Electrosurgical apparatus and methods for ablating tissue

Abstract

Electrosurgical methods and apparatus for the controlled ablation of tissue from a target site of a patient. The instrument includes a shaft having a proximal and distal end portion and an active electrode on the distal end portion, a return electrode arranged on the shaft spaced from the active electrode, at least one electrical connector extending through the shaft that connects the active electrode with a high frequency power supply, and at least one fluid delivery port adapted to deliver fluid across the active electrode and an aspiration lumen within the shaft having a distal opening that aspirates the fluid.

1 . An electrosurgical instrument for removing tissue from a target site within or on a patient's body comprising: 
 a shaft having a proximal and distal end portion and an active working area on the distal end portion, said active working area comprising at least one active electrode;    a return electrode arranged on the shaft spaced from the working area;    at least one electrical connector extending through the shaft that connects the active electrode with a high frequency power supply;    at least one fluid delivery port and in fluid communication with an electrically conductive fluid source, said fluid delivery port adapted to direct fluid at said active working area; and    a suction working area spaced from said active working area and positioned on a lateral surface of said shaft, said suction working area comprising at least one aspiration port such that fluid is transported across the active electrode as the fluid exits said fluid delivery port and enters said aspiration port.    
   
   
       2 . The instrument of  claim 1  wherein the at least one fluid delivery port comprises a plurality of fluid delivery ports.  
   
   
       3 . The instrument of  claim 1  wherein the active electrode is a screen electrode and is disposed on a lateral side of the shaft.  
   
   
       4 . The instrument of  claim 1  further comprising an electrically insulating support member upon which the active electrode is mounted to, the support member comprising an inorganic material.  
   
   
       5 . The instrument of  claim 4  wherein the support member has an axial opening in communication with the aspiration lumen, and a lateral opening in contact with the active electrode.  
     electrically conductive fluid, the active electrode is positioned between the return electrode and the tissue structure and the electrically conductive fluid completes a conduction path between the active electrode and the return electrode.  
   
   
       7 . The instrument of claim  6  wherein the active and return electrodes are configured, upon the application of a sufficiently high frequency voltage therebetween, to vaporize the fluid in a thin layer over at least a portion of the active electrode and to induce the discharge of energy from the vapor layer.  
   
   
       8 . The instrument of  claim 1  wherein said active electrode is coupled to said shaft and to said electrical connector with a plurality of electrical coupling members.  
   
   
       9 . The instrument of  claim 2  wherein said plurality of fluid delivery ports comprises at least eight fluid delivery ports.  
   
   
       10 . The instrument of  claim 9  wherein said fluid delivery ports are circumferentially spaced about the working area.  
   
   
       11 . The instrument of  claim 1  wherein said active electrode is at least one loop electrode.  
   
   
       12 . The instrument of  claim 4  further comprising a cap arranged on the distal end portion of the shaft wherein said cap comprises an opening that receives said insulating support.  
   
   
       13 . The instrument of  claim 12  wherein said cap is electrically conductive and forms a portion of the return electrode.  
   
   
       14 . A method for treating target tissue comprising removing said target tissue using an electrosurgical instrument comprising the steps of: 
 providing an instrument comprising at least one active electrode on a distal end of a shaft, a return electrode spaced a distance from said active electrode, at least one aspiration port, and at least one fluid delivery port;    delivering fluid through said fluid delivery port across said active electrode and into said aspiration port;    applying a voltage difference across the active and return electrode to vaporize fluid in a thin layer surrounding said active electrode; and    positioning said active electrode and said vapor layer in contact or close proximity to said target tissue whereby said applying step volumetrically removes said tissue wherein said active electrode covers in part said aspiration port.    
   
   
       15 . The method of  claim 14  wherein said target tissue is within a joint.  
   
   
       16 . The method of  claim 15  wherein said tissue is selected from the group consisting of meniscus, synovial tissue, and articular cartilage.  
   
   
       17 . The method of  claim 14  wherein said aspiration port comprises a plurality of discrete ports proximal of said active electrode.  
   
   
       18 . The method of  claim 14  wherein said active electrode comprises a plurality of loop electrodes.  
   
   
       19 . The method of  claim 14  wherein said active electrode comprises a wire screen having a plurality of apertures.  
   
   
       20 . A method for treating target tissue comprising removing said target tissue with an electrosurgical instrument comprising the steps of: 
 flowing electrically conductive fluid from a plurality of fluid delivery ports, across an active electrode and into an aspiration port in the vicinity of the active electrode;    applying a voltage difference between the active electrode and a return electrode to create a current path through said fluid and between said active electrode and the return electrode spaced proximal of said active electrode; and    positioning the active electrode in proximity of the tissue such that the tissue is removed and wherein said active electrode is adapted to prevent tissue fragments from clogging and wherein said active electrode is one of a wire screen, a wire loop, and a set of wire loops.