An interface joint 120 integrates into a single cable assembly 154 (i) a fluid feed 150, (ii) a needle movement mechanism, and (iii) a coaxial cable for conveying RF and/or microwave energy to an electrosurgical device for cutting and coagulating. An electrically insulating housing has a QMA connector 144 to receive an electromagnetic signal and a port 152 to receive saline, arranged as Y-connector. The combined limb may form a first limb 140 of a second Y-connector 126, the first limb 138 of which contains a push rod 130 which is moved by a slider 136 to deploy or withdraw a needle at the distal end of the cable assembly. A coax cable 142, a fluid pathway and the push rod all exit the handle through an outlet 146 into a multi-lumen cable assembly 154, with optional strain relief (156, figure 1). Also disclosed is an electrosurgical tip (figures 8 and 9) and a torque transfer device (figures 4A and 4B) which may be combined with the interface joint into a single assembly (figure 6).