WO2005122938A1 - Procede et dispositif electrochirurgicaux servant a extraire un tissu a l'interieur d'un corps osseux - Google Patents

Procede et dispositif electrochirurgicaux servant a extraire un tissu a l'interieur d'un corps osseux Download PDF

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Publication number
WO2005122938A1
WO2005122938A1 PCT/US2005/020774 US2005020774W WO2005122938A1 WO 2005122938 A1 WO2005122938 A1 WO 2005122938A1 US 2005020774 W US2005020774 W US 2005020774W WO 2005122938 A1 WO2005122938 A1 WO 2005122938A1
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WIPO (PCT)
Prior art keywords
electrode
ofthe
tissue
shaft
active
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PCT/US2005/020774
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English (en)
Inventor
Darren Crawford
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Arthrocare Corporation
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Application filed by Arthrocare Corporation filed Critical Arthrocare Corporation
Priority to EP05760511A priority Critical patent/EP1768595A4/fr
Publication of WO2005122938A1 publication Critical patent/WO2005122938A1/fr

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B18/04—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating
    • A61B18/12—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating by passing a current through the tissue to be heated, e.g. high-frequency current
    • A61B18/14—Probes or electrodes therefor
    • A61B18/1477—Needle-like probes
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B2018/00315—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body for treatment of particular body parts
    • A61B2018/00565—Bone

Definitions

  • the present invention relates generally to treating diseased bone by removing tissue from within the bone and more particularly, by immediately removing neoplastic and osteoporotic tissue using a minimally invasive electrosurgical probe.
  • the present invention is particularly well suited for the treatment ofthe vertebrae as well as other bone bodies such as, for example, the femur.
  • Medical procedures involving the vertebrae are typically complicated because ofthe preciseness required to avoid both neural damage and injury to major blood vessels, as well as the indirect path that is usually required to access the treatment site. This is certainly the case when performing a vertebroplasty, a procedure most commonly performed to treat vertebral compression fractures (NCFs) or metastatic disease.
  • NCFs vertebral compression fractures
  • NCFs may be secondary to osteoporosis or to the presence of (and treatment of) a tumor (e.g., myelomas or metastatic tumors) in the vertebrae.
  • Vertebroplasty is a procedure whereby bone cement, most commonly methyl methacrylate, is injected into a vertebral body by a transpedicular or paravertebral approach under CT and/or fluoroscopic guidance.
  • Percutaneous vertebroplasty is desirable from the standpoint that it is minimally invasive as compared to the alternative of surgically exposing a hard tissue site to be supplemented with a filler material.
  • Vertebroplasty involves injecting a viscous solution of bone cement (e.g., poly- methylmethacrylate) through an access cannula or an introducer needle into the fractured vertebral body.
  • the cement fills the spaces between the bone fragments and serves to stabilize the vertebral body, preventing spinal collapse.
  • the viscous solution may include a radio-opaque material to provide fluoroscopic guidance for the physician.
  • vacancies in the vertebral body being filled in a vertebroplasty procedure are very small and can comprise highly porous areas of cancellous bone. Small spaces in the vertebral body are generally undesirable because only a small volume of stabilizing bone cement may be added to the space and the infused mass of cement is likely to lack homogeneity and therefore compromise the load-bearing requirements ofthe vertebral body.
  • a larger open space may accept a greater amount of bone cement, tending to increase the stability and the life ofthe semi-artificial bone body.
  • the very small vacancies and bone fragments present in cancellous bone may present barriers to the filling material and even prevent filling of certain ofthe vacancies, resulting in insufficient stability and load-bearing capabilities ofthe vertebral body.
  • having a clearly defined, relatively large open space within the vertebral body provides improved stability and better long-term results. Even if the filling material is able to fill a vacancy, there is still the concern that the filler material may not adhere well to the uneven surface characteristics ofthe walls ofthe vacancies. Accordingly, a larger smoother cavity is desirable in vertebroplasty.
  • the cutting structures include filaments in the form of a loop, or brush, a blade that may be moved laterally or rotatably or both to reach and cut an area of tissue beyond or outward from the cross-sectional dimension ofthe cannula or needle.
  • the structure may comprise a transmitter of energy.
  • the Reiley patent at column 8, lines 19-30 indicates that the type of energy that the transmitter propagates to remove tissue can vary. Described examples include ultrasonic energy and laser energy at a suitable tissue cutting frequency.
  • a number of patents describe instruments and methods for treating tumors by applying energy from a radio frequency source. See, for example, U.S. Patent No. 6,622,731 to Daniel.
  • drilling and compacting the osteoporotic bone fails to remove the bone fragments and merely displaces them.
  • the compacted fragments provide an unstable surface for the bone cement to adhere to.
  • the presence of bony debris at the margins ofthe void created by the balloon limits the ability of cement to penetrate beyond the balloon void into the adjacent cancellous bone.
  • inserting, expanding and deflating an inflatable member require additional time and steps. Treating tumors with heat generated from RF energy can also fail to immediately remove the tissue. Accordingly, a fast minimally invasive procedure and apparatus for creating a cavity of a selected size by the removal of tissue, bone or other matter is desired.
  • tissue removal apparatus that is deliverable through current access techniques and small gauge needles or cannulas while having the capability of accessing a target tissue beyond the immediate trajectory ofthe access cannula.
  • tissue removal apparatus that was capable of penetrating cancellous bone as well as other types of tissue.
  • the present invention provides methods and devices for removing a volume of tissue within a bone body.
  • the methods generally involve inserting a distal end of an apparatus into the bone body, where the apparatus has an elongate shaft and at least one active electrode at or near the distal end ofthe shaft in electrical communication with a radio frequency current or voltage generator; and applying a radio frequency voltage to the active electrode(s) sufficient to cause the volume to be immediately removed whereby a cavity is formed within the bone body.
  • the methods may further comprise delivering an electrically conductive fluid to the one or more active electrodes. Additionally, during the step of applying a radio frequency voltage, a plasma may be formed around the active electrodes, whereby the plasma has sufficient energy to molecularly disassociate the tissue.
  • the methods may be carried out to operate on a bone body such as a vertebral body, for example, to remove abnormal tissue.
  • the tissue targeted for removal may be fractured, osteoporotic (cancellous bone), neoplastic (a tumor), nonosteoporotic, or a combination thereof. Removal ofthe targeted tissue leaves behind a cavity within the bone body.
  • certain ofthe methods may also include the step of injecting a stabilizing material (such as bone cement) into the resulting cavity.
  • a stabilizing material such as bone cement
  • These methods may also include supplying a venous coagulant solution to within the cavity prior to the step of injecting. Coagulation may then be confirmed by injecting a saline into the cavity with a tracer and observing the lack of venous uptake.
  • the apparatus may be in the form of a probe and include at least two active electrodes.
  • at least one active electrode is a ball wire.
  • the shape ofthe active electrode may include an equatorial cusp and an apical spike or tip.
  • Each ofthe at active electrodes is connected to a wire conductor that extends at least partially through the shaft.
  • the wire conductors collectively form a wire bundle.
  • the apparatus may further include a return electrode spaced proximal to the active electrodes.
  • the apparatus may further comprise a securing member that is wrapped around the wire bundle to prevent the active electrodes from radially expanding or at least from expanding beyond a desired radius.
  • the apparatus may further comprise a polymeric tubular element or member that holds the active electrodes in close proximity to one another.
  • the tubular member may be malleable.
  • the tubular element may be positioned interior to the securing member.
  • the tubular element may be arranged concentrically with the wire bundle, and positioned between the wire bundle and the securing member.
  • the probe is connected to a fluid connector and the fluid connector comprises a fluid ingress port configured to fluidly communicate with an electrically conductive fluid source, and a fluid egress port configured to fluidly communicate with an introducer needle assembly.
  • the fluid connector is also adapted to axially slide along the shaft.
  • the electrosurgical probe itself or a portion thereof is configured to allow removal of tissue to form a cavity having a cross-sectional dimension (e.g., diameter) substantially greater than that of the access opening or the introducer cannula through which the probe is delivered.
  • the shaft or a portion ofthe probe's shaft is angled or able to be angled or bent to provide a plurality of access trajectories to the tissue to be removed.
  • the shaft may have one or more preselected bends or may be malleable or bendable such that the shaft may be ⁇ selectively bent prior to use or delivery to the target tissue.
  • the shaft or distal end thereof may be flexible so as to be deflectable or articulatable upon delivery to a target tissue.
  • an end effector ofthe probe is expandable from a low profile configuration to an enlarged configuration. In the low profile state, the probe is deliverable through a very small access channel. In the high profile state, the end effector is able to reach laterally ofthe channel pathway and to remove a volume of tissue larger than a transverse dimension ofthe access channel.
  • the electrodes are mounted to a structure that is expandable upon exiting the access channel.
  • the means for expanding include but are not limited to balloon expansion, self-expanding struts or mesh and compressive and/or rotational forces applied to the electrodes.
  • kits comprising: an introducer needle for penetrating a vertebrae; an apparatus as recited above; a high frequency generator or voltage supply in electrical communication with the apparatus.
  • the kit may further comprise a fluid valve adapted to couple to a fluid source and to a proximal end ofthe introducer needle, and the valve further being slideable along the shaft.
  • FIG. 1A-1H illustrate steps of a spinal surgical procedure in accordance with the present invention.
  • FIG. 2A is a perspective view of an electrosurgical system incorporating a power supply and an electrosurgical probe for tissue ablation, resection, incision, contraction and for vessel hemostasis;
  • Fig. 2B schematically illustrates one embodiment of a power supply according to the present invention;
  • Fig. 3 illustrates an electrosurgical system incorporating a plurality of active electrodes and associated current limiting elements;
  • Fig. 4 is a side view of an electrosurgical probe;
  • Fig. 5 is a view ofthe distal end portion ofthe probe of Fig. 4;
  • FIG. 6 is an exploded view of a proximal portion of an electrosurgical probe;
  • Figs. 7A-7D illustrate four embodiments of electrosurgical probes designed for treating spinal defects;
  • Fig. 8 illustrates an electrosurgical system incorporating a dispersive return pad for monopolar and/or bipolar operations;
  • Fig. 9 is a side view of an electrosurgical probe;
  • Fig. 10 is a side view ofthe distal end portion ofthe electrosurgical probe of Fig. 9;
  • Fig. 11 is a side view of an electrosurgical probe having a curved shaft;
  • Fig. 12A is a side view ofthe distal end portion ofthe curved shaft of Fig. 11, with the shaft distal end portion within an introducer device;
  • FIG. 12B is a side view ofthe distal end portion ofthe curved shaft of Fig. 12 A, with the shaft distal end portion free unconfined by an introducer device;
  • Fig. 13 is a side view ofthe distal end portion of an electrosurgical probe showing an active electrode having an apical spike and an equatorial cusp;
  • Fig. 14 is a cross-sectional view ofthe distal end portion ofthe electrosurgical probe of Fig. 13;
  • Fig. 15 is a side view ofthe distal end portion a shaft of an electrosurgical probe, indicating the position of a first curve and a second curve in relation to the head ofthe active electrode;
  • Fig. 16A shows the distal end portion ofthe shaft of an electrosurgical probe extended distally from an introducer needle;
  • FIG. 16B illustrates the position ofthe active electrode in relation to the inner wall of the introducer needle upon retraction ofthe active electrode within the introducer needle;
  • Fig. 17 A shows a probe having a curved distal end and a plurality of active electrodes arranged in a bouquet;
  • Fig. 17B shows an enlarged view ofthe distal end section ofthe probe shown in Fig. 17A;
  • Fig. 17C shows a partial cross section of a distal section ofthe probe shown in Figs. 17A and l7B;
  • Fig. 17D shows a partial cross section of a portion ofthe distal end ofthe probe of Figs.
  • Fig 18 A shows a probe assembly in an expanded view including a probe, a fluid connector, and an introducer needle
  • Fig. 18B shows the probe assembly of Fig. 18A assembled
  • Fig. 19A, 19B show a side view and an end view, respectively, of a curved shaft of an electrosurgical probe, in relation to an introducer needle
  • Fig. 20 shows the proximal end portion ofthe shaft of an electrosurgical probe, wherein the shaft includes a plurality of depth markings
  • Fig. 21 shows the proximal end portion ofthe shaft of an electrosurgical probe, wherein the shaft includes a mechanical stop
  • Fig. 22 illustrates stages in manufacture of an active electrode of an electrosurgical probe
  • FIG. 23 schematically represents a series of steps involved in a method of making a probe shaft;
  • Fig. 24 schematically represents a series of steps involved in a method of making an electrosurgical probe;
  • Figs. 25 shows a probe with a marker;
  • Figs. 26-27 show a probe that may flex;
  • Fig. 28 illustrates a probe having a selectively inflatable balloon upon which the electrodes are positioned;
  • Fig. 29 illustrates an exemplary arrangement of electrodes on the balloon of Fig. 28;
  • Fig. 30 illustrates another exemplary arrangement of electrodes on the balloon of Fig. 28;
  • Figs. 31 A and 3 IB illustrate a selectively expandable mechanical structure having an exemplary arrangement of electrodes for use with the subject probes;
  • FIG. 31C illustrates another exemplary arrangement of electrodes suitable for use with the expandable structure of Figs. 31 A and 3 IB;
  • Figs. 32 and 32' illustrate another selectively expandable electrode structure for use with the probes ofthe present invention;
  • Fig. 33 illustrates another probe having a hinged distal section.
  • the present invention provides systems and methods for selectively applying electrical energy to a target location within or on a patient's body, particularly including tissue within a bone body such as tumors (especially metastatic tumors), osteoporotic bone fragments, and bone fragments of nonosteoporotic origin.
  • tissue within a bone body such as tumors (especially metastatic tumors), osteoporotic bone fragments, and bone fragments of nonosteoporotic origin.
  • procedures include, but are not limited to, any procedure that may benefit from creating a void or cavity in a bone body such as a vertebroplasty procedure, channeling bone tissue, removing tumors, removing cancellous bone (in the spine, leg bones or other peripheral or non-peripheral bones), interspinous tissue, degenerative discs, laminectomy/discectomy procedures for treating herniated discs, decompressive laminectomy for stenosis in the lumbosacral and cervical spine, localized tears or fissures in the annulus, nucleotomy, disc fusion procedures, medial facetectomy, posterior lumbosacral and cervical spine fusions, treatment of scoliosis associated with vertebral disease, foraminotomies to remove the roof of the intervertebral foramina to relieve nerve root compression and anterior cervical and lumbar discectomies.
  • a vertebroplasty procedure channeling bone tissue, removing tumors, removing cancellous bone (in the spine
  • Figs. 1 A to IH A method for removing a bone tumor is described in Figs. 1 A to IH.
  • Fig. 1 A a portion ofthe spine is shown.
  • three vertebral bodies are shown.
  • the introducer needle 2 may be a metallic needle having a hollow shaft. It may have a diameter from 0.5 to 5 mm, or perhaps up to 10 mm. Its length may vary.
  • a sharp or pointed obturator is provided to prevent tissue from filling the introducer needle as well as facilitate penetration tlirough the hard cortical bone.
  • the obturator may comprise a radiopaque material or it may be made of a plastic.
  • the obturator may be rigid and it may have various tip configurations to facilitate penetration of different types of tissue. As shown in Fig. IB, the introducer needle is extended through the pedicle, the cortical bone tissue, the cancellous bone tissue 3, and ultimately into or near the tumor 4 to be removed. Fig.
  • IC shows the introducer needle touching the tumor with the obturator removed.
  • Fig. ID shows insertion of an electrosurgical probe 5, described more fully in connection with Figs. 2A et seq.
  • another probe suitable for use with this method is described in co pending patent application U.S. Pat. App. No. 10/613,115, filed July 3, 2003, incorporated by reference herein in its entirety.
  • the probe 5 is configured to apply energy to ablate tissue within a bone body, creating a void or space 6.
  • the probe 5 contains at least one active electrode that is connected to a radiofrequency source. Application of a voltage difference between the active electrode and a return electrode disintegrates the tumor tissue into harmless components, leaving a space 6.
  • the present invention does not leave the tissue in place to be absorbed by the bone body over time in a slow eventual manner. Instead, the present invention ablates the tissue such that the tissue is immediately removed.
  • the mechanism of action ofthe present invention is related to formation of a plasma at the probe tip.
  • Fig. IE shows the tumor removed leaving a large open space 6. Once the tumor is removed, it is desirable to stabilize the vertebral body. An open space, crack, fragment, etc. can facilitate spinal collapse resulting in serious pain, if not dehabilitation. Accordingly, a vertebroplasty may desirably be performed as shown in Fig. IF.
  • a flowable bone cement 7 is injected into the space 6.
  • a suitable cement injection system may include a connector that cooperates with the introducer needle 2.
  • An example of a cement delivery system is EZFLOWTM CEMENT DELIVERY SYSTEM, manufactured by Parallax Medical Inc., Scotts Valley California.
  • a venous coagulant such as THROMB IN- JMI ® may be injected.
  • Fig. 1G indicates the space 6 filled with bone cement 7. Overtime, the bone cement will harden forming a solidified mass as shown in Fig. IH. In some cases, the bone cement may permeate the rest ofthe vertebral body.
  • bone cement examples include PMMA type acrylic resins such as SECOURTM, manufactured by Parallax Medical Inc., Scotts Valley, California.
  • stabilizing material may be used to fill the space 6 some of which having radio pacifiers to increase visualization ofthe flow. Specific aspects ofthe apparatus, system, and kits for performing various procedures to remove tissue within a bone body are described in more detail below.
  • the high electric field intensities may be generated by applying a high frequency voltage that is sufficient to vaporize an electrically conductive fluid over at least a portion of the active electrode(s) in the region between the distal tip ofthe active electrode(s) and the target tissue.
  • the electrically conductive fluid may be a liquid or gas, such as isotonic saline, blood, extracelluar or intracellular fluid, delivered to, or already present at, the target site, or a viscous fluid, such as a gel, applied to the target site. Since the vapor layer or vaporized region has a relatively high electrical impedance, it minimizes the current flow into the electrically conductive fluid. This ionization, under the conditions described herein, induces the discharge of energetic electrons and photons from the vapor layer and to the surface of the target tissue. A more detailed description of this phenomena, termed Coblation ® can be found in commonly assigned U.S. Patent No. 5,697,882 the complete disclosure of which is incorporated herein by reference.
  • the principle mechanism of tissue removal in the Coblation ® mechanism ofthe present invention is energetic electrons or ions that have been energized in a plasma adjacent to the active electrode(s).
  • a liquid is heated enough that atoms vaporize off the surface faster than they recondense, a gas is formed.
  • the gas is heated enough that the atoms collide with each other and knock their electrons off in the process, an ionized gas or plasma is formed (the so-called "fourth state of matter").
  • a more complete description of plasma can be found in Plasma Physics, by R.J. Goldston and P.H. Rutherford ofthe Plasma Physics Laboratory of Princeton University (1995), the complete disclosure of which is incorporated herein by reference.
  • the electron mean free path increases to enable subsequently injected electrons to cause impact ionization within these regions of low density (i.e., vapor layers or bubbles).
  • the ionic particles in the plasma layer have sufficient energy, they accelerate towards the target tissue.
  • Energy evolved by the energetic electrons e.g., 3.5 eV to 5 eV
  • Plasmas may be formed by heating a gas and ionizing the gas by driving an electric current through it, or by shining radio waves into the gas.
  • these methods of plasma formation give energy to free electrons in the plasma directly, and then electron-atom collisions liberate more electrons, and the process cascades until the desired degree of ionization is achieved.
  • the electrons carry the electrical current or absorb the radio waves and, therefore, are hotter than the ions.
  • the electrons which are carried away from the tissue towards the return electrode, carry most ofthe plasma's heat with them, allowing the ions to break apart the tissue molecules in a substantially non-thermal manner.
  • one or more active electrodes are brought into close proximity to tissue at a target site, and the power supply is activated in the ablation mode such that sufficient voltage is applied between the active electrodes and the return electrode to volumetrically remove the tissue through molecular dissociation, as described below.
  • the Coblation ® mechanism of the present invention can be manipulated to ablate or remove certain tissue structures, while having little effect on other tissue structures.
  • the present invention uses a technique of vaporizing electrically conductive fluid to form a plasma layer or pocket around the active electrode(s), and then inducing the discharge of energy from this plasma or vapor layer to break the molecular bonds ofthe tissue structure.
  • the free electrons within the ionized vapor layer are accelerated in the high electric fields near the electrode tip(s).
  • the electron mean free path increases to enable subsequently injected electrons to cause impact ionization within these regions of low density (i.e., vapor layers or bubbles).
  • Energy evolved by the energetic electrons e.g., 4 eV to 5 eV
  • the energy evolved by the energetic electrons may be varied by adjusting a variety of factors, such as: the number of active electrodes; electrode size and spacing; electrode surface area; asperities and sharp edges on the electrode surfaces; electrode materials; applied voltage and power; current limiting means, such as inductors; electrical conductivity ofthe fluid in contact with the electrodes; density ofthe fluid; and other factors. Accordingly, these factors can be manipulated to control the energy level ofthe excited electrons. Since different tissue structures have different molecular bonds, the present invention can be configured to break the molecular bonds of certain tissue, while having too low an energy to break the molecular bonds of other tissue.
  • fatty tissue e.g., adipose
  • fatty tissue e.g., adipose
  • the present invention in its current configuration generally does not ablate or remove such fatty tissue.
  • the present invention may be used to effectively ablate cells to release the inner fat content in a liquid form.
  • factors may be changed such that these double bonds can also be broken in a similar fashion as the single bonds (e.g., increasing voltage or changing the electrode configuration to increase the current density at the electrode tips). A more complete description of this phenomena can be found in U.S. Patent No.
  • the present invention provides systems, apparatus and methods for selectively removing tumors, e.g., spinal tumors, facial tumors, or other undesirable body structures while minimizing the spread of viable cells from the tumor.
  • tumors e.g., spinal tumors, facial tumors, or other undesirable body structures
  • Conventional techniques for removing such tumors generally result in the production of smoke in the surgical setting, termed an electrosurgical or laser plume, which can spread intact, viable bacterial or viral particles from the tumor or lesion to the surgical team or to other portions ofthe patient's body.
  • This potential spread of viable cells or particles has resulted in increased concerns over the proliferation of certain debilitating and fatal diseases, such as hepatitis, herpes, HIV and papillomavirus.
  • high frequency voltage is applied between the active electrode(s) and one or more return electrode(s) to volumetrically remove at least a portion of the tissue cells in the tumor tlirough the dissociation or disintegration of organic molecules into non-viable atoms and molecules.
  • the present invention may provide an immediate removal of tissue. Specifically, the present invention converts the solid tissue cells into non-condensable gases that are no longer intact or viable, and thus, not capable of spreading viable tumor particles to other portions ofthe patient's bone, vessel or brain or to the surgical staff.
  • the high frequency voltage is preferably selected to effect controlled removal of these tissue cells while minimizing substantial tissue necrosis to surrounding or underlying tissue. A more complete description of this phenomena can be found in co-pending U.S.
  • the electrosurgical probe or catheter ofthe present invention can comprise a shaft or a handpiece having a proximal end and a distal end which supports one or more active electrode(s).
  • the shaft or handpiece may assume a wide variety of configurations, with the primary purpose being to mechanically support the active electrode and permit the treating physician to manipulate the electrode from a proximal end ofthe shaft.
  • the shaft may be rigid, bendable, malleable or flexible, with bendable, malleable and flexible shafts optionally being combined with a generally rigid external tube for mechanical support.
  • Flexible shafts may be combined with pull wires, shape memory actuators, and other known mechanisms for effecting selective deflection ofthe distal end ofthe shaft to facilitate positioning ofthe electrode array.
  • the shaft will usually include a plurality of wires or other conductive elements running axially therethrough to permit connection ofthe electrode array to a connector at the proximal end ofthe shaft.
  • the electrosurgical instrument may also be a catheter that is delivered percutaneously and/or endoluminally into the patient by insertion through a conventional or specialized guide catheter, or the invention may include a catheter having an active electrode or electrode array integral with its distal end.
  • the catheter shaft may be rigid or flexible, with flexible shafts optionally being combined with a generally rigid external tube for mechanical support.
  • Flexible shafts may be combined with pull wires, shape memory actuators, and other known mechanisms for effecting selective deflection ofthe distal end ofthe shaft to facilitate positioning ofthe electrode or electrode array.
  • the catheter shaft will usually include a plurality of wires or other conductive elements running axially therethrough to permit connection ofthe electrode or electrode array and the return electrode to a connector at the proximal end ofthe catheter shaft.
  • the catheter shaft may include a guide wire for guiding the catheter to the target site, or the catheter may comprise a steerable guide catheter.
  • the catheter may also include a substantially rigid distal end portion to increase the torque control ofthe distal end portion as the catheter is advanced further into the patient's body. Specific shaft designs will be described in detail in connection with the figures hereinafter.
  • the active electrode(s) are preferably supported within or by an inorganic insulating support positioned near the distal end ofthe instrument shaft.
  • the return electrode may be located on the instrument shaft, on another instrument or on the external surface ofthe patient (i.e., a dispersive pad).
  • a dispersive pad located on the instrument shaft, on another instrument or on the external surface ofthe patient (i.e., a dispersive pad).
  • the return electrode is preferably either integrated with the instrument body, or another instrument located in close proximity thereto.
  • the proximal end ofthe instrument(s) will include the appropriate electrical connections for coupling the return electrode(s) and the active electrode(s) to a high frequency power supply, such as an electrosurgical generator.
  • the active electrode(s) have an active portion or surface with surface geometries shaped to promote the electric field intensity and associated current density along the leading edges ofthe electrodes. Suitable surface geometries may be obtained by creating electrode shapes that include preferential sharp edges, or by creating asperities or other surface roughness on the active surface(s) ofthe electrodes. Electrode shapes according to the present invention can include the use of formed wire (e.g., by drawing round wire through a shaping die) to form electrodes with a variety of cross- sectional shapes, such as square, rectangular, L or V shaped, or the like. Electrode edges may also be created by removing a portion ofthe elongate metal electrode to reshape the cross-section.
  • material can be ground along the length of a round or hollow wire electrode to form D or C shaped wires, respectively, with edges facing in the cutting direction.
  • material can be removed at closely spaced intervals along the electrode length to form transverse grooves, slots, threads or the like along the electrodes.
  • the active electrode surface(s) may be modified tlirough chemical, electrochemical or abrasive methods to create a multiplicity of surface asperities on the electrode surface. These surface asperities will promote high electric field intensities between the active electrode surface(s) and the target tissue to facilitate ablation or cutting of the tissue.
  • surface asperities may be created by etching the active electrodes with etchants having a pH less than 7.0 or by using a high velocity stream of abrasive particles (e.g., grit blasting) to create asperities on the surface of an elongated electrode.
  • abrasive particles e.g., grit blasting
  • the return electrode is typically spaced proximally from the active electrode(s) a suitable distance to avoid electrical shorting between the active and return electrodes in the presence of electrically conductive fluid.
  • the distal edge ofthe exposed surface ofthe return electrode is spaced about 0.5 mm to 25 mm from the proximal edge ofthe exposed surface ofthe active electrode(s), preferably about 1.0 mm to 5.0 mm.
  • this distance may vary with different voltage ranges, conductive fluids, and depending on the proximity of tissue structures to active and return electrodes.
  • the return electrode will typically have an exposed length in the range of about 1 mm to 20 mm.
  • the current flow path between the active electrodes and the return electrode(s) may be generated by submerging the tissue site in an electrical conducting fluid (e.g., within a viscous fluid, such as an electrically conductive gel) or by directing an electrically conductive fluid along a fluid path to the target site (i.e., a liquid, such as isotonic saline, hypotonic saline or a gas, such as argon).
  • the conductive gel may also be delivered to the target site to achieve a slower more controlled delivery rate of conductive fluid.
  • the viscous nature ofthe gel may allow the surgeon to more easily contain the gel around the target site (e.g., rather than attempting to contain isotonic saline).
  • a liquid electrically conductive fluid e.g., isotonic saline
  • the power supply, or generator may include a fluid interlock for interrupting power to the active electrode(s) when there is insufficient conductive fluid around the active electrode(s). This ensures that the instrument will not be activated when conductive fluid is not present, minimizing the tissue damage that may otherwise occur.
  • a fluid interlock can be found in commonly assigned, co-pending U.S. Application No. 09/058,336, filed April 10, 1998, the complete disclosure of which is incorporated herein by reference.
  • the system ofthe present invention may include one or more suction lumen(s) in the instrument, or on another instrument, coupled to a suitable vacuum source for aspirating fluids from the target site.
  • the invention may include one or more aspiration electrode(s) coupled to the distal end ofthe suction lumen for ablating, or at least reducing the volume of, non-ablated tissue fragments that are aspirated into the lumen.
  • the aspiration electrode(s) function mainly to inhibit clogging ofthe lumen that may otherwise occur as larger tissue fragments are drawn therein.
  • the aspiration electrode(s) may be different from the ablation active electrode(s), or the same electrode(s) may serve both functions.
  • a containment apparatus such as a basket, retractable sheath, or the like.
  • This embodiment has the advantage of ensuring that the conductive fluid, tissue fragments or ablation products do not flow through the patient's vasculature or into other portions ofthe body.
  • Apparatuses may use a single active electrode or an array of active electrodes spaced around the distal surface of a catheter or probe.
  • the electrode a ⁇ ay usually includes a plurality of independently current-limited and/or power-controlled active electrodes to apply electrical energy selectively to the target tissue while limiting the unwanted application of electrical energy to the surrounding tissue and environment resulting from power dissipation into surrounding electrically conductive fluids, such as blood, normal saline, and the like.
  • the active electrodes may be independently current-limited by isolating the terminals from each other and connecting each terminal to a separate power source that is isolated from the other active electrodes.
  • the active electrodes may be connected to each other at either the proximal or distal ends ofthe catheter to form a single wire that couples to a power source.
  • each individual active electrode in the electrode array is electrically insulated from all other active electrodes in the array within the instrument and is connected to a power source which is isolated from each ofthe other active electrodes in the array or to circuitry which limits or interrupts current flow to the active electrode when low resistivity material (e.g., blood, electrically conductive saline irrigant or electrically conductive gel) causes a lower impedance path between the return electrode and the individual active electrode.
  • the isolated power sources for each individual active electrode may be separate power supply circuits having internal impedance characteristics which limit power to the associated active electrode when a low impedance return path is encountered.
  • the isolated power source may be a user selectable constant current source.
  • a single power source may be connected to each ofthe active electrodes through independently actuatable switches, or by independent current limiting elements, such as inductors, capacitors, resistors and/or combinations thereof.
  • the current limiting elements may be provided in the instrument, connectors, cable, controller, or along the conductive path from the controller to the distal tip ofthe instrument.
  • the resistance and/or capacitance may occur on the surface ofthe active electrode(s) due to oxide layers which fonn selected active electrodes (e.g., titanium or a resistive coating on the surface of metal, such as platinum).
  • the tip region ofthe instrument may comprise many independent active electrodes designed to deliver electrical energy in the vicinity ofthe tip.
  • the selective application of electrical energy to the conductive fluid is achieved by connecting each individual active electrode and the return electrode to a power source having independently controlled or current limited channels.
  • the return electrode(s) may comprise a single tubular member of conductive material proximal to the electrode array at the tip which also serves as a conduit for the supply ofthe electrically conductive fluid between the active and return electrodes.
  • the instrument may comprise an array of return electrodes at the distal tip of the instrument (together with the active electrodes) to maintain the electric current at the tip.
  • the application of high frequency voltage between the return electrode(s) and the electrode array results in the generation of high electric field intensities at the distal tips ofthe active electrodes with conduction of high frequency current from each individual active electrode to the return electrode.
  • the current flow from each individual active electrode to the return electrode(s) is controlled by either active or passive means, or a combination thereof, to deliver electrical energy to the surrounding conductive fluid while minimizing energy delivery to surrounding (non-target) tissue.
  • the application of a high frequency voltage between the return electrode(s) and the active electrode(s) for appropriate time intervals affects shrinking, cutting, removing, ablating, shaping, contracting or otherwise modifying the target tissue.
  • the tissue volume over which energy is dissipated may be more precisely controlled, for example, by the use of a multiplicity of small active electrodes whose effective diameters or principal dimensions range from about 10 mm to 0.01 mm, preferably from about 2 mm to 0.05 mm, and more preferably from about 1 mm to 0.1 mm.
  • electrode areas for both circular and non-circular te ⁇ ninals will have a contact area (per active electrode) below 50 mm 2 for electrode arrays and as large as 75 mm for single electrode embodiments.
  • the contact area of each active electrode is typically in the range from 0.0001 mm 2 to 1 mm 2 , and more preferably from 0.001 mm 2 to .5 mm 2 .
  • the circumscribed area ofthe electrode array or active electrode is in the range from 0.25 mm 2 to 75 mm , preferably from 0.5 mm to 40 mm .
  • the array will usually include at least two isolated active electrodes, often at least five active electrodes, often greater than 10 active electrodes and even 50 or more active electrodes, disposed over the distal contact surfaces on the shaft.
  • tissue treatment surface can vary widely, and the tissue treatment surface can assume a variety of geometries, with particular areas and geometries being selected for specific applications.
  • the geometries can be planar, concave, convex, hemispherical, conical, linear "in-line” array or virtually any other regular or irregular shape.
  • the active electrode(s) or active electrode(s) will be formed at the distal tip ofthe electrosurgical instrument shaft, frequently being planar, disk-shaped, or hemispherical surfaces for use in reshaping procedures or being linear arrays for use in cutting.
  • the active electrode(s) may be formed on lateral surfaces ofthe electrosurgical instrument shaft (e.g., in the manner of a spatula), facilitating access to certain body structures in endoscopic procedures.
  • the invention is not limited to electrically isolated active electrodes, or even to a plurality of active electrodes.
  • the array of active electrodes may be connected to a single lead that extends through the catheter shaft to a power source of high frequency current.
  • the instrument may incorporate a single electrode that extends directly through the catheter shaft or is connected to a single lead that extends to the power source.
  • the active electrode(s) may have ball shapes (e.g., for tissue vaporization and desiccation), twizzle shapes (for vaporization and needle-like cutting), spring shapes (for rapid tissue debulking and desiccation), twisted metal shapes, annular or solid tube shapes or the like.
  • the electrode(s) may comprise a plurality of filaments, rigid or flexible brush electrode(s) (for debulking a tumor, such as a fibroid, bladder tumor or a prostate adenoma), side-effect brush electrode(s) on a lateral surface ofthe shaft, coiled electrode(s) or the like.
  • the electrode support and the fluid outlet may be recessed from an outer surface ofthe instrument or handpiece to confine the electrically conductive fluid to the region immediately surrounding the electrode support.
  • the shaft may be shaped so as to form a cavity around the electrode support and the fluid outlet. This helps to assure that the electrically conductive fluid will remain in contact with the active electrode(s) and the return electrode s) to maintain the conductive path therebetween.
  • the active electrodes are spaced from the tissue a sufficient distance to minimize or avoid contact between the tissue and the vapor layer formed around the active electrodes. In these embodiments, contact between the heated electrons in the vapor layer and the tissue is minimized as these electrons travel from the vapor layer back through the conductive fluid to the return electrode.
  • the electrically conductive fluid should have a threshold conductivity to provide a suitable conductive path between the return electrode and the active electrode(s).
  • the electrical conductivity ofthe fluid (in units of millisiemens per centimeter or mS/cm) will usually be greater than 0.2 mS/cm, preferably will be greater than 2 mS/cm and more preferably greater than 10 mS/cm.
  • the electrically conductive fluid is isotonic saline, which has a conductivity of about 17 mS/cm.
  • a more conductive fluid, or one with a higher ionic concentration will usually provide a more aggressive ablation rate.
  • a saline solution with higher levels of sodium chloride than conventional saline which is on the order of about 0.9% sodium chloride
  • the invention may be used with different types of conductive fluids that increase the power ofthe plasma layer by, for example, increasing the quantity of ions in the plasma, or by providing ions that have higher energy levels than sodium ions.
  • the present invention may be used with elements other than sodium, such as potassium, magnesium, calcium and other metals near the left end ofthe periodic chart.
  • other electronegative elements may be used in place of chlorine, such as fluorine.
  • the voltage difference applied between the return electrode(s) and the active electrode(s) will be at high or radio frequency, typically between about 5 kHz and 20 MHz, usually being between about 30 kHz and 2.5 MHz, preferably being between about 50 kHz and 500 kHz, often less than 350 kHz, and often between about 100 kHz and 200 kHz. In some applications, applicant has found that a frequency of about 100 kHz is useful because the tissue impedance is much greater at this frequency.
  • RMS root mean square
  • the RMS (root mean square) voltage applied will usually be in the range from about 5 volts to 1000 volts, preferably being in the range from about 10 volts to 500 volts, often between about 150 volts to 400 volts depending on the active electrode size, the operating frequency and the operation mode ofthe particular procedure or desired effect on the tissue (i.e., contraction, coagulation, cutting or ablation).
  • the peak-to-peak voltage for ablation or cutting with a square wave form will be in the range of 10 volts to 2000 volts and preferably in the range of 100 volts to 1800 volts and more preferably in the range of about 300 volts to 1500 volts, often in the range of about 300 volts to 800 volts peak to peak (again, depending on the electrode size, number of electrons, the operating frequency and the operation mode).
  • Lower peak-to-peak voltages will be used for tissue coagulation, thermal heating of tissue, or collagen contraction and will typically be in the range from 50 to 1500, preferably 100 to 1000 and more preferably 120 to 400 volts peak-to-peak (again, these values are computed using a square wave form).
  • the voltage is usually delivered in a series of voltage pulses or alternating current of time varying voltage amplitude with a sufficiently high frequency (e.g., on the order of 5 kHz to 20 MHz) such that the voltage is effectively applied continuously (as compared with e.g., lasers claiming small depths of necrosis, which are generally pulsed about 10 Hz to 20 Hz).
  • the duty cycle i.e., cumulative time in any one-second interval that energy is applied
  • the duty cycle is on the order of about 50% for the present invention, as compared with pulsed lasers which typically have a duty cycle of about 0.0001%.
  • the preferred power source ofthe present invention delivers a high frequency current selectable to generate average power levels ranging from several milliwatts to tens of watts per electrode, depending on the volume of target tissue being treated, and/or the maximum allowed temperature selected for the instrument tip.
  • the power source allows the user to select the voltage level according to the specific requirements of a particular spinal surgery, neurosurgery procedure, cardiac surgery, arthroscopic surgery, dermatological procedure, ophthalmic procedures, open surgery or other endoscopic surgery procedure.
  • the power source may have an additional filter, for filtering leakage voltages at frequencies below 100 kHz, particularly voltages around 60 kHz.
  • a power source having a higher operating frequency e.g., 300 kHz to 600 kHz may be used in certain procedures in which stray low frequency currents may be problematic.
  • a description of one suitable power source can be found in co-pending Patent Applications 09/058,571 and 09/058,336, filed April 10, 1998, the complete disclosure of both applications are incorporated herein by reference for all purposes.
  • the power source may be current limited or otherwise controlled so that undesired heating ofthe target tissue or surrounding (non-target) tissue does not occur.
  • current limiting inductors are placed in series with each independent active electrode, where the inductance ofthe inductor is in the range of lOuH to 50,000uH, depending on the electrical properties ofthe target tissue, the desired tissue heating rate and the operating frequency.
  • capacitor-inductor (LC) circuit structures may be employed, as described previously in U.S. Patent No. 5,697,909, the complete disclosure of which is incorporated herein by reference. Additionally, current- limiting resistors may be selected.
  • Electrosurgical system 11 generally comprises an electrosurgical handpiece or probe 10 connected to a power supply 28 for providing high frequency voltage to a target site, and a fluid source 21 for supplying electrically conductive fluid 50 to probe 10.
  • electrosurgical system 11 may include an endoscope (not shown) with a fiber optic headlight for viewing the surgical site.
  • the endoscope may be integral with probe 10, or it may be part of a separate instrument.
  • the system 11 may also include a vacuum source (not shown) for coupling to a suction lumen or tube 211 (see Fig. 4) in the probe 10 for aspirating the target site.
  • probe 10 generally includes a proximal handle 19 and an elongate shaft 18 having an array 12 of active electrodes 58 at its distal end.
  • a connecting cable 34 has a connector 26 for electrically coupling the active electrodes 58 to power supply 28.
  • the active electrodes 58 are electrically isolated from each other and each of electrodes 58 is connected to an active or passive control network within power supply 28 by means of a plurality of individually insulated conductors (not shown).
  • a fluid supply tube 15 is connected to a fluid tube 14 of probe 10 for supplying electrically conductive fluid 50 to the target site. Fluid supply tube 15 may be connected to a suitable pump (not shown), if desired.
  • Power supply 28 has an operator controllable voltage level adjustment 30 to change the applied voltage level, which is observable at a voltage level display 32.
  • Power supply 28 also includes first, second and tliird foot pedals 37, 38, 39 and a cable 36 which is removably coupled to power supply 28.
  • first foot pedal 37 is used to place the power supply into the "ablation” mode and second foot pedal 38 places power supply 28 into the "sub-ablation” mode (e.g., for coagulation or contraction of tissue).
  • the third foot pedal 39 allows the user to adjust the voltage level within the
  • ablation In the ablation mode, a sufficient voltage is applied to the active electrodes to establish the requisite conditions for molecular dissociation ofthe tissue (i.e., vaporizing a portion ofthe electrically conductive fluid, ionizing charged particles within the vapor layer and accelerating these charged particles against the tissue). As discussed above, the requisite voltage level for ablation will vary depending on the number, size, shape and spacing ofthe electrodes, the distance in which the electrodes extend from the support member, etc. Once the surgeon places the power supply in the "ablation” mode, voltage level adjustment 30 or third foot pedal 39 may be used to adjust the voltage level to adjust the degree or aggressiveness ofthe ablation.
  • the voltage and modality ofthe power supply may be controlled by other input devices.
  • foot pedals are convenient methods of controlling the power supply while manipulating the probe during a surgical procedure.
  • the power supply 28 applies a low enough voltage to the active electrodes to avoid vaporization ofthe electrically conductive fluid and subsequent molecular dissociation ofthe tissue.
  • the surgeon may automatically toggle the power supply between the ablation and sub-ablation modes by alternately stepping on foot pedals 37, 38, respectively. In some embodiments, this allows the surgeon to quickly move between coagulation/thermal heating and ablation in situ, without having to remove his/her concentration from the surgical field or without having to request an assistant to switch the power supply.
  • the probe typically will simultaneously seal and/or coagulation small severed vessels within the tissue.
  • larger vessels, or vessels with high fluid pressures e.g., arterial vessels
  • the surgeon can simply step on foot pedal 38, automatically lowering the voltage level below the threshold level for ablation, and apply sufficient pressure onto the severed vessel for a sufficient period of time to seal and/or coagulate the vessel. After this is completed, the surgeon may quickly move back into the ablation mode by stepping on foot pedal 37.
  • Figs. 2B and 3 a representative high frequency power supply for use according to the principles ofthe present invention will now be described.
  • the high frequency power supply of the present invention is configured to apply a high frequency voltage of about 10 volts RMS to 500 volts RMS between one or more active electrodes (and/or coagulation electrode) and one or more return electrodes.
  • the power supply applies about 70 volts RMS to 350 volts RMS in the ablation mode and about 20 volts to 90 volts in a subablation mode, preferably 45 volts to 70 volts in the subablation mode (these values will, of course, vary depending on the probe configuration attached to the power supply and the desired mode of operation).
  • the preferred power source ofthe present invention delivers a high frequency current selectable to generate average power levels ranging from several milliwatts to tens of watts per electrode, depending on the volume of target tissue being treated, and/or the maximum allowed temperature selected for the probe tip.
  • the power supply allows the user to select the voltage level according to the specific requirements of a particular procedure, e.g., spinal surgery, arthroscopic surgery, dermatological procedure, ophthalmic procedures, open surgery, or other endoscopic surgery procedure.
  • the power supply generally comprises a radio frequency (RF) power oscillator 70 having output connections for coupling via a power output signal 71 to the load impedance, which is represented by the electrode assembly when the electrosurgical probe is in use.
  • RF radio frequency
  • the RF oscillator operates at about 100 kHz.
  • the RF oscillator is not limited to this frequency and may operate at frequencies of about 300kHz to 600kHz. In particular, for cardiac applications, the RF oscillator will preferably operate in the range of about 400 kHz to about 600 kHz.
  • the RF oscillator will generally supply a square wave signal with a crest factor of about 1 to 2. Of course, this signal may be a sine wave signal or other suitable wave signal depending on the application and other factors, such as the voltage applied, the number and geometry of the electrodes, etc.
  • the power output signal 71 is designed to incur minimal voltage decrease (i.e., sag) under load.
  • RF oscillator 70 Power is supplied to RF oscillator 70 by a switching power supply 72 coupled between the power line and the RF oscillator rather than a conventional transformer.
  • the switching power supply 72 allows power supply 28 to achieve high peak power output without the large size and weight of a bulky transformer.
  • the architecture ofthe switching power supply also has been designed to reduce electromagnetic noise such that U.S. and foreign EMI requirements are met. This architecture comprises a zero voltage switching or crossing, which causes the transistors to turn ON and OFF when the voltage is zero. Therefore, the electromagnetic noise produced by the transistors switching is vastly reduced.
  • the switching power supply 72 operates at about 100 kHz.
  • the controller 74 may be a microprocessor or an integrated circuit.
  • the power supply may also include one or more current sensors 75 for detecting the output current.
  • the power supply is preferably housed within a metal casing which provides a durable enclosure for the electrical components therein. In addition, the metal casing reduces the electromagnetic noise generated within the power supply because the grounded metal casing functions as a "Faraday shield," thereby shielding the environment from internal sources of electromagnetic noise.
  • the power supply generally comprises a main or motherboard containing generic electrical components required for many different surgical procedures (e.g., arthroscopy, urology, general surgery, dermatology, neurosurgery, etc.), and a daughter board containing application specific current-limiting circuitry (e.g., inductors, resistors, capacitors and the like).
  • the daughter board is coupled to the mother board by a detachable multi-pin connector to allow convenient conversion ofthe power supply to, e.g., applications requiring a different current limiting circuit design.
  • the daughter board preferably comprises a plurality of inductors of about 200 to 400 microhenries, usually about 300 microhenries, for each ofthe channels supplying current to the active electrodes 102 (see Fig.
  • current limiting inductors are placed in series with each independent active electrode, where the inductance ofthe inductor is in the range of lOuH to 50,000uH, depending on the electrical properties ofthe target tissue, the desired tissue heating rate and the operating frequency.
  • capacitor-inductor (LC) circuit structures may be employed, as described previously in co-pending PCT application No. PCT/US94/05168, the complete disclosure of which is incorporated herein by reference. Additionally, current-limiting resistors may be selected.
  • these resistors will have a large positive temperature coefficient of resistance so that, as the current level begins to rise for any individual active electrode in contact with a low resistance medium (e.g., saline irrigant or conductive gel), the resistance ofthe current limiting resistor increases significantly, thereby minimizing the power delivery from the active electrode into the low resistance medium (e.g., saline irrigant or conductive gel).
  • Power output signal may also be coupled to a plurality of current limiting elements 96, which are preferably located on the daughter board since the current limiting elements may vary depending on the application.
  • probe 20 generally includes an elongated shaft 100 which may be flexible, malleable, bendable or rigid, a handle 204 coupled to the proximal end of shaft 100 and an electrode support member 102 coupled to the distal end of shaft 100.
  • Shaft 100 preferably comprises an electrically conductive material, usually metal, which is selected from the group comprising tungsten, stainless steel alloys, platinum or its alloys, titanium or its alloys, molybdenum or its alloys, and nickel or its alloys.
  • shaft 100 includes an electrically insulating jacket 108, which is typically formed as one or more electrically insulating sheaths or coatings, such as polytetrafluoroethylene, polyimide, and the like.
  • electrically insulating jacket 108 is typically formed as one or more electrically insulating sheaths or coatings, such as polytetrafluoroethylene, polyimide, and the like.
  • the provision ofthe electrically insulating jacket over the shaft prevents direct electrical contact between these metal elements and any adjacent body structure or the surgeon.
  • Such direct electrical contact between a body structure (e.g., tendon) and an exposed electrode could result in unwanted heating and necrosis ofthe structure at the point of contact causing necrosis.
  • the return electrode may comprise an annular band coupled to an insulating shaft and having a connector extending within the shaft to its proximal end.
  • Handle 204 typically comprises a plastic material that is easily molded into a suitable shape for handling by the surgeon. Handle 204 defines an inner cavity (not shown) that houses the electrical connections 250 (Fig. 6), and provides a suitable interface for connection to an electrical connecting cable distal portion 22 (see Fig. 2 A) Electrode support member 102 extends from the distal end of shaft 100 (usually about 1 mm to 20 mm), and provides support for a plurality of electrically isolated active electrodes 104 (see Fig. 5). As shown in Fig. 4, a fluid tube 233 extends tlirough an opening in handle 204, and includes a connector 235 for connection to a fluid supply source, for supplying electrically conductive fluid to the target site.
  • fluid tube 233 may extend through a single lumen (not shown) in shaft 100, or it may be coupled to a plurality of lumens (also not shown) that extend through shaft 100 to a plurality of openings at its distal end.
  • tubing 239 is a tube that extends along the exterior of shaft 100 to a point just distal of return electrode 112 (see Fig. 5).
  • the fluid is directed through an opening 237 past return electrode 112 to the active electrodes 104.
  • Probe 20 may also include a valve 17 (Fig. 2A) or equivalent structure for controlling the flow rate ofthe electrically conductive fluid to the target site. As shown in Fig.
  • Electrode support member 102 has a substantially planar tissue treatment surface 212 (Fig. 5) that is usually at an angle of about 10 degrees to 90 degrees relative to the longitudinal axis of shaft 100, preferably less than about 60 degrees and more preferably less than about 45 degrees.
  • the distal portion of shaft 100 comprises a flexible material which can be deflected relative to the longitudinal axis ofthe shaft. Such deflection may be selectively induced by mechanical tension of a pull wire, for example, or by a shape memory wire that expands or contracts by externally applied temperature changes. A more complete description of this embodiment can be found in U.S. Patent No.
  • probe 20 includes a return electrode 112 for completing the current path between active electrodes 104 and a high frequency power supply 28 (see Fig. 2 A).
  • return electrode 112 preferably comprises an exposed portion of shaft 100 shaped as an annular conductive band near the distal end of shaft 100 slightly proximal to tissue treatment surface 212 of electrode support member 102, typically about 0.5 mm to 10 mm and more preferably about 1 mm to 10 mm.
  • Return electrode 112 or shaft 100 is coupled to a connector 258 that extends to the proximal end of probe 10/20, where it is suitably connected to power supply 28 (Fig. 2A). As shown in Fig. 4, return electrode 112 is not directly connected to active electrodes 104. To complete this current path so that active electrodes 104 are electrically connected to return electrode 112, an electrically conductive fluid (e.g., isotonic saline) is caused to flow therebetween.
  • the electrically conductive fluid is delivered through fluid tube 233 to opening 237, as described above.
  • the conductive fluid may be delivered by a fluid delivery element (not shown) that is separate from probe 20.
  • the target area ofthe joint will be flooded with isotonic saline and the probe 90 will be introduced into this flooded target area.
  • Electrically conductive fluid can be continually resupplied to maintain the conduction path between return electrode 112 and active electrodes 104.
  • the distal portion of probe 20 may be dipped into a source of electrically conductive fluid, such as a gel or isotonic saline, prior to positioning at the target site. Applicant has found that the surface tension ofthe fluid and/or the viscous nature of a gel allows the conductive fluid to remain around the active and return electrodes for long enough to complete its function according to the present invention, as described below.
  • the conductive fluid such as a gel
  • the fluid path may be formed in probe 90 by, for example, an inner lumen or an annular gap between the return electrode and a tubular support member within shaft 100 (see Figs. 8 A and 8B). This annular gap may be formed near the perimeter ofthe shaft 100 such that the electrically conductive fluid tends to flow radially inward towards the target site, or it may be formed towards the center of shaft 100 so that the fluid flows radially outward.
  • a fluid source e.g., a bag of fluid elevated above the surgical site or having a pumping device
  • a fluid supply tube (not shown) that may or may not have a controllable valve.
  • an electrosurgical probe incorporating one or more fluid lumen(s) can be found in U.S. Patent No. 5,697,281, the complete disclosure of which has previously been incorporated herein by reference.
  • the electrically isolated active electrodes 104 are spaced apart over tissue treatment surface 212 of electrode support member 102. The tissue treatment surface and individual active electrodes 104 will usually have dimensions within the ranges set forth above.
  • the tissue treatment surface 212 has a circular cross-sectional shape with a diameter in the range of 1 mm to 20 mm.
  • the individual active electrodes 104 preferably extend outward from tissue treatment surface 212 by a distance of about 0.1 mm to 4 mm, usually about 0.2 mm to 2 mm. Applicant has found that this configuration increases the high electric field intensities and associated current densities around active electrodes 104 to facilitate the ablation and shrinkage of tissue as described in detail above.
  • the probe includes a single, larger opening 209 in the center of tissue treatment surface 212, and a plurality of active electrodes (e.g., about 3- 15) around the perimeter of surface 212 (see Fig. 5).
  • the probe may include a single, annular, or partially annular, active electrode at the perimeter ofthe tissue treatment surface.
  • the central opening 209 is coupled to a suction lumen (not shown) within shaft 100 and a suction tube 211 (Fig. 4) for aspirating tissue, fluids and/or gases from the target site.
  • the electrically conductive fluid generally flows radially inward past active electrodes 104 and then back through the opening 209. Aspirating the electrically conductive fluid during surgery allows the surgeon to see the target site, and it prevents the fluid from flowing into the patient's body.
  • the distal tip of an electrosurgical probe ofthe invention e.g., probe 10/20/90, may have a variety of different configurations.
  • the probe may include a plurality of openings 209 around the outer perimeter of tissue treatment surface 212 (see Fig. 7B).
  • the active electrodes 104 extend distally from the center of tissue treatment surface 212 such that they are located radially inward from openings 209.
  • the openings are suitably coupled to fluid tube 233 for delivering electrically conductive fluid to the target site, and suction tube 211 for aspirating the fluid after it has completed the conductive path between the return electrode 112 and the active electrodes 104.
  • Fig. 6 illustrates the electrical connections 250 within handle 204 for coupling active electrodes 104 and return electrode 112 to the power supply 28.
  • the probe 20 further includes an identification element that is characteristic ofthe particular electrode assembly so that the same power supply 28 can be used for different electrosurgical operations.
  • the probe e.g., 20
  • the probe includes a voltage reduction element or a voltage reduction circuit for reducing the voltage applied between the active electrodes 104 and the return electrode 112.
  • the voltage reduction element serves to reduce the voltage applied by the power supply so that the voltage between the active electrodes and the return electrode is low enough to avoid excessive power dissipation into the electrically conducting medium and/or ablation ofthe soft tissue at the target site,
  • the voltage reduction element allows the power supply 28 to apply two different voltages simultaneously to two different electrodes (see Fig. 7D).
  • the voltage reduction element primarily allows the electrosurgical probe to be compatible with various electrosurgical generators supplied by ArthroCare Corporation (Sunnyvale, CA) that are adapted to apply higher voltages for ablation or vaporization of tissue.
  • the voltage reduction element will serve to reduce a voltage of about 100 volts rms to 170 volts rms (which is a setting of 1 or 2 on the ArthroCare Model 970 and 980 (i.e., 2000) Generators) to about 45 volts rms to 60 volts rms, which is a suitable voltage for coagulation of tissue without ablation (e.g., molecular dissociation) ofthe tissue.
  • the probe will typically not require a voltage reduction element.
  • the probe may include a voltage increasing element or circuit, if desired.
  • the cable 34 and/or cable distal end 22 that couples the power supply 28 to the probe may be used as a voltage reduction element.
  • the cable has an inherent capacitance that can be used to reduce the power supply voltage if the cable is placed into the electrical circuit between the power supply, the active electrodes and the return electrode.
  • the cable distal end 22 may be used alone, or in combination with one ofthe voltage reduction elements discussed above, e.g., a capacitor.
  • the present invention can be used with a power supply that is adapted to apply a voltage within the selected range for treatment of tissue, hi this embodiment, a voltage reduction element or circuitiy may not be desired. Figs.
  • probe 350 comprises an electrically conductive shaft 352, a handle 354 coupled to the proximal end of shaft 352 and an electrically insulating support member 356 at the distal end of shaft 352.
  • Probe 350 further includes a shrink wrapped insulating sleeve 358 over shaft 352, and an exposed portion of shaft 352 that functions as the return electrode 360.
  • probe 350 comprises a plurality of active electrodes 362 extending from the distal end of support member 356. As shown, return electrode 360 is spaced a further distance from active electrodes 362 than in the embodiments described above.
  • the return electrode 360 is spaced a distance of about 2.0 mm to 50 mm, preferably about 5 mm to 25 mm from active electrodes 362.
  • return electrode 360 has a larger exposed surface area than in previous embodiments, having a length in the range of about 2.0 mm to 40 mm, preferably about 5 mm to 20 mm. Accordingly, electric current passing from active electrodes 362 to return electrode 360 will follow a current flow path 370 that is further away from shaft 352 than in the previous embodiments. In some applications, this current flow path 370 results in a deeper current penetration into the surrounding tissue with the same voltage level, and thus increased thermal heating ofthe tissue. As discussed above, this increased thermal heating may have advantages in some applications of treating disc or other spinal abnormalities.
  • a tissue temperature in the range of about 60°C to 100°C to a depth of about 0.2 mm to 5 mm, usually about 1 mm to 2 mm.
  • the voltage required for this thermal damage will partly depend on the electrode configurations, the conductivity ofthe tissue and the area immediately surrounding the electrodes, the time period in which the voltage is applied and the depth of tissue damage desired. With the electrode configurations described in Figs. 7A- 7D, the voltage level for thermal heating will usually be in the range of about 20 volts rms to 300 volts rms, preferably about 60 volts rms to 200 volts rms.
  • the peak-to-peak voltages for thermal heating with a square wave form having a crest factor of about 2 are typically in the range of about 40 to 600 volts peak-to-peak, preferably about 120 to 400 volts peak-to-peak. The higher the voltage is within this range, the less time required. If the voltage is too high, however, the surface tissue may be vaporized, debulked or ablated, which is undesirable.
  • a dispersive return electrode 450 (see Fig. 8) for switching between bipolar and monopolar modes.
  • the system will switch between an ablation mode, where the dispersive pad 450 is deactivated and voltage is applied between active and return electrodes 362, 360, and a subablation or thermal heating mode, where the active electrode(s) 362 are deactivated and voltage is applied between the dispersive pad 450 and the return electrode 360.
  • a subablation or thermal heating mode where the active electrode(s) 362 are deactivated and voltage is applied between the dispersive pad 450 and the return electrode 360.
  • a lower voltage is typically applied and the return electrode 360 functions as the active electrode to provide thermal heating and/or coagulation of tissue surrounding return electrode 360.
  • Fig. 7B illustrates yet another probe.
  • electrosurgical probe 350 comprises an electrode assembly 372 having one or more active electrode(s) 362 and a proximally spaced return electrode 360 as in previous embodiments.
  • Return electrode 360 is typically spaced about 0.5 mm to 25 mm, preferably 1.0 mm to 5.0 mm from the active electrode(s) 362, and has an exposed length of about 1 mm to 20 mm.
  • electrode assembly 372 includes two additional electrodes 374, 376 spaced axially on either side of return electrode 360. Electrodes 374, 376 are typically spaced about 0.5 mm to 25 mm, preferably about 1 mm to 5 mm from return electrode 360.
  • the additional electrodes 374, 376 are exposed portions of shaft 352, and the return electrode 360 is electrically insulated from shaft 352 such that a voltage difference may be applied between electrodes 374, 376 and electrode 360.
  • probe 350 may be used in at least two different modes, an ablation mode and a subablation or thermal heating mode.
  • ablation mode voltage is applied between active electrode(s) 362 and return electrode 360 in the presence of electrically conductive fluid, as described above.
  • electrodes 374, 376 are deactivated.
  • Fig. 7B illustrates another probe 350 incorporating an electrode assembly 372 having one or more active electrode(s) 362 and a proximally spaced return electrode 360 as in previous embodiments.
  • Return electrode 360 is typically spaced about 0.5 mm to 25 mm, preferably 1.0 mm to 5.0 mm from the active electrode(s) 362, and has an exposed length of about 1 mm to 20 mm.
  • electrode assembly 372 includes a second active electrode 380 separated from return electrode 360 by an electrically insulating spacer 382.
  • handle 354 includes a switch 384 for toggling probe 350 between at least two different modes, an ablation mode and a subablation or thermal heating mode. In the ablation mode, voltage is applied between active electrode(s) 362 and return electrode 360 in the presence of electrically conductive fluid, as described above. In the ablation mode, electrode 380 is deactivated.
  • active electrode(s) 362 may be deactivated and a voltage difference is applied between electrode 380 and electrode 360 such that a high frequency current 370 flows therebetween.
  • active electrode(s) 362 may not be deactivated as the higher resistance ofthe smaller electrodes may automatically send the electric current to electrode 380 without having to physically decouple electrode(s) 362 from the circuit.
  • a lower voltage is typically applied below the threshold for plasma formation and ablation, but sufficient to cause some thermal damage to the tissue immediately surrounding the electrodes without vaporizing or otherwise debulking this tissue so that the current 370 provides thermal heating and/or coagulation of tissue surrounding electrodes 360, 380.
  • electrosurgical probe 350 may include a plurality of helical bands formed around shaft 352, with one or more ofthe helical bands having an electrode coupled to the portion ofthe band such that one or more electrodes are formed on shaft 352 spaced axially from each other.
  • Fig. 7D illustrates another probe designed for channeling tlirough tissue and creating lesions. This probe may be useful in a wide variety of applications such as, for example, treatment of spinal discs and/or snoring and sleep apnea. As shown, probe 350 is similar to the probe in Fig.
  • active electrode 362 comprises a single electrode wire extending distally from insulating support member 356.
  • the active electrode 362 may have a variety of configurations to increase the current densities on its surfaces, e.g., a conical shape tapering to a distal point, a hollow cylinder, loop electrode and the like.
  • support members 356 and 382 are constructed of a material, such as ceramic, glass, silicone and the like.
  • the proximal support member 382 may also comprise a more conventional organic material as this support member 382 will generally not be in the presence of a plasma that would otherwise etch or wear away an organic material.
  • the probe 350 in Fig. 7D does not include a switching element. In this embodiment, all three electrodes are activated when the power supply is activated.
  • the return electrode 360 has an opposite polarity from the active and coagulation electrodes 362, 380 such that current 370 flows from the latter electrodes to the return electrode 360 as shown.
  • the electrosurgical system includes a voltage reduction element or a voltage reduction circuit for reducing the voltage applied between the coagulation electrode 380 and return electrode 360. The voltage reduction element allows the power supply 28 to, in effect, apply two different voltages simultaneously to two different electrodes.
  • the operator may apply a voltage sufficient to provide ablation of the tissue at the tip ofthe probe (i.e., tissue adjacent to the active electrode 362).
  • the voltage applied to the coagulation electrode 380 will be insufficient to ablate tissue.
  • the voltage reduction element will serve to reduce a voltage of about 100 volts rms to 300 volts rms to about 45 volts rms to 90 volts rms, which is a suitable voltage for coagulation of tissue without ablation (e.g., molecular dissociation) ofthe tissue.
  • the voltage reduction element comprises a pair of capacitors forming a bridge divider(not shown) coupled to the power supply and coagulation electrode 380.
  • the capacitors usually have a capacitance of about 200 pF to 500 pF (at 500 volts) and preferably about 300 pF to 350 pF (at 500 volts).
  • the capacitors may be located in other places within the system, such as in, or distributed along the length of, the cable, the generator, the connector, etc.
  • other voltage reduction elements such as diodes, transistors, inductors, resistors, capacitors or combinations thereof, may be used in conjunction with the present invention.
  • the probe 350 may include a coded resistor (not shown) that is constructed to lower the voltage applied between the return and coagulation electrodes 360, 380, respectively.
  • electrical circuits may be employed for this purpose.
  • the probe will typically not require a voltage reduction element.
  • the probe may include a voltage increasing element or circuit, if desired.
  • cable 22/34 that couples power supply 28 to the probe 90 may be used as a voltage reduction element. The cable has an inherent capacitance that can be used to reduce the power supply voltage if the cable is placed into the electrical circuit between the power supply, the active electrodes and the return electrode.
  • cable 22/34 may be used alone, or in combination with one ofthe voltage reduction elements discussed above, e.g., a capacitor. Further, it should be noted that the present invention can be used with a power supply that is adapted to apply two different voltages within the selected range for treatment of tissue. In this embodiment, a voltage reduction element or circuitry may not be desired.
  • the probe 350 is manufactured by first inserting an electrode wire (active electrode 362) through a ceramic tube (insulating member 356) such that a distal portion ofthe wire extends through the distal portion ofthe tube, and bonding the wire to the tube, typically with an appropriate epoxy.
  • a stainless steel tube (return electrode 360) is then placed over the proximal portion ofthe ceramic tube, and a wire (e.g., nickel wire) is bonded, typically by spot welding, to the inside surface ofthe stainless steel tube.
  • the stainless steel tube is coupled to the ceramic tube by epoxy, and the device is cured in an oven or other suitable heat source.
  • a second ceramic tube (insulating member 382) is then placed inside ofthe proximal portion ofthe stainless steel tube, and bonded in a similar manner.
  • the shaft 358 is then bonded to the proximal portion ofthe second ceramic tube, and an insulating sleeve (e.g., polyimide) is wrapped around shaft 358 such that only a distal portion ofthe shaft is exposed (i.e., coagulation electrode 380).
  • the nickel wire connection will extend through the center of shaft 358 to connect return electrode 360 to the power supply.
  • the active electrode 362 may form a distal portion of shaft 358, or it may also have a connector extending through shaft 358 to the power supply. In use, the physician positions active electrode 362 adjacent to the tissue surface to be treated (e.g., a spinal disc).
  • the power supply is activated to provide an ablation voltage between active and return electrodes 362, 360, respectively, and a coagulation or thermal heating voltage between coagulation and return electrodes 380, 360, respectively.
  • An electrically conductive fluid can then be provided around active electrode 362, and in the junction between the active and return electrodes 360, 362 to provide a current flow path therebetween. This may be accomplished in a variety of manners, as discussed above.
  • the active electrode 362 is then advanced through the space left by the ablated tissue to form a channel in the disc. During ablation, the electric current between the coagulation and return electrode is typically insufficient to cause any damage to the surface ofthe tissue as these electrodes pass through the tissue surface into the channel created by active electrode 362.
  • the physician Once the physician has formed the channel to the appropriate depth, he or she will cease advancement ofthe active electrode, and will either hold the instrument in place for approximately 5 seconds to 30 seconds, or can immediately remove the distal tip ofthe instrument from the channel (see detailed discussion of this below). In either event, when the active electrode is no longer advancing, it will eventually stop ablating tissue.
  • an open circuit Prior to entering the channel formed by the active electrode 362, an open circuit exists between return and coagulation electrodes 360, 380. Once coagulation electrode 380 enters this channel, electric current will flow from coagulation electrode 380, through the tissue surrounding the channel, to return electrode 360. This electric current will heat the tissue immediately surrounding the channel to coagulate any severed vessels at the surface of the channel.
  • FIG. 8 illustrates yet another embodiment of an electrosurgical system 440 incorporating a dispersive return pad 450 attached to the electrosurgical probe 400.
  • the invention functions in the bipolar mode as described above.
  • the system 440 may function in a monopolar mode in which a high frequency voltage difference is applied between the active electrode(s) 410, and the dispersive return pad 450.
  • the pad 450 and the probe 400 are coupled together, and are both disposable, single-use items.
  • the pad 450 includes an electrical connector 452 that extends into handle 404 of probe 400 for direct connection to the power supply.
  • the invention would also be operable with a standard return pad that connects directly to the power supply.
  • the power supply 460 will include a switch, e.g., a foot pedal 462, for switching between the monopolar and bipolar modes.
  • the return path on the power supply is coupled to return electrode 408 on probe 400, as described above.
  • the return path on the power supply is coupled to connector 452 of pad 450, active electrode(s) 410 are decoupled from the electrical circuit, and return electrode 408 functions as the active electrode. This allows the surgeon to switch between bipolar and monopolar modes during, or prior to, the surgical procedure.
  • the dispersive return pad 450 is adapted for coupling to an external surface ofthe patient in a region substantially close to the target region. For example, during the treatment of tissue in the head and neck, the dispersive return pad is designed and constructed for placement in or around the patient's shoulder, upper back or upper chest region.
  • Fig. 9 is a side view of an electrosurgical probe 900, according to one embodiment of the invention.
  • Probe 900 includes a shaft 902 having a distal end portion 902a and a proximal end portion 902b.
  • An active electrode 910 is disposed on distal end portion 902a. Although only one active electrode is shown in Fig. 9, embodiments including a plurality of active electrodes are also within the scope ofthe invention.
  • Probe 900 further includes a handle 904 which houses a connection block 906 for coupling electrodes, e.g. active electrode 910, thereto.
  • Com ection block 906 includes a plurality of pins 908 adapted for coupling probe 900 to a power supply unit, e.g., power supply 28 (Fig. 2A).
  • Fig. 10 is a side view ofthe distal end portion ofthe electrosurgical probe of Fig. 9, showing details of shaft distal end portion 902a.
  • Distal end portion 902a includes an insulating collar or spacer 916 proximal to active electrode 910, and a return electrode 918 proximal to collar 916.
  • a first insulating sleeve (Fig. 14) may be located beneath return electrode 918.
  • a second insulating jacket or sleeve 920 may extend proximally from return electrode 918.
  • Second insulating sleeve 920 serves as an electrical insulator to inhibit current flow into the adjacent tissue.
  • probe 900 further includes a shield 922 extending proximally from second insulating sleeve 920.
  • Shield 922 may be formed from a conductive metal such as stainless steel, and the like. Shield 922 functions to decrease the amount of leakage current passing from probe 900 to a patient or a user (e.g., surgeon). In particular, shield 922 decreases the amount of capacitive coupling between return electrode 918 and an introducer needle 928 (Fig. 19A).
  • shield 922 is coupled to an outer floating conductive layer or cable shield (not shown) of a cable, e.g. cables 22, 34 (Fig. 2A), connecting probe 900 to power supply 28. In this way, the capacitor balance of shaft 902 is disturbed.
  • shield 922 may be coated with a durable, hard compound such as titanium nitride. Such a coating has the advantage of providing reduced friction between shield 922 and introducer inner wall 932 as shaft 902 is axially translated within introducer needle 928 (e.g., Figs. 19A, 19B).
  • the electrosurgical probes may have shafts, particularly at their distal portions, which are angled or capable of being angled to access a volume of tissue wider than the cross-sectional dimension ofthe shaft.
  • the shaft may have a pre-defined bias or angle or may be selectively biased or angled by means as described above.
  • the electrosurgical probe 900 of Figs. 11 and 12 has an angled distal portion having at least two bends or curves 924, 926 to provide a pre-defined S-curve configuration.
  • Electrosurgical probe 900 has a first curve 924 and a second curve 926 located at distal end portion 902a, wherein second curve 926 is proximal to first curve 924.
  • First curve 924 and second curve 926 may be separated by a linear (i.e. straight, or non- curved), or substantially linear, inter-curve portion 925 of shaft 902.
  • shaft distal end portion 902a includes a linear or substantially linear proximal portion 901 extending from proximal end portion 902b to second curve 926, a linear or substantially linear inter-curve portion 925 between first and second curves 924, 926, and a linear or substantially linear distal portion 909 between first curve 924 and the distal tip of shaft 902 (the distal tip is represented in Fig. 12A as an electrode head 911).
  • first curve 924 subtends a first angle V to the inner surface of needle 928
  • second curve 926 subtends a second angle 3 to inner surface 932 of needle 928.
  • needle inner surface 932 is essentially parallel to the longitudinal axis of shaft proximal end portion 902b (Fig. 11).)
  • shaft distal end portion 902a is designed such that the shaft distal tip occupies a substantially central transverse location within the lumen of introducer needle 928 when shaft distal end portion 902a is translated axially with respect to introducer needle 928. Thus, as shaft distal end portion 902a is advanced through the distal opening of needle 928 (Figs.
  • shaft distal end portion 902a is flexible and has a configuration which requires shaft distal end portion 902a be distorted in the region of at least second curve 926 by application of a lateral force imposed by inner wall 932 of introducer needle 928 as shaft distal end portion 902a is introduced or retracted into needle 928.
  • first curve 924 and second curve 926 are in the same plane relative to the longitudinal axis of shaft 902, and first and second curves 924, 926 are in opposite directions.
  • the "S-curve" design of shaft distal end portion 902a allows the distal tip (e.g., electrode head 911) to be advanced and retracted through the distal opening of needle 928 while avoiding contact between the distal tip and the edges ofthe distal opening of needle 928.
  • the length L2 of distal portion 909 and the angle V between distal portion 909 and needle inner surface 932 928, when shaft distal end portion 902a is compressed within needle 928 are selected such that the distal tip is substantially in the center ofthe lumen of needle 928, as shown in Fig. 12 A.
  • the angle V will decrease, and vice versa.
  • first and second curves, 924, 926 provides a pre-defined bias in shaft 902.
  • shaft distal end portion 902a is designed such that at least one of first and second curves 924, 926 are compressed to some extent as shaft distal end portion 902a is retracted into the lumen of needle 928.
  • the angle of at least one of curves 924, 926 may be changed when distal end portion 902a is advanced out through the distal opening of introducer needle 928, as compared with the corresponding angle when shaft distal end portion is completely retracted within introducer needle 928.
  • Fig. 12B shows shaft 902 of Fig. 12A free from introducer needle 928, wherein first and second curves 924, 926 are allowed to adopt their natural or uncompressed angles V and 3', respectively, wherein 3' is typically equal to or greater than 3.
  • Angle V may be greater than, equal to, or less than angle V.
  • Angle 3' is subtended by inter-curve portion 925 and proximal portion 901.
  • proximal portion 901 approximates the longitudinal axis of shaft 902.
  • Angle V is subtended between linear distal portion 909 and a line drawn parallel to proximal portion 901.
  • Electrode head 911 is omitted from Fig. 12B for the sake of clarity.
  • the principle described above with reference to shaft 902 and introducer needle 928 may equally apply to a range of other medical devices. That is to say, the "S-curve" configuration ofthe invention may be included as a feature of any medical system or apparatus in which a medical instrument may be axially translated or passed within an introducer device.
  • the principle ofthe "S-curve" configuration ofthe invention may be applied to any apparatus wherein it is desired that the distal end ofthe medical instmment does not contact or impinge upon the introducer device as the medical instrument is advanced from or retracted into the introducer device.
  • the introducer device may be any apparatus through which a medical instrument is passed.
  • Such medical systems may include, for example, a catheter, a cannula, an endoscope, and the like.
  • the S-curve design allows a sensitive or delicate component, such as an electrode, to be located at the distal tip of a device, wherein the distal end or tip is advanced or retracted through a lumen of an introducer instrument comprising a relatively hard material (e.g., an introducer needle comprising stainless steel).
  • a relatively hard material e.g., an introducer needle comprising stainless steel.
  • This design also allows a component located at a distal end or tip of a device to be constructed from a relatively soft material, and for the component located at the distal end or tip to be passed through an introducer instrument comprising a hard material without risking damage to the component comprising a relatively soft material.
  • shaft distal tip When shaft 902 is advanced distally through the needle lumen to a point where second curve 926 is located distal to needle distal end 928a, the shaft distal tip is deflected from the longitudinal axis of needle 928.
  • the amount of this deflection is determined by the relative size of angles 3' and V, and the relative lengths of LI and L2.
  • the amount of this deflection will in turn determine the size of a channel or lesion (depending on the application) formed in a tissue treated by electrode head 911 when shaft 902 is rotated circumferentially with respect to the longitudinal axis of probe 900.
  • shaft distal end portion 902a will contact a larger volume of tissue than a linear shaft having the same dimensions.
  • the pre-defined bias of shaft 902 allows the physician to guide or steer the distal tip of shaft 902 by a combination of axial movement of needle distal end 928a and the inherent curvature at shaft distal end portion 902a of probe 900.
  • Shaft 902 preferably has a length in the range of from about 4 to 30 cm.
  • probe 900 is manufactured in a range of sizes having different lengths and/or diameters of shaft 902. A shaft of appropriate size can then be selected by the surgeon according to the body structure or tissue to be treated and the age or size ofthe patient. In this way, patients varying in size from small children to large adults can be accommodated.
  • a shaft of appropriate size can be selected by the surgeon depending on the organ or tissue to be treated, for example, whether an intervertebral disc to be treated is in the lumbar spine or the cervical spine.
  • a shaft suitable for treatment of a disc of the cervical spine may be substantially smaller than a shaft for treatment of a lumbar disc.
  • shaft 902 is preferably in the range of from about 15 to 25 cm.
  • shaft 902 is preferably in the range of from about 4 to about 15 cm.
  • the diameter of shaft 902 is preferably in the range of from about 0.5 to about 2.5 mm, and more preferably from about 1 to 1.5 mm.
  • First curve 924 is characterized by a length LI
  • second curve 926 is characterized by a length L2 (Fig. 12 A).
  • Inter-curve portion 925 is characterized by a length L3, while shaft 902 extends distally from first curve 924 a length L4.
  • L2 is greater than LI .
  • Length LI may be in the range of from about 0.5 to about 5 mm
  • L2 may be in the range of from about 1 to about 10 mm.
  • L3 and L4 are each in the range of from about 1 to 6 mm.
  • Fig. 13 is a side view of shaft distal end portion 902a of electrosurgical probe 900 showing a head 911 of active electrode 910 (the latter not shown in Fig.
  • electrode head 911 includes an apical spike 911a and an equatorial cusp 911b. Electrode head 911 exhibits a number of advantages as compared with, for example, an electrosurgical probe having a blunt, globular, or substantially spherical active electrode. In particular, electrode head 911 provides a high current density at apical spike 911a and cusp 911b. In turn, high current density in the vicinity of an active electrode is advantageous in the generation of a plasma; and, as is described fully hereinabove, generation of a plasma in the vicinity of an active electrode is fundamental to ablation of tissue with minimal collateral thermal damage according to certain embodiments ofthe instant invention.
  • Electrode head 911 provides an additional advantage, in that the sharp edges of cusp 91 lb, and more particularly of apical spike 911a, facilitate movement and guiding of head 911 into tissue during surgical procedures, as described fully herein below.
  • an electrosurgical probe having a blunt or rounded apical electrode is more likely to follow a path of least resistance, such as a channel which was previously ablated within nucleus pulposus tissue.
  • FIG. 14 is a longitudinal cross-sectional view of distal end portion 902a of shaft 902.
  • Apical electrode head 911 is in communication with a filament 912.
  • Filament 912 typically comprises an electrically conductive wire encased within a first insulating sleeve 914.
  • First insulating sleeve 914 comprises an insulator, such as various synthetic polymeric materials.
  • An exemplary material from which first insulating sleeve 914 may be constructed is a polyimide.
  • First insulating sleeve 914 may extend the entire length of shaft 902 proximal to head 911.
  • An insulating collar or spacer 916 is disposed on the distal end of first insulating sleeve 914, adj acent to electrode head 911.
  • Collar 916 preferably comprises a material such as a glass, a ceramic, or silicone.
  • first insulating sleeve 914 (i.e., the portion proximal to collar 916) is encased within a cylindrical return electrode 918.
  • Return electrode 918 may extend proximally the entire length of shaft 902.
  • Return electrode 918 may comprise an electrically conductive material such as stainless steel, tungsten, platinum or its alloys, titanium or its alloys, molybdenum or its alloys, nickel or its alloys, and the like.
  • a proximal portion of return electrode 918 is encased within a second insulating sleeve 920, so as to provide an exposed band of return electrode 918 located distal to second sleeve 920 and proximal to collar 916.
  • Second sleeve 920 provides an insulated portion of shaft 920 which facilitates handling of probe 900 by the surgeon during a surgical procedure.
  • a proximal portion of second sleeve 920 is encased within an electrically conductive shield 922.
  • Second sleeve 920 and shield 922 may also extend proximally for the entire length of shaft 902.
  • Fig. 15 is a side view of shaft distal end portion 902a of electrosurgical probe 900, indicating the position of first and second curves 924, 926, respectively.
  • Probe 900 includes head 911, collar 916, return electrode 918, second insulating sleeve 920, and shield 922, generally as described with reference to Figs. 13, 14. In the embodiment of Fig.
  • first curve 924 is located within return electrode 918, while second curve 926 is located within shield 922.
  • shaft 902 may be provided in which one or more curves are present at alternative or additional locations or components of shaft 902, other than the location of first and second curves 924, 926, respectively, shown in Fig. 15.
  • Fig. 16A shows distal end portion 902a of shaft 902 extended distally from an introducer needle 928, according to one embodiment ofthe invention.
  • Introducer needle 928 may be used to conveniently introduce shaft 902 into tissue, such as the nucleus pulposus of an intervertebral disc.
  • FIGs. 17A-D show another electrosurgical probe 1200 that may be useful in performing a spinal surgery as well as other types of surgery.
  • the probe shown in Figs. 17A-17D is intended for minimally invasive surgeries that may require relatively large volumes or cavities to be formed in a bone body where access to the target site is limited, such as removal of a bone tumor in a vertebral body.
  • the probe 1200 comprises a proximal end 1210 that is adapted to connect with a cable, an elongate shaft 1220, and a curved distal end 1230.
  • the overall length ofthe probe may vary depending on the application.
  • An exemplary length for the shaft 1220 in a spinal surgery procedure may be about 8-9 inches not including the proximal end connector 1210.
  • the probe diameter may range from 1 to 5 mm and, in one variation, ranges from 2 to 2.5 mm.
  • Fig. 17B shows an enlarged view ofthe distal end section of probe 1200 of Fig. 17 A.
  • Distal end section 1230 includes a first bend 1232 and a second bend 1234 fonning an "s- curve" similar to that described in the above mentioned probes.
  • This type of bend tends to prevent the active electrodes 1240a-c on the distal tip from contacting an introducer needle (not shown) when the active electrodes exit the introducer needle and enter the target tissue.
  • an introducer needle not shown
  • the s-curve tends to prevent the active electrode from contacting the introducer needle.
  • Contact between the introducer needle and the active electrodes can have detrimental effects on the ablation energy and is thus undesirable.
  • the curved or bent configuration ofthe distal end section 1230 of probe 1200 also allows the electrode tip 1240 to be pointed laterally of or at an angle to the longitudinal axis defined by the introducer needle. Rotation ofthe probe within the needle introducer allows positioning ofthe electrode tip at multiple trajectories.
  • the radius ofthe area or volume which can be ablated is increased.
  • This angle may vary depending on the size ofthe access area and ofthe targeted area to be ablated. Exemplary angles range from about 5 to about 30 degrees, and more typically from about 8-10 degrees or about 9 degrees.
  • the probe shown in Fig. 17A includes a particular bend, the invention is not intended to be so limited unless specifically recited so in the appended claims. Indeed, the probe may have no bend or other types of bends and curvatures.
  • probe 1200 may be bendable or malleable such that the curve configuration may be customized by the physician at the time of surgery in order to most effectively access and target the area to be ablated.
  • Malleable metals, alloys, and plastics as is known to those of skill in the relevant art may be used for the probe.
  • probe 1200 includes wire conductors 1238a-c which collectively form a wire bundle where each conductor provides an electrode 1240 at its distal end, which collectively provide a bouquet arrangement or configuration.
  • the multiple active electrodes 1240a-c allow for more aggressive ablation.
  • the active electrodes may be shaped variously, including an equatorial cusp or an apical tip as shown in Fig.
  • each wire conductor 1238a-c and associated electrode 1240a-c ofthe bouquet may be biased radially outward from the other electrodes.
  • the active electrodes thus spread or expand radially outward to a degree when not confined by another member such as an introducer needle.
  • the electrodes may be made of a shaped memory material, e.g., Nitinol, which are caused to change configurations or shapes upon exposure to an activating temperature.
  • conductor wires 1238-a-c may have very straight original configurations in order to minimize the necessary space for delivery of the electrodes 1240a-c through an access channel.
  • this self-expandable electrode arrangement allows a cavity to be formed which is at least as large as the inner diameter ofthe introducer needle, and may be larger, typically about 2 to 5 times larger than the im er diameter ofthe introducer and thereby able to remove more tissue. Furthermore, this feature minimizes the need for a predefined angled or bent distal shaft portion, and thus allows for a smaller- diameter probe and introducer.
  • Each ofthe plurality of active electrodes is connected to a wire conductor that extends through the shaft (as shown in the partial cross-section of a distal section ofthe probe 1200 in Fig. 17C).
  • the wire conductors collectively form a wire bundle and are joined to a cable (not shown) that connects the probe to an electrical source.
  • Each ofthe wire conductors may be covered with a thin polymeric coating such as polyimide.
  • An inner tubular non-electrically conducting member or spacer 1254 is coaxially arranged on the exterior ofthe wire bundle to provide an electrical gap between the active electrodes 1240a-c and the return electrode 1250.
  • Suitable materials for the tubular member include, for example, ceramic, e.g., alumina, silicone polymers and other polyesters or polyolefins or copolymers, e.g., ethylene tetrafluoroethylene (ETFE).
  • the tubular member may extend a distance from the distal edge ofthe return electrode 1250. Distance di may range from 0.25 to 2 mm and more preferably from 0.75 to 1.25 mm and perhaps about 1 mm. Also, the electrode heads may be spaced a distance (d 2 ) from the distal edge ofthe tubular member. Distance d 2 may range from 0.25 to 2.5 mm and may be about 0.5 mm in one variation ofthe invention.
  • a securing member 1252 is arranged over the exterior ofthe tubular member to control the amount radial expansion by the active electrodes.
  • a securing member may be a metal wire or coil that is helically wrapped around the wire bundle, or a metal ring.
  • the metal wire or ring may be stainless steel, titanium, molybdenum, etc., and may also have a polymeric coating such as polyimide or ETFE.
  • the thickness ofthe coating may vary and may be as small as about 15 microns and are more typically about 25 microns but may have other thicknesses.
  • a redundant member 1256 may be arranged over the helically wrapped wire member 1252 to further provide mechanical integrity to the probe.
  • the redundant member 1256 may be, for example, heat shrink-wrap tube and it may extend coaxially to cover the whole length of the inner silicone tube.
  • An adhesive 1258 such as UV adhesive or a silicone adhesive may be added to bond all the components or layers together.
  • the combined structure holds the active electrodes in tension while having a strong dielectric strength and providing some elasticity and compliance to allow for radially expansion ofthe active electrodes when not radially confined by the lumen ofthe introducer needle.
  • the active electrodes may be further pushed radially apart from each other during blunt dissection of tissue.
  • the elasticity and compliance characteristics ofthe tubular member, securing member and redundant member may be selected to achieve the desired electrode expansion parameters.
  • the probe 1200 also includes a return electrode 1250 arranged proximal to the active electrodes on the shaft.
  • the return electrode is coated with a polymeric coating 1251 proximally and includes a length of exposed metal ranging from 0.5 to 10 mm and perhaps about 5 to 7 mm.
  • a voltage difference is applied between the active electrodes and the return electrode to ablate tissue during an application.
  • an electrolytically conductive fluid is delivered in the target area and contacts the return and active electrodes. As described above, the electrolytically conductive fluid is vaporized and a plasma is formed when a proper voltage differential is applied between the electrodes. The plasma-mediated ablation removes tissue quickly.
  • a multiple active electrode configuration such as that of Figs.
  • one or more ofthe electrodes may be employed with one or more suction lumens in the instrument coupled to a suitable vacuum source to aspirate any non-ablated tissue fragments, the electrically conductive fluid, or other fluids at the target site, such as bone marrow, blood, mucus, and/or the non-condensable gaseous products of ablation.
  • the aspiration electrode(s) function mainly to inhibit clogging ofthe lumen that may otherwise occur as larger tissue fragments are drawn therein.
  • One or more active electrodes may alternatively or additionally serve as irrigation electrodes in fluid communication with a source of saline.
  • Fig. 33 illustrates another variation of an electrosurgical probe which may be configured to be self-extending or manually articulated to an extended position upon exiting the access cannula or needle.
  • Probe 1500 has a shaft 1510 having a hinged distal portion 1520.
  • distal portion 1520 In an un-extended condition distal portion 1520 is aligned coaxially with the axis of the remainder of shaft 1510, allowing the probe to pass linearly though the access channel.
  • distal portion 1520 rotates away from the shaft axis by means of one or more hinges 1522 and is positioned at an angle ⁇ with shaft 1510.
  • Angle ⁇ may vary and may range from 35-70 and 45-55 degrees. Rotation ofthe probe about the shaft's axis while applying a voltage across the active electrodes 1530 and return electrode 1532 results in the creation of three-dimensional cavity.
  • distal portion 1520 may be naturally biased or spring-loaded to open or extend to a desired angle with respect to the shaft. With manually controlled embodiments, the articulation or rotation of distal portion 1520 is controlled by the physician through pull-wires or rods and other means previously mentioned herein.
  • the present invention provides other variations of electrosurgical probes utilizing different modalities of increasing the accessible area and volume of tissue to be removed.
  • the probes may provide electrodes positioned or mounted on a structure which is movable or expandable from a low profile state or configuration (during delivery through the access channel) to a higher profile state or configuration (upon exiting the access channel) to remove tissue.
  • the expansion ofthe expandable structure may be accomplished passively, such as by a self-expanding mechanism, e.g., by spring loading, or temperature activation, or actively, such as by balloon inflation or mechanical actuation, e.g., by the application of linear or rotational forces.
  • Fig. 28 there is illustrated a distal portion of an electrosurgical probe
  • Probe 1400 having an expandable or inflatable structure, such as balloon or bladder 1408, for supporting electrodes (not shown).
  • Probe 1400 further includes an outer shaft 1402 and an inner shaft 1404 positioned within and translatable tlirough outer shaft 1402.
  • Balloon inflation lumen 1406 is positioned outside inner shaft 1404 and within outer shaft 1402.
  • Inner shaft 1404 includes a lumen for delivering a conductive fluid for creating the Coblation effect as described above.
  • Outer shaft 1402 may include an auxiliary suction lumen (not shown) for aspirating tissue, fluids and/or gases from the target site.
  • the inflation lumen 1406 has one or more inflation and/or deflation ports or apertures to selectively inflate and deflate balloon 1408 with the supply and removal of an inflation media, such as saline.
  • the inflation media may include a radiopaque contrast agent so that the balloon location and degree of inflation can be monitored by fluoroscopy.
  • Balloon 1408 may be made of a material that is distensible, compliant, semi compliant or non compliant, so as to be selectively inflatable to a desired diameter depending on the size ofthe target tissue area to be removed.
  • the diameter of balloon 1408 when fully inflated is typically not greater than about 13 mm.
  • the shape and height of balloon 1408 may also be selected based on the size ofthe target tissue area to be removed.
  • Probe 1400 further includes at least one electrode mounted on or supported by balloon 1408.
  • the one or more electrodes which overlie and may be substantially flush with the outer surface ofthe balloon, may be provided in any suitable arrangement (see Figs. 29 and 30).
  • the metal is preferably mounted on plastic insulation such that it may flex. The metal may stretch or bend from one configuration to another. Additionally, the electrodes may be shaped in a zig-zag arrangement that lengthens as the balloon is expanded.
  • the electrode lines may be bonded to an insulation material at selected points along the electrode line. This configuration allows for some electrode movement such that balloon may be expanded and contracted while keeping the electrodes intact. At least the active electrode(s) is positioned about the balloon; however, the return electrode(s) may also be positioned on the balloon. Alternatively, the return electrode may be positioned proximally ofthe balloon, such as on shaft 1402.
  • Figs. 29 and 30 illustrate exemplary balloon electrode arrangements for use with probe 1400 of Fig 28.
  • the electrode-balloon assemblies 1410 and 1420 include at least one active electrode 1412 and at least one return electrode 1414.
  • Each electrode 1412, 1414 includes a central, primary or apical portion 1412a, 1414a and at least one secondary or lateral portion 1412b, 1414b extending from the respective primary portion.
  • primary electrode portions 1412a, 1414a are positioned at the distal and proximal apexes, respectively, of balloons 1418, where primary return electrode portion 1414a is positioned proximally of primary active electrode portion 1412a.
  • At least one or a plurality of secondary portions 1412b, 1414b ofthe electrodes extend from their respective primary portions over the lateral surface(s) (i.e., lateral with respect to the longitudinal axis of the probe shaft) of balloon 1418, providing an electrode array.
  • the electrode-balloon assemblies 1410 and 1420 differ from each other in the relative configurations of their respective secondary electrode portions 1412b, 1414b as well as in the directional placement ofthe secondary electrode portions 1412b, 1414b vis-a-vis the longitudinal axis 1416 of the probe 1400.
  • Each ofthe electrodes ofthe electrode assembly of Fig. 29 includes a single secondary electrode portion 1412b, 1414b wliich wraps helically about the circumference of balloon 1418 such that portions 1412b, 1414b are positioned substantially transverse to longitudinal axis 1416 (i.e., horizontally with respect to the view of Fig. 29).
  • FIG. 30 includes a plurality of secondary electrode portions or fingers 1412b, 1414b extending linearly or radially from the respective primary portion 1412a, 1414a such that they extend substantially parallel to longitudinal axis 1416 (i.e., vertically with respect to the view of Fig. 30). While the electrode assembly of Fig. 30 has been described in the context of a single active electrode having a plurality of portions and a single return electrode having a plurality of portions, it is understood that a plurality of active and/or return electrodes may be used instead. Another characteristic ofthe illustrated electrode assemblies is that the secondary portions 1412b ofthe active electrode and the secondary portions 1414b ofthe return electrode are parallel to and interspaced or interdigitated with each other.
  • the active electrode portions alternate with the return electrode portions.
  • the electrode portions are evenly spaced from each other and are at least about 2-5 mm apart.
  • a spherical shape may be used.
  • current is supplied to the active and return balloon electrodes ofthe probe of Fig. 28 by conductors which may be positioned along the length of inflation lumen or the inner and outer shafts ofthe probe.
  • an active electrode on the balloon is electrically coupled to a controller with a conductor wire that extends along or is embedded within the wall of inflation lumen 1406.
  • Return electrode 1414 may likewise be in electrical communication with a controller via a conductor wire that extends along inner shaft and covered by an insulating coating.
  • the balloon 1408 Upon positioning ofthe distal end ofthe probe adjacent the tissue to be removed, the balloon 1408 is selectively inflated and the requisite voltage is applied as described previously.
  • the interdigitating pattern ofthe balloon-electrode assemblies create a plurality of high electric field intensities upon application of voltage.
  • the balloon is inflated and its diameter increased incrementally or continuously thereby radially increasing the size ofthe cavity formed by removal ofthe target tissue. The process is continued until the desired area or volume of target tissue is removed.
  • the application of voltage may be done simultaneously or alternatingly with the inflation of balloon 1408, and either or both may be done continuously or alternatingly until the desired area of target tissue is removed.
  • tissue is ablated prior to or concurrently with expansion ofthe balloon.
  • the ablation process removes the tissue and the expansion ofthe balloon provides for a greater sweep or area of target tissue. This is in contrast to systems that use a balloon to mechanically enlarge a cavity within the vertebral body by displacing tissue.
  • the temperature at or near the balloon surface typically ranges from about 40° to about 70° C, which is insufficient to damage the balloon material.
  • FIG. 31 A and 3 IB there is illustrated another probe 1430 utilizing an expandable mechanical structure 1432 for supporting and advancing the electrodes into the target tissue to be removed.
  • Structure 1432 includes parallel, spaced apart struts 1434 which define a hollow cage-like structure.
  • the struts may be configured to provide any suitable shape to the structure including, but not limited to, spherical, elliptical or diamond shaped.
  • the outer or external surfaces ofthe struts support primary or central portions 1436a ofthe active electrode at the distal apex ofthe structure and support primary or central portions 1438a ofthe return electrode at the proximal apex ofthe structure. Similar to the balloon embodiment of Fig.
  • the active and return electrodes each include a plurality of secondary electrode portions 1436b, 1438b extending linearly or radially from the respective primary portion 1436a, 1438a, providing an electrode array.
  • Each secondary portion overlies the outer surface of a strut 1434.
  • the secondary portions are arranged such that secondary portions 1436b ofthe active electrode interdigitate with each ofthe secondary portions 1438b ofthe return electrode.
  • the active and return electrode portions may be mounted on opposite sides ofthe same strut, i.e., the secondary portions 1436b ofthe active electrode may be positioned on the outer surfaces ofthe struts while the secondary portions 1438b of the return electrode are positioned on the internal or undersurfaces ofthe struts, as illustrated Fig. 31C.
  • a distal end of tubular shaft 1440 is affixed to structure 1432 at central portion 1438a ofthe return electrode.
  • a rod or insulated wire 1442 is positioned and translatable within the lumen of shaft 1440 and extends distally ofthe tubular shaft 1440 to within structure 1432.
  • the distal end of wire 1442 is affixed to the underside of central portion 1436a ofthe active electrode.
  • Structure 1432 is made of a flexible material. A metal, alloy, stainless steel, mesh, or braided material may also be used. As such, moving or pushing rod 1442 in a distal direction while holding shaft 1442 stable stretches structure 1432 lengthwise along the longitudinal axis ofthe rod.
  • struts 1434 When rod 1442 is in a fully extended position, the struts 1434 are aligned and flush with the rod. This low profile state facilitates delivery through the access channel to the target site.
  • Moving or pulling rod 1442 in a proximal direction (indicated by arrow 1435a) compresses structure 1432 along the longitudinal axis of rod 1442 whereby the apex-to-apex distance of structure 1432 is foreshortened or reduced and the width or lateral distance of structure 1432 is increased (indicated by arrows 1435b and 1435c), i.e., struts 1434 are caused to flex or bend outwardly.
  • the extent of axial compression of structure 1432 can be controlled by selectively pushing and pulling rod 1442.
  • structure 1432 may be gradually expanded so as to reach the perimeter ofthe target tissue.
  • the pushing of wire 1442 in a distal direction extends or lengthens structure 1432 along the longitudinal axis of wire 1442 and causes struts 1434 to flex or bend inwardly whereby the apex-to-apex distance of structure 1432 is lengthened or increased and the width or lateral distance of structure 1432 is reduced.
  • the flexible struts may be made of a material having a preformed expanded or high profile configuration whereby the struts may be held in a compressed or un-expanded or low profile configuration and released to expand to the expanded configuration.
  • the struts may be self-expanding upon release or may expand to the high profile configuration upon exposure to particular temperature, e.g., body temperature, or under compression by pulling of wire 1442.
  • Active electrode 1436a may be in electrical communication with a conductor wire (not shown) extending along rod 1442 and return electrode 1438a is in electrical communication with a conductor wire (not shown) extending along or embedded within the wall of tubular shaft 1440.
  • the extent of compression expansion of structure 1432 is dictated by its size and may be controlled by a user to allow selective, three-dimensional ablation and removal of tissue or bone.
  • the mechanical structure or cage is extended and its diameter or length is increased incrementally or continuously thereby radially increasing the size of the cavity formed upon application of a voltage to the electrodes.
  • the application of voltage may be done simultaneously or alternatingly with the expansion of structure 1432, and either or both may be done continuously until the desired area of target tissue is removed.
  • Structure 1432 may optionally be provided with radiopaque markers in order to view the various steps ofthe procedure, and particularly the movement ofthe structure
  • Other variations ofthe probes ofthe present invention in which the relative position ofthe electrodes, particularly the lateral displacement ofthe electrodes from a first configuration to a second configuration, do not require the use of an independent expandable or extendable structure to which the electrodes are mounted.
  • FIG. 32 there is illustrated another electrosurgical probe 1450 having active and return electrodes 1452, 1460 in the form of coils or spirally or helically wrapped wires.
  • One end 1460a of return electrode 1460 is affixed to the distal end of tubular shaft 1454 and is in electrical communication via a conductor (not shown) on or within the wall of shaft 1454.
  • the other end ofthe return electrode is attached to rod 1456.
  • the attachment may be insulated to prevent an electrical connection between return electrode 1460 and rod 1456.
  • the active electrode is attached at one end 1452a to the distal end of rod 1456 and is in electrical communication via a conductor (not shown) running along rod 1456.
  • the active electrode is attached at the other end to the shaft 1454. However, the attachment may be insulated to prevent an electrical connection between the components.
  • the coil turns or secondary portions 1452b and 1460b ofthe active and return electrodes, respectively, run parallel to each other and are also interdigitated along their entire lengths.
  • Rod 1456 is positioned within and rotatably movable within shaft 1454 whereby the axial rotation of rod 1456 in one direction, designated by arrow 1458b, causes a tightening or winding ofthe active and return electrodes and the axial rotation of rod 1456 in the opposite direction, designated by arrow 1458a, results in a loosening or unwinding unwrapping ofthe active and return electrodes.
  • Figure 32' shows a top view ofthe connection between the active electrode coil 1452b, rod 1456, return electrode coil 1460b, and support 1452a.
  • the active electrode and rod may be electrically connected via a wire element or other means.
  • the whole support 1452a may be electrically conductive and the return electrode end may be insulated to prevent a short in the circuit.
  • the embodiment illustrated in figure 32 thus provides another controllably expandable electrode structure to ablate tissues, form cavities and lumens. While specific electrode arrangements have been illustrated with the various expandable or extendable electrode structures, any other suitable arrangement, spacing, relative positioning and number of electrodes may be employed with the subject probes. Additionally, while only symmetrically shaped expandable members or structures (e.g., balloons, cages, etc.) have been illustrated and discussed, asymmetrically shaped structures may be employed to accommodate oddly or asymmetrically shaped target sites or where the target site or tumor to be removed abuts the vertebral wall on one side.
  • asymmetrically shaped structures may be employed to accommodate oddly or asymmetrically shaped target sites or where the target site or tumor to be removed abuts the vertebral wall on one side.
  • a non-distensible or non-compliant material having a preformed, customized asymmetrical shape may be used for the specific application at hand.
  • Figs. 18A-18B show an electrosurgical assembly or kit 1300 including an introducer needle 1310, a fluid connector 1320, and an electrosurgical probe 1330 as described above in connection with Figs. 17A-C.
  • the kit assembly may be used in a number of procedures such as the procedures described above in connection with Figs. 1 A-1H.
  • Fig. 18A shows an exploded view illustrating how the components are interconnected.
  • the probe 1330 is inserted through connector 1320 and through needle 1310.
  • the needle may be rigid and have a length suitable for the type of procedure.
  • the connector has an egress end 1322 that is configured to fluidly connect with a proximal end ofthe introducer needle.
  • connector and introducer needle may have Luer- type threads 1326.
  • the connector further includes an ingress port 1324 for accepting fluid from a fluid source.
  • a flexible tube 1340 may fluidly connect the fluid connector to a stopcock 1342 that is configured to receive fluid from the fluid source.
  • a wide variety of fluid connector assemblies may be employed to supply liquid to the introducer needle.
  • the introducer needle 1310 directs fluid to the target region where the active electrodes ofthe probe are positioned. In this manner, the active electrodes may operate in the presence of electrically conductive fluid.
  • the probe tip may be urged distally and proximally relative to the introducer needle.
  • FIG. 19A shows a side view of shaft 902 in relation to an inner wall 932 of introducer needle 928 upon extension or retraction of electrode head 911 from, or within, introducer needle 928.
  • Shaft 902 is located within introducer 928 with head 911 adjacent to introducer distal end 928a (Fig. 19B).
  • curvature of shaft 902 may cause shaft distal end 902a to be forced into contact with introducer inner wall 932, e.g., at a location of second curve 926.
  • first curve 924 Figs.
  • FIG. 11-B head 911 does not contact introducer distal end 928a.
  • Fig. 19B shows an end view of electrode head 911 in relation to introducer needle 928 at a point during extension or retraction of shaft 902, wherein head 911 is adjacent to introducer distal end 928a (Figs. 16B, 19B). In this situation, head 911 is substantially centrally positioned within lumen 930 of introducer 928. Therefore, contact between head 911 and introducer 928 is avoided, allowing shaft distal end 902a to be extended and retracted repeatedly without sustaining any damage to shaft 902. Fig.
  • shaft proximal end portion 902b of electrosurgical probe 900 shows shaft proximal end portion 902b of electrosurgical probe 900, wherein shaft 902 includes a plurality of depth markings 903 (shown as 903 a-f in Fig. 20).
  • depth markings 903 may be included on shaft 902.
  • depth markings may be present along the entire length of shield 922, or a single depth marking 903 may be present at shaft proximal end portion 902b.
  • Depth markings serve to indicate to the surgeon the depth of penetration of shaft 902 into a patient's tissue, organ, or body, during a surgical procedure.
  • Depth markings 903 may be formed directly in or on shield 922, and may comprise the same material as shield 922.
  • depth markings 903 may be formed from a material other than that of shield 922.
  • depth markings may be formed from materials which have a different color and/or a different level of radiopacity, as compared with material of shield 922.
  • depth markings may comprise a metal, such as tungsten, gold, or platinum oxide (black), having a level of radiopacity different from that of shield 922.
  • Such depth markings may be visualized by the surgeon during a procedure performed under fluoroscopy.
  • the length ofthe introducer needle and the shaft 902 are selected to limit the range ofthe shaft beyond the distal tip ofthe introducer needle.
  • Fig. 21 shows a probe 900, wherein shaft 902 includes a mechanical stop 905.
  • mechanical stop 905 is located at shaft proximal end portion 902b.
  • Mechanical stop 905 limits the distance to which shaft distal end 902a can be advanced through introducer 928 by making mechanical contact with a proximal end 928b of introducer 928.
  • Mechanical stop 905 may be a rigid material or structure affixed to, or integral with, shaft ' 902. Mechanical stop 905 also serves to monitor the depth or distance of advancement of shaft distal end 902a through introducer 928, and the degree of penetration of distal end 902a into a patient's tissue, organ, or body.
  • mechanical stop 905 is movable on shaft 902, and stop 905 includes a stop adjustment unit 907 for adjusting the position of stop 905 and for locking stop 905 at a selected location on shaft 902.
  • Fig. 22 illustrates stages in manufacture of an active electrode 910 of a shaft 902, according to one embodiment ofthe present invention.
  • Stage 22-1 shows an elongated piece of electrically conductive material 912', e.g., a metal wire, as is well known in the art.
  • Material 912' includes a first end 912'a and a second end 912'b.
  • Stage 22-11 shows the formation of a globular structure 911' from first end 912'a, wherein globular structure 911' is attached to filament 912.
  • Globular structure 911' may be conveniently formed by applying heat to first end 912'a. Techniques for applying heat to the end of a metal wire are well known in the art.
  • Stage 22-111 shows the formation of an electrode head 911 from globular structure 911', wherein active electrode 910 comprises head 91 1 and filament 912 attached to head 911.
  • head 911 includes an apical spike 911a and a substantially equatorial cusp 911b.
  • Fig. 23 schematically represents a series of steps involved in a method of making a shaft according to one embodiment ofthe present invention, wherein step 1000 involves providing an active electrode having a filament, the active electrode including an electrode head attached to the filament.
  • An exemplary active electrode to be provided in step 1000 is an electrode ofthe type described with reference to Fig. 22.
  • the filament may be trimmed to an appropriate length for subsequent coupling to a connection block (Fig. 9).
  • Step 1002 involves covering or encasing the filament with a first insulating sleeve of an electrically insulating material such as a synthetic polymer or plastic, e.g., a polyimide.
  • the first insulating sleeve extends the entire length ofthe shaft.
  • Step 1004 involves positioning a collar of an electrically insulating material on the distal end ofthe first insulating sleeve, wherein the collar is located adjacent to the electrode head.
  • the collar is preferably a material such as a glass, a ceramic, or silicone.
  • Step 1006 involves placing a cylindrical return electrode over the first insulating sleeve.
  • the return electrode is positioned such that its distal end is contiguous with the proximal end ofthe collar, and the return electrode preferably extends proximally for the entire length ofthe shaft.
  • the return electrode may be constructed from stainless steel or other non-corrosive, electrically conductive metal.
  • a metal cylindrical return electrode is pre-bent to include a curve within its distal region (i.e., the return electrode component is bent prior to assembly onto the shaft).
  • Step 1008 involves covering a portion ofthe return electrode with a second insulating layer or sleeve such that a band ofthe return electrode is exposed distal to the distal end ofthe second insulating sleeve.
  • the second insulating sleeve comprises a heat-shrink plastic material which is heated prior to positioning the second insulating sleeve over the return electrode.
  • the second insulating sleeve is initially placed over the entire length ofthe shaft, and thereafter the distal end ofthe second insulating sleeve is cut back to expose an appropriate length ofthe return electrode.
  • Step 1010 involves encasing a proximal portion ofthe second insulating sleeve within a shield of electrically conductive material, such as a cylinder of stainless steel or other metal, as previously described herein.
  • Fig. 24 schematically represents a series of steps involved in a method of making an electrosurgical probe ofthe present invention, wherein step 1100 involves providing a shaft having at least one active electrode and at least one return electrode.
  • An exemplary shaft to be provided in step 1100 is that prepared according to the method described hereinabove with reference to Fig.
  • Step 1102 involves bending the shaft to form a second curve.
  • the second curve is located at the distal end portion ofthe shaft, but proximal to the first curve. In one embodiment, the second curve is greater than the first curve.
  • Step 1104 involves providing a handle for the probe.
  • the handle includes a connection block for electrically coupling the electrodes thereto.
  • Step 1106 involves coupling the active and return electrodes ofthe shaft to the connection block.
  • the connection block allows for convenient coupling ofthe electrosurgical probe to a power supply (e.g., power supply 28, Fig. 2A).
  • step 1108 involves affixing the shaft to the handle.
  • Fig. 25 is a side view of an electrosurgical probe 900' including shaft 902" having tracking device 942 located at distal end portion 902"a.
  • Tracking device 942 may serve as a radiopaque marker adapted for guiding distal end portion 902"a within a bone body or disc.
  • Shaft 902" also includes at least one active electrode 910 disposed on the distal end portion 902"a.
  • electrically insulating support member or collar 916 is positioned proximal of active electrode 910 to insulate active electrode 910 from at least one return electrode 918.
  • the return electrode 918 is positioned on the distal end portion ofthe shaft 902" and proximal ofthe active electrode 910. In other embodiments, however, return electrode 918 can be omitted from shaft 902", in which case at least one return electrode may be provided on ancillary device 940, or the return electrode may be positioned on the patient's body, as a dispersive pad (not shown).
  • active electrode 910 is shown in Fig. 25 as comprising a single apical electrode, other numbers, arrangements, and shapes for active electrode 910 are within the scope ofthe invention. For example, active electrode 910 can include a plurality of isolated electrodes in a variety of shapes.
  • Active electrode 910 will usually have a smaller exposed surface area than return electrode 918, such that the current density is much higher at active electrode 910 than at return electrode 918.
  • return electrode 918 has a relatively large, smooth surfaces extending around shaft 902" in order to reduce current densities in the vicinity of return electrode 918, thereby minimizing damage to non-target tissue.
  • bipolar delivery of a high frequency energy is the preferred method of debulking, it should be appreciated that other energy sources (i.e., resistive, or the like) can be used, and the energy can be delivered with other methods (i.e., monopolar, conductive, or the like) to debulk the target tissue.
  • tissue may include, for example, bone tissue, disc tissue, and soft tissue.
  • Probe 950 includes handle 904, shaft distal end 952a, active electrode 910, insulating collar 916, and return electrode 918.
  • shaft distal end 952a can adopt a nonlinear configuration, designated 952'a.
  • the deformable nature of shaft distal end 952'a allows active electrode 910 to be guided to a specific target site within a bone body or disc.
  • the principles ofthe "S-curve" configuration ofthe invention may be applied to any medical system or apparatus in which a medical instrument is passed within an introducer device, wherein it is desired that the distal end ofthe medical instrument does not contact or impinge upon the introducer device as the instrument is advanced from or retracted within the introducer device.
  • the introducer device may be any apparatus through which a medical instrument is passed.
  • a medical system or apparatus may include, for example, a catheter, a cannula, an endoscope, and the like.

Abstract

Procédé servant à traiter un corps osseux et consistant à insérer une sonde possédant au moins une électrode active dans le tissu ciblé et à appliquer une différence de tension entre une électrode active et un électrode de retour afin d'effectuer l'ablation du tissu. Ce procédé est particulièrement approprié pour extraire des tumeurs d'un corps osseux et/ou pour enlever un os spongieux dans un corps osseux. Ce corps osseux peut consister en un corps vertébral. Ce dispositif consiste en des sondes électrochirurgicales permettant à leurs électrodes d'accéder au tissu au niveau de trajectoires dépassant le canal d'accès à travers lequel elles sont administrées au tissu ciblé. L'invention concerne également une trousse contenant une sonde électrochirurgicale, un générateur électrochirurgical, une aiguille d'introduction et un raccord de liquide servant à accoupler l'aiguille d'introduction à une source de liquide, de façon à pouvoir appliquer du liquide au tissu ciblé pendant l'intervention.
PCT/US2005/020774 2004-06-10 2005-06-10 Procede et dispositif electrochirurgicaux servant a extraire un tissu a l'interieur d'un corps osseux WO2005122938A1 (fr)

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