U.S. patent application number 12/584514 was filed with the patent office on 2010-01-07 for rf electrode array for low-rate collagen shrinkage in capsular shift procedures and methods of use.
Invention is credited to James A. Baker.
Application Number | 20100004649 12/584514 |
Document ID | / |
Family ID | 26757782 |
Filed Date | 2010-01-07 |
United States Patent
Application |
20100004649 |
Kind Code |
A1 |
Baker; James A. |
January 7, 2010 |
RF Electrode array for low-rate collagen shrinkage in capsular
shift procedures and methods of use
Abstract
Methods and apparatus are provided for an achieving low-rate
collagen shrinkage using an electrode array comprising an elongated
insulator strip having at least one pair of spaced-apart bi-polar
RF electrodes, and a "channeling" disposed on the strip between the
bi-polar electrodes to direct the flow of RF current therebetween.
The channeling electrode is not directly coupled to the RF power
source, but only indirectly through the tissue in contact with the
channeling electrode. The apparatus enables low RF power levels
(e.g., 0.5 watts to 25 watts) to be applied over time intervals of
5 seconds to 180 seconds to attain low-rate collagen shrinkage by
directing or focusing the path of the RF current.
Inventors: |
Baker; James A.; (Palo Alto,
CA) |
Correspondence
Address: |
Daniel D. Ryan;RYAN KROMHOLZ & MANION, S.C.
Post Office Box 26618
Milwaukee
WI
53226
US
|
Family ID: |
26757782 |
Appl. No.: |
12/584514 |
Filed: |
September 8, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11650887 |
Jan 8, 2007 |
7585297 |
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12584514 |
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10758777 |
Jan 16, 2004 |
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11650887 |
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10141273 |
May 8, 2002 |
6689129 |
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10758777 |
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09750548 |
Dec 28, 2000 |
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10141273 |
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09257359 |
Feb 25, 1999 |
6169926 |
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09750548 |
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60076199 |
Feb 27, 1998 |
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Current U.S.
Class: |
606/33 |
Current CPC
Class: |
A61B 18/14 20130101 |
Class at
Publication: |
606/33 |
International
Class: |
A61B 18/18 20060101
A61B018/18 |
Claims
1. A method of delivering bi-polar RF current from a RF source to
tissue in a medical procedure comprising contacting a first tissue
region with a first bi-polar electrode, contacting a second tissue
region with a second bi-polar electrode spaced apart from the first
bi-polar electrode to form a bi-polar pair of electrodes,
contacting a third tissue region with an electrically conductive
material having an elongated axis spaced intermediate the bi-polar
pair of electrodes, the electrically conductive material being
electrically insulated from the bi-polar pair of electrodes,
coupling the bi-polar pair of electrodes to a source of RF current,
and applying the RF current between the bi-polar pair of electrodes
at a power in a range of about 0.5 to 25 watts for a time period in
a range from about 5 to 180 seconds, the an electrically conductive
material serving to direct a path of RF current generally parallel
to the elongated axis through the third tissue region.
2. The method of claim 1, wherein the RF current is applied between
the bi-polar pair of electrodes at a power in a range of about 2 to
10 watts.
3. The method of claim 1, wherein the RF current is applied between
the bi-polar pair of electrodes for a time period in a range from
about 10 to 60 seconds.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of co-pending U.S.
application Ser. No. 11/650,887, filed 8 Jan. 2007, which is a
continuation of co-pending U.S. application Ser. No. 10/758,777,
filed 16 Jan. 2004 (now abandoned), which is a divisional of U.S.
application Ser. No. 10/141,273, filed 8 May 2002 (now U.S. Pat.
No. 6,689,129), which is a continuation of U.S. application Ser.
No. 09/750,548 filed 28 Dec. 2000 (now abandoned), which is a
continuation of U.S. application Ser. No. 09/257,359 filed 25 Feb.
1999 (now U.S. Pat. No. 6,169,926), which claims the benefit of
U.S. provisional Application Ser. No. 60/076,199, filed 27 Feb.
1998.
FIELD OF THE INVENTION
[0002] This invention relates to RF (radiofrequency) devices and
methods for delivering RF energy to tissue in a patient's body, and
more particularly to an electrode array that allows for controlled
low-power RF energy delivery in orthopedic applications, for
example in capsular shift procedures.
BACKGROUND OF THE INVENTION
[0003] Joint instability in adults is caused by ligaments and
cartridge in a joint becoming lax or stretched, due either to the
aging process or to acute trauma. Joint instability is a widespread
disease and is estimated to affect up to 10 percent of the male
population in the U.S. A patient's shoulder joints, knees, ankles
and elbows all may become unstable due to lax ligaments. As a
specific example, a patient's shoulder joint (or glenohumeral joint
capsule) is maintained in a stable condition by a capsular ligament
complex, subscapular tendons, rotator cuff and teres minor muscles,
among others.
[0004] Joint instability is caused by laxity in the fibrous
ligament complex within the joint capsule. An increase in ligament
laxity may be due to an acute-event type of trauma or recurrent
minor trauma (i.e., wear-and-tear). Often, acute-event trauma
results in a unidirectional type of instability, whereas normal
wear-and-tear results in multidirectional joint instability. In
terms of pathology, unidirectional joint instability may be defined
as an excess capsular volume (space between the humeral head and
synovial surface of the capsule) in a particular location, region
or path across the capsule. Multi-directional joint instability
generally may be considered to be excessive volume within the
entire joint capsule around the humeral head.
[0005] Surgeons have developed open surgical treatments for
reducing the volume of unstable joint capsules, generally termed
"capsular shift procedures". In such surgery, over-stretched or lax
capsular ligaments are tightened and secured around the perimeter
of the joint capsule. Such procedures frequently result in
post-operative pain, loss of motion, nerve injury and even
osteoarthritis. Further, capsular shift patients require lengthy
post-operative rehabilitation and often do not achieve pre-injury
levels of joint stability.
[0006] Surgeons also have developed minimally invasive arthroscopic
techniques for performing capsular shift procedures which, for the
most part, replicate the open procedures. An arthroscopic approach
typically results in less post-operative pain and reduced
rehabilitation time. However, arthroscopic capsular shift
techniques require high levels of technical expertise. Also, it is
not clear whether arthroscopic ligament fixation devices and
methods are equal to those available in an open surgical
approach.
[0007] More recently, to avoid surgical reconstruction of a joint
capsule, arthroscopic surgeons have investigated the use of thermal
energy to tighten or shrink the ligaments within a joint capsule. A
capsular ligament complex includes various types of collagen, which
is one of the most abundant proteins in the human body. It is
well-known that collagen fibrils will shrink in length when
subjected to temperatures ranging above about 60.degree. C.
Interstitial collagen consists of a continuous helical molecule
made up of three polypeptide coil chains. Each of the three chains
is approximately equal in longitudinal dimension with the molecule,
being about 1.4 nm in diameter and 300 nm in length along its
longitudinal axis in the helical domain portion.
[0008] Collagen molecules polymerize into chains in a head-to-tail
arrangement generally with each adjacent chain overlapping another
by about one-fourth the length of the helical domain. The spatial
arrangement of the three peptide chains is unique to collagen, with
each chain existing as a right-handed helical coil. The
superstructure of the molecule is represented by the three chains
that are twisted into a left-handed superhelix. The helical
structure of each collagen molecule is bonded together by heat
labile cross-links between the three peptide chains providing the
molecule with unique physical properties, including high tensile
strength and limited longitudinal elasticity.
[0009] The heat labile cross-links may be broken by thermal
effects, thus causing the helical structure of the molecule to be
destroyed (or denatured) with the peptide chains separating into
individually randomly coiled structures of significantly lesser
length. The thermal cleaving of such cross-links may result in
contraction or shrinkage of the collagen molecule along its
longitudinal axis by as much as one-third of its original
dimension. It is such thermal shrinkage of collagenous ligament
tissue that can stabilize a joint capsule.
[0010] Collagen shrinks within a specific temperature range, (e.g.,
60.degree. C. to 70.degree. C. depending on its type), which range
has been variously defined as: the temperature at which a helical
structure collagen molecule is denatured; the temperature at which
1/2 of the helical superstructure is lost; or the temperature at
which the collagen shrinkage is greatest. In fact, the concept of a
single collagen shrinkage temperature is less than meaningful,
because shrinkage or denaturation of collagen depends not only on
an actual peak temperature but on a temperature increase profile
(increase in temperature at a particular rate and maintenance at a
particular temperature over a period of time).
[0011] Thus, collagen shrinkage can be attained through high-energy
exposure (energy density) for a very short period of time to attain
"instantaneous" collagen shrinkage--the method used by all
previously known devices (both laser and high-energy RF waves) for
joint capsule shrinkage. These previously known treatments shrink
collagenous tissue in a matter of seconds (e.g., 1-2 seconds).
[0012] Previously known methods of "instantaneous" capsular
collagen shrinkage with a high energy (40 to 60 watts) mono-polar
RF probe (or similar high-energy laser) suffer from several
significant drawbacks. In such an RF treatment (or laser
treatment), the surgeon "paints" the tip of the RF probe across a
section of a joint capsule targeted for collagen shrinkage. Because
the collagen targeted for shrinkage generally lies well under the
capsular surface, high RF energy levels are needed to cause
shrinkage, typically 40 to 60 watts. These power levels, however,
pose a substantial risk of ablating or perforating the synovial
surface, which is highly undesirable.
[0013] Also, as depicted in FIG. 1A, it is difficult to "paint" the
RF probe tip (even though only 3-5 mm in diameter) across the
targeted portion of the joint capsule due to the limited working
space between humeral head H and capsule C, while still maintaining
an adequate endoscopic view of the damaged or lax tissue indicated
at D in FIG. 1A. At times, it may be necessary to use an lever-type
instrument to pry (or retract) the humeral head away from the joint
capsule to provide a larger working space, thus posing a risk of
damaging the labrum (the fibrous cartilage surrounding glenoid
capsule G).
[0014] Further, the previously known methods of creating
"instantaneous" collagen shrinkage cause the working space between
the humeral head and capsular surface to shrink and disappear
practically instantaneously, thus making it necessary to work from
a first position treatment location L1 toward a second location L2.
Thus, it is generally not possible to return toward the first
location L1 for additional treatment or diagnosis (see FIG.
1A).
[0015] Previously known methods of "painting" tissue with
high-energy RF waves with a hand-held probe to achieve rapid
collagen shrinkage are not well suited for collagenous tissues of
different thicknesses and/or for tissue in which collagen content
varies. For example, the capsular regions carrying the medial and
inferior glenohumeral ligaments have significant collagen content
(e.g., >85%) and are quite thick. Areas between the ligaments
and around the axillary recess are quite thin. Other areas of the
joint capsule contain much less collagen (e.g., <40%).
[0016] Thus, "painting" the synovial surface with RF waves--even if
the probe is moved at a steady rate--will not cause uniform
capsular shrinkage. Such free-hand techniques are technically
demanding with a steep learning curve. In practice, an experienced
surgeon will "paint" the RF probe tip across the capsular surface
in high collagen areas, but will stop and hold the probe tip in
firm contact with thicker ligament areas (or areas with lesser
collagen), in order to apply sufficient heat to the tissue. Such
start-and-stop motions, however, tend to pose a risk of ablating
and perforating the synovial lining.
[0017] Moreover, there are disadvantages in using a hand-held
mono-polar RF probe when relying on a thermal sensor in the probe
tip to safeguard against surface tissue ablation. While thermal
sensors are often touted as having the ability to cut off RF
delivery when tissue exceeds a certain temperature, this is
generally the case only when a tissue mass is firmly in contact
with the sensor. In the above-described "painting" techniques,
however, the probe tip contacts the tissue with varying pressures,
so that the "actual" tissue temperature may vary greatly from the
temperature detected by the probe. Again, there is a substantial
risk that the synovial surface may be ablated or perforated by
excessively high temperatures before RF current flow is
terminated.
[0018] Still other disadvantages of the previously known apparatus
and methods are associated with high-energy mono-polar RF delivery.
RF energy causes thermal effects in a tissue mass by perturbation
or agitation of ions as alternating RF energy courses through the
tissue in random paths of least resistance between the active
mono-polar RF electrode and a ground plate. As depicted in FIG. 1B,
"painting" a mono-polar RF probe tip across a synovial surface
causes the RF paths through tissue (to the ground plate) to change
constantly, preventing the perturbation of ions in any particular
path or location and thus preventing effective energy densities
from being attained in any particular location.
[0019] Previously known methods thus achieve "instantaneous"
collagen shrinkage only by using a very high current intensity (for
high energy densities) that are compatible with the moving
electrode ("painting") technique. As shown in FIG. 1B, the RF
current paths are only momentarily in a given position and not
focused on the tissue that is targeted for ionic agitation.
Ideally, as shown in FIG. 1C, the portion of capsular ligaments
(depthwise) that need to be heated is indicated by the shaded
area.
[0020] Yet another disadvantage of previously known mono-polar RF
probes relates to the focus of RF energy created around the probe
tip. The small diameter of the probe tip (e.g., from 2 mm to 5 mm
for reaching into the joint capsule) when energized at high power
levels causes the a focus of RF energy at the probe tip. Again,
such small diameter mono-polar RF electrodes require much higher
energy levels than would be required of a larger electrode to
achieve a given level of thermal effects in the joint capsule.
[0021] In view of the foregoing, it would be desirable to provide
apparatus and methods for elevating the temperature of collagen
tissue in a joint capsule that preferably (i) utilize relatively
low RF power levels to prevent surface ablation, (ii) are adaptable
for treating tissues having high and low collagen content, and
(iii) allow for observation of the shrinkage at less than an
instantaneous rate.
[0022] It also would be desirable to provide apparatus and methods
that shrink collagen at lower rates and at lower temperatures than
obtained with previously known RF apparatus and methods.
[0023] It further would be desirable to provide apparatus and
methods that create a uniform or predictable path for RF current
flow through targeted tissue, thereby causing more uniform heating
of tissue to a low-rate collagen shrinkage temperature.
SUMMARY OF THE INVENTION
[0024] In view of the foregoing, it is an object of this invention
to provide apparatus and methods for elevating the temperature of
collagen tissue in a joint capsule that preferably (i) utilize
relatively low RF power levels to prevent surface ablation, (ii)
are adaptable for treating tissues having high and low collagen
content, and (iii) allow for observation of the shrinkage at less
than an instantaneous rate.
[0025] It also an object of the present invention to provide
apparatus and methods that shrink collagen at lower rates and at a
lower temperatures than obtained with previously known RF apparatus
and methods.
[0026] It is a further object of this invention to provide
apparatus and methods that create a uniform or predictable path for
RF current flow through targeted tissue, thereby causing more
uniform heating of tissue to a low-rate collagen shrinkage
temperature.
[0027] These and other objects of the present invention are
accomplished by providing an electrode array comprising an
elongated insulator strip having at least one pair of spaced-apart
bi-polar RF electrodes, and a "channeling" electrode disposed on
the strip between the bi-polar electrodes to direct the flow of RF
current therebetween. The channeling electrode is not directly
coupled to the RF power source, but coupled only indirectly through
the tissue in contact with the channeling electrode. The apparatus
enables low RF power levels (e.g., 0.5 watts to 25 watts) to be
used to attain low-rate collagen shrinkage by directing or focusing
the path of the RF current.
[0028] In a preferred embodiment, bi-polar electrodes are provided
in first and second groups at each end of an elongated insulator
strip adapted to be inserted into a joint capsule through a
cannula. The bi-polar electrodes are exposed on one surface of the
strip, and are connected to a suitable RF source by individual
current-carrying wires. Any pair of bi-polar electrodes of the
first and second groups may be selected to deliver RF energy. A
channeling electrode is disposed on a central portion of the
insulator strip, spaced apart from the bi-polar electrodes, with
one surface exposed in the same direction as the active electrodes.
The channeling electrode has no direct electrical connection to the
RF source or any of the active electrodes.
[0029] Methods of using the apparatus of the present invention to
perform capsular shift procedures are also provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Additional objects and advantages of the invention will be
apparent from the following description, the accompanying drawings
and the appended claims, in which:
[0031] FIGS. 1A-1C are schematic views showing use of a previously
known probe to deliver RF energy to a glenohumeral joint to provide
rapid collagen shrinkage;
[0032] FIGS. 2 and 3 are perspective views of an illustrative
embodiment of apparatus of the present invention;
[0033] FIG. 4 is an enlarged perspective view one end of the
apparatus of FIGS. 2 and 3;
[0034] FIG. 5 is a schematic block diagram of a controller suitable
for use with the present invention;
[0035] FIGS. 6A-6E depict a sequence of using the electrode array
of FIG. 2 to perform "low rate" shrinkage of collagenous tissue of
a glenohumeral joint to treat unidirectional joint instability.
DETAILED DESCRIPTION OF THE INVENTION
[0036] The present invention provides apparatus and methods for
performing capsular shift procedures, and other similar procedures,
using low levels of directed RF power (e.g., between about 0.5
watts to 25.0 watts) to remodel collagen at low shrinkage rates,
i.e., where collagenous ligament tissue is elevated to shrinkage
temperatures slowly to achieve uniform shrinkage over a large
tissue mass. In the preferred embodiment, high frequency
alternating RF current (e.g., from 55,000 Hz to 540,000 Hz) is
directed between paired bi-polar electrodes, and through a targeted
collagenous tissue volume, by a non-energized "channeling
electrode" interposed between the bi-polar electrodes.
[0037] Alternating RF current causes ionic perturbation and
friction within the targeted tissue volume, elevating the tissue
temperature as ions follow the changes in direction of the
alternating current. Such ionic perturbation thus does not result
from direct tissue contact with a resistive electrode that conducts
heat into tissue. In the delivery of such RF energy to a soft
tissue mass, I=E/R, where I is the intensity of the current in
amperes, E is the energy potential measured in volts and R is the
tissue resistance measured in ohms. In a soft tissue target,
current density (or level of current intensity) is an important
gauge of energy delivery, which further relates to the impedance of
the target tissue mass.
[0038] The level of thermal effects generated within a target
tissue volume is influenced by several factors, such as (i) RF
current intensity, (ii)-RF current frequency, (iii) impedance
levels of tissue between paired electrodes, (iv) heat dissipation
from the target tissue volume; (v) duration of RF delivery, and
(vi) distance through the targeted tissue volume between the paired
bi-polar electrodes.
[0039] In a preferred embodiment, the apparatus of the present
invention comprises an elongate flexible insulator strip having
dimensions suitable for introducing the strip into a joint capsule
through a cannula. The insulator strip has first and second groups
of bi-polar electrodes at each end disposed facing one surface of
the strip, each bi-polar electrode facing being coupled to an RF
source. A (non-active) channeling electrode is disposed in a
central portion of the insulator strip, spaced apart from the
bi-polar electrodes, and facing the same surface of the strip as
the bi-polar electrodes. The electrode array permits delivery of
sufficient RF energy to subsurface tissue to shrink collagen at a
low rate, while reducing the risk of desiccating or ablating
surface tissues.
[0040] Referring now to FIGS. 2-3, apparatus constructed in
accordance with the principles of the present invention is
described. Electrode array 5 illustratively is adapted for thermal
treatment of a patient's joint capsule, for example a glenohumeral
capsule. Electrode array 5 comprises elongated member 10 carrying
bipolar electrode groups 20 and 22 and channeling electrode 25.
Electrodes groups 20 and 22 and channeling electrode 25 have a
lower surface exposed on surface 12 of elongated member 10.
[0041] Elongated member 10 preferably is formed from a flexible
non-conductive material, such as any suitable medical grade plastic
(e.g., vinyl), and includes insulating surface 14 that covers the
upper surfaces of all of the electrodes. More preferably, the
elongated member 10 comprises a transparent, or substantially
transparent, material as shown in FIG. 2. Elongated member 10
preferably has dimensions that allow it to be introduced into a
joint capsule through a trocar sleeve or any minimally invasive
incision.
[0042] In a preferred embodiment, elongated member 10 has a
generally rectangular cross-section having and has a thickness as
thin as practicable for an intended application. For example; for
performing a capsular shift procedure in a glenohumeral joint
capsule, elongated member 10 preferably has thickness in a range
from 0.5 mm to 3 mm, a width ranging from about 2 mm to 8 mm, and a
length in a range from about 30 mm to 80 mm. As shown in FIG. 3,
elongated member 10 preferably is sufficiently flexible to twist
about its longitudinal axis. In addition, elongated member 10 may
comprise a resilient material capable of being springably formed to
either a repose curved or linear configuration.
[0043] Bi-polar electrode groups 20 and 22 are provided in paired
bi-polar groups at left end 18A and right end 18B of elongated
member 10. Left-end bi-polar electrode group 20 comprises
individual electrodes 20A, 20B and 20C; right-end bi-polar
electrode group 22 comprises individual electrodes 22A, 22B and
22C. Electrodes 20A-20C and 22A-22C may be fabricated from a
suitable electrically conductive material, for example, gold,
nickel titanium, platinum, aluminum or copper, and are embedded in
first surface 12 of elongated member 10, for example, during a
molding process.
[0044] Each bi-polar electrode (20A-20C, and 22A-22C) is connected
to RF source 40 by individual current-carrying wires 30A-30C and
32A-32C, respectively (see also FIG. 4). Accordingly, a pair of
bi-polar electrodes consisting of any of electrodes 20A-20C paired
with any of electrodes 22a-22C may be energized, as described in
greater detail below. Current carrying wires 30A-30C and 32A-32C
preferably are encased in an insulated cord 42 to permit coupling
of the bi-polar electrodes to PS source 40.
[0045] In accordance with the principles of the present invention,
channeling electrode 25 is disposed with its lower surface exposed
on surface 12 of elongated member 10 at a position intermediate
left-end group of electrodes 20 and right-end group of electrodes
22. Channeling electrode 25 is not coupled to RF source 40, and is
insulated and spaced apart from the "active" bi-polar electrodes.
In accordance with the present invention, channeling electrode 25
directs the flow of RF current through the tissue in contact
therewith and between the selected pair of bi-polar electrodes 20
and 22.
[0046] Channeling electrode 25 may comprise any suitable
electrically conductive material, as described above for electrode
groups 20 and 22. As will of course be understood, channeling
electrode may comprise multiple discrete elements. Alternatively,
channeling electrode may extend into and overlap the region
carrying bi-polar electrode groups 20 and 22 (e.g., channeling
electrode may take the form of rails disposed outwardly of
electrode groups 20 and 22 along the width of elongated member 10,
and may extend for the length of the elongated member).
[0047] Still referring to FIGS. 2 and 3, elongated member 10 has
impressed in upper surface 12 a series visual indicator marks A, B,
C, and 1, 2, 3, one mark corresponding to each of bi-polar
electrodes 20A-20C and 22A-22C, respectively. The visual indicator
marks may be any suitable figures or symbols and provide cues that
the surgeon can view intraoperatively to determine which two
bi-polar electrodes to energize for a given procedure. Indicator
marks A-C and 1-3 preferably are as large as possible for easy
identification during an arthroscopic procedure. The surgeon may
therefore select a particular pair of bi-polar electrodes for
activation depending on which electrodes best span an area targeted
for treatment. For example, RF current may flow from electrode 20A
to 22A, from 20A to 22C, from 20C to 22C, etc.
[0048] With respect to FIG. 5, RF source 40, adapted to deliver
bi-polar RF current between selected paired bi-polar electrodes
from groups 20 and 22, is described. Control panel 45 includes
selectors A-C and 1-3, or alternatively, selector combinations A1,
A2, A3, B1, B2, etc. (not shown) corresponding to the active
electrodes or possible electrode pairings. The surgeon may, for
example, press buttons on control panel 45 to direct bi-polar RF
current flow to and between the selected bi-polar electrode
pairing. The RF source 40, for example, may be any suitable
electrosurgical RF generator capable of controlling energy delivery
to the electrode array at low-power levels, for example, from about
0.5 to 25 watts.
[0049] Referring now to FIG. 6A, a schematic view of glenohumeral
joint capsule 50 is shown with synovial surface 52 overlying
collagen-containing ligament layer 55. The end of the scapula is
called the glenoid, and is indicated at 56 having a periosteum 58,
The joint is partly stabilized by a ring of fibrous cartilage
surrounding the glenoid called the labrum (indicated in phantom
view at 59).
[0050] To access the capsule, the surgeon makes a standard
posterior access portal for an endoscope. A standard anterior
portal then is created at the upper border of the subscapularis
tendon and through the rotator interval. A sleeve or cannula
disposed through the anterior portal allows for introduction of
electrode array 5 of the present invention. Generally, the joint
capsule is prepared for standard arthroscopic fluid inflows and
outflows, although such fluids are an optional aspect of the
procedure described herein.
[0051] In FIG. 6A, the joint capsule (humeral head not shown) has
lax ligament portions indicated at band 60, such as may be caused
by an acute-event injury and result in a unidirectional
instability. As shown in FIGS. 6A-6B, the collagen ligament complex
varies in thickness within the joint capsule, e.g., with thick area
62A and thin area 62B (ligament thickness exaggerated for clarity).
FIG. 6B shows in sectional view the depth of capsular ligaments
targeted for collagen shrinkage, the area targeted for treatment
extending from the synovial surface to the periosteum across the
lax portion.
[0052] Now referring to FIG. 6C, the surgeon introduces electrode
array 5 through a suitable portal or incision into joint capsule
50, so that power cord 42 extends out of the patient's body and may
be connected to RF source 40. Electrode-array 5 may be introduced
into the working space with a suitable instrument, e.g., a grasper,
and its position is adjusted until surface 12 is positioned in
contact with the capsular surface overlying the collagenous
ligament tissue targeted for treatment, i.e., underlying band 60.
When electrode array 5 is disposed in a suitable position, the
surgeon may use sponges 70 (shown in phantom view) or other
formable material to retain electrode array 5 in position relative
to the humeral head (not shown) and the capsular surface.
[0053] The surgeon then identifies which pair of electrodes 20A-20C
and 22A-22C best span band 60 of tissue targeted for treatment. For
example, in FIG. 6C, electrode 20C (with overlying visual indicator
mark "C") and electrode 22A (with overlying visual indicator mark
"1") are best positioned in the joint capsule to deliver the
desired thermal treatment. The surgeon accordingly selects the
appropriate controls on the control panel 45 of RF source 40 for RF
delivery to the selected pair of electrodes.
[0054] In FIG. 6D the joint capsule is shown with arrows 125
indicating the path of the RF current flowing between the selected
pair of bi-polar electrodes. Of particular interest to the
invention, RF energy flows between electrode 22A and electrode 20C
and through the tissue in contact with intermediate channeling
electrode 25. As indicated by arrows 125, the RF current generally
flows through the collagenous tissue directly under channeling
electrode 25 (in band 60) that is targeted for treatment along
similar "directed paths" for the entire time the electrodes are
-activated. By contrast, in the previously known mono-polar RF
delivery methods depicted in FIG. 1, the current flow is in a
constant state of flux.
[0055] It has been determined that the channeling electrode of the
present invention generally confines the RF current path to the
tissue region proximate to conductive element as indicated by
arrows 125. This is highly desirable because stray RF current flow
between the bipolar electrodes is largely eliminated, thereby
providing higher current density (energy density) in the targeted
tissue with lower RF power levels.
[0056] Moreover, the RF current travels generally parallel to
channeling electrode 25, thereby heating the entire depth of
collagen tissue and developing a fairly uniform thermal gradient
from capsular surface 52 to periosteum 58. This aspect of the
invention is to be contrasted with previously known mono-polar RF
delivery, wherein the capsular surface receives excess heat
(possibly ablating surface 52) and RF current flow between the
probe and ground plate is perpendicular to the surface, or
random.
[0057] FIG. 6E shows the joint capsule after shrinking collagen in
ligament 55 with the capsular surface shifted toward the humeral
head (not shown) along band 60 (electrode array 5 is shown in
phantom view and the extent of capsular shift is exaggerated for
purposes of illustration). By thus directing RF current along the
desired path along and below synovial surface 52, it been found
that RF current intensity can be reduced significantly, when
compared to previously known mono-polar devices and methods.
[0058] The method of the present invention thus utilizes a
stationary electrode (rather than a painting technique), with the
bi-polar electrodes and channeling electrode pressed against
capsular surface 52. In a preferred method of the present
invention, RF current is applied for times ranging between 5
seconds and 180 seconds at powers in a range of 0.5 to 25 watts,
more preferably 2 to 20 watts, and still more preferably, 2 to 10
watts. The duration of RF current for low-rate collagen shrinkage
more preferably ranges from 10 seconds to 120 seconds, and still
more preferably, from 20 seconds to 60 seconds.
[0059] Compared to the rapid shrinkage of previously known systems
(typically 1 to 2 seconds), the longer time intervals provided by
the present invention allow "low-rate" collagen shrinkage,
affording the surgeon sufficient time to evaluate the extent of
capsular shrinkage and to terminate RF energy delivery based on
observation. Using the apparatus and methods of the present
invention, the surgeon simply may terminate the low-level RF power
at any time during capsule shrinkage to gauge the correct amount of
shrinkage. After shrinking targeted ligament tissue in the first
location, the surgeon then may move electrode array 5 to a second
location.
[0060] It should be appreciated that applications of the electrode
array of the present invention may be generalized to deliver
controlled levels of radiofrequency energy to subsurface tissues at
other locations in a body for a variety of therapeutic purposes,
such as for bio-stimulation or bio-excitation purposes.
[0061] Although particular embodiments of the present invention
have been described above in detail, it will be understood that
this description is merely for purposes of illustration. Specific
features of the invention are shown in some drawings and not in
others, and this is for convenience only and any feature may be
combined with another in accordance with the invention. Further
variations will be apparent to one skilled in the art in light of
this disclosure and are intended to fall within the scope of the
appended claims.
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