A sonotrode for an ultrasonic surgical instrument has a shaft and an instrument head at a distal end of the shaft. The instrument head is equipped with a cutting structure for the treatment of bones. The shaft has a helical cut-out. The helical cut-out is provided with a transversely running shoulder. A method produces a sonotrode and a surgical instrument having such a sonotrode. As a result of the shoulder in the helical cut-out, the torsional vibration of the instrument head is amplified such that bone material can be ablated in a particularly effective fashion.