or electrodes can range from about 1 to 100 and can be
adapted to cooperate with a ground pad (e.g., ground pad 170 in
FIG. 13) or other surface portion of sleeve 320. In one embodiment,
the electrodes can include a PTC or NTC material (positive
temperature coefficient of resistance or negative temperature
coefficient of resistance) to thereby function as a thermistor to
allow measurement of temperature, as well as functioning as a
sensor. The sensor system 344 includes the controller 125B, which
measures at least one selected parameter of the current flow to
determine a change in a parameter such as impedance. When the bone
cement 345 (e.g., a non-conductive bone cement material) contacts
one or more electrodes of the sensor system 344, the controller
125B identifies a change in the selected electrical parameter and
generates a signal to the operator. In another embodiment, the
controller 125B identifies a change in the selected parameter when
the bone cement 345 passes proximal one or more of the sensors of
the sensor system 344 and communicates a signal to the operator
corresponding to said change in said selected parameter. Said
selected parameter can be at least one electrical property,
reflectance, fluorescence, magnetic property, chemical property,
mechanical property or a combination thereof.
[0130] Now referring to FIG. 19, another embodiment of a bone fill
system 310B for vertebroplasty procedures is shown. The bone fill
system 310B includes an introducer 320 with a proximal portion 360a
that is larger in cross-section than a distal portion 360b thereof.
This advantageously allows for lower injection pressures since the
cement flow needs to travel a shorter distance through the smallest
diameter distal portion 360b of the introducer 320. In one
embodiment, the distal portion 360b of the introducer 385 can have
a cross section ranging between about 2 mm and 4 mm with a length
ranging between about 40 mm and 60 mm. Similarly, in one embodiment
the proximal portion 360a of the introducer 320 can have a cross
section ranging between about 5 mm and 15 mm, or between about 6 mm
and 12 mm. However the proximal and distal portions 360a, 360b of
the introducer 320 can have other suitable dimensions.
[0131] With continued reference to FIG. 19, the bone fill system
310B also includes a sensing system 365 for detecting a retrograde
flow of bone cement along an outer surface 366 of the introducer
320. In the illustrated embodiment, the sensing system 365 includes
a first and a second electrode 365a, 365b in the form of spaced
apart exposed flat wire surfaces that are disposed on the surface
366 of the distal introducer portion 360b, wherein the introducer
320 includes a surface insulator layer 368. In one embodiment, the
insulator layer 368 covers the entire surface of the distal
introducer portion 360b, and more preferably the entire surface of
the introducer 320, except where the electrodes 365a, 365b are
disposed. In another embodiment, the distal introducer portion 360b
can be a conductive metal introducer portion with a first polarity
electrode that is exposed in cut-out portions of insulator layer
368 and another opposing polarity electrode is disposed on the
surface of the insulator layer 368. In the illustrated embodiment
the electrodes or sensors 365a, 365b have a helical shape and
extend helically along the introducer 320. However, in another
embodiment, the electrodes 365a, 365b can have other suitable
shapes (e.g., ring electrodes). Though FIG. 19 shows two electrodes
365a, 365b, one of ordinary skill in the art will recognize that
more or less than two electrodes can be provided.
[0132] In the illustrated embodiment, the electrodes 365a, 365b are
preferably electrically connected to the energy source 125A and
controller 125B via lead lines (dashed lines). In one embodiment,
the energy source 125A is an Rf electrical source capable of
delivering sufficient Rf energy (i) to coagulate tissue which in
turn will polymerize adjacent bone cement to create a dam to
inhibit retrograde flows, or (ii) to deliver energy to a conductive
bone cement 345 to inhibit retrograde flows. The opposing polarity
electrodes indicated by the (+) and (-) can be spaced apart any
selected distance to thus operate in a bi-polar manner wherein the
depth of tissue coagulation will depend, at least in part, on the
approximate center-to-center or edge-to-edge dimensions of the
positive and negative electrodes. Thus, any such electrode
arrangement can be adapted to both sense retrograde flows and
thereafter deliver energy to such flow in response to at least one
feedback algorithm in the controller 125B. Any suitable type of
external thermal energy emitter that is linked to the sensor system
365 for inhibiting retrograde flows can be used, such as the energy
emitter 128 discussed above with respect to FIG. 2A. The exterior
thermal energy emitter can be a resistively heated emitter, a
resistive coil, a PTC heating element, a light energy emitter, an
inductive heating emitter, an ultrasound source, a microwave
emitter or any other electromagnetic energy emitter or Rf emitter
that cooperates with the bone cement.
[0133] FIG. 20 shows another embodiment of an introducer system 500
that includes a thin wall sleeve or sheath 510 removably slidable
over an injector or introducer 520 (in phantom) used in
conventional vertebroplasty procedures and adapted for ejection of
bone fill material (e.g., bone cement) through an outlet opening
522 (in phantom) at a distal end of the introducer 520. In the
illustrated embodiment, the sheath 510 has an opening 515 formed at
a distal end 518 of the sheath 510, wherein the opening 515
preferably aligns with the opening 522 of the of the introducer 520
when the sleeve 510 is deployed over the introducer 520. In the
illustrated embodiment, the sleeve 510 is preferably a thin-wall
flexible sleeve. For example, the sleeve 510 can be fabricated of
silicone, polyethylene, urethane, polystyrene, or any other
suitable polymer. The sleeve 510 can be elastic and dimensioned for
a substantially tight grip fit about the injector 520. In another
embodiment, the sleeve 510 can include a tacky or adhesive surface
for engaging the injector 520. In another embodiment, the sleeve
510 can be invertable with or without a self-stick surface to roll
over the injector 520 (e.g., as a condom). In another embodiment,
the sleeve 510 can comprise a heat shrink material to shrink over
the injector 520. In another embodiment, the sleeve 510 can be a
thin-wall flexible sleeve that has a large diameter compared to
injector 520 so that the sleeve 510 fits loosely over the injector
520, where the sleeve 510 is adapted to longitudinally fold about
the injector 520 for inserting into a path in the cancellous bone.
Upon any retrograde flow of cement, said thin wall material
advantageously tends to crumple and engage the cancellous bone to
form a mechanical dam to inhibit retrograde flows. In still another
embodiment (not shown), the sleeve can be a thin-wall substantially
rigid or rigid sleeve that can slip over the introducer 520, and be
made of, for example, metal or a hard plastic.
[0134] The system 500 preferably includes a sensor system 560,
which includes a first and second spaced apart electrodes 565a,
565b, similar to the electrodes 365a, 365b described above with
respect to FIG. 19. The electrodes 565a, 565b are preferably
disposed on an outer surface 512 of the sleeve 510. In the
illustrated embodiment, the electrodes or sensors 565a, 565b have a
helical shape and extend helically along the length of the sleeve
510. However, the electrodes 565a, 565b can have any suitable shape
(e.g., ring electrodes). Additionally, any number of electrodes
565a, 565b can be provided.
[0135] With continued reference to FIG. 20, the sensor system 560
includes an electrical connector 570 that connects to a proximal
end 514 of the sleeve 510. The connector 570 is configured for
detachable coupling with electrical leads 572A, 572B that extend to
the electrical or energy source 125a. The electrical leads 572A,
572B preferably are electrically connected to the electrodes 565a,
565b. In one embodiment, the electrodes 565a, 565b can be used to
sense a retrograde flow of bone cement, where the signals (e.g., of
impedance as discussed above) are communicated to the controller
125B, which in turn generates a signal (e.g., visual, tactile,
auditory) to notify the operator of the retrograde flow, as
discussed above. In another embodiment, the sensor system 560 can
operate as an energy-delivery system, where the controller 125B
controls the operation of the energy source 125A to control the
delivery of electricity to the electrodes 565a, 565b to, for
example, polymerize bone cement proximal the sensors 565a, 565b or
coagulate tissue proximal the sensors 565a, 565b, as discussed
above.
Hydraulic Pressure Mechanism
[0136] Returning to FIG. 19, system 310B includes a container of
fill material or source 145' that is pressurized by a pressure
mechanism 150'. The pressure mechanism 150' can be a hydraulic
source. For example, in one embodiment, the hydraulic source can
include a syringe, or plurality of syringes, with a conduit
containing a working fluid therein and connecting the syringe to a
proximal end of the fill material source 145'. The working fluid
can transfer the force generated by the syringe onto a piston 358
(e.g., a floating piston) that travels through a sleeve 145A of the
fill material source 145' to eject fill material from the fill
material source 145' into the introducer 320. In another embodiment
the hydraulic source can comprise a plurality of syringes connected
via conduits having working fluids therein, the force generated by
one syringe transferred through the working fluid onto a piston of
a downstream syringe, and eventually transferred to the piston 358
in the sleeve 145A. In still another embodiment, the hydraulic
mechanism can include a screw pump actuatable to transmit a force
onto a working fluid in a conduit, which in turn transmits said
force onto the piston 358 in the sleeve 145A. However, the pressure
mechanism 150' can comprise other suitable mechanisms.
Temperature Control Systems
[0137] FIG. 21, shows another embodiment of a bone fill delivery
system 310C. The system 310C is similar to the system 310B in FIG.
19, except as noted below. Thus, the reference numerals used to
designate the various components of the system 310C are identical
to those used for identifying the corresponding components of the
system 310B, except as noted below.
[0138] The system 310C can include a sensing system for detecting
retrograde flows of bone cement, as discussed above. Further, the
system 310C preferably includes a cooling system or mechanism 380,
which is shown schematically in FIG. 21. In one embodiment, the
cooling mechanism 380 is carried within the container 145 that
carries the fill material (e.g., PMMA bone cement or similar
in-situ hardening cement) as shown in FIG. 22. In another
embodiment, the cooling mechanism 380 can be disposed about the
container 145. As can be seen in FIG. 21, the electrical source
125A and controller 125B are coupled to the introducer 320 via
leads that are electrically connected to a detachable coupling 382
coupleable to the introducer 320. A stylet 384 is also provided,
preferably having a sharp tip, for use in embodiments where the
introducer 320 has a distal open port 325''.
[0139] The cooling system 380 of FIG. 21 advantageously maintains a
volume of mixed bone cement at a pre-determined temperature to
inhibit acceleration of the exothermic heating thereof, thus
extending the working time of the cement. In one embodiment, as
shown in FIG. 21, the introducer 320 is an independent introducer
320 sized and configured for introducing the bone cement 345 (FIGS.
18A-18C) into the vertebra 350. In the illustrated embodiment, the
bone cement container 145 has a fitting and optional flexible
sleeve connector 388 for providing a substantially sealed and
substantially pressure-tight coupling between the container 145 and
the introducer 320. The connector 388 preferably has a length of
between about 10 mm and about 100 mm and can optionally include a
cooling system disposed therein.
[0140] The cooling system 380 preferably includes at least one of
an active cooling system and a passive cooling system. In one
embodiment, shown in FIG. 21, the cooling system 380 includes a
thermoelectric system with at least one element 390 (e.g., a
Peltier element) in contact with a thermally conductive wall
portion 392 of the container 145. In another embodiment, the
cooling system 380 includes a chilled fluid circulation system with
channels 394 disposed proximate the wall portion 392 of container
145 (See FIG. 22). In another embodiment (not shown) the cooling
system 380 includes a freon system with an expansion channel inside
the wall portion 392 of the container 145. However, the cooling
system 380 can include other suitable active cooling arrangements.
In still another embodiment (not shown), the cooling system 380
includes a heat pipe system with at least one elongate channel or
concentric channel in the wall portion 392 of the container 145,
which wicks heat away from the container 145 to a heat exchanger
component. In yet another embodiment (not shown), the cooling
system 380 is a passive system that includes an open cell graphite
structure for conducting heat away from the container 145 to a heat
exchanger component. In one embodiment, the open cell graphite is
PocoFoam.TM. manufactured by Poco Graphite, Inc. 300 Old Greenwood
Road, Decatur, Tex. 76234.
[0141] With continued reference to FIG. 21, the bone fill injection
system 310C includes the pressure source or mechanism 150', as
discussed above with respect to FIG. 19. In the illustrated
embodiment, the pressure source 150' is a hydraulic mechanism
coupled to the container 145 via flexible or deformable tubing 396
to drive the piston 358.
[0142] As shown in FIG. 21, the controller 125B can be further
coupled to at least one sensing system 440 for determining the
viscosity of the bone cement in the container 145. Preferably, the
sensing system 440 is at least partially disposed in the container
145. The controller 125B preferably includes algorithms for
preventing any flow of bone cement through the introducer 320 until
the cement has reached a pre-determined viscosity.
[0143] In one embodiment, the sensing system 440 includes an
electrical parameter sensing system for querying an electrical
parameter of a polymerizable bone cement to thereby determine its
viscosity. Such an electrical sensor can preferably measure at
least one of capacitance, conductivity and impedance. Another
embodiment of sensing system 440 includes a mechanical parameter
sensing system for measuring a mechanical parameter of the bone
cement. For example, the mechanical parameter sensing system can
query the bone cement by applying an acoustic wave thereto. In
still another embodiment, the sensing system 440 includes an
optical parameter sensing system for determining the viscosity of
the bone cement by measuring an optical parameter of a polymerizing
bone cement. For example, the optical parameter sensing system can
measure reflectance of the bone cement. In another embodiment, the
optical parameter sensing system can acquire an optical signature
of a bone cement that carries a thermochromic composition. In
another embodiment, the sensing system 440 includes a temperature
sensing system for determining the viscosity of the bone cement via
a measured the temperature of a polymerizable bone cement in the
container 145. In still another embodiment, the sensing system 440
includes a strain gauge (not shown) disposed in the container 145
or drive system to determine the viscosity of the cement. In
another embodiment, the sensing system 440 uses a pressure sensor,
such as a MEMS pressure sensor, to determine the viscosity of the
bone cement. Any of the sensing systems described herein can be
configured to query the parameter of the bone cement continuously
or intermittently at any suitable rate.
[0144] With continued reference to FIG. 21, the bone fill injection
system 310C optionally further includes a thermal energy emitter
420 (See FIG. 23A) disposed within an interior channel 424 of the
introducer 320 for heating a flow of bone cement exiting the
introducer 320 through the outlet opening 325, as shown in FIG.
23A. In one embodiment, the thermal energy emitter 420 is an Rf
emitter adapted for heating a conductive bone cement as disclosed
in the following co-pending U.S. patent applications: application
Ser. No. 11/165,652 filed Jun. 24, 2005; application Ser. No.
11/165,651 filed Jun. 24, 2005, now U.S. Pub. No. 2006-0122622;
application Ser. No. 11/196,045 filed Aug. 2, 2005; application
Ser. No. 11/208,448 filed Aug. 20, 2005; and application Ser. No.
11/209,035 filed Aug. 22, 2005, the entire contents of which are
hereby incorporated by reference and should be considered a part of
this specification. In another embodiment, the thermal energy
emitter 420 delivers thermal energy to the bone cement via
conduction in the distal region of the introducer 320. The thermal
energy emitter 420 can be a resistive heat emitter, a light energy
emitter, an inductive heating emitter, an ultrasound source, a
microwave emitter and any other electromagnetic energy emitter to
cooperate with the bone cement.
[0145] In another embodiment, shown in FIG. 23B, the thermal energy
emitter is a resistive heater 420' with a resistive heating element
422. The heating element 422 preferably has a helical
configuration, though other suitable configurations are possible,
such as an axial configuration. Additionally, the heating element
422 is preferably disposed in an interior bore 424 of the
introducer 320 and can optionally be formed from (or coated with) a
positive temperature coefficient material and coupled to a suitable
voltage source to provide a constant temperature heater as is known
in the art. Preferably, the heating element 422 is carried within
an insulative coating 426 on an interior surface of the introducer
320.
[0146] In one embodiment, the thermal energy emitter 420, 420'
raises the temperature of the chilled bone cement to body
temperature or within about 5.degree. C. above or below body
temperature. In another embodiment, thermal energy emitter 420,
420' raises the temperature of the chilled bone cement 345 to at
least about 45.degree. C., at least about 55.degree. C. in another
embodiment, at least about 65.degree. C. in still another
embodiment, and between about 45.degree. C. and 95.degree. C. in
another embodiment to accelerate polymerization of the bone cement
345 and increase the viscosity of a PMMA or similar bone cement. In
another embodiment, the thermal energy emitter 420, 420' raises the
temperature of the chilled bone cement 345 to between about
50.degree. C. and 85.degree. C., or between about 50.degree. C. and
65.degree. C. to accelerate polymerization of bone cement 345.
[0147] In the embodiments illustrated in FIGS. 21, 22 and 23A-B,
the controller 125B preferably controls all parameters associated
with cooling of the bone cement in the container 145, cement
injection pressure and/or flow rate, energy delivery to cement
flows in or proximate the distal end of the introducer 320, sensing
of retrograde flows, and energy delivery to retrograde flows about
the exterior surface of the introducer 320.
[0148] FIG. 22 illustrates another system 310D for delivery of bone
infill material. The system 310D is similar to the system 310B in
FIG. 19, except as noted below. Thus, the reference numerals used
to designate the various components of the system 310D are
identical to those used for identifying the corresponding
components of the system 310B, except as noted below. In the
illustrated embodiment, the arrangement of the electrodes 365a,
365b can be multiplexed between a bi-polar mode and a mono-polar
mode using a remote return electrode (ground pad) 170.
Injector Coatings
[0149] FIGS. 24 and 25 show another embodiment of a bone infill
material delivery system 600, which again comprises a bone cement
injector 620 that extends to a working end 605 thereof. However,
the features described below are applicable to any electrosurgical
probe or other heated probe. The injector 620 has a handle portion
640 and an extension portion 642 with a flow passageway 424
extending therethrough (See FIG. 25). The extension portion 642 is
preferably sized and shaped for use in a vertebroplasty
procedure.
[0150] As shown in FIG. 24, the injector 620 has an exterior
surface that includes a coating 625. The coating 625 preferably
comprises a thin layer of a non-metallic material, such as an
insulative amorphous diamond-like carbon (DLC) or a diamond-like
nanocomposite (DCN). Such coatings advantageously inhibit
scratching (e.g., have high scratch resistance), as well as have
lubricious and non-stick characteristics that are useful in bone
cement injectors configured for carrying electrical current for (i)
impedance sensing purposes; (ii) for energy delivery to bone fill
material; and/or (iii) ohmic heating of tissue, such as the
injectors 110A, 320, 620 discussed herein. In a preferred
embodiment, the coating has a scratch resistance of at least about
10 on the Mohs scale, or above about 12 on the Mohs scale in
another embodiment, or above about 14 on the Mohs scale in still
another embodiment. A surface of the injector can have a lubricious
level represented by a static coefficient of friction of less than
about 0.5 in one embodiment, less than about 0.2 in another
embodiment, and less than about 0.1 in still another embodiment. In
one embodiment, the DLC or DNC coatings can have an overlying layer
of Teflon, or similar material, to provide the desired lubricious
level. For example, when inserting a bone cement injector through
the cortical bone surface of a pedicle and then into the interior
of a vertebra, it is important that the exterior insulative coating
portions do not fracture, chip or scratch to thereby ensure that
the electrical current carrying functions of the injector 110A,
320, 620 are not compromised.
[0151] With continued reference to FIG. 24, the source of bone fill
material 145 is coupleable to the flow passageway 424 of the
introducer 620. In addition, the handle portion 640 of the injector
620 includes a connector 645A that allows for releasable connection
of the injector 620 with an electrical connector 645B coupled to
the electrical or energy source. The extension portion 642 is
preferably sized and shaped for use in a vertebroplasty procedure
and to the controller 125B via an electrical cable 650. The
electrical cable 650 preferably carries current to the working end
605 of the bone cement injector 620. In another embodiment, the
electrical cable 650 can be integrated into and permanently
attached to the handle portion 640 of the injector 620.
[0152] As shown in FIG. 24, the system 600 includes a sensor system
660 that includes a series of electrodes 662 at the working end 605
of the introducer 620. In the illustrated embodiment, the
electrodes 662 are ring-like electrodes, though other suitable
configurations can be used (e.g., helical shaped electrodes).
Though FIG. 24 shows five electrodes 662, the sensor system 660 can
have more or fewer electrodes. In the illustrated embodiment, the
electrodes 662 are defined by circumferential rings of exposed
surfaces of a metal cannula, where the amorphous diamond-like
carbon coating has been removed, for example, by etching. In use,
the low voltage current provide by the electrical source 125A is
coupled to the ring-like electrodes 662 from a second opposing
polarity electrode in the working end 605 (or a remote electrode
such as a ground pad). As bone cement covers the ring-like
electrodes 660, impedance will change to thus allow a signal of
retrograde bone cement migration, as described above, to be
generated and communicated by the controller 125B to the operator.
In one embodiment, the electrical source 125A provides energy to
the electrodes 662 for sensing a retrograde flow. In another
embodiment, the electrical source 125B provides energy to the
electrodes 662 for heating of bone cement (e.g., polymerization of
bone cement( ) or tissue.
[0153] FIG. 25 shows a schematic partial cross-sectional view of
the introducer 620. The introducer 620 in FIG. 25 is similar to the
introducer 320 in FIG. 23B, except as noted below. Thus, the
reference numerals used to designate the various features of the
introducer 620 are identical to those used for identifying the
corresponding features of the introducer 320, except as noted
below. In the illustrated embodiment, the introducer 620 includes
the thermal energy embitter 420', which includes the resistive
heating element 422, coupled to the electrical source 125A and
controller 125B. The source of fill material 145 provides a flow of
bone infill material (e.g., bone cement) through the flow
passageway 424, which extends through the introducer 620 to the
outlet opening 325. As discussed above, the introducer 620 has the
coating 625 disposed over an outer surface thereof. As shown in
FIG. 25, the introducer 620 also has an amorphous diamond-like
carbon (DLC) or a diamond-like nanocomposite (DCN) coating 630
within the interior passageway 424 of the bone cement injector 620,
though the injector can be of any type described above.
[0154] Suitable amorphous diamond-like carbon coatings and
diamond-like nanocomposites are available from Bekaert Progressive
Composites Corporations, 2455 Ash Street, Vista, Calif. 92081 or
its parent company or affiliates. Further information on said
coatings can be found at:
http://www.bekaert.com/bac/Products/Diamond-like%20coatings.htm,
the contents of which are incorporated herein by reference. The
diamond-like coatings preferably comprise amorphous carbon-based
coatings with high hardness and low coefficient of friction. The
amorphous carbon coatings advantageously exhibit non-stick
characteristics and excellent wear resistance. The coatings are
preferably thin, chemically inert and have a very low surface
roughness. In one embodiment, the coatings have a thickness ranging
between about 0.001 mm and about 0.010 mm. In another embodiment,
the coatings have a thickness ranging between about 0.002 mm and
about 0.005 mm. The diamond-like carbon coatings are preferably a
composite of sp2 and sp3 bonded carbon atoms with a hydrogen
concentration of between about 0% and about 80%. Another suitable
diamond-like nanocomposite coating (a-C:H/a-Si:O; DLN) is made by
Bakaert and is suitable for use in the bone cement injector
described above. The materials and coatings are known by the names
Dylyn.RTM.Plus, Dylyn.RTM./DLC and Cavidur.RTM..
[0155] In another embodiment, the metal-doped amorphous
diamond-like carbon or diamond-like nanocomposite can be used in an
electrosurgical surface of a blade, needle, probe, jaw surface,
catheter working end and the like. In one embodiment, the surface
of a probe or jaw can comprise a pattern of metal-doped amorphous
diamond-like carbon portions and adjacent or surrounding insulative
amorphous diamond-like carbon portions.
[0156] In another embodiment, the amorphous diamond-like carbon or
diamond-like nanocomposite can be used in a high temperature
circuit board. Such a circuit board can comprise any insulative
substrate together with an electrical circuit deposited thereon,
wherein the circuit is of a metal-doped amorphous carbon or
diamond-like nanocomposite. The circuit board can use depositions
of the DLC or DLN that have a thickness ranging between about 1
micron and 10 microns. The width of the electrical circuit paths
have a width of less than about 1000 microns; 100 microns; 10
microns and 1 micron.
[0157] In one embodiment, the electrodes 280a, 280b, 280c, 344,
365, 662 do not come in contact with adjacent tissue due to, for
example, the presence of a coating on an external surface of the
injector 110A, 320, 620, such as coating 625. Accordingly, the
electrodes 280a, 280b, 280c, 344, 365, 662 can preferably sense a
retrograde flow without being in direct contact with bone cement or
tissue, and can direct energy to said bone cement or tissue without
being in direct contact with the same to, for example, coagulate
tissue or polymerize bone cement.
[0158] In another embodiment, energy can be delivered via the
electrodes 280a, 280b, 280c, 344, 365, 662 of the systems described
above to heat surrounding tissue prior to introduction of bone
cement into the vertebra. In another embodiment, energy can be
delivered via the electrodes 280a, 280b, 280c, 344, 365, 662 of the
systems described above to heat surrounding tissue and bone cement
prior to introduction of additional bone cement into the
vertebra.
[0159] The features described herein are further applicable to
cure-on-demand fill materials that can be used for disc nucleus
implants, wherein the conductive fill material is injected to
conform to the shape of a space and wherein Rf current is then
applied to increase the modulus of the material on demand to a
desired level that is adapted for dynamic stabilization. Thus, the
Rf conductive fill material 120, 345 can be engineered to reach a
desired modulus that is less than that of a hardened fill material
used for bone support. In this embodiment, the fill material is
used to support a disc or portion thereof. The cure-on-demand fill
material also can be configured as an injectable material to repair
or patch a disc annulus as when a tear or herniation occurs
[0160] The features described herein are further applicable to
cure-on-demand fill materials that can be used for plastic surgery
and reconstructive surgery wherein the conductive fill material is
injected to conform to a desired shape, for example in facial
plastics for chin implants, nasal implants, check implants or
breast implants and the like.
[0161] The features described herein are further applicable to
cure-on-demand fill material that can be used for injection into a
space between vertebrae for intervertebral fusion. The injection of
fill material can conform to a space created between two adjacent
vertebrae, or can be injected into notches or bores in two adjacent
vertebrae and the intervening space, and then cured by application
of Rf current to provide a substantially high modulus block to
cause bone fusion.
[0162] In any embodiment such as for intervertebral fusion or for
bone support in VCFs, the system can further include the injection
of a gas (such as carbon dioxide) into the fill material before it
is injected from a high pressure source. Thereafter, the gas can
expand to form voids in the fill material as it is cured to create
porosities in the hardened fill material for allowing rapid bone
ingrowth into the fill material.
[0163] The systems described herein can use any suitable energy
source, other that radiofrequency energy, to accomplish the purpose
of altering the viscosity of the fill material 120, 345. The method
of altering fill material can be at least one of a radiofrequency
source, a laser source, a microwave source, a magnetic source and
an ultrasound source. Each of these energy sources can be
configured to preferentially deliver energy to a cooperating,
energy sensitive filler component carried by the fill material. For
example, such filler can be suitable chromophores for cooperating
with a light source, ferromagnetic materials for cooperating with
magnetic inductive heating means, or fluids that thermally respond
to microwave energy.
[0164] The features described herein are further applicable to
additional filler materials, such as porous scaffold elements and
materials for allowing or accelerating bone ingrowth. In any
embodiment, the filler material can comprise reticulated or porous
elements of the types disclosed in co-pending U.S. patent
application Ser. No. 11/146,891, filed Jun. 7, 2005, titled
"Implants and Methods for Treating Bone" which is incorporated
herein by reference in its entirety and should be considered a part
of this specification. Such fillers also can carry bioactive
agents. Additional fillers, or the conductive filler, also can
include thermally insulative solid or hollow microspheres of a
glass or other material for reducing heat transfer to bone from the
exothermic reaction in a typical bone cement component.
[0165] Of course, the foregoing description is that of certain
features, aspects and advantages of the present invention, to which
various changes and modifications can be made without departing
from the spirit and scope of the present invention. Moreover, the
bone treatment systems and methods need not feature all of the
objects, advantages, features and aspects discussed above. Thus,
for example, those skill in the art will recognize that the
invention can be embodied or carried out in a manner that achieves
or optimizes one advantage or a group of advantages as taught
herein without necessarily achieving other objects or advantages as
may be taught or suggested herein. In addition, while a number of
variations of the invention have been shown and described in
detail, other modifications and methods of use, which are within
the scope of this invention, will be readily apparent to those of
skill in the art based upon this disclosure. It is contemplated
that various combinations or subcombinations of these specific
features and aspects of embodiments may be made and still fall
within the scope of the invention. Accordingly, it should be
understood that various features and aspects of the disclosed
embodiments can be combined with or substituted for one another in
order to form varying modes of the discussed bone treatment systems
and methods.
* * * * *
References