Patent Publication Number: US-8992521-B2

Title: Flexible electrosurgical ablation and aspiration electrode with beveled active surface

Description:
PRIORITY 
     This application is a continuation-in-part of U.S. patent application Ser. No. 13/091,584, filed Apr. 21, 2011, which, in turn, claims the benefit of U.S. Provisional Application Ser. No. 61/342,990, filed Apr. 22, 2010. The contents of all prior applications are hereby incorporated by reference herein in their entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to electrosurgical devices for use in a conductive fluid environment, and more specifically to aspirating ablation electrosurgical devices for bulk vaporization of tissue in a conductive fluid environment that may be manufactured at low cost and have increased efficiency through the minimization of process heat loss. 
     BACKGROUND OF THE INVENTION 
     Minimally invasive surgical techniques have gained significant popularity due to their ability to accomplish desirable outcomes with reduced patient pain and accelerated recovery and return of the patient to normal activities. Arthroscopic surgery, wherein the intra-articular space is filled with fluid, allows orthopedic surgeons to efficiently perform procedures using special purpose instruments designed specifically for arthroscopy. Among these special purpose tools are various manual graspers and biters, powered shaver blades and burs, and electrosurgical devices. During the last several years specialized arthroscopic electrosurgical electrodes referred to in the art as “ablators” have been developed. Examples of such instruments include ArthroWands manufactured by Arthrocare (Sunnyvale, Calif.), VAPR electrodes manufactured by Mitek Products Division of Johnson &amp; Johnson (Westwood, Mass.) and electrodes by Smith and Nephew, Inc. (Andover, Mass.). These ablator electrodes differ from conventional arthroscopic electrosurgical electrodes in that they are designed for the bulk removal of tissue by vaporization rather than the cutting of tissue or coagulation of bleeding vessels. While standard electrodes are capable of ablation, their geometries are generally not efficient for accomplishing this task. The tissue removal rates of ablator electrodes are lower than those of arthroscopic shaver blades, however, electrosurgical ablators are used because they achieve hemostasis (stop bleeding) during use and are able to efficiently remove tissue from bony surfaces. Ablator electrodes are used in an environment filled with electrically conductive fluid. 
     During ablation, current flows from the ablator into the conductive fluid and heats the fluid to its boiling point. Heating of the conductive fluid is proportional to the density of electrical current flowing from the electrode into the fluid. Regions of high current density will experience higher rates of heating as compared to regions of low current density. In general, regions of high current density occur at the corners and edges of the electrode. Steam bubbles form first at the edges of an ablator but eventually cover virtually the electrode&#39;s entire surface. When a steam bubble reaches a critical size, arcing occurs within the bubble and enclosed portion of tissue. A train of sparks occurs within the bubble with the train ending when the bubble grows too large or the tissue enclosed in the bubble is evaporated and conditions within the bubble become unfavorable for sparking. 
     During ablation, water within the target tissue is vaporized. Because volumes of tissue are vaporized rather than discretely cut out and removed from the surgical site, the power requirements of ablator electrodes are generally higher than those of other arthroscopic electrosurgical electrodes. The efficiency of the electrode design and the characteristics of the Radio Frequency (RF) power supplied to the electrode also affect the amount of power required for ablation. Electrodes with inefficient designs and/or powered by RF energy with poorly suited characteristics will require higher power levels than those with efficient designs and appropriate generators. Because of these factors the ablation power levels of devices produced by different manufacturers vary widely, with some using power levels significantly higher than those commonly used by arthroscopists. Ablator electrode systems from some manufacturers may use up to 280 Watts, significantly higher than the 30 to 70 Watt range generally used by other arthroscopic electrosurgical electrodes. 
     During arthroscopic electrosurgery, all of the RF energy supplied to the electrode is converted into heat, thereby raising the temperature of the fluid within the joint and the temperature of adjacent tissue. Prior to the introduction of ablator electrodes, the temperature of the fluid within the joint was not of concern to the surgeon. However, due to the higher power levels at which they generally operate and the longer periods of time that they are energized, fluid temperature is a major concern during the use of ablator electrodes. Standard arthroscopic electrosurgical electrodes are usually energized for only brief periods, generally measured in seconds, while specific tissue is resected or modified, or a bleeder coagulated. In contrast, ablator electrodes are energized for longer periods of time, often measured in minutes, while volumes of tissue are vaporized. 
     The temperature of the fluid within the joint is critical since cell death occurs at 45.degree. C., a temperature easily reached with high-powered ablators if fluid flow through the surgical site is insufficient. Patient injury may result. Such injuries have been documented. 
     The likelihood of thermal injury is strongly affected by the amount of power supplied to the ablator. This, in turn, is determined by the efficiency of the ablator and the speed with which the surgeon desires to remove tissue. A highly efficient ablator will allow the surgeon to remove tissue at desirably high rates while requiring low levels of power. Under these conditions, the likelihood of thermal injuries is reduced significantly. 
     Ablator electrodes are produced in a variety of sizes and configurations to suit a variety of procedures. Ablators for use in ankle, wrist or elbow arthroscopy, for instance, are smaller than those used in the knee or shoulder. In each of these sizes, a variety of configurations are produced to facilitate access to various structures within the joint being treated. These configurations differ in the working length of the electrode (the maximum distance that an electrode can be inserted into a joint), in the size and shape of their ablating surfaces and in the angle between the ablating face and the axis of the electrode shaft. Electrodes are typically designated by the angle between a normal to the ablating surface and the axis of the electrode shaft, and by the size of their ablating surface and any associated insulator. 
     Primary considerations of surgeons when choosing a particular configuration of ablator for a specific procedure are its convenience of use (the ease with which the instrument is able to access certain structures) and the speed with which the ablator will be able to complete the required tasks. When choosing between two configurations capable of accomplishing a particular task, surgeons will generally choose the ablator with the larger ablating surface so as to remove tissue more quickly. This is particularly true for procedures during which large volumes of tissue must be removed. One such procedure is acromioplasty, the reshaping of the acromion. The underside of the acromion is covered with highly vascular tissue that may bleed profusely when removed by a conventional powered cutting instrument, such as an arthroscopic shaver blade. Ablator electrodes are used extensively during this procedure since they are able to remove tissue without the bleeding which obscures the surgeon&#39;s view of the site. Ablation in the area under the acromion is most efficiently accomplished using an electrode on which a line normal to the ablating surface is approximately perpendicular to the axis of the ablator shaft. Such an electrode is designated as a “90 Degree Ablator” or a “side effect” ablator. Examples of such electrodes include the “3.2 mm 90 Degree Three-Rib UltrAblator” by Linvatec Corporation (Largo, Fla.), the “90 Degree Ablator” and “90 Degree High Profile Ablator” by Smith and Nephew (Andover, Mass.), the “Side Effect VAPR Electrode” by Mitek Products Division of Johnson and Johnson, and the “3.5 mm 90 Degree Arthrowand”, “3.6 mm 90 Degree Lo Pro Arthrowand”, and “4.5 mm 90 Deg. Eliminator Arthrowand” by Arthrocare Corporation. 
     Recently ablator electrodes have been configured with a means of aspiration to remove bubbles and debris from the surgical site. During electrosurgery in a conductive fluid environment, tissue is vaporized, thereby producing steam bubbles that may obscure the view of the surgeon or displace saline from the area of the intra-articular space that the surgeon wishes to affect. In the case of ablation (bulk vaporization of tissue), the number and volume of bubbles produced is even greater than when using other electrodes since fluid is continually boiling at the active electrode during use. Ideally, flow through the joint carries these bubbles away; however, in certain procedures this flow is insufficient to remove all of the bubbles. The aspiration means on an aspirating ablator removes some bubbles as they are formed by the ablation process, and others after they have collected in pockets within the joint. The ablator aspiration means is typically connected to an external vacuum source that provides suction for bubble evacuation. 
     Aspiration on currently available ablator products may be divided into two categories according to their level of flow. High-flow ablators have an aspiration tube, the axis of which is coaxial with the axis of the ablator rod or tube, that draws in bubbles and fluid through its distal opening and/or openings cut into the tube wall near its distal tip. High-flow ablators may decrease the average joint fluid temperature by removing heated saline (waste heat since it is an undesirable byproduct of the process) from the general area in which ablation is occurring. The effectiveness of the aspiration, both for removal of bubbles and for removal of waste heat, will be affected by the distance between the aspiration opening and the active electrode. The distal tip of the aspiration tube is generally positioned several millimeters proximal to the active electrode so as to not to obstruct the surgeon&#39;s view of the electrode during use. Decreasing this distance is desirable since doing so will increase the effectiveness of the aspiration; however, this must be accomplished without limiting the surgeon&#39;s view or decreasing the ablator&#39;s ability to access certain structures during use. Examples of high-flow aspirating ablators systems include the Three Rib-Aspirating ablators by Linvatec Corporation and the 2.3 mm and 3.5 mm Suction Sheaths for the VAPR system by Mitek Products, the sheaths being used with standard VAPR ablation probes. 
     Arthrex, Incorporated (Naples, Fla.) markets aspirating ablators in which the aspiration port is in the distal-most surface of the device, and the aspiration path runs through the device. These devices have higher flow rates than low-flow ablators, though less than the high-flow models previously herein described. 
     Low-flow ablators are characterized by the aspiration of bubbles and fluid through gaps in the ablating surfaces of the active electrode, conveying them from the surgical site via means in the elongated distal portion of the device. Because the low-flow aspiration tends to draw hot saline from the active site of a thermal process, current low-flow ablators require increased power to operate as effectively as a non-aspirating or high-flow aspirating ablators. In the case of low-flow ablators, the heat removed is necessary process heat rather than the waste heat removed by high-flow ablators. Because of this, aspirating ablators of the low-flow type generally require higher power levels to operate than other ablators thereby generating more waste heat and increasing undesirable heating of the fluid within the joint. Typical of low-flow aspirating ablators are those produced by Arthrocare and Smith and Nephew. 
     Each of these types of aspirating ablator electrodes has its drawbacks. In the case of high-flow aspirating ablators, the aspiration tube increases the diameter of the device, thereby necessitating the use of larger cannulae. In the case of low-flow aspirating ablators, aspiration decreases the efficiency of the probes since process heat is removed from a thermal process. This decreased efficiency results in decreased rates of tissue removal for a given power level. In turn, this results in increased procedure times or necessitates the use of higher power levels to achieve satisfactory tissue removal rates. Both increased procedure time and high power level usage are undesirable as they cause increased heating of the fluid at the site and thereby the likelihood of thermal injury to the patient. 
     U.S. Pat. No. 6,840,937 to Van Wyk discloses an aspirating ablator that minimizes the removal of process heat by placing aspiration ports at a distance from the active electrode, specifically in the distal end of the probe, and in the top surface of the ablator, the top aspiration port being surrounded by the insulator that surrounds the active electrode and the port being displaced a short distance from the active electrode. Aspiration ports positioned in this manner remove debris and aspiration byproducts from regions adjacent to the active electrode rather than through the active electrode in the manner of low-flow ablators thereby minimizing the loss of process heat. However, the construction taught by Van Wyk is not well suited to ablators other than 90-degree ablators, in which the aspirating surface is substantially parallel to the tube axis. The distal portion of the device may be bent to create other angles to the tube axis; however, the bend would be proximal to the distal end assembly and would have a relatively large radius such that the finished product would have to be used with large cannulae, an undesirable condition. 
     U.S. Pat. No. 7,837,683 to Carmel, et al. (herein incorporated by reference in its entirety) describes an aspirating ablator that has an aspiration port in the center of the active electrode. The aspiration port is surrounded by a tubular portion (i.e., wall) that both restricts flow between protuberances surrounding the port and causes aspiration of liquids from regions above (distal to) the ablating surface. The efficiency of the Carmel ablator is increased since the amount of process heat removed is reduced; however, the construction of the device is somewhat complex. Producing ablators of various angles using the construction suggested by Carmel requires that the distal end of the ablator be bent in the same manner as that of the Van Wyk embodiment. The resulting ablator is again too large to be used in small cannulae. 
     Many surgical procedures are not performed inside a natural or formed body cavity and as such are not performed on structures submerged under a conductive liquid. In laparoscopic procedures, for instance, the abdominal cavity is pressurized with carbon dioxide to provide working space for the instruments and to improve the surgeon&#39;s visibility of the surgical site. Other procedures, such as oral surgery, the ablation and necrosis of diseased tissue, or the ablation of epidermal tissue, are also typically performed in an environment in which the target tissue is not submerged. In such cases, it is necessary to provide a conductive irrigant to the region surrounding the active electrode(s), and frequently also to aspirate debris and liquid from the site. Such irrigant may be applied by a means external to the instrument; however, having an irrigation means internal or attached to the instrument generally provides better control and placement. This is also true for aspiration of fluid and debris. External means may be used for aspiration from the site; however, aspiration through the instrument distal end provides improved fluid control and may, in some cases, draw tissue toward the active electrode thereby enhancing performance. U.S. Pat. No. 7,566,333 to Van Wyk, et al. (herein incorporated by reference in its entirety) discloses an electrosurgical device for use in a dry or semi-dry environment. 
     Electrosurgical devices having means for irrigating a site, and/or means for aspirating fluid, bubbles and debris from a site are well known. Smith, in U.S. Pat. No. 5,195,959, disclose an electrosurgical device with suction and irrigation. Bales, et al., in U.S. Pat. No. 4,682,596 discloses a catheter for electrosurgical removal of plaque buildup in blood vessels, the catheter having lumens for supplying irrigant to the region of the instrument distal tip and for aspirating debris from the region. Hagen, in U.S. Pat. No. 5,277,696 discloses a high frequency coagulation instrument with means for irrigation and aspiration from the region of the instrument tip. Pao, in U.S. Pat. No. 6,674,499, discloses a coaxial bipolar probe with suction and/or irrigation. Eggers, in U.S. Pat. No. 6,066,134, discloses a method for electrosurgical cutting and coagulation that uses a bipolar probe having means for irrigating and aspirating from the region of the probe distal tip. The Eggers device uses the irrigant flow to provide a return path to a return electrode recessed axially a distance away from the active electrode(s). 
     As in the case with ablators operating in a fluid filled cavity, for those operating in a dry or semi-dry environment with supplied irrigant, the placement and volume of aspiration flow through an electrosurgical instrument in the region of an active electrode, or even through the active electrode, may adversely affect the performance of the instrument. Electrosurgery, particularly procedures in which tissue is vaporized, is a thermal process. Aspiration which draws fluid through or around the active electrode surfaces draws away process heat, thereby decreasing heating of the conductive irrigant in the region so as to decrease bubble production and ablative arcing. This makes the device less efficient thereby requiring increased power to achieve acceptable performance. 
     The construction of aspirating ablator distal portions (those distal to the handle) may be divided into two types: complex construction in which power is conducted to the active electrode by wires housed within a tubular distal portion, and simple construction in which the elongated tubular structure conducts power to the active electrode. 
     Aspirating ablation devices with complex construction have a return electrode attached to the probe, the tubular portion conducting RF energy from the return electrode to the handle assembly, from which it is returned to the generator. This tubular return portion must be electrically isolated from the active electrode and wiring within the tubular portion that conducts power to the active electrode. Additionally, the tubular portion must house a dielectric tube for conducting the aspirated materials from the device distal tip to the handle, and therethrough to an external vacuum supply. Aspiration flow must be isolated from the tubular return structure since the conductive liquid contained in the flow is in contact with the active electrode and therefore at high potential. Ablation devices having complex construction are those from Arthrocare, Smith and Nephew, Mitek division of Johnson and Johnson, and Stryker. 
     Aspirating ablation devices with simple construction use a return electrode in the form of a dispersive pad that is removably applied to the patient&#39;s body remote to the surgical site. The distal portion of these device is a metallic tube, to the distal end of which is mounted an active electrode, the RF energy being conducted to the electrode by the tube. Aspirated materials are conducted from the distal tip of the device to the handle, and therethrough to an external vacuum supply. Because the flow is at the same high potential as the tube, it is not necessary to electrically isolate it from the tube. Typical of aspirating ablators having a simple construction are the Lightwave Suction Ablator by Linvatec, and the 9800 series aspirating ablators by Arthrex. 
     Ablators having an ablating surface with a normal perpendicular to that of the device axis (“90 degree ablators”) are the most popular configuration with surgeons, however, ablators are produced in a variety of configurations with the normal to the ablating surface inclined to the axis at angles ranging between thirty and ninety degrees. Ablators having a complex construction are formed to each unique angle using components specific to that geometry. For instance, the distal-end components used to create a 90-degree ablator are configured differently from those used to create a 60-degree ablator, which are different from those used to create a 30-degree ablator. Mitek produces a “VAPR-T Side-Effect ablator” and a “VAPR-T Reverse-angled Side-Effect ablator” from the same components, the tubular element being bent proximal to the distal electrode assembly, however, because of the bend in the tube the ablator cannot be inserted into a standard small-diameter cannula frequently used for fluid control in shoulder and knee surgery. 
     In the case of ablators having simple construction, non-aspirating ablators of various angles of a particular configuration (for example 3.4 mm 30-, 60- and 90-degree) may be constructed using common components. For instance, 30, 60 and 90 degree Ultrablators by Linvatec use a common active electrode component and insulator, the active electrode component being bent to the required angle to create the various products. Similarly, Arthrex 45 and 90 degree small joint and meniscectomy ablators have common active electrode components, the distal ablating surface of the component being beveled at 45 degrees to form the 45-degree ablator. The distal end of the element is bent 45 degrees to create a 90-degree ablator. 
     Prior art aspirating ablators of simple construction (that is, wherein the RF energy is conducted to the active electrode by the elongated tubular distal element) have an active electrode and distal aspiration path formed by an assembly of at least two elements, generally an active electrode element and an element to provide an aspiration path from the aspiration port to the tubular element. This two-piece construction has two associated disadvantages: first, depending on the specific design, the complexity may increase manufacturing difficulty and cost; and second, the complexity may make it difficult to use common components to produce ablators having a range of angular displacement between ablating surface and tube device axis while maintaining a profile that allows use of the device in small diameter cannulas. For instance, Van Wyk in U.S. Pat. No. 6,840,937, Carmel, et al. in co-pending application Ser. No. 11/431,515, teach aspirating ablators with distal electrode assemblies formed from an electrode element and a tubular element for providing an aspiration path, both elements being of a simple, easy to manufacture design that can be produced at low cost. However, if the assembly is bent in such a way that ablators having a range of angles between the surfaces can be formed with the same components, the resulting profile of the bent devices will be such that they cannot pass through small diameter cannulas. Gallo, et al. in co-pending application Ser. Nos. 11/636,548 and 12/639,644 teaches assemblies of complex, difficult to machine components joined by laser welding. While these ablator assemblies can be bent to some degree to produce ablators having a range of angles between the ablating surfaces and the device axis and with the resulting ablators being able to pass through fairly small cannulas, the cost of manufacturing these assemblies is high. 
     There is a need for an aspirating ablator having a simple construction in which the aspiration flow removes primarily waste heat rather than process heat; and which is constructed so that a single component or set of components can be used to produce at low cost ablators of various angles which may be used with small cannulae for arthroscopy, or in a semi-dry environment. 
     SUMMARY OF THE INVENTION 
     It is accordingly an objective of the present invention to provide a highly efficient aspirating electrosurgical ablator capable of overcoming the deficiencies discussed above. More particularly, in view of the ever-present need in the art for improvements in electrode design, it is an objective of the present invention to provide an effective, efficient aspirating ablator that has a simple form, may be produced at low cost and is suited to the bulk vaporization of a wide variety of tissue, in a wide array of environments. To that end, an additional objective of this invention to provide active electrode fabricated as a single machined component that can be flexed into a number of bent positions, to give rise to a range of ablating surface angles (i.e., the angle between the ablating surface and the axis of the ablation device). 
     Thus, in view of the above, the present invention provides an aspirating electrosurgical ablator for bulk vaporization of tissue characterized by a distal end active element of a unitary construction, preferably fabricated from a monolithic piece of homogeneous metallic material. The ablator preferably includes a proximal portion forming a handle, a distal portion that includes the active element and a central lumen extending from the proximal portion to the distal portion, stopping short of the distal end. In a particularly preferred embodiment, the active element is a closed-end tubular element having protuberances, grooves or other contours machined into its distal end to create regions of high current density and yield an angled or beveled ablating surface. The angle of the ablating surface is characterized by the angle a line normal to the ablating surface forms with the longitudinal axis of the distal portion of the tubular element. In a preferred embodiment, this angle ranges between 30 and 80 degrees, and more preferably between 40 and 70 degrees. 
     The active element is further characterized by cannulated lumen, preferably centralized and suited for aspiration extending therethrough and terminating in a lateral opening (aspiration port) positioned just proximal and therefore adjacent to said ablating surface. This novel configuration of lateral aspiration port and beveled, contoured ablation surface permits ablation and vaporization to occur simultaneously, without significantly impacting process heat dispersal and/or negatively affecting ablation efficiency. 
     Accordingly, in a preferred embodiment, the present invention provides an active electrode for connection to an electrosurgical device for the bulk vaporization of tissue, the active electrode including a cannulated tubular element formed from a single piece of homogenous metallic material and characterized by an open proximal end, a closed distal end and a preferably centralized lumen extending therebetween, the active electrode further characterized by: 
     a) a tubular distal portion having a beveled distal-most ablation surface that forms an acute angle with the longitudinal axis of said distal portion, 
     b) a raised flange portion proximally adjacent to the tubular distal portion having a diameter greater than the diameter of the tubular distal portion and a flat distal-facing surface, 
     c) a tubular middle portion proximally adjacent to said flange portion, wherein the tubular middle portion and the tubular distal portion are not coaxial, further wherein the longitudinal axis of the tubular middle portion forms a pre-determined acute angle with the longitudinal axis of said tubular distal portion, 
     d) a tubular proximal portion configured for attachment to an elongate cannulated tubular member, and 
     e) a lateral opening formed in a side wall of the tubular distal portion and positioned proximally to said beveled ablation surface, said opening extending through the side wall of said distal portion into the central lumen. 
     The active electrode of the present invention may be fabricated by any suitable method, including, for example, by metal injection molding as either a single unitary element, or as two sub-elements that are subsequently fused into a single unitary element during sintering. For example, an active metal electrode as described above, including a (a) tubular distal portion of a predetermined length having an angled distal most surface, (b) a flange portion proximally adjacent to the tubular distal portion having a diameter greater than the diameter of said tubular distal portion and having a distal-facing surface, and (c) a tubular proximal-most portion is formed for attachment to an elongated cannulated member, as well as a central lumen extending from the proximal end of said the active electrode to a predetermined depth and terminating in a lateral opening disposed on the exterior surface of said tubular distal portion, may be fabricated by (i) first molding the active metal electrode as a single linear unit and then (ii) bending the tubular middle portion to a pre-determined acute angle such that tubular distal portion and said tubular middle portion are not coaxial. Alternatively, the active metal electrode may be pre-formed in the bent configuration or assembled into a bent configuration from separately molded components. 
     The proximal end of the active electrode piece may be readily affixed to the distal end of the elongate tubular cannula element that constitutes the distal portion of an electrosurgical ablation device. The proximal portion of the ablation device includes a handle that may be, in turn, connected to a suitable vacuum source such that the aperture adjacent and just proximal to the beveled ablating surface, the central lumen of the active electrode piece, and the lumen of the cannula portion together form an aspiration path such that byproducts of ablation may be removed from the region surrounding the distal end of the device during use. 
     The unitary active element piece described above preferably further includes a tubular insulator having open proximal and distal ends and formed from a suitable dielectric material, the insulator configured to slide over and surround the distal end of the electrode. In use, the proximal end of the insulator abuts a raised or flanged, preferably radiused, portion of active element acting as a stop therefore. The distal end of the tubular insulator includes an angled planar surface analogous to and coordinating with the beveled ablation surface disposed on the distal end of the active element. When the insulator is assembled to the active electrode piece, the beveled ablating surface protrudes through the distal portion of the distal opening of the insulator a predetermined distance, and the open proximal end allows communication between the region distal to the insulator and the lateral aperture (i.e., aspiration port) disposed in the electrode piece. The beveled ablating surface is then parallel to the angled distal surface of the insulator. 
     Except for the portion of the electrode piece protruding beyond the insulator distal surface, the electrode piece and elongate tubular member are preferably insulated by a dielectric coating that overlaps the proximal end of the insulator. Additionally, with the exception of the distal insulator component and the proximal cannula component, the remainder of the active electrode component constitutes a unitary, integral construction, preferably fabricated from a homogenous single piece of metallic material. 
     Accordingly, in another preferred embodiment, the present invention provides an electrosurgical device for the bulk vaporization of tissue including an active electrode such as described above, including an elongate cannulated tubular element affixed to the proximal portion of the active electrode and further including a tubular insulator formed from a suitable dielectric material. In a particularly preferred embodiment, the insulator has an open proximal end characterized by a first proximal-most surface and an open distal end characterized by a second distal-most surface, such that when the insulator is positioned about the tubular distal portion of the active electrode, the first proximal-most surface of the insulator abuts the distal-facing surface of the flange portion and the second distal-most surface of the insulator is slightly proximal to the beveled ablation surface of the active electrode such that the lateral opening, the active electrode central lumen, and the cannulated tubular element provide a continuous aspiration path allowing the flow of vaporization by-products from the region adjacent to the beveled ablation surface and to the proximal end of the electrode tubular element. The electrosurgical device may optionally further include a dielectric coating covering the exterior of the tubular element, the portion of the active electrode proximal to said insulator, and a proximal portion of said insulator. 
     The active element preferably includes a portion of reduced wall thickness disposed proximate to the proximal end of the insulator when assembled to the electrode piece, the reduced wall thickness affording flexibility to the active element, permitting it to be bent, the bend occurring primarily in the region of reduced wall thickness. Flexing and bending of the active electrode piece allows the distal end ablating surface to be oriented at a wide range of angles and therefore find utility in connection with a wide variety of electrosurgical products. For instance, bending the element to an angle that is the complement of the angle formed between a line normal to the ablating surface and the axis of the element distal portion in the direction of the aperture (hereinafter referred to as “upward”) the normal to the ablating surface can be made perpendicular to the axis of the tubular element to form what is commonly referred to as a “90 degree ablator”. As an example, if the first ablation surface angle (characterized by a line normal to the ablating surface and the longitudinal tube axis) is 60 degrees, in its unbent state the finished product would be referred to in the industry as a “60 degree ablator”. Converting the active electrode piece to the upward configuration, such that the second angle is 30 degrees would result in the creation of a “90 degree ablator”. Bending the electrode piece downward (away from the aperture) 15 degrees would make the angle between the normal to the ablating face and the tube axis 45 degrees so as to create a “45 degree ablator”. In this fashion, a single unitary piece active element configured for connection to any number of conventional electrosurgical device can be used to produce a variety of ablator products appropriate for a range of tissues and procedures. 
     Because the active electrode piece is bent only moderately to form the various products (generally less than the complement of the first angle), and because the bend is localized at a distal location just proximate to the proximal end of the insulator, the ablators whether unbent or bent, fit into cannulae having relatively small inner diameters. In this manner, insertion trauma may be reduced. 
     Due to its location proximal to the ablating surface, the aspiration port primarily removes waste heat rather than process heat. The aspiration port may be made quite large relative to the size of the ablating surface so as to allow efficient removal of ablation byproducts without clogging. If clogging occurs, the size of the aspirating port and its readily accessible, unobstructed location allow easy clearing of the clogging tissue either by wiping on a suitable surface or by the insertion of a wire into the aspiration port. 
     The aspiration port allows substantial aspiration flow through the electrode piece thereby removing waste heat from the ablation process. Cooling of the electrode piece in this manner prevents failure of the dielectric coating which covers the assembly and also guards against overly high local temperatures which can, in turn, give rise to tissue injury. 
     A final objective of the present invention is to provide a method for forming an active electrode of the present invention, the method including the steps of: [0046] (a) on a screw-machine, lathe or other suitable turning machine, forming a metal blank having a tubular distal portion of a predetermined length, a flange portion having a diameter greater than the diameter of said tubular distal portion and having a distal-facing surface, said flange portion being proximally adjacent to said tubular distal portion, a tubular middle portion proximal to said flange portion, a tubular proximal-most portion formed for attachment to an elongated cannulated member, and a central lumen extending from the proximal end of said active electrode to a predetermined depth; [0047] (b) beveling the distal end of said blank to form an angled distal most surface on said blank; [0048] (c) forming a lateral opening between the exterior surface of said tubular distal portion and the central lumen; and [0049] (d) bending the tubular middle portion a pre-determined acute angle such that tubular distal portion and said tubular middle portion are not coaxial. 
     These and other objects are accomplished in the invention herein disclosed which is an aspirating electrosurgical ablator of simple construction. It will be understood by those skilled in the art that one or more aspects of this invention can meet certain of the above objectives, while one or more other aspects can meet certain other objectives. Each objective may not apply equally, in all its respects, to every aspect of this invention. As such, the preceding objects should be viewed in the alternative with respect to any one aspect of this invention. 
     The above-noted objects and features of the invention will become more fully apparent when the following detailed description is read in conjunction with the accompanying figures and/or examples. However, it is to be understood that both the foregoing summary of the invention and the following detailed description are of a preferred embodiment and not restrictive of the invention or other alternate embodiments of the invention. In particular, while the invention is described herein with reference to a number of specific embodiments, it will be appreciated that the description is illustrative of the invention and is not constructed as limiting of the invention. Various modifications and applications may occur to those who are skilled in the art, without departing from the spirit and the scope of the invention, as described by the appended claims. Likewise, other objects, features, benefits and advantages of the present invention will be apparent from this summary and certain embodiments described below, and will be readily apparent to those skilled in the art having knowledge of electrode design. Such objects, features, benefits and advantages will be apparent from the above in conjunction with the accompanying examples, data, figures and all reasonable inferences to be drawn therefrom, alone or with consideration of the references incorporated herein. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Various aspects and applications of the present invention will become apparent to the skilled artisan upon consideration of the brief description of the figures and the detailed description of the present invention and its preferred embodiments which follows: 
         FIG. 1  is a schematic representation of an electrosurgical system for bulk vaporization of tissue constructed in accordance with the principles of this invention. 
         FIG. 2  depicts an electrosurgical device constructed in accordance with the principles of this invention 
         FIG. 3  is a perspective view of the objects of  FIG. 2 . 
         FIG. 4  is a plan view of the distal portion of a prior art electrosurgical ablator. 
         FIG. 5  is a side elevational view of the objects of  FIG. 1 . 
         FIG. 6  is an axial elevational view of the objects of  FIG. 1 . 
         FIG. 7  is a perspective view of the objects of  FIG. 1 . 
         FIG. 8  is a sectional view of the objects of  FIG. 1  at location A-A of  FIG. 1 . 
         FIG. 9  is a side elevational view of the prior art device objects of  FIG. 1  with the tubular element bent downward. 
         FIG. 10  is an axial elevational view of the objects of  FIG. 6 . 
         FIG. 11  is a plan view of an electrode piece for an electrosurgical ablator formed in accordance with the principles of this invention. 
         FIG. 12  is a side elevational view of the objects of  FIG. 8 . 
         FIG. 13  is a sectional view of the objects of  FIG. 8  at location A-A of  FIG. 8 . 
         FIG. 14  is an axial elevational view of the objects of  FIG. 8 . 
         FIG. 15  is a perspective view of the elements of  FIG. 8 . 
         FIG. 16  is a side elevational view of an insulator for an electrosurgical ablator formed in accordance with the principles of this invention. 
         FIG. 17  is an axial elevational view of the objects of  FIG. 13 . 
         FIG. 18  is a perspective view of the objects of  FIG. 13 . 
         FIG. 19  is a plan view of the distal end assembly of an ablator formed in accordance with the principles of this invention. 
         FIG. 20  is a side elevational view of the objects of  FIG. 16 . 
         FIG. 21  is a sectional view of the objects of  FIG. 16  at location A-A of  FIG. 16 . 
         FIG. 22  is an axial elevational view of the objects of  FIG. 16 . 
         FIG. 23  is a perspective view of the objects of  FIG. 16 . 
         FIG. 24  is a side elevational view of the objects of  FIG. 16  wherein the electrode piece has been bent downward to a predetermined angle. 
         FIG. 25  is an axial elevational view of the objects of  FIG. 21 . 
         FIG. 26  is a plan view of the objects of  FIG. 16  in which the electrode piece has been bent upward to a predetermined angle. 
         FIG. 27  is a side elevational view of the objects of  FIG. 23 . 
         FIG. 28  is a sectional view of the objects of  FIG. 23  at location A-A of  FIG. 23 . 
         FIG. 29  is an axial elevational view of the objects of  FIG. 23 . 
         FIG. 30  is a sectional view of the distal portion of the device during use. 
         FIG. 31  is a plan view of an active electrode for an alternate embodiment of this invention. 
         FIG. 32  is a side elevational view of the objects of  FIG. 31 . 
         FIG. 33  is a side elevational sectional view of the objects of  FIG. 31  at location A-A of  FIG. 31 . 
         FIG. 34  is a distal axial view of the objects of  FIG. 31 . 
         FIG. 35  is a perspective view of the objects of  FIG. 31 . 
         FIG. 36  is a plan view of an insulator for an alternate embodiment of this invention. 
         FIG. 37  is a perspective view of the objects of  FIG. 36 . 
         FIG. 38  is a side elevational view of the objects of  FIG. 36 . 
         FIG. 39  is a distal axial view of the objects of  FIG. 36 . 
         FIG. 40  is a side elevational sectional view of the objects of  FIG. 36  at location A-A of  FIG. 36 . 
         FIG. 41  is a view of the objects of  FIG. 36  in direction A-A of  FIG. 36 . 
         FIG. 42  is a plan view of the distal assembly of an alternate embodiment of the invention herein disclosed. 
         FIG. 43  is a side elevational view of the objects of  FIG. 42 . 
         FIG. 44  is a side elevational sectional view of the objects of  FIG. 42  at location C-C of  FIG. 42 . 
         FIG. 45  is a distal axial view of the objects of  FIG. 42 . 
         FIG. 46  is a perspective view of the objects of  FIG. 42 . 
         FIG. 47  depicts a plan view of an electrode piece of an alternate embodiment formed in accordance with the principles of this invention. 
         FIG. 48  is a side elevational view of the elements of  FIG. 47   
         FIG. 49  is a side elevational sectional view of the elements of  FIG. 47  at location A-A of  FIG. 47 . 
         FIG. 50  is a perspective view of the electrode piece of  FIG. 47  formed upward to create a 90-degree tip. 
         FIG. 51  is a plan of a view of the objects of  FIG. 50 . 
         FIG. 52  is a side elevational view of the objects of  FIG. 50 . 
         FIG. 53  is a side elevational sectional view at location A-A of  FIG. 51 . 
         FIG. 54  is a perspective view of the formed active element of embodiment of  FIG. 50  mounted to a tubular member. 
         FIG. 55  is a plan view of the objects of  FIG. 51 . 
         FIG. 56  is a side elevational view of the objects of  FIG. 51 . 
         FIG. 57  is a side elevational sectional view of the objects of  FIG. 54  at location A-A of  FIG. 55 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention constitutes a marked improvement in the field of electrosurgery, more particularly, to high efficiency surgical devices and methods which use radio frequency (RF) electrical power to vaporize and remove all or part of a tissue mass. 
     Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present invention, the preferred methods, devices, and materials are now described. However, before the present materials and methods are described, it is to be understood that this invention is not limited to the particular compositions, methodologies or protocols herein described, as these may vary in accordance with routine experimentation and optimization. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope of the present invention which will be limited only by the appended claims. 
     Elements of the Present Invention 
     In the context of the present invention, the following definitions apply: 
     The words “a”, “an”, and “the” as used herein mean “at least one” unless otherwise specifically indicated. 
     In common terminology and as used herein, the term “electrode” may refer to one or more components of an electrosurgical device (such as an active electrode or a return electrode) or to the entire device, as in an “ablator electrode” or “cutting electrode”. Such electrosurgical devices are often interchangeably referred to herein as electrosurgical “probes” or “instruments”. 
     The present invention is particularly concerned with the category of electrosurgical instruments referred to in the art as “ablators”, i.e., electrosurgical electrodes designed for the bulk removal of tissue by vaporization rather than the cutting of tissue or coagulation of bleeding vessels. 
     The present invention makes reference to an “active electrode” or “active element”. As used herein, the term “active electrode” refers to one or more conductive elements formed from any suitable metallic material, such as stainless steel, nickel, titanium, tungsten, and the like, connected, for example via cabling disposed within the elongated proximal portion of the instrument, to a power supply, for example, an externally disposed electrosurgical generator, and capable of generating an electric field. 
     The present invention makes reference to a “return electrode”. As used herein, the term “return electrode” refers to one or more powered conductive elements to which current flows after passing from the active electrode(s) back to the electrical RF generator. This return electrode may be located on the ablator device or in close proximity thereto and may be formed from any suitable electrically conductive material, for example a metallic material such as stainless steel, nickel, titanium, tungsten, aluminum and the like. Alternatively, one or more return electrodes, referred to in the art as “dispersive pads” or “return pads”, may be positioned at a remote site on the patient&#39;s body. 
     The present invention makes reference to “fluid(s)”. As used herein, the term “fluid(s)” refers to liquid(s), either electrically conductive or non-conductive, and to gaseous material, or a combination of liquid(s) and gas(es). 
     The term “proximal” refers to that end or portion which is situated closest to the user; in other words, the proximal end of an electrosurgical instrument of the instant invention will typically include the handle portion. 
     The term “distal” refers to that end or portion situated farthest away from the user; in other words, the distal end of an electrosurgical instrument of the instant invention will typically include the active electrode portion. 
     The present invention makes reference to the vaporization of tissue. As used herein, the term “tissue” refers to biological tissues, generally defined as a collection of interconnected cells that perform a similar function within an organism. Four basic types of tissue are found in the bodies of all animals, including the human body and lower multicellular organisms such as insects, including epithelium, connective tissue, muscle tissue, and nervous tissue. These tissues make up all the organs, structures and other body contents. The present invention is not limited in terms of the tissue to be treated but rather has broad application to the vaporization any target tissue with particular applicability to the ablation, destruction and removal of problematic joint tissues. 
     The instant invention has both human medical and veterinary applications. Accordingly, the terms “subject” and “patient” are used interchangeably herein to refer to the person or animal being treated or examined. Exemplary animals include house pets, farm animals, and zoo animals. In a preferred embodiment, the subject is a mammal. 
     Unless otherwise defined, 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. In case of conflict, the present specification, including definitions, will control. 
     Utilities of the Present Invention 
     As noted above, the present invention is directed to high efficiency electrosurgical instruments and methods which utilize radio frequency (RF) energy to vaporize soft tissues, having particular utility in the context of arthroscopy and the removal of problematic joint tissues. However, the invention is not restricted thereto. Aspects are equally applicable to other uses, for example in connection with oncological, ENT, urological, gynecological, and laparascopic procedures, as well as in the context of general surgery. 
     Similarly, while some embodiments utilize the endogenous fluid of a “wet field” environment to transmit current to target sites, others require an exogenous irrigant. In certain embodiments, the “irrigant” (whether native or externally applied) is heated to the boiling point, whereby thermal tissue treatment arises through direct contact with either the boiling liquid itself or steam associated therewith. This thermal treatment may include desiccation to stop bleeding (hemostasis), and/or shrinking, denaturing, or enclosing of tissues for the purpose of volumetric reduction (as in the soft palate to reduce snoring) or to prevent aberrant growth of tissue, for instance, endometrial tissue or malignant tumors. 
     Liquids (either electrically conductive or non conductive) and gaseous irrigants, either singly or in combination may also be advantageously applied to devices for incremental vaporization of tissue. Normal saline solution may be used. Alternatively, the use of low-conductivity irrigants such as water or gaseous irrigants or a combination of the two allows increased control of the ablating environment. 
     The electrosurgical devices of the present invention may be used in conjunction with existing diagnostic and imaging technologies, for example imaging systems including, but not limited to, MRI, CT, PET, x-ray, fluoroscopic, thermographic, photo-acoustic, ultrasonic and gamma camera and ultrasound systems. Such imaging technology may be used to monitor the introduction and operation of the instruments of the present invention. For example, existing imaging systems may be used to determine location of target tissue, to confirm accuracy of instrument positioning, to assess the degree of tissue vaporization (e.g., sufficiency of tissue removal), to determine if subsequent procedures are required (e.g., thermal treatment such as coagulation and/or cauterization of tissue adjacent to the target tissue and/or surgical site), and to assist in the traumatic removal of the device. 
     As noted above, the electrosurgical instruments of the present invention find utility in bulk tissue vaporization. The flexible design permits the distal active end to exhibit a wide array of angled profiles. Certain configurations will have particular utility in the treatment of protruding or projecting tissues while others will be optimized for tissue surface treatment. Accordingly, the present invention is not particularly limited to the treatment of any one specific disease, body part or organ or the removal of any one specific type of tissue, the components and instruments of the present invention. 
     Illustrative Embodiments of the Present Invention 
     Hereinafter, the present invention is described in more detail by reference to the exemplary embodiments. However, the following examples only illustrate aspects of the invention and in no way are intended to limit the scope of the present invention. As such, embodiments similar or equivalent to those described herein can be used in the practice or testing of the present invention. 
     Referring to the figures,  FIG. 1  depicts an electrosurgical system constructed in accordance with the principles of this invention. Ablator electrode  900  is connected by electrical cable  908  to electrosurgical generator  911 , and by tube  920  to an external vacuum source. A return electrode (not shown) is connected to the electrosurgical generator to provide a return path for the RF energy. The return electrode may be a dispersive pad attached to the patient at a site remote from the surgical site, or may be in proximity to the active electrode in contact with tissue or the conductive liquid. 
       FIGS. 2 and 3  further depict the details of electrosurgical instrument  900  constructed in accordance with the principles of this invention. Instrument  900 , also referred to herein as an “ablator”, has a proximal portion  902  forming a handle and an elongated distal portion  904 . Handle  902  has passing from its proximal end  906  electrical cable  908  which is connected to electrosurgical generator  911 , and flexible tube  910  which is connected to tube  920  and thereby to external vacuum source  913 . Near distal end  912  of handle  902 , first activation button  914  labeled “ablate” and second activation button  916  labeled “coagulate”, protrude from top surface  918  of handle  902 . Elongated distal portion  904  has a proximal end  920  that is mounted to distal end  912  of handle  902 , and a distal end  922 . 
     To best understand the principles of this invention, it is necessary to consider a prior art aspirating ablator. The distal portion  100  of a prior art aspirating device is depicted in  FIGS. 4 through 8 . Tube  102  is affixed to active electrode  104  which is affixed to distal end  108  of tubular elongate element  106 , the proximal end  116  of which is assembled to the distal end  110  of tube  112 . Insulator  114  surrounds the upper portion of active electrode  104 . Lumen  120  of tube  102 , lumen  122  of active electrode  104 , lumen  124  of tubular elongate element  106 , and lumen  126  of tube  112  together form an aspiration path for removal of heated fluid, bubbles and debris products of ablation during use, lumen  126  of tube  112  being in communication with a vacuum source. Tube  102  prevents flow of liquid through grooves  130  between ribs  132  thereby minimizing removal of process heat so as to increase the efficiency of the prior art ablator. Distal portion  100  is covered with a suitable dielectric material except for the upper portions of active electrode  104  and insulator  114 . Dotted line  118  is normal to the ablating surface. 
     As shown in  FIGS. 4 through 8 , distal end  100  forms a “90 degree” ablator, a normal  118  to the upper, ablating surface  119  of active electrode  104  being normal to the axis of tubular member  106  and tube  110 .  FIGS. 9 and 10  depict a distal portion  108  of tubular elongate element wherein the distal end is bent, formed downward so that line  118  normal to ablating surface  119  forms an angle  113  with axis  111  of member  106 . Bending in this manner increases the overall height of distal portion  100  to height  115 . 
     A distal-end element (active electrode) for an electrosurgical ablator formed in accordance with the principles of this invention is depicted in  FIGS. 11 through 15 . Active element  200  is formed from a single monolithic metallic material. Active element  200  combines the functions of elongate element  106  and active electrode  104  of prior art assembly  100 , such that proximal end  202  of element  200  is configured for mounting to directly the distal end of a tube. Distal portion  204  has an ablating surface  206  formed thereon, wherein a line  208  normal to ablating surface  206  forms an angle  210  with axis  212  of element  200 . Ablating surface  206  has integral grooves  214  formed therein. A lateral port or opening  206  that intersects lumen  220  of active element  200  is positioned just proximal to ablating surface  206 . Proximal to opening  218 , portion  219  of element  200  has an external diameter of  221 . Middle portion  224  of element  200  has at its distal end flange  226  having a distal surface  228  perpendicular to the device axis  212 , a conical proximal surface  230 , and a radiused edge  232  disposed between the distal and proximal surfaces. Sharpened edges increase the electric field on an RF device. Edge  232  is radiused to minimize intensification of the electric field so as to prevent breakdown of the dielectric coating that will cover the completed assembly. Proximal to flange  226 , middle portion  224  includes cylindrical portion  234  of diameter  236  that extends distance  238 . The proximal end  240  of middle portion  224  has formed thereon a flange  242  having a proximal planar surface  244  to which device axis  212  is normal, and a conical distal surface  246 . Distal to distal surface  246 , cylindrical portion  248  of diameter  250  extends distally to cylindrical portion  234 . Diameter  250  of cylindrical portion  248  is larger than diameter  236  of portion  234  such that bending of element  200  occurs primarily in portion  234 . Portion  234  is fabricated to have a reduced resistance to bending as compared to portion  248 ; for example, portion  234  may be manufactured to have one or more regions of reduced wall thickness. In other embodiments, cylindrical portion  234  of middle portion  224  is eliminated such that middle portion  224  has a constant diameter throughout its entire length. In such embodiments, the length of middle portion  224  is minimized so that bending of portion  224  results in a tight bend radius. Element  200  may be manufactured at low cost using standard machine tools. For instance, a type of lathe commonly referred to as a Swiss-style screw machine may be used to form a cylindrical blank after which a wire electrical discharge machine (wire EDM) may be used to form ablating surface  206 , grooves  214  and lateral opening  218 . 
       FIGS. 16 through 18  depict an insulator for an electrosurgical ablator formed in accordance with the principles of this invention. Insulator  300 , formed from a suitable dielectric material such as, for instance, alumina, is tubular in form having a lumen  301  with a diameter  302  slightly larger than diameter  221  of portion  219  of element  200 , and an outside diameter  304 . Insulator  300  has a proximal end  306  with a planar proximal face having a normal parallel to axis  310  of insulator  300 . Insulator  300  has a distal end  312  forming a planar surface  314  having a normal  316  angularly displaced from axis  310  at angle  318 , angle  318  being approximately equal to angle  210  of element  200 . Lumen  301  intersects surface  314  to form distal opening  320 . 
     Referring to  FIGS. 19 through 23  depicting the distal end assembly  500  of an electrosurgical ablator constructed in accordance with the principles of this invention. Proximal end  202  of active element  200  is mounted to the distal end  402  of tube  400 . Insulator  300  is mounted to distal end  204  of element  200 , proximal face  308  of insulator  300  being adjacent to distal face  228  of flange  226  that acts as a stop for insulator  300 . Lumen  301  of insulator  300  is centered by portion  219  of active element  200  such that the outer cylindrical surface of portion  204  of active element  200  does not contact the inner surface of lumen  301 . Distal face  314  of insulator  300  is parallel to ablating surface  206  and is displaced from ablating surface  206  distance  502 . Tubular member  400  is assembled to proximal end  240  of middle portion  224  of active element  200 , with distal end  402  of member  400  abutting proximal surface  244  of flange  242  of active element  200 . Distal opening  320  and lumen  301 , lumen  220  of element  200 , and lumen  404  of tubular member  400  provide an aspiration path between the region distal to distal surface  314  and a vacuum source connected via means within the handle to lumen  404  of tubular member  400 . A dielectric coating covers assembly  500  proximal to line  510 . 
     Active element  200  may be bent or flexed as needed. For example, active element  200  may be bent downward, to thereby decrease the angle between the axis of the device and the ablating surface. As depicted in  FIGS. 24 and 25 , when active element  200  is bent downward, axis  524  of the distal portion of assembly  500  forms angle  520  with axis  212  of tubular member  400 , the bend being localized in portion  224  of element  200 . Ablating surface  206  forms angle  522  with axis  212  of tubular member  400 , said angle typically being on the order of 30 to 80, more preferably 40 to 70. Bent assembly  500  has an overall height of  515 , said height typically being on the order of 3 mm (0.12 inches) to 8 mm (0.32 inches), more preferably 3 mm (0.12 inches) to 6 mm (0.24 inches). 
     Active element  200  may also be bent upward, to increase the angle between the ablating surface and the axis of the elongate tubular member.  FIGS. 26 through 29  depict distal portion  500  in which region  224  of active element  200  has been bent upward, whereby the axis  524  of distal portion  204  of active element  200  forms angle  520  with axis  212  of the proximal portion of element  200  and tubular element  400 . Angle  520  is the complement of angle  210  ( FIG. 13 ) between line  208  normal to ablating surface  206  and axis  212 . As depicted in  FIG. 28 , normal line  208  may be made perpendicular to axis  212  to convert distal portion  500  into a “90 degree” ablator. Assembly  500 , when formed as shown if  FIGS. 26 through 29 , has an overall height  515 . 
     It will be understood that, as shown in the figures, singly constructed active element  200  may be flexed to a variety of angled positions, characterized by a range of angles formed between the ablating surface and the axis of the tubular portion, so as to permit introduction of assembly  500  into a wide variety of environments and facilitate application to a wide variety of tissues. Because the bend is concentrated in region  224  of electrode element  200 , the overall height  515  is small regardless of the bend. In this manner, the angle will not interfere with or unduly restrict device insertion and manipulation. 
     During use, RF energy is supplied via tubular element  400  to electrode element  200  to ablating surface  206 , which in turn heats the conductive liquid adjacent to and surrounding surface  206 . Heating of the liquid continues until boiling of the liquid occurs at surface  206 , the boiling occurring first around the edges. Bubbles formed at the surface by the boiling grow until they reach a critical size at which arcing through the bubbles occurs. If ablating surface  206  is brought sufficiently close to the tissue, some of the bubbles will intersect the surface of the tissue, and arcing within these bubbles will pass from the ablating surface  206  to the tissue, each arc vaporizing a discreet volume of tissue. Bubbles and debris created by the tissue vaporization process may then be aspirated from the site. 
       FIG. 30  depicts this ablation process using assembly  500  formed as shown in  FIGS. 26 through 29 . Arcs  540  between ablating surface  206  and the tissue vaporize tissue. The ablation by-products and bubbles are removed by the aspiration path provided by aperture  218  and lumen  220  of electrode element  200  and lumen  404  of tubular element  400 . Because the aperture  218  is proximally adjacent to the ablating surface  206  but not does not pass directly through surface  206  or intersect grooves  214  in the ablating surface, the amount of process heat removed is minimized. In this manner, aspiration does not interfere with or significantly decrease the efficiency of the ablating process. 
     An alternate embodiment of a distal end active element for an electrosurgical ablator formed in accordance with the principles of this invention is depicted in  FIGS. 31 through 35 . Active element  600  is identical in form and function to active element  200  except for the placement and configuration of opening  618  compared to opening  218  of active element  200 . Proximal end  602  of active element  600  is configured for mounting to the distal end of a standard electrosurgical shaft or tube. Distal end  604  has an ablating surface  606  formed thereon, wherein a line  608  normal to surface  606  forms an angle  610  with axis  612  of active element  600 . Surface  606  has grooves or contours  614  formed or machined therein. Just proximal to surface  606 , a lateral opening—aspiration port  618 —is disposed, said opening stemming from central lumen  620  of element  600 . Proximal to opening  618  is tubular active element portion  619  having an external diameter of  621 . Continuing in the proximal direction, one finds middle portion  624  of element  600 , a portion having at its distal end flange  626  having a distal surface  628  perpendicular to axis  612 , a conical proximal surface  630 , and a radiused edge  632  disposed between distal and proximal surfaces. Proximal to flange  626  in middle portion  624  is cylindrical portion  634  of diameter  636  and extending distance  638 . The proximal end  640  of middle portion  624  has formed thereon a flange  642  having a proximal planar surface  644  to which axis  612  is normal, and a conical distal surface  646 . Distal to distal surface  646 , cylindrical portion  648  of diameter  650  extends distally to cylindrical portion  634 . Diameter  650  of cylindrical portion  648  is larger than diameter  636  of portion  634 . 
       FIGS. 36 through 41  depict an insulator suitable for use in connection with an alternate embodiment of the present invention. Insulator  700 , formed from a suitable dielectric material such as, for instance, alumina, is tubular in form, has a lumen  701  with a diameter  702  sized to be slightly larger than diameter  621  of portion  619  of element  600 , and a distal portion  703  with an outside diameter  704 . The proximal portion  706  of insulator is characterized by a planar proximal face  708  having a normal parallel to axis  710  of insulator  700 . Proximal portion  706  has a maximum diameter  730 , which is greater than diameter  704  of distal portion  703 , and angled distal and proximal surfaces  732  and  734  respectively. Distal portion  703  has a distal end planar surface  714  having a normal  716  angularly displaced from axis  710  angle  718 , angle  718  being approximately equal to angle  610  of element  600 . Lumen  701  intersects surface  714  to form distal opening  720 . At the proximal end of opening  720 , recess  738  is formed, recess  738  having a proximal wall  740 . 
       FIGS. 42 through 46  depict the distal end assembly  800  of an electrosurgical ablator constructed in accordance with the principles of this invention. Proximal end  602  of active element  600  is mounted to the distal end  402  of tube  400 . Insulator  700  is mounted to distal end  604  of active element  600 , with proximal face  708  of insulator  700  positioned to be adjacent to distal face  628  of flange  626 . Distal face  714  of insulator  700  is parallel to ablating surface  606  and is displaced from ablating surface  606  distance  802 . Recess  738 , opening  618  and lumen  620  of element  600 , and lumen  404  of tubular member  400  together provide an aspiration path between the region distal to distal surface  714  and a vacuum source connected via means within the handle to lumen  404  of tubular member  400 . A dielectric coating covers assembly  500  and tubular member  400  proximal to line  510 . 
     In some cases, it may be advantageous to minimize the diameter of tube  400 , for instance, so that the distal electrode assembly can be incorporated into an ablator having a return electrode on the device. This may be accomplished through elimination of flange  242  ( FIGS. 8 through 12 ) or flange  642  ( FIGS. 31 through 34 ). An alternate embodiment incorporating this configuration is depicted in  FIGS. 47 through 57 . Active element  800  is identical to active element  600  (depicted in  FIGS. 31 through 35 ) and functions in identical manner, with the exception that flange  642  has been eliminated. Proximal end  802  of active element  800  has a reduced diameter such that proximal end  802  may be inserted into distal end  402  of tube  400 . Referring now to  FIGS. 51 through 54  depicting an active element  800  that may mounted to distal end  402  of tube  400 , proximal end  802  of active element  800  may be affixed to distal end  402  of tube  400  by any suitable means, preferably by welding, more preferably by laser welding. Active element  800  functions in the same manner as previous embodiments in that it is machined or molded in a straight (un-bent) condition and may then be formed (bent) at mid-portion  834  to a range of angles so as to produce more than one product. In the Figures, element  800  is bent to form a 90 degree ablator; however, the invention is not limited thereto and may be readily utilized to produce a variety of products each having a different angle between the tube axis and a normal the ablating surface  806 . 
     INDUSTRIAL APPLICABILITY 
     The flexible single piece active element of the present invention, as well as the aspirating ablators formed therewith, find utility in the field of bulk tissue vaporization, providing a simple construction suitable for use with a wide array of electrosurgical components and adjustable to wide range of angled positions to permit access to a variety of tissues, in an array of diverse environments and address a host of ablation needs. 
     Additionally, the novel geometry and positioning of both ablation surface and aspiration port permits aspiration flow to remove primarily waste heat rather than process heat, to thereby improve vaporization efficiency and reduce procedure time. Thus, present invention maximizes efficiency and adaptability while minimizing manufacturing costs and device profile. 
     All patents and publications mentioned herein are incorporated by reference in their entirety. Nothing herein is to be construed as an admission that the invention is not entitled to antedate such disclosure by virtue of prior invention. 
     While the invention has been described in detail and with reference to specific embodiments thereof, it is to be understood that the foregoing description is exemplary and explanatory in nature and is intended to illustrate the invention and its preferred embodiments. Through routine experimentation, one skilled in the art will readily recognize that various changes and modifications can be made therein without departing from the spirit and scope of the invention. 
     Other advantages and features will become apparent from the claims filed hereafter, with the scope of such claims to be determined by their reasonable equivalents, as would be understood by those skilled in the art. Thus, the invention is intended to be defined not by the above description, but by the following claims and their equivalents.