Abstract:
One surgical device includes a first member and a second member defining a lumen for receiving the first member. The first member is configured to be movable relative to the second member to cut tissue. An electrical connector is physically and electrically coupled to the second member, to electrically couple the second member to a source of electricity. A tension device holds a distal region of the first member in electrical contact with a distal region of the second member. The first member includes a blade used both to cut tissue mechanically, and to coagulate cut tissue. The blade is electrically conductive and serves as an active electrode in a bipolar arrangement with a return electrode. Electrical energy is transferred to the blade through a point contact at a distal tip of the first and second members.

Description:
TECHNICAL FIELD 
   A disclosed embodiment relates generally to arthroscopic surgery, and more particularly to a hand-held arthroscopic instrument providing an electrically conductive blade for mechanical cutting and electrosurgery. 
   BACKGROUND 
   Arthroscopic instruments can be used to cut tissue mechanically in various parts of a body, such as, for example, a knee, using a blade that is rotated, or otherwise brought into contact with the tissue to be cut. Arthroscopic instruments are also known that include a monopolar or bipolar electrode configuration for coagulating tissue using radio frequency (“RF”) energy. 
   SUMMARY 
   A described embodiment provides an arthroscopic or endoscopic instrument having a blade that is used both to cut tissue mechanically and to coagulate the cut tissue. The blade is electrically conductive and serves as an active electrode in a bipolar arrangement with a return electrode located nearby on the instrument. The blade is rotated to cut the tissue mechanically, yet no brush is used to transfer electrical energy to the rotating blade. Instead, electrical energy is transferred to the blade through contact between distal tips of a non-rotating tube and a concentric rotating tube containing the blade. 
   According to one aspect, a surgical device includes a first member, a second member, an electrical connector, and a tension device. The second member defines a lumen for receiving the first member, the first member and second member being configured to be movable relative to each other to cut tissue. The electrical connector is physically and electrically coupled to the second member, the electrical connector being configured to electrically couple the second member to a source of electricity. The tension device is for holding a distal region of the first member in electrical contact with a distal region of the second member. 
   Embodiments of this aspect may include one or more of the following features. 
   The electrical connector is self-centering on the second member. The second member includes a tube and the electrical connector includes a three-point connector that is self-centering on the tube. 
   A third member is physically coupled to the second member and electrically isolated from the distal region of the first member. A first electrode is in electrical contact with the distal portion of the first member; the third member includes a second electrode; and the surgical device is operable as a bipolar electrosurgical device using the first and second electrodes. The first member includes a first tube, the second member includes a second tube that is cylindrical, and the third member includes a third tube disposed about the second tube. An exposed surface area of the second electrode is at least approximately five times larger than an exposed surface area of the first electrode. 
   An electrode is in electrical contact with the distal portion of the first member, and the surgical device is operable as a monopolar electrosurgical device using the electrode. The electrode is part of the first member. 
   The tension device holds a tip of the first member in electrical contact with a tip of the second member. The first member defines a longitudinal axis and the tension device applies tension along the longitudinal axis of the first member. The tension device includes a spring. A lock is physically coupled to the second member for coupling the second member to the tension device. A drive unit is coupled to the first member to move the first member relative to the second member, wherein the second member is fixed with respect to the drive unit. 
   The first member includes an electrically conductive cutting surface configured to cut tissue mechanically and to perform electrosurgery. The cutting surface includes a blade or a burr. The electrosurgery includes coagulation. The second member includes a cutting surface configured to cut tissue mechanically in cooperation with the electrically conductive cutting surface of the first member. A portion of the cutting surface of the second member is electrically conductive and is configured to perform electrosurgery along with the cutting surface of the first member. The cutting surfaces of the first member and the second member are configured to be moved past each other and to cut tissue mechanically that is disposed between the two cutting surfaces as the two cutting surfaces are moved past each other. The second member includes an electrically insulating cutting surface configured to cut tissue mechanically in cooperation with the electrically conductive cutting surface of the first member. 
   The first member is configured to be rotated relative to the second member to cut tissue. The first member includes a first tube, and the second member includes a second tube that is cylindrical. The first member defines an inner lumen operable as an aspiration lumen. 
   The first member is substantially electrically insulating, and the first member includes an electrically conductive material at the distal portion of the first member. The second member is substantially electrically insulating, and includes an electrically conductive material at the distal portion of the second member. 
   A drive unit is coupled to the first member to move the first member relative to the second member, and the second member is fixed with respect to the drive unit. A first electrode is in electrical contact with the distal portion of the first member, and the first electrode includes a cutting surface configured to cut tissue mechanically and to perform electrosurgery. A second electrode is physically coupled to the second member and electrically isolated from the distal region of the first member, and the distal region of the first member includes a tip of the first member and the distal region of the second member includes a tip of the second member. 
   According to another aspect, performing surgery includes inserting a surgical device into a body. The surgical device includes a first member and a second member, and the second member defines a lumen for receiving the first member. The first member and the second member are moved relative to each other to cut tissue. A distal region of the first member is held in electrical contact with a distal region of the second member. Electrical power is provided to the first member through the second member. 
   Embodiments of this aspect may include one or more of the following features. 
   A distal tip of the first member is maintained in electrical connection with a distal tip of the second member. Inserting the surgical device includes inserting a surgical device having an inner cutting surface on the first member and an outer cutting surface on the second member. Moving the first member and the second member relative to each other includes cutting tissue in the body using the inner cutting surface and the outer cutting surface. Providing electrical power includes performing electrosurgery on the cut tissue using the inner cutting surface. 
   Moving the first member and the second member relative to each other includes rotating the first member relative to the second member, such rotating causing the inner cutting surface to pass by the outer cutting surface and causing tissue disposed between the two cutting surfaces to be cut mechanically. A conductive environment is provided in the body, and inserting the surgical device into the body includes inserting the inner cutting surface into the conductive environment. Performing electrosurgery includes performing bipolar electrosurgery using the inner cutting surface as an electrode. Inserting the surgical device includes inserting a surgical device that includes a third member coupled to the second member and including a return electrode. 
   According to another aspect, a surgical device includes a first member, a second member, and an electrical connector. The second member defines a lumen for receiving the first member, and the first member and the second member are configured to be movable with respect to each other to cut tissue. The electrical connector is physically and electrically coupled to the second member for electrically coupling the second member to a source of electricity. The surgical device includes a mechanism for holding a distal region of the first member in electrical contact with a distal region of the second member. 
   Described instruments allow tissue to be cut mechanically and coagulated with a single instrument, and the tissue can be cut and coagulated with the same surface of the instrument. Because the same surface can be used, the mechanical cutting and electrosurgery can also occur at approximately the same time. The instruments can perform other electrosurgery on tissue with or without also mechanically cutting tissue, and the electrosurgery can be monopolar or bipolar. In one instrument including an inner tube rotating within a second tube, electrical power is coupled to an electrode on the inner tube through contact at the distal end of the instrument between the inner and second tubes. 
   The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the description, the drawings, and the claims. 

   
     DESCRIPTION OF DRAWINGS 
       FIG. 1  is a side view of an embodiment of the surgical device, along with block diagrams for equipment connected to the surgical device. 
       FIG. 2  is an exploded view of the surgical device of  FIG. 1 , separately showing an electroblade and a motor drive unit (“MDU”). 
       FIG. 3  is a perspective view of the electroblade of  FIG. 2 , also including a complete RF power cord. 
       FIG. 4A  is a side view of the MDU of  FIG. 2  with a distal portion shown in cross-section. 
       FIG. 4B  is an enlarged view of a portion of the cross-section of  FIG. 4A . 
       FIG. 4C  is an enlarged view of a portion of  FIG. 4B  showing a tension device in greater detail. 
       FIG. 5  is a cross-sectional side view of an outer tube assembly of the electroblade of  FIG. 2B . 
       FIG. 6A  is a side view of a middle tube assembly of the electroblade of  FIG. 2 . 
       FIG. 6B  is a bottom view of a proximal portion of the middle tube assembly of  FIG. 6A , taken along line  6 B— 6 B in  FIG. 6A . 
       FIG. 7A  is a side view of an inner tube assembly of the electroblade of  FIG. 2 . 
       FIG. 7B  is a cross-sectional view of a proximal portion of  FIG. 7A . 
       FIG. 8A  is an enlarged view of a distal portion of the electroblade of  FIG. 2 . 
       FIG. 8B  is a top view of the distal portion of the electroblade, taken along line  8 B— 8 B in  FIG. 8A . 
       FIG. 8C  is the top view of  FIG. 8B  without an inner tube. 
       FIG. 9A  is a side view of the power cord of  FIG. 3  showing a portion in cross-section that connects to the electroblade. 
       FIG. 9B  is an enlarged view of a portion of the cross-section of  FIG. 9A , shown in the same orientation as  FIG. 9A  and positioned so that the openings for the electroblade in  FIGS. 9A and 9B  are aligned. 
       FIG. 9C  is a top view of a portion of  FIG. 9B  showing the electrical connection for an outer tube, taken along line  9 C— 9 C in  FIG. 9B , shown in a complimentary orientation relative to  FIGS. 9A and 9B , and positioned on a line between the openings for the electroblade in  FIGS. 9A and 9B . 
       FIG. 9D  is a bottom view of a portion of  FIG. 9B  showing the electrical connection for a middle tube, taken along line  9 D— 9 D in  FIG. 9B , shown in the same orientation as FIG.  9 C, and positioned on an extension of the line between the openings for the electroblade in  FIGS. 9A and 9B . 
       FIG. 10  is a top view of an alternate embodiment of the electrical connections of  FIGS. 9C and 9D . 
       FIG. 11A  shows an alternate embodiment of a connector for providing electrical connections to an electroblade. 
       FIG. 11B  shows another alternate embodiment of a connector for providing electrical connections to an electroblade. 
       FIG. 11C  shows an alternate embodiment of an electroblade using the electrical connector of  FIG. 11B . 
       FIG. 12  is an enlarged view of a distal portion of an alternate embodiment of the electroblade of  FIG. 2  having a serrated cutting surface. 
       FIG. 13  is an enlarged view of a distal portion of another alternate embodiment of the electroblade of  FIG. 2  having a closed-ended return electrode. 
       FIG. 14  is a side view of an alternate embodiment of the power cord of  FIG. 9A  showing a different generator connector. 
       FIG. 15  is a side view of an alternate embodiment of an electroblade including a burr. 
   

   DETAILED DESCRIPTION 
   Referring to  FIG. 1 , a surgical system  100  includes a surgical device  110  having a motor drive unit (“MDU”)  112  mechanically coupled to an electroblade  114 . Surgical device  110  also includes a RF bipolar power cord  116  electrically and mechanically coupled to electroblade  114  for supplying RF power to electroblade  114 . Surgical system  100  further includes a control box  120  for supplying power to MDU  112  through a power cord  130 , and a RF generator  140  for supplying RF power to electroblade  114  through RF power cord  116 . 
   Referring to  FIG. 2 , MDU  112  includes an aspiration tube  210  and an aspiration control  220 . Aspiration tube  210  is coupled to a suction pump or other device to provide aspiration of tissue and fluid. Electroblade  114  includes an opening  225  that extends radially through electroblade  114  and communicates with aspiration tube  210  for aspiration. Electroblade  114  includes a distal portion  230  that is inserted into a patient&#39;s body to cut tissue mechanically and to perform electrosurgery. 
   Electroblade  114  includes a ridge  240  for connecting electroblade  114  to MDU  112 . Ridge  240  is deflected radially inward when electroblade  114  is inserted into MDU  112  and ridge  240  retracts slightly (radially outward) when ridge  240  comes into alignment with a corresponding surface (not shown) in MDU  112 . Ridge  240  thus engages the surface, attaching electroblade  114  to MDU  112 . Electroblade  114  also includes a release  250  for releasing electroblade  114  from MDU  112 . Pressing release  250  deflects ridge  240  radially inward disengaging ridge  240  from the groove, and allowing electroblade  114  to be withdrawn from MDU  112 . Electroblade  114  further includes a tab  260  that is rotated by MDU  112 . Commercial implementations of MDU  112  are available from Smith &amp; Nephew, Inc., of Andover, Mass., in part numbers 7205354, 7205355, and 7205971. 
   Referring to  FIG. 3 , RF power cord  116  terminates at a free end with a connector  320 . Connector  320  has two prongs  322  and  324  designed to connect to either a generator or a foot switch. Each prong connects to one of two separate conductors within RF power cord  116  to provide both a supply path and a return path for electroblade  114 . 
   Referring to  FIGS. 4A–4C , MDU  112  includes a drive shaft terminating at a distal end in a pair of parallel prongs  410 , only one of which is visible in cross-section. Tab  260  of electroblade  114  fits between prongs  410 , and prongs  410  rotate tab  260  as the drive shaft is rotated. MDU  112  includes a tension device  420  that applies pressure to electroblade  114  when electroblade  114  is secured in MDU  112 . As best shown in  FIG. 4C , tension device  420  is, for example, a coil spring, that applies pressure generally along a longitudinal axis, X, of MDU  112  and electroblade  114 .  FIG. 4C  shows the cross-section of the coils. Tension device  420  may also or alternatively include, for example, a compression spring (coil or otherwise); other types of springs, such as, for example, a leaf spring; an elastic device, such as, for example, a rubber grommet or a device made of an elastic plastic material; or a nozzle or other structure that provides fluid pressure, such as, for example, air pressure, rather than structural pressure. 
   Referring to  FIG. 8A , a distal tip of electroblade  114  includes an inner tube  710 , a middle tube  610 , a middle tube insulating layer  620 , an outer tube  510  having a distal exposed portion  540 , and an outer tube insulating layer  520 . The three tubes  510 ,  610 , and  710  are concentric. 
   Referring to  FIG. 5 , an outer tube assembly  500  includes electrically conductive outer tube  510  covered by outer tube insulating layer  520  on all but a proximal portion  530  and distal portion  540 . An electrode is defined by exposed distal portion  540  of outer tube  510 , and this electrode is referred to as the return electrode as explained in detail below. 
   Outer tube  510  defines a lumen  545  and an opening  550  at a distal end in communication with lumen  545 . Outer tube assembly  500  also includes an outer tube hub  560 . Outer tube hub  560  includes an outer tube connector  570  for electrically connecting one of the conductors in RF power cord  116  to exposed proximal portion  530  of outer tube  510 . Outer tube hub  560  also includes a middle tube connector  580  for electrically connecting the second conductor in RF power cord  116  to an exposed portion of middle tube  610 . Connectors  570  and  580 , and their connections, are further explained in the discussion of  FIGS. 9A–9D . Outer tube hub  560  further includes a cavity  590  and, at a portion extending proximal to cavity  590 , release  250  and ridge  240  (described above). Note that outer tube  510  does not extend proximally of exposed proximal portion  530 , and that no tube is located in cavity  590  in  FIG. 5 ; rather, cavity  590  includes markings on the interior wall of cavity  590  that resemble the outline of a tube. 
   Outer tube assembly  500  has an approximate length for dimension L 1  of, for example, 6.4 inches, and an approximate length for dimension L 2  of, for example, 5.9 inches. These dimensions are not critical to operation and can vary depending on, for example, the location of the body tissue on which surgical device  110  is to operate. 
   Referring to  FIGS. 6A ,  6 B,  8 A, and  8 B, a middle tube assembly  600  includes electrically conductive middle tube  610  covered by middle tube insulating layer  620  on all but a proximal portion  630  and a distal portion (labeled as  610  in  FIG. 8A ). Middle tube  610  defines a lumen  635  and an opening  640  at a distal end in communication with lumen  635 . Opening  640  is bounded by a sharp edge  820  for cutting ( FIG. 8B ) that is part of the exposed distal portion ( 610  in  FIG. 8A ) not covered by insulating layer  620 . Middle tube  610  also includes a distal portion  645  that is rounded, a straight portion  646 , and an inside surface  647  ( FIG. 6B ). A tangent line  648  shows the demarcation between distal rounded portion  645  and straight portion  646 . Middle tube assembly  600  includes a middle tube hub  650  including a distal portion  652  and a proximal portion  654 . Middle tube assembly  600  also includes a cavity  656  in a proximal end  660 . 
   Middle tube assembly  600  is fixed to outer tube assembly  500 , such that both assemblies  500  and  600  are stationary. That is, neither assembly  500  or  600  is rotated by MDU  112 . Middle tube  610  and insulating layer  620  are positioned inside of outer tube  510  and protrude past distal opening  550  of outer tube  510 , as shown in  FIG. 2B , to electrically isolate outer tube  510  from middle tube  610 . Middle tube connector  580  contacts exposed portion  630  of middle tube  610  to provide an electrical connection to middle tube  610 . Distal portion  652  of middle tube hub  650  fits inside cavity  590  of outer tube hub  560 . Proximal portion  654  abuts cavity  590  and includes a cut-out  670  ( FIG. 6B ) that surrounds ridge  240  and release  250  as shown in  FIG. 2B . 
   Middle tube assembly  600  has an approximate length for dimension L 3  of, for example, 7.5 inches, and an approximate length for dimension L 4  of, for example, 6.0 inches. These dimensions are not critical to operation and can vary depending on, for example, the location of the body tissue on which surgical device  110  is to operate. 
   Referring to  FIGS. 7A and 7B , an inner tube assembly  700  includes electrically conductive inner tube  710  and an inner tube hub  720  having a distal portion  722  and a proximal portion  724 . Inner tube  710  is not covered by an insulating layer, and a distal portion serves as an electrode as described in detail below. Inner tube  710  defines an aspiration lumen  728  and includes an opening  730  in communication with aspiration lumen  728 . Opening  730  is bounded by a sharp edge (labeled  810  in  FIG. 8B ) for cutting. A proximal end  740  of aspiration lumen  728  is in communication with opening  225 , as shown in  FIG. 7B . 
   Inner tube assembly  700  can be rotated by MDU  112  while middle tube assembly  600  and outer tube assembly  500  remain stationary. Inner tube  710  is positioned inside of middle tube  610 . As explained earlier, tension device  420  applies longitudinal pressure. The pressure applied by tension device  420  causes a distal rounded portion  750  of an outer surface  760  of inner tube  710  to abut distal portion  645  of inner surface  647  of middle tube  610  ( FIG. 8B ), thereby making electrical contact. Distal portion  722  of inner tube hub  720  fits inside of cavity  656  in proximal end  660  of middle tube assembly  600 . Proximal portion  724  is exposed, as seen in  FIG. 2B . In addition, or alternatively, electrical contact can be made between outer surface  760  of a straight portion  770  of inner tube  710  and inner surface  647  of straight portion  646  of middle tube  610 . Note that a tangent line  780  (see  FIGS. 7A and 8A ) shows the demarcation between distal rounded portion  750  and straight portion  770 . Such contact between straight portions  646  and  770  may be only incidental, not providing a reliable electrical connection, such that the distal tip connection provides the primary electrical connection between middle tube  610  and inner tube  710 . 
   Inner tube assembly  700  has an approximate length for dimension L 5  of, for example, 7.0 inches. This dimension is not critical to operation and can vary depending on, for example, the location of the body tissue on which surgical device  110  is to operate. 
   Referring again to  FIG. 8A , middle tube  610  and middle tube insulating layer  620  extend past uninsulated distal portion  540  of outer tube  510  to provide electrical isolation between middle tube  610  and outer tube  510 . Inner tube  710  extends into opening  640  in middle tube  610  to expose a portion of inner tube  710  for use as an electrode and a cutting instrument. Opening  730  in inner tube  710  is shown facing up (in  FIG. 8A ), in the same direction as opening  640 . Because the entire part of inner tube  710  that is visible in opening  640  has had a portion removed to form opening  730 , inner tube  710  appears to have a disproportionately small diameter compared to the diameter of middle tube  610 . 
   Referring to  FIGS. 8B and 8C , opening  730  in inner tube  710  is partially bounded by an uninsulated cutting edge  810  of inner tube  710 . Edge  810  bounds the two sides and a distal perimeter  815  of opening  730 . Opening  640  in middle tube  610  is completely bounded by the uninsulated oval-shaped cutting edge  820  of middle tube  610 . Proximal to edge  820  is a crescent-shaped exposed portion  825  of middle tube  610 , and surrounding both edge  820  and the crescent-shaped exposed portion of middle tube  610  is an oval-shaped beveled edge  830  of middle tube insulating layer  620 .  FIG. 8C  provides a more isolated view of edges  820  and  830  and crescent-shaped exposed portion  825 . In summary, the uninsulated exposed surfaces include edge  810  of inner tube  710  which provides an edge for mechanical cutting and electrosurgery, edge  820  of middle tube  610  which provides an edge for mechanical cutting, and crescent-shaped exposed portion  825 . Alternatively, no portion of middle tube  610  between edge  830  and edge  820  need be uninsulated. For example, middle tube insulating layer  620  can cover all of the distal portion of middle tube  610  except for approximately 0.02 inches around opening  640  used for edge  820 . As stated above, edge  820  is uninsulated to allow edge  820  to be unimpeded during mechanical cutting. Because edge  820  is uninsulated, edge  820  also serves as part of an electrode, however such use is incidental and typically forms a small part of the electrode as explained in more detail below. 
   As inner tube assembly  700  ( FIG. 7 ) is rotated by prongs  410  ( FIG. 4 ) engaging tab  260  ( FIGS. 2B and 3 ), edge  820  of middle tube  610  ( FIG. 8B ) works cooperatively with edge  810  of inner tube  710  ( FIG. 8B ) in a scissors-like cutting action to cut tissue disposed between edges  820  and  810 . Tissue can be drawn between edges  820  and  810  with the aid of aspiration through opening  640  in middle tube  610  and opening  730  in inner tube  710 . 
   Inner tube assembly  700  can be rotated continuously or intermittently in either a forward or a reverse direction, or oscillated in both directions. The direction of rotation, the speed of rotation, the timing of oscillations between the two directions, the torque control, and other variables can be varied as appropriate for a given application. Inner tube  710  can be locked in one position by MDU  112  to prevent rotation of inner tube  710 , and a locking position can be selected. These and other variables can be controlled at MDU  112  using, for example, hand controls, such as, for example, pushbuttons. Variables also can be controlled at, for example, control box  120  or a hand switch or foot switch positioned between control box  120  and MDU  112 . 
   As mentioned earlier, a first electrode is defined by the exposed distal portions of inner tube  710  and, incidentally, middle tube  610  that contact tissue. These exposed portions include a variable portion of inner tube  710  that is visible through opening  640 , and that part of middle tube  610  forming edge  820  and the crescent-shaped exposed portion  825  proximal to edge  820 . The portion of inner tube  710  visible through opening  640  is variable because inner tube  710  can be rotated. The first electrode has a proximal portion  840 , a middle portion  850 , and a distal portion  860 , as shown in  FIGS. 8A and 8B . 
   A second electrode is defined by exposed distal portion  540  of outer tube  510 . A circuit is completed between the two electrodes by immersing both electrodes in a conductive environment. A conductive environment can be produced, for example, from a 9% normal saline solution, or from Ringers lactate, a physiologically compatible conductive solution. The conductive solution also can serve as an irrigant and to distend a body cavity. In practice, the circuit typically also extends through tissue that is positioned adjacent the first electrode. 
   The second electrode has a surface area that is approximately five times larger than the surface area of the first electrode, and the greater surface area allows for a lower current density at the second electrode than at the first electrode. Specifically, when inner tube  710  is fully closed, the surface area of the second electrode is five times larger than the exposed surface area of inner tube  710 . The ratio is larger when inner tube  710  is in another position, such as, for example, only three-fourths closed. The ratio is minimally affected when the exposed surface area of middle tube  610  is considered as part of the first electrode. 
   The current density at the first electrode is further increased at sharp edge  810  of inner tube  710 . The higher current density at the first electrode generally gives rise to a tissue effect being seen on tissue adjacent or near the first electrode and not on tissue adjacent or near the second electrode. Tissue effects include, for example, coagulation and shrinkage and the term electrosurgery encompasses electrical surgery that achieves these or other tissue effects. 
   Electrical energy can be applied to tissue using one of the first or second electrodes, and electrical energy can return to electroblade  114  through the other of the two electrodes. Accordingly, either electrode can act as an active electrode or as a return electrode. However, for simplicity, the first electrode is referred to as the active electrode and the second electrode is referred to as the return electrode. 
   Referring to  FIG. 9A , one end of RF power cord  116  includes a connector  910  that provides electrical connections to middle tube  610  and outer tube  510 , and ultimately to the active and return electrodes. Connector  910  forms part of outer tube hub  560  and, along with outer tube hub  560 , is fixed to outer tube  510  and middle tube  610 . 
   Referring to  FIG. 9B , connector  910  includes outer tube connector  570 , middle tube connector  580 , and a housing  920 . Outer tube connector  570  includes an upper tab  932  and three lower tabs  934  (see also  FIG. 9C ). Similarly, middle tube connector  580  includes an upper tab  936  and three lower tabs  938  (see also  FIG. 9D ). Housing  920  defines a conductor channel  940  through which two RF conductors  942  and  944  are passed from power cord  116  to connectors  570  and  580 . Conductor  942  couples to tab  932  of connector  570 , and conductor  944  couples to tab  936  of connector  580  to provide power to tabs  932  and  936 . 
   Housing  920  also defines a tube channel  950 , through which one or more tubes and/or insulating layers are fixed during assembly. In an assembled electroblade, middle tube  610 , middle tube insulating layer  620 , and outer tube  510  each are fixed within tube channel  950 . Tube channel  950  has varying diameters to accommodate the various tubes and insulating layers. 
   Referring to  FIG. 9C , outer tube connector  570  is generally described as a three-sided connector and/or a three-point connector. Connector  570  is self-centering on outer tube  510 . That is, because connector  570  has three tabs  934  distributed around outer tube  510  that contact tube  510 , connector  570  tends to position itself such that outer tube  510  is centered within connector  570 . 
   Referring to  FIG. 9D , middle tube connector  580  is similar to connector  570 . The diameter of tube channel  950  is smaller at the opening surrounded by connector  580  than at the opening surrounded by connector  570  because the diameter of middle tube  610  is smaller than the diameter of outer tube  510 . 
   RF power is applied to electroblade  114  using generator  140  and RF power cord  116  ( FIG. 1 ). As explained earlier, connector  320  ( FIG. 3 ) is connected to generator  140  directly or through a foot switch. One prong  322  (or  324 ) electrically connects both middle tube  610  and inner tube  710  to the generator using middle tube connector  580  ( FIG. 9D ). RF power is transferred from middle tube  610  to inner tube  710  principally through distal portions  645  and  750  of tubes  610  and  710 , respectively ( FIGS. 5 ,  8 A, and  8 B). The other prong  324  (or  322 ) electrically connects outer tube  510  to the generator using outer tube connector  570  ( FIGS. 5 and 9C ). 
   By applying RF power during a mechanical cutting operation, the RF power can be used, for example, to coagulate tissue as the tissue is cut mechanically. RF power also can be applied when no mechanical cutting operation is taking place in order, for example, to coagulate previously cut tissue. If no mechanical cutting is desired, inner tube  710  can be locked in a particular position, such as, for example, a position that “closes” or obscures three-fourths of opening  640  in middle tube  610 . A three-fourths-closed position exposes additional surface area of inner tube  710  to provide a greater area, for example, for coagulation, and still provides a one-fourth opening for aspiration. Inner tube  710  can be locked by setting MDU  112  so that prongs  410  do not allow rotation. 
   Electroblade  114  is designed to coagulate tissue at the active electrode, and not to ablate tissue under normal operating conditions which are discussed below. The relative surface areas of the active and return electrodes, and the use of formations (for example, edges) both promote coagulation by controlling current density, as discussed above. The inter-electrode distance has also been designed to facilitate coagulation. The return electrode of electroblade  114  is closest to the active electrode at approximately the middle  850  of the active electrode, and the return electrode is farthest from the active electrode at the proximal end  840  of the active electrode. Such spacing has been found to provide a current density appropriate for coagulation. 
   Design parameters and/or operating conditions can be varied to provide coagulation capability in different embodiments. For example, design parameters such as the relative surface areas of the two electrodes, the types of formations on the electrodes (for example, edges), and the distance between the active and return electrodes can be varied to affect current densities. The current density tends to be greatest where the inter-electrode distance is smallest, and where there are formations, such as, for example, edges, that concentrate current. As a further example, operating conditions such as the power level for coagulation can be varied depending on, for example, the surface area of the electrodes and the amount of tissue being cut. 
   The RF power that is applied can be controlled using, for example, generator  140 , a foot switch or other foot-operated control, and a hand switch or other hand-operated control including controls integrally mounted in MDU  112  or electroblade  114 . RF power controls can be provided for parameters, such as, for example, the type and/or shape of the RF waveform, the level of power, the direct current (“DC”) bias, and the duration of the RF power. RF control also can include temperature detection and feedback using, for example, a thermocouple or thermistor that is integrally mounted in electroblade  114 . Frequencies outside of the RF band also can be used. 
   Referring to  FIG. 10 , in an alternative embodiment of a connector for connecting electrical power from a conductor in cable  116  to a tube, such as, for example, tube  510 ,  610 , or  710 , a connector  1010  includes three contacts  1020  and is generally described as a five-sided connector and/or a three-point connector (as opposed to the three-sided connector of  FIGS. 9A–9D ). The use of five sides, compared to three, has the effect of flattening the curves associated with connectors  570  and  580  and allowing a reduction of the dimension L 6 , and a consequent reduction of the required size of connector  910  and outer tube hub  560 . As with connectors  570  and  580 , connector  1010  is self-centering on, slidable along, and rotatable around either outer tube  510  or middle tube  610 . Connectors can have various numbers of sides and/or contacts depending on, for example, the desired dimensions of the connector or the desired current density at any given contact. 
   Connector  1010  has an approximate length for dimension L 6  of, for example, 0.26 inches. This dimension is not critical to operation and can vary depending on, for example, the diameter of the concentric tubes  510 ,  610 , and  710 . 
   Referring to  FIG. 11A , in an alternative embodiment of a connector for connecting electrical power from a conductor in cable  116  to a tube, such as, for example, tube  510 ,  610 , or  710 , a connector  1110 A provides an electrical connection to electroblade  114 . Connector  1110 A includes a conductor  1120 A in the form of a flexible metal conductor that operates as a leaf spring to make contact at a distal portion  1130 A with a tube. 
   Referring to  FIG. 11B , in another alternative embodiment of a connector for connecting electrical power from a conductor in cable  116  to a tube, such as, for example, tube  510 ,  610 , or  710 , a connector  1110 B includes a conductor  1120 B in the form of a flexible metal conductor that operates as a compression spring to make contact at a distal portion  1130 B with a tube. 
   Referring to  FIG. 11C , a device  1140  shows connector  1110 B coupling to a tube at an angle such that distal portion  1130 B makes a reliable contact with the tube. Such contact can be with a stationary tube, such as, for example, outer tube  510  or middle tube  610 , or with a moving tube, such as, for example, inner tube  710 . Connectors  1110 A and  1110 B can include two or more conductors  1120 A and  1120 B, respectively, to provide connections, for example, for an active electrode and a return electrode. Although contact can be made with a moving tube along a straight portion of the tube, such contact would not enjoy the benefits and advantages of providing electrical contact at a distal end of the tubes as described herein. 
   Referring to  FIG. 12 , in an alternative embodiment of inner tube  710 , a distal portion  1210  of an electroblade similar to electroblade  114  includes an inner tube  1220  with a serrated, or toothed, edge  1230  surrounding opening  730 . Serrated edge  1230  is particularly useful in cutting tissue that is described variously as being ligamentous, banded, or rubbery. Other types of edges can be employed to surround opening  730 , depending, for example, on the particular application. Due to the angle of the view, a portion  1240  of middle tube insulating layer  620  appears to cover part of opening  640 , however, opening  640  does continue to a top  1250  of middle tube  610 , as in  FIGS. 6A ,  8 A, and  13  (below). 
   Referring to  FIG. 13 , in an alternate embodiment of outer tube  510 , a distal portion  1305  of an electroblade similar to electroblade  114  includes a closed-ended outer tube  1310  that extends distally past a straight portion  646  of middle tube  610  and curves around to partially cover distal rounded portion  645  of middle tube  610 . Closed-ended outer tube  1310  provides a smaller inter-electrode distance, d, at distal portion  860  of middle tube  610  than does outer tube  510  (compare  FIG. 8A ). The smaller inter-electrode distance is a result of a distal rounded portion  1330  of outer tube  1310 . Note that distance “d” is shown for simplicity as a linear measurement in  FIG. 13 , however, the true distance traversed can be a curved line. Although outer tube  510  and closed-ended outer tube  1310  can be used in various configurations of electroblade  114 , closed-ended outer tube  1310  has found particular application in embodiments using larger diameter concentric tubes. For example, outer tube  510  is particularly applicable where the diameter of the outer tube is approximately 4.5 millimeters, and closed-ended outer tube  1310  is particularly applicable where the diameter of the outer tube is approximately 5.5 millimeters. The closer inter-electrode distance at distal portion  860  is useful in the 5.5 millimeter implementation to provide a higher current density at distal portion  860  and, as a result, provide for coagulation at distal portion  860  without increasing power substantially. Variations of closed-ended outer tube  1310  can cover more or less of middle tube  610 , including covering more or less of rounded distal portion  645 . Such variations will affect the inter-electrode distance at different locations along the electrodes and, as a result, will affect the current density at those locations. 
   Referring to  FIG. 14 , RF power cord  116  can include an integral connector  1410  for connecting power cord  116  to a Vulcan Generator produced by Oratec Interventions, Inc. of Menlo Park, Calif., now owned by Smith &amp; Nephew, Inc. Vulcan connector  1410  includes a resistor (not shown) that allows the Vulcan Generator to identify the attached instrument as an electroblade and to provide a pre-programmed output to the electroblade. 
   Referring again generally to  FIG. 1 , control box  120  is, for example, the Dyonics® Power Shaver system or the Dyonics® EP-18 Shaver System supplied by Smith &amp; Nephew, Inc. of Andover, Mass. Generator  140  is a commercially available generator such as, for example, a Vulcan Generator or a Valleylab Electrosurgical Generator Force FXTM, Force FXTM-C, or ForceTM 2, supplied by Valleylab, a division of Tyco Healthcare Group L.P., of Boulder, Colo. Various embodiments are easily integrated into a standard operating room because (i) the mechanical and RF operations, as well as aspiration, are performed with the same instrument, (ii) a standard operating room generator can be used, and (iii) no grounding pad is necessary. 
   Typical generator settings are between zero and seventy watts for coagulation, with the generator allowing settings up to one-hundred watts. Typical settings for use with an inner tube and cutting surface that are stationary include minimum coagulation settings of between twenty and forty watts, and recommended coagulation settings of between thirty and fifty watts. Such settings are used, for example, when inner tube  710  is locked in a position closing off three-fourths of opening  640  in middle tube  610 . If the inner tube is moving, thus providing simultaneous mechanical cutting and RF electrosurgery, typical minimum power settings for coagulation range from thirty to fifty watts, and recommended coagulation power settings range from fifty to seventy watts. 
   The generator provides, for example, waveforms having an open circuit maximum peak-to-peak voltage of 800 volts with no load. Typical settings on one of the Valleylab generators include both 320 volts peak-to-peak and 750 volts peak-to-peak, with a maximum peak-to-peak voltage of 1000 volts. Frequency settings typically range from approximately 470–510 kilohertz (“kHz”) for a sinusoidal wave, with a nominal setting of 500 kHz. 
   The electroblade is sized to accommodate the desired application. For example, for use in a shoulder the electroblade is sized differently from one for use in a prostate. Applications include, for example, use in a shoulder, a knee, and other joints, as well as use in natural orifices such as, for example, a uterus, a urethra, a nasal cavity, and a mouth. 
   The electroblade assembly is designed as, for example, a single-use, sterile, disposable assembly. Alternatively, the electroblade is a multiple-use assembly that can be cleaned and re-sterilized. Single-use assemblies obviate the need to clean between the tubes and may be made using materials, such as, for example, plastics, that cannot be steam re-sterilized, thereby preventing multiple uses. Conversely, device components, such as, for example, outer tube  510  and middle tube  610 , need not be fixed to outer tube hub  560 , thus allowing such components to be more amenable to cleaning. 
   Referring again to  FIG. 2B , electroblade  114  can be attached to MDU  112  using various other structures, for example, threaded connections and pressure-fit connections. Various embodiments of MDU  112  include motor drive units manufactured by Smith &amp; Nephew, Inc., of Andover, Mass., such as, for example, part numbers 7205354, 7205355, and 7205971. 
   Referring again generally to  FIGS. 5–7 , outer tube connector  570  and middle tube connector  580  can clip onto outer tube  510  and middle tube  610 , respectively, or slide over one of the ends of tube  510  or  610 . The outer tube connector and the middle tube connector can contact outer tube  510  and middle tube  610 , respectively, in various ways including, for example, by using an electrically conductive clip, an electrically conductive leaf spring, or a solder connection. 
   Outer tube insulating layer  520  and middle tube insulating layer  620  are, for example, heat shrinkable tubing that is placed over outer tube  510  or middle tube  610 , respectively, then shrunk and trimmed to desired dimensions, or a halar coating having a thickness of, for example, 0.009 inches or more. Other embodiments may use materials that are, for example, painted, sprayed, or deposited on one or more surfaces (for example, interior and exterior) of a tube. Materials include, for example, ceramics, plastics, and silicone. Other embodiments may use one or more insulating layers that are not secured to a tube. Non-secured insulating layers may be made from plastic or ceramic, for example. Further, middle tube insulating layer  620  may be on the inner surface of outer tube  710  rather than, or in addition to, middle tube  610 . 
   The various tubes and insulating layers can be selected to facilitate energy transfer. The inner and middle tubes can be coated, for example, to expose only the edge of the cutting surfaces and the bearing surfaces, thereby focusing energy and facilitating electrosurgery. Further, the bearing surfaces of tubes, such as, for example, the interior and exterior of the tubes, need not be exposed and can be, for example, coated with silicone. The tubes themselves need not be metal, or entirely conductive. For example, the inner tube can be plastic with a conductor at a distal end to make electrical contact with the middle tube and to provide conductive cutting edges where contact is made with tissue. Such an embodiment reduces metal exposed to any saline fluid and concentrates energy. As another example, a plastic middle tube can be used having a conductive strip, metal or otherwise, between the distal end and the proximal connection to RF power cord  116 . As a further example, an inner tube can be non-conductive, although it still may have a cutting edge, and the active electrode is provided by the middle tube having a conductive cutting edge. As yet another example, one embodiment does not use a middle tube, but instead uses a brush mechanism to make electrical contact between a rotating inner tube and a connector from an RF power cord. Such a brush embodiment also may include a middle tube that is not conductive and that has a cutting edge that mates with a cutting edge on the inner tube. 
   The electroblade can be a monopolar instrument without an outer tube. Whether monopolar or bipolar, embodiments may provide electrosurgery at the surface that provides mechanical cutting or at another surface. 
   As described earlier, electrical contact between the inner and middle tubes is reliably maintained using a spring or other tensioning device, such as, for example, a coil spring, a leaf spring, or a rubber grommet or other elastic material that is coated, if desired, with a lubricant. Regardless of the tension device, physical contact between inner tube  710  and middle tube  610  can occur across various surface areas and/or points of contact. For example, the location and extent of contact can depend on the shapes of the distal ends of tubes  610  and  710  (for example, flat or rounded, and, if rounded, the relative radii of curvature) and the size and location of openings  640  and  730 . 
   Electrical contact between tubes  610  and  710  can be provided by, for example, (i) providing physical contact along some part of the longitudinally extending walls of tubes  610  and  710 , (ii) designing and machining tubes  610  and  710  with small (tight) tolerances so that an electrical connection is maintained during rotation without the use of an additional tensioning device, (iii) having a conductive solution fill some of the space between tubes  610  and  710 , or (iv) using a conventional brush and slip ring mechanism. 
   The various references to a brush being used to provide electrical contact between middle tube  610  and inner tube  710  do not suggest that a brush would enjoy all of the benefits of the present invention. Rather, a brush is mentioned to provide another example of a manner of providing electrical contact. A brush, and other known techniques of providing electrical contact, may be used in conjunction with advantageous features disclosed herein. 
   Other motions can be used to perform mechanical cutting, such as, for example, a reciprocating motion. Electrical contact in a reciprocating embodiment can be maintained by using, for example, tight tolerances, a flexible wire, or a brush and slip-ring mechanism. 
   A variety of cutting surfaces can provide mechanical cutting. Such surfaces include, for example, blades that are curved, burred, straight, serrated, or miniature. Mechanical cutting is typically achieved with speeds in the thousands of cycles (for example, revolutions or reciprocations) per minute. Further, embodiments need not have cutting surfaces on both inner tube  710  and middle tube  610 , for example, only inner tube  710  includes a cutting surface and opening  640  in middle tube  610  does not have a sharp edge. 
   Referring to  FIG. 15 , an electroblade distal portion  1510  includes a burr  1520  at a distal end  1525  of an inner tube or shaft  1530 . Burr  1520  protrudes from a lumen opening  1535  at a distal end  1540  of a middle tube  1550 . Proximal to burr  1520 , inner tube  1530  includes a shoulder  1555  with a tapered surface  1560 . Middle tube  1550  includes a tapered surface  1565  configured to contact tapered surface  1555  of inner tub  1530 . MDU  112  can be used to apply longitudinal pressure on inner tube  1530  so that tapered surfaces  1555  and  1565  contact each other and transfer electrical power from middle tube  1550  to inner tube  1530 , and eventually to burr  1520 . As  FIG. 15  shows, cutting surfaces, such as, for example, a burr, can be provided on an inner tube that has a distal shoulder portion that engages the middle tube under the pressure of a tension device and provides electrical contact with the middle tube and electrical energy to the cutting surface. 
   A resistive element can be used to provide heat energy for coagulation. Embodiments may be designed to operate in a non-conductive environment with both electrodes configured to touch the tissue to be treated. 
   A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made. For example, features of the above-described embodiments generally may be combined in ways not discussed and other features or variations not discussed also may be used. Accordingly, other embodiments are within the scope of the following claims.