Ultrasonic cutting tool

An ultrasonic surgical tool comprising:

• an elongate waveguide,
• a source of torsional mode ultrasonic vibrations operatively connected or connectable to a proximal end of said waveguide,
• an operative element having a proximal end adjacent a generally cylindrical distal end of said waveguide and comprising a radially-extending ridge defined between a substantially parallel pair of grooves extending longitudinally of the waveguide and deepening from a distal end of the waveguide to a distal end of the operative element, a first of said substantially parallel pair of grooves being longer than a second of said substantially parallel pair of grooves in a plane parallel to said ridge, said operative element being curved in a plane transverse to a plane of the ridge, said operative element converging in a longitudinal direction from the proximal end to the distal end of the operative element, wherein, when the tool is operated in torsional vibrational mode, the ridge and regions of the grooves flanking the ridge are configured to transmit ultrasonic energy into a tissue, and
• wherein the operative element further comprises first and second vertically extending flats, wherein said first and second flats converge towards the distal end of the operative element and begin each level with the other at their proximal ends, wherein the first flat extends at a lesser angle to the ridge than the second flat, and wherein a tip formed by the first and second flats is asymmetric about said ridge, said tip having more material remaining to a side of the ridge adjacent to the first flat than to a side of the ridge adjacent to the second flat.