Patent Publication Number: US-9839468-B2

Title: Electrosurgical device with internal digestor electrode

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. application Ser. No. 13/409,762 filed Mar. 1, 2012, which claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/448,289 filed Mar. 2, 2011, the complete disclosure of which is incorporated herein by reference for all purposes. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to methods and apparatus for accessing and treating tissue, and more particularly to apparatus and methods for electrosurgically treating tissue such as laryngeal tissue. 
     BACKGROUND 
     The field of electrosurgery includes a number of loosely related surgical techniques which have in common the application of electrical energy to modify the structure or integrity of patient tissue. Electrosurgical procedures usually operate through the application of very high frequency currents to cut or ablate tissue structures, where the operation can be monopolar or bipolar. Monopolar techniques rely on a separate electrode for the return of current that is placed away from the surgical site on the body of the patient, and where the surgical device defines only a single electrode pole that provides the surgical effect. Bipolar devices comprise two or more electrodes on the same support for the application of current between their surfaces. 
     Electrosurgical procedures and techniques are particularly advantageous because they generally reduce patient bleeding and trauma associated with cutting operations. Additionally, electrosurgical ablation procedures, where tissue surfaces and volume may be reshaped, cannot be duplicated through other treatment modalities. 
     Radiofrequency (RF) energy is used in a wide range of surgical procedures because it provides efficient tissue resection and coagulation and relatively easy access to the target tissues through a portal or cannula. Conventional monopolar high frequency electrosurgical devices typically operate by creating a voltage difference between the active electrode and the target tissue, causing an electrical arc to form across the physical gap between the electrode and tissue. At the point of contact of the electric arcs with tissue, rapid tissue heating occurs due to high current density between the electrode and tissue. This high current density causes cellular fluids to rapidly vaporize into steam, thereby producing a “cutting effect” along the pathway of localized tissue heating. Thus, the tissue is parted along the pathway of evaporated cellular fluid, inducing undesirable collateral tissue damage in regions surrounding the target tissue site. This collateral tissue damage often causes indiscriminate destruction of tissue, resulting in the loss of the proper function of the tissue. In addition, the device does not remove any tissue directly, but rather depends on destroying a zone of tissue and allowing the body to eventually remove the destroyed tissue. 
     Present electrosurgical devices used for tissue ablation in narrow anatomies may suffer from concerns associated with the difficulties that the device size may present in accessing certain treatment areas. Specifically, instances may arise where the device may have a shaft diameter that is too wide or shaft working length that is not sufficiently long making the desired access problematic. In additional, present devices used for tissue removal may suffer from poor visibility at the working end of the device where the overall size or orientation of the device tip obscures the physician&#39;s view of the surgical field. The inability to easily access and visualize the surgical field is a significant disadvantage in using electrosurgical techniques for tissue ablation, particularly in arthroscopic, otolaryngological, and spinal procedures. 
     Alternative devices for tissue treatment in narrow anatomies, such as CO2 lasers or microdebriders, may suffer from additional shortcomings in addition to obstacles attributed to the size of the device. For example, a CO2 laser may require a substantially longer set up time prior to the actual procedure, and such lasers are further impaired by relatively smaller tissue removal rate and increased collateral damage to tissue. Microdebriders typically are not afforded adequate hemostatis capabilities, resulting in the presence of significant amounts of blood likely contributing to blocked visibility of the surgical field and prolonged procedure times as other materials are required to stop bleeding. 
     Accordingly, improved systems and methods are still desired for precise tissue removal in narrow anatomies via electrosurgical ablation of tissue. In particular, improved systems operable designed to provide access to narrow anatomies while allowing increased surgical field visualization would provide a competitive advantage. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a detailed description of exemplary embodiments, reference will now be made to the accompanying drawings in which: 
         FIG. 1  shows an electrosurgical system in accordance with at least some embodiments; 
         FIG. 2  shows an end elevation view of a wand in accordance with at least some embodiments; 
         FIG. 3  shows a cross-sectional view of a wand distal end in accordance with at least some embodiments; 
         FIG. 4  shows a cross-sectional view of a wand in accordance with at least some embodiments; 
         FIG. 5  shows an overhead view of a wand in accordance with at least some embodiments; 
         FIG. 6A  shows a cross-sectional view of a wand connector in accordance with at least some embodiments; 
         FIG. 6B  shows an elevational end-view of a wand connector in accordance with at least some embodiments; 
         FIG. 7A  shows a cross-sectional view of a controller connector in accordance with at least some embodiments; 
         FIG. 7B  shows both an elevational end-view of a controller connector in accordance with at least some embodiments; 
         FIG. 8  shows an electrical block diagram of an electrosurgical controller in accordance with at least some embodiments; and 
         FIG. 9  shows a method in accordance with at least some embodiments. 
     
    
    
     NOTATION AND NOMENCLATURE 
     Certain terms are used throughout the following description and claims to refer to particular system components. As one skilled in the art will appreciate, companies that design and manufacture electrosurgical systems may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. 
     In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection or through an indirect electrical connection via other devices and connections. 
     Reference to a singular item includes the possibility that there are plural of the same items present. More specifically, as used herein and in the appended claims, the singular forms “a,” “an,” “said” and “the” include plural references unless the context clearly dictates otherwise. It is further noted that the claims may be drafted to exclude any optional element. As such, this statement serves as antecedent basis for use of such exclusive terminology as “solely,” “only” and the like in connection with the recitation of claim elements, or use of a “negative” limitation. Lastly, it is to be appreciated that unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. 
     “Active electrode” shall mean an electrode of an electrosurgical wand which produces an electrically-induced tissue-altering effect when brought into contact with, or close proximity to, a tissue targeted for treatment. 
     “Return electrode” shall mean an electrode of an electrosurgical wand which serves to provide a current flow path for electrons with respect to an active electrode, and/or an electrode of an electrical surgical wand which does not itself produce an electrically-induced tissue-altering effect on tissue targeted for treatment. 
     “Digester electrode” or “digester surface” shall mean an electrode or a discrete, electrically connected portion of an active electrode of an electrosurgical wand which serves to produce an additional electrically-induced tissue-altering effect when brought into contact with, or close proximity to by-products or tissue remnants produced by the active electrode. 
     A fluid conduit said to be “within” an elongate shaft shall include not only a separate fluid conduit that physically resides within an internal volume of the elongate shaft, but also situations where the internal volume of the elongate shaft is itself the fluid conduit. 
     Where a range of values is provided, it is understood that every intervening value, between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the invention. Also, it is contemplated that any optional feature of the inventive variations described may be set forth and claimed independently, or in combination with any one or more of the features described herein. 
     All existing subject matter mentioned herein (e.g., publications, patents, patent applications and hardware) is incorporated by reference herein in its entirety except insofar as the subject matter may conflict with that of the present invention (in which case what is present herein shall prevail). The referenced items are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present invention is not entitled to antedate such material by virtue of prior invention. 
     DETAILED DESCRIPTION 
     Before the various embodiments are described in detail, it is to be understood that this invention is not limited to particular variations set forth herein as various changes or modifications may be made, and equivalents may be substituted, without departing from the spirit and scope of the invention. As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present invention. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, process act(s) or step(s) to the objective(s), spirit or scope of the present invention. All such modifications are intended to be within the scope of the claims made herein. 
       FIG. 1  illustrates an electrosurgical system  100  in accordance with at least some embodiments. In particular, the electrosurgical system comprises an electrosurgical wand  102  (hereinafter “wand”) coupled to an electrosurgical controller  104  (hereinafter “controller”). The wand  102  comprises an elongate shaft  106  that defines distal end  108  where at least some electrodes are disposed. The elongate shaft  106  further defines a handle or proximal end  110 , where a physician grips the wand  102  during surgical procedures. The wand  102  further comprises a flexible multi-conductor cable  112  housing a plurality of electrical leads (not specifically shown in  FIG. 1 ), and the flexible multi-conductor cable  112  terminates in a wand connector  114 . As shown in  FIG. 1 , the wand  102  couples to the controller  104 , such as by a controller connector  120  on an outer surface  122  (in the illustrative case of  FIG. 1 , the front surface). 
     Though not visible in the view of  FIG. 1 , in some embodiments the wand  102  has one or more internal fluid conduits coupled to externally accessible tubular members. As illustrated, the wand  102  has a flexible tubular member  116  and a second flexible tubular member  118 . In some embodiments, the flexible tubular member  116  is used to provide electrically conductive fluid (e.g., saline) to the distal end  108  of the wand. Likewise in some embodiments, flexible tubular member  118  is used to provide aspiration to the distal end  108  of the wand. 
     Still referring to  FIG. 1 , a display device or interface panel  124  is visible through the outer surface  122  of the controller  104 , and in some embodiments a user may select operational modes of the controller  104  by way of the interface device  124  and related buttons  126 . 
     In some embodiments the electrosurgical system  100  also comprises a foot pedal assembly  130 . The foot pedal assembly  130  may comprise one or more pedal devices  132  and  134 , a flexible multi-conductor cable  136  and a pedal connector  138 . While only two pedal devices  132 ,  134  are shown, one or more pedal devices may be implemented. The outer surface  122  of the controller  104  may comprise a corresponding connector  140  that couples to the pedal connector  138 . A physician may use the foot pedal assembly  130  to control various aspects of the controller  104 , such as the operational mode. For example, a pedal device, such as pedal device  132 , may be used for on-off control of the application of radio frequency (RF) energy to the wand  102 , and more specifically for control of energy in an ablation mode. A second pedal device, such as pedal device  134 , may be used to control and/or set the operational mode of the electrosurgical system. For example, actuation of pedal device  134  may switch between energy levels of an ablation mode. 
     The electrosurgical system  100  of the various embodiments may have a variety of operational modes. One such mode employs Coblation® technology. In particular, the assignee of the present disclosure is the owner of Coblation technology. Coblation technology involves the application of a radio frequency (RF) signal between one or more active electrodes and one or more return electrodes of the wand  102  to develop high electric field intensities in the vicinity of the target tissue. The electric field intensities may be sufficient to vaporize an electrically conductive fluid over at least a portion of the one or more active electrodes in the region between the one or more active electrodes and the target tissue. The electrically conductive fluid may be inherently present in the body, such as blood, or in some cases extracellular or intracellular fluid. In other embodiments, the electrically conductive fluid may be a liquid or gas, such as isotonic saline. In some embodiments, such as surgical procedures on a disc between vertebrae, the electrically conductive fluid is delivered in the vicinity of the active electrode and/or to the target site by the wand  102 , such as by way of the internal passage and flexible tubular member  116 . 
     When the electrically conductive fluid is heated to the point that the atoms of the fluid vaporize faster than the atoms re-condense, a gas is formed. When sufficient energy is applied to the gas, the atoms collide with each other causing a release of electrons in the process, and an ionized gas or plasma is formed (the so-called “fourth state of matter”). Stated otherwise, plasmas may be formed by heating a gas and ionizing the gas by driving an electric current through the gas, or by directing electromagnetic waves into the gas. The methods of plasma formation give energy to free electrons in the plasma directly, electron-atom collisions liberate more electrons, and the process cascades until the desired degree of ionization is achieved. A more complete description of plasma can be found in Plasma Physics, by R. J. Goldston and P. H. Rutherford of the Plasma Physics Laboratory of Princeton University (1995), the complete disclosure of which is incorporated herein by reference. 
     As the density of the plasma becomes sufficiently low (i.e., less than approximately 1020 atoms/cm3 for aqueous solutions), the electron mean free path increases such that subsequently injected electrons cause impact ionization within the plasma. When the ionic particles in the plasma layer have sufficient energy (e.g., 3.5 electron-Volt (eV) to 5 eV), collisions of the ionic particles with molecules that make up the target tissue break molecular bonds of the target tissue, dissociating molecules into free radicals which then combine into gaseous or liquid species. Often, the electrons in the plasma carry the electrical current or absorb the electromagnetic waves and, therefore, are hotter than the ionic particles. Thus, the electrons, which are carried away from the target tissue toward the active or return electrodes, carry most of the plasma&#39;s heat, enabling the ionic particles to break apart the target tissue molecules in a substantially non-thermal manner. 
     By means of the molecular dissociation (as opposed to thermal evaporation or carbonization), the target tissue is volumetrically removed through molecular dissociation of larger organic molecules into smaller molecules and/or atoms, such as hydrogen, oxygen, oxides of carbon, hydrocarbons and nitrogen compounds. The molecular dissociation completely removes the tissue structure, as opposed to dehydrating the tissue material by the removal of liquid within the cells of the tissue and extracellular fluids, as occurs in related art electrosurgical desiccation and vaporization. A more detailed description of the molecular dissociation can be found in commonly assigned U.S. Pat. No. 5,697,882, the complete disclosure of which is incorporated herein by reference. 
     In addition to the Coblation mode, the electrosurgical system  100  of  FIG. 1  may also in particular situations be useful for sealing larger arterial vessels (e.g., on the order of about 1 mm in diameter), when used in what is known as a coagulation mode. Thus, the system of  FIG. 1  may have an ablation mode where RF energy at a first voltage is applied to one or more active electrodes sufficient to effect molecular dissociation or disintegration of the tissue, and the system of  FIG. 1  may have a coagulation mode where RF energy at a second, lower voltage is applied to one or more active electrodes (either the same or different electrode(s) as the ablation mode) sufficient to heat, shrink, seal, fuse, and/or achieve homeostasis of severed vessels within the tissue. 
     The energy density produced by electrosurgical system  100  at the distal end  108  of the wand  102  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/or sharp edges on the electrode surfaces; electrode materials; applied voltage; current limiting of one or more electrodes (e.g., by placing an inductor in series with an electrode); electrical conductivity of the fluid in contact with the electrodes; density of the conductive fluid; and other factors. Accordingly, these factors can be manipulated to control the energy level of the excited electrons. Because different tissue structures have different molecular bonds, the electrosurgical system  100  may be configured to produce energy sufficient to break the molecular bonds of certain tissue but insufficient to break the molecular bonds of other tissue. For example, fatty tissue (e.g., adipose) has double bonds that require an energy level higher than 4 eV to 5 eV (i.e., on the order of about 8 eV) to break. Accordingly, the Coblation® technology in some operational modes does not ablate such fatty tissue; however, the Coblation® technology at the lower energy levels may be used to effectively ablate cells to release the inner fat content in a liquid form. Other modes may have increased energy such that the 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 electrodes). 
     A more complete description of the various phenomena can be found in commonly assigned U.S. Pat. Nos. 6,355,032; 6,149,120 and 6,296,136, the complete disclosures of which are incorporated herein by reference. 
       FIG. 2  illustrates an end elevation view of the distal end  108  of wand  102  in accordance with at least some embodiments. In some embodiments, a portion of the elongate shaft  106  may be made of a metallic material (e.g., Grade TP304 stainless steel hypodermic tubing). In other embodiments, portions of the elongate shaft may be constructed of other suitable materials, such as inorganic insulating materials. The elongate shaft  106  may define a circular cross-section at the handle or proximal end  110  (not shown in  FIG. 2 ), and at least a portion of the distal end  108  may also be circular in cross-section. For wands intended for use in otolaryngological procedures, and in particular for use in procedures where access to the larynx is desired, the diameter of shaft  106  may be 3 centimeters or less, and in some cases 2.8 millimeters. Additionally, the length of shaft  106  from handle  110  to the tip of distal end  108  may be 8.5 inches, and in some cases 7.5 inches. Other dimensions may be equivalently used when the surgical procedure allows. 
     In embodiments where the elongate shaft is metallic, the distal end  108  may further comprise a non-conductive spacer  200  coupled to the elongate shaft  106 . In some cases the spacer  200  is ceramic, but other non-conductive materials resistant to degradation when exposed to plasma may be equivalently used (e.g., glass). The spacer  200  supports electrodes of conductive material, with illustrative active electrode labeled  202  in  FIG. 2 . Active electrode  202  defines an exposed surface area of conductive material, where active electrode  202  is a loop of wire of particular diameter. For embodiments using a loop of wire, the loop of wire may be molybdenum or tungsten having a diameter between and including 0.008 and 0.015 inches, and more preferably of 0.010 inches. In certain embodiments, the active electrode  202  has an exposed ablative surface  203  bridging aspiration aperture  207  wherein exposed surface  203  defines a straight portion of active electrode  202  that is oriented substantially parallel to the long axis of distal end  108 . 
     In certain embodiments electrode  202  has an active electrode recessed secondary surface  210  that may be oriented substantially transverse to the long axis of the distal end  108  and may be recessed within the spacer  200 , so that the surface  210  is disposed below a top surface  220  of the spacer  200 . Secondary surface  210  may be recessed within an elongate nest provided by spacer  200 , the nest being deep enough so that the secondary  210  may not treat tissue inadvertently, however is capable of applying energy to a target tissue, should the surgeon intentionally oppose this surface  210  against tissue so that the tissue extends into the recesses area around secondary electrode surface  210 . Is alternative embodiments, this surface  210  may be insulated so as to not be an active surface (not shown here). 
     Referring still to  FIG. 2 , wand  102  includes a return electrode  204  for completing the current path between active electrode  202  and controller  104  (not shown in this figure). Return electrode  204  is suitably connected to controller  104 . Return electrode  204  is preferably a semi-annular member defining the exterior of shaft  106 , and a distal portion of return electrode  204  on the side of shaft  106  corresponding to the exposed surface  203  of active electrode  202  is preferably exposed (e.g., approximately half the circumference of return electrode  204  is exposed and free of insulative covering). Additionally, a section of the distal portion of return electrode  204  may be disposed within sheath  209 , preferably the section disposed on the opposite side of shaft  106  from exposed surface  203  of active electrode  202 . At least a proximal portion of return electrode  204  is disposed within an electrically insulative sheath  209 , which is typically formed as one, or more electrically insulative sheaths or coatings, such as polytetrafluoroethylene, polyimide, and the like. The provision of the electrically insulative sheath  209  encircling over a portion of return electrode  204  may minimize prevents direct electrical contact between return electrode  204  and any adjacent body structure or the surgeon. Such direct electrical contact between a body structure (e.g., tendon) and an exposed common electrode member  204  could result in unwanted heating and necrosis of the structure at the point of contact causing necrosis. Return electrode  204  is preferably formed from an electrically conductive material, usually metal, which is selected from the group consisting of stainless steel alloys, platinum or its alloys, titanium or its alloys, molybdenum or its alloys, and nickel or its alloys. 
     In some embodiments saline is delivered to the distal end  108  of wand, possibly to aid in plasma creation. Referring still to  FIG. 2 , discharge aperture  208  is illustrated on the distal end  108  disposed through return electrode  204 . Discharge aperture  208  is formed through the exposed portion of return electrode  204  on the same side of shaft  106  as exposed surface  203  of active electrode  202 . It is preferable that discharge aperture  208  is disposed proximally of aspiration aperture  207  and the exposed surface  203  of active electrode  202 . The discharge aperture  208  is fluidly coupled to the flexible tubular member  116  ( FIG. 1 ) by way of a fluid conduit within the wand  102 . Thus, saline or other fluid may be pumped into the flexible tubular member  116  ( FIG. 1 ) and discharged through discharge aperture  208  to further aid in developing consistent wetting around the exposed surface or circumference of return electrode  204 . Discharge aperture  208  is disposed towards the proximal end of return electrode  204 , so that a large portion of the return electrode surface area is sufficiently wetted, as the fluid travels from the discharge aperture  208  towards the exposed surface  203 . Discharge aperture  208  is approximately crescent or boomerang shaped with the widest portion or widest opening, as measured parallel to distal end long axis, substantially in line with active surface  203 . This aperture  208  shape has been found to produce a preferable uniform and directed flow, distally, over the return electrode surface and towards the active electrode  202 . 
     In yet still further embodiments, aspiration is provided at the distal end  108  of the wand  102 .  FIGS. 2 and 3  illustrate aspiration aperture  207  (i.e., suction port  207 ) at the distal end  108  of the device and disposed through the non-conductive spacer  200 . Suction aperture  207  is disposed at distal end  108  and in certain embodiments preferably only located on one side of spacer  200  and disposed through spacer  200  on the same side of shaft  106  as the exposed surface  203  of active electrode  202  and discharge aperture  208 . More particularly, and as stated above, suction port  207  is disposed adjacent to and behind exposed surface  203  such that exposed surface  203  bridges or traverses a portion of suction port  207 . Suction port  207  provides a path to aspirate the area near the distal end  108 , so as to remove excess fluids, ablative by-products, and remnants of ablation created by exposed surface  203  of active electrode  202 . The location of suction port  207  further provides for ample wetting of the active and return electrodes, with the saline flowing out from discharge aperture  208  and then being pulled toward active electrode  202  by the fluid flow induced from suction port  207 . Applicants have found it is particularly beneficial to provide broader wetting of the exposed surface of return electrode  204 , enabling more uniform plasma formation particularly on the exposed surface  203  of active electrode  202 . 
     Referring now to  FIG. 3 , a cross-section of the distal tip of the wand in accordance with certain embodiments is shown. In particular, digester electrode or digester surface  205  of active electrode  202  is shown. Digester surface  205  is shown disposed within a portion of spacer  200  and located substantially within the aspiration fluid path. In particular, digester surface  205  is disposed coaxially within suction lumen  206 , wherein suction lumen  206  is fluidly connected to suction port  207 , and where digester surface  205  is recessed away from the opening of suction port  207 . In certain embodiments, digester surface  205  is a discrete section of the loop of wire that forms active electrode  202 , and digester surface  205  is thereby electrically connected to active electrode  202 . Active electrode  202  may be formed in a shape resembling a hook, where exposed surface  203  forms one portion of the hook and digester surface  205  forms the opposite side of the hook, with a contiguous piece of active electrode  202  (secondary surface  210 ) spanning transversely to the long axis of distal end  108  and routed within a recessed portion of spacer  200 . Digester surface  205  is preferably arranged parallel to and co-planar with exposed surface  203  of active electrode  202 . Digester surface  205  may preferably include at least one asperity, such as a sharp edge or point, for example surface end  211 , where a higher charge density will form, so that when a high frequency voltage is applied between the active electrode and return electrode, a plasma may readily initiate in the presence of an electrically conductive fluid, at this asperity, so as to further morcellate any tissue or ablation by-products that are travelling through the suction lumen  206 . Fluids, ablative by-products, and tissue remnants produced by the initial tissue treatment initiated by exposed surface  203  are aspirated away from the tissue treatment site via suction port  207  and into suction lumen  206  such that the ablative by-products are exposed to the electrically-induced effects of digester electrode  205  and thereby further reduced for uninterrupted aspiration. By disposing digester surface  205  within the aspiration fluid flow path, additional ablation and breakdown of the initial ablative by-products is produced in order to minimize clogging of suction lumen  206 . Suction lumen  206  is approximately perpendicular to suction port  207  and may be coaxial with the distal end long axis. A diameter of suction lumen  206  may preferably be less than a diameter of the suction port  207 , so as fit within the confines of the smaller wand shaft diameter, as described earlier. 
     As shown for example in  FIGS. 2 and 3 , return electrode  204  is not directly connected to active electrode  202 . To complete a current path so that active electrode  202  is electrically connected to return electrode  204  in the presence of a target tissue, electrically conducting liquid (e.g., isotonic saline) is caused to flow along liquid paths emanating from discharge aperture  208  toward and within suction port  207  and suction  206 , and contacting both return electrode  204  and active electrode  202 . When a voltage difference is applied between active electrode  202  and return electrode  204 , high electric field intensities will be generated at active electrode  202 , and particularly adjacent to exposed surface  203  and digester surface  205  of active electrode  202 . As current flows from active electrode  202  to the return electrode  204  in the presence of electrically conductive fluid, the high electric field intensities cause ablation of target tissue adjacent exposed surface  203  of active electrode  202 . Further ablation and breakdown of aspirated by-products from the initial ablation of the target tissue occurs adjacent digester surface  205  of active electrode  202  in order to prevent clogging of the aspiration features of the device. 
       FIG. 4  shows a cross-sectional elevation view of a wand  102  in accordance with at least some embodiments. In particular,  FIG. 4  shows the handle or proximal end  110  coupled to the elongate shaft  106 . As illustrated, the elongate shaft  106  telescopes within the handle, but other mechanisms to couple the elongate shaft to the handle may be equivalently used. The elongate shaft  106  defines internal conduit  400  that serves several purposes. For example, in the embodiments illustrated by  FIG. 4  the electrical leads  402  and  404  extend through the internal conduit  400  to electrically couple to the active electrode  202  and return electrode  204 , respectively. Likewise, the flexible tubular member  116  extends through the internal conduit  400  to fluidly couple to discharge aperture  208 . 
     The internal conduit  400  also serves as the aspiration route. In particular,  FIG. 4  illustrates suction port  207 . In the embodiments illustrated the flexible tubular member  118 , through which aspiration is performed, couples through the handle and then fluidly couples to the internal conduit  400 . Thus, the suction provided through flexible tubular member  118  provides aspiration via suction lumen  206  at the suction port  207 . The fluids that are drawn into the internal fluid conduit  400  may abut the portion of the flexible tubular member  116  that resides within the internal conduit as the fluids are drawn along the conduit; however, the flexible tubular member  116  is sealed, and thus the aspirated fluids do not mix with the fluid (e.g., saline) being pumped through the flexible tubular member  116 . Likewise, the fluids that are drawn into the internal fluid conduit  400  may abut portions of the electrical leads  402  and  404  within the internal fluid conduit  400  as the fluids are drawn along the conduit. However, the electrical leads are insulated with an insulating material that electrically and fluidly isolates the leads from any substance within the internal fluid conduit  400 . Thus, the internal fluid conduit serves, in the embodiments shown, two purposes—one to be the pathway through which the flexible tubular member  116  and electrical leads traverse to reach the distal end  108 , and also as the conduit through which aspiration takes place. In other embodiments, the flexible tubular member  118  may extend partially or fully through the elongate shaft  106 , and thus more directly couple to the aspiration aperture. 
     The offsets of the elongate shaft  106  are not visible in  FIG. 4  because of the particular view; however,  FIG. 5  shows illustrative offsets.  FIG. 5  shows an overhead view of the wand  102  in an orientation where the offsets in the elongate shaft  106  are visible. The illustrative wand  102  is designed and constructed for use in procedures where other equipment (e.g., an arthroscopic camera or surgical microscope) may be present and where those other devices prevent use of straight elongate shaft. In particular, the distal end  108  defines wand tip axis  502 , and the elongate shaft  106  also defines a medial portion  500  which has an axis  504  (hereafter, the medial axis  504 ). In the particular embodiments illustrated the angle α between the medial axis  504  and the wand tip axis  502  is non-zero, and in some embodiments the acute angle α between the medial axis  504  and the wand tip axis  502  is 16 degrees, but greater or lesser angles may be equivalently used. 
     Likewise, the elongate shaft  106  of  FIG. 5  defines a proximal portion  506  with an axis  508  (hereafter, the proximal axis  508 ). In the particular embodiment illustrated the angle β between the proximal axis  508  and the medial axis  504  is non-zero, and in some embodiments the acute angle β between the proximal axis  508  and the medial axis  504  is 55 degrees, but greater or lesser angles may be equivalently used. 
     As illustrated in  FIG. 1 , flexible multi-conductor cable  112  (and more particularly its constituent electrical leads  402 ,  404  and possibly others) couple to the wand connector  114 . Wand connector  114  couples the controller  104 , and more particularly the controller connector  120 .  FIG. 6  shows both a cross-sectional view (right) and an end elevation view (left) of wand connector  114  in accordance with at least some embodiments. In particular, wand connector  114  comprises a tab  600 . Tab  600  works in conjunction with a slot on controller connector  120  (shown in  FIG. 7 ) to ensure that the wand connector  114  and controller connector  120  only couple in one relative orientation. The illustrative wand connector  114  further comprises a plurality of electrical pins  602  protruding from wand connector  114 . In many cases, the electrical pins  602  are coupled one each to an electrical lead of electrical leads  604  (two of which may be leads  402  and  404  of  FIG. 4 ). Stated otherwise, in particular embodiments each electrical pin  602  couples to a single electrical lead, and thus each illustrative electrical pin  602  couples to a single electrode of the wand  102 . In other cases, a single electrical pin  602  couples to multiple electrodes on the electrosurgical wand  102 . While  FIG. 6  shows four illustrative electrical pins, in some embodiments as few as two electrical pins, and as many as 26 electrical pins, may be present in the wand connector  114 . 
       FIG. 7  shows both a cross-sectional view (right) and an end elevation view (left) of controller connector  120  in accordance with at least some embodiments. In particular, controller connector  120  comprises a slot  700 . Slot  700  works in conjunction with a tab  600  on wand connector  114  (shown in  FIG. 5 ) to ensure that the wand connector  114  and controller connector  120  only couple in one orientation. The illustrative controller connector  120  further comprises a plurality of electrical pins  702  residing within respective holes of controller connector  120 . The electrical pins  702  are coupled to terminals of a voltage generator within the controller  104  (discussed more thoroughly below). When wand connector  114  and controller connector  120  are coupled, each electrical pin  702  couples to a single electrical pin  602 . While  FIG. 7  shows only four illustrative electrical pins, in some embodiments as few as two electrical pins and as many as 26 electrical pins may be present in the wand connector  120 . 
     While illustrative wand connector  114  is shown to have the tab  600  and male electrical pins  602 , and controller connector  120  is shown to have the slot  700  and female electrical pins  702 , in alternative embodiments the wand connector has the female electrical pins and slot, and the controller connector  120  has the tab and male electrical pins, or other combination. In other embodiments, the arrangement of the pins within the connectors may enable only a single orientation for connection of the connectors, and thus the tab and slot arrangement may be omitted. In yet still other embodiments, other mechanical arrangements to ensure the wand connector and controller connector couple in only one orientation may be equivalently used. In the case of a wand with only two electrodes, and which electrodes may be either active or return electrodes as the physical situation dictates, there may be no need to ensure the connectors couple in a particular orientation. 
       FIG. 8  illustrates a controller  104  in accordance with at least some embodiments. In particular, the controller  104  comprises a processor  800 . The processor  800  may be a microcontroller, and therefore the microcontroller may be integral with random access memory (RAM)  802 , read-only memory (RAM)  804 , digital-to-analog converter (D/A)  806 , digital outputs (D/O)  808  and digital inputs (D/I)  810 . The processor  800  may further provide one or more externally available peripheral busses, such as a serial bus (e.g., I2C), parallel bus, or other bus and corresponding communication mode. The processor  800  may further be integral with a communication logic  812  to enable the processor  800  to communicate with external devices, as well as internal devices, such as display deice  124 . Although in some embodiments the controller  104  may implement a microcontroller, in yet other embodiments the processor  800  may be implemented as a standalone central processing unit in combination with individual RAM, ROM, communication, D/A, D/O and D/I devices, as well as communication port hardware for communication to peripheral components. 
     ROM  804  stores instructions executable by the processor  800 . In particular, the ROM  804  may comprise a software program that implements the various embodiments of periodically reducing voltage generator output to change position of the plasma relative to the electrodes of the wand (discussed more below), as well as interfacing with the user by way of the display device  124  and/or the foot pedal assembly  130  ( FIG. 1 ). The RAM  802  may be the working memory for the processor  800 , where data may be temporarily stored and from which instructions may be executed. Processor  800  couples to other devices within the controller  104  by way of the D/A converter  806  (e.g., the voltage generator  816 ), digital outputs  808  (e.g., the voltage generator  816 ), digital inputs  810  (i.e., push button switches  126 , and the foot pedal assembly  130  ( FIG. 1 )), and other peripheral devices. 
     Voltage generator  816  generates selectable alternating current (AC) voltages that are applied to the electrodes of the wand  102 . In the various embodiments, the voltage generator defines two terminals  824  and  826 . In accordance with the various embodiments, the voltage generator generates an alternating current (AC) voltage across the terminals  824  and  826 . In at least some embodiments the voltage generator  816  is electrically “floated” from the balance of the supply power in the controller  104 , and thus the voltage on terminals  824 ,  826 , when measured with respect to the earth ground or common (e.g., common  828 ) within the controller  104 , may or may not show a voltage difference even when the voltage generator  816  is active. 
     The voltage generated and applied between the active terminal  824  and return terminal  826  by the voltage generator  816  is a RF signal that, in some embodiments, has a frequency of between about 5 kilo-Hertz (kHz) and 20 Mega-Hertz (MHz), in some cases being between about 30 kHz and 2.5 MHz, often between about 100 kHz and 200 kHz. In applications associated with otolaryngology—head and neck procedures, a frequency of about 100 kHz appears most effective. The RMS (root mean square) voltage generated by the voltage generator  816  may be in the range from about 5 Volts (V) to 1000 V, preferably being in the range from about 10 V to 500 V, often between about 100 V to 350 V depending on the active electrode size and the operating frequency. The peak-to-peak voltage generated by the voltage generator  816  for ablation or cutting in some embodiments is a square wave form in the range of 10 V to 2000 V and in some cases in the range of 100 V to 1800 V and in other cases in the range of about 28 V to 1200 V, often in the range of about 100 V to 320 V peak-to-peak (again, depending on the electrode size and the operating frequency). 
     Still referring to the voltage generator  816 , the voltage generator  816  delivers average power levels ranging from several milliwatts to hundreds of watts per electrode, depending on the voltage applied for the target tissue being treated, and/or the maximum allowed temperature selected for the wand  102 . The voltage generator  816  is configured to enable a user to select the voltage level according to the specific requirements of a particular procedure. A description of one suitable voltage generator  816  can be found in commonly assigned U.S. Pat. Nos. 6,142,992 and 6,235,020, the complete disclosure of both patents are incorporated herein by reference for all purposes. 
     In some embodiments, the various operational modes of the voltage generator  816  may be controlled by way of digital-to-analog converter  806 . That is, for example, the processor  800  may control the output voltage by providing a variable voltage to the voltage generator  816 , where the voltage provided is proportional to the voltage generated by the voltage generator  816 . In other embodiments, the processor  800  may communicate with the voltage generator by way of one or more digital output signals from the digital output  808  device, or by way of packet based communications using the communication device  812  (connection not specifically shown so as not to unduly complicate  FIG. 8 ). 
       FIG. 8  also shows a simplified side view of the distal end  108  of the wand  102 . As shown, illustrative active electrode  202  of the wand  102  electrically couples to terminal  824  of the voltage generator  816  by way of the connector  120 , and return electrode  204  electrically couples to terminal  826  of the voltage generator  816 . 
       FIG. 9  shows a method in accordance with at least some embodiments. In particular, the method starts (block  900 ) and proceeds to: flowing a conductive fluid within a fluid conduit disposed within a electrosurgical wand, the conductive fluid discharges through a discharge aperture and flows through a return electrode disposed distally from the fluid conduit, and is then discharged over an active electrode and a digester electrode recessed away from the active electrode and electrically connected to the active electrode (block  902 ); applying electrical energy between the active electrode and the return electrode (block  904 ); forming, responsive to the energy, a localized plasma proximate the active electrode and the digester electrode (block  906 ); ablating, by the localized plasma, a portion of a target tissue proximate to the active electrode (block  908 ); and breaking down, responsive to the energy, aspirated fragmented by-products of the ablated portion of the target tissue proximate to the digester electrode (block  910 ). And thereafter the method ends (block  912 ). 
     The above discussion is meant to be illustrative of the principles and various embodiments of the present invention. Numerous variations and modifications possible. For example, while in some cases electrodes were designated as upper electrodes and lower electrodes, such a designation was for purposes of discussion, and shall not be read to require any relationship to gravity during surgical procedures. It is intended that the following claims be interpreted to embrace all such variations and modifications. 
     While preferred embodiments of this disclosure have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teaching herein. The embodiments described herein are exemplary only and are not limiting. Because many varying and different embodiments may be made within the scope of the present inventive concept, including equivalent structures, materials, or methods hereafter thought of, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirements of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.