Electrosurgical apparatus for delivering RF and/or microwave energy into biological tissue

An electrosurgical instrument for delivering radio frequency and/or microwave energy to biological tissue has a distal end assembly 214 with a planar active tip 224 (two opposing electrode surfaces separated by a dielectric) with an electrically conductive protective hull 222. The hull has a smoothly contoured convex undersurface, is bio-compatible and preferably has low coefficient of friction with biological tissue; it may be of stainless steel and induction soldered to the lower electrode surface of tungsten or titanium, optionally augmented by gold or silver in the contact region. A recess 249 may be provided in the hull to hold a solder preform. The hull protects underlying tissue, electrically connects a coaxial feed line 142 to the active tip, and may house a retractable needle (234, figure 5) for fluid injection. The distal end assembly may be attached to a braided cannula tube 216 enabling torque transfer, the attachment being via a short section of flexible unbraided tube 218 providing a soft tip.