An electrode-like device attached to a dedicated ultrasonic osteosynthesis system handpiece used to apply high frequency mechanical oscillation (ultrasonic vibration) to a resorbable fixation pin on a surgically-drilled bone tunnel. The ultrasonic vibration is used to create friction and then heat so that the pin will flow into the tunnel and solidify (weld) with underlying porous bone after energy removal. This is a reusable device.