Abstract:
A surgical device includes a return electrode, an active electrode, and an insulating region adjacent to the active electrode. A rasping surface is provided by either the active electrode or the insulating region. Another surgical device includes an adapter configured to couple to a generator and to convert monopolar output from the generator into bipolar output. A method of applying electricity to tissue includes bringing a surgical device into close proximity with tissue and applying electricity to the tissue using the surgical device.

Description:
BACKGROUND  
         [0001]    The invention relates to electrosurgery systems and, more particularly, to the use of electrosurgery in arthroscopy.  
           [0002]    In electrosurgery, electrical energy, such as, for example, high frequency and radio frequency electrical energy, is used to modify the structure of tissue. For example, an electrical current can be directed from a first electrode (an active electrode) to a second electrode (a return electrode), and the path of the current can be used to cut, coagulate, and ablate tissue.  
           [0003]    Electrosurgery is performed using monopolar instruments and bipolar instruments.  
           [0004]    With a monopolar instrument, electrical current is directed from an active electrode positioned at the tissue to be treated, through the patient&#39;s body to a return electrode generally in the form of a ground pad attached to the patient. With a bipolar instrument, both the active electrode and the return electrode are positioned at the tissue to be treated, and electrical current flows from the active electrode to the return electrode over a short distance.  
         SUMMARY  
         [0005]    Aspects of the invention relate to surgical systems and instruments, such as, for example, those that are used in the field of electrosurgery. For example, the surgical systems and instruments are used for arthroscopic surgical procedures, such as resection, ablation, excision of soft tissue, hemostasis of blood vessels and coagulation of soft tissue in patients requiring arthroscopic surgery of the knee, shoulder, ankle, elbow, wrist, or hip. In some embodiments, the invention features single-use instruments used with a conductive irrigating solution, such as saline and Ringer&#39;s lactate.  
           [0006]    According to one aspect, a surgical device includes an insulating region having a surface with a formation for providing a mechanical rasping action against tissue. The surgical device includes an active electrode, and the insulating region is adjacent the active electrode.  
           [0007]    Embodiments of this aspect may include one or more of the following features. The formation includes a groove. The formation includes a ridge. The ridge has a flat top-surface. The ridge has a curved top-surface. The formation includes at least one of a scallop, an edge, and a point. The insulating region substantially encircles a periphery of the active electrode. The insulating region includes an electrically non-conductive, refractory material. The active electrode includes a location that provides for concentration of current density. The active electrode includes a geometry having at least one location particularly adapted to provide light off. The location includes a raised portion.  
           [0008]    The surgical device includes a hand wand and a shaft rotatably coupled to the hand wand, and the shaft includes the active electrode and the insulating region. The shaft is continuously rotatable, such that the active electrode is continuously rotatable. The shaft defines an aspiration lumen. The surgical device includes a tube coupled to the shaft, and a suction control coupled to the tube. The tube defines a lumen in communication with the aspiration lumen and the suction control is for controlling suction through the aspiration lumen. The control includes a valve. The surgical device includes a rotation control coupled to the shaft for rotating the shaft. The rotation control includes a hand-actuated knob. The surgical device includes a power control coupled to the hand wand for controlling power applied to the active electrode. The power control includes a push button.  
           [0009]    An electrical characteristic of the surgical device is substantially uniform around a periphery of the active electrode when the electrical characteristic is measured in a plane. The plane is perpendicular to an engagement angle between the active electrode and a tissue surface, and the plane goes through part of the active electrode. The electrical characteristic includes electric field strength. The engagement angle includes an angle providing substantially maximum tissue contact between the active electrode and a flat tissue surface. The active electrode includes a surface configured to contact tissue at an angle that is not parallel to a longitudinal axis of the surgical device.  
           [0010]    An electrical characteristic of the surgical device measured at any point in a given plane that is at least {fraction (3/100)} of an inch outside of an envelope of an active electrode drops off to no more than 60% of a maximum value for the electrical characteristic in the given plane. The active electrode defines the envelope in the given plane. The given plane goes through the active electrode. The electrical characteristic includes electric field strength. The given plane is perpendicular to an engagement angle between the active electrode and a tissue surface. The engagement angle provides substantially maximum tissue contact between the active electrode and a flat tissue surface. The active electrode includes a surface configured to contact tissue at an angle that is not parallel to a longitudinal axis of the surgical device.  
           [0011]    An electrical characteristic of the surgical device measured at any point in a plane corresponding to a tissue depth of at least {fraction (3/100)} of an inch drops off to no more than 60% of a maximum value in the plane. The active electrode contacts a tissue surface. The plane goes through the active electrode and the tissue surface. The electrical characteristic includes electric field strength. The electric field strength drops off to no more than half the maximum value at any point in the plane corresponding to a tissue depth of at least {fraction (15/1000)} of an inch. The plane is parallel to an engagement angle between the active electrode and the tissue surface.  
           [0012]    The active electrode defines an envelope in a given plane, the given plane goes through the active electrode and an electrical characteristic of the surgical device achieves a maximum for the given plane outside of the envelope. The surgical device includes a return electrode. The surgical device includes an adapter electrically coupled to the active electrode and the return electrode. The adapter is configured (i) to couple to a generator, (ii) to convert monopolar output from the generator into bipolar output, and (iii) to provide the bipolar output to the active electrode. The adapter is further configured to convert substantially constant power output from the generator into substantially constant voltage output.  
           [0013]    According to another aspect, a method includes rasping tissue mechanically using a formation on a surface of an insulating region. The method includes applying electrical energy to tissue using an active electrode of a surgical device, and the insulating region is adjacent the active electrode.  
           [0014]    Embodiments of this aspect may include one or more of the following features. Rasping tissue includes using a ridge as the formation. Applying electrical energy includes using a location on the active electrode, the location being particularly adapted to provide light off. Rasping tissue includes providing a user of the surgical device tactile feedback from tissue. The method includes penetrating a joint in a body with the active electrode and the formation of the surgical device. The method includes ablating tissue with the applied electrical energy. The method includes coagulating tissue with the applied electrical energy.  
           [0015]    According to another aspect, a surgical device includes an insulating region having a surface adapted for providing a mechanical rasping action against tissue. The surgical device includes an active electrode, and the insulating region is adjacent the active electrode.  
           [0016]    According to another aspect, a surgical device includes an insulating region having a roughened surface for providing a mechanical rasping action against tissue. The surgical device includes an active electrode, and the insulating region is adjacent the active electrode.  
           [0017]    According to another aspect, a surgical device includes an active electrode, and an electrical characteristic of the surgical device achieves a maximum for a given plane outside of an envelope defined by the active electrode in the given plane. The given plane goes through the active electrode.  
           [0018]    Embodiments of this aspect may include one or more of the following features. The electrical characteristic is substantially uniform around a periphery of the active electrode when the electrical characteristic is measured in the given plane. The given plane is perpendicular to an engagement angle between the active electrode and a tissue surface. The electrical characteristic measured at any point in the given plane that is at least {fraction (3/100)} of an inch outside of the envelope drops off to no more than 60% of a maximum value for the electrical characteristic in the given plane.  
           [0019]    According to another aspect, a surgical device includes a hand wand and a shaft rotatably coupled to the hand wand and continuously rotatable with respect to the hand wand. The shaft is adapted to be inserted into a joint in a body.  
           [0020]    Embodiments of this aspect may include one or more of the following features. The surgical device includes a rotation control coupled to the shaft for rotating the shaft. The shaft defines an aspiration lumen and the surgical device includes a tube coupled to the shaft and a suction control coupled to the tube. The tube defines a lumen in communication with the aspiration lumen, and the suction control is for controlling suction through the aspiration lumen. The surgical device includes an active electrode coupled to the shaft. The surgical device includes a power control coupled to the hand wand for controlling power applied to the active electrode. The rotation control includes a knob. The suction control includes a valve. The power control includes a push button.  
           [0021]    According to another aspect, a method includes inserting a shaft of a surgical device into a joint in a body, the shaft being rotatably coupled to a grip, and rotating the shaft through more than 360 degrees in one direction without rotating the grip.  
           [0022]    Embodiments of this aspect may include one or more of the following features. The method includes aspirating fluid through a lumen defined by the shaft, and controlling the aspirating using an aspiration control coupled to the grip. The method includes applying electrical power to an active electrode coupled to the shaft, and controlling the power using a power control coupled to the grip.  
           [0023]    According to another aspect, a system includes an adapter that includes first circuitry to convert monopolar output from a generator into bipolar output for an active electrode. The adapter is configured to be electrically coupled to the active electrode and to the generator.  
           [0024]    Embodiments of this aspect may include one or more of the following features. The first circuitry is adapted to convert substantially constant power output from the generator into substantially constant voltage output. The adapter is configured to be electrically coupled to a return electrode, and the adapter includes second circuitry to receive bipolar return from the return electrode. The first circuitry and the second circuitry overlap such that each of the first circuitry and the second circuitry include a specific circuit element. The system includes the active electrode and the return electrode, the active electrode and the return electrode both being electrically coupled to the adapter.  
           [0025]    According to other aspects, the invention relates to methods and apparatus for rasping tissue while applying electrical energy to the tissue.  
           [0026]    Advantages of the invention may include (i) providing a surgeon tactile feedback as well as the ability to move or disrupt tissue by providing a rasping formation on a surgical tip, (ii) allowing access to tissue at different sites within a body by providing different surgical tips and a rotatable surgical tip, (iii) allowing a surgeon to effectively operate on tissue by providing relatively uniform electrical characteristics around the entire perimeter of an electrode, and by providing a high electric field strength outside of and/or above the envelope of an electrode, (iv) reducing the risk of burning tissue below the surface tissue that is of interest by providing an electric field strength or other electrical characteristic that falls off quickly within tissue, (v) minimizing the possibility of runaway current during electrosurgery by providing an adapter that converts constant power output from a generator to constant voltage output for an electrosurgical probe, (vi) simplifying endoscopic operations by providing suction to remove debris and bubbles to maintain a clear view of the target tissue, (vii) simplifying endoscopic operations by providing a surgical instrument with a hand grip that includes controls for power, suction, and/or rotation, and (viii) reducing patient burn and other disadvantages of monopolar devices by providing a bipolar surgical device.  
           [0027]    The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and the drawings, and from the claims. 
       
    
    
     DESCRIPTION OF DRAWINGS  
       [0028]    [0028]FIG. 1 is a perspective view of an embodiment of a surgical system including a generator, an adapter module and a probe;  
         [0029]    [0029]FIG. 2 is a perspective view of the generator of FIG. 1 with a front, exploded view of the adapter module;  
         [0030]    [0030]FIG. 3 is a back exploded view of the adapter module of FIG. 2;  
         [0031]    [0031]FIG. 3A shows a perspective view of the back of another adapter module;  
         [0032]    [0032]FIG. 3B shows a perspective view of the front of the adapter module of FIG. 3A;  
         [0033]    [0033]FIG. 3C shows a cross-sectional view of the adapter module of FIG. 3B, taken along line  3 C- 3 C;  
         [0034]    [0034]FIG. 3D is a front, exploded view of the adapter module of FIG. 3A;  
         [0035]    [0035]FIG. 3E is a back, exploded view of the adapter module of FIG. 3A;  
         [0036]    [0036]FIG. 4 is a front view of the adapter module of FIG. 2;  
         [0037]    [0037]FIG. 5 is a cross-sectional view of the adapter module of FIG. 4, taken along line  55 ;  
         [0038]    [0038]FIG. 6 is a partial schematic diagram of an embodiment of an adapter module and a probe with hand switches;  
         [0039]    [0039]FIG. 7 is a partially cut-away, perspective view of the probe of FIG. 1;  
         [0040]    [0040]FIG. 8 is a detailed, partially cut-away, perspective view of the probe of FIG. 1;  
         [0041]    [0041]FIG. 9 is a detailed cross-sectional view of the probe of FIG. 1;  
         [0042]    [0042]FIG. 10 illustrates the wiring of the probe of FIG. 1;  
         [0043]    [0043]FIG. 11 is a partial schematic diagram of an embodiment of a probe without hand switches;  
         [0044]    [0044]FIGS. 12A and 12B are perspective views of an embodiment of a valve housing;  
         [0045]    [0045]FIG. 13 is a perspective view of an embodiment of a valve actuator;  
         [0046]    [0046]FIG. 14 is a cross-sectional view of an embodiment of a valve;  
         [0047]    FIGS.  15 - 15 H are perspective views of various embodiments of a surgical tip;  
         [0048]    [0048]FIG. 16 is a perspective view of an embodiment of a surgical tip;  
         [0049]    [0049]FIG. 16A is an exploded perspective view of the surgical tip of FIG. 16;  
         [0050]    [0050]FIG. 16B is a top view of the surgical tip of FIG. 16;  
         [0051]    [0051]FIG. 16C is a cross-sectional view of the surgical tip of FIG. 16B, taken along line  16 C- 16 C;  
         [0052]    [0052]FIG. 16D is a cross-sectional end view of the surgical tip of FIG. 16C, taken along line  16 D- 16 D;  
         [0053]    [0053]FIG. 16E is a cross-sectional view of the surgical tip of FIG. 16B, taken along line  16 E- 16 E;  
         [0054]    [0054]FIG. 16F is a cross-sectional end view of the surgical tip of FIG. 16E, taken along line  16 F- 16 F;  
         [0055]    [0055]FIG. 16G is a perspective view of another embodiment of a surgical tip;  
         [0056]    [0056]FIG. 16H is an exploded perspective view of the surgical tip of FIG. 16G;  
         [0057]    [0057]FIG. 16I is a top view of the surgical tip of FIG. 16G;  
         [0058]    [0058]FIG. 16J is a cross-sectional view of the surgical tip of FIG. 16I, taken along line  16 J- 16 J;  
         [0059]    [0059]FIG. 16K is an end view of the surgical tip of FIG. 16G;  
         [0060]    [0060]FIG. 17 is a perspective view of another embodiment of a surgical tip;  
         [0061]    [0061]FIG. 17A is an exploded perspective view of the surgical tip of FIG. 17;  
         [0062]    [0062]FIG. 17B is a top view of the surgical tip of FIG. 17;  
         [0063]    [0063]FIG. 17C is a cross-sectional view of the surgical tip of FIG. 17B, taken along line  17 C- 17 C;  
         [0064]    [0064]FIG. 17D is an end view of the surgical tip of FIG. 17;  
         [0065]    [0065]FIG. 18 is a perspective view of another embodiment of a surgical tip;  
         [0066]    [0066]FIG. 18A is an exploded perspective view of the surgical tip of FIG. 18;  
         [0067]    [0067]FIG. 18B is a top view of the surgical tip of FIG. 18;  
         [0068]    [0068]FIG. 18C is a cross-sectional view of the surgical tip of FIG. 18B, taken along line  18 C- 18 C;  
         [0069]    [0069]FIG. 18D is a cross-sectional view of the surgical tip of FIG. 18C, taken along line  18 D- 18 D;  
         [0070]    [0070]FIG. 18E is an end view of the surgical tip of FIG. 18;  
         [0071]    [0071]FIG. 19 is a perspective view of another embodiment of a surgical tip;  
         [0072]    [0072]FIG. 19A is an exploded perspective view of the surgical tip of FIG. 19;  
         [0073]    [0073]FIG. 19B is a top view of the surgical tip of FIG. 19;  
         [0074]    [0074]FIG. 19C is a cross-sectional view of the surgical tip of FIG. 19B, taken along line  19 C- 19 C;  
         [0075]    [0075]FIG. 19D is a cross-sectional view of the surgical tip of FIG. 19C, taken along line  19 D- 19 D;  
         [0076]    [0076]FIG. 19E is an end view of the surgical tip of FIG. 19;  
         [0077]    [0077]FIG. 20 is a perspective view of another embodiment of a surgical tip;  
         [0078]    [0078]FIG. 20A is an exploded perspective view of the surgical tip of FIG. 20;  
         [0079]    [0079]FIG. 20B is a top view of the surgical tip of FIG. 20;  
         [0080]    [0080]FIG. 20C is a cross-sectional view of the surgical tip of FIG. 20B, taken along line  20 C- 20 C;  
         [0081]    [0081]FIG. 20D is an end view of the surgical tip of FIG. 20;  
         [0082]    FIGS.  21 A-C are perspective, top, and side views, respectively, of an embodiment of an electrode:  
         [0083]    [0083]FIG. 22 is a perspective view of another embodiment of a surgical tip;  
         [0084]    [0084]FIG. 22A is an exploded perspective view of the surgical tip of FIG. 22;  
         [0085]    [0085]FIG. 22B is a top view of the surgical tip of FIG. 22;  
         [0086]    [0086]FIG. 22C is a cross-sectional view of the surgical tip of FIG. 22B, taken along line  22 C- 22 C;  
         [0087]    [0087]FIG. 22D is an end view of the surgical tip of FIG. 22;  
         [0088]    [0088]FIG. 23 is a perspective view of another embodiment of a surgical tip;  
         [0089]    [0089]FIG. 23A is an exploded perspective view of the surgical tip of FIG. 23;  
         [0090]    [0090]FIG. 23B is a top view of the surgical tip of FIG. 23;  
         [0091]    [0091]FIG. 23C is a cross-sectional view of the surgical tip of FIG. 23B, taken along line  23 C- 23 C;  
         [0092]    [0092]FIG. 23D is an end view of the surgical tip of FIG. 23;  
         [0093]    FIGS.  24 A-C are perspective, top, and side views, respectively, of another embodiment of an electrode;  
         [0094]    [0094]FIG. 25 is a longitudinal cross-sectional view of another embodiment of a surgical tip, taken along the same line as FIG. 16C;  
         [0095]    [0095]FIG. 25A is a longitudinal cross-sectional view of the surgical tip of FIG. 25, taken along the same line as FIG. 16E;  
         [0096]    [0096]FIG. 25B is a radial cross-sectional view of the surgical tip of FIG. 25, taken along line  25 B- 25 B;  
         [0097]    [0097]FIG. 25C is a radial cross-sectional view of the surgical tip of FIG. 25A, taken along line  25 C- 25 C;  
         [0098]    [0098]FIG. 26 is a perspective view of another assembled surgical tip;  
         [0099]    [0099]FIG. 26A is an exploded perspective view of the surgical tip of FIG. 26;  
         [0100]    [0100]FIG. 26B is a top view of the surgical tip of FIG. 26;  
         [0101]    [0101]FIG. 26C is a longitudinal cross-sectional view of the surgical tip of FIG. 26B, taken along line  26 C- 26 C;  
         [0102]    [0102]FIG. 26D is a longitudinal cross-sectional view of the surgical tip of FIG. 26C, taken along line  26 D- 26 D;  
         [0103]    [0103]FIG. 26E is a distal end view of the surgical tip of FIG. 26.  
         [0104]    [0104]FIG. 27 is a perspective view of another assembled surgical tip;  
         [0105]    [0105]FIG. 27A is an exploded perspective view of the surgical tip of FIG. 27;  
         [0106]    [0106]FIG. 27B is a top view of the surgical tip of FIG. 27;  
         [0107]    [0107]FIG. 27C is a longitudinal cross-sectional view of the surgical tip of FIG. 27B, taken along line  27 C- 27 C;  
         [0108]    [0108]FIG. 27D is an enlarged portion of FIG. 27C;  
         [0109]    [0109]FIG. 27E is a distal end view of the surgical tip of FIG. 27;  
         [0110]    [0110]FIG. 28 is perspective view of a housing of another surgical tip;  
         [0111]    [0111]FIG. 28A is a perspective view of an electrode for use with the housing of FIG. 28;  
         [0112]    [0112]FIG. 29 is a perspective view of another assembled surgical tip;  
         [0113]    [0113]FIG. 29A is an exploded perspective view of the surgical tip of FIG. 29;  
         [0114]    [0114]FIG. 29B is a top view of the surgical tip of FIG. 29;  
         [0115]    [0115]FIG. 29C is a longitudinal cross-sectional view of the surgical tip of FIG. 29B, taken along line  29 C- 29 C;  
         [0116]    [0116]FIG. 29D is an enlarged portion of FIG. 29C;  
         [0117]    [0117]FIG. 29E is a distal end view of the surgical tip of FIG. 29;  
         [0118]    [0118]FIG. 30 includes a graph of isometric lines of electric potential for the surgical tip of FIGS.  25 - 25 F;  
         [0119]    [0119]FIG. 31 includes a graph of electric field vectors for the surgical tip in the graph in FIG. 30;  
         [0120]    [0120]FIG. 32 includes a graph of electric field vectors for the surgical tip of FIGS.  18 - 18 E;  
         [0121]    [0121]FIG. 33 includes a graph of isometric lines of electric potential for a portion of the surgical tip of FIGS.  27 - 27 E; and  
         [0122]    [0122]FIG. 34 includes a graph of electric field vectors for the portion of the surgical tip in the graph in FIG. 33. 
     
    
       [0123]    All dimensions shown and materials listed in the figures are illustrative and not intended to be limiting. Distance dimensions are in inches unless otherwise noted.  
       DETAILED DESCRIPTION  
       [0124]    Referring to FIG. 1, a surgical system  30  includes a generator  32 , an adapter module  34  connectable to generator  32 , and a radio frequency bipolar probe  36  connectable to adapter module  34 . Probe  36  includes a hand wand  38  having a proximal end  40  and a distal end  42 . Wand  38  has a cable  44  and a suction tube  46  extending from its proximal end  40 . Cable  44  terminates with a male connector  48 , and suction tube  46  terminates with a suction barb connector  52 . Male connector  48  is configured to mate with a female receptacle  50  defined by module  34 . At its distal end  42 , wand  38  has a rotation tube  54 , e.g., made of stainless steel, extending therefrom and terminating at a surgical tip  56 , having, for example, an active electrode. The length of rotation tube  54  is electrically insulated, e.g., with a heat shrink polymer, except a portion of the rotation tube near tip  56  is uninsulated to serve as a return electrode.  
         [0125]    Generally, generator  32  provides constant electric power to adapter module  34 , which converts the power to a form useable by probe  36 , e.g., approximately constant voltage. The converted power is sent to surgical tip  56  via cable  44 , wand  38 , and rotation tube  54 . By manipulating probe  36  at a tissue site and selectively applying power, a surgeon can use surgical system  30  for electrosurgery.  
         [0126]    Referring to FIG. 2, generator  32  has a front portion  70  that includes a power switch  66 , a bipolar current output  72 , a first monopolar current output  74 , a second monopolar current output  76 , and a return current input  78 . Generator  32  can be a commercially available generator, such as a Force FX™/Force FX™-C generator, available from Valleylab Inc., Boulder, Colo.  
         [0127]    Referring to FIGS.  2 - 5 , adapter module  34  has a unibody design that simultaneously establishes all appropriate connections to generator  32  and blocks unwanted connections. Adapter module  34  can be a commercially available adapter, such as a Dyonics® Control RF Generator Adaptor, available from Smith &amp; Nephew, Andover, Mass. Adapter module  34  is configured to attach to front portion  70  of generator  32 , and to convert the constant power output from the generator to a constant voltage output to probe  36 , thereby minimizing the possibility of runaway current during use. Module  34  includes a front plate  58  and a back plate  60  that, when connected together with screws  61 , form a housing for the module. Back plate  60  includes a covered recess  80 , a central opening  82 , a current output opening  84 , and a current input opening  86 . Recess  80  is configured to engage bipolar current output  72 , thereby blocking the bipolar current output and preventing probe  36  from being used with an inappropriate power output, e.g., bipolar current. Around central opening  82 , back plate  60  is connected to a housing  88 . Housing  88  mates with first monopolar current output  74  of generator  32 . Similar to recess  80 , housing  88  is configured to block first monopolar current output  74  and to prevent probe  36  from being used with an inappropriate power output. Housing  88  and recess  80  can also serve as a guiding mechanism for attaching module  34  to generator  32 . Housing  88  contains a member  90  made of a resilient and expandable material such as Santoprene rubber. As will soon be described, member  90  provides an attachment mechanism between module  34  and generator  32 . Current output opening  84  and current input opening  86  are configured to overlap with second monopolar current output  76 , and return current input  78 , respectively.  
         [0128]    Front plate  58  of adapter module  34  includes a power switch opening  62 , female receptacle  50 , and a cam lock opening  64 . Power switch opening  62  provides access to power switch  66  when module  34  is attached to generator  32  (FIG. 1). As discussed above, female receptacle  50  receives male connector  48  of probe  36 . Cam lock opening  64  receives a cam lock  68 , which is connected to member  90  to provide an attachment mechanism between module  34  and generator  32 . During use, module  34  is placed over front portion  70  of generator  32  and attached by turning cam lock  68  from an unlock position to a lock position. This action causes portions of member  90  to expand sufficiently out of housing  88 , thereby providing an interference fit between member  90  and first monopolar current output  74 .  
         [0129]    To further secure module  34  to generator  32 , module  34  includes two clips  92 , each connected to a leaf spring  94 . Leaf springs  94  connect clips  92  to front portion  70  of generator  32 , and clips  92  hook to the underside of the generator (FIG. 5).  
         [0130]    Inside its housing, module  34  includes electronic circuitry that converts constant power to constant voltage, and sends the voltage to probe  36  via male connector  48 . FIG. 6 shows a schematic circuit diagram of the electronic circuitry having two sets of two capacitors. The two sets of capacitors, e.g., cera-mite high voltage capacitors (250 pF, 10,000 VDC), are placed in parallel. By placing the two sets of capacitors in parallel, the capacitors serve as voltage dividers and current limiters. Further, the capacitors provide a capacitive load that is large compared to the capacitive load near tip  56 . The voltage division, current limiting, and large relative capacitive load enable the conversion from constant power to constant voltage, or substantially constant voltage.  
         [0131]    Referring again to FIGS. 2 and 3, the electronic circuitry includes a wiring harness  96  that connects to the interior side of female receptacle  50 , a three-pin male connector  98  whose pins connect to second monopolar current output  76  through current output opening  84 , and a two-pin male connector  100  whose pins connect to return current input  78  through current input opening  86 .  
         [0132]    Referring to FIGS.  3 A- 3 E another adapter module  34 A includes a housing  88 A used in place of housing  88  (FIG. 3) to mate with first monopolar current output  74  of generator  32  (FIG. 2). Housing  88 A is coupled to member  90 A which may be substantially similar to member  90  (FIGS.  2 - 3 ). Housing  88 A includes four projections  89  (FIG. 3A) that mate with corresponding receiving holes (see FIG. 2) in first monopolar current output  74 .  
         [0133]    Projections  89  plug into first monopolar current output  74 , and at least one of projections  89 , for example, an end projection, activates or selects a particular mode in generator  32 . Projections  89  need not be electrical contacts, but can activate the particular mode by mechanical or other means. In one implementation, the short projection, of projections  89 , activates a micro-switch in generator  32  to select the mode. Generator  32  is, for example, a Valleylab Force FX™, and the particular mode is, e.g., a reduced power mode that limits the output power for cutting to 100 Watts and for coagulating to 70 Watts. Housing  88 A also serves as a guiding mechanism for attaching adapter module  34 A to generator  32 .  
         [0134]    Referring to FIGS.  7 - 9 , adapter module  34  and wand  38  are connected by cable  44  and a suction tube  46 . Suction tube  46  extends from the proximal end of wand  38  to male connector  48  where the tube terminates in suction barb connector  52 , which is generally not integrally formed with male connector  48  (compare FIG. 1 and FIG. 7). At its proximal end  102 , cable  44  terminates in male connector  48  having five pins  104  configured to connect with sockets (not shown) in female receptacle  50  of module  34 . Pins  104  include two long pins  105  at lateral ends of male connector  48 , and three short pins  107  grouped offset from the center of the male connector. Pins  104  are arranged on male connector  48  such that the male connector can be inserted in female receptacle  50  in only one orientation, thereby minimizing misuse of probe  36 . At its distal end  106 , cable  44  terminates in wand  38 . Specifically, cable  44  includes an electrically insulating outer tubing that includes an integrally-formed grommet  169  near the distal end of the cable (FIG. 8). Grommet  169  engages a rounded recess defined by a wall  130  of wand  38  to help secure cable  44  to wand  38 .  
         [0135]    Cable  44  includes five conductors that extend from pins  104  to wand  38 . FIGS. 6 and 10 show schematic diagrams of the connection of conductors. Generally, an active conductor  108  is connected to an electrode  110 , and a return conductor  112  is connected to rotation tube  54 , an uninsulated portion of which serves as a return electrode. Three other conductors (a cut conductor, a coagulation conductor, and a second active conductor) are connected to a printed circuit board  114 , which is used to control the type of power provided to electrode  110 , e.g., power of different waveforms such as pulses and continuous power. Printed circuit board  114  is connected to a silicone keypad  115  provided on top of a housing  120  to provide manual control of power. Other power controls may be used, and control may be continuously variable, such as with a knob, or variable among a discrete number of options, such as with a switch. Examples of different power settings include 0-70 watts for coagulation and 0-120 watts for cutting. One implementation uses two push buttons for hand control of power, with the push buttons providing power only when pressed and held. One push button enables cut power and the other push button enables coagulation power. The same implementation optionally provides the same cut/coagulation control with a foot pedal, and controls the power setting, that is, the Watts level, at the generator.  
         [0136]    In some embodiments, generator  32  can be equipped with a foot control, e.g., to control power. FIG. 11 shows another embodiment of a schematic diagram of the connection of the conductors. In this embodiment, a foot control is used in lieu of the circuit board to control power, so the printed circuit board is used only to terminate the conductors and is a blank board.  
         [0137]    Referring again to FIGS.  7 - 9 , wand  38  includes a left handle  118  and a right handle  119  (FIG. 1) that together form housing  120 . Handles  118  and  119  are mirror images of each other. When left and right handles  118  and  119  are connected together, housing  120  defines a wall  130  that divides the housing into a proximal chamber  122  and a distal chamber  124 . Handles  118  are connected together by ultrasonic sealing or welding. The edge perimeter of distal chamber  124  includes a continuous raised ridge  121  that acts as an energy director during ultrasonic sealing to minimize leaks, e.g., aspirated fluid, from wand  38 . The edge perimeter of proximal chamber  122  includes spaced-apart ridges  123  that act as energy directors during ultrasonic sealing.  
         [0138]    Proximal chamber  122  contains a valve  136 , suction tube  46 , and cable  44 . Valve  136  regulates suction between suction tube  46  and surgical tip  56  (as described below). Referring to FIGS. 12A, 12B,  13  and  14 , valve  136  includes a valve housing  140  and a valve actuator  146 . Valve housing  140  includes a bell housing  138 , a central housing  141  connected to the bell housing by a tubular bridging portion  148 , and a tubular section  150  connected to the central housing. When valve  136  is assembled in an assembled probe  36 , bell housing  138  is located in distal chamber  124 , and central housing  139  is located in proximal chamber  122 . Bell housing  138  defines a chamber  139 ; bridging portion  148  defines a bore  149 ; central housing  141  defines a chamber  143 ; and tubular section  150  defines a bore  151 . Bores  149  are  151  are coaxial. Thus, valve housing  140  provides fluid communication between chamber  139  and bore  151  (FIG. 14). Bridging portion  148  further defines an exterior annular groove  152  that engages a rounded recess of wall  130 , thereby helping to retain valve  140  in place when left and right handles  118  and  119  are connected together (FIG. 8). Tubular section  150  further defines an exterior that is configured to mate with suction tube  46 . When probe  36  is fully assembled, suction tube  46  mates with tubular section  150 .  
         [0139]    Referring to FIGS. 13 and 14, valve actuator  146  is generally configured to mate with valve housing  140  to regulate suction through tube  46 . In particular, valve actuator  146  includes a generally tubular portion  154  and an arm  156  connected to the tubular portion. Tubular portion  154  is configured to mate with central housing  141  and be rotatable inside the central housing. Tubular portion  154  also defines an annular groove  155  configured to receive an O-ring (not shown) to provide a tight seal between tubular portion  154  and central housing  141  when they are mated. Arm  156  is connected to a suction slide button  144  slidably positioned on top of wand  38  such that moving the slide button back and forth rotates tubular portion  154  within valve housing  140 . Tubular portion  154  includes a bore  158  that extends through the tubular portion such that when valve actuator  146  mates with valve housing  140 , bore  158  can align or misalign with bores  149  and  151 . Thus, during use, when suction tube  46  provides a suction force to bore  151 , the amount of suction force provided to bore  149  can be regulated by moving slide button  144 , which controls the degree of alignment between bore  158  of actuator  146  and bores  149  and  151  of valve housing  140 . For example, when slide button  144  is positioned at a most proximal position, bore  158  is completely misaligned with bores  149  and  151 , and no suction force is provided to bore  149  and chamber  139 . When slide button  144  is positioned at a most distal position, bore  158  is completely aligned with bores  149  and  151 , and all the applied suction force provided by suction tube  46  is provided to bore  149  and chamber  139 . For relatively easy movement, valve housing  140  and valve actuator  146  can be made, for example, of lubricious materials such as nylon and polycarbonate.  
         [0140]    Referring again to FIG. 8, left and right handles  118  and  119  define support elements  128  and  132  in proximal chamber  122  that help hold cable  44  and suction tube  46 , respectively, in wand  38 . Support element  128  defines a rounded portion that is configured to engage a grommet  134  integrally formed with cable  44 , thereby preventing cable  44  from being pulled from wand  38 . Support element  132  defines a V-shaped groove (not shown) that engages tubular section  150  of valve housing  140  to help hold the housing in place, e.g., when a user slides button  144 .  
         [0141]    In distal chamber  124 , wand  38  includes a conductive rear clamp  170 , a conductive rear contact  172 , an insulating rotation core  174 , and a conductive front clamp  176 . Rotation core  174  is generally a hollow tubular member. Rotation core  174  is supported, in part, by a support element  177  integrally defined by left and right handles  118  and  119 . Clamps  170  and  176 , shown in cross-sectional views in FIG. 10, are metallic clamps with solder tabs. Clamps  170  and  176  are attached to left handle  118 . Rear clamp  170  is configured to engage with and secure rear contact  172 , while still allowing the rear contact to rotate. Rear contact  172  is a metallic member having an opening at its generally flat base and a vertical corrugated wall, e.g., similar to the bundt cake pan. The opening at the base of rear contact  172  defines engaging elements, e.g., teeth, that can engage with rotation core  174 , described below. The grooves and peaks defined by corrugations of rear contact  172  are spaced, in this embodiment, fifteen degrees apart. Other spacing intervals are possible. Thus, as described below, as rotation tube  54  is rotated and rear contact  172  rotates with the rotation tube, the rotation tube can be temporarily “locked”, e.g., indexed, into position every fifteen degrees via the rear contact.  
         [0142]    Near the proximal end of distal chamber  124 , rotation core  174  is configured to mate with bell housing  138  at a proximal end and with rotation tube  54  at a distal end. Near its proximal end, rotation core  174  passes through the base opening of rear contact  172 . The engaging elements defined by rear contact  172  grip rotation core  174  with a press fit such that the rear contact and the rotation core rotate together. At its proximal end, rotation core  174  mates with chamber  139  and butts against bell housing  138  (FIG. 9). Bell housing  138  includes an O-ring  178  therein to provide a tight seal between the bell housing and rotation core  174  when they engage. Bell housing  138  remains stationary, held in place in part by wall  130 . At its distal end, rotation core  174  mates with the proximal end of rotation tube  54 . Rotation core  174  and rotation tube  54  are securely connected, e.g., with an interference fit and/or an adhesive, such that they rotate together. Rotation core  174  defines an opening  180  that allows active electrode conductor  108  to be threaded into lumens defined by the rotation core and rotation tube  54 . The active electrode conductor then makes electrical contact with an active electrode at tip  56 , as described below.  
         [0143]    Front clamp  176  is attached to left handle  118  and is configured to engage with and secure an uninsulated portion of rotation tube  54 , while still allowing the rotation tube to rotate. Front-clamp  176  is connected to return electrode conductor  112 , and since the front clamp and rotation tube  54  are electrically connected, the rotation tube serves as a return electrode. Front clamp  176  is generally similar to rear clamp  170  in design but smaller to engage rotation tube  54 .  
         [0144]    Referring again to FIG. 6, the electrical wiring of wand  38  is shown. Active conductor  108  extends from cable  44  and is soldered to rear clamp  170 , e.g., to a solder tab. An insulated second segment of active conductor  182  is then connected, e.g., by soldering, to rear contact  172 , passed through opening  180 , and extended through lumens defined by rotation core  174  and rotation tube  54  to tip  56 . Second segment of active conductor  182  then electrically contacts an active electrode at the distal end of rotation tube  54 . By using two segments of an active conductor, rotation tube  54 , rotation core  174 , and rear contact  172  can be rotated freely 360 degrees, e.g., without the active conductor entangling with or wrapping around a component of wand  38 . Opening  180  of rotation core  174  is sealed, e.g., with a UV-curable epoxy, to provide the lumens of rotation core  174  and rotation tube  54  with an air and liquid tight seal. Return conductor  112  extends from cable  44  and is soldered to front clamp  176 , e.g., to a solder tab. Front clamp  176  clamps an uninsulated portion of rotation tube  54 .  
         [0145]    At the distal end of right and left handles  118 , wand  38  includes a nose piece assembly  126  having a nose piece  184  and a nose piece mount  186 . Referring to FIG. 9, nose piece mount  186 , which can be made of nylon for good flex, defines a threaded portion  188  that can engage with a nut  190 . Nose piece mount  186  can be securely attached to rotation tube  54  by passing the rotation tube through the nose piece mount, threading nut  190  onto portion  188 , and tightening the nut. Once tightened by nut  190 , nose piece mount  186  and rotation tube  54  rotate together. Rotation tube  54  also passes through nose piece  184 . Nose piece  184  and nose piece mount  186  snap fit together and define interlocking elements (not shown), e.g., slots and tabs, such that, once fitted together, the nose piece and the nose piece mount rotate together with rotation tube  54 . Nose piece  184  defines recesses  192  about its conical exterior to provide a good gripping surface by which to rotate rotation tube  54 . By rotating nose piece  184 , rotation tube  54  can be made to rotate. Further, the rotation can be continuous in a given direction because there is no wire that will bind or any other impediment to continued rotation.  
         [0146]    Proceeding distally of probe  36 , rotation tube  54  a stainless steel tube that is insulated, e.g., with a polymeric insulator such as a polyester, from about the distal end of left and right handles  118  and  119  to near the distal end of the rotation tube. The uninsulated portion of rotation tube  54  is used as a return electrode.  
         [0147]    At its distal end, wand  38  includes surgical tip  56 , e.g., a bipolar electrode, at the distal end of rotation tube  54 . FIG. 15 shows multiple embodiments of surgical tips, some of which will be described in detail below. Generally, the surgical tips are configured to provide a surgeon different access to different anatomical sites. For example, tips  215 ,  230 ,  400  and  500  may be particularly useful for angled or recessed sites, such as those encountered in shoulder surgery. Tips  215 ,  230 , and  400  are generally referred to as side-effect tips. A side-effect tip may be defined as a tip that includes an active electrode with a surface disposed radially from a longitudinal axis of the rotation tube  54  (or the surgical device, generally). Tip  500  is generally referred to as a beveled tip, and may also be referred to as a side-effect tip. Tips  300  and  350 , with electrodes at the end of the tips, may be particularly useful in knee surgery. Tips  300  and  350  are generally referred to as end-effect tips.  
         [0148]    Referring to FIGS.  16 - 16 F, a surgical tip  200  includes an electrically insulating, ceramic housing  202  and a formed wire electrode  204 . Housing  202  includes a grooved and notched portion  206  and an aspiration lumen  208 . Portion  206  is configured to engage with electrode  204  and to provide a textured surface having a formation that can be used, for example, to rasp tissue during use. Aspiration lumen  208  is in fluid communication with a lumen  210  defined by rotation tube  54  (FIG. 16C). Housing  202  is also configured to connect to an uninsulated portion  212  of rotation tube  54 , i.e., the return electrode. An insulated portion  213  is insulated with a shrink polyester insulator. Housing  202  and rotation tube  54  can be connected, e.g., by a ceramic adhesive. Housing  202  and rotation tube  54  are joined by a ceramic collar  214 , which acts as a spacer between the return electrode and electrode  204 , e.g., to minimize the possibility of arcing. In some embodiments, collar  214  and housing  202  can be integrally formed as one member.  
         [0149]    Electrode  204  is formed to engage with portion  206  of housing  202 . At one end, electrode  204  is connected to active conductor  182  by a stainless steel crimp connector  216 . The other end of electrode  204  terminates within and is surrounded by housing  202  to prevent a short circuit, e.g., if electrode  204  were to contact rotation tube  54 . A polyimide insulator  218  insulates active conductor  182 , crimp connector  216  and portions of electrode  204  (FIG. 16A). Electrode  204  is formed of tungsten wire and has a racetrack shaped loop with downwardly bent portions. At its distal end, electrode  204  curves down such that it is in fluid communication with lumen  208  (FIGS. 16C and 16D). As shown in FIGS. 16E and 16F, there are two cavities  250  in the surgical tip, one cavity  250  below each of the arms of electrode  204 . Surgical tip  200  is sized to be received within a joint and housing  202  has a length, L1, of about 0.2 inches, a width, W, of about 0.142 inches, and a height, H, of about 0.171 inches. Further, the exposed electrode wires have a length, L2, of about 0.153 inches, and are separated from return  212  by a length, L3, of about 0.075 inches.  
         [0150]    Referring to FIGS.  16 G- 16 K, a surgical tip  215 , which is similar to tip  200 , has no collar  214  and has a pin  220 . Pin  220  can be used to secure electrode  204  in place (FIG. 16J).  
         [0151]    Referring to FIGS.  17 - 17 D, a surgical tip  230  includes an electrically insulating, ceramic housing  232  and a tungsten electrode  234  formed by metal injection molding. Housing  232  includes a recessed portion  236  and an aspiration lumen  238 . Recessed portion  236  is configured to receive electrode  234 . Aspiration lumen  238  is in fluid communication with lumen  210  defined by rotation tube  54  (FIG. 17C). Housing  232  is also configured to engage with an uninsulated portion  240  of rotation tube  54 , i.e., the return electrode. Return electrode  240  may contain one or more cut-outs  260 .  
         [0152]    Electrode  234  is formed to engage with recessed portion  236 . Electrode  234  is formed with a sharp edge  235  that defines sharp ridges and/or grooves. The ridges and/or grooves are formations that help to create higher field intensities during use and can be used, for example, to rasp tissue during use. Electrode  234  is connected to active conductor  182  by engaging active conductor  182  to an opening  242  defined by the electrode. Active conductor  182  is surrounded by an insulator  244 , e.g., a shrink polyester, and portions of the active conductor and electrode  234  are surrounded by an insulator  246 , e.g., a polyimide.  
         [0153]    Referring to FIGS.  18 - 18 E, a surgical tip  300  includes an electrically insulating, ceramic housing  302  and a formed tungsten wire electrode  304 . Housing  302  includes a grooved and notched distal end  306  with a groove  308  configured to receive electrode  304 . The textured surface of distal end  306  provides formations that can be used, for example, to rasp tissue during use. The formations can be described as ridges or scallops, and have a curved top surface when viewed from the distal end. Groove  308  is in fluid communication with a suction tube  312 . At its proximal end, suction tube  312  is in fluid communication with suction tubing  46 . The thickness of groove  308  and the inner diameter of tube  312  are larger than the width of electrode  304  to provide a suction path into suction tube  312 . Housing  302  is also configured to engage with an uninsulated portion  212  of rotation tube  54 , i.e., the return electrode. In other implementations, tube  312  may be omitted or altered, using the lumen defined by rotation tube  54  and/or the pathway defined by groove  308  for suction, or eliminating suction altogether.  
         [0154]    Electrode  304  is formed to fit in groove  308  of housing  302 . At one end, electrode  304  is connected to active electrode  182 , e.g., by soldering, mechanically crimping, etc. The other end of electrode  304  is separated from the first end of the electrode by tube  312 . A shrink polyester insulator  314  surrounds active electrode  182 , and a polyimide insulator  316  surrounds portions of the active conductor and electrode  304 . Surgical tip  300  is sized to be received within a joint and housing  302  has a length, L1, of about 0.228 inches, a width, W, of about 0.166 inches, and a height, H, of about 0.092 inches. Further, to enable electrode  304  to contact tissue, electrode  304  extends beyond housing  302  by a length, L2, of about 0.009 inches.  
         [0155]    Referring to FIGS.  19 - 19 E, a surgical tip  350  includes an electrically insulating, ceramic housing  352  and a tungsten electrode  354  formed by metal injection molding. Housing  352  includes a grooved and notched distal end  356 . The textured surface of distal end  356  provides formations that can be used, for example, to rasp tissue during use. Housing  352  further defines an aspiration lumen  360  that is in fluid communication with a lumen  210  defined by rotation tube  54 . Housing  352  is also configured to engage with an uninsulated portion  212  of rotation tube  54 , i.e., the return electrode.  
         [0156]    Electrode  354  is configured to engage with and fit inside aspiration lumen  360 . Electrode  354  defines openings  362  that are in fluid communication with lumen  210  defined by rotation tube  54  to provide an aspiration path to suction tube  46 . During aspiration, aspirated material flows through openings  362 , pass recessed portions  364  defined by electrode  354 , and into lumen  210 . At its proximal end, electrode  354  is connected to active conductor  182  by hooking the active conductor through an opening  366  defined by the electrode. A shrink polyester insulator  368  surrounds active electrode  182 , and a polyimide insulator  370  surrounds portions of the active conductor and electrode  354 .  
         [0157]    Referring to FIGS.  20 - 20 D, a surgical tip  400  includes a housing  402 , a thermal band  404 , an active electrode  406 , e.g., tungsten, and an electrically insulating ceramic thermal pin  408 . Housing  402  is formed of an electrically conducting material, e.g., stainless steel, and is configured to engage with an uninsulated portion  212  of rotation tube  54 . Thus, in this embodiment, housing  402  and portion  212  act as the return electrode. Housing  402  also defines an aspiration opening  410  that is in fluid communication with lumen  210  defined by rotation tube  54 . Surgical tip  400  is sized to be received within a joint and housing  402  has a length, L1, of about 0.259 inches, electrode  406  has a width, W, of about 0.135 inches, and tip  400  has a height, H, of about 0.217 inches. Further, to provide a bipolar path, electrode  406  is separated from return  212  by a length, L2, of about 0.121 inches.  
         [0158]    Thermal band  404  is made of an electrically insulating material, e.g., a ceramic, and is disposed in housing  402 . Active conductor  182  (not shown), which is surrounded by a polyimide insulator  412 , extends along rotation tube  54  and up into thermal band  404 . An uninsulated portion  414 , e.g., bare copper wire, of active conductor  182  is fitted into a recess defined by thermal band  404 .  
         [0159]    Electrode  406  is a ring-shaped member having a top circumference with ridges and grooves, e.g., like the top of a rook piece in chess. The textured top surface of electrode  406  provides formations that can be used, for example, to rasp tissue during use. Referring to FIGS.  21 A-C, detailed views of electrode  406  include illustrative dimensions. Electrode  406  is sized to be received within housing  402  and has a height, H1, of about 0.025 inches. Electrode  406  is designed to provide points of plasma generation and has a height, H2, of about 0.01 inches, an angle, A1, of about sixty degrees, an angle, A2, of about thirty degrees, and an angle, A3, of about forty degrees.  
         [0160]    When assembled, thermal pin  408  and electrode  406  engage thermal band  404 , and a bottom portion of electrode  406  contacts portion  414  (FIG. 20C). To accommodate active conductor  182 , thermal pin  408  includes a cut away portion  414  that receives the active conductor (FIG. 20C).  
         [0161]    Referring to FIGS.  22 - 22 D, a surgical tip  450  includes an electrically insulating, ceramic housing  452 , an electrically conducting, e.g., stainless steel, connector  454 , an active electrode  456 , e.g., tungsten, and an electrically insulating, ceramic thermal pin  458 . Housing  452  is configured to engage an uninsulated portion  212  of rotation tube  54 , i.e., the return electrode. Housing  452  includes an aspiration opening  460  that is in fluid communication with lumen  210  defined by rotation tube  54 . Housing  452  also defines a top circumference  453  with ridges and notches that are formations that can be used, for example, to rasp tissue. The ridges on housing top surface  453  have a flat top, where the top is defined as in FIG. 22B. The formation of the top surface of electrode  456  can also be used to rasp tissue during use. Surgical tip  450  is sized substantially the same as surgical tip  400  in FIGS.  20 - 20 D.  
         [0162]    At its distal end, connector  454  defines a horseshoe-shaped portion  462  that rests on a surface  464  defined by housing  452  when electrode  450  is fully assembled. At its proximal end, connector  454  is connected to active conductor  182 . Portions of connector  454  and active conductor  182  within rotation tube  54  are electrically insulated, e.g., with a polyimide insulator as described above.  
         [0163]    Electrode  456  and thermal pin  458  are generally similar to electrode  406  and thermal pin  408 , respectively. When assembled, thermal pin  458  and electrode  456  engage with housing  452 , with a bottom portion of electrode  456  making good contact with connector  454  (FIG. 22C). To accommodate for connector  454 , thermal pin  458  defines a cut away portion  466  that receives the connector (FIG. 22C).  
         [0164]    Referring to FIGS.  23 - 23 D, a surgical tip  500  is similar, though not identical, to tip  400 . Tip  400  is angled about ninety degrees relative to the length of rotation tube  54 , whereas tip  500  is positioned at a non-ninety degree angle relative to the length of the rotation tube.  
         [0165]    Tip  500  generally includes an electrically conducting housing  502 , e.g., stainless steel, an electrically insulating, e.g., ceramic, thermal band  504 , an active, e.g., tungsten, electrode  508 , and an electrically insulating, e.g., ceramic, thermal pin  508 . Housing  502  is configured to engage with an uninsulated portion  212  of rotation tube  54  by a conductive, e.g., stainless steel, coupler  510 . In some embodiments, housing  502  and coupler  510  are integrally formed as one member.  
         [0166]    Thermal band  504  is configured to be disposed in housing  402 . Active conductor  182 , which is surrounded by a polyimide insulator  512 , extends along rotation tube  54  and up into thermal band  504 . An uninsulated portion  514 , e.g., bare copper wire, of active conductor  182  is fitted into a recess defined by thermal band  404 . Surgical tip  500  is sized to be received within a joint and has a length, L1, of about 0.32 inches, a width, W, of about 0.128 inches, and a height, H, of about 0.222 inches. Further, to provide a bipolar path, electrode  506  is separated from return  212  by a length, L2, of about 0.252 inches.  
         [0167]    Electrode  506  is a ring-shaped member having a top circumference with ridges and grooves, e.g., like the top of a rook in chess, which can be referred to as castleations. The textured top surface of electrode  506  provides formations that can be used, for example, to rasp tissue during use. FIGS.  24 A- 24 C show detailed views of electrode  506 . The dimensions are substantially similar to those in FIGS. 21B and 21C.  
         [0168]    When assembled, thermal pin  508  and electrode  506  engage with thermal band  504 , and a bottom portion of electrode  506  contacts portion  514  (FIG. 23C). To accommodate for active conductor  182 , thermal pin  508  defines a cut away portion  516  that receives the active conductor (FIG. 23C). Thermal pin  508  also defines an aspiration lumen  518  that is in fluid communication with lumen  210  defined by rotation tube  54 .  
         [0169]    Referring to FIGS.  25 - 25 C, rather than electrode  204  penetrating the aspiration lumen  208  (FIG. 16C), an electrode  2510  does not protrude into suction lumen  208 . Further, there are no cavities  250  below the arms of electrode  2510  (compare FIGS.  16 E- 16 F with FIGS. 25A and 25C).  
         [0170]    Referring to FIGS.  26 - 26 E, an electrode  2654  has a different shape than electrode  354  of FIG. 19A. Electrode  2654  can be metal injection molded and includes a distal tip  2610  with a groove  2612  that is a formation that can be used for rasping, and includes a proximal end  2614 . A housing  2652  has a different surface contour at the distal end than housing  352  of FIG. 19A. Housing  2652  has a formation  2670  that can be described as a groove, or as a ridge or an edge, and that provides rasping capability. Electrode  2654  does not define a suction lumen, in contrast to electrode  354  of FIG. 19A. Rather, suction is provided through a suction hole  2620  in a side of housing  2652 . Suction hole  2620  is in fluid communication with the interior of rotation tube  54  and proximal end  2614  of the electrode may be off-center to accommodate the fluid communication and/or desired wall thicknesses.  
         [0171]    Further, electrode  2654  connects to copper wire  182  using a crimp connector  2630 , rather than folding over wire  182  as in FIG. 19A. Crimp connector  2630  is mechanically crimped to both electrode  2654  and copper wire  182 . A polyimide insulator  2640  covers wire  182 , the crimp connector  2630 , and an exposed portion of electrode  2654 . Polyimide insulator  2640  can be inserted into housing  2652 , as shown in FIGS.  26 C- 26 D. Polyimide insulator  2640  can be further secured in housing  2652  by using an epoxy, for example a ceramic-based epoxy. An epoxy can be used to secure housing  2652  to rotation tube  54 .  
         [0172]    Referring to FIGS.  27 - 27 E, a connector  2710  can be made from phosphor bronze, which may be a better conductor than the stainless steel used for connector  454  in FIG. 22A. Further, connector  2710  includes a lead  2712  that connects to a distal end of a contact surface  2714 . Contact surface  2714  may contact an electrode  2716 . Lead  2712  makes an approximately ninety degree turn toward electrode  2716  near the bottom of a housing  2720 . Lead  2712  thus provides more clearance for suction hole  460  than that shown in FIG. 22C.  
         [0173]    Connector  2710  is connected to wire  182  using a crimp connector  2730  made of stainless steel. A polyimide insulator  2740  may be used to insulate all or part of wire  182 , crimp  2730 , and lead  2712 . As shown in FIG. 27C, insulator  2740  may cover lead  2712  up to the point where lead  2712  turns toward contact surface  2714 . An epoxy may also be used to retain connector  2710  and/or a thermal pin  2745  in place, and the epoxy may be applied, for example, distally up to the point where lead  2712  turns toward contact surface  2714 . FIG. 27D illustrates a particular implementation in which epoxy does not completely surround, that is, encircle the outer perimeter of, electrode  2716 , as indicated by reference numeral  2750 .  
         [0174]    Dimensions in the embodiment of FIGS.  27 - 27 E are substantially similar to the dimensions in FIGS.  20 - 20 D and  22 - 22 D. It can also be seen that the raised edges of electrode  2716  align with the low points of housing  2720 , in contrast to FIGS.  22 - 22 D in which the raised portions of electrode  456  align with raised portions of housing  452 .  
         [0175]    Referring to FIGS.  28 - 28 A, a keying tab  2810  is highlighted on a housing  2820  (see also FIG. 27A) for aligning an electrode. Keying tab  2810  may also align a connector (see connector  2710  in FIG. 27A). In housing  2820 , suction hole  460  is closer to the bend in the housing, as compared to housing  2720  in FIG. 27A. FIG. 28A shows female key slots  2830  on the bottom of an electrode  2840 .  
         [0176]    Referring to FIGS.  29 - 29 E, a connector  2910  is configured substantially similarly to connector  2710  in FIGS.  27 - 27 E, including the use of a crimp connector  2920  and a polyimide insulator  2930 . Connector  2910  provides a contact surface  2940  for contacting an electrode  2950 . Contact surface  2940  forms substantially a complete circle, providing almost three-hundred sixty degrees of contact. This is more than that provided in FIG. 23A by wire  514  contacting electrode  506  over approximately a ninety degree portion of a circle.  
         [0177]    As described for FIGS.  26 - 26 E and FIGS.  27 - 27 E, an epoxy may be used to secure connector  2910  to a housing  2955 . In a particular implementation, the epoxy is applied distally until is contacts a thermal pin  2960  and forms around an indented groove  2962  near the base of pin  2960 . In that implementation, the epoxy may wick up part of the outside surface of pin  2960 , but stops short of completely surrounding electrode  2950 , as shown by reference numeral  2970  in FIG. 29D. In one implementation, thermal pin  2960  is approximately 0.145 inches in length, the length being associated with the longest dimension.  
         [0178]    Electrode  2950  is similar to electrodes  2716 ,  2840  in FIGS.  27 - 27 E and FIG. 28A, and includes key slots on its bottom surface that align electrode  2950  in housing  2955 . The top surface of electrode  2950  is designed to provide high points  2970  at specified angles with respect to the geometry of scallops  2980  on housing  2955  and with respect to a return electrode  212 . In the embodiment of FIGS.  29 - 29 E, high points  2970  occur at approximately sixty degree intervals and align with the low points of scallops  2980 , and the shortest distance between electrode  2950  and return electrode  212  is L1, which is about 0.309 inches.  
         [0179]    High points  2970  may provide areas of higher current density, also referred to as concentrations of current density. The concentrations of current density facilitate creation of a vapor barrier and plasma generation from one or more points  2970  on electrode  2950 . The generation of a plasma is commonly referred to as light off. The electrodes of FIGS.  20 - 20 D,  21 A-C,  22 - 22 D,  23 - 23 D,  24 A-C,  27 - 27 E,  28 A, and  29 - 29 E include multiple high points that may each provide a location for light off. The other disclosed electrodes may also provide light off from various locations along the electrode depending on the design. Scallops  2980 , more particularly referred to as castleations, are utilized in several of the embodiments in this disclosure and are features that provide rasping capability. The embodiment of FIGS.  29 - 29 E is sized to be received in a joint and the dimensions are substantially similar to previous embodiments. The embodiment of FIGS.  29 - 29 E is designed to have a beveled tip with an angle, A, of about forty degrees.  
         [0180]    Referring to FIGS.  30 - 34 , there are shown various results from a finite element analysis of the surgical tips depicted in FIGS.  25 - 25 F, FIGS.  18 - 18 E, and FIGS.  27 - 27 E. The analysis models one or more electrical characteristics, such as, for example, electric field strength, voltage, current, or power, to determine probe configurations that provide desired design objectives. For example, design objectives can include, for a particular electrical characteristic, providing for (i) substantial uniformity around an electrode, (ii) a maximum value at a point above and to the outside of an electrode envelope, (iii) quick drop-off as a function of distance from an electrode, and (iv) quick drop-off as a function of tissue depth.  
         [0181]    Referring to FIGS.  30 - 31 , a model of the surgical tip of FIGS.  25 - 25 F, shown as atop view, looking at the face of the surgical tip through tissue, assumes that the wires of electrode  2510  (FIGS.  25 - 25 C) are buried in tissue to the surface of ceramic housing  202  (FIGS.  16 - 16 F), which is approximately the surface of electrode  2510 . The model also assumes that the surgical tip is immersed in a medical grade saline solution containing 0.9% saline. Thus, the region outside of the surgical tip is modeled as consisting of the saline solution. The plane of view can also be expressed in terms of an engagement angle. An engagement angle refers to the angle at which the surgical tip contacts tissue. In the present model, the engagement angle is perpendicular to the face of electrode  25 . 10 .  
         [0182]    The surgical tip of FIGS.  25 - 25 F is shown superimposed with isometric lines of constant electric potential (voltage). The potential is substantially uniform around the entire envelope of the electrode. The envelope of the electrode refers to the smallest rectangle, or other closed shape, that will enclose the electrode in the plane being viewed. In this case, the envelope is the smallest rectangle that will enclose both wires of the electrode in the plane being viewed. This feature allows a surgeon to effectively operate on tissue by providing relatively uniform electrical characteristics around the entire perimeter of the electrode.  
         [0183]    [0183]FIG. 30 also shows that the strength of the potential falls off to approximately half of its maximum value by {fraction (3/100)} of an inch from the electrode surface around the entire periphery of the envelope. The maximum is achieved at the top right corner of the electrode, and the entire periphery of the electrode is at substantially the maximum value. When the electric field strength falls off quickly after the tissue surface, it reduces the risk of burning tissue below the surface tissue that is of interest.  
         [0184]    Referring to FIG. 31, the electric field strength, measured in volts per thousandth of an inch (volts/mil), represents the gradient of the potential. The graph displays the electric field as a vector. The maximum electric field strength is outside of the envelope of the electrode, which facilitates operating on tissue by not having to center the tissue over the electrode in order to take advantage of the maximum electric field strength.  
         [0185]    Referring to FIG. 32, a model of the surgical tip of FIGS.  18 - 18 E is shown from a side view along a longitudinal cross-section down the middle of electrode wire  304 . The model assumes that electrode  304  is touching the tissue, indicated by a solid horizontal line  3210 . The model further assumes that the region below the tissue and outside of the surgical tip is the medical grade saline solution. The electric field strength at the tissue surface has dropped by more than 65% from a maximum value 3220. Within {fraction (3/100)} of an inch into the tissue, the strength of the electric field has fallen by more than 50% from the strength at the tissue surface and by more than 85% from the maximum value. The envelope of electrode  304  can be taken to be a rectangle having an upper edge at the line representing the tissue surface, and having two side edges coming down from the upper edge at approximately +/−60 mils on the x axis.  
         [0186]    Referring to FIGS.  33 - 34 , a model of the surgical tip of FIGS.  27 - 27 E is shown from a side view along a longitudinal cross-section down the middle of the surgical tip, similar to the view depicted in FIG. 27C. As indicated in FIG. 27B, the cross-section goes through a high point ( 2970  in FIG. 29A) of electrode  2716 , and through a low point on one of the scallops ( 2980  in FIG. 29A) on housing  2720 . In the model, the high point of the electrode is assumed to have penetrated tissue surface  3210  by approximately ten mils. The model further assumes that the region below the tissue and outside of the surgical tip is the medical grade saline solution.  
         [0187]    Referring to FIG. 33, at a tissue depth of approximately 30 mils, the potential has dropped by more than 40% from its maximum, which occurs along the surface of the high point that is labeled as “D.” At a tissue depth that is approximately 30 mils deeper than the high point, the potential has dropped by more than 45%, or almost half, from its maximum.  
         [0188]    Referring to FIG. 34, the electric field strength at a tissue depth of approximately 15 mils has fallen by more than 50% from a maximum 3410, which occurs just above housing  2720 . The electric field strength at a tissue depth of approximately 30 mils has fallen by more than 70% from its maximum. Maximum value 3410 occurs at a position that is above substantially all of the electrode, and at points above the high point, the electric field strength is at least approximately 70% of the maximum value. Being “above” the electrode refers to being away from the electrode surface in a favorable direction for contacting tissue. The electrode envelope extends from the left side of the graph to the right up to the edge of the electrode, which is at approximately 68 mils on the x axis.  
         [0189]    Modifications to the disclosed implementations can be made. For example, the features described for one or more of the disclosed surgical tips can generally be applied to other disclosed tips. Such features include, for example, electrode geometry and materials, housing geometry and materials, and aspiration techniques. For example, in some embodiments, probe  36  does not include a suction feature. As a further example, any of the disclosed tips may include one or more surfaces that have a formation for providing a mechanical rasping action against tissue.  
         [0190]    Such rasping action may be provided, for example, by a housing or an electrode. The housing or electrode may have a formation such as, for example, an elevated or depressed area, such as a deposit or pit, arising from, for example, (i) a manufacturing process using, for example, a mold, (ii) a chemical process that may etch a surface or leave a deposit, (iii) a coating or the addition of another material or object to the housing or electrode, or (iv) a mechanical process such as, for example, sanding or scraping. A formation may also include, for example, (i) an edge, (ii) a point, (iii) a groove, (iv) a ridge, (v) a scallop, (vi) a castleation, (vii) some other area of raised elevation with respect to another surface, (viii) a non-smooth surface contour, (ix) a surface roughened by, for example, a chemical or mechanical process, or (x) some other surface feature useful for rasping.  
         [0191]    The disclosed materials are only examples and other suitable materials may be used. For example, implementations may use an insulator that is not a polyimide and a housing that is not a ceramic. Insulating portions may also include an electrically non-conductive, refractory material.  
         [0192]    A number of implementations have been described. Nevertheless, it will be understood that various modifications can be made. Accordingly, other implementations are within the scope of the following claims.