U.S. patent application number 12/940974 was filed with the patent office on 2011-09-01 for methods and systems for spinal radio frequency neurotomy.
Invention is credited to Scott A. Brandt, Robert E. Wright.
Application Number | 20110213356 12/940974 |
Document ID | / |
Family ID | 43970383 |
Filed Date | 2011-09-01 |
United States Patent
Application |
20110213356 |
Kind Code |
A1 |
Wright; Robert E. ; et
al. |
September 1, 2011 |
METHODS AND SYSTEMS FOR SPINAL RADIO FREQUENCY NEUROTOMY
Abstract
Methods and systems for spinal radio frequency neurotomy.
Systems include needles capable of applying RF energy to target
volumes within a patient. Such target volumes may contain target
medial branch nerves along vertebrae or rami proximate the sacrum.
Such procedures may be used to ablate or cauterize a portion of the
targeted nerve, thus blocking the ability of the nerve to transmit
signals to the central nervous system. Disclosed needles may be
operable to asymmetrically, relative to a central longitudinal axis
of the needle, apply RF energy. Such asymmetry facilitates
procedures where a tip of the needle is placed proximate to
anatomical structures for location verification. Then RF energy may
be applied in a selectable direction relative to the needle tip to
ablate volumes that include the targeted medial branch nerves or
rami, thus denervating facet joints or the sacroiliac joint,
respectively, to relieve pain in a patient.
Inventors: |
Wright; Robert E.; (Denver,
CO) ; Brandt; Scott A.; (Denver, CO) |
Family ID: |
43970383 |
Appl. No.: |
12/940974 |
Filed: |
November 5, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61280557 |
Nov 5, 2009 |
|
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61347351 |
May 21, 2010 |
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Current U.S.
Class: |
606/33 |
Current CPC
Class: |
A61B 2018/00791
20130101; A61B 2018/1253 20130101; A61B 18/1206 20130101; A61B
18/1477 20130101; A61B 2018/00577 20130101; A61B 2018/00595
20130101; A61B 2018/126 20130101; A61B 2018/00642 20130101; A61B
2018/00434 20130101; A61B 2018/00821 20130101; A61B 2018/00875
20130101; A61B 2090/376 20160201; A61B 2090/3762 20160201; A61B
2018/1467 20130101 |
Class at
Publication: |
606/33 |
International
Class: |
A61B 18/18 20060101
A61B018/18 |
Claims
1. A needle for insertion into a patient during an RF ablation
procedure, the needle comprising: a hub; an elongate member fixed
to the hub; a tip fixed to the elongate member at a distal end of
the needle, wherein the tip is shaped to pierce tissue of the
patient; a plurality of filaments disposed within at least a
portion of the elongate member; an actuator interconnected to the
plurality of filaments, wherein the actuator includes one of a
helical track and a helical thread on an internal surface thereof,
wherein the hub includes a corresponding other one of the helical
track and helical thread on an external surface thereof, wherein
upon rotation of the actuator relative to the hub, the actuator is
advanced or retracted relative to the hub and moves the plurality
of filaments between a retracted position and a deployed position
relative to the tip; and a lumen within the elongate member,
wherein the lumen and the tip are configured to accept an RF probe
such that an electrode of an inserted RF probe, the tip, and the
first and second filaments are operable to form a single monopolar
RF electrode.
2. (canceled)
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7. A needle for insertion into a patient during an RF ablation
procedure as recited in claim 1, wherein the RF probe comprises a
temperature sensor.
8. A needle for insertion into a patient during an RF ablation
procedure as recited in claim 1, wherein said lumen is in fluid
communication with a fluid port in the tip.
9. (canceled)
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15. A needle for insertion into a patient during an RF ablation
procedure as recited in claim 1, further comprising a slide member
fixedly connected to the plurality of filaments, wherein upon
rotation of the actuator relative to the slide Member and relative
to the hub, the actuator moves in tandem relation with the slide
member along a longitudinal axis of the needle and the plurality of
filaments are advanced or retracted relative to the hub.
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23. A needle for insertion into a patient during an RF ablation
procedure as recited in claim 1, wherein the plurality of filaments
consists of a first filament and a second filament, wherein the
needle contains no filaments other than the plurality of filaments,
wherein when the first and second filaments are in their respective
deployed positions, a midpoint between a distal end of the first
filament and a distal end of the second filament are offset from a
central longitudinal axis of the elongate member.
24. (canceled)
25. (canceled)
26. A needle for insertion into a patient during an RF ablation
procedure as recited in claim 1, wherein each filament of the
needle comprises a distal end, and wherein, in their respective
deployed positions, each said filament distal end defines a vertex
of a polygon; wherein a centroid of the polygon is offset from a
central longitudinal axis of the elongate member.
27. (canceled)
28. A needle for insertion into a patient during an RF ablation
procedure as recited in claim 1, wherein when the plurality of
filaments are in a deployed position, the tip comprises an angle of
at least 200 degrees about a central longitudinal axis of the
elongate member that is free of filaments.
29. (canceled)
30. A needle for insertion into a patient during an RF ablation
procedure as recited in claim 1, wherein each filament of the
needle comprises a distal end, and wherein, in their respective
deployed positions, each said filament distal end is disposed
distal to a distal end of the tip.
31. A needle for insertion into a patient during an RF ablation
procedure as recited in claim 22, wherein the average of all the
points is offset from the central ongitudinal axis of the elongate
member.
32. (canceled)
33. (canceled)
34. A needle for insertion into a patient during an RF ablation
procedure as recited in claim 22, wherein each said point is on a
common side of a plane that contains the central longitudinal
axis.
35. A needle for insertion into a patient during an RF ablation
procedure as recited in claim 1, wherein, when the plurality of
filaments are in the deployed position, each of the plurality of
filaments points in an at least partially distal direction.
36. A needle for insertion into a patient during an RF ablation
procedure as recited in claim 1, wherein, when the plurality of
filaments are in the deployed position, portions of each filament
extend outwardly and away from the tip and the portions are each
straight.
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111. A method of performing spinal RF neurotomy in a patient, the
method comprising: moving a tip of a needle to a first position
proximate to a target nerve along the spine of the patient; after
moving the tip, advancing a plurality of filaments to a deployed
position relative to the tip; and after advancing the plurality of
filaments, applying RF energy to the tip and to the plurality of
filaments, wherein applying the RF energy comprises ablating a
first volume comprising at least a portion of the target nerve.
112. (canceled)
113. A method of performing spinal RF neurotomy in a patient as
recited in claim 111, wherein the target nerve is a medial branch
nerve and wherein the first position is between the transverse and
superior articular processes of a lumbar vertebra.
114. (canceled)
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117. A method of performing spinal RF neurotomy in a patient as
recited in claim 111, further comprising imaging the tip of the
needle to verify position of the tip of the needle relative to the
target nerve.
118. (canceled)
119. (canceled)
120. A method of performing spinal RF neurotomy in a patient as
recited in claim 111, further comprising rotating the needle about
an axis parallel to a central longitudinal axis of the needle to
position the tip in a predetermined orientation relative to the
target nerve.
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133. A method of performing spinal RF neurotomy in a patient as
recited in claim 111, further comprising: during applying the RF
energy, monitoring a temperature proximate to the target nerve: and
adjusting a parameter of the RF energy.
134. (canceled)
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137. A method of performing spinal RF neurotomy in a patient as
recited in claim 111, further comprising: inserting an RF probe
through a lumen within the needle wherein an electrode of the RF
probe, the tip, and the plurality of filaments form a monopolar
electrode; and passing fluid through the lumen and through a fluid
port in the tip.
138. (canceled)
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141. A method of performing spinal RF neurotomy in a patient as
recited in claim 111, further comprising: retracting the plurality
of filaments to a retracted position relative to the tip; after
retracting the plurality of filaments and with the tip in the first
position, rotating the needle about a central longitudinal axis of
the needle to re-orient the plurality of filaments; after rotating
the needle, re-advancing the plurality of filaments to the deployed
position; and after re-advancing the plurality of filaments,
re-applying RF energy to the tip and to the plurality of filaments,
wherein re-applying the RF energy comprises ablating a second
volume proximate to the tip.
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146. A method of performing spinal RF neurotomy in a patient as
recited in claim 111, wherein the first position is proximate to a
vertebra and wherein moving the tip of the needle to the first
position comprises: contacting a surface of the vertebra with the
tip; and after contacting the surface, moving the needle away from
the surface of the vertebra a predetermined distance.
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178. A method of performing spinal RF neurotomy in a patient as
recited in claim 111, wherein the target nerve a medial branch
nerve and wherein the first position is proximate to a superior
surface of a transverse process of a thoracic vertebra.
179. (canceled)
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183. A method of performing spinal RF neurotomy in a patient as
recited in claim 178, wherein the thoracic vertebra is a thoracic
vertebra selected from the group consisting of T5, T6, T7, and
T8.
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194. A method of performing cervical medial branch RF neurotomy on
a third occipital nerve of a patient, the method comprising: a.
positioning the patient in a prone position; b. targeting a side of
the C2/3 Z-joint; c. rotating the head of the patient away from the
targeted side; d. locating the lateral aspect of the C2/3 Z-joint;
e. moving, after steps a, b, c and d, a tip of a needle over the
most lateral aspect of bone of the articular pillar at the juncture
of the C2/3 z-joint to a first position contacting bone proximate
to the most posterior and lateral aspect of the z-joint complex; f.
retracting, after step e, the tip of the needle a predetermined
distance from the first position; g. extending, after step f, a
plurality of filaments outwardly from the tip and towards the
lateral aspect of the C2/3 z-joint such that the plurality of
filaments are positioned straddling the lateral joint lucency and
posterior, to the C2/3 neural foramen; h. applying, after step g,
RF energy to the tip and the plurality of filaments, wherein the
applying the RF energy generates heat that ablates a portion of the
third occipital nerve.
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202. A method of performing spinal RF neurotomy in a patient as
recited in claim 111, wherein advancing the plurality of filaments
to the deployed position relative to the tip comprises rotating an
actuator interconnected to the plurality of filaments.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. provisional
patent application Ser. No. 61/280,557, filed Nov. 5, 2009, and
U.S. provisional patent application Ser. No. 61/347,351, filed May
21, 2010, both of which are hereby incorporated by reference in
their entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to thermal ablation systems
and methods and, more specifically, to improved systems and methods
for performing Radio Frequency (RF) neurotomy. The invention is
particularly apt for spinal RF neurotomy procedures.
BACKGROUND OF THE INVENTION
[0003] Thermal ablation involves the creation of temperature
changes sufficient to produce necrosis in a specific volume of
tissue within a patient. The target volume may be, for example, a
nerve or tumor. A significant challenge in ablation therapy is to
provide adequate treatment to the targeted tissue while sparing the
surrounding structures from injury.
[0004] RF ablation uses electrical energy transmitted into a target
volume through an electrode to generate heat in the area of the
electrode tip. The radio waves emanate from a non-insulated distal
portion of the electrode tip. The introduced radiofrequency energy
causes molecular strain, or ionic agitation, in the area
surrounding the electrode as the current flows from the electrode
tip to ground. The resulting strain causes the temperature in the
area surrounding the electrode tip to rise. Temperature calibration
or measurement devices, for example thermocouples, in the electrode
may provide feedback and allow precise control of the temperatures
produced at the electrode tip.
[0005] RF neurotomy uses RF energy to cauterize a target nerve to
disrupt the ability of the nerve to transmit pain signals to the
brain. Known RF neurotomy methods typically use a single RF probe
generating a generally oval or oblate spheroid lesion. The RF probe
is positioned in an attempt to include the target nerve within the
oval or oblate spheroid lesion. In various procedures, access to a
target nerve may be limited (e.g., limited to a restricted angular
range), thereby raising significant challenges to medical personnel
to create sufficient lesions to provide optimal clinical outcomes.
Additionally, anatomical variations of the nerve location relative
to anatomical landmarks provide additional challenges.
SUMMARY OF THE INVENTION
[0006] The present invention is directed toward improved methods,
systems, and related apparatuses for performing thermal ablation in
general, and in particular, improved methods, systems, and related
apparatuses for performing RF neurotomy, specifically in the region
of the spine of a patient.
[0007] In one aspect, a needle is provided for use (e.g., insertion
into a patient) during an RF ablation procedure that comprises a
hub, an elongate member fixed to the hub, a tip fixed to the
elongate member at a distal end thereof, and a plurality of
filaments disposed within at least a portion of the elongate
member. The needle may further include an actuator interconnected
to the plurality of filaments, wherein the actuator may move
relative to the hub so as to move the plurality of filaments
relative to the tip of the needle.
[0008] In one approach, the tip and first and second ones of the
plurality of filaments are operable as a single monopolar RF
electrode. By way of example, in one implementation the needle may
include a lumen disposed within the elongate member, wherein the
lumen and tip are configured to receive an RF probe, wherein the
tip and the first and second filaments may be electrically
connected to the RF probe for delivery of an RF energy signal. In
another implementation, an RF probe may be integrated into the
needle structure for communication of an RF signal to the tip and
plurality of filaments.
[0009] In another approach, the tip and the plurality of filaments
may be operable in a bipolar manner. For example, the tip and/or
one or more of the plurality of filaments may be electrically
interconnected to an RF energy source to combinatively operate as
an active RF electrode. In turn, one or a plurality of additional
ones of the plurality of filaments may be electrically
interconnected to combinatively function as a return RF
electrode.
[0010] In a further aspect, the actuator may be operable to move
the plurality of filaments relative to the tip between a retracted
position and a deployed position, wherein in the deployed position
the plurality of filaments extend outwardly from the tip. In this
regard, each filament may comprise a distal end, wherein in a
deployed position the distal ends of the filaments each define a
point, and wherein the average of all the points is offset from a
central longitudinal axis of the elongate member.
[0011] In one embodiment, the average of distal end points of first
and second filaments may be at midpoint between such distal ends.
In certain embodiments, the distal end of each of the plurality of
filaments defines a vertex of a polygon, wherein an average of
corresponding points is a centroid of the polygon.
[0012] In certain embodiments, a first filament and a second
filament may have corresponding distal ends which, together with a
distal end of the tip, define a polygon therebetween. In this
regard, in various implementations the plurality of filaments may
be disposed asymmetrically about a central longitudinal axis of the
elongate member in their deployed position.
[0013] In another aspect, a method for performing RF neurotomy in a
patient is provided (e.g., spinal RF neurotomy), and includes the
steps of moving a tip of a needle to a first position proximate to
a target nerve along the spine of a patient, and after achieving
the first position, advancing a plurality of filaments relative to
the tip to a deployed position. After such positioning, the method
may include the step of applying RF energy to the tip and/or at
least one of the plurality of filaments, wherein said RF energy
application generates heat to ablate at least a portion of the
target nerve.
[0014] In one approach, the RF energy may be applied to the needle
tip and each of the plurality of filaments to yield monopolar
operation. In another approach, the RF energy may be applied to the
tip and/or one or more of the plurality of filaments to define an
active electrode, while one or more additional one of the plurality
of filaments are electrically isolated to function as a return
electrode for bipolar operation.
[0015] In relation to the present invention it is recognized that,
as RF energy penetrates biological tissue, protein and water
molecules oscillate in response to the RF current and the tissue
adjacent to the active needle tip heats secondary to ionic
friction. As the tissue heats, and coagulates, the biophysical
properties of the tissue change. These tissue changes limit
penetration of the RF energy beyond a leading edge defined by the
shape and size of the active needle tip. The size of a
radiofrequency lesion using conventional needle technology is
limited regardless of the duration of lesion or maximum temperature
delivered.
[0016] The described invention overcomes this obstacle and expands
the effective area of RF energy delivery by increasing the overall
active tip surface area from which the RF energy emanates. The use
of multiple filaments provides additional conduits for RF energy
creating a multipolar RF field effect. The size and specific
conformation of the RF lesion may be dictated by the location and
orientation of the filaments, and may be beneficially modified to
suit a specific anatomical application by changing the size,
placement, and number of filaments.
[0017] Additional aspects and advantages of the present invention
will become apparent to one skilled in the art upon consideration
of the further description that follows. It should be understood
that the detailed description and specific examples are intended
for purposes of illustration only and are not intended to limit the
scope of the invention. Furthermore, any of the above arrangements,
features and/or embodiments may be combined with any of the above
aspects where appropriate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] For a more complete understanding of the present invention
and further advantages thereof, reference is now made to the
following Detailed Description of the Invention taken in
conjunction with the accompanying drawings, wherein:
[0019] FIG. 1 is a schematic diagram of an RF neurotomy system
being used to perform RF neurotomy on a patient.
[0020] FIG. 2A is a perspective view of a needle that may be used
in an RF neurotomy procedure.
[0021] FIG. 2B is a cut away perspective view of a portion of the
needle of FIG. 2A.
[0022] FIG. 2C is a cut away view of a portion of an alternate
embodiment of a needle that may be used in an RF neurotomy
procedure.
[0023] FIG. 3A is a detailed view of a tip of the needle of FIG. 2A
with filaments disposed in a fully deployed position.
[0024] FIG. 3B is a detailed view of a tip of the needle of FIG. 2A
with filaments disposed in a retracted position.
[0025] FIG. 3C is a detailed view of an alternate tip of the needle
of FIG. 2A with filaments disposed in a deployed position.
[0026] FIG. 4 is a schematic diagram of an RF probe assembly.
[0027] FIG. 5 is an end view of the needle of FIG. 2A.
[0028] FIG. 6 is a side view of the tip of the needle of FIG.
2A.
[0029] FIG. 7 is an end view of another alternate embodiment of the
needle of FIG. 2A.
[0030] FIG. 8 is an end view of another alternate embodiment of the
needle of FIG. 2A.
[0031] FIG. 9 is an end view of another alternate embodiment of the
needle of FIG. 2A.
[0032] FIG. 10 is a side view of another alternate embodiment of
the needle of FIG. 2A.
[0033] FIG. 11A is an illustration of an exemplary set of isotherms
that may be created with the needle of FIG. 2A.
[0034] FIG. 11B is an illustration of an exemplary lesion that may
be created with the needle of FIG. 2A.
[0035] FIG. 11C is an illustration of an exemplary lesion that may
be created with a single-filament needle.
[0036] FIG. 12 is a perspective view of the needle of FIG. 2A
positioned relative to a lumbar vertebra for performing RF
neurotomy.
[0037] FIG. 13 is an illustration of a sacrum including target
lesion volumes for performing Sacroiliac Joint (SIJ) RF
neurotomy.
[0038] FIG. 14 is a perspective view of the needle of FIG. 2A
positioned relative to a thoracic vertebra for performing RF
neurotomy.
[0039] FIG. 15 is a perspective view of the needle of FIG. 2A
positioned relative to the C2/3 cervical zygapophyseal joint (z
joint)for performing cervical medial branch RF neurotomy on the
third occipital nerve.
DETAILED DESCRIPTION OF THE INVENTION
[0040] In the following description, the invention is set forth in
the context of apparatus and methods for performing RF ablation.
More particularly, the systems and methods may be used to perform
RF neurotomy to ablate portions of target nerves. Even more
particularly, the systems and methods may be used to perform spinal
RF neurotomy to ablate portions of target nerves along the spine of
a patient to relieve pain. For example, embodiments of methods and
apparatuses described herein relate to lumbar RF neurotomy to
denervate a facet joint between the L4 and L5 lumbar vertebrae.
Denervation is achieved by application of RF energy to a portion of
a medial branch nerve to ablate or cauterize a portion of the
nerve, thus interrupting the ability of the nerve to transmit
signals to the central nervous system. In another example,
embodiments described herein relate to sacroiliac joint RF
neurotomy.
[0041] FIG. 1 is an illustration of an RF neurotomy system 100 for
performing RF neurotomy on a patient 101. The patient 101 may be
positioned face down on a table 109 or surface to allow access
along the spine of the patient 101. The table 109 may be made of
radiolucent materials substantially transparent to x-rays, such as
carbon fiber.
[0042] The system 100 may include an RF generator 102 capable of
generating an RF energy signal sufficient to ablate target tissue
(e.g. cause lesions in targeted volumes; cauterize targeted
portions of target nerves). The RF generator 102 may, for example,
be capable of delivering RF energy of about 460,000-500,000 Hz. A
needle 103 capable of conducting (e.g., transmitting or directing)
RF energy may be interconnected to the RF generator 102 and may be
used to deliver an RF energy signal to a specific site within the
patient 101. Where the needle 103 is a monopolar device, a return
electrode pad 104 may be attached to the patient 101 to complete a
circuit from the RF generator 102, through the needle 103, through
a portion of the patient 101, and back to the RF generator 102
through the return electrode pad 104. In other bipolar arrangements
the needle 103 may comprise at least one supply electrode and at
least one return electrode to define the circuit.
[0043] The RF generator 102 may be operable to control the RF
energy emanating from the needle 103 in a closed-loop fashion. For
example, the needle 103 and/or an RF probe disposed within the
needle 103 may contain a temperature measurement device, such as a
thermocouple, to measure the temperature at the target tissue. Data
may also be available from the RF generator 102, such as power
level and/or impedance, which may also be used for closed-loop
control of the needle 103.
[0044] Turning to FIG. 4, an exemplary RF probe assembly 400
compatible with the needle 103 is illustrated. The RF probe
assembly 400 includes an RF probe 401 that may be inserted into a
patient (e.g., through needle 103) and may direct RF energy to the
target tissue. The RF probe 401 may include a thermocouple operable
to measure temperature at a distal end 402 of the RF probe 401. The
RF probe assembly 400 may include a connector 403 and a cable 404
for use in connecting the RF probe 401 to the RF generator 102.
[0045] Returning to FIG. 1, the system 100 may include an imaging
system 105 capable of producing internal images of the patient 101
and the needle 103 to facilitate navigation of the needle 103
during a procedure. The system 100 may further include a display
for displaying the generated images to a physician performing the
RF ablation procedure. In one example, the imaging system 105 may
be a fluoroscope capable of generating real-time two dimensional
images of the needle 103 and internal structures of the patient
101. As such, the imaging system may include an X-ray source 106,
an X-ray detector 107 and a controller 108. The X-ray source 106
and X-ray detector 107 may be mounted on a movable structure (e.g.,
a C-arm), to facilitate capturing a variety of images of the
patient 101 (e.g., at various angles or projection views).
Alternatively, the imaging system 105 may be any other appropriate
imaging system, such as, for example, a computed tomography (CT)
scanner.
[0046] FIG. 2A is a detailed view of the needle 103 of the system
100 for performing RF neurotomy. The needle 103 may include a tip
201 that tapers to a point 301 capable of piercing the skin of a
patient. The needle 103 may further include an elongate member 203
connected to the tip 201 at a distal end 202 of the needle 103 and
connected to a hub 204 at a proximal end 205 of the needle 103. The
needle 103 includes a central longitudinal axis 223 that is
disposed along the center of the elongate member 203.
[0047] The needle 103 may include a self-contained mechanical
mechanism, in the form of deployable filaments 206a, 206b, operable
to expand the volume of effective RF energy delivery as compared to
known single-electrode RF probes. The filaments 206a, 206b may be
at least partially disposed within the elongate member 203 and may
be operable to emerge through a side wall of the needle 103
proximate to the distal end 202 of the needle 103. Alternatively,
the needle 103 may include a single filament or three or more
filaments. The filaments 206a, 206b allow offsetting and/or
contouring of the lesion geometry produced using the needle 103 to
match a desired target volume. The filaments 206a, 206b may be
deployable and/or retractable by moving an actuator 216 relative to
the hub 204.
[0048] As will be further described, the needle 103 may further
include a tube 207 that includes a lumen therethrough. The lumen
may be used to transport fluids to and/or from the target volume.
The lumen may also accept the RF probe 401 for delivery of RF
energy to the target volume. In an alternate embodiment, the RF
probe 401 may be integrated into the needle 103. In such an
embodiment, the tube 207 need not be present for RF energy
delivery, although it may be included to facilitate fluid delivery.
The filaments 206a, 206b may include lumens therethrough for the
transportation of fluid to and/or from the target volume. The
filaments 206a, 206b may function as thermocouples.
[0049] As RF energy penetrates biological tissue, protein and water
molecules oscillate in response to the RF current and the tissue
adjacent to the RF electrode is heated. As the tissue heats and
coagulates, the biophysical properties of the tissue change. These
tissue changes limit penetration of the RF energy beyond a leading
edge defined by the shape and size of an active needle tip.
Accordingly, the size of a radiofrequency lesion using conventional
single needle technology is thus practically limited after
achievement of a certain temperature delivered for a certain
time.
[0050] The needle 103 with deployable filaments 206a, 206b
overcomes this obstacle and expands the effective area of RF energy
delivery by providing multiple locations (e.g., tip 201 and
filaments 206a, 206b) from which the RF energy emanates. The use of
multiple filaments 206a, 206b provides additional conduits for RF
energy creating a multiple electrode RF field effect. The size,
shape and location of a lesion created with the needle 103 may be
established by the quantity, location and orientation of the
filaments, and may be beneficially modified to suit a specific
anatomical application by changing various aspects of the filaments
as discussed below.
[0051] Where it is desired to create a lesion offset from the
central longitudinal axis 223, the lesion may be preferentially
offset in a desired direction from the central longitudinal axis
223 by rotationally orienting the needle 103. Moreover, the needle
103 may be used to create a lesion offset from the central
longitudinal axis 223 in a first direction. Then, the filaments
206a, 206b may be retracted, the needle 103 rotated, and the
filaments 206a, 206b re-deployed to create a lesion offset from the
central longitudinal axis 223 in a second direction.
[0052] FIGS. 3A and 3B are detailed views of the distal end 202 of
the needle 103 that includes the tip 201. The tip 201 may include
the sharpened point 301 for piercing the skin of a patient and
facilitating advancement through tissue. The tip 201 may further
include a tapered portion 302 that transitions the tip 201 from the
point 301 to a body portion 303. The body portion 303 is the
portion of the tip 201 that is disposed proximal to the tapered
portion 302. The body portion 303 may be cylindrical as
illustrated, or it may be of any other appropriate shape. The body
portion 303 may have a cross-section that coincides with the cross
section of the elongate member 203.
[0053] The tip 201 may act as an RF energy delivery element. As
such, the tip 201 may be made from a conductive material such as,
for example, stainless steel. The tip 201 may be coated. The tip
201 material and optional coating may be selected to improve
radiopacity, improve and/or alter RF energy conduction, improve
lubricity and/or reduce tissue adhesion.
[0054] The tip 201 may include filament port or slot 304a (not
visible in the views of FIGS. 3A and 3B) and filament port or slot
304b. The geometry of the filament slots 304a, 304b may be selected
to allow filaments 206a, 206b to be adequately retracted (e.g.,
such that they are disposed within a cross-sectional envelope of
the body portion 303 of the tip 201) while the needle 103 is
inserted into the body, so that the filaments 206a, 206b do not
cause any unintended damage to the patient. Such positioning of the
filament slots 304a, 304b avoids having filament exit features on
the tapered portion 302 and thus avoids potential coring that could
be caused by such positioning.
[0055] The internal geometry of the filament slots 304a, 304b may
be designed such that the filaments 206a, 206b may be easily
retracted and advanced. For example, the internal geometry of the
filament slots 304a, 304b may include a transition region 305 that
meets the outer surface of the body portion 303 at an angle of
about 30 degrees. The transition region 305 may, for example, be
curved or planar. Thus, when the filaments 206a, 206b are in the
form of a member without a pre-set bias (e.g., substantially
straight), advancement of the filaments 206a, 206b relative to the
filament slots 304a, 304b, will cause the filaments 206a, 206b to
be deflected outwardly as the filaments 206a, 206b move distally
along the transition region 305. Depending on the positioning of
the transition region 305 relative to where the filaments 206a,
206b are confined (e.g., in the needle 103 of FIG. 3A the filaments
206a, 206b are confined to only longitudinal movement where they
enter into the elongate member 203) and on the mechanical
properties of the filaments 206a, 206b, various deployment angles
of the filaments 206a, 206b relative to the central longitudinal
axis 223 may be achieved. Generally, the portions of the filaments
206a, 206b that extend outwardly away from the filament slots 304a,
304b may be unrestrained and thus may take any appropriate form.
For example, where there is no pre-set bias, the portions of the
filaments that extend outwardly away from the filament slots (and
therefore from the tip) may be substantially straight, such as
shown in FIGS. 2A, 3A, 3C, 6, 11A-11C and 14. Where a pre-set bias
is present, the portions of the filaments that extend outwardly
away from the filament slots may take any appropriate shape, such
as, for example, curved as shown in FIG. 10.
[0056] The radial orientation of the filament slots 304a, 304b may
be selected such that a center point between the filament slots
304a, 304b does not coincide with the central longitudinal axis
223. For example, as shown in FIGS. 2A, 3A and 3B, the filament
slots 304a, 304b may be positioned such that they are about 120
degrees apart about the circumference of the tip 201. Other
filament slot configurations may be configured to achieve the
filament placements discussed below. These configurations may be
achieved by varying the quantity of filament slots, the placement
of filament slots about the circumference of the tip 201, and/or
the placement of filament slots along the center longitudinal axis
223 to achieve the filament placements discussed below.
[0057] As noted above, and illustrated in FIGS. 3A and 3B, the
needle 103 may comprise a tube 207 that includes a lumen 222
therethrough. The lumen 222 may be employed to accept the RF probe
40 for delivery of RF energy and/or for the transport of fluids. In
this regard, the tip 201 may further include a fluid port 210 that
may be in fluid communication via a channel through the tip 201
with the lumen 222. The fluid port 210 may be centrally located or
it may be located offset from the center longitudinal axis 223 as
shown in FIGS. 2A and 3A. The fluid port 210 may be used to
transfer fluid between the region of the tip 201 and the proximal
end 205 of the needle 103. For example, during an RF neurotomy
procedure, an anesthetic and/or an image enhancing dye may be
introduced into the region of tissue around the tip 201 through the
fluid port 210. In an alternate embodiment, the fluid port 210 may
be located along the body portion 303 of the tip 201.
[0058] As may be appreciated, the channel through the tip 201 may
be sized to accommodate a tip of the RF probe 401 that may be
inserted into the needle 103. The channel may be sized such that RF
energy from the inserted RF probe 401 is satisfactorily passed from
the RF probe 401 to the tip 201 and filaments 206a, 206b.
[0059] The elongate member 203 may be in the form of a hollow tube
(e.g., sheath, cannula) interconnecting the tip 201 with the hub
204. The elongate member 203 may be configured with adequate
strength to allow the needle 103 to pierce the patient's skin and
advance to a target area through various tissue types, including,
for example, fat and muscle tissue. The elongate member 203 may
also be capable of resisting kinking as it is advanced. In an
alternate embodiment, the elongate member 203 may be a rod with a
plurality of lumens along its length to accommodate filaments 206a,
206b, the RF probe 401, and/or a fluid passage.
[0060] The elongate member 203 houses portions of the filaments
206a, 206b and the tube 207, and allows for relative movement of
the filaments 206a, 206b. The elongate member 203 may be of any
appropriate size and internal configuration to allow insertion into
the patient 101 and to house componentry therein. In an exemplary
embodiment, the elongate member 203 may, for example, be a 16 gauge
round tube or smaller. For example, the elongate member 203 may be
18 or 20 gauge. For example, the elongate member may have a maximum
cross dimension of at most about 1.7 mm. In another example, the
elongate member may have a maximum cross dimension of at most about
1 mm. The elongate member 203 may have a length selected for
performing a specific spinal RF neurotomy procedure on a particular
patient. The elongate member 203 may be constructed from an
insulative material to reduce the amount of RF energy emitted along
the length of the elongate member 203 when the RF probe 401 is
disposed therein. For example, the elongate member 203 may be
constructed from polymeric, ceramic or other insulative material.
The elongate member 203 may include a coating that may improve
radiopacity to aid in visualization of the position of the needle
103 using fluoroscopy. The elongate member 203 may include a
coating to improve its insulative properties. The elongate member
203 may include a lubricious coating to improve its ability to be
inserted and positioned within the patient and to reduce tissue
adhesion. The elongate member 203 may include markers 224 along its
length to assist in determining the depth to which the needle 103
has entered into the anatomy. Such markers 224 may be radiopaque so
that they may be viewed under fluoroscopy. A collar (not shown) may
be disposed about the elongate member 203 to assist in placement of
the tip 201 of the needle 103. For example, the tip 201 may be
positioned in a first position, the collar may then be placed
against the patient's 101 skin, and then the needle 103 may be
withdrawn a certain distance. Such a distance will be indicated by
the distance between the collar and the patient's 101 skin.
[0061] The elongate member 203 may be fixedly interconnected to the
tip 201 and hub 204 in any appropriate manner. For example, the tip
201 may be press fit into the elongate member 203 and the elongate
member 203 may be press fit into the hub 204. Other possible
methods of attachment include adhesive bonding and welding. In an
alternate embodiment, the elongate member 203 and the tip 201 may
be a single unitary structure. The elongate member 203 may be
steerable and incorporate controlling mechanisms allowing the
elongate member 203 to be deflected or steered after insertion into
the anatomy.
[0062] The tube 207 containing the lumen 222 may be constructed
from any appropriate material. For example, the tube 207 may be
constructed from a conductive material, such as stainless steel,
such that when the RF probe 401 is inserted within the tube 207,
the RF energy emitted by the RF probe 401 may be conducted through
the tube 207 and into and through the tip 201 and filaments 206A,
206b. The tube 207 may be interconnected to the tip 201 such that
the lumen 222 is in sealed, fluid communication with the channel
through the tip 201. This may be accomplished by a press fit, weld,
or any other appropriate method.
[0063] As noted, the lumen 222 may be in fluid communication with
the tip 201 at the distal end 202. A proximal end of the lumen 222
may be disposed at the proximal end 205 of the needle 103. In this
regard, the lumen 222 may run from the distal end 202 to the
proximal end 205 with the only access being at the distal and
proximal ends. Furthermore, the lumen 222 may be the only lumen of
the needle 103 disposed along the elongate member 103.
[0064] Accordingly, the RF probe 401 inserted into the lumen 222
may be positioned such that an end of the RF probe 401 is proximate
the tip 201. For example, the RF probe 401 may be positioned such
that the distal end 402 of the RF probe 401 is in the lumen 222
near the tip 201 or in the channel through the tip 201. Thus, RF
energy transmitted through the RF probe 401 may be conducted by the
tip 201 and filaments 206a, 206b. The size of the lumen 222 may be
selected to accommodate a particular size of RF probe 401. For
example, for a 22 gauge RF probe 401, at least a 21 gauge or larger
lumen 222 may be employed. For example, the lumen 222 may have a
maximum cross-dimension of less than about 0.85 mm.
[0065] The proximal end of the tube 207 may be operable to receive
the RF probe 401. Moreover, the proximal end of the tube 207 and
the actuator 216 may be configured to accept a connector, such as a
Luer fitting, such that a fluid source may be connected to the tube
207.
[0066] As illustrated in FIGS. 2A and 3A, the needle 103 includes
two filaments 206a, 206b disposed within and along elongate member
203. Distal ends of the filaments 206a, 206b are disposed proximate
to the tip 201 and proximal ends of the filaments 206a, 206b are
fixed to a filament hub 221 discussed below. The filaments 206a,
206b are movable along the central longitudinal axis 223 between a
fully deployed position as illustrated in FIGS. 2A and 3A and a
retracted position illustrated in FIG. 3B. Moving the filaments
206a, 206b distally from the retracted position moves the filaments
206a, 206b toward the fully deployed position, while moving the
filaments 206a, 206b proximally from the deployed position moves
the filaments 206a, 206b toward the retracted position. The
filaments 206a, 206b may be deployed in intermediate positions
between the fully deployed positions and the retracted
positions.
[0067] In the fully deployed position as shown in FIG. 3A, the
distal ends of the filaments 206a, 206b are disposed away from the
tip 201. In the refracted position as shown in FIG. 3B, the distal
ends of the filaments 206a, 206b are disposed entirely within an
outer perimeter (e.g., circumference where the non-tapered portion
303 of the tip 201 is round) of the tip 201. In the deployed
position, the filaments 206a, 206b act as broadcast antennae for
the RF probe 401 (e.g., RF energy passes from the RF probe 401 to
tip 201 and filaments 206a, 206b, and into a target volume within
the patient 101). In this regard, together, the RF probe 401
inserted into the lumen 222, the tip 201, and the filaments 206a,
206b, may form a monopolar electrode for application of RF energy
to the target volume. The filaments 206a, 206b allow the RF energy
from the RF probe 401 to be dispersed over a larger volume than
would be possible with the tip 201 alone.
[0068] The filaments 206a, 206b may be constructed from a material
operable to conduct RF energy, e.g., a metal such as stainless
steel, Nitinol or shape memory alloy. The filaments 206a, 206b may
be coated to enhance their ability to conduct RF energy. The
filaments 206a, 206b may include a lubricious coating to aid in
insertion and/or reduce tissue adhesion. The distal ends of the
filaments 206a, 206b may be shaped (e.g., pointed) to improve their
ability to move through tissue.
[0069] The positioning of the filaments 206a, 206b of the
embodiment illustrated in FIGS. 2A and 3A will now be described in
relation to FIG. 5. FIG. 5 is an end view of the tip 201 and
deployed filaments 206a, 206b of the embodiment illustrated in
FIGS. 2A and 3A. The filaments 206a, 206b are positioned at a
filament angle 503 of about 120 degrees apart from each other about
the central longitudinal axis 223. This coincides with the
positions of the filament slots 304a, 304b discussed above since
the filaments 206a, 206b emerge from the filament slots 304a, 304b.
Accordingly, a filament-free angle 504 of about 240 degrees is
defined as the largest angle about the circumference of the tip 201
that is free of filaments 206a, 206b. In an embodiment consisting
of two filaments, the filament angle 503 may be less than 180
degrees and the filament-free angle 504 may be correspondingly
greater than 180 degrees (e.g., greater than 200 degrees or greater
than 240 degrees).
[0070] In FIG. 5, the central longitudinal axis 223 is
perpendicular to the plane of the illustration. A midpoint 502 is
defined between distal ends 501a, 501b of the filaments 206a, 206b,
respectively. The midpoint 502 is offset from the central
longitudinal axis 223. For example, in an embodiment, the midpoint
502 may be offset from the central longitudinal axis 223 by about 2
mm. Accordingly, when RF energy is transmitted from the tip 201 and
filaments 206a, 206b, it will be transmitted asymmetrically with
respect to the central longitudinal axis 223 as energy will be
emitted from the tip 201 and the filaments 206a, 206b. As oriented
in FIG. 5, the energy will be biased in an upward direction in the
direction from the point 301 toward the midpoint 502. Thus, when RF
energy is transmitted during an RF neurotomy procedure, a lesion
will be created that is correspondingly offset from the central
longitudinal axis 223 in the direction from the point 301 toward
the midpoint 502.
[0071] FIG. 6 is a side view of the tip 201 and filaments 206a,
206b oriented such that deployed filament 206b is disposed entirely
within the plane of the figure. The filaments 206a, 206b extend
from the tip 201 at a common distance, or location, along the
central longitudinal axis 223. The filament 206b is deflected
radially outwardly from the central longitudinal axis 223. The
filament 206b emerges from the tip 201 at an angle 601 of about 30
degrees as dictated by the positioning of the transition region 305
relative to where the filament 206b is confined and on the
mechanical properties of the filament 206b (as previously
discussed). Also, it is noted that the distal tips 501a, 501b are
positioned distally beyond the point 301 by a distance 602 and are
disposed at a distance 603 from the central longitudinal axis 223.
In the embodiment illustrated in FIG. 6, the distance 602 may be
about 3.5 mm and the distance 603 may be about 3 mm. Such an
arrangement may distally offset a lesion created by the needle 103
as compared to a lesion created with a tip without filaments or a
lesion created with the needle 103 with the filaments 206a, 206b in
the retracted position.
[0072] Accordingly, the filament 206a, 206b arrangement illustrated
in FIGS. 2A, 3A, 3B, 5 and 6 may be operable to produce lesions
that are radially offset from the central longitudinal axis 223 and
distally offset from the point 301 as compared to a lesion created
by the tip 201 without the filaments or a lesion created with the
needle 103 with the filaments 206a, 206b in the retracted
position.
[0073] Variations of filament positions and configurations from
those illustrated in FIGS. 2A, 3A, 3B, 5 and 6 will now be
addressed. Variations in the relative shapes, positions and sizes
of lesions created with the needle 103 may be achieved by
repositioning the filaments. For example, as noted above, the
lesion produced by the needle 103 will be in different positions
depending on whether the filaments are in the deployed or refracted
positions. Accordingly, intermediately shaped, positioned and/or
sized lesions may be achieved by positioning the filaments in
intermediate positions between the fully deployed or refracted
positions. Thus, for any given configuration of deployable
filaments discussed herein, the positions and/or sizes of lesions
created by those configurations may be varied by varying the
positioning of the filaments to intermediate positions between the
fully deployed and retracted positions. As noted above, the needle
103 with deployed filaments is operable to produce larger lesion
volumes than the needle 103 with retracted filaments. For example,
the needle 103 with fully deployed filaments may be operable to
produce lesion volumes of about 500 mm.sup.3.
[0074] Further variation in the shape, position and/or size of
lesions created by needles with deployable filaments may be
achieved by different configurations of filaments. Variations may
include variations in materials, the number of filaments, the
radial positioning of the filaments, the axial positioning of the
filaments, the length of the filaments, the angle at which the
filaments exit the tip, and the shape of the filaments. By varying
these parameters the needle may be configured to produce lesions of
various sizes and shapes that are positioned at various locations
relative to the tip. Such variations may be specifically tailored
to be used in specific procedures, such as RF neurotomy procedures
of particular nerves adjacent to particular vertebrae.
[0075] Variations of the materials used for the tip and/or the
filaments may be selected to achieve particular lesion sizes,
positions and/or shapes. For example, the tip may be made form a
material that does not conduct RF energy. In such an embodiment, RF
energy from the RF probe 401 may be conducted by substantially only
the deployed filaments. Such an arrangement may provide for a
lesion with a larger offset from the central longitudinal axis 223
than would be produced where the tip conducts RF energy and acts as
an electrode along with the filaments.
[0076] Another material-related variation that may affect lesion
shape, size and/or position is the addition and placement of
insulation over the tip and/or filaments. For example, by placing a
layer of insulation over the proximal half of the portions of the
filaments that extend from the tip when in the deployed position,
the shape of the lesion may be altered since RF energy may
primarily emanate from the distal, non-insulated portion of the
filaments. Similarly, insulation may be added to the tip to alter
the RF energy delivered from the tip.
[0077] Moreover, the materials used in making the filaments and tip
may be selected based on RF conductivity. For example, by using a
material for the tip that is less conductive of RF energy, the
proportion of RF energy emanating from the tip as compared to that
emanating from the filaments may be altered resulting in a
corresponding change in lesion size, position and/or shape.
[0078] The RF needles and RF probes discussed herein may be
constructed from materials that are Magnetic Resonance Imaging
(MRI) compatible. As such, MRI equipment may be used to verify the
positioning of such RF needles and/or monitor the progress of an
ablation procedure (e.g., RF neurotomy) using such RF needles.
[0079] Variations of the number of filaments used for needle may be
selected to achieve particular lesion sizes, positions and/or
shapes. For example, as illustrated in FIG. 7, a third filament 701
may extend from tip 201' in a position between filaments 206a,
206b. The tips 501a, 501b of the filaments 206a, 206b and a tip 702
of filament 701 may form a polygon 703 that has a centroid 704. The
centroid 704 is offset from the central longitudinal axis 223. Such
an arrangement may produce a lesion that is offset from the central
longitudinal axis 223 to a different degree than, and shaped
differently than, a lesion created by the needle of FIG. 5. In
general, where a centroid of a polygon formed by the tips of
filaments (or, in the case where there are two filaments, the
midpoint between them) is offset from the central longitudinal axis
223, a lesion created by such a configuration will be
correspondingly offset from the central longitudinal axis 223. The
filaments 206a, 206b, 702 are positioned within the same filament
angle 503 of about 120 degrees as in the embodiment of FIG. 5.
Furthermore, the embodiment of FIG. 7 has a filament-free angle 504
of about 240 degrees, also the same as in the embodiment of FIG. 5.
In general, where the filaments are positioned within an arc that
is less than 180 degrees, resultant lesions will be offset from the
central longitudinal axis 223 in the direction of the filaments. In
general, in an embodiment consisting of three or more filaments
where the filaments are positioned within an arc that is less than
180 degrees, the filament-free angle may be correspondingly greater
than 180 degrees (e.g., greater than 200 degrees or greater than
240 degrees).
[0080] Variations in the radial positioning of filaments of a
needle may be selected to achieve particular lesion sizes,
positions and/or shapes. For example, as illustrated in FIG. 8,
four filaments 801a-801d are positioned about a tip 201''. The tips
of the filaments 801a-801d may form a polygon 802 that has a
centroid 803. Such an arrangement may produce a lesion whose center
is offset from the central longitudinal axis 223 in the direction
of the centroid 803. The filaments 801a-801d are positioned within
a filament angle 804 of about 200 degrees. Furthermore, the
embodiment of FIG. 8 has a filament-free angle 805 (i.e., the
largest angle about the circumference of the tip 201'' that is free
of filaments) of about 160 degrees. It will be appreciated that, as
illustrated in FIG. 8, a configuration capable of producing a
lesion offset from the central longitudinal axis 223 may have a
filament-free angle that is less than 180 degrees.
[0081] In the above-described embodiment of FIGS. 2A, 3A, 3B, 5,
and 6 with two filaments, a midpoint 502 between the filaments was
discussed. In embodiments with more than two filaments, a centroid
of a polygon formed by the distal ends of the filaments was
discussed. Both the midpoints and the centroids may be considered
to be "average" points of the filaments for their particular
configurations. In such embodiments, the midpoint between filaments
in two-filament embodiments and the centroid of the polygon in
embodiments with more than two filaments may be offset from the
central longitudinal axis of the elongate member. For example, the
midpoint or centroid may be offset from the central longitudinal
axis by 1 mm or more. In embodiments, the polygon may lie in a
plane perpendicular to the central longitudinal axis.
[0082] As illustrated in, for example, FIGS. 2A, 3A, 3C, 5, 7, 8
and 9 the distal ends of the filaments when fully deployed may be
disposed in a common plane. In an embodiment, the common plane may
be disposed perpendicular to the central longitudinal axis. Such a
common plane for the distal ends of deployed filaments may be
disposed distally from the distal end of the tip.
[0083] As illustrated in, for example, FIGS. 2A, 3A, 3C, 5 and 7
the filaments of the needle may be deployed on a common side of a
central plane of the needle (where the central longitudinal axis is
disposed entirely within the central plane). In such embodiments,
the distal ends of the fully deployed filaments may all be disposed
on a common side of the central plane. Such a configuration may
enable the needle to be used to create a lesion that is offset from
the tip of the needle to the same side of the central plane as the
deployed filament ends.
[0084] As illustrated, inter alia, in FIG. 2A, the filaments when
fully deployed may point in an at least partially distal direction.
In this regard, a vector extending axially from the distal end of a
filament and coinciding with a central axis of the filament at the
end of the filament has at least some distal component.
Accordingly, the fully deployed filaments embodiments shown in
FIGS. 2A, 3A and 10 all point in an at least partially distal
direction.
[0085] In another variation of the radial positioning of filaments
of a needle, the filaments may be uniformly distributed about the
circumference of the tip. Such an embodiment is illustrated in FIG.
9. The needle of FIG. 9 includes 3 equally distributed filaments
901a, 901b, 901c. Consequently, the angles 902a, 902b, 902c between
the filaments 901a, 901b, 901c may each equal 120 degrees. Such a
needle may be operable to produce a lesion that is generally
centered along the central longitudinal axis 223. However, the
position of the produced lesion axially along the central
longitudinal axis 223 may be determined by the configuration of the
filaments. For example, relatively longer filaments may be operable
to produce lesions that are positioned distal to lesions produced
by configurations with relatively shorter filaments.
[0086] Variations in the axial positioning of where deployed
filaments emerge from the tip of a needle may be selected to
achieve particular lesion sizes, positions and/or shapes. For
example, returning to FIG. 7, if the third filament 701 of the
embodiment of FIG. 7 were axially positioned such that it is distal
to filaments 206a, 206b, the resultant lesion may be produced may
be longer along the central longitudinal axis 223 than that of an
embodiment where the filaments 206a, 206b, 701 are positioned at
the same point along the central longitudinal axis 223. In another
variation, as deployed, two or more filaments may be disposed at
the same radial position and at different axial positions. Such
embodiments may include multiple rows of filaments.
[0087] The lengths of filaments beyond the tip (when the filaments
are in the deployed position) in a needle may be varied to achieve
particular lesion sizes, positions and/or shapes. For example,
increasing the length of the deployed portions of the filaments
206a and 206b of the embodiment illustrated in FIGS. 5 and 6 may
result in a needle capable of producing lesions that are more
distally positioned than those created by the embodiment as shown
in FIGS. 5 and 6. The effects of lengthening or shortening the
deployed length of the filaments are similar to those discussed
above with respect to partially deploying filaments.
[0088] Embodiments of a needle may include deployed filaments of
different lengths. Where all of the filaments of a particular
needle are moved by a common actuator, such variations may be
achieved by varying the overall length of the filaments. In such an
embodiment, the end points of the shorter filaments may be
retracted further into the tip or elongate member than longer
filaments. The effects of lengthening or shortening the deployed
length of the filaments are similar to those discussed above with
respect to variations in the axial positioning of where deployed
filaments emerge from the tip of the needle.
[0089] The angle (such as angle 601 of FIG. 6) at which a filament
exits a tip may be varied to achieve particular lesion sizes,
positions and/or shapes. For example, an embodiment similar to the
embodiment of FIGS. 5 and 6, but where the deployed filaments are
at a 60 degree angle instead of the 30 degree angle shown in FIG.
6, may be operable to produce a lesion that has a larger maximum
cross-sectional dimension in a plane perpendicular to the central
longitudinal axis 223 than the embodiment of FIGS. 5 and 6. This
may be due to the filaments emanating RF energy at a distance
further away from the central longitudinal axis than the embodiment
of FIGS. 5 and 6. A particular embodiment of the needle may include
deployed filaments at different angles relative to the central
longitudinal axis.
[0090] The shapes of the portions of the filaments that extend away
from the tip may be varied to achieve particular lesion sizes,
positions and/or shapes. For example, FIG. 10 illustrates the tip
201 and filaments 1001a, 1001b, where the portions of the filaments
1001a, 1001b that extend beyond the tip 201 are curved. Such
curvatures may be achieved by, for example, filaments that comprise
a shape memory alloy (e.g., Nitinol) or spring material. When the
filaments 1001a, 1001b are retracted, the shape of the tip 201
and/or elongate member 203 may keep the filaments 1001a, 1001b in a
constrained straightened position. As the filaments 1001a, 1001b
are advanced toward the fully deployed position, they become
unconstrained and return to their curved shape as shown in FIG. 10.
The deployed shape of the filaments 1001a, 1001b may be
predetermined, or the filaments 1001a, 1001b may be made from a
material that may be shaped by a user prior to insertion.
[0091] The curved filaments 1001a, 1001b of FIG. 10 are positioned
within planes that include the central longitudinal axis 223. In
other embodiments, the filaments 1001a, 1001b may be curved in
other directions, such as in a corkscrew arrangement. This may be
beneficial to assist the filaments in remaining anchored to the
tissue during delivery of RF energy. The curved filaments 1001a,
1001b of FIG. 10 may be operable to produce a flatter (in a plane
perpendicular to the central longitudinal axis 223) lesion than the
straight filaments 206a, 206b of FIG. 6.
[0092] FIG. 3C is a detailed view of the distal end 310 of a needle
309 that is an alternate embodiment of the needle 103. The distal
end 310 includes a tip 311 that may include a sharpened point 312
for piercing the skin of a patient and facilitating advancement
through tissue. The tip 311 may further include a tapered portion
313 that transitions the tip 311 from the point 312 to a first body
portion 314. The first body portion 314 may be connected to a
second body portion 315 at an angle 316. In an exemplary
embodiment, the angle 316 may be about 15.degree.. The second body
portion 315 may be aligned with an elongate member 317. The
elongate member 317 may be similarly configured as the elongate
member 203 of FIGS. 3A and 3B. The angle 316 between the first body
portion 314 and the second body portion 315 may aid the physician
in navigating the needle 309 to a desired position. For example, by
rotating the needle 309 such that the first body portion 314 is
pointing in a desired direction, subsequent advancement of the
needle 309 may result in the needle 309 following a non-straight
path biased toward the desired direction.
[0093] The first and second body portions 314, 315 may be
cylindrical as illustrated, or they may be of any other appropriate
shape. The first and second body portions 314, 315 may have
cross-sections that coincide with the cross section of the elongate
member 317.
[0094] The tip 311, or a non-insulated portion thereof, may act as
an RF energy delivery element. As such, the tip 311 may be made
from a conductive material such as, for example, stainless steel.
The tip 311 may be coated. The tip 311 material and optional
coating may be selected to improve radiopacity, improve and/or
alter RF energy conduction, improve lubricity and/or reduce tissue
adhesion.
[0095] The tip 311 may include filament slot 318a and filament slot
318b. The geometry of the filament slots 318a, 318b may be selected
to allow filaments 319a, 319b to be adequately retracted (e.g.,
such that they are disposed within a cross-sectional envelope of
the second body portion 315) while the needle 309 is inserted into
the body, so that the filaments 319a, 319b do not cause any
unintended damage to the patient. Such positioning of the filament
slots 318a, 318b avoids having filament exit features on the
tapered portion 313 and on the first body portion 314 and thus
avoids potential coring that could be caused by such
positioning.
[0096] The internal geometry of the filament slots 318a, 318b may
be designed such that the filaments 319a, 319b may be retracted and
advanced. For example, the internal geometry of the filament slots
318a, 318b may be configured such that advancement of the filaments
319a, 319b relative to the filament slots 318a, 318b, will cause
the filaments 319a, 319b to be deflected outwardly as the filaments
319a, 319b move distally relative to the second body portion 315.
Depending on the configuration of the filament slots 318a, 318b and
on the mechanical properties of the filaments 319a, 319b, various
deployment angles of the filaments 319a, 319b relative to a central
longitudinal axis of the second body portion 315 may be
achieved.
[0097] The configuration and orientation of the filament slots
318a, 318b may be selected such that deployed filaments 319a, 319b
may achieve the positioning illustrated in FIG. 3C. In FIG. 3C, the
filaments 319a, 319b are generally positioned in a plane that is
perpendicular to a plane that includes the angle 316 between the
first and second body portions 314, 315. As illustrated, the
filaments 319a, 319b may be positioned such that they extend at an
angle relative to the plane that includes the angle 316. Other
filament slot 318a, 318b configurations may be configured to
achieve other desired filament 319a, 319b placements. These
configurations may be achieved by varying the quantity of filament
slots and filaments, the placement of filament slots about the
circumference of the tip 311, the angle at which the filaments
extend away from the first and second body portions 314, 315,
and/or the placement of filament slots along the first and second
body portions 314, 315.
[0098] Similar to the embodiment of FIGS. 3A and 3B, the needle 309
may comprise a tube that includes a lumen therethrough. The lumen
may be employed to accept an RF probe for delivery of RF energy
and/or for the transport of fluids. In this regard, the tip 311 may
further include a fluid port 320 that may be in fluid communication
via a channel through the tip 311 with the lumen. The fluid port
320 may be used to transfer fluid between the region of the tip 311
and a proximal end of the needle 309.
[0099] In the deployed position as shown in FIG. 3C, the distal
ends of the filaments 319a, 319b are disposed away from the tip
311. In a retracted position (not shown, but similar to as shown in
FIG. 3B), the distal ends of the filaments 319a, 319b are disposed
entirely within an outer perimeter (e.g., circumference where the
second body portion 315 of the tip 311 is round) of the tip 311. In
the deployed position, the filaments 319a, 319b act as broadcast
antennae for an RF probe inserted into the needle 309. In this
regard, together, the RF probe inserted into the lumen, the tip
311, and the filaments 319a, 319b, may form a monopolar electrode
for application of RF energy to the target volume. The filaments
319a, 319b may allow the RF energy from the RF probe to be
dispersed over a larger volume than would be possible with the tip
311 alone.
[0100] The filaments 319a, 319b may be constructed in a manner
similar to as described with respect to the filaments 206a,
206b.
[0101] In general, any or all of the above variables may be
incorporated into a particular embodiment of a needle to yield a
needle capable of producing a lesion with a particular size,
position and shape relative to the tip of the needle. Such custom
sizes, positions and shapes may be designed for specific
procedures. For example, a particular lesion size, position and
shape may be selected to enable a physician to navigate the needle
to a particular landmark (e.g., proximate or touching a bone
visible using fluoroscopy) and then orient the needle such that
deployed filaments will be operable to produce a lesion at a
particular location relative to the landmark. By navigating to a
particular internal landmark, as opposed to attempting to visualize
a relative position of a needle offset from a landmark, a more
accurate and/or consistent positioning of the needle may be
achieved. In this regard, the skill level required to accurately
position the needle for a particular procedure may be reduced.
[0102] The lesion shapes achievable through selection of the above
variables may include, for example, generally spherical, oblong,
conical, and pyramidal shapes. The orientation relative to, and the
amount of offset from, the tip of such shapes may be selectable. In
an embodiment, the tips of the deployed filaments may be positioned
distally relative to the point of the tip to provide for a facile
positioning of the lesion relative to the tip. Such capability may
allow for the needle to be inserted directly toward a target
volume. In other embodiments, the tips of the deployed filaments
may be positioned at the same axial position along the central
longitudinal axis as the point of the tip or the tips of the
deployed filaments may be positioned proximally relative to the
point of the tip. In other embodiments, some filament endpoints may
be located distal to the point of the tip while others are disposed
proximal to the point of the tip.
[0103] In the embodiment of FIGS. 2A, 2B, 3A, 3B, 5 and 6, the
filaments 206a, 206b have been illustrated as running the entire
length of the elongate member 203 from the filament hub 221 to the
tip 201. In an embodiment, a single member may run along at least
part of the elongate member 203 and the filaments may be
interconnected to the single member at some point proximal to the
tip 201. Furthermore, the filaments 206a, 206b have been
illustrated as being straight within the elongate member 203. In
alternate embodiments, the filaments within the elongate member 203
may be braided, wrapped or twisted together. Such embodiments may
have increased column strength, providing resistance to buckling
and/or bending within the elongate member 203.
[0104] The filaments discussed herein may be encased within lumens
sized to help prevent buckling or bending of the filaments within
the elongate member 203. Such lumens may be part of the elongate
member or they may be separate members (e.g., tubes within the
elongate member). Such lumens may be formed by an inner member (not
shown) within the elongate member where the inner member includes
channels along its periphery in which the filaments may lie with
the elongate member forming a portion of the lumens. Lumens used
for filaments may also serve as lumens for the transfer of liquid
to and/or from the region surrounding the tip. In another
variation, the filaments may be hollow and may be used for transfer
of liquid to and/or from the region surrounding the tip.
[0105] The illustrated embodiments show all of the filaments of a
given embodiment as commonly deployed or refracted. In a variation,
one or more filaments may be separately deployed and/or refracted
such that the physician could selectively engage a desired number
of elements. In another variation, a plurality of filaments may
exit from the tip at a common location and form a fan-like
arrangement as they are deployed.
[0106] Deployment of filaments discussed above has been described
as the filaments moving relative to a stationary tip.
Alternatively, embodiments may be deployed by pulling the tip back
relative to the filaments. Such embodiments may be beneficial where
the needle is initially advanced such that it is in contact with
bone to ensure proper positioning. Then the tip may be withdrawn,
leaving the filaments (e.g., curved shape memory filaments) in a
precise, known position.
[0107] Returning to FIGS. 2A and 2B, as noted, the hub 204 may be
fixedly attached to the elongate member 203. The hub 204 may be the
primary portion of the needle 103 gripped by the physician during
insertion and manipulation of the needle 103. The hub 204 may have
an asymmetric feature, such as indicator 225, that is oriented in a
known fashion relative to the asymmetry of the tip 201. In this
regard, the indicator 225 may be used to communicate to the
physician the orientation of the tip 201 within the patient 101.
Internally, the hub 204 may include a cavity 213 sized to house a
protrusion 218 of the actuator 216. The hub 204 may include a hole
through which a projection 215 may project into the interior of the
cavity 213 to control the motion of the actuator 216 relative to
the hub 204 and to secure the actuator 216 to the hub 204. The hub
204 may be made from any appropriate material, e.g., a thermoset
plastic.
[0108] The actuator 216 may be used to control the motion to deploy
and/or retract the filaments 206a, 206b. The actuator 216 is
operable to move along the central longitudinal axis 223 relative
to the hub 204, elongate member 203 and tip 201. The actuator 216
includes the protrusion 218 extending into the cavity 213 of the
hub 204. The outer surface of the protrusion 218 includes a helical
track 219 sized to accommodate the projection 215. In this regard,
as the actuator is rotated relative to the hub 204 (e.g., by a
physician to deploy the filaments 206a, 206b), the helical track
219 and projection 215 combine to cause the actuator 216 to move
axially along the central longitudinal axis 223. The actuator 216
has an interface portion 217 that may be gripped by a user when
twisting the actuator 216. The interface portion 217 may be knurled
or otherwise textured to enhance the physician's ability to twist
the actuator 216. The protrusion 218 may include an inner cavity
226 sized to accept the filament hub 221 and to allow the filament
hub 221 to rotate freely relative to the actuator 216. In this
regard, the linear motion of the actuator 216 may be transmitted to
the filament hub 221 while the rotational motion of the actuator
216 may not be transmitted to the filament hub 221.
[0109] The actuator 216 may include a Luer fitting 220 or any other
appropriate fitting type on a proximal end thereof. The Luer
fitting 220 may be in fluid communication with the lumen 222 and
provide a connection such that fluid may be delivered into the
lumen 222 and to the fluid port 210 of the tip 201. The Luer
fitting 220 may also be configured to allow for the insertion of
the RF probe 401 into the lumen 222. The actuator 216 may be made
from any appropriate material.
[0110] The filaments 206a, 206b may be fixedly interconnected to
the filament hub 221. In this regard, the axial movement of the
filament hub 221 due to the actuator 216 may be communicated to the
filaments 206a, 206b to deploy and retract the filaments 206a, 206b
when the actuator 216 is rotated. The filament hub 221 may be made
from any appropriate material.
[0111] Thusly, the physician may be able to deploy or retract the
filaments 206a, 206b by twisting the actuator 216. For example, as
illustrated, a counterclockwise (as seen from the viewpoint of FIG.
5) rotation of the actuator 216 relative to the hub 204 will result
in the deployment (extension) of the filaments 206a, 206b.
Relatedly, a clockwise rotation of the actuator 216 relative to the
hub 204 will result in the retraction of the filaments 206a, 206b.
Additionally, by partially rotating the actuator 216 relative to
the hub 204, the filaments 206a, 206b may be partially deployed or
refracted. The actuator 216 and/or the hub 204 may include markings
to indicate the position of the filaments 206a, 206b (e.g., the
depth of deployment). The actuator 206 and/or hub 204 may include
detents to provide a tactile feedback of the position of the
filaments 206a, 206b.
[0112] Other types of mechanisms may be used to control the
deployment and retraction of the filaments 206a, 206b. For example,
a spring loaded mechanism may be used. Such a configuration may use
a spring that acts upon the filaments 206a, 206b to bias the
filaments 206a, 206b toward a predetermined position (e.g., either
deployed or retracted). Such a mechanism may be analogous to a
spring loaded mechanism used in retractable ballpoint pens. In
another example, a roll clamp mechanism may be incorporated. A
roller wheel could be incorporated into the hub 204 such that as
the wheel is rotated with the user's thumb, the filaments 206a,
206b would advance or retract. In another example, the hub 204 and
actuator 216 may interact via complimentary threaded features. As
the actuator 216 is threaded into the hub 204, the filaments 206a,
206b would advance. As the actuator 216 is threaded out of the hub
204, the filaments 206a, 206b would retract. In another example, a
Touhy-Borst type mechanism could be incorporated to control the
deployment and retraction of the filaments 206a, 206b. Any other
appropriate mechanism for controlling linear motion of the
filaments 206a, 206b may be incorporated into the needle 103.
[0113] FIG. 2C is a cut away view of a portion of an alternate
embodiment of a hub 231 and actuator 232 that may be part of RF
needle 103 used in an RF neurotomy procedure. The hub 231 may be
fixedly attached to the elongate member 203. The hub 231 may be the
primary portion of the needle 103 gripped by the physician during
insertion and manipulation of the needle 103. The hub 231 may have
an asymmetric feature, such as indicator 233, that is oriented in a
known fashion relative to the asymmetry of the tip 201. In this
regard, the indicator 233 may be used to communicate to the
physician the orientation of the tip 201 within the patient 101.
Internally, the hub 231 may include a cavity 234 sized to house a
protrusion 235 of a slide member 236. The protrusion 235 may
include a keyway or key slot 237 that may run along a longitudinal
direction of the protrusion 235. The internal surface of the hub
231 through which the protrusion 235 moves may include a mating key
(not shown) configured to fit and slide within the key slot 237.
Together, the key slot 237 and mating key of the hub 231 may limit
the slide member 236 to a linear motion along the central
longitudinal axis 223.
[0114] Filaments 206a, 206b may be fixedly connected to the
protrusion 235 of the slide member 236 for movement therewith. In
this regard, distal movement (e.g., movement to the right as shown
in FIG. 2C) of the protrusion 235 relative to the hub 231 may cause
extension of the filaments 206a, 206b relative to the hub 231,
elongate member 203 and tip 201 (not shown in FIG. 2C). For
example, distal movement of the protrusion 235 may be used to move
the filaments 206a, 206b from a retracted position to a deployed
position. Similarly, proximal movement (e.g., movement to the left
as shown in FIG. 2C) of the protrusion 235 relative to the hub 231
may result in retraction of the filaments 206a, 206b relative to
the hub 231, elongate member 203 and tip 201 (not shown in FIG.
2C).
[0115] The hub 231 may be made from any appropriate material, e.g.,
a thermoset plastic. The hub 231 may be at least partially
transparent such that the position of the protrusion 235 and/or
other components within the hub 231 may be observable by a user.
The hub 231 may further include demarcations (e.g., molded or
printed marks) such that the amount of extension of the filaments
206a, 206b may be determined from the position of the protrusion
235 and/or other components relative to the demarcations.
[0116] An actuator 232 may be used to control the motion to deploy
and/or retract the filaments 206a, 206b fixedly connected to the
protrusion 235. The actuator 232 may be generally tubular such that
it may fit around a hub projection 238 projecting from the proximal
end of the hub 231. At least a portion of the cavity 234 may be
disposed within the hub projection 238. The actuator 232 may also
include an annular feature 239 configured to fit within an annular
slot 240 in the slide member 236. The annular feature 239 may be
sized relative to the annular slot 240 such that the actuator 232
may rotate relative to the slide member 236 about the central
longitudinal axis 223 (or an axis parallel thereto) while the
position of the actuator 232 relative to the slide member 236 along
the central longitudinal axis 223 remains fixed. In this regard,
the actuator 232 and the slide member 236 may be configured to move
in tandem relation along the central longitudinal axis 223. The
annular feature 239 and annular slot 240 may be configured such
that, during assembly, the actuator 232 may be pressed onto the
slide member 236 and the annular feature 239 may snap into the
annular slot 240.
[0117] The inner surface of the actuator 232 may include a helical
track 241 sized to accommodate a corresponding mating helical
thread 242 on the hub projection 238. In this regard, as the
actuator 232 is rotated relative to the slide member 236 and hub
231 (e.g., by a physician to deploy the filaments 206a, 206b), the
helical track 241 and helical thread 242 combine to cause the
actuator 232 and the slide member 236 to move axially along the
central longitudinal axis 223. In this regard, a linear motion of
the slide member 236 relative to the hub 231 may be created while
the rotational motion of the actuator 232 may not be transmitted to
the slide member 236 and the hub 231. An outer surface of the
actuator 232 may be textured or include features to assist the user
in gripping and twisting the actuator 232. In an alternative
configuration, the helical track 241 may be disposed on the hub
projection 238 and the helical thread 242 may be disposed on the
inner surface of the actuator 232.
[0118] The slide member 236 may include a Luer fitting 243 or any
other appropriate fitting type on a proximal end thereof. The Luer
fitting 243 may be in fluid communication with a lumen passing
through the slide member 236 and may provide a connection such that
fluid may be delivered through the Luer fitting 243 and into the
lumen of the slide member 236. In turn, the lumen of the slide
member 236 may be in fluid communication with the cavity 234 of the
hub 231, which may in turn be in fluid communication with a lumen
disposed within the elongate member 223. The lumen disposed within
the elongate member 223 may be in fluid communication with the tip
201. In this regard, fluid may flow into the Luer fitting 243, into
and through the lumen within the slide member 236, into and through
the cavity 234 of the hub 231, into and through the elongate member
223, and out from the tip 201. The Luer fitting 243, the lumen
within the slide member 236, the cavity 234 of the hub 231, and the
lumen of the elongate member 223 may all also be configured to
allow for the insertion of the RF probe 401 therethrough. Moreover,
the protrusion 235 and cavity 234 of the hub projection 238 may be
sized and/or configured to form a fluid seal therebetween.
Accordingly, fluid delivered under pressure through the Luer
fitting 220 may flow through the cavity 238 and into the elongate
member 203 substantially without leaking past the interface between
the protrusion 235 and the cavity 234 of the hub projection
238.
[0119] As noted, the filaments 206a, 206b may be fixedly
interconnected to the slide member 236. In this regard, the axial
movement of the slide member 236 due to the actuator 232 may be
communicated to the filaments 206a, 206b to deploy and retract the
filaments 206a, 206b when the actuator 232 is rotated. The slide
member 236 may be made from any appropriate material. The actuator
232 may be made from any appropriate material.
[0120] Thusly, the physician may be able to deploy or retract the
filaments 206a, 206b by twisting the actuator 232. Additionally, by
partially rotating the actuator 232 relative to the hub 231, the
filaments 206a, 206b may be partially deployed or refracted. The
actuator 232 and/or hub 231 may include detents to provide a
tactile feedback of the position of the filaments 206a, 206b. The
detents may be configured such that tactile feedback associated
with engagement of a detent coincides with a predetermined amount
of deployment or retraction of the filaments 206a, 206b. In this
regard, such tactile feedback may be used in determining filament
position.
[0121] In alternate embodiments, the needle 103 may be a bipolar
device instead of the monopolar device described above. In such
embodiments, the filaments may be isolated from each other and the
tip to enable bipolar operation. Where more than two filaments are
included, elements may be included to allow for selection of the
polarity of the filaments to aid in lesion shape, size and position
control. In another variation, the needle 103 may be used in either
a monopolar or a bipolar mode as selected by the physician.
[0122] The above-described embodiments of needles may used in
spinal RF neurotomy procedures, which will now be described. In
general, for an RF neurotomy procedure, the patient may lie face
down on a table so that the spine of the patient is accessible to
the physician. At any appropriate time before, during, and/or after
the procedure, the physician may use imaging equipment, such a
fluoroscope, to visualize the patient's anatomy and/or to visualize
the positioning of equipment (e.g., the needle relative to a target
volume).
[0123] The patient may be administered sedatives and/or intravenous
fluids as appropriate. The skin of the patient surrounding where
the procedure will take place may be prepared and maintained using
an appropriate sterile technique. Where the needle is a monopolar
device, a return electrode pad may be attached to the patient. A
local anesthetic may be injected subcutaneously where the needle
will be inserted. Anesthetic may also be administered along the
approximate path the needle will take.
[0124] With the filaments in the retracted position, the needle may
be introduced into the patient and moved to a target position
relative to a target portion of a target nerve or to a target
position relative to a target volume in which the target nerve is
likely situated (all of which are generally referred to herein as
the target nerve or portion of the target nerve). The target nerve
may be an afferent nociceptive nerve such as, for example, a medial
branch nerve proximate a lumbar facet joint. Introduction into the
patient may include percutaneously using the tip of the needle to
pierce the skin of the patient. The moving of the needle may
include navigating toward the target position using fluoroscopic
guidance. Furthermore, the moving of the needle may include
advancing the needle to an intermediate position and then
repositioning the needle to the target position. For example, the
needle may be advanced until it contacts a bone or other structure
to achieve the intermediate position. This may be followed by
retracting the needle a predetermined distance to achieve the
target position. Such a procedure may be facilitated by the markers
224 or collar previously discussed.
[0125] During the moving of the needle or after the target position
has been achieved, the needle may be used to inject an anesthetic
and/or a dye. The dye may increase contrast in fluoroscopic images
to assist in visualizing the patient's anatomy, which may aid the
physician in guiding and/or verifying the position of the
needle.
[0126] The needle may be rotated about the central longitudinal
axis of the elongate member of the needle to achieve a desired
orientation relative to the target nerve. For example, the needle
may be rotated such that a lesion created with the needle with the
filaments deployed will be offset from the central longitudinal
axis toward the target nerve. Such rotation of the needle may be
performed prior to insertion of the needle into the patient and/or
after insertion into the patient. For example, the physician may
rotate the needle prior to insertion such that the needle is
generally in the desired rotational orientation. Then, after
achieving the target position, the physician may fine tune the
rotational orientation of the needle by rotating the needle to a
more precise orientation.
[0127] Once the target position and desired rotational orientation
have been achieved, the next step may be to advance one or more
filaments of the needle relative to the tip of the needle. The
particular needle used for a procedure may have been selected to
enable the creation of a particular sized and shaped lesion at a
particular position relative to the needle. As such, the particular
needle used may be of any appropriate configuration (e.g., any
appropriate number of filaments, any appropriate filament
positioning) discussed above.
[0128] Where the needle is configured as shown in FIG. 5, the
advancement of filaments may include advancing the filaments such
that when the filaments are in their respective deployed positions,
a midpoint between a distal end of the first filament and a distal
end of the second filament is offset from the central longitudinal
axis of the needle and the filament endpoints are disposed distal
to the tip of the needle. Such deployment may enable the needle to
be used to create a lesion that is offset from the tip of the
needle toward the midpoint between the deployed filament ends. The
lesion created may also be positioned at least partially distal to
the tip of the needle.
[0129] FIG. 11A is an illustration of an exemplary set of isotherms
1010a-1010c that may be created with the needle 103 of FIG. 2A. As
illustrated by the set of isotherms 1010a-1010c, RF energy
emanating from the tip 201 and filaments 206a, 206b, may produce a
region of elevated temperatures disposed about the tip 201 and
filaments 206a, 206b. The isotherms 1010a-1010c may be offset from
the central longitudinal axis 223 such that a centroid of the
isotherms as viewed in FIG. 11A is offset from the central
longitudinal axis 223 in the direction of the filaments 206a, 206b.
The centroid of the isotherms 1010a-1010c as viewed in FIG. 11A may
also be disposed distally relative to the tip 201 such that it is
disposed between the tip 201 and the distal ends of the deployed
filaments 206a, 206b. The isotherms 1010a-1010c may also be shaped
such that, as viewed in FIG. 11A, the isotherms 1010a-1010c have a
maximum cross dimension along the central longitudinal axis 223
that is greater than a maximum cross dimension in the plane of FIG.
11A perpendicular to the central longitudinal axis 223. Similarly,
as shown in FIG. 11B discussed below, the isotherms 1010a-1010c may
have a maximum cross dimension along the central longitudinal axis
223 that is greater than a maximum cross dimension perpendicular to
the plane of FIG. 11A and perpendicular to the central longitudinal
axis 223.
[0130] The offset of the centroid of the isotherms 1010a-1010c from
the central longitudinal axis 223 results in greater lesion width
in a plane perpendicular to the central longitudinal axis 223, as
compared to a similarly sized straight needle with no filaments.
The offset of the centroid of the isotherms 1010a-1010c also allows
for projection of the centroid of a corresponding lesion volume in
a direction away from the central longitudinal axis 223. By way of
example, such offsets may advantageously enable the execution of
the exemplary procedures described herein. In addition, such
offsets may advantageously enable the creation of lesion volumes
distal (relative to the needle 103) to potentially interfering
structures (e.g., an ossified process). Moreover, such offsets may
advantageously enable the needle 103 to be inserted into a patient
at a more desirable angle (e.g., closer to perpendicular to the
surface of the patient such as within 30.degree. of perpendicular
to the surface of the patient) than would be required using a
needle without offset lesion capabilities.
[0131] FIG. 11B is an illustration of an exemplary lesion 1011 that
may be created with the needle 103 of FIG. 2A. In FIG. 11B, the
needle 103 has been placed perpendicular to a surface 1012. The
surface 1012 may, for example, be the surface of a bone, such as a
lumbar vertebra. As illustrated, the filaments 206a, 206b are
deployed such they are proximate to the surface 1012. As such, the
lesion 1011 has a width along the surface 1012 that is wider than
would be created by the needle 103 if the filaments 206a, 206b were
not deployed. Such capabilities may, for example, be advantageous
where a target structure (e.g., a nerve) is known to be positioned
along the surface 1012, but its exact position is unknown. In such
a case, the needle 103 may be positioned generally perpendicular to
the surface 1012 to achieve the illustrated lesion width along the
surface 1012, whereas the needle 103 without the filaments 206a,
206b deployed, would require either multiple repositioning steps or
for the needle 103 to be placed generally parallel to the surface
1012 to achieve the same lesion width along the surface 1012.
[0132] FIG. 11C is an illustration of an exemplary lesion 1022 that
may be created with a single-filament needle 1020. The
single-filament needle 1020 is similar to the needle 103 with a
difference that the single-filament needle 1020 includes only a
single filament 1021. The filament 1021 may be configured similarly
to the filaments 206a, 206b. The single-filament needle 1020 with
the filament 1021 deployed may be operable to produce a lesion 1022
that is a flattened version (e.g., thinner in a direction
perpendicular to the central longitudinal axis 223--the left to
right direction as illustrated in FIG. 11C) of a lesion that may be
produced by the needle 103 with its filaments 206a, 206b deployed.
The capability to produce such a lesion shape may be beneficial
when it is desirable to have a relatively large lesion in a
particular direction (e.g., to compensate for the variability of
location of a target nerve) and a relatively small lesion width in
another direction (e.g., to avoid a structure such as viscera or a
patient's skin).
[0133] Where the needle is configured such that all of the
filaments of the needle are deployed on a common side of a central
plane of the needle (where the central longitudinal axis is
disposed entirely within the central plane), the advancement of
filaments may include advancing the filaments such that when the
filaments are in their respective deployed positions, the distal
ends of all of the filaments are disposed on a common side of the
central plane. Such deployment may enable the needle to be used to
create a lesion that is offset from the tip of the needle to the
same side of the central plane as the deployed filament ends. The
lesion created may also be positioned at least partially distal to
the tip of the needle.
[0134] Where the needle is configured as shown in FIG. 8, the
advancement of filaments may include advancing the filaments such
that when the filaments are in their respective deployed positions,
each filament distal end defines a vertex of a polygon whose
centroid is offset from a central longitudinal axis of the needle.
Such deployment may enable the needle to be used to create a lesion
that is offset from the tip of the needle toward the centroid. The
lesion created may also be positioned at least partially distal to
the tip of the needle.
[0135] The advancement of the filaments may be achieved using any
of the mechanisms discussed above. For example, in the embodiment
of FIG. 2A, rotating the actuator 216 relative to the hub 104 may
cause the filaments to advance to the deployed position. The
advancement of the filaments may be performed such that each of the
plurality of filaments passes through a surface of the needle that
is parallel to the central longitudinal axis of the needle. In an
embodiment, the filaments of the needle may be advanced to a
position that is an intermediate position between the retracted
position and the fully deployed position. The degree of deployment
may be based on the desired lesion size and/or the accuracy of the
placement of needle. For example, the same needle may be used in
two different procedures where the variability of the location of a
target nerve is greater in the first procedure than it is in the
second procedure. In such situation, the greater deployment of the
filaments may be used in the first procedure, whereas in the second
procedure, a smaller degree of deployment may be used since a
smaller lesion may suffice to ensure that the target nerve has been
lesioned. In another example, after placement of the needle during
a procedure, the position of the needle may be determined to be
slightly offset from a target position. In such a case, the
filaments may be deployed to a greater degree than would have been
required if the needle were placed exactly on target. In such a
case, the greater degree of deployment may be used to compensate
for the needle positioning inaccuracy. In such a case, needle
repositioning and possible associated trauma may be avoided.
[0136] After advancing the filaments to the deployed position,
their positions may be confirmed using the imaging system (e.g.,
using a fluoroscope). Furthermore, proper positioning may be
verified by using the needle to stimulate the target nerve. An
electrical signal (e.g., up to about 2 volts applied at about 2 Hz)
may be applied to the needle and the physician may observe any
related patient movement (e.g., muscle fasciculation in the
territory supplied by the nerve). In another example, an electrical
signal (e.g., up to about 1 volt applied at about 50 Hz) may be
applied to the needle and the patient may indicate if they feel any
associated sensations and their locations to assist in verifying
correct needle positioning. Such stimulation (either
physician-observed or patient reported) may be used to stimulate a
targeted nerve to determine if the deployed position is adequate to
achieve denervation of the targeted nerve. In this regard, it is
desirable for the stimulation to affect the targeted nerve.
[0137] Such stimulation may be used to attempt to stimulate a nerve
that is not targeted for denervation (e.g., a nerve where no
denervation is desired) to determine the position of the needle
relative to such a non-targeted nerve. In this regard, if the
stimulation signal does not stimulate the non-targeted nerve, it
may be assumed that the position of the needle relative to the
non-targeted nerve is such that the application of RF energy to the
needle will not result in significant damage to the non-targeted
nerve. And if the stimulation does stimulate the non-targeted
nerve, the needle may be repositioned to avoid damaging the
non-targeted nerve. In this regard, it is desirable for the
stimulation not to affect the non-targeted nerve.
[0138] After correct needle positioning has been verified (e.g., by
imaging and/or patient response), an anesthetic may be injected
through the needle.
[0139] After the filaments have been advanced to the desired
position, the next step may be to apply RF energy to the needle
using the interconnected RF generator. In embodiments that use a
separate RF probe to deliver RF energy, the RF probe may be
inserted into a lumen of the needle prior to application of the RF
energy. Additionally, when using such a configuration, the
application of RF energy may include applying RF energy to the RF
probe and conducting the RF energy away from the probe by the tip
and/or filaments.
[0140] The resultant RF energy emanating from the tip and filaments
may generate heat that ablates the target nerve. Such ablation may
be achieved by creating a lesion that includes the target nerve. It
is desired that the target nerve be completely ablated to prevent
incomplete neurotomy which may result in dysesthesia and patient
discomfort. In an exemplary embodiment, a lesion with a maximum
cross dimension of 8-10 mm may be created. Larger or smaller
lesions may be created by varying filament characteristics (e.g.,
filament advancement distance) and/or RF energy levels. The created
lesion may be offset from the central longitudinal axis of the
needle. The center of the lesion may be positioned distal to the
tip of the needle. Of note, since the RF energy is emanating from
the tip and filaments, a particularly sized lesion may be created
with a lower peak temperature (the maximum temperature experienced
in the patient) than would be possible if a needle without
filaments were to be used to create the same-sized lesion. For
example, a particular lesion may be achieved with the needle with
deployed filaments where the peak temperature is about
55-60.degree. C., whereas creation of the same lesion using a
needle without filaments could require a peak temperature of about
80.degree. C. Such lower temperatures required by the needle with
deployed filaments may result in greater patient safety.
[0141] Before, during, and after the application of RF energy, a
temperature sensor (e.g., thermocouple) at or near the tip of the
needle may be used to monitor the temperature at or near the tip.
Such readings may be used as control signals (e.g., a feedback
loop) to control the application of RF energy to the needle. If it
is desired to ablate additional target nerves or to ablate an
additional volume to ensure ablation of the original target nerve,
the spinal RF neurotomy procedure may continue.
[0142] Where the particular needle is configured to create lesions
offset from the central longitudinal axis of the needle, and the
additional target nerve or target volume is within a volume that
may be lesioned using the needle in its current position but in a
different rotational orientation, the procedure may continue as
follows. First, after the initial RF energy application, the
filaments may be retracted into the needle. Once retracted, the
needle may be rotated, and the filaments redeployed. Next, the
reoriented needle may be used to at least partially ablate the
additional target nerve or target volume. Such retargeting of
ablation volumes without repositioning (e.g., without withdrawing
the needle from the patient and reinserting), may result in reduced
patient trauma as compared to known spinal RF neurotomy procedures
which may require removal and reinsertion of a needle to achieve
lesioning of the second target volume. Moreover, such retargeting
of ablation volumes without repositioning may result in the ability
to create uniquely shaped lesions from a single insertion position.
Such shaped lesions may include, for example, lesions that are in
the shape of two or more intersecting spheres. The steps of
retracting the filaments, rotating the needle, redeploying the
filaments, and applying RF energy may be repeated a plurality of
times.
[0143] Where the additional target nerve or target volume is not
within a volume that may be lesioned using the needle in its
current position, the needle may be repositioned. Such
repositioning may include partially or fully removing the needle
from the patient and then repositioning the needle and repeating
the above-described steps.
[0144] At any point where no additional lesioning is desired, the
filaments of the needle may be retracted, and the needle may be
removed from the patient. After removal of the needle, a sterile
bandage may be placed over the needle insertion site or sites. The
patient may then be held for observation and recovery from the
effects of any sedative that may have been administered.
[0145] Examples of specific spinal RF neurotomy procedures will now
be described. Generally, steps unique to each procedure will be
discussed while steps common to any spinal RF neurotomy procedure
(e.g., site preparation, needle removal) will not be further
discussed. Each of the procedures is described as being performed
with the needle 103 of FIGS. 2A-6. It will be appreciated that the
variations in needle configuration discussed above may be used in
these procedures. For example, to increase the offset of the
created lesion relative to the central longitudinal axis, curved
(e.g., FIG. 10) and/or partially insulated filaments may be used
that may create a lesion with a greater offset from the central
longitudinal axis than the embodiment of FIG. 2A-6.
[0146] 1. Lumbar RF Neurotomy of a Medial Branch Nerve Proximate a
Lumbar Facet Joint.
[0147] This process may include using a needle that enables the
creation of lesions which are offset from the central longitudinal
axis of the needle. The procedure will be described as being
performed on the L5 vertebra 1101 using FIG. 12 and the needle 103
of FIG. 2A. It should be understood that other embodiments of
needles described herein may be used in the procedure.
[0148] The lumbar RF neurotomy process may include positioning the
tip 201 of the needle 103 (e.g., using fluoroscopic navigation)
such that it is in contact with, or proximate to the groove 1102
between the transverse 1103 and superior articular 1104 processes
of the targeted lumbar vertebra 1101. Such positioning is shown in
FIG. 12. By contacting the lumbar vertebra 1101, a positive
determination of the position of the needle 103 may be made. By way
of example, such positioning may be performed such that the needle
103 is within 30.degree. of being perpendicular to the lumber
vertebra 1101 at the point of contact with the lumbar vertebra
1101, or at the point of the lumbar vertebra 1101 closest to the
tip 201 of the needle 103. Optionally, from such a position, the
needle 103 may be retracted a predetermined amount (e.g., between
about 3 mm and 5 mm) as measured by markers 224 on the needle 103,
as determined using the collar about the elongated member 203
discussed above, and/or by fluoroscopic navigation.
[0149] The process may include rotating the needle 103 such that
the midpoint 502 is oriented toward the superior articular process
1104 and a medial branch nerve 1105 that is positioned along a
lateral face 1106 of the superior articular process 1104. Next, the
filaments 206a, 206b may be advanced to the deployed position (as
shown in FIG. 12). The position of the needle 103 and deployed
filaments 206a, 206b may be verified using fluoroscopy and/or
patient stimulation. The RF probe 401 may then be inserted into the
lumen 222 such that RF energy emanating from the probe 103 will be
conducted by the tip 201 and filaments 206a, 206b to the target
medial branch nerve 1105 and away from the intermediate branch of
the posterior primary ramus.
[0150] Next, RF energy may be applied to the RF probe 401. The RF
energy emanating from the needle 103 may be preferentially biased
toward the target medial branch nerve 1105. The lesion created by
such a procedure may, for example, have a maximum cross dimension
of 8-10 mm, and may ablate a corresponding portion of the medial
branch nerve 1105, thus denervating the facet joint.
[0151] In a variation, the needle may be operable to create a
generally symmetric lesion relative to its central longitudinal
axis. In such a variation the sequence of steps may include insert
needle, deploy filaments, and apply RF energy.
[0152] In another variation, the needle may be inserted so it is
positioned along the length of a portion of the nerve (as
illustrated by needle 103'). Such positioning is similar to known
methods of RF neurotomy performed with needles without filaments.
After positioning the needle, the filaments may be deployed and a
lesion may be created. As noted above, a needle with deployable
filaments that is capable of producing a lesion equivalent to that
of a needle without deployable filaments may be smaller in diameter
than the needle without deployable filaments. Accordingly, although
the positioning of needle 103' may be similar to known processes,
the process utilizing the needle with deployable filaments may
cause less trauma and be safer than procedures using a needle
without deployable filaments due to the smaller size of the needle
with deployable filaments. Moreover, as discussed above, the peak
temperatures required to produce the desired lesion volume may be
less when using the needle with deployable filaments as compared to
the needle without deployable filaments, further contributing to
patient safety. Furthermore, the filaments of needle 103' may be
partially or fully deployed to achieve a desired lesion location,
shape and/or size.
[0153] It is noted that the illustrated deployment of needle 103
with the filaments 206a, 206b deployed may be used to create a
lesion that approximates a lesion that would be created with the a
prior art (non filament) needle placed in the position of needle
103' (e.g., parallel to the target nerve 1105). Moreover, the
placement of needle 103 generally perpendicular to the surface of
the L5 vertebra 1101 may be less difficult to achieve than the
parallel placement of the needle 103'.
[0154] 2. Sacroiliac Joint (SIJ) RF Neurotomy of the Posterior
Rami.
[0155] This process may include using a needle that enables the
creation of lesions which are offset from the central longitudinal
axis of the needle. The procedure will be described as being
performed on the posterior rami 1201 of the SIJ referencing FIG. 13
and using the needle 103 of FIGS. 2A-6. It should be understood
that other embodiments of needles described herein may be used in
the procedure.
[0156] As part of the SIJ RF neurotomy process, it may be desirable
to create a series of lesions in a series of lesion target volumes
1203a-1203h lateral to the sacral foramina 1211, 1212, 1213 of a
side of the sacrum 1200 to ablate posterior rami 1201 that are
responsible for relaying nociceptive signals from the SIJ. Since
the exact positions of the rami 1201 may not be known, lesioning
such a series of target volumes 1203a-1203h may accommodate the
variations in rami 1201 positions. The series of target volumes
1203 may be in the form of one or more interconnected individual
target volumes, such as target volumes 1203a and 1203b. In
addition, the process may include an additional lesion 1208 between
the L5 vertebra 1209 and the sacrum 1200.
[0157] The SIJ RF neurotomy process may include positioning the tip
201 of the needle 103 (e.g., using fluoroscopic navigation) such
that it is in contact with, or proximate to, and in lateral
relation to the S1 posterior sacral foraminal aperture (PSFA) 1211
at a first point 1204 that is at the intersection of the two target
volumes 1203a and 1203b. Such positioning may be performed such
that the needle 103 is oriented within 30.degree. of being
perpendicular to the sacrum 1200 at the point of contact (or at the
point of the sacrum 1200 closest to the tip 201 of the needle 103).
By contacting the sacrum 1200, a positive determination of the
position of the needle 103 may be made. Optionally, from such a
position, the needle 103 may be retracted a predetermined amount
(e.g., between 3 mm and 5 mm) as measured by markers 224 on the
needle 103, as determined using the collar about the elongated
member 203 discussed above, and/or by fluoroscopic navigation. For
example, a contralateral posterior oblique view may be obtained to
ascertain that the tip 201 has not entered the spinal canal. For
example, a fluoroscopic view may be obtained looking down the
length of the needle 103 to verify that the needle 103 is properly
offset from the S1 PSFA 1211 and/or a fluoroscopic view may be
obtained looking perpendicular to the central longitudinal axis 223
of the needle 103 to verify that the needle is not below the
surface of the scrum (e.g., disposed within the S1 PSFA 1211).
Additionally, an electrical signal may be applied to the needle 103
to stimulate nerves proximate to the tip 201 to verify correct
needle 103 placement.
[0158] The process may include rotating the needle 103 such that
the midpoint 502 is oriented toward the first target volume 1203a
in the direction of arrow 1205a. Next, the filaments 206a, 206b may
be advanced to the deployed position. The position of the needle
103 and deployed filaments 206a, 206b may be verified using
fluoroscopy and/or stimulation. The RF probe 401 may then be
inserted into the lumen 222 such that RF energy emanating from the
needle 103 will be conducted by the tip 201 and filaments 206a,
206b to the first target volume 1203a. Next, RF energy may be
applied to the RF probe 401. The RF energy emanating from the
needle 103 may be preferentially biased toward the first target
volume 1203a. The lesion created by such an application of RF
energy may, for example, have a maximum cross dimension of 8-10 mm,
and may ablate a corresponding portion of the rami 1201.
[0159] Next, the filaments 206a, 206b may be retracted and the
needle 103 may be rotated approximately 180 degrees such that the
midpoint 502 is oriented toward the second target volume 1203b in
the direction of arrow 1205b. Optionally, some lateral
repositioning of the needle may performed (e.g. without any needle
pull back or with a small amount of needle pull back and
reinsertion). Next, the filaments 206a, 206b may be advanced to the
deployed position. The position of the needle 103 and deployed
filaments 206a, 206b may be verified using fluoroscopy and/or
stimulation. Next, RF energy may be applied to the RF probe 401 to
create a lesion corresponding to the second target volume
1203b.
[0160] In this regard, with a single insertion of the needle 103,
two interconnected lesions (which may also be considered to be a
single oblong lesion) may be created. Thus, as compared to known
methods where an RF probe must be repositioned prior to each
application of RF energy, the number of probe repositioning steps
may be greatly reduced, thus reducing patient trauma and procedure
duration. In this regard, a continuous region of lesioning may be
achieved disposed about the S1 PSFA 1211 such that the lesion
occupies a volume surrounding the S1 PSFA 1211 from about the 2:30
clock position to about the 5:30 clock position (as viewed in FIG.
13). Such lesioning may help to achieve denervation of the
posterior rami proximate to the S1 PSFA 1211.
[0161] The above procedure may be repeated as appropriate to create
lesions corresponding to the entire series of target volumes
1203a-1203h, thus denervating the SIJ. In this regard, a similar
continuous region of lesioning may be achieved disposed about the
S2 PSFA 1212 and a region of lesioning from about the 12:00 clock
position to about the 3:00 clock position (as viewed in FIG. 13)
relative to the S3 PSFA may be achieved disposed about the S3 PSFA
1213. Furthermore, a lesion 1208 may be created at the base of the
superior articular process of the L5 1209 dorsal ramus in the grove
between the superior articular process and the body of the sacrum.
The needle 103 may be inserted generally perpendicular to the plane
of FIG. 13 to produce lesion 1208.
[0162] In a variation of the above procedure, three or more lesions
may be created with a needle in a single position. For example, a
needle positioned at a point 1106 proximate to three target volumes
1203c, 1203d, and 1203e, may be operable to create lesions at each
of the three target volumes 1203c, 1203d, and 1203e, thus further
reducing the number of needle repositionings.
[0163] In another variation, each individual lesion corresponding
to the series of target volumes 1203 may be created using a needle
with deployable filaments where the needle is repositioned prior to
each application of RF energy. In such a variation the sequence of
steps may be insert needle, deploy filaments, apply RF energy,
retract filaments, reposition needle, and repeat as appropriate to
create each desired lesion. Such a procedure may be conducted using
a needle capable of producing a lesion symmetric to a central
longitudinal axis of the needle (e.g., the needle of FIG. 9).
[0164] 3. Thoracic RF Neurotomy of a Medial Branch Nerve.
[0165] This process may include using a needle that enables the
creation of lesions which are offset from the central longitudinal
axis of the needle. Successful treatment of thoracic z-joint pain
using radiofrequency ablation of relevant medial branch nerves is
challenging owing to the inconsistent medial branch location in the
intertransverse space, especially levels T5-T8. A conventional RF
cannula must be positioned at multiple locations within the
intertransverse space to achieve the sufficient tissue ablation for
successful medial branch neurotomy. The procedure will be described
as being performed on an intertransverse space between adjacent
ones 1301, 1302 of the T5 to T8 thoracic vertebrae using FIG. 14
and the needle 103 of FIGS. 2A-6. It should be understood that
other embodiments of needles described herein may be used in the
procedure.
[0166] The process may include obtaining an optimized segmental
anteroposterior image at target level defined by meticulous
counting from T1 and T12. This may be followed by obtaining an
image that is ipsalateral oblique 8-15 degrees off sagittal plane
of the spine to visualize costotransverse joint lucency clearly.
This allows improved visualization of superior-lateral transverse
process (especially in osteopenic patients). This angle aids in
directing the probe to a thoracic anatomic safe zone medial to the
lung, minimizing risk of pneumothorax.
[0167] The skin entry site for the needle 103 may be over the most
inferior aspect of transverse process slightly medial to
costotransverse joint. Inserting the needle 103 may include
navigating the device over transverse process over bone to touch
superior transverse process slightly medial to costotransverse
joint. The process may include checking anteroposterior imaging to
demonstrate active tip 201 of the needle 103 is at the
superolateral corner of the transverse process. The process may
also include checking a contralateral oblique (e.g., +/-15 degrees)
image view to demonstrate the target transverse process in an
elongate fashion. This view is useful for demonstrating the tip 201
of the needle 103 in relationship to the superolateral margin of
the transverse process subadjacent to the targeted medial branch
nerve. The process may include retracting the active tip 201
slightly (e.g., 1 mm to 3 mm).
[0168] The process may include rotating the needle 103 such that
the midpoint 502 is oriented toward the intertransverse space
between the vertebrae 1301, 1302 and the medial branch nerve 1303
that is positioned therein. Next, the filaments 206a, 206b may be
advanced ventral into the intertransverse space between the
vertebrae 1301, 1302 to the deployed position. The position of the
needle 103 and deployed filaments 206a, 206b may be verified using
fluoroscopy (e.g., using lateral imaging). The RF probe 401 may
then be inserted into the lumen 222 such that RF energy emanating
from the probe 103 will be conducted by the tip 201 and filaments
206a, 206b to the target medial branch nerve 1303. Stimulation
(e.g., motor and/or sensory) may be performed to verify
positioning. Next, RF energy may be applied to the RF probe 401.
The RF energy emanating from the needle 103 may be preferentially
biased toward the volume between the vertebrae 1301, 1302. The
lesion created by such a procedure may, for example, have a maximum
cross dimension of 8-10 mm, and may ablate a corresponding portion
of the medial branch nerve 1303.
[0169] It is noted that thoracic RF neurotomy performed on other
thoracic vertebrae may require different sized lesions. For
example, thoracic RF neurotomy performed on the T3-T4 vertebrae may
require a smaller lesion volume than the above-described procedure,
and thoracic RF neurotomy performed on the T1-T2 vertebrae may
require a still smaller lesion volume. As described herein, the
deployment of the filaments of the needle 103 may be varied to
achieve such desired target lesion volumes.
[0170] 4. Cervical Medial Branch RF Neurotomy.
[0171] Embodiments of needles described herein (e.g., the needle
103 of FIG. 2A) are capable of creating a volume of tissue ablation
necessary for complete denervation of the cervical zygapophyseal
joints, including the C2/3 cervical zygapophyseal joint (z-joint).
Tissue ablation for cervical z-joint using embodiments of needles
described herein may be accomplished using a single placement and
single heating cycle. Such single placement and single heating
cycle may avoid unnecessary tissue damage from multiple placements
of a conventional probe, and unintended injury to collateral tissue
caused by excessive lesioning. The zone of ablation created by
various embodiments of the device is designed to provide
sufficient, and necessary tissue coagulation for a successful
procedure, and thus may be expected to improve the outcomes of
patients undergoing this spinal radiofrequency neurotomy.
[0172] A cervical medial branch RF neurotomy procedure will be
described as being performed on the third occipital nerve at the
C2/3 z-joint using the needle 103 as shown in FIG. 15. In FIG. 15,
the needle 103 is positioned between the C2 1401 and C3 1402
vertebrae.
[0173] In a first step, the patient may be placed in a prone
position on a radiolucent table suited to performing
fluoroscopically guided spinal procedures. Sedation may be
administered. The patient's head may be rotated away from the
targeted side. Sterile skin prep and draping may be performed using
standard well-described surgical techniques.
[0174] For Third Occipital Nerve (TON) ablation (C2/3 joint
innervation) the lateral aspect of the C2/3 Z-joint is located
under either parasagittal or alternatively, ipsilateral oblique
rotation of less than/equal to 30 degrees of obliquity relative to
the true sagittal plane of the cervical spine. The skin entry point
may be infiltrated with local anesthetic. Then the tip 201 of the
needle 103 is moved over the most lateral aspect of bone of the
articular pillar at the juncture of the C2/3 z-joint to a first
position contacting bone proximate to the most posterior and
lateral aspect of the z-joint complex
[0175] Once boney contact is made, the needle 103 may be retracted
a predetermined distance (e.g., 1-3 mm) and the filaments are
deployed towards the lateral aspect of the C2/3 z-joint. The needle
103 may be rotated about a central longitudinal axis prior to
filament deployment to ensure that deployment will occur in the
desired direction.
[0176] Multiplanar fluoroscopic imaging may then be employed to
verify that the tip and filaments are positioned as desired. For
example, it may be verified that the filaments are positioned
straddling the lateral joint lucency, and posterior to the C2/3
neural foramen. Useful imaging angles include anterior-posterior
(AP), lateral, and contralateral oblique (Sluijter) views. To
further verify adequate positioning of the needle 103, motor
stimulation may be performed by delivering a voltage (of up to 2
volts) at 2 Hz to the tip 201 and filaments. Furthermore, sensory
stimulation may be performed at appropriate voltage (e.g., 0.4 to 1
volt) and frequency (e.g., 50 Hz).
[0177] After position verification, RF energy may be applied to the
tip and the plurality of filaments to generate heat that ablates a
portion of the third occipital nerve. After lesioning, the device
may be removed. For levels below the C2/3 z-joint, the procedure
may be similar than as described above with respect to the third
occipital nerve, with the exception that the initial boney contact
target is at the waist of inflection point of the articular
pillar.
[0178] Similar to the above procedures, other spinal RF procedures
may benefit from the asymmetrical application of RF energy from
embodiments of probes described herein. Such asymmetry may, for
example, be used to project RF energy in a desired direction and/or
limit the projection of RF energy in undesired directions. The
configuration of the filaments may be selected for a particular
application to produce a desired size, shape and location (relative
to the needle tip) of a lesion within the patient. The location of
the lesion may be offset distally and/or laterally from the tip of
the needle as required for a particular application.
[0179] It will be appreciated that the delivery of RF energy to
tissue in the anatomy is practiced for a multitude of reasons and
embodiments of needles described herein may be adapted (modified or
scaled) for use in other medical procedures. For example,
embodiments of needles described herein could be used to deliver RF
energy as a means to cauterize "feeder vessels," such as in
bleeding ulcers and/or in orthopedic applications. Further,
embodiments of needles described herein could also be adapted to
procedures such as cardiac ablation, in which cardiac tissue is
destroyed in an effort to restore a normal electrical rhythm in the
hart. This application could further benefit from the ability of
embodiments of needles described herein to deliver fluid through a
lumen since, for example, emerging procedures in cardiac therapy
require the ability to deliver stem cells, vascular endothelial
growth factor (VEGF), or other growth factors to cardiac tissue.
The ability to steer embodiments of the needle (previously
discussed) may provide significant benefit to the in the field of
cardiovascular drug delivery.
[0180] While various embodiments of the present invention have been
described in detail, it is apparent that further modifications and
adaptations of the invention will occur to those skilled in the
art. However, it is to be expressly understood that such
modifications and adaptations are within the spirit and scope of
the present invention.
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