Abstract: An ultrasonically-vibratable surgical tool for cement removal in revision arthroplasty, comprises an elongate solid shaft. This can be mounted at its proximal end to a source of ultrasonic vibrations, so that the shaft acts as a waveguide for propagation of the ultrasonic vibrations. The shaft has at its distal end an operative head to act on the cement. An intermediate portion of the elongate shaft is provided with at least one row of dimples extending helically along and around that portion of the elongate shaft. Each dimple is separate from each adjacent dimple. The dimples may have a shallow part-spherical profile.

Abstract: Apparatus for generating torsional-mode ultrasonic vibrations, for example in a surgical tool, comprises an ultrasonic transducer that would conventionally produce longitudinal-mode ultrasonic vibrations, with a long, hollow, cylindrical, mode converter mounted coaxially to its distal end. A plurality of holes are formed through the walls of the mode converters. These holes are arranged in multiple parallel helical rows, extending along and around the cylindrical mode converters. Holes within the same row are spaced relatively closely, compared with the spacing between rows. Relationships have been established between the hole diameter (d), the spacing between rows (W), the spacing between holes in the same row (l), the spacing between individual holes in adjacent rows (L), and the overall diameter of the mode converter (D). In a preferred version, the holes through the walls of the second mode converter are tapered inwardly, rather than being cylindrical holes as in the first mode converter.

Abstract: A series of surgical tools (11, 21, 31, 41, 51, 61, 71, 81) have respective operative heads (16, 26, 36, 46, 56, 66, 76, 86 & 96) mounted adjacent a distal end of an elongate waveguide (12, 13, 14). The operative heads (16, 26, 36, 46, 56, 66, 76, 86 & 96) are used to remove PMMA bone cement (2, 5) from within a hollow bone (1), such as a femur (1), as part of a prosthesis revision operation, such as replacement of an artificial hip joint. Torsional-mode ultrasonic vibrations are transmitted along the waveguide (12, 13, 14) to the respective operative heads (16, 26, 36, 46, 56, 66, 76, 86 & 96), which are applied to the bone cement (2, 5), softening it and facilitating its removal. Elongate radial channels (18, 23, 28, 38) extend across cement-contacting faces of several of the surgical tools (11, 21, 31, 41, 71, 81), acting to focus and transmit the torsional-mode ultrasonic vibrations into adjacent cement (2, 5).