Electrosurgical instrument and an electrosurgery system including such an instrument

An electrosurgical instrument for treating tissue immersed in an electrically conductive fluid with radio frequency energy in the frequency range of from 100 kHz to 50 Mhz, wherein the instrument comprises an elongate shaft configured to be mounted at a proximal end to a handpiece and carrying at its distal end a bipolar electrode assembly which includes:

• an active electrode with an active zone at a distal end of the active electrode;
• and
• a return electrode with a return zone near the active zone;
• wherein at least one of the active and return zones has an electrically insulating dielectric covering such that in use a radio frequency electrical circuit between the active and return electrodes through the conductive fluid is completed at least primarily by dielectric coupling through the dielectric covering.

An electrosurgical system for treating tissue structure contained within a body cavity and immersed in an electrically conductive fluid, said system comprising:

• a generator for delivering a radio frequency output for the treatment of tissue structures in the high to very high frequency range;
• and
• an electrode assembly connected to said generator, said electrode assembly comprising:
• an active electrode including an active zone at a distal end of said active electrode;
• a return electrode including a return zone defined by an electric field developed between said active electrode and said return electrode when said electrode assembly is connected to said radio frequency output of said generator;
• and
• an insulator separating said return electrode from said active electrode;
• said return zone being coated with a layer of dielectric insulating material wherein, in use, said return zone is insulated from direct electrical contact with said tissue and said electrically conductive fluid so that an electrical circuit is completed between said active and return zones by dielectric coupling through said dielectric insulating material.

An electrode assembly for treating tissue structure contained within a body cavity and immersed in an electrically conductive fluid, said electrode assembly being connected to a generator for delivering a radio frequency output for the treatment of tissue structures in the high to very high frequency range, said electrode assembly comprising:

• an active electrode including an active zone at a distal end of said active electrode;
• a return electrode including a return zone defined by an electric field developed between said active electrode and said return electrode when electrode assembly is connected to said radio frequency output of said generator;
• and
• an insulator separating said return electrode from said active electrode;
• said return zone being coated with a dielectric insulating material layer wherein, in use, said return zone is insulated from direct electrical contact with said tissue and said electrically conductive fluid so that an electrical circuit is completed between said active and return zones by dielectric coupling through said dielectric insulating material.