Patent Description:
In many arthroscopic procedures including subacromial decompression, anterior cruciate ligament reconstruction, and resection of the acromioclavicular joint, there is a need for cutting and removing and soft tissue. Currently, surgeons use arthroscopic shavers having rotational cutting surfaces to remove soft tissue in such procedures. <CIT> describes tissue resection devices and methods, for example, for use in resecting and extracting uterine fibroid tissue, polyps and other abnormal uterine tissue.

The need exists for arthroscopic instrument that remove soft tissue rapidly.

In a first aspect, there is provided an electrosurgical probe as set out in claim <NUM>.

Various embodiments of the present disclosure will now be discussed with reference to the appended drawings. It should be appreciated that the drawings depict only typical embodiments of the disclosure and are therefore not to be considered limiting in scope.

The present disclosure relates to devices for cutting, ablating and removing bone and soft tissue. Several variations of the disclosure will now be described to provide an overall understanding of the principles of the form, function and methods of use of the devices disclosed herein. In one variation, the present disclosure provides for an arthroscopic cutter or burr assembly for cutting or abrading bone that is disposable and is configured for detachable coupling to a non-disposable handle and motor drive component. This description of the general principles of this disclosure is not meant to limit the inventive concepts in the appended claims. The embodiment shown in <FIG> is covered by the claimed subject-matter. Other disclosed described embodiments which do not include all features of independent claim <NUM> are not covered by the claimed subject-matter. Any disclosed methods for treatment of the human or animal body by surgery are provided to illustrate the functioning of the disclosed devices - the claimed subject-matter is directed to a device (specifically an electrosurgical probe).

In general, one embodiment provides a high-speed rotating ceramic cutter or burr that is configured for use in many arthroscopic surgical applications, including but not limited to treating bone in shoulders, knees, hips, wrists, ankles and the spine. More in particular, the device includes a cutting member that is fabricated entirely of a ceramic material that is extremely hard and durable, as described in detail below. A motor drive is operatively coupled to the ceramic cutter to rotate the burr edges at speeds ranging from <NUM>,<NUM> RPM to <NUM>,<NUM> RPM.

In one variation shown in <FIG>, an arthroscopic cutter or burr assembly <NUM> is provided for cutting and removing hard tissue, which operates in a manner similar to commercially available metals shavers and burrs. <FIG> shows disposable burr assembly <NUM> that is adapted for detachable coupling to a handle <NUM> and motor drive unit <NUM> therein as shown in <FIG>.

The cutter assembly <NUM> has a shaft <NUM> extending along longitudinal axis <NUM> that comprises an outer sleeve <NUM> and an inner sleeve <NUM> rotatably disposed therein with the inner sleeve <NUM> carrying a distal ceramic cutting member <NUM>. The shaft <NUM> extends from a proximal hub assembly <NUM> wherein the outer sleeve <NUM> is coupled in a fixed manner to an outer hub 140A which can be an injection molded plastic, for example, with the outer sleeve <NUM> insert molded therein. The inner sleeve <NUM> is coupled to an inner hub 140B (phantom view) that is configured for coupling to the motor drive unit <NUM> (<FIG>). The outer and inner sleeves <NUM> ands <NUM> typically can be a thin wall stainless steel tube, but other materials can be used such as ceramics, metals, plastics or combinations thereof.

Referring to <FIG>, the outer sleeve <NUM> extends to distal sleeve region <NUM> that has an open end and cut-out <NUM> that is adapted to expose a window <NUM> in the ceramic cutting member <NUM> during a portion of the inner sleeve's rotation. Referring to <FIG> and <FIG>, the proximal hub <NUM> of the burr assembly <NUM> is configured with a J-lock, snap-fit feature, screw thread or other suitable feature for detachably locking the hub assembly <NUM> into the handle <NUM>. As can be seen in <FIG>, the outer hub 140A includes a projecting key <NUM> that is adapted to mate with a receiving J-lock slot <NUM> in the handle <NUM> (see <FIG>).

In <FIG>, it can be seen that the handle <NUM> is operatively coupled by electrical cable <NUM> to a controller <NUM> which controls the motor drive unit <NUM>. Actuator buttons 156a, 156b or 156c on the handle <NUM> can be used to select operating modes, such as various rotational modes for the ceramic cutting member. In one variation, a joystick <NUM> be moved forward and backward to adjust the rotational speed of the ceramic cutting member <NUM>. The rotational speed of the cutter can continuously adjustable, or can be adjusted in increments up to <NUM>,<NUM> RPM. <FIG> further shows that negative pressure source <NUM> is coupled to aspiration tubing <NUM> which communicates with a flow channel in the handle <NUM> and lumen <NUM> in inner sleeve <NUM> which extends to window <NUM> in the ceramic cutting member <NUM> (<FIG>).

Now referring to <FIG> and <FIG>, the cutting member <NUM> comprises a ceramic body or monolith that is fabricated entirely of a technical ceramic material that has a very high hardness rating and a high fracture toughness rating, where "hardness" is measured on a Vickers scale and "fracture toughness" is measured in MPam<NUM>/<NUM>. Fracture toughness refers to a property which describes the ability of a material containing a flaw or crack to resist further fracture and expresses a material's resistance to brittle fracture. The occurrence of flaws is not completely avoidable in the fabrication and processing of any components.

The authors evaluated technical ceramic materials and tested prototypes to determine which ceramics are best suited for the non-metal cutting member <NUM>. When comparing the material hardness of the ceramic cutters of the disclosure to prior art metal cutters, it can easily be understood why typical stainless steel bone burrs are not optimal. Types <NUM> and <NUM> stainless steel have hardness ratings of <NUM> and <NUM>, respectively, which is low and a fracture toughness ratings of <NUM> and <NUM>, respectively, which is very high. Human bone has a hardness rating of <NUM>, so a stainless steel cutter is only about <NUM> times harder than bone. The high fracture toughness of stainless steel provides ductile behavior which results in rapid cleaving and wear on sharp edges of a stainless steel cutting member. In contrast, technical ceramic materials have a hardness ranging from approximately <NUM> to <NUM>, which is five to six times greater than stainless steel and which is <NUM> to <NUM> times harder than cortical bone. As a result, the sharp cutting edges of a ceramic remain sharp and will not become dull when cutting bone. The fracture toughness of suitable ceramics ranges from about <NUM> to <NUM> which is sufficient to prevent any fracturing or chipping of the ceramic cutting edges. The authors determined that a hardness-to-fracture toughness ratio ("hardness-toughness ratio") is a useful term for characterizing ceramic materials that are suitable for the disclosure as can be understood form the Chart A below, which lists hardness and fracture toughness of cortical bone, a <NUM> stainless steel, and several technical ceramic materials.

As can be seen in Chart A, the hardness-toughness ratio for the listed ceramic materials ranges from 98X to 250X greater than the hardness-toughness ratio for stainless steel <NUM>. In one aspect of the disclosure, a ceramic cutter for cutting hard tissue is provided that has a hardness-toughness ratio of at least <NUM>:<NUM>, <NUM>:<NUM> or <NUM>:<NUM>.

In one variation, the ceramic cutting member <NUM> is a form of zirconia. Zirconia-based ceramics have been widely used in dentistry and such materials were derived from structural ceramics used in aerospace and military armor. Such ceramics were modified to meet the additional requirements of biocompatibility and are doped with stabilizers to achieve high strength and fracture toughness. The types of ceramics used in the current disclosure have been used in dental implants, and technical details of such zirconia-based ceramics can be found in <NPL>).

In one variation, the ceramic cutting member <NUM> is fabricated of an yttria-stabilized zirconia as is known in the field of technical ceramics, and can be provided by CoorsTek Inc. , <NUM> Table Mountain Pkwy. , Golden, CO <NUM> or Superior Technical Ceramics Corp. , <NUM> Industrial Park Rd. Albans City, VT <NUM>. Other technical ceramics that may be used consist of magnesia-stabilized zirconia, ceria-stabilized zirconia, zirconia toughened alumina and silicon nitride. In general, in one aspect of the disclosure, the monolithic ceramic cutting member <NUM> has a hardness rating of at least <NUM> Gpa (kg/mm<NUM>). In another aspect of the disclosure, the ceramic cutting member <NUM> has a fracture toughness of at least <NUM> MPam<NUM>/<NUM>.

The fabrication of such ceramics or monoblock components are known in the art of technical ceramics, but have not been used in the field of arthroscopic or endoscopic cutting or resecting devices. Ceramic part fabrication includes molding, sintering and then heating the molded part at high temperatures over precise time intervals to transform a compressed ceramic powder into a ceramic monoblock which can provide the hardness range and fracture toughness range as described above. In one variation, the molded ceramic member part can have additional strengthening through hot isostatic pressing of the part. Following the ceramic fabrication process, a subsequent grinding process optionally may be used to sharpen the cutting edges <NUM> of the burr (see <FIG> and <FIG>).

In <FIG>, it can be seen that in one variation, the proximal shaft portion <NUM> of cutting member <NUM> includes projecting elements <NUM> which are engaged by receiving openings <NUM> in a stainless steel split collar <NUM> shown in phantom view. The split collar <NUM> can be attached around the shaft portion <NUM> and projecting elements <NUM> and then laser welded along weld line <NUM>. Thereafter, proximal end <NUM> of collar <NUM> can be laser welded to the distal end <NUM> of stainless steel inner sleeve <NUM> to mechanically couple the ceramic body <NUM> to the metal inner sleeve <NUM>. In another aspect of the disclosure, the ceramic material is selected to have a coefficient of thermal expansion between is less than <NUM> (<NUM> × <NUM><NUM>/ °C) which can be close enough to the coefficient of thermal expansion of the metal sleeve <NUM> so that thermal stresses will be reduced in the mechanical coupling of the ceramic member <NUM> and sleeve <NUM> as just described. In another variation, a ceramic cutting member can be coupled to metal sleeve <NUM> by brazing, adhesives, threads or a combination thereof.

Referring to <FIG> and <FIG>, the ceramic cutting member <NUM> has window <NUM> therein which can extend over a radial angle of about <NUM>° to <NUM>° of the cutting member's shaft. In the variation of <FIG>, the window is positioned proximally to the cutting edges <NUM>, but in other variations, one or more windows or openings can be provided and such openings can extend in the flutes <NUM> (see <FIG>) intermediate the cutting edges <NUM> or around a rounded distal nose of the ceramic cutting member <NUM>. The length L of window <NUM> can range from <NUM> to <NUM> depending on the diameter and design of the ceramic member <NUM>, with a width W of <NUM> to <NUM>.

<FIG> and <FIG> shows the ceramic burr or cutting member <NUM> with a plurality of sharp cutting edges <NUM> which can extend helically, axially, longitudinally or in a cross-hatched configuration around the cutting member, or any combination thereof. The number of cutting edges <NUM> ands intermediate flutes <NUM> can range from <NUM> to <NUM> with a flute depth ranging from <NUM> to <NUM>. In the variation shown in <FIG> and <FIG>, the outer surface or periphery of the cutting edges <NUM> is cylindrical, but such a surface or periphery can be angled relative to axis <NUM> or rounded as shown in <FIG> and <FIG>. The axial length AL of the cutting edges can range between <NUM> and <NUM>. While the cutting edges <NUM> as depicted in <FIG> are configured for optimal bone cutting or abrading in a single direction of rotation, it should be appreciated the that the controller <NUM> and motor drive <NUM> can be adapted to rotate the ceramic cutting member <NUM> in either rotational direction, or oscillate the cutting member back and forth in opposing rotational directions.

<FIG> illustrate a sectional view of the window <NUM> and shaft portion <NUM> of a ceramic cutting member <NUM>' that is very similar to the ceramic member <NUM> of <FIG> and <FIG>. In this variation, the ceramic cutting member has window <NUM> with one or both lateral sides configured with sharp cutting edges 202a and 202b which are adapted to resect tissue when rotated or oscillated within close proximity, or in scissor-like contact with, the lateral edges 204a and 204b of the sleeve walls in the cut-out portion <NUM> of the distal end of outer sleeve <NUM> (see <FIG>). Thus, in general, the sharp edges of window <NUM> can function as a cutter or shaver for resecting soft tissue rather than hard tissue or bone. In this variation, there is effectively no open gap G between the sharp edges 202a and 202b of the ceramic cutting member <NUM>' and the sharp lateral edges 204a, 204b of the sleeve <NUM>. In another variation, the gap G between the window cutting edges 202a, 202b and the sleeve edges 204a, 204b is less than about <NUM>", or less than <NUM>".

<FIG> illustrates another variation of ceramic cutting member <NUM> coupled to an inner sleeve <NUM> in phantom view. The ceramic cutting member again has a plurality of sharp cutting edges <NUM> and flutes <NUM> therebetween. The outer sleeve <NUM> and its distal opening and cut-out shape <NUM> are also shown in phantom view. In this variation, a plurality of windows or opening <NUM> are formed within the flutes <NUM> and communicate with the interior aspiration channel <NUM> in the ceramic member as described previously.

<FIG> illustrates another variation of ceramic cutting member <NUM> coupled to an inner sleeve <NUM> (phantom view) with the outer sleeve not shown. The ceramic cutting member <NUM> is very similar to the ceramic cutter <NUM> of <FIG>, <FIG> and <FIG>, and again has a plurality of sharp cutting edges <NUM> and flutes <NUM> therebetween. In this variation, a plurality of windows or opening <NUM> are formed in the flutes <NUM> intermediate the cutting edges <NUM> and another window <NUM> is provided in a shaft portion <NUM> of ceramic member <NUM> as described previously. The openings <NUM> and window <NUM> communicate with the interior aspiration channel <NUM> in the ceramic member as described above.

It can be understood that the ceramic cutting members can eliminate the possibility of leaving metal particles in a treatment site. In one aspect of the disclosure, a method of preventing foreign particle induced inflammation in a bone treatment site comprises providing a rotatable cutter fabricated of a ceramic material having a hardness of at least <NUM> Gpa (kg/mm<NUM>) and/or a fracture toughness of at least <NUM> MPam<NUM>/<NUM> and rotating the cutter to cut bone without leaving any foreign particles in the treatment site. The method includes removing the cut bone tissue from the treatment site through an aspiration channel in a cutting assembly.

<FIG> illustrates variation of an outer sleeve assembly with the rotating ceramic cutter and inner sleeve not shown. In the previous variations, such as in <FIG>, <FIG> and <FIG>, shaft portion <NUM> of the ceramic cutter <NUM> rotates in a metal outer sleeve <NUM>. <FIG> illustrates another variation in which a ceramic cutter (not shown) would rotate in a ceramic housing <NUM>. In this variation, the shaft or a ceramic cutter would thus rotate is a similar ceramic body which may be advantageous when operating a ceramic cutter at high rotational speeds. As can be seen in <FIG>, a metal distal metal housing <NUM> is welded to the outer sleeve <NUM> along weld line <NUM>. The distal metal housing <NUM> is shaped to support and provide strength to the inner ceramic housing <NUM>.

<FIG> are views of an alternative tissue resecting assembly or working end <NUM> that includes a ceramic member <NUM> with cutting edges <NUM> in a form similar to that described previously. <FIG> illustrates the monolithic ceramic member <NUM> carried as a distal tip of a shaft or inner sleeve <NUM> as described in previous embodiments. The ceramic member <NUM> again has a window <NUM> that communicates with aspiration channel <NUM> in shaft <NUM> that is connected to negative pressure source <NUM> as described previously. The inner sleeve <NUM> is operatively coupled to a motor drive <NUM> and rotates in an outer sleeve <NUM> of the type shown in <FIG>. The outer sleeve <NUM> is shown in <FIG>.

In the variation illustrated in <FIG>, the ceramic member <NUM> carries an electrode arrangement <NUM>, or active electrode, having a single polarity that is operatively connected to an RF source <NUM>. A return electrode, or second polarity electrode <NUM>, is provided on the outer sleeve <NUM> as shown in <FIG>. In one variation, the outer sleeve <NUM> can comprise an electrically conductive material such as stainless steel to thereby function as return electrode <NUM>, with a distal portion of outer sleeve <NUM> is optionally covered by a thin insulative layer <NUM> such as parylene, to space apart the active electrode <NUM> from the return electrode <NUM>.

The active electrode arrangement <NUM> can consist of a single conductive metal element or a plurality of metal elements as shown in <FIG> and <FIG>. In one variation shown in <FIG>, the plurality of electrode elements 450a, 450b and 450c extend transverse to the longitudinal axis <NUM> of ceramic member <NUM> and inner sleeve <NUM> and are slightly spaced apart in the ceramic member. In one variation shown in <FIG> and <FIG>, the active electrode <NUM> is spaced distance D from the distal edge <NUM> of window <NUM> which is less than <NUM> and often less than <NUM> for reasons described below. The width W and length L of window <NUM> can be the same as described in a previous embodiment with reference to <FIG>.

As can be seen in <FIG> and <FIG>, the electrode arrangement <NUM> is carried intermediate the cutting edges <NUM> of the ceramic member <NUM> in a flattened region <NUM> where the cutting edges <NUM> have been removed. As can be best understood from <FIG>, the outer periphery <NUM> of active electrode <NUM> is within the cylindrical or rotational periphery of the cutting edges <NUM> when they rotate. In <FIG>, the rotational periphery of the cutting edges is indicated at <NUM>. The purpose of the electrode's outer periphery <NUM> being equal to, or inward from, the cutting edge periphery <NUM> during rotation is to allow the cutting edges <NUM> to rotate at high RPMs to engage and cut bone or other hard tissue without the surface or the electrode <NUM> contacting the targeted tissue.

<FIG> further illustrates a method of fabricating the ceramic member <NUM> with the electrode arrangement <NUM> carried therein. The molded ceramic member <NUM> is fabricated with slots <NUM> that receive the electrode elements 450a-450c, with the electrode elements fabricated from stainless steel, tungsten or a similar conductive material. Each electrode element 450a-450c has a bore <NUM> extending therethrough for receiving an elongated wire electrode element <NUM>. As can be seen in <FIG>, and the elongated wire electrode <NUM> can be inserted from the distal end of the ceramic member <NUM> through a channel in the ceramic member <NUM> and through the bores <NUM> in the electrode elements 450a-450c. The wire electrode <NUM> can extend through the shaft <NUM> and is coupled to the RF source <NUM>. The wire electrode element <NUM> thus can be used as a means of mechanically locking the electrode elements 450a-450c in slots <NUM> and also as a means to deliver RF energy to the electrode <NUM>.

Another aspect of the disclosure is illustrated in <FIG> wherein it can be seen that the electrode arrangement <NUM> has a transverse dimension TD relative to axis <NUM> that is substantial in comparison to the window width W as depicted in <FIG>. In one variation, the electrode's transverse dimension TD is at least <NUM>% of the window width W, or the transverse dimension TD is at least <NUM>% of the window width W. In the variation of <FIG>, the electrode transverse dimension TD is <NUM>% or more of the window width W. It has been found that tissue debris and byproducts from RF ablation are better captured and extracted by a window <NUM> that is wide when compared to the width of the RF plasma ablation being performed.

In general, the tissue resecting system comprises an elongated shaft with a distal tip comprising a ceramic member, a window in the ceramic member connected to an interior channel in the shaft and an electrode arrangement in the ceramic member positioned distal to the window and having a width that is at <NUM>% of the width of the window, at <NUM>% of the width of the window or at <NUM>% of the width of the window. Further, the system includes a negative pressure source <NUM> in communication with the interior channel <NUM>.

Now turning to <FIG>, a method of use of the resecting assembly <NUM> of <FIG> can be explained. In <FIG>, the system and a controller is operated to stop rotation of the ceramic member <NUM> in a selected position were the window <NUM> is exposed in the cut-out <NUM> of the open end of outer sleeve <NUM> shown in phantom view. In one variation, a controller algorithm can be adapted to stop the rotation of the ceramic <NUM> that uses a Hall sensor 484a in the handle <NUM> (see <FIG>) that senses the rotation of a magnet 484b carried by inner sleeve hub 140B as shown in <FIG>. The controller algorithm can receive signals from the Hall sensor which indicated the rotational position of the inner sleeve <NUM> and ceramic member relative to the outer sleeve <NUM>. The magnet 484b can be positioned in the hub 140B (<FIG>) so that when sensed by the Hall sensor, the controller algorithm can de-activate the motor drive <NUM> so as to stop the rotation of the inner sleeve in the selected position.

Under endoscopic vision, referring to <FIG>, the physician then can position the electrode arrangement <NUM> in contact with tissue targeted T for ablation and removal in a working space filled with fluid <NUM>, such as a saline solution which enables RF plasma creation about the electrode. The negative pressure source <NUM> is activated prior to or contemporaneously with the step of delivering RF energy to electrode <NUM>. Still referring to <FIG>, when the ceramic member <NUM> is positioned in contact with tissue and translated in the direction of arrow Z, the negative pressure source <NUM> suctions the targeted tissue into the window <NUM>. At the same time, RF energy delivered to electrode arrangement <NUM> creates a plasma P as is known in the art to thereby ablate tissue. The ablation then will be very close to the window <NUM> so that tissue debris, fragments, detritus and byproducts will be aspirated along with fluid <NUM> through the window <NUM> and outwardly through the interior extraction channel <NUM> to a collection reservoir. In one method shown schematically in <FIG>, a light movement or translation of electrode arrangement <NUM> over the targeted tissue will ablate a surface layer of the tissue and aspirate away the tissue detritus.

<FIG> schematically illustrates a variation of a method which is of particular interest. It has been found if suitable downward pressure on the working end <NUM> is provided, then axial translation of working end <NUM> in the direction arrow Z in <FIG>, together with suitable negative pressure and the RF energy delivery will cause the plasma P to undercut the targeted tissue along line L that is suctioned into window <NUM> and then cut and scoop out a tissue chips indicated at <NUM>. In effect, the working end <NUM> then can function more as a high volume tissue resecting device instead of, or in addition to, its ability to function as a surface ablation tool. In this method, the cutting or scooping of such tissue chips <NUM> would allow the chips to be entrained in outflows of fluid <NUM> and aspirated through the extraction channel <NUM>. It has been found that this system with an outer shaft diameter of <NUM>, can perform a method of the disclosure can ablate, resect and remove tissue greater than <NUM> grams/min, greater than <NUM> grams/min, and greater than <NUM> grams/min.

In general, a method corresponding to the disclosure includes providing an elongated shaft with a working end <NUM> comprising an active electrode <NUM> carried adjacent to a window <NUM> that opens to an interior channel in the shaft which is connected to a negative pressure source, positioning the active electrode and window in contact with targeted tissue in a fluidfilled space, activating the negative pressure source to thereby suction targeted tissue into the window and delivering RF energy to the active electrode to ablate tissue while translating the working end across the targeted tissue. The method further comprises aspirating tissue debris through the interior channel <NUM>. In a method, the working end <NUM> is translated to remove a surface portion of the targeted tissue. In a variation of the method, the working end <NUM> is translated to undercut the targeted tissue to thereby remove chips <NUM> of tissue.

Now turning to <FIG>, other distal ceramic tips of cutting assemblies are illustrated that are similar to that of <FIG>, except the electrode configurations carried by the ceramic members <NUM> are varied. In <FIG>, the electrode 490A comprises one or more electrode elements extending generally axially distally from the window <NUM>. <FIG> illustrates an electrode 490B that comprises a plurality of wire-like elements <NUM> projecting outwardly from surface <NUM>. <FIG> shows electrode 490C that comprises a ring-like element that is partly recessed in a groove <NUM> in the ceramic body. All of these variations can produce an RF plasma that is effective for surface ablation of tissue, and are positioned adjacent to window <NUM> to allow aspiration of tissue detritus from the site.

<FIG> illustrates another variation of a distal ceramic tip <NUM> of an inner sleeve <NUM> that is similar to that of <FIG> except that the window <NUM> has a distal portion <NUM> that extends distally between the cutting edges <NUM>, which is useful for aspirating tissue debris cut by high speed rotation of the cutting edges <NUM>. Further, in the variation of <FIG>, the electrode <NUM> encircles a distal portion <NUM> of window <NUM> which may be useful for removing tissue debris that is ablated by the electrode when the ceramic tip <NUM> is not rotated but translated over the targeted tissue as described above in relation to <FIG>. In another variation, a distal tip <NUM> as shown in <FIG> can be energized for RF ablation at the same time that the motor drive rotates back and forth (or oscillates) the ceramic member <NUM> in a radial arc ranging from <NUM>° to <NUM>° and more often from <NUM>° to <NUM>°.

<FIG> illustrate other distal ceramic tips <NUM> and <NUM>' that are similar to that of <FIG> except the electrode configurations differ. In <FIG>, the window <NUM> has a distal portion <NUM> that again extends distally between the cutting edges <NUM>, with electrode <NUM> comprising a plurality of projecting electrode elements that extend partly around the window <NUM>. <FIG> shows a ceramic tip <NUM>' with window <NUM> having a distal portion <NUM> that again extends distally between the cutting edges <NUM>. In this variation, the electrode <NUM> comprises a single blade element that extends transverse to axis <NUM> and is in close proximity to the distal end <NUM> of window <NUM>.

<FIG> illustrates another variation of distal ceramic tip <NUM> of an inner sleeve <NUM> that is configured without the sharp cutting edges <NUM> of the embodiment of <FIG>. In other respects, the arrangement of the window <NUM> and the electrode <NUM> is the same as described previously. Further, the outer periphery of the electrode is similar to the outward surface of the ceramic tip <NUM>. In the variation of <FIG>, the window <NUM> has at least one sharp edge <NUM> for cutting soft tissue when the assembly is rotated at a suitable speed from <NUM> to <NUM>,<NUM> RPM. When the ceramic tip member <NUM> is maintained in a stationary position and translated over targeted tissue, the electrode <NUM> can be used to ablate surface layers of tissue as described above.

<FIG> depicts another variation of distal ceramic tip <NUM> coupled to an inner sleeve <NUM> that again has sharp burr edges or cutting edges <NUM> as in the embodiment of <FIG>. In this variation, the ceramic monolith has only <NUM> sharp edges <NUM> which has been found to work well for cutting bone at high RPMs, for example from <NUM>,<NUM> RPM to <NUM>,<NUM> RPM. In this variation, the arrangement of window <NUM> and electrode <NUM> is the same as described previously. Again, the outer periphery of electrode <NUM> is similar to the outward surface of the cutting edges <NUM>.

<FIG> illustrate another electrosurgical RF ablation device or probe <NUM> (<FIG>) that is adapted for use with a handpiece <NUM> and motor drive unit <NUM> (see <FIG>). In <FIG>, the console <NUM> carries RF source 705A and a negative pressure source 705B which can comprise a peristaltic pump and cassette to provide suction though tubing <NUM> coupled to the handpiece <NUM> as is known in the art. The console <NUM> further can carry a controller 705C that operates the motor drive as well as actuation and/or modulation of the RF source 705A and negative pressure source 705B. A footswitch 707a is provided for operation of RF source 705A, negative pressure source 705B and optionally the motor drive. In addition, the motor drive <NUM>, RF source and negative pressure source can be operated by control buttons 707b in the handpiece <NUM> (<FIG>). In the RF probe of <FIG>, the motor drive <NUM> does not rotate a cutting blade or electrode but instead moves or reciprocates an RF electrode axially at a selected reciprocation rate (which may be a high or low reciprocation rate or a single reciprocation) to dynamically ablate, resect and remove tissue.

More in particular, referring to <FIG>, the detachable RF ablation probe <NUM> has a proximal housing portion or hub <NUM> that is coupled to an elongated shaft or extension portion <NUM> that has an outer diameter ranging from about <NUM> to <NUM>, and in one variation is from <NUM> to <NUM> in diameter. The shaft <NUM> extends about longitudinal axis <NUM> to a working end housing or body <NUM> that comprises a dielectric material such as a ceramic as described above. Referring to <FIG>, <FIG> and <FIG>, it can be seen that elongated shaft <NUM> comprises an outer sleeve <NUM> and an inner sleeve <NUM>. Both sleeves <NUM> and <NUM> can be a thin wall stainless steel tube or another similar material or composite that is electrically conductive. The outer sleeve <NUM> has a distal end <NUM> that is coupled to the ceramic housing <NUM> and an interior channel <NUM> extending through the housing <NUM> to a distal channel opening <NUM> in housing <NUM>. In this variation, the channel opening <NUM> in part faces sideways or laterally in the housing <NUM> relative to axis <NUM> and also faces in the distal direction.

Referring to <FIG>, a moveable active electrode <NUM> is configured to extend laterally across a window <NUM> which has a planar surface and is a section of opening <NUM> in housing <NUM>. As can be seen in FIS. 20A-20B, the electrode <NUM> is carried at the distal end of reciprocating inner sleeve <NUM>. The electrode <NUM> is adapted to be driven by motor drive unit <NUM> in handpiece <NUM> (see <FIG>) so that proximal-facing edge 728a and side-facing edges 728b of electrode <NUM> move axially relative to the window <NUM>. <FIG> and the corresponding sectional view of <FIG> show the inner sleeve <NUM> and electrode <NUM> moved by motor drive <NUM> to an extended or distal axial position relative to window <NUM>. <FIG> and <FIG> show the inner sleeve <NUM> and electrode <NUM> moved by the motor drive to a non-extended or retracted position relative to window <NUM>. In <FIG> and <FIG>, the window <NUM> has an open window length WL that can be defined as the dimension between the proximal window edge <NUM> and the proximal-facing electrode edge <NUM>. The stroke AA of the moving electrode <NUM> is also shown in <FIG> wherein the electrode edge 728a in the retracted position (<FIG> and <FIG>) is adapted to extend over the proximal window edge <NUM> to shear tissue and clean the electrode surface. Likewise, referring to <FIG>, the side-facing edges 728b of electrode <NUM> extend over the lateral edges <NUM> of window <NUM> to shear tissue engaged by suction in the window.

As can be seen in <FIG>, the inner sleeve <NUM> comprises a thin-wall tube of stainless steel or another conductive material, and is coupled to RF source 705A (<FIG>) to carry RF current to the electrode <NUM>. The inner sleeve <NUM> has a distal end <NUM> that coupled by a weld to a conductive metal rod or element <NUM> that extends transversely through a dielectric body <NUM> carried by the inner sleeve. The conductive element <NUM> is welded to electrode <NUM> that extends laterally across the window <NUM>. The dielectric body <NUM> can be a ceramic, polymer or combination thereof and is in part configured to provide an insulator layer around to electrical conductive components (inner sleeve <NUM> and transverse rod <NUM>) to define the "active electrode" as the limited surface area of electrode <NUM> which enhances RF energy delivery to the electrode edges 728a and 728b for tissue cutting. The inner sleeve <NUM> also has side-facing window <NUM> therein that cooperates with window <NUM> in housing <NUM> to provide suction through the windows <NUM> and <NUM> from negative pressure source 705B (see <FIG> and <FIG>) to draw tissue into the window <NUM>.

Now turning to <FIG>, <FIG>, <FIG> and <FIG>, the mechanism that axially translates the electrode <NUM> in window <NUM> is described in more detail. As can be understood from <FIG>, <FIG> and <FIG>, the RF ablation probe <NUM> can be locked into handpiece <NUM> of <FIG> by inserting tabs 737a and 737b on flex arms 738a and 738b (<FIG> and <FIG>) into receiving openings 740a and 740b in handpiece <NUM> (<FIG>). O-rings 742a and 742b are provided in hub <NUM> (<FIG>) to seal the hub <NUM> into the receiving channel <NUM> in the handpiece <NUM> (<FIG>).

Referring now to <FIG>, the hub <NUM> is fixed to outer sleeve <NUM> that has a bore or channel <NUM> therein in which the inner sleeve <NUM> is slidably disposed. A proximal end <NUM> of inner sleeve <NUM> has an actuator collar <NUM> of an electrically conductive material attached thereto with a proximal-facing surface <NUM> that has a bump or cam surface <NUM> thereon. The actuator collar <NUM> is adapted to reciprocate within bore <NUM> in the hub <NUM>. <FIG> shows the actuator collar <NUM> in an extended position which corresponds to the extended electrode position of <FIG> and <FIG>. <FIG> shows the actuator collar <NUM> in a non-extended or retracted position which corresponds to the retracted electrode position of <FIG> and <FIG>.

The actuator collar <NUM> and hub <NUM> include slot and key features described further below to allow for axial reciprocation of the sliding actuator collar <NUM> and inner sleeve <NUM> while preventing rotation of the collar <NUM> and sleeve <NUM>. A spring <NUM> between a distal surface <NUM> of actuator collar <NUM> and a proximally facing internal surface <NUM> of hub <NUM> urges the sliding actuator collar <NUM> and the moveable active electrode <NUM> toward the retracted or proximal-most position as shown in <FIG>, <FIG> and <FIG>.

The motor drive <NUM> of handpiece <NUM> (<FIG>) couples to a rotating drive coupling <NUM> fabricated of a non-conductive material that rotates in hub <NUM> as shown in <FIG> and <FIG>. The drive coupling <NUM> has a distal cam surface <NUM> that engages the proximal-facing cam surface <NUM> on the actuator collar <NUM> so that rotation of drive coupling <NUM> will reciprocate the sliding actuator collar <NUM> through a forward and backward stroke AA, as schematically shown in <FIG>. While the cam surfaces <NUM> and <NUM> are illustrated schematically as bumps or cams, one of skill in the art will appreciate that the surfaces can be undulating or "wavy" or alternately comprise multiple facets to provide a ratchet-like mechanism wherein rotation of the rotating drive coupling in <NUM>° will reciprocate the sliding actuator collar <NUM> through a selected length stroke multiple times, for example from <NUM> to <NUM> times per rotation of the drive coupling <NUM>. It should also be appreciated that while full and continuous rotation of the rotating coupling <NUM> will usually be preferred, it would also be possible to rotationally oscillate (periodically reverse the direction of rotation between clockwise and counterclockwise) the rotating drive coupling <NUM>, for example to control a length of travel of the moveable active electrode <NUM> in the window <NUM> where a rotation of less than <NUM>° will result in a shortened length of travel. The stroke of the sliding actuator collar <NUM> and electrode <NUM> can be between <NUM> and <NUM>, and in one variation is between <NUM> and <NUM>. The selected RPM of the motor determines the reciprocation rate, and in one variation a controller 705C can select a motor operating RPM to provide a reciprocation rate between <NUM> and <NUM>,<NUM>, usually between <NUM> and <NUM>. In another variation, the RF ablation probe <NUM> can be selectively operated in different reciprocation modes (by controller 705C) to provide different reciprocation rates to provide different RF effects when treating tissue. In an additional variation, the length of the electrode stroke can be selected for different modes, wherein the housing <NUM> can be provided with a slidable adjustment (not shown) to adjust the distance between the cam surfaces <NUM> and <NUM> of the sliding collar <NUM> and rotating coupling <NUM>, respectively.

The RF probe of <FIG> also can be operated in different RF modes. As described above, a typical RF mode for dynamic RF ablation reciprocates the electrode <NUM> at a selected high speed while delivering RF current in a cutting waveform to thereby create a plasma that ablates tissue. In another RF mode, the controller 705C can include an algorithm that stops the reciprocation of electrode <NUM> in the extended position of <FIG> and <FIG> and then RF RF current in a coagulation waveform can be delivered to the electrode <NUM>. The operator can then move the stationary electrode over a targeted site for coagulation of tissue. In yet another RF mode, the controller 705C can reciprocate the electrode <NUM> as at slow rate (e. g,, <NUM> to <NUM>) while delivering a coagulation waveform to coagulate tissue.

Referring to <FIG>, <FIG> and <FIG>, the rotating coupling <NUM> is rotationally maintained in hub <NUM> by a flange <NUM> that projects into annular groove <NUM> in the hub <NUM>. The rotating drive coupling <NUM> is configured for coupling with the drive shaft <NUM> and transverse pin <NUM> of motor drive unit <NUM> as shown in <FIG>. As in previous embodiments of cutting or shaver assemblies, the negative pressure source 705B is coupled to a passageway <NUM> in handpiece <NUM> (<FIG>) that further communicates through the interior of the handpiece with opening <NUM> in the drive coupling <NUM> (see <FIG>) and lumen <NUM> in inner sleeve <NUM> to suction tissue into window <NUM>, as can be understood from <FIG>.

<FIG> is a longitudinal sectional view of the device hub <NUM> rotated <NUM>° from the sectional views of <FIG>. <FIG> shows the means provided for connecting the RF source 705A to the probe <NUM> and electrodes. In <FIG>, first and second electrical leads 790a and 790b are shown schematically extending from RF source 705A through handpiece <NUM> to electrical contact surfaces 792a and 792b in the receiving channel <NUM> in the handpiece <NUM>. <FIG> shows electrical contacts 795a and 795b in hub <NUM> as described previously which engage the contact surfaces 792a and 792b in the handpiece. In <FIG>, the first electrical lead 790a and contact surface 792a delivers RF electrical current to contact 795a in hub <NUM> which provides at least one ball and spring contact assembly <NUM> to deliver current to the conductive actuator collar <NUM> and inner sleeve <NUM> which is connected to active electrode <NUM> as described above. It can be understood that the ball and spring contact assembly <NUM> will allow the actuator collar <NUM> to reciprocate while engaging the contact assembly <NUM>. In one variation, two ball and spring contact assemblies <NUM> are provided on opposing sides of the hub <NUM> for assuring RF current delivery to the actuator collar <NUM>. The inward portions of the two ball and spring contact assemblies <NUM> also are disposed in axial channels or slots 798a and 798b in the actuator collar <NUM> and thus function as a slot and key features to allow the actuator collar <NUM> to reciprocate but not rotate.

Referring again to <FIG>, the second electrical lead 790b connects to contact surface 792b in handpiece receiving channel <NUM> which engages the electrical contact 795b in hub <NUM> of the RF probe <NUM>. It can be seen that an electrical path <NUM> extends from electrical contact 795b in the hub <NUM> to outer sleeve <NUM> wherein and an exposed portion of the outer sleeve <NUM> comprises a return electrode <NUM> as shown in <FIG>, <FIG> and <FIG>. It should be appreciated that the outer sleeve <NUM> can be covered on the inside and outside with a thin electrically insulating cover or coating (not shown) except for the exposed portion which comprises the return electrode <NUM>. The inner sleeve <NUM> has an insulative exterior layer <NUM> such as a heat shrink polymer shown in <FIG> and <FIG>. The insulative exterior layer <NUM> on the inner sleeve <NUM> is provided to electrically insulate the inner sleeve <NUM> from the outer sleeve <NUM>.

In a method of operation, it can be understood that the device can be introduced into a patient's joint that is distended with saline solution together with an endoscope for viewing the working space. Under endoscopic vision, the device working end is oriented to place the electrode <NUM> against a targeted tissue surface in the patient's joint, and thereafter the RF source 705A and negative pressure source 705B can be actuated contemporaneously to thereby suction tissue into the window <NUM> at the same time that an RF plasma is formed about the reciprocating electrode <NUM> which then ablates tissue. The ablated tissue debris is suctioned through the windows <NUM> and <NUM> into lumen <NUM> of inner sleeve <NUM> to the fluid outflow pathway in the handpiece <NUM>. Ultimately, the tissue debris is carried though the outflow pump system to the collection reservoir <NUM> (<FIG>). The device and system can be actuated by the footswitch 707a or a button 707b in the control panel of the handpiece <NUM> as described previously.

<FIG> shows the RF ablation probe or assembly <NUM> from a different angle where it can be seen that the rotating drive coupling <NUM> has a bore <NUM> and at least one slot <NUM> therein to receive that motor drive shaft <NUM> and transverse pin <NUM>. In another aspect of the disclosure, the drive coupling <NUM> has a smooth exterior surface <NUM> in <NUM>° around the coupling to provide an enclosure that surrounds and enclosed shaft <NUM> and transverse pin <NUM>. The exterior surface <NUM> and <NUM>° enclosure is configured to prevent a fluid outflow indicated by arrow <NUM> (which carries resected tissue debris) from clogging the system. It can be understood that resected tissue may include elongated, sinewy tissue strips that can wrap around the drive coupling <NUM> which is spinning at <NUM>,<NUM>-<NUM>,<NUM> RPM after being suctioned with fluid through opening <NUM> in the drive coupling <NUM>. Prior art devices typically have a drive shaft and pin arrangement that is exposed which then is susceptible to "catching" tissue debris that may wrap around the coupling and eventually clog the flow pathway. For this reason, the rotating drive coupling <NUM> has a continuous, smooth exterior surface <NUM>. In an aspect of the present disclosure, a disposable arthroscopic cutting or ablation device is provided that includes a rotating drive coupling that is adapted to couple to a motor drive shaft in a handpiece, wherein the rotating drive coupling has a continuous <NUM>° enclosing surface that encloses the drive shaft and shaft-engaging features of the drive coupling. In other words, the drive coupling <NUM> of the disclosure has motor shaft-engaging features that are within an interior receiving channel of the drive coupling. In another aspect of the disclosure, referring to <FIG>, the drive collar <NUM> of a shaver blade includes enclosing features 838a and 838b that are configured to carry magnets 840a and 840b. Such magnets are adapted to cooperate with Hall sensors (not shown) in the handpiece <NUM>. Such Hall sensors can be used for one or more purposes, including (i) calculating shaft RPM, (ii) stopping shaft rotation and thus electrode <NUM> and the inner sleeve window <NUM> in a selected axial position, and (iii) identifying the type of shaver blade out of a potential catalog of different shaver blades wherein the controller that operates the RF source 705A, negative pressure source 705B and motor controller 705C then can select different operating parameters for different shaver blades based identifying the blade type.

<FIG> illustrate a variation of an RF probe <NUM> with a working end <NUM> that is similar to the version of <FIG>. The electrosurgical RF ablation probe or assembly <NUM> again is adapted for use with the handle <NUM> and motor drive unit <NUM> as shown in <FIG>.

Referring to <FIG>, the working end <NUM> includes a ceramic housing <NUM> that has a lateral or side-facing window <NUM> in which the active electrode <NUM> reciprocates at high speed as described previously. The ceramic housing <NUM> is coupled to the distal end <NUM> of outer sleeve <NUM>. As can be seen in <FIG>, the ceramic housing <NUM> is formed in a proximal body portion 940A and a distal end-cap 940B which allows for simplified assembly of the working end <NUM>. The distal end-cap 940B is held in place by metal retaining strap <NUM> that fits into notch <NUM> in the end-cap 940B and is welded at several points <NUM> to the distal end <NUM> of outer sleeve <NUM> (<FIG>).

The inner sleeve <NUM> can be covered with an insulative shrink tube <NUM> as the inner sleeve carries electrical current to the active electrode <NUM> (<FIG>). The exterior of outer sleeve <NUM> comprises the return electrode <NUM>. In this variation, the proximal and distal edges 952a-952b of the electrode are adapted to extend slightly over the window edges 954a-954b so as to shear tissue with the energized RF electrode <NUM>. Likewise, the lateral edges 962a-962b of electrode <NUM> are adapted to extend over the lateral window edges 964a-964b to insure tissue suctioned into the window is entirely cut or sheared.

Referring to <FIG>, it has been found that rapid reciprocation or oscillation of the electrode <NUM> in window <NUM> is very effective in a tissue ablation procedure, in part, because the ablative plasma practically forms a plasma layer or cloud <NUM> over the area of the window <NUM> even through the surface of the electrode <NUM> may be only in transient contact with a portion of the plasma cloud <NUM>. The plasma layer or cloud is formed in an interface with targeted tissue wherein the plasma applies ablative energy to tissue as is known in the art. In an aspect of the disclosure shown in <FIG>, a method (i) ignites a plasma in a conductive liquid in a tissue interface using RF energy delivered from an electrode surface <NUM>, and (ii) moves the electrode surface <NUM> to form a plasma cloud <NUM> with a dimension that exceeds the area of electrode surface <NUM> wherein the rate of motion of the electrode surface delivers plasma-maintaining RF energy to the cloud <NUM> at a rater faster than the plasma cloud is extinguished in the conductive liquid. In a variation, the rate of motion of the electrode surface <NUM> is at least <NUM>/sec. In other variations, the rate of motion is least <NUM>/sec or at least <NUM>/sec.

More in particular, referring to <FIG>, the electrode surface <NUM> moves in alignment with a longitudinal axis <NUM> of shaft <NUM> and window <NUM>. The stroke of the electrode surface <NUM> has a dimension ranging between <NUM> and <NUM>, or more often, the stroke has a dimension ranging between <NUM> and <NUM>. The electrode surface <NUM> has a width WW dimension transverse to the axis of the stroke, with said width WW ranging between <NUM> and <NUM>, and more often between <NUM> and <NUM> (<FIG>). In the variation shown in <FIG>, the window <NUM> in the ceramic body <NUM> has an area ranging from <NUM><NUM> to <NUM><NUM> and thus the plasma cloud <NUM> may have a surface area ranging from <NUM><NUM> to <NUM><NUM>.

While the illustrated embodiment have and electrode that reciprocates in a predetermined cycles per second (Hz), it should be appreciated that electrode surface can be moved axially relative to the probe axis, or transverse relative to the probe axis, or can rotate relative to the probe axis. Thus, the needed rate of motion as described above can be provided by moving the electrode in any direction relative to the probe axis <NUM> to perform the method of the disclosure.

In general, a method for forming an RF plasma cloud for applying energy to tissue comprises immersing an electrode surface <NUM> in a conductive liquid in proximity to targeted tissue, and moving the electrode surface <NUM> over a selected cloud surface area while delivering electrical current to the moving electrode surface <NUM> such that a plasma cloud surface area is maintained although the electrode surface contacts only a portion of the cloud surface area at any point in time.

Another way to state the method for applying electrosurgical energy to tissue is immersing an electrode surface in a conductive liquid in proximity to targeted tissue and moving the electrode surface in a stroke at a selected Hz and applying an electrical current to the moving electrode surface adapted to form a transient plasma cloud thereabout which applies energy to the targeted tissue wherein the Hz rate is sufficiently fast to maintain the plasma cloud between the opposing ends of the stroke while the electrode surface is moving between said opposing ends of the stroke.

Referring again to the probes of <FIG> and <FIG>, a method of operating an electrosurgical probe comprises (i) providing an elongated shaft having a longitudinal axis, a windowed ceramic body carried at a distal end of the shaft, a moveable electrode surface disposed in the window, and a motor drive configured to move the electrode surface back and forth across the window, (ii) positioning the ceramic body and electrode surface in an interface with targeted tissue, and (iii) delivering an electrical current to the electrode and actuating the motor drive to move the electrode surface across the window at greater than <NUM> or greater than <NUM> to thereby ablate tissue in the interface. The targeted tissue is at least one of cartilage, meniscus, connective tissue, tendons, ligaments or synovial tissue.

In general, an RF probe corresponding to the disclosure comprises an elongated sleeve extending along a longitudinal axis with a windowed ceramic housing carried at a distal end of the sleeve and a motor-driven electrode surface configured to move across the window in the ceramic housing wherein a motor drive provides a rate of motion of the electrode surface of at least <NUM>/sec, at least <NUM>/sec or at least <NUM>/sec. The window has an area of <NUM><NUM> to <NUM><NUM> and the electrode surface has an area of <NUM><NUM> to <NUM><NUM>. The electrode surface can be moved across the window in a stroke having a dimension ranging between <NUM> and <NUM>, or more often ranging between <NUM> and <NUM>. The electrode surface can have a width dimension transverse to the axis of the stroke ranging between <NUM> and <NUM>, and more often between <NUM> and <NUM>. The ratio of the window area to the electrode surface area is at least <NUM>:<NUM> or at least <NUM>:<NUM>.

<FIG> illustrates another variation of an RF probe <NUM> that is similar to the version of <FIG>. The electrosurgical RF ablation probe <NUM> is again is adapted for use with the handle <NUM> and motor drive unit <NUM> as shown in <FIG>. In the variation shown in <FIG>, the probe <NUM> again has a shaft <NUM> with an outer sleeve <NUM> that carries a distal dielectric or ceramic housing <NUM> with a window <NUM> therein. The inner sleeve <NUM> has a distal end on which a dielectric or ceramic member <NUM> is mounted. In this variation, the electrode <NUM> has a loop configuration which is adapted for cutting strips of tissue. Such a loop-shaped electrode can be adapted to reciprocate at high speeds ass described above or can be moved in a single stroke for a slow, controlled resection of tissue. For example, in a mode of operation, a button on the handpiece or a footswitch could be actuated to cause a single reciprocation of the electrode together with actuation of the negative pressure source.

While the variations described above and shown in the drawings relate to RF probes that have an axially reciprocating electrode, it should be appreciated that a similar electrode can be configured to be driven laterally from side to side in a window of a ceramic housing carried at the distal end of an elongated. Such an RF probe can couple to the handpiece <NUM> and motor drive <NUM> as shown in <FIG>.

Although particular embodiments of the present disclosure have been described above in detail, it will be understood that this description is merely for purposes of illustration and the above description of the disclosure is not exhaustive. Specific features of the disclosure are shown in some drawings and not in others, and this is for convenience only and any feature may be combined with another in accordance with the disclosure. A number of variations and alternatives will be apparent to one having ordinary skills in the art.

The use of the terms "a" and "an" and "the" and similar referents in the context of describing the disclosure (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The term "connected" is to be construed as partly or wholly contained within, attached to, or joined together, even if there is something intervening. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate embodiments of the disclosure and does not pose a limitation on the scope of the disclosure unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the disclosure.

Claim 1:
An electrosurgical probe (<NUM>) comprising:
an elongated shaft assembly (<NUM>) having a proximal end, a distal end, and a longitudinal axis (<NUM>);
a housing (<NUM>) carried on the distal end of the shaft (<NUM>);
an interior channel (<NUM>) extending axially through the interior of the shaft and housing to an opening (<NUM>) in the housing (<NUM>), said opening having a proximal edge (<NUM>); and
an electrode (<NUM>) with an elongate edge (728a) extending laterally across the opening (<NUM>), said electrode (<NUM>) configured to reciprocate longitudinally relative to the opening (<NUM>) between an extended position and a retracted position, wherein the elongate edge (728a) of the electrode extends over the proximal edge of the opening (<NUM>) when the electrode (<NUM>) is in the retracted position to shear tissue interfacing with the opening (<NUM>),
wherein the shaft (<NUM>) comprises an outer sleeve (<NUM>) and an inner sleeve (<NUM>), wherein the housing is mounted on a distal end of the outer sleeve, the electrode is mounted on a distal end of the inner sleeve (<NUM>), and wherein the inner sleeve (<NUM>) is reciprocatably mounted in the outer sleeve (<NUM>).