Abstract:
An electrode assembly for an electrosurgical instrument, comprises a bipolar cutting blade, and fluid supply lines for directing a cooling fluid to the cutting blade, the cutting blade comprising first, second and third electrodes, and electrical insulators spacing apart the electrodes, the fluid supply lines being such that cooling fluid enters the cutting blade via the first electrode, passes through an aperture in the second electrode, and exits the cutting blade via the third electrode.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates to an electrode assembly for an electrosurgical instrument. Such instruments are commonly used for the cutting and/or coagulation of tissue in surgical intervention, most commonly in “keyhole” or minimally-invasive surgery, but also in “open” or “laparoscopic assisted” surgery.  
         [0002]     It is known to provide an electrosurgical instrument with a cooling system for prevention excess temperatures being developed at the electrode or electrodes. These fall into two categories. The first category includes instruments with a circulating cooling fluid. Examples are U.S. Pat. Nos. 3,991,764, 4,202,336, 5,647,871 and EP 0246350A. It should be noted that, with each of these systems, some or all of the fluid reservoir, pump and fluid supply lines are located externally of the electrosurgical handpiece. The second category includes instruments with heat pipes. Examples are U.S. 6,733.501. 6,544,264, 6,503,248, 6,206,876, and 6,074,389.  
       BRIEF SUMMARY OF THE INVENTION  
       [0003]     It is an aim of the present invention to provide an improvement over these prior art electrosurgical devices.  
         [0004]     Accordingly, there is provided an electrode assembly for an electrosurgical instrument, the electrode assembly comprising a bipolar cutting blade, and fluid supply lines for directing a cooling fluid to, and from, the cutting blade, the cutting blade comprising first, second and third electrodes, and electrical insulators spacing apart the electrodes, the fluid supply lines being such that cooling fluid enters the cutting blade via the first electrode, passes through an aperture in the second electrode, and exits the cutting blade via the third electrode.  
         [0005]     The cutting blade preferably comprises three electrodes in a sandwich structure with insulting layers therebetween. In a preferred arrangement the electrode assembly is as described in our co-pending published patent application EP 1458300.  
         [0006]     Preferably, one or both of the first and third electrodes includes a lumen though which the cooling fluid is constrained to flow. According to one convenient arrangement, one or both of the first and third electrodes comprises a hollow structure, the inside of the hollow structure defining the lumen though which the cooling fluid is constrained to flow.  
         [0007]     In this way, the cooling fluid is in intimate contact with the electrode assembly, especially the outer electrodes which are used for the coagulation of tissue. Cooling of the electrodes is particularly advantageous in the coagulation of tissue, as the coagulation power that can be used is otherwise limited by the rise in temperature of the electrodes. If the temperature of the electrodes is allowed to rise, tissue and dried blood will start to adhere to the electrodes, limiting the effectiveness thereof. This problem generally limits the available coagulation power of such electrodes, and cooling allows higher power and/or the longer use of coagulation electrodes without the temperature of the electrode reaching a level at which matter adhering becomes a problem.  
         [0008]     The invention further provides an electrosurgical instrument comprising a handpiece, a bipolar cutting blade secured to the handpiece, and fluid supply lines for directing a cooling fluid to, and from, the cutting blade, the cutting blade comprising first, second and third electrodes, and electrical insulators spacing apart the electrodes, the fluid supply lines being such that cooling fluid enters the cutting blade via the first electrode, passes through an aperture in the second electrode, and exits the cutting blade via the third electrode.  
         [0009]     Preferably, the housing also contains a reservoir of cooling fluid, and a pump for driving the cooling fluid through the supply lines. The cooling fluid is an electrically non-conductive fluid, typically deionised water or ethanol. A non-conductive fluid is required because the fluid is in intimate contact with each of the electrodes, and would therefore provide leakage current pathways if it were electrically conductive.  
         [0010]     Having the pump and fluid reservoir within the handpiece provides the advantages of a circulating cooling fluid system, without the requirement for additional coolant lines and equipment external to the instrument handpiece. The handpiece can be supplied together with a reservoir of cooling fluid, or alternatively this can be assembled within the handpiece immediately prior to the instrument being used. In a preferred arrangement the housing also contains a reservoir of cooling fluid, and there are two possible arrangements for the fluid reservoir, a first arrangement in which the reservoir is not connected to the fluid supply lines, and the second arrangement being in which the reservoir is connected to the fluid supply lines. In this way, the instrument can be supplied with all of the necessary components, and yet the reservoir need not be connected to the supply lines until the instrument is ready for use. This minimises the risk of contamination of the cooling fluid or the corrosion of other components by the fluid, thereby increasing the acceptable shelf-life of the instrument.  
         [0011]     In one convenient arrangement the housing is such that the reservoir is movable between first and second positions, the first position being in which the reservoir is not connected to the fluid supply lines, and the second position being in which the reservoir is connected to the fluid supply lines. In this way, the fluid reservoir can be moved into position, e.g. by a sliding movement, either when the instrument is manufactured, or alternatively immediately prior to the first use of the instrument.  
         [0012]     The pump is preferably driven by an electric motor, typically a synchronous motor. In one convenient arrangement, the electric motor constitutes the pump. The motor conveniently includes a spindle on which is provided a paddle, the paddle being rotated by the action of the motor. The rotation of the paddle causes the cooling fluid to be driven though the fluid supply lines. Other types of pump, including those known for use with electronic equipment such as computers, may be suitable for use with this electrosurgical instrument.  
         [0013]     The invention further provides an electrosurgical system comprising a bipolar cutting blade, a handpiece to which the cutting blade is secured, an electrosurgical generator for supplying a radio frequency voltage signal to the cutting blade, fluid supply lines for directing a cooling fluid to, and from, the cutting blade, and a pump for driving cooling fluid through the fluid supply lines, the cutting blade comprising first, second and third electrodes, and electrical insulators spacing apart the electrodes, the fluid supply lines being such that cooling fluid enters the cutting blade via the first electrode, passes through an aperture in the second electrode, and exits the cutting blade via the third electrode. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which,  
         [0015]      FIG. 1  is a schematic diagram of an electrosurgical system including an electrode assembly constructed in accordance with the present invention;  
         [0016]      FIGS. 2 and 3  are views, shown partly in section, of a handpiece forming part of the electrosurgical instrument of  FIG. 1 ;  
         [0017]      FIGS. 4 and 5  are sectional views of an alternative embodiment of handpiece forming part of the electrosurgical instrument of  FIG. 1 ;  
         [0018]      FIG. 6  is an enlarged sectional view of part of the handpiece of  FIGS. 4 and 5 ;  
         [0019]      FIG. 7  is a perspective view of an electrode assembly forming part of the electrosurgical instrument of  FIG. 1 ;  
         [0020]      FIG. 8  is a perspective view, shown partly in section, of the electrode assembly of  FIG. 7 ;  
         [0021]      FIG. 9  is a schematic sectional plan view of the electrode assembly of  FIG. 7 ; and  
         [0022]      FIGS. 10A  to  10 F are perspective views showing the electrode assembly of  FIG. 7  is various stages of assembly. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]     Referring to  FIG. 1 , a generator  10  has an output socket  10 S providing a radio frequency (RF) output for an electrosurgical instrument  12  via a connection cord  14 . Activation of the generator  10  may be performed from the instrument  12  via a connection cord  14 , or by means of a footswitch unit  16 , as shown, connected to the rear of the generator by a footswitch connection cord  18 . In the illustrated embodiment, the footswitch unit  16  has two footswitches  16 A and  16 B for selecting a coagulation mode and a cutting mode of the generator  10  respectively. The front panel of the generator  10  has push buttons  20  and  22  for respectively setting parameters such as the coagulation and cutting power levels, which are indicated in a display  24 . Push buttons  26  are provided as an alternative means for selection between coagulation and cutting modes.  
         [0024]     The instrument  12  comprises a handpiece  1 , a shaft  2  and an electrode assembly  3  mounted at the distal end of the shaft. Referring to  FIG. 2 , the handpiece  1  comprises a hollow housing  53 , in which is located a fluid reservoir  4 , a motor  5 , and a connection block  6 . Referring also to  FIG. 6 , the motor  5  includes a spindle  7 , and a paddle wheel  8  attached to the spindle and located in a chamber  9  within the connection block  6 . The connection block  6  also includes an inflow needle  11  and an outflow needle  13 . The fluid reservoir  4  is slidable within the housing  53 , between the position shown in  FIG. 2  and that of  FIG. 3 , in which the inflow and outflow needles  11  and  13  pierce a diaphragm  15  present on the end face  17  of the fluid reservoir.  
         [0025]      FIGS. 4 and 5  show an alternative version of the handpiece  1 . In the handpiece  1  of  FIGS. 4 and 5 , the fluid reservoir  4  is introduced through an aperture  19  in the rear face  21  of the housing  53 .  FIGS. 4 and 5  also show a fluid feed line  23  and a fluid return line  25 , which were omitted from  FIGS. 2 and 3  for reasons of clarity. The fluid feed line  23  runs from the chamber  9 , through the shaft  2 , to the electrode assembly  3 . The inflow needle  11  is in communication with the chamber  9 , while the outflow needle  13  is in communication with fluid return line  25  at a section  27  of the connection block  6 . The fluid return line  25  runs from the connection block  6 , through the shaft  2 , to the electrode assembly  3 .  
         [0026]     Referring to  FIG. 6 , the paddle wheel  8  is located in the chamber  9 , and is mounted on the spindle  7 , which spindle extends through a sealing membrane  28 . The membrane  28  prevents cooling fluid from the chamber  9  entering the motor  5 .  
         [0027]     The electrode assembly  3  will now be described with reference to FIGS.  7  to  9 . At the centre of the electrode assembly is a flat active electrode  30 , with insulating mouldings  31  and  32  on either side thereof. The insulating mouldings  31  and  32  are both part of an integrated moulding assembly  33 . The insulating moulding  31  includes wall portions  34  defining a hollow space  35  therein, while the insulating moulding  32  has similar wall portions defining a hollow space  36 . The moulding  31  is provided with an opening  37  connecting the hollow space  35  with the fluid feed line  23 , while the moulding  32  is provided with a similar opening connecting the hollow space  36  with the fluid return line  25 .  
         [0028]     The mouldings  31  and  32  are covered by electrically-conductive shells  38  and  39 , constituting return electrodes for the electrode assembly  3 . The active electrode  30  is provided with a through hole  40 , connecting the hollow spaces  35  and  36  beneath the return electrodes  38  and  39 . The electrode assembly  3  is in the form of a hook arrangement, with a recess  41  provided in one side thereof.  
         [0029]     The assembly of the above construction will now be described with reference to  FIGS. 10A  to  10 F.  FIG. 10A  shows the active electrode  30 , formed by stamping from stainless steel. The stamped active electrode  30  has the through hole  40  formed therein, along with additional holes  42  provided for fastening purposes. The stamping also has ears  43 , which are removed at the end of the manufacturing process, but which are provided for materials handling purposes.  
         [0030]      FIG. 10B  shows heat-shrink material  44  added to the proximal portion of the active electrode  30 . The active electrode  30  is then assembled into the integrated moulding assembly  33 , as shown in  FIG. 10C . The insulating moulding assembly  33  is formed of ceramic, or alternatively silicone rubber. The electrically-conductive shells  38  and  39  are formed of copper (see  FIG. 10D ), and are assembled on to the moulding assembly  33  by welding them on to the metallic fluid feed and return lines  23  and  25  respectively (see  FIG. 10E ). The completed assembly is shown in  FIG. 10F , prior to the removal of the ears  43 .  
         [0031]     The operation of the instrument  12  is as follows. If not already in position, the fluid reservoir  4  is moved into location with the connection block  6 , as shown in  FIGS. 3 and 5 . The instrument  12  is connected to the generator  10 , and introduced into the surgical site. The footswitch  16  is operated in order to supply an electrosurgical RF voltage to the electrodes  30 ,  38  and  39  in order to cut or coagulate tissue at the surgical site. The operation of the electrodes  30 ,  38  and  39  is described in more detail in our published application EP 1458300, but in essence when electrosurgical cutting is required a cutting voltage is supplied between the cutting electrode  30  and one or both of the return electrodes  38  and  39 . Alternatively, when electrosurgical coagulation is required, a coagulating voltage is supplied between the return electrodes  38  and  39 . In a blended mode, a blended waveform typically consisting of a waveform rapidly alternating between the cutting and coagulating voltage is supplied, typically also rapidly alternating between the cutting and coagulating electrodes  30 ,  38  and  39 . For clarity, the leads connecting the RF signal between the cord  14  and the electrode assembly  3  have been omitted, but the fluid feed and return lines  23  and  25  could be formed of an electrically-conductive material and used for this purpose.  
         [0032]     When the footswitch  16  is depressed, a signal is also sent to the motor  5  which causes the spindle  7  and hence the paddle wheel  8  to rotate. The rotation of the paddle wheel  8  causes cooling fluid to be driven out of the chamber  9  and through the fluid feed line  23 . The cooling fluid is typically an electrically non-conductive fluid such as deionised water or ethanol. The cooling fluid travels though the fluid feed line  23  along the shaft  2  to the hollow space  35  within the return electrode  38 . Once within the hollow space  35 , the cooling fluid travels through the active electrode  30  by means of the through hole  40 , and into the hollow space  36  within the other return electrode  39 . From the hollow space  36 , the cooling fluid travels back along the shaft  2  by means of the fluid return line  25  and into the reservoir  4  via the outflow needle  11 .  
         [0033]     The circulating cooling fluid travels to, and from, the electrode assembly  3 , coming into close contact with both return electrodes  38  and  39  and cooling them accordingly. By cooling the return electrodes  38  and  39 , more electrical energy can be transferred into the tissue for coagulation purposes without the electrodes reaching a temperature at which tissue and blood will start to adhere to the electrode surfaces. It is essential that the cooling fluid is substantially electrically non-conductive, as it may come into contact with the active electrode  30  and with the return electrodes  38  and  39 .  
         [0034]     The motor  5  can be run continuously, or can be switched in and out whenever the electrode assembly  3  is actuated. In may be advantageous to run the motor  5 , and hence circulate the cooling fluid, whenever the electrode assembly  3  is actuated, and for a predetermined additional time thereafter. In this way, any residual heat within the electrodes  30 ,  38  and  39 , or transferred to the electrodes from adjacent hot tissue, will be removed by the cooling fluid.  
         [0035]     It will be appreciated that the instrument  12  provides a handpiece  1  containing the fluid reservoir  4  and all of the fluid lines, and the only external lead is the connection cord  14  for the RF signal. This connection cord  12  can also be used for the electric supply to the motor  5 . Alternatively, the RF signal can also be used as a supply for the motor  5 . Heat is removed from the electrode assembly  3  by the cooling fluid, which is deposited back into the reservoir  4 , and dissipated through the housing  53 . For all normal operations of the instrument  12 , the temperature rise of the housing  53  is only a few degrees, and still comfortable for the user of the instrument to hold.  
         [0036]     By cooling the electrodes  30 ,  38  and  39 , particularly during the coagulation of tissue, greater coagulative power can be applied without the overheating of the electrodes. Tissue sticking and the coating of the electrodes  30 ,  38  and  39  with dried blood are factors limiting the coagulative power of un-cooled instruments, and the present invention provides a compact and versatile instrument with considerable coagulative capabilities. In addition, the instrument, possibly even including the connection cord  14 , can be made disposable, by the use of relatively-inexpensive components therein.  
         [0037]     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.