Note: Descriptions are shown in the official language in which they were submitted.
CA 02438913 2004-06-14
Attorney Docket No.: 00167-506001
Intervertebral Decompression
This application is a continuation-in-part of U.S. application Ser. No.
10/388,609,
filed March 17, 2003, which is a continuation of U.S. application Ser. No.
09/707,627, filed
Nov. 6, 2000, now U.S. Pat. No. 6,547,810, U.S. application Ser. No.
09/236,816, filed Jan.
25, 1999, now U.S. Pat. No. 6,290,715, and a continuation-in-part of U.S.
application Ser.
Nos. 09/776,186 and 09/776,231, filed Feb. 1, ZOOI, which are continuations of
U.S.
application Ser. No. 09/272,806, filed March 19, 1999, now U.S. Pat. No.
6,258,086, and
claim priority to U.S. application Ser. No. 09/162,704, filed Sep. 29, 1998,
now U.S. Pat. No.
6,099,514, U.S. application Ser. No. 09/153,552, filed Sep. 15, 1998, now U.S.
Pat. No.
6,126,682, and U.S. application Ser. Nos. 08/881,525, 08/881,692 (now U.S.
Pat. No.
6,073,051), Ser. No. 08/881,527 (now U.S. Pat. No. 5,980,504), Ser. No.
08/881,693 (now
U.S. Pat. No. 6,007,570), Ser. No. 08/881,694 (now U.S. Pat. No. 6,095,149)
each filed Ju.n.
24, 1997, and U.S. Provisional Application Nos. 60/047,820, 60/047,841,
60/047,818,
60/047,848 filed May 28, 1997, U.S. Provisional Application No. 60/045,941
filed May 8,
1997, and U.S. Provisional Application Nos. 60/029,734, 60/029,735,
60/029,600,
~5 60/029,602 filed Oct. 23, 1996, a continuation-in-part of U.S. application
Ser. No.
09/876,831 filed June 6, 2001, and a continuation-in-part of U.S. application
Ser. Nos.
09/792,628 filed Feb. 22, 2001 and 09/884,859 filed June 18, 2001, which claim
priority to
U.S. Provisional Application No. 60/185,221 filed Feb. 25, 2000, each of which
is
incorporated herein by reference in its entirety.
2o This invention relates to methods and apparatuses for modifying
intervertebral disc
tissue and more particularly to the treatment of disc herniations and bulges
using
percutaneous techniques to avoid major surgical intervention.
BACKGROUND
Intervertebral disc abnormalities have a high incidence in the population and
may
25 result in pain and discomfort if they impinge on or irritate nerves. Disc
abnormalities may be
the result of trauma, repetitive use, metabolic disorders and the aging
process and include
such disorders but are not limited to degenerative discs. Abnormalities
include (i) localized
tears or fissures in the annulus fibrosus, (ii) localized disc herniations
with contained or
escaped extrusions, and (iii) chronic, circumferential bulging disc.
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Disc fissures occur rather easily after structural degeneration (a part of the
aging
process that may be accelerated by trauma) of fibrous components of the
annulus fibrosus.
Sneezing, bending or just attrition can tear these degenerated annulus fibers,
creating a
fissure. The fissure may or may not be accompanied by extrusion of nucleus
pulposus
material into or beyond the annulus fibrosus. The fissure itself may be the
sole morphological
change, above and beyond generalized degenerative changes in the connective
tissue of the
disc. Even if there is no visible extrusion, biochemicals within the disc may
still irritate
surrounding structures. Disc fissures can be debilitatingly painful. Initial
treatment is
symptomatic, including bed rest, pain killers and muscle relaxants. More
recently spinal
fusion with cages have been performed when conservative treatment did not
relieve the pain.
The fissure may also be associated with a herniation of that portion of the
annulus.
With a contained disc herniation, there are no free nucleus fragments in the
spinal
canal. Nevertheless, even a contained disc herniation is problematic because
the outward
protrusion can press on the spinal nerves or irritate other structures. In
addition to nerve root
15 compression, escaped nucleus pulposus contents may chemically irritate
neural structures.
Current treatment methods include reduction of pressure on the annulus by
removing some of
the interior nucleus pulposus material by percutaneous nuclectomy. However,
complications
include disc space infection, nerve root injury, hematoma formation,
instability of the
adjacent vertebrae and collapse of the disc from decrease in height.
2o Another disc problem occurs when the disc bulges outward circumferentially
in all
directions and not just in one location. Over time, the disc weakens and takes
on a "roll"
shape or circumferential bulge. Mechanical stiffness of the joint is reduced
and the joint may
become unstable. One vertebra may settle on top of another. This problem
continues as the
body ages and accounts for shortened stature in old age. With the increasing
life expectancy
25 of the population, such degenerative disc disease and impairment of nerve
function are
becoming major public health problems. As the disc "roll" extends beyond the
normal
circumference, the disc height may be compromised, foramina with nerve roots
are
compressed. In addition, osteophytes may form on the outer surface of the disc
roll and
further encroach on the spinal canal and foramina through which nerves pass.
This condition
3o is called lumbar spondylosis.
It has been thought that such disc degeneration creates segmental instability
which
disturbs sensitive structures which in turn register pain. Traditional,
conservative methods. of
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treatment include bed rest, pain medication, physical therapy or steroid
injection. Upon
failure of conservative therapy, spinal pain (assumed to be due to
instability) has been treated
by spinal fusion, with or without instrumentation, which causes the vertebrae
above and
below the disc to grow solidly together and form a single, solid piece of
bone. The procedure
is carried out with or without discectomy. Other treatments include discectomy
alone or disc
decompression with or without fusion. Nuclectomy can be performed by removing
some of
the nucleus to reduce pressure on the annulus. However, complications include
disc space
infection, nerve root injury, hematoma formation, and instability of adjacent
vertebrae.
The ability to treat bulging intervertebral spinal discs has been a long
standing
challenge. A common treatment involves surgical intervention by discectomy or
laminectomy procedures. These involve an open procedure and fairly extensive
tissue
disruption. At times these procedures are necessary to treat the pathology,
e.g., for
sequestered fragments of the nucleus pulposus that have escaped the disc.
Other times the
problems caused by disc bulges can be treated through percutaneous procedures
that use
~ 5 needles or cannulae to access the disc and then employ catheter or small
tool based treatment
modes.
These interventions have been problematic in that alleviation of back pain and
radicular pain is unpredictable even if surgery appears successful. In
attempts to overcome
these difficulties, new fixation devices have been introduced to the market,
including but not
20 limited to pedicle screws and interbody fusion cages. Although pedicle
screws provide a
high fusion success rate, there is still no direct correlation between fusion
success and patient
improvement in function and pain. Studies on fusion have demonstrated success
rates of
between 50% and 67% for pain improvement, and a significant number of patients
have more
pain postoperatively. Therefore, different methods of helping patients with
degenerative disc
25 problems need to be explored.
FIGS. 1 (a) and 1 (b) illustrate a cross-sectional anatomical view of a
vertebra and
associated disc and a lateral view of a portion of a lumbar and thoracic
spine, respectively.
Structures of a typical cervical spine (superior aspect) are shown in FICA 1
(a): 104--lamina:
106--spinal cord: 108--dorsal root of spinal nerve; 114--ventral root spinal
nerve; 115--
30 posterior longitudinal ligament: 118--intervertebral disc; 120--nucleus
pulposus; 122--
annulus fibrosus; 124--anterior longitudinal ligament; 126--vertebral body;
128--pedicle;
130--vertebral artery; 132--vertebral veins; 134--superior articular facet;
136--posterior
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lateral portion of the annulus; 138--posterior medial portion of the annulus;
and 142--spinous
process. In FICA 1 (a), one side of the intervertebral disc 118 is not shown
so that the superior
vertebral body 126 can be seen. FICz 1 (b) is a lateral aspect of the lower
portion of a typical
spinal column showing the entire lumbar region and part of the thoracic region
and
displaying the following structures: 118--intervertebral disc; 126--vertebral
body; 142--
spinous process; 170--inferior vertebral notch; 110--spinal nerve; 174--
superior articular
process; 176--lumbar curvature; and 180--sacrum.
The presence of the spinal cord and the posterior portion of the vertebral
body,
including the spinous process, and superior and inferior articular processes,
prohibit
introduction of a needle or trocar from a directly posterior position. This is
important
because the posterior disc wall is the site of symptomatic annulus tears and
disc
protrusions/extrusions that compress or irritate spinal nerves for most
degenerative disc
syndromes. The inferior articular process, along with the pedicle and the
lumbar spinal
nerve, form a small "triangular" window 168 through which introduction can be
achieved
from the posterior lateral approach. FICz 1 (d) looks down on an instrument
introduced by the
posterior lateral approach. It is well known to those skilled in the art that
percutaneous
access to the disc is achieved by placing an introduces into the disc from
this posterior lateral
approach, but the triangular window does not allow much room to maneuver. Once
the
introduces pierces the tough annulus fibrosus, the introduces is fixed at two
points along its
length and has very little freedom of movement. Thus, this approach has
allowed access only
to small central and anterior portions of the nucleus pulposus. Current
methods do not permit
percutaneous access to the posterior half of the nucleus or to the posterior
wall of the disc.
Major and potentially dangerous surgery is required to access these areas.
SUMMARY
It is desirable to diagnose and treat disc abnormalities at locations
previously not
accessible via percutaneous approaches and without substantial destruction to
the disc, and to
provide for a percutaneous procedure that can be performed by non-surgical
specialists
commonly performing spine pain management procedures (interventional
anesthesiologists
and radiologists, etc.), that addresses the symptoms brought on by bulging
discs (i.e.
3o radicular pain that shoots down the leg, sciatica), that is performed
through a small diameter
introduces, and that treats the tissue at the site of the bulge.
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According to one aspect of the invention, a method of delivering energy to an
intervertebral disc includes positioning an energy delivery device adjacent an
inner wall of~
the disc, and shrinking the nucleus pulposus.
Embodiments of this aspect of the invention may include one or more of the
following features.
The method includes positioning an energy delivery element of the device
adjacent: a
bulge in the intervertebral disc. The method includes monitoring temperature
and controlling
energy delivery based on the monitored temperature. The method includes
providing a
catheter having the energy delivery device, introducing the catheter into the
intervertebral
disc, and advancing the catheter along the inner wall of the disc.
According to another aspect of the invention, a device for delivering energy
includes
a catheter with a distal portion configured to be inserted into a patient and
to follow a natural
boundary of a patient tissue, and an energy delivery element located at the
distal portion for
treating tissue.
~5 Embodiments of this aspect of the invention may include one or more of the
following features.
The distal portion includes a braided polymeric material. The catheter has a
proximal
portion including a tube for transmitted torque to the distal portion. The
tube is attached to
the braided polymeric material by a bonding agent.
2o In an illustrated embodiment, the energy delivery element is a resistive
heating coil
having a length, e.g., of about 1.5 cm.
The braided polymeric material is in the form of a tube defining a lumen and
the
energy delivery element and a pair of wires are located within the lumen. The
pair of wires
are spirally wound about a tube. The wires are joined in the distal portion to
form a
25 peripherally located thermocouple.
The distal portion includes an atraumatic tip formed of a heat UV cured
polymer.
The details of one or more embodiments of the invention are set forth in the
accompa-
nying drawings and the description below. Other features, objects, and
advantages of the
invention will be apparent from the description and drawings, and from the
claims.
3o DESCRIPTION OF DRAWINGS
FIG. 1 (a) is a superior cross-sectional anatomical view of a cervical disc
and vertebra.
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FIG. 1 (b) is a lateral anatomical view of the lower spine.
FIG. 1 (c) is a posterior-lateral anatomical view of two lumbar vertebrae and
illustration of the triangular working zone.
FIG. 1 (d) is a superior cross-sectional view of the required posterior
lateral approach.
FIG. 2 is a second cross-sectional view of an intervertebral disc illustrating
a disc
plane of the intervertebral disc and an inferior/superior plane.
FIG. 3(a) is a plan view of an introducer and an instrument of the invention
in which
solid lines illustrate the position of the instrument in the absence of
bending forces and domed
lines indicate the position the distal portion of the instruments would assume
under bending
forces applied to the intradiscal section of the instrument.
FIG. 3(b) is an end view of the handle of the embodiment shown in FIG. 3(a).
FIG. 4 is a cross-sectional view of an intervertebral disc with a portion of
the
intervertebral apparatus of the present invention inserted in the
intervertebral disc.
FIG. 5(a) is a cross-sectional view of the intervertebral segment of the
embodiment of
~5 the invention shown in FIG. 3(a) taken along the line 5(a)-5(a) ofFIG.
3(a).
FIG. 5(b) is a cross-sectional view of the intervertebral segment of a second
embodiment of the present invention having a combined wall/guiding mandrel.
FIG. 6 is a perspective view of an embodiment of an apparatus of the present
invention with a resistive heating coil positioned around an exterior of an
intradiscal section
20 of the catheter.
FIG. 7 is a partial cross-sectional view of an embodiment an apparatus of the
invention illustrating a sensor positioned in an interior of the intradiscal
section of the
catheter.
FIG. 8 is a partial cross-sectional view of an embodiment of the apparatus of
the
25 invention further including a sheath positioned around the resistive
heating coil.
FIG. 9 is a partial cross-sectional view of an embodiment of the apparatus of
FIG. 6
with multiple resistive heating coils.
FIG. 10 is a plan view of an embodiment of the intradiscal section of a
catheter of the
invention with a helical structure.
3o FIG. 11 is a block diagram of an open or closed loop feedback system that
couples
one or more sensors to an energy source.
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FIG. 12 is a block diagram of an embodiment illustrating an analog amplifier,
analog
multiplexes and microprocessor used with the feedback control system of FIG.
11.
FIG. 13 is an illustration of a decompression catheter treating a bulge in a
disc.
FIG. 14 is a cross-sectional view of the decompression catheter.
FICz 15 is a cross-sectional view of a distal region of the decompression
catheter.
FIG 16 is another cross-sectional view of the distal region of the
decompression
catheter.
FIG. 17 is a cross-sectional view of a middle region of the decompression
catheter.
DETAILED DESCRIPTION
The present invention provides method and apparatus for treating
intervertebral disc
disorders, particularly fissures of the annulus fibrosus, which may or may not
be
accompanied with contained or escaped extrusions, herniations, and bulges.
In general, an apparatus of the invention is in the form of an externally
guidable
intervertebral disc apparatus for accessing and manipulating disc tissue
present at a selected
~ 5 location of an intervertebral disc having a nucleus pulposus and an
annulus fibrosus, the
annulus having an inner wall. Use of a temperature-controlled energy delivery
element,
combined with the navigational control of the inventive catheter, provides
preferential,
localized heating to treat the fissure. For ease of reference to various
manipulations and
distances described below, the nucleus pulposus can be considered as having a
given
2o diameter in a disc plane between opposing sections of the inner wall. This
nucleus pulposus
diameter measurement allows instrument sizes (and parts of instruments)
designed for one:
size disc to be readily converted to sizes suitable for an instrument designed
for a different
size of disc.
The operational portion of the apparatus of the invention is brought to a
location in or
25 near the disc's fissure or bulge using techniques and apparatuses typical
of percutaneous
interventions. For convenience and to indicate that the apparatus of the
invention can be used
with any insertional apparatus that provides proximity to the disc, including
many such
insertional apparatuses known in the art, the term "introduces" is used to
describe this aid to
the method. An introduces has an internal introduces lumen with a distal
opening at a
3o terminus of the introduces to allow insertion (and manipulation) of the
operational parts o:f
the apparatus into (and in) the interior of a disc.
7
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The operational part of the apparatus comprises an elongated element referred
to as a
catheter, various parts of which are located by reference to a distal end and
a proximal end. at
opposite ends of its longitudinal axis. The proximal end is the end closest to
the external
environment surrounding the body being operated upon (which may still be
inside the body
in some embodiments if the catheter is attached to a handle insertable into
the introducer).
The distal end of the catheter is intended to be located inside the disc under
conditions of use.
The catheter is not necessarily a traditional medical catheter (i.e., an
elongate hollow tube for
admission or removal of fluids from an internal body cavity) but is a defined
term for the
purposes of this specification. "Catheter" has been selected as the operant
word to describe;
this part of the apparatus, as the inventive apparatus is a long, flexible
tube which transmila
energy and/or material from a location external to the body to a location
internal to the disc
being accessed upon, such as a collagen solution and heat to the annular
fissure.
Alternatively, material can be transported in the other direction to remove
material from the
disc, such as removing material by aspiration to decrease pressure which is
keeping the
~5 fissure open and aggravating the symptoms due to the fissure.
The catheter is adapted to slidably advance through the introducer lumen, the
cathcaer
having an intradiscal section at the distal end of the catheter, the
intradiscal section being
extendible through the distal opening at the terminus of the introducer into
the disc. Although
the length of the intradiscal portion can vary with the intended function as
explained in detail
2o below, a typical distance of extension is at least one-half the diameter of
the nucleus
pulposus, preferably in the range of one-half to one and one-half times the
circumference of
the nucleus.
In order that the functional elements of the catheter can be readily guided to
the
desired location within a disc, the intradiscal portion of the catheter is
manufactured with
25 sufficient rigidity to avoid collapsing upon itself while being advanced
through the nucleus
pulposus and navigated around the inner wall of the annulus fibrosus. The
intradiscal portion,
however, has insufficient rigidity to puncture the annulus fibrosus under the
same force used
to advance the catheter through the nucleus pulposus and around the inner wall
of the
annulus fibrosus. Absolute penetration ability will vary with sharpness and
stiffness of the; tip
so of the catheter, but in all cases a catheter of the present invention will
advance more readily
through the nucleus pulposus than through the annulus fibrosus.
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In preferred embodiments, the intradiscal section of the catheter further has
differential bending ability in two orthogonal directions at right angles to
the longitudinal
axis. This causes the catheter to bend along a desired plane (instead of at
random). Also wlhen
a torsional (twisting) force is applied to the proximal end of the catheter to
re-orient the distal
end of the catheter, controlled advancement of the catheter in the desired
plane is possible.
A further component of the catheter is a functional element located in the
intradisc,al
section for diagnosis or for adding energy and adding and/or removing material
at the
selected location of the disc where the annular tear, herniation, or bulge is
to be treated. The
apparatus allows the functional element to be controllably guided by
manipulation of the
proximal end of the catheter into a selected location for localized treatment
of the annular
fissure.
The method of the invention. which involves manipulating disc tissue at the
annular
fissure, herniation, or bulge, is easily carried out with an apparatus of the
invention. An
introduces is provided that is located in a patient's body so that its
proximal end is externall to
~5 the body and the distal opening of its lumen is internal to the body and
(1) internal to the
annulus fibrosus or (2) adjacent to an annular opening leading to the nucleus
pulposus, such
as an annular tear or trocar puncture that communicates with the nucleus
pulposus. The
catheter is then slid into position in and through the introduces lumen so
that the functional
element in the catheter is positioned at the selected location of the disc by
advancing or
2o retracting the catheter in the introduces lumen and optionally twisting the
proximal end of the
catheter to precisely navigate the catheter. By careful selection of the
rigidity of the catheter
and by making it sufficiently blunt to not penetrate the annulus fibrosus, and
by careful
selection of the flexibility in one plane versus the orthogonal plane, the
distal portion of the
catheter will curve along the inner wall of the annulus fibrosus as it is
navigated and is
25 selectively guided to an annular tear, herniation, or bulge at selected
locations) in the disc;.
Energy is applied and/or material is added or removed at the selected location
of the disc via
the functional element.
Each of the elements of the apparatus and method will now be described in more
detail. However, a brief description of disc anatomy is provided first, as
sizes and orientation
30 of structural elements of the apparatus and operations of the method can be
better understood
in some cases by reference to disc anatomy.
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The annulus fibrosus is comprised primarily of tough fibrous material, while
the
nucleus pulposus is comprised primarily of an amorphous colloidal gel. There
is a transition
zone between the annulus fibrosus and the nucleus pulposus made of both
fibrous-tike
material and amorphous colloidal gel. The border between the annulus fibrosus
and the
nucleus pulposus becomes more difficult to distinguish as a patient ages, due
to degenerative
changes. This process may begin as early as 30 years of age. For purposes of
this
specification, the inner wall of the annulus fibrosus can include the young
wall comprised
primarily of fibrous material as well as the transition zone which includes
both fibrous
material and amorphous colloidal gels (hereafter collectively referred to as
the "inner wall of
the annulus fibrosus"). Functionally, that location at which there is an
increase in resistance
to catheter penetration and which is sufficient to cause bending of the distal
portion of the
catheter into a radius less than that of the internal wall of the annulus
fibrosus is considered
to be the "inner wall of the annulus fibrosus".
As with any medical instrument and method, not all patients can be treated,
especially
~5 when their disease or injury is too severe. There is a medical gradation of
degenerative disc
disease (stages 1-5). See, for example, Adams et al., "The Stages of Disc
Degeneration as
Revealed by Discograms," J. Bone and Joint Surgery, 68, 36-41 (1986). As these
grades a:re
commonly understood, the methods of instrument navigation described herein
would
probably not be able to distinguish between the nucleus and the annulus in
degenerative
2o disease of grade 5. In any case, most treatment is expected to be performed
in discs in stages
3 and 4, as stages 1 and 2 are asymptomatic in most patients, and stage 5 may
require disc
removal and fusion.
Some of the following discussion refers to motion of the catheter inside the
disc by
use of the terms "disc plane" "oblique plane" and "cephalo-caudal plane."
These specific
25 terms refer to orientations of the catheter within the intervertebral disc.
Refernng now to
FIG. 2 (which shows a vertical cross-section of a disc), a disc plane 30 of
the intervertebral
disc is generally a plane of some thickness 27 within the nucleus pulposus 120
orthogonal to
the axis formed by the spinal column (i.e., such a disc plane is substantially
horizontal in a
standing human, corresponding to the "flat" surface of a vertebra). A oblique
plane 31
3o extends along any tilted orientation relative to axial plane 30; however,
when the plane is
tilted 90°, such a plane would be substantially vertical in a standing
human and is
referred to as a cephalo-caudal plane. Reference is made to such planes to
describe catheter
to
CA 02438913 2004-06-14
Attorney Docket No.: 00167-506001
movements with respect to the disc plane. In various embodiments, disc plane
30 has a
thickness no greater than the thickness of the intervertebral disc, preferably
a thickness no
greater than 75% of a thickness of the intervertebral disc, and more
preferably a thickness no
greater than SO% of a thickness of the intervertebral disc. Refernng to FIG.
3(a), movement
of the intradiscal portion 16 of catheter 14 is confined within a disc plane
by the physical ~~nd
mechanical properties of the intradiscal portion 16 during advancement of the
catheter when
the bending plane of the catheter is aligned with the disc plane until some
additional force is
applied to the catheter by the physician. A twisting force (which can be
applied
mechanically, electrically, or by any other means) acting on the proximal end
of the catheter
changes the forces acting on the distal end of the catheter so that the plane
of the catheter
bend can be angled relative to the disc plane as the catheter is advanced.
Thus, the physician
can cause the distal end of the catheter to move up or down, depending on the
direction of the
twist.
Turning now to the introduces, a detailed description of an entire apparatus
should not
~ 5 be necessary for those skilled in the art of percutaneous procedures and
the design of
instruments intended for such use. The method of the invention can also be
carned out with
endoscopic instruments, and an endoscopic apparatus having structural parts
that meet the
descriptions set forth in this specification would also be an apparatus of the
invention.
In general, a device of the invention can be prepared in a number of different
forms
2o and can consist (for example) of a single instrument with multiple internal
parts or a series of
instruments that can be replaceably and sequentially inserted into a hollow
fixed instrument
(such as a needle) that guides the operational instruments to a selected
location in or adjacent
to an annular fissure. Because prior patents do not fully agree on how to
describe parts of
percutaneous instruments, terminology with the widest common usage will be
used.
25 The iritroducer, in its simplest form, can consist of a hollow needle-like
device
(optionally f tted with an internal removable obturator or trocar to prevent
clogging during
initial insertion) or a combination of a simple exterior cannula that fits
around a trocar. The
result is essentially the same: placement of a hollow tube (the needle or
exterior cannula after
removal of the obturator or trocar, respectively) through skin and tissue to
provide access
3o into the annulus fibrosus. The hollow introduces acts as a guide for
introducing
instrumentation. More complex variations exist in percutaneous instruments
designed for
other parts of the body and can be applied to design of instruments intended
for disc
11
CA 02438913 2004-06-14
Attorney Docket No.: 00167-506001
operations. Examples of such obturators are well known in the art. A
particularly preferred)
introduces is a 17- or 18-gauge, thin-wall needle with a matched obturator,
which a8er
insertion is replaced with a catheter of the present invention.
Refernng now to the figures, FIGS. 3(a) and 3(b) illustrate one embodiment of
a
catheter 14 for treating discogenic back pain as it would appear inserted into
an introduces
12. The apparatus shown is not to scale, as an exemplary apparatus (as will be
clear from the
device dimensions below) would be relatively longer and thinner; the
proportions used in
FIG. 3(a) were selected for easier viewing by the reader. The distal portion
of an
intervertebral apparatus operates inside an introduces 12 having an internal
introduces lumen
13. A flexible, movable catheter 14 is at least partially positionable in the
introduces lumen
13. Catheter 14 includes a distal end section 16 referred to as the
intradiscal section, which is
designed to be the portion of the catheter that will be pushed out of the
introduces lumen and
into the nucleus pulposus, where movement of the catheter will be controlled
to bring
operational portions of the catheter into the selected locations) with regard
to the annular
~5 tear. In FIG. 3(a), dashed lines are used to illustrate bending of the
intradiscal portion of the
catheter as it might appear under use, as discussed in detail later in the
specification. FIG.
3(b) shows an end view of handle 11 at the proximal end of the catheter, with
the handle 11
having an oval shape to indicate the plane of bending, also discussed in
detail later in the
specification. Other sections and properties of catheter 14 are described
later.
2o For one embodiment suitable for intervertebral discs, the outer diameter of
catheter
14 is in the range of 0.2 to 5 mm, the total length of catheter 14 (including
the portion inside
the introduces) is in the range of 10 to 60 cm, and the length of introduces
12 is in the range
of S to 50 cm. For one preferred embodiment, the catheter has a diameter of 1
mm, an overall
length of 30 cm, and an introduced length of 15 cm (for the intradiscal
section). With an
25 instrument of this size, a physician can insert the catheter for a distance
sufficient to reach
selected locations) in the nucleus of a human intervertebral disc.
FIG. 4 illustrates the anatomy of an intervertebral disc and shows an
apparatus of the
invention inserted into a disc. Structures of the disc are identified and
described by these
anatomical designations: the posterior lateral inner annulus 136, posterior
medial inner
3o annulus 138, annulus fibrosus 122/nucleus pulposus 120 interface, the
annulus/dural interface
146, annulus/posterior longitudinal ligament interface 148, anterior lateral
inner annulus 150,
and the anterior medial inner annulus 152.
12
CA 02438913 2004-06-14
Attorney Docket No.: 00167-506001
Refernng again to FIG. 4, the mechanical characteristics of intradiscal
section 16 of
catheter 14 are selected to have (1) sufficient column strength along the
longitudinal axis o~f
the catheter to avoid collapse of the catheter and (2) different flexural
strengths along the two
axes orthogonal to the longitudinal axis to allow controlled bending of the
catheter. These
parameters make the catheter conformable and guidable along inner wall 22 of
an annulus
fibrosus 122 to reach selected location(s), such as the posterior medial
annulus 138.
Specific mechanical characteristics of particular designs will be described
later in the
examples that follow. Generally, however, the necessary design features can be
selected (i:n
an interrelated fashion) by first providing the intradiscal section of the
catheter with
sufficient column strength to be advanceable through normal human nucleus
pulposus and
around the inner wall of the annulus fibrosus without collapse. Here
"collapse" refers to
bending sufficient to inhibit further advancement at the tip. Advancement of
the tip is
restricted by 1 ) sliding through the normal gelatinous nucleus pulposus, 2)
contacting denser
clumps of nucleus pulposus and 3) curving and advancing along the inner wall
of the
~ 5 annulus. Column strength can be increased in many ways known in the art,
including but not
limited to selecting materials (e.g., metal alloy or plastic) with a high
resistance to bendin~;
from which to form the catheter, forming the structure of the catheter with
elements that add
stiffening (such as bracing), and increasing the thickness of the structural
materials. Colunm
strength can be decreased to favor bending by selecting the opposite
characteristics (e.g., s,oft
2o alloys, hinging, and thin structural elements).
When a catheter collapses, the physician feels an abrupt decrease in
resistance. At
that time, the catheter forms one or more loops or kinks between the tip of
the introducer and
the distal tip of the catheter.
Particularly preferred for annular tears at the posterior of the annulus, the
tip 28 of
25 intradiscal section 16 is biased or otherwise manufactured so that it forms
a pre-bent segment
prior to contact with the annulus fibrosus as shown in FIG. 3(a). The bent tip
will cause the
intradiscal section to tend to continue to bend the catheter in the same
direction as the
catheter is advanced. This enhanced curving of a pre-bent catheter is
preferred for a catheter
that is designed to reach a posterior region of the nucleus pulposus; however,
such a catheter
3o must have sufficient column strength to prevent the catheter from
collapsing back on itsehE
The intradiscal section not only must allow bending around the relatively
stronger
annulus fibrosus in one direction, but also resist bending in the orthogonal
direction to the
13
CA 02438913 2004-06-14
Attorney Docket No.: 00167-506001
plane in which bending is designed to occur. By twisting the proximal end of a
catheter and
thus controlling the orientation of the plane of bending while concurrently
controlling the
advancement of the catheter through the nucleus, a physician can navigate the
catheter and. its
instrumentation within the disc.
The bending stiffness of the intradiscal section as measured in Taber
stiffness units.
(using a length of the inventive catheter as the test strip rather than the
standard dimension,
homogeneous-material test strip) should be in the range of 2-400 units (in a 0-
10,000 unit
range) in the desired bending plane, preferably 3-150 units. In preferred
embodiments,
stiffness is in the range of 4-30 units in the desired bending plane. In all
cases, the bending;
stiffness preferably is 2-20 times higher for bending in the orthogonal
direction.
The column or compressive strength of the intradiscal section (force required
to
buckle a segment whose length is 25 or more times its diameter) is in the
range of 0.05 to 4
kg, preferably 0.05 to 2 kg. In the most preferred embodiments, it is in the
range of 0.1 to 1
kg. In the proximal shaft section (i.e., the part of the catheter proximal to
the intradiscal
~5 section), this strength is in the range of 0.1 to 25 kg, preferably 0.2 to
7 kg. In the most
preferred embodiments, it is in the range of 0.7 to 4 kg.
Returning now to FIG. 4, intradiscal section 16 is guidable and can reach the
posterior, the posterior lateral, and the posterior medial regions of the
posterior wall of the
annulus ftbrosus, as well as other selected sections) on or adjacent to inner
wall 22. In order
2o to move the functional section of the catheter into a desired nucleus
location, intradiscal
section 16 is first positioned in the nucleus pulposus 120 by means of the
introducer.
In most uses, introducer 12 pierces annulus fibrosus 122 and is advanced
through the
wall of the annulus fibrosus into the nucleus pulposus. In such embodiments,
introducer 12 is
then extended a desired distance into nucleus pulposus 120. Catheter 14 is
advanced through
25 a distal end of introducer 12 into nucleus pulpbsus 120. Advancement of the
catheter 14,
combined with increased resistance to advancement at the annulus fibrosus,
causes the tip of
the intradiscal section to bend relative to the longitudinal axis of
introducer 12 when the
intradiscal section contacts the inner wall of the annulus fibrosus 122.
Catheter 14 is
navigated along inner wall 22 of annulus fibrosus 122 to selected sites) of
inner wall 22 o~r
30 within nucleus pulposus 120. For example, intradiscal section 16 can be
positioned in or
adjacent to a fissure or tear 44 of annulus fibrosus 122, or a herniation or
bulge in the nucleus
pulposus.
14
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Attorney Docket No.: 00167-506001
The distal portion 28 of intradiscal section 16 is designed to be incapable of
piercing
the annulus fibrosus 122. The inability of distal portion 28 to pierce the
annulus can be the
result of either shape of the tip 29 or flexibility of distal portion 28, or
both. The tip 29 is
considered sufficiently blunt when it does not penetrate the annulus fibrosus
but is deflected
back into the nucleus pulposus or to the side around the inner wall of the
annulus when the;
tip 29 is advanced. The tip can be made with a freely rotating ball. This
embodiment provides
not only a blunt surface but also a rolling contact to facilitate navigation.
Many percutaneous and endoscopic instruments designed for other purposes can
be
adapted for use in this invention. This permits other functions at the desired
location after the
catheter is advanced to that position. For example, cutting edges and sharp
points can be
present in the distal portion 28 if they can be temporarily masked by a
covering element.
However, such devices must be sufficiently flexible and thin to meet the
design
characteristics described in this specification.
In another embodiment an introduces 12 pierces the skin and reaches an
exterior of
~5 annulus fibrosus 122. A rigid and sharp trocar is then advanced through
introduces 12, to
pierce annulus fibrosus 122 and enter the disc. The trocar is then removed.
and catheter 14. is
advanced through a distal end of introduces 12, following the path created by
the trocar in
annulus fibrosus 122 beyond the end of the introduces. In such cases, the
introduces is
outside the annulus fibrosus 122 and only the catheter with its guidable
distal portion 16 i;>
2o present inside the disc. The physician can manipulate the proximal portion
15 of the catheter
to move the distal portion of the catheter to a selected location for treating
a fissure of the
annulus fibrosus 122.
Catheter 14 is not always pre-bent as shown in FIG. 3(a), but optionally can
includLe a
biased distal portion 28 if desired. "Pre-bent" or "biased" means that a
portion of the catheaer
25 (or other structural element under discussion) is made of a spring-like
material that is bent: in
the absence of external stress but which. under selected stress conditions
(for example, while
the catheter is inside the introduces), is linear. Such a biased distal
portion can be
manufactured from either spring metal or superelastic memory material (such as
TineI®
nickel-titanium alloy, Raychem Corp., Menlo Park Calif.). The introduces (at
least in the case
30 of a spring-like material for forming the catheter) is sufficiently strong
to resist the bending
action of the bent tip and maintain the biased distal portion in alignment as
it passes through
the introduces. Compared to unbiased catheters, a catheter with a biased
distal portion 28
CA 02438913 2004-06-14
Attorney Docket No.: 00167-506001
encourages advancement of intradiscal section 16 substantially in the
direction of the bend
relative to other lateral directions as shown by the bent location of
intradiscal section 16
indicated by dashed lines in FIG. 3(a). Biasing the catheter tip also further
decreases
likelihood that the tip 29 will be forced through the annulus fibrosus under
the pressure used
to advance the catheter.
In addition to biasing a catheter tip prior to insertion into an introducer, a
catheter tip
can be provided that is deflected by mechanical means, such as a wire attached
to one side of
the tip that deflects the tip in the desired direction upon application of
force to the proximal
end of the deflection wire. Any device in which bending of the tip of a
catheter of the
invention is controlled by the physician is "actively steerable." In addition
to a tip that is
actively steerable by action of a wire, other methods of providing a bending
force at the tiI>
can be used, such as hydraulic pressure and electromagnetic force (such as
heating a shaped
memory alloy to cause it to contract). Any of a number of techniques can be
used to provide
selective bending of the catheter in one lateral direction.
~5 Refernng now to FIG. 5(a), a guiding mandrel 32 can be included both to add
rigidlity
to the catheter and to inhibit movement of catheter 14 in the inferior and
superior directions
while positioned and aligned in the disc plane of a nucleus pulposus 120. This
aids the
functions of preventing undesired contact with a vertebra and facilitating
navigation. The
mandrel can be flattened to encourage bending in a plane (the "plane of the
bend")
20 orthogonal to the "flat" side of the mandrel. "Flat" here is a relative
term, as the mandrel c,an
have a D-shaped cross-section, or even an oval or other cross-sectional shape
without a
planar face on any part of the structure. Regardless of the exact
configuration, bending will
preferentially occur in the plane formed by the principal longitudinal axis of
the mandrel a.nd
a line connecting the opposite sides of the shortest cross-sectional dimension
of the mandrel
25 (the "thin" dimension). To provide sufficient resistance to the catheter
bending out of the
desired plane while encouraging bending in the desired plane, the minimum
ratio is 1.25:1
("thickest" to "thinnest" cross-sectional dimensions along at least a portion
of the intradiscal
section). The maximum ratio is 20:1, with the preferred ratio being between
1.5:1 and 16:3,
more preferably between 2:1 and 3.5:1. These ratios are for a solid mandrel
and apply to any
3o material, as deflection under stress for uniform solids is inversely
proportional to the
thickness of the solid in the direction (dimension) in which bending is taking
place. For otlher
16
CA 02438913 2004-06-14
Attorney Docket No.: 00167-SOEi001
types of mandrels (e.g., hollow or non-uniform materials), selection of
dimensions andJor
materials that provide the same relative bending motions under stress are
preferred.
A catheter of the present invention is designed with sufficient torsional
strength
(resistance to twisting) to prevent undesired directional movement of the
catheter. Mandrels
formed from materials having tensile strengths in the range set forth in the
examples of this
specification provide a portion of the desired torsional strength. Other
materials can be
substituted so long as they provide the operational functions described in the
examples and
desired operating parameters.
While the mandrel can provide a significant portion of the column strength,
selective
flexibility, and torsional strength of a catheter, other structural elements
of the catheter also
contribute to these characteristics. Accordingly, it must be kept in mind that
it is the
characteristics of the overall catheter that determine suitability of a
particular catheter for use
in the methods of the invention. For example, a mandrel that does not have
sufficient
torsional strength when acting alone can be combined with another element,
such as anti-
~5 twisting outer sheath 40 or inserting/advancing a second mandrel, to
provide a catheter of the
invention. Similarly, components inside the catheter, such as a heating
element or potting
compound, can be used to strengthen the catheter or provide directional
flexibility at the
locations of these elements along the catheter.
It is not necessary that the guiding mandrel 32 be flattened along its entire
length.
2o Different mandrels can be designed for different sized discs, both because
of variations in
disc sizes from individual to individual and because of variations in size
from disc to disc in
one patient. The bendable portion of the mandrel is preferably sufficient to
allow intradiscal
portion 16 of the catheter to navigate at least partially around the
circumference of the inner
wall of the annulus fibrosus (so that the operational functions of the
catheter can be carried
25 out at desired locations) along the inner wall of the annulus fibrosus).
Shorter bendable
sections are acceptable for specialized instruments. In most cases, a
flattened distal portion of
the mandrel of at least 10 mm, preferably 25 mm, is satisfactory. The
flattened portion can
extend as much as the entire length of the mandrel, with some embodiments
being flattened
for less than 1 S cm, in other cases for less than 10 cm, of the distal end of
the guide mandrel.
3o In preferred embodiments the guide mandrel or other differential bending
control
element is maintained in a readily determinable orientation by a control
element located at:
the proximal end of the catheter. The orientation of the direction of bending
and its amount
17
CA 02438913 2004-06-14
Attorney Docket No.: 00167-SOE~001
can be readily observed and controlled by the physician. One possible control
element is
simply a portion of the mandrel that extends out of the proximal end of the
introducer and
can be grasped by the physician, with a shape being provided that enables the
physician to
determine the orientation of the distal portion by orientation of the portion
in the hand. For
example, a flattened shape can be provided that mimics the shape at the distal
end (optionally
made larger to allow better control in the gloved hand of the physician, as in
the handle 11 of
FIG. 3(b)). More complex proximal control elements capable of grasping the
proximal end of
the mandrel or other bending control element can be used if desired, including
but not limited
to electronic. mechanical, and hydraulic controls for actuation by the
physician.
The guide mandrel can also provide the function of differential flexibility by
varying
the thickness in one or more dimensions (for example, the "thin" dimension,
the "thick"
dimension, or both) along the length of the mandrel. A guide mandrel that
tapers (becomes
gradually thinner) toward the distal tip of the mandrel will be more flexible
and easier to
bend at the tip than it is at other locations along the mandrel. A guide
mandrel that has a
~5 thicker or more rounded tip than more proximal portions of the mandrel will
resist bending; at
the tip but aid bending at more proximal locations. Thickening (or thinning)
can also occur in
other locations along the mandrel. Control of the direction of bending can be
accomplished
by making the mandrel more round. i.e., closer to having 1:1 diameter ratios;
flatter in
different sections of the mandrel; or by varying the absolute dimensions
(increasing or
2o decreasing the diameter). Such control over flexibility allows instruments
to be designed that
minimize bending in some desired locations (such as the location of connector
of an
electrical element to avoid disruption of the connection) while encouraging
bending in other
locations (e.g., between sensitive functional elements). In this manner, a
catheter that is
uniformly flexible along its entire length, is variably flexibility along its
entire length, or has
25 alternating more flexible and less flexible segment(s), is readily obtained
simply by
manufacturing the guide mandrel with appropriate thickness at different
distances and in
different orientations along the length of the mandrel. Such a catheter will
have two or more
different radii of curvature in different segments of the catheter under the
same bending
force.
3o In some preferred embodiments, the most distal 3 to 40 mm of a guide
mandrel is
thinner relative to central portions of the intradiscal section to provide
greater flexibility, v~rith
18
CA 02438913 2004-06-14
Attorney Docket No.: 00167-506001
the proximal 10 to 40 mm of the intradiscal section being thicker and less
flexible to add
column strength and facilitate navigation.
The actual dimensions of the guide mandrel will vary with the stiffness and
tensile
strength of the material used to form the mandrel. In most cases the mandrel
will be formed
from a metal (elemental or an alloy) or plastic that will be selected so that
the resulting
catheter will have characteristics of stiffness and bending that fall within
the stated limits.
Additional examples of ways to vary the stiffness and tensile strength include
transverse
breaks in a material, advance of the material so that it "doubles up,"
additional layers of the
same or different material, tensioning or relaxing tension on the catheter,
and applying
electricity to a memory metal.
As illustrated in FIG. 5(b), in some embodiments of an apparatus of the
invention,
guiding mandrel is combined with at least a portion of the catheter 14 to form
a structure
which provides the functions of both, a wall/mandrel 41. In this figure, the
wall/mandrel 41
of catheter 14 can be varied in dimensions as described in the previous
section of this
~5 specification directed to a separate mandrel, with the same resulting
changes in function. F'or
example, changing the thickness of the wall/mandrel 41 that functions as the
mandrel portion
change, the flexibility and preferred direction of bending of the catheter. In
many cases, the
wall/mandrel 41 will be thinner than other portions of the catheter wall 33 so
that
wall/mandrel 41 controls bending. Alternatively, wall/mandrel 41 can be formed
of a
2o different material than the other portions 33 of the catheter walls (i.e.,
one with a lower
tensile and/or flexural strength) in order to facilitate bending.
Returning now to FIG. 5(a), the guiding mandrel 32 is generally located in the
interior
of catheter 14, where it shares space with other functional elements of the
catheter. For
example and as shown in FIG. 5(a), thermal energy delivery device lumen 34 can
receive any
25 of a variety of different couplings from an energy source 20 to a thermal
energy delivery
device (functional element) further along the catheter, including but not
limited to a wire or
other connector between thermal energy elements. Alternatively or
concurrently, hollow
lumens) 36 for delivery or removal of a fluid or solid connectors for
application of a force; to
a mechanical element can be present, so no limitation should be placed on the
types of
3o energy, force, or material transporting elements present in the catheter.
These are merely
some of the possible alternative functional elements that can be included in
the intradiscal
19
CA 02438913 2004-06-14
Attorney Docket No.: 00167-506001
portion of the catheter. Accordingly, a general description will now be given
of some of the
possible functional elements.
To repair tears or fissures in a disc by operation of the instrument at the
tear location
adjacent to or inside the disc, and to repair herniations and bulges, a
functional element is
provided in or on the catheter to carry out that purpose.
Non-limiting examples of functional elements include any element capable of
aiding
diagnosis, delivering energy, or delivering or removing a material from a
location adjacent:
the element's location in the catheter, such as an opening in the catheter for
delivery of a fluid
(e.g., dissolved collagen to seal the fissure) or for suction, a thermal
energy delivery device
1o (heat source), a mechanical grasping tool for removing or depositing a
solid, a cutting tool
(which includes all similar operations, such as puncturing), a sensor for
measurement of a
function (such as electrical resistance, temperature, or mechanical strength),
or a functional
element having a combination of these functions.
The functional element can be at varied locations in the intradiscal portion
of the
~ 5 catheter, depending on its intended use. Multiple functional elements can
be present such as
multiple functional elements of different types (e.g., a heat source and a
temperature sensor)
or multiple functional elements of the same type (e.g., multiple heat sources
spaced along the
intradiscal portion).
One of the possible functional elements present on intradiscal section 16 is a
thermal
2o energy delivery device 18 having a length, e.g., of about S cm. A variety
of different types of
thermal energy can be delivered including but not limited to resistive heat,
radiofrequency
(RF), coherent and incoherent light, microwave, ultrasound and liquid thermal
jet energies. In
one embodiment, thermal energy delivery device 18 is positioned proximal to
the distal
portion of intradiscal section 16 so that there is no substantial delivery of
energy at the distal
2s portion, which can then perform other functions without being constrained
by being required
to provide energy (or resist the resulting heat).
Some embodiments have an interior infusion lumen 36. Infusion lumen 36 is
configured to transport a variety of different media including but not limited
to electrolytic
solutions (such as normal saline), contrast media (such as Conray meglumine
iothalamate),
3o pharmaceutical agents, disinfectants, filling or binding materials such as
collagens or
cements, chemonucleolytic agents and the like, from a reservoir exterior to
the patient to a
desired location within the interior of a disc (i.e., the fissure). Further,
infusion lumen 36 c,an
CA 02438913 2004-06-14
Attorney Docket No.: 00167-SOEi001
be used as an aspiration lumen to remove nucleus material or excess liquid or
gas (naturally
present, present as the result of a liquefying operation, or present because
of prior
introduction) from the interior of a disc. When used to transport a fluid for
irngation of the;
location within the disc, the infusion lumen is sometimes referred to as an
irrigation lumen.
Infusion lumen 36 can be coupled to a medium reservoir through the catheter.
Included in the particular embodiment shown in this figure is one or more
sensor
lumens 42. An example is a wire connecting a thermal sensor at a distal
portion of the
catheter to control elements attached to a connector in the proximal handle 11
of the catheter.
Also included in the embodiment shown in FIG. S(a) is an optional energy
directing
device 43 including but not limited to a thermal reflector, an optical
reflector, thermal
insulator, or electrical insulator. Energy directing device 43 is configured
to limit thermal
and/or electromagnetic energy delivery to a selected site of the disc and to
leave other
sections of the disc substantially unaffected. Energy directing device 43 can
be positioned on
an exterior surface of catheter intradiscal section 16 and/or catheter 14 as
well as in an
~ 5 internal portion of the catheter intradiscal section 16 and/or catheter
14. For example, the
energy can be directed to the walls of the fissure to cauterize granulation
tissue and to shrink
the collagen component of the annulus, while the nucleus is shielded from
excess heat.
In one embodiment, catheter intradiscal section 16 and/or distal portion 28
are
positionable to selected sites) around and/or adjacent to inner wall 22 of
annulus fibrosus
20 122 for the delivery of therapeutic and/or diagnostic agents including but
not limited to,
electromagnetic energy, electrolytic solutions, contrast media, pharmaceutical
agents,
disinfectants, collagens, cements, chemonucleolytic agents and thermal energy.
Intradiscalf
section 16 is navigational and can reach the posterior, the posterior lateral,
the posterior
medial, anterior lateral, and anterior medial regions of the annulus fibrosus
and nucleus
25 pulposus, as well as selected sections) on or adjacent to inner wall 22.
In a preferred embodiment, intradiscal section 16 is positioned adjacent to
the entire
posterior wall of the disc. Sufficient thermal energy can then be delivered,
for example, to
selectively heat the posterior annulus to cauterize granulation tissue and
shrink the collagen
component of the wall around and adjacent to fissure 44 without undue damage
to other
3o portions of the intervertebral disc, particularly the nucleus. These
actions help close the
fissure in the annulus.
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CA 02438913 2004-06-14
Attorney Docket No.: 00167-SOEi001
In the preferred embodiment of FIG. S(a), markings 38 are visible on the
portion of
the catheter that is located during normal operation outside the body being
acted upon,
particularly for embodiments in which the proximal end of the catheter is
designed to be
directly manipulated by the hand of the physician. Advancement of the catheter
into the
introducer will advance the markings into the introducer. thereby showing how
far the
catheter has been advanced into the nucleus. Such a visible marking 38 can be
positioned on
an exterior surface of the catheter or can be present on an interior surface
and visible throu~,gh
a transparent outer covering or sheath. Preferred are visible markings every
centimeter to aid
the physician in estimating the catheter tip advancement.
If desired, visible markings can also be used to show twisting motions of the
catheter
to indicate the orientation of the bending plane of the distal portion of the
catheter. It is
preferred, however, to indicate the distal bending plane by the shape and feel
of the proximal
end of the catheter assembly. The catheter can be attached to or shaped into a
handle 11 that
fits the hand of the physician and also indicates the orientation of the
distal bending plane.
t5 Both the markings and the handle shape thus act as control elements to
provide control over
the orientation of the bending plane; other control elements, such as plungers
or buttons that
act on mechanical, hydrostatic, electrical, or other types of controls, can be
present in more
complex embodiments of the invention.
Additionally, a radiographically opaque marking device can be included in the
distal
2o portion of the catheter (such as in the tip or at spaced locations
throughout the intradiscal
portion) so that advancement and positioning of the intradiscal section can be
directly
observed by radiographic imaging. Such radiographically opaque markings are
preferred
when the intradiscal section is not clearly visible by radiographic imaging,
such as when the
majority of the catheter is made of plastic instead of metal. A
radiographically opaque
25 marking can be any of the known (or newly discovered) materials or devices
with significant
opacity. Examples include but are not limited to a steel mandrel sufficiently
thick to be
visible on fluoroscopy, a tantalum/polyurethane tip, a gold-plated tip, bands
of platinum,
stainless steel or gold, soldered spots of gold and polymeric materials with
radiographicall;y
opaque filler such as barium sulfate. A resistive heating element or an RF
electrode(s) may
so provide sufficient radio-opacity in some embodiments to serve as a marking
device
A sheath 40 can optionally be positioned around catheter 14. Sheath 40
provides a
flexible surface that is smooth and provides for easy introduction into a
selected area within
22
CA 02438913 2004-06-14
Attorney Docket No.: 00167-SOE~001
the disc. Sheath 40 can be made of a variety of different materials including
but not limited to
polyester, rayon, polyimide, polyurethane, polyethylene, polyamide and
silicone. When
visible markings are present to indicate the advancement of the catheter,
either the sheath
carries the markings, or the sheath is clear to reveal markings underneath.
In one preferred embodiment, thermal energy delivery device 18 is a resistive
heating
device. As illustrated in FIG. 6 a heating coil 46 is positioned around an
exterior of catheter
14. The heating element 46 need not be in the shape of a coil. For instance,
the heating
element can be in the form of a thin flexible circuit which is mountable on or
in substantially
one side of the intradiscal portion of the catheter. Heating element 46 is
powered by a direct
current source 20 (and less preferably a source of alternating current).
Heating element is
made of a material that acts as a resistor. Suitable materials include but are
not limited to
stainless steel, nickel/chrome alloys, platinum, and the like.
Preferably, the heating element is inside the intradiscal section of catheter
14 (FIG.
8). The resistive material is electrically insulated and substantially no
current escapes into the
~ 5 body. With increasing levels of current, element 46 heats to greater
temperature levels.
Additionally, a circuit can be completed substantially entirely at intradiscal
section 16 and a
controllable delivery of thermal energy is achieved. In one embodiment, 2
watts pass through
heating element 46 to produce a temperature of about SS° C. in a
selected target such
as fissure 44, 3 watts produces 65° C., 4 watts produces 75°C.
and so on.
2o In another embodiment, thermal energy delivery device 18 is a
radiofrequency
electrode, such as a band or coil. As illustrated in FIG. 6, RF electrode 46
is positioned on an
exterior of catheter 14. RF electrode 46 is powered by an RF generator. The
electrode is
made of suitable materials including but not limited to stainless steel or
platinum. The RF
electrode is located on intradiscal section of catheter 14. Increasing levels
of current
25 conducted into disc tissue heat that tissue to greater temperature levels.
A circuit can be
completed substantially entirely at intradiscal section 16 (bipolar device) or
by use of a
second electrode attached to another portion of the patient's body (monopolar
device). In
either case, a controllable delivery of RF energy is achieved.
In another embodiment sufficient energy is delivered to the intervertebral
disc to heat
3o and shrink the collagen component of the annulus but not ablate tissue
adjacent to catheter
14.
23
CA 02438913 2004-06-14
Attorney Docket No.: 00167-SOEi001
With a resistive heating device, the amount of thermal energy delivered to the
tissue
is a function of (i) the amount of current passing through heating element 46,
(ii) the length,
shape, and/or size of heating element 46, (iii) the resistive properties of
heating element 46,
(iv) the gauge of heating element 46, and (v) the use of cooling fluid to
control temperature.
All of these factors can be varied individually or in combination to provide
the desired level
of heat. Power supply 20 associated with heating element 46 may he battery
based. Catheter
14 can be sterilized and may be disposable.
Referring now to FIG. 7, a thermal sensor 48 may be positioned in an interior
location
of catheter 14. In another embodiment, thermal sensor 48 is positioned on an
exterior surface
of catheter 14. A thermal sensor can be used to control the delivery of energy
to thermal
energy delivery device 18 (FIG. 12). A potting material can be used to fix the
position of
thermal sensor 48 and provide a larger area from which to average the measured
temperature.
Thermal sensor 48 is of conventional design, including but not limited to a
thermistor; T t~rpe
thermocouple with a copper constant an junction; J type, E type, and K type
thermocouples;
t5 fiber optics; resistive wires; IR detectors; and the like. Optionally,
there may be a lumen 4:Z
(FIG. 5(a)) for the thermal sensor connection.
As illustrated in FIG. 8, a sheath 40 may be used to cover resistive heating
element
46. A plurality of resistive heating elements 46 can be used (FIG. 9) in a
catheter of the
invention.
2o Refernng now to the embodiment shown in FIG. 10, thermal energy delivery
device
18 (FIG. 12) includes one or more resistive heating elements 46 coupled to a
resistive heating
energy source. Resistive heating elements 46 are positioned along intradiscal
section 16
(FIG. 4) at locations where they controllably deliver thermal energy to
selected structures,
including granulation tissue in a fissure 44 (FIG. 4) and the annulus
surrounding the fissure.
25 Resistive heating elements 46 can be segmented and multiplexed so that only
certain resistive
heating elements, or combinations of resistive heating elements are activated
at any one
particular time. Thermal sensor 48 can be positioned between resistive heating
elements 46
and/or at an exterior or interior location of catheter 14 (FIG. 4). In the
embodiment illustrated
in FIG. 10, catheter 14 can be prepared with a wound helical structural
element 49 to increase
3o flexibility and minimize kinking. However, other structures and geometries
are suitable for
catheter 14, including but not limited to a substantially smooth surface (and
specifically
including the devices using an internal guide mandrel as previously
described). For example,
24
CA 02438913 2004-06-14
Attorney Docket No.: 00167-506~001
a sheath can be provided over the heating element, and the guiding mandrel
inside the coil
can be encapsulated in silicone potting material. The tubing flexibility and
the silicone
potting material prevent kinking. Additionally, sheath 40 can be positioned
around catheter
14 and also around resistive heating elements 46 to afford a substantially
smooth surface.
s Resistive heating element 46 can be at least partially covered by a
thermally insulating
material, for example, along one side of the catheter, to selectively heat
disc tissue on the
opposite side.
Referring now to FIGS. 11 and 12, an open or closed loop feedback system 52
couples sensors 48 to energy source 20. As illustrated in FIG. 10, thermal
energy delivery
to device 18 is a resistive heating element 46. It will be appreciated that
the embodiments
illustrated in FIGS. 10 and 11 are readily adaptable to other thermal energy
delivery sources
(e.g., for radiofrequency energy, the resistive heating element is replaced
with insulated RF
probes) and the energy source is an RF generator).
The temperature of the tissue or of element 46 (FIG. 10) is monitored by
sensors 48,
and the output power of energy source 20 adjusted accordingly. The physician
can, if desired,
overnde control system 52. A microprocessor can be included and incorporated
in the closed
or open loop system to switch power on and off, as well as to modulate the
power. The
closed loop system utilizes a microprocessor to serve as a controller 54 which
acts to monitor
the temperature and adjust the power accordingly. Alternatives to the
microprocessor are, for
2o example, analog control circuitry and a logic controller.
With the use of sensors 48 and feedback control system 52, a tissue adjacent
to
resistive heating elements 46 can be maintained at a desired temperature for a
selected period
of time without aberrant high temperature fluctuations. Each resistive heating
element 46 can
be connected to separate control and power supply resources, which generate an
independent
25 output for each resistive heating element 46. For example, a desired
thermal output can be
achieved by maintaining a selected energy at resistive heating elements 46 for
a selected
length of time.
When a resistive heating element 46 is used, current delivered through
resistive
heating element 46 can be measured by current sensor 56. Voltage can be
measured by
so voltage sensor 58. Resistance and power are then calculated at power
calculation device 60.
These values can then be displayed at user interface and display 62. Signals
representative of
power and resistance values are received by a controller 54.
CA 02438913 2004-06-14
Attorney Docket No.: 00167-506001
A control signal is generated by controller 54 that is related to the current
and
voltages. The control signal is used by power circuits 66 to adjust the power
output in an
appropriate amount in order to maintain the desired power delivered at
respective resistive
heating elements 46.
In a similar manner, temperatures detected at sensors 48 provide feedback for
maintaining a selected power. The actual temperatures are measured at
temperature
measurement device 68, and the temperatures are displayed at user interface
and display 6:?.
A control signal is generated by controller 54 that is related to the actually
measured
temperature and a desired temperature. The control signal is used by power
circuits 66 to
adjust the power output in an appropriate amount in order to maintain the
desired temperature
delivered at the respective sensor 48. A multiplexer can be included to
measure current,
voltage, and temperature at the sensors 48, 56 and 58, so that appropriate
energy can be
delivered to resistive heating elements 46.
Controller 54 can be a digital or analog controller or a computer with
software. When
~5 controller 54 is a computer, it can include a CPU coupled through a system
bus. Included in
this system can be a keyboard, a disc drive or other non-volatile memory
system, a display,
and other peripherals, as are known in the art. Also coupled to the bus can be
a program
memory and a data memory.
User interface and display 62 includes operator controls and a display.
Controller 54
2o can be coupled to imaging systems well known in the art.
The output of current sensor 56 and voltage sensor 58 is used by controller 54
to
maintain a selected power level at resistive heating elements 46. A
predetermined profile of
power delivered can be incorporated in controller 54, and a preset amount of
energy to be
delivered can also be profiled.
25 Circuitry, software, and feedback to controller 54 result in process
control and in the
maintenance of the selected power that is independent of changes in voltage or
current.
Control can include (i) the selected power and (ii) the duty cycle (wattage
and on-off times).
These process variables are controlled and varied while maintaining the
desired delivery of
power independent of changes in voltage or current, based on temperatures
monitored at
3o sensors 48.
In the embodiment shown, current sensor 56 and voltage sensor 58 are connected
to
the input of an analog amplifier 70. Analog amplifier 70 can be a conventional
differential
26
CA 02438913 2004-06-14
Attorney Docket No.: 00167-506001
amplifier circuit for use with sensors 48, 56 and 58. The output of analog
amplifier 70 is
sequentially connected by an analog multiplexer 72 to the input of A/D
converter 74. The
output of analog amplifier 70 is a voltage which represents the respective
sensed parameters.
Digitized amplifier output voltages are supplied by A/D converter 74 to
microprocessor 54..
Microprocessor 54 may be a type 68HCII available from Motorola. However, it
will be
appreciated that any suitable microprocessor or general purpose digital or
analog computer
can be used to the parameters of temperature, voltage or current.
Microprocessor 54 sequentially receives and stores digital representations of
temperature. Each digital value received by microprocessor 54 corresponds to
different
t o parameters.
Calculated power and temperature values can be indicated on user interface and
display 62. Alternatively, or in addition to the numerical indication of
power, calculated
power values can be compared by microprocessor 54 with power limits. When the
values
exceed predetermined power or temperature values, a warning can be given on
user interface
~ 5 and display 62, and additionally, the delivery of electromagnetic energy
can be reduced,
modified or interrupted. A control signal from microprocessor 54 can modify
the power level
supplied by energy source 20.
In preferred embodiment of the invention, the materials that make up the
various parts
of an apparatus of the invention have the following characteristics:
ComponentTensile~ Conductivity ResistivityMelt Geometry
StrengthElongationcal/cm~/cm/sec/nS2*m temp. (height,
C.
in MPa C, width,
and/or
dia. )
:in
mm
Mandrel 600-20005-100 N/A N/A N/A height
0.2-2.:3
width
0.05-0.5
Heating 300 20 (min.).025-0.2 500-1500* N/A 0.5-0.5
min.
Element dia.
ConductorN/A N/A 2-1.0 150 max.* N/A 0.1-0.!i
wire dia.
Plastic N/A 25 (min.)N/A N/A 80(min.)0.05-0.2
sheath thickness
Another preferred characteristic is that the minimum ratio of heating element
resistivity to conductor wire resistivity is 6:1; the preferred minimum ratio
of guiding
27
CA 02438913 2004-06-14
Attorney Docket No.: 00167-506001
mandrel height to guiding mandrel width is 2:1. Tensile strength and %
elongation can be
measured according to ASTME8 (tension test of metallic materials).
Conductivity and
resistivity can be determined by procedures to be found in ASTM Vol. 2.03 for
electrothermal properties.
A particularly preferred embodiment of a catheter of the invention can be
prepared
using a covering sheath of polyimide with an outside diameter of 1 mm and a
wall thickness
of 0.05 mm. Such a sheath provides a significant fraction of the stiffness and
torsional
strength appropriate for the catheter. Internal to the polyimide sheath and in
the intradiscal
section of the catheter is a heating coil of insulated nickel/chromium wire
that has an outside
diameter that matches the interior diameter of the polyimide sheath. This
heating coil
provides both heat and additional stiffness to the assembly. Also internal to
the polyimide
sheath on each side of the coil (longitudinally) is a 0.1 mm-walled, 304
stainless-steel,
metallic band whose outer diameter matches the inner diameter of the sheath,
the distal band
having a hemispherical end that exits the end of the polyimide sheath and
creates a blunt tip
~ 5 29 (FIG. 3(a)) at the end of the catheter. These bands provide enhanced
radio-opacity for
fluoroscopic visualization, as well as some of the stiffness of the assembled
apparatus.
Proximal to the proximal metallic band and internal to the sheath is an
additional polyimide
tube 47 (FIG. 5(a)) that increases the stiffness of the catheter in the region
that transitions
from the intradiscal section containing the coil to the rigid proximal
section. Proximal to the
2o second polyimide tube and internal to the sheath is a 304 stainless steel
(fully hard)
hypodermic tube with an outside diameter matching the inside diameter of the
polyimide
sheath and a wall thickness of 0.1 mm. This combination provides the rigidity
needed for a
physician to advance the distal portion of the device inside a nucleus
pulposus and provides
tactile force feedback from the tip to the physician.
25 ~ In some embodiments, inside the bands, coil, hypodermic tube, and both
the
polyimide sheath and internal polyimide tube is a guiding mandrel that extends
from a
proximal handle to tip. In one embodiment, this mandrel is 0.15 mm by 0.5 mm
and formed
from 304 stainless steel. In another embodiment, it is a 0.3 mm diameter 304
stainless steep
wire, with the distal 2.5 cm flattened to 0.2 mm by 0.5 mm.
3o Inside the center of the heating coil is a T-type thermocouple potted with
cyanoacrylate adhesive into a polyimide sheath and located alongside the
mandrel. The
thermocouple wire travels through the coil and hypodermic tube to the handle
at the proximal
28
CA 02438913 2004-06-14
Attorney Docket No.: 00167-506001
end of the apparatus. Two copper conductor wires (36 gauge-insulated with
polyimide) are
soldered to the heating coil and pass through the hypodermic tube and handle
to the proximal
handle's electrical connector, which allows a power supply and feedback
controls to be
connected to electrical elements in the catheter. One embodiment has the
handle fitted with a
s 1-3 meter cable extension ending in an electrical connector to eliminate the
need for a
connector in the handle. This design reduces weight (from connector elements)
on the
proximal end and increases the physician's tactile feedback during device
manipulation.
The entire inside of the catheter in one embodiment is encapsulated with a
silicone
material which removes air (which would insulate the heat created by the
heating coil) and
1o helps support the polyimide sheath to prevent collapse (i.e., increases
stiffness). Instead of
the silicone, another embodiment uses an epoxy which remains flexible after
curing. Strain
relief is provided between the catheter body and the handle with an
elastomeric boot. The
distal end of the catheter is pre-bent 15-30° off the longitudinal axis
of the catheter at about
S-10 mm from the distal tip.
~s The catheter in one embodiment carries visible markings 38 (FIG. 5(a)) on
the
hypodermic tube (with the markings being visible through the polyimide sheath)
to indicate
distance of insertion of the catheter into an introducer and/or distance that
the distal end of
the catheter extends out of the introducer into a disc. The catheter is also
marked both
visually and with tactile relief on its handle to indicate the direction of
bending of the pre-
2o bent tip and biased stiffness.
The guidable apparatus described herein can be used in any of a number of
methods
to treat annular fissures, herniations, and bulges. Specific methods that can
be carned out
with an apparatus of the invention will now be described.
Discs with fissures can be treated non-destructively with or without the
removal of
25 nucleus tissue other than limited desiccation of the nucleus pulposus which
reduces its water
content. Fissures can also be ameliorated by shrinking the collagen component
of the
surrounding annulus to bring the sides closer to their normal position.
Thermal shrinkage o~f
collagen also facilitates ingrowth of collagen which increases annular
stiffness. Fissures can
also be repaired with sealants such as a filler (non-adhesive material that
blocks the opening)
3o and/or bonding material (adhesives or cements) which help seal the tear.
The fissure can also
29
CA 02438913 2004-06-14
Attorney Docket No.: 00167-506001
be treated with global heating of the disc. Most of the heat will be directed
toward the fissure,
but the remainder of the disc will also receive some heat.
In some methods of the invention, bonding materials such as collagen, albumin,
and a
mixture of fibrinogen and thrombin are delivered to the fissure. Collagen from
a variety of
sources can be used (e.g., bovine extracted collagen from Semex Medical,
Frazer Pa., or
human recombinant collagen from Collagen Corp., Palo Alto, Calif.). The
collagen is
injected dissolved or as a fine slurry, after which it gradually thickens (or
may be heated) in
the fissure, where the injected collagen provides a matrix for collagen
disposition by the
body.
A variety of different materials can also be delivered to the fissure,
including but not
limited to electrolyte solutions (i.e. normal saline), contrast media (e.g.,
Conray meglumine
iothalamate), pharmaceutical agents (such as the steroid methylprednisolone
sodium
succinate available from Pharmacia & Upjohn. Kalamazoo, Mich., and
nonsteroidal anti-
inflammatory drugs), chemonucleolytic enzyme (e.g., chymopapain), hydrogel
(such as
~5 disclosed in U.S. Pat. No. 4,478,822), osteoinductive substances (e.g.,
BMP, see U.S. Pat.
No. 5,364,839), chondrocyte inductive substance (e.g., TGF-.beta.) and the
like. The
materials are delivered via the catheter and/or introducer to the disc.
Preferably, however,
when precision placement of the material (as in a fissure) is necessary or
desired, the delivery
method uses the apparatus described above, especially when delivery to the
posterior,
2o posterior lateral, or posterior medial region of the disc is desired. The
materials may be
administered simultaneously or sequentially, such as beginning with an
electrolytic solution
(which helps the physician view the pathology) and following with products to
seal a fissure.
The materials are delivered in an amount sufficient to decrease the extent of
the
fissure at least partially, preferably to fill the fissure completely. The
delivered material ca:n
25 be fixed in position with an adhesive, with a hydrogel that is liquid at
room temperature gels
at body temperature, with naturally occurring processes (such as interaction
of fibrinogen and
thrombin) within the disc, or by heating the disc as described in more detail
below.
To seal a fissure, a combination of thrombin and fibrinogen is injected at the
fissure,
after which it coagulates and forms a seal over the fissure. A kit with
appropriate syringes
30 and other equipment is available from Micromedics, Inc., Eagan, Minn.
Frozen fibrinogen
solution is thawed in its plastic bag and then dispensed to a small med cup.
Thrombin is
reconstituted with sterile water in the "slow gel" concentration (100
units/ml) for tissue
CA 02438913 2004-06-14
Attorney Docket No.: 00167-506.001
bonding. For example, 100 ml is added to a vial containing 10,000 units.
Thrombin solution
is withdrawn from the vial and dispensed to a second med cup. The two syringes
are filled
equally, one with each solution. Then the syringe tips are each twisted into
an applicator that
mixes the solutions before passing them to an administration tube. The
syringes are fitted
into the dual syringe holder and the plunger link, which helps the
practitioner administer
equal amounts of thrombin and fibrinogen. Then the practitioner connects the
administration
tube to the proximal end of the inventive catheter, depresses the plungers and
dispenses thc:
sealant solution to the fissure. The thrombin and fibrinogen react and form a
natural seal over
the fissure.
Chymopapain can be injected through the subject catheter, particularly near a
herniation of the disc. Chymopapain splits side chains off proteoglycan
molecules, thereby
decreasing their ability to hold water and their volume. The disc gradually
loses water and
decreases in size. A typical dose is 0.75 to 1.0 ml (2000 pKat/ml).
In some embodiments, thermal energy is delivered to a selected section of the
disc in
an amount that does not create a destructive lesion to the disc, other than at
most a change in
the water content of the nucleus pulposus. In one embodiment there is no
removal and/or
vaporization of disc material positioned adjacent to an energy delivery device
positioned in a
nucleus pulposus. Sufficient thermal energy is delivered to the disc to change
its biochemical
and/or biomechanical properties without structural degradation of tissue.
2o Thermal energy is used to cauterize granulation tissue which is pain
sensitive and
forms in a long-standing tear or fissure. Additionally or alternatively,
thermal energy is used
to seal at least a part of the fissure. To do that, the disc material adjacent
to the fissure is
typically heated to a temperature in the range of 45-70° C. which is
sufficient to shrink
and weld collagen. In one method, tissue is heated to a temperature of at
least SO° C.
for times of approximately one, two, three minutes, or longer, as needed to
shrink the tissue
back into place.
Delivery of thermal energy to the nucleus pulposus removes some water and
permits
the nucleus pulposus to shrink. This reduces a "pushing out" effect that may
have contributed
to the fissure. Reducing the pressure in the disc and repairing the fissure
may help stabilize
3o the spine and reduce pain.
Global heating of the disc also can be used to cauterize the granulation
tissue and seal
the fissure. In this embodiment of the method, the heating element is
positioned away from
31
CA 02438913 2004-06-14
Attorney Docket No.: 00167-SOE>001
the annulus but energy radiates to the annulus to raise the temperature of the
tissue around
the fissure. This global heating method can help seal a large area or multiple
fissures
simultaneously.
Referring to FICA 13, a decompression catheter 200 for treating bulging or
contained
herniated discs, e.g., associated with radicular pain, is a steerable device
that is introduced
into the disc through, e.g., a 17 gauge introduces needle 201 placed using
standard
fluoroscopic techniques. Needle placement of this type is routinely performed
by spine pain
management physicians. This enables the procedure to be an outpatient
procedure performed
by interventionalists in a procedure room setting. The decompression catheter
includes depth
markers (not shown) that aid in proper introduction of the catheter through
the introduces
needle. The decompression catheter is inserted into the nucleus pulposus 202
of the disc 204
on the contralateral side form the target tissue, and then steered to the site
of the bulge 206 by
advancing and twisting the steerable catheter 200, following its progress
using fluoroscopy.
The decompression catheter includes radiopaque markers 290 and 266 (FICA 15)
that help
~5 localize the position of the catheter within the disc.
After the decompression catheter is advanced to the site of the bulge, energy
is
delivered to the site of bulge via the catheter from a radiofrequency
generator (not shown).
The radiofrequency is delivered in the form of resistive heat generated within
a heating coiil
259 (FIG 15) inside the catheter (though other functional elements as
described above can be
2o employed). The temperature at the tip of the catheter is monitored by a
thermocouple 284
(FIG 15) housed within the catheter. The generator uses feedback from the
thermocouple to
control the temperature to a desired level inside the disc. Starting from an
initial temperature
of 50°C, the temperature is ramped up, e.g., every 30 to 60 seconds at
5 degree intervals to a
temperature of 90°C, which is held, e.g., about 6 minutes. The total
treatment time is about
25 13 minutes.
By placing the resistive heating coil at the site of the bulge and delivering
sufficient
energy to heat the disc material to a temperature adequate to shrink collagen
tissue of the
nucleus pulposus and reduce nuclear volume, the catheter allows for
decompression of the
bulge at the site of pathology. The catheter also acts to denervate nerve
fibers in the outer
30 annulus.
32
CA 02438913 2004-06-14
Attorney Docket No.: 00167-506001
Referring to FIG 14, decompression catheter 200 includes a handle 250 from
which a
cable (not shown) extends for connection to the radiofrequency generator, a
torque tube 252,
and a flexible distal section 254. Torque tube 252 is formed, e.g., of a
stainless steel tube
with an outer diameter of 0.045 inches and a wall thickness of 0.0025 inches
to provide
adequate hoop strength such that a torque applied at handle 250 is transmitted
by torque tube
252 to distal section 254. Torque tube 252 has a length, Ll, extending from
handle 250 of,
e.g., about 6.6 inches, and distal section 254 has a length, LZ, of, e.g.,
about 4.9 inches.
Referring also to FIGS. 15 and 16, distal section 254 includes an outer,
flexible tube
256 attached to torque tube 252 by a bonding agent, e.g., epoxy Flexible tube
256 is, e.g., a
braided polymeric material such as a polyimide tube with an embedded stainless
steel braid.
The tube has an outer diameter of 0.038 inches, a wall thickness of 0.0035
inches, and
defines a lumen 258 having a diameter of 0.031 inches. The stainless steel
braid is, e.g., a
flat wire having dimensions of 0.0025" wide by 0.0005 inches thick. The
flexibility of distal
section 254 is selected such that the applied force needed to advance the
catheter through the
~5 nucleus pulposus and along the inner wall of the disc is less than the
force that would
puncture the annulus fibrosus of the disc. The braided sleeve enhances
steerability and
provides for a more rugged catheter that avoids the possibility of damage to
the catheter
during insertion and removal through the introducer needle. The stainless
steel braiding acts
as an armour to help prevent cutting or shearing of the outside of the tube.
The bonding
20 agent enhances torque and steerability of catheter 200 and avoids rippling
of the catheter
surface, enhancing the insertion and removal of the catheter through the
introducer and inside
the disc.
Within lumen 258 is resistive heating coil 259, a delivery wire 260 that
provides the
conduction path from the generator to the heating coil, and a return wire 262
that provides
25 the return conduction path to the generator. Heating coil 259 is, e.g.,
formed from a
polyimide coated 38 gauge wire having an overall diameter of 0.0051 inches.
The heating
coil has an overall length, l, of, e.g., about 1.5 cm to limit the effect of
the heating to the area
of the bulge. Delivery wire 260 is, e.g., an insulated copper wire with a
diameter of 0.005
inches. Return wire 262 is, e.g., a solid stainless steel wire having an
insulating coating of
3o polyimide and a diameter of 0.011 inches. Delivery wire 260 is connected to
coil 259 by,
e.g., a lap solder joint, and return wire 262 is attached to coil 259 by
radiopaque band 266.
Band 266 is, e.g., a stainless steel sleeve soldered to coil 259 and return
wire 262.
33
CA 02438913 2004-06-14
Attorney Docket No.: 00167-506001
Located at the distal end 268 of outer tube 256 is an atraumatic tip 270
formed, e.g.,
of a heat/UV cured polymer such as urethane acrylate. Tip 270 has a reduced
diameter hub
272 that abuts band 266. Hub 272 receives the end 276 of return wire 262.
Located between
coil 259 and outer tube 256 is a sleeve 278, e.g., a polyimide sleeve having
an outer diameter
of 0.025 inches and a wall thickness of 0.001 inches. The material of tip 270
acts like a glue
and is injected into the tip space, effectively potting the space between wire
end 276 and
sleeve 278.
Spirally wound about sleeve 278 are a pair of wires 280, 282, e.g., 44 gauge
wires.
Wires 280, 282 are insulated along their lengths except near the tip where the
wires are
joined to form a thermocouple 284 for measuring temperature. The position of
thermocouple
284 is determined by a sleeve 286, e.g., a polyimide sleeve having an outer
diameter of
0.0294 inches and a wall thickness of 0.0016 inches, that wires 280, 282 abut.
Thermocouple
284 is peripherally located on catheter 200 such that the temperature reading
more accurately
depicts the temperature of the surrounding tissue and allows for more
efficient monitoring of
~5 temperature. This allows for more aggressive shrinkage of the nuclear
tissue at the site of the
bulge.
Radiopaque marker 290, e.g., a platinum/iridium band, is located at the
proximal end
288 of coil 259 and radiopaque band 266 is located at the distal end 289 of
the coil to help
the user determine the position of coil 259 in use. Proximal of marker 290 is
a tube 292, e.g.,
2o a polyimide tube having an outer diameter of 0.021 inches and a wall
thickness of 0.002
inches, that keeps marker 290 from sliding proximally and provides structural
support.
Refernng to FICz 17, prior to being spirally wound, wires 280, 282 are
contained
within a cover 294, e.g., a polyimide tube.
Catheter 200 can include other modifications as described above with reference
to
25 Figs. 3 to 10. The bending stiffness and column or compressive strength of
the distal portion
of catheter 200 can be as described above. The activation elements described
in U.S.
application Ser. No. 09/776,231, supra, can also be incorporated into the
various devices
described above.
All publications and patent applications mentioned in this specification are
herein
3o incorporated by reference in their entirity.
A number of embodiments of the invention have been described. Nevertheless, it
will
be understood that various modifications may be made without departing from
the spirit and
34
CA 02438913 2004-06-14
Attorney Docket No.: 00167-506001
scope of the invention. Accordingly, other embodiments are within the scope of
the
following claims.
