A mains electricity (AC-powered) unit that generates a high frequency electrical current used in an ultrasonic osteosynthesis system. The current is converted, typically within an electrode handpiece, into a high frequency mechanical oscillation (ultrasonic vibration) to produce friction and heat for the implantation (welding) of a resorbable fixation pin in a surgically-drilled bone tunnel. The energy produced by the device may be regulated through a foot-pedal.