Sra Developments Limited

Radley Scientific Limited

Michael James Ede

Stephen Michael Radley Young

James Anton Slipszenko

Michael John Radley Young

A torsional-mode ultrasonic vibration generator is manufactured with longitudinal slots extending along its horn which damp unwanted vibrational modes and allow it to be made significantly smaller than previous apparatus. The torsional-mode ultrasonic generator is operable with a suite of surgical tools, to perform portions of an orthopaedic arthroplasty revision procedure. Three of the tools are for removing bone cement from within a bone cavity on a prosthesis cemented into the bone cavity. Three other tools are for separating an uncemented prosthesis from ingrown bone by cutting the bone between the prosthesis and walls of the bone cavity. The seventh tool is provided with sensors to determine a separation between a bone-cutting tool head and a metal prosthesis, feedback from the sensors being used to control servo motors of an articulated mounting for the seventh tool, to maintain the separation at a desirable value.

Torsional orthopaedic revision system

A transducer stack () includes rings () of piezo-electric ceramic alternating with metal electrodes () along a threaded central shaft () extending from a titanium back plate (). A spacer or threaded element () threaded on to the shaft () holds the ceramic rings () and electrodes () in compression against the back plate (). The transducer stack () is mountable eccentrically to a horn () of an ultrasonically-vibratable tool, away from an axis of an elongate waveguide () extending from the horn (). The transducer stack () may vibrate in a flexural mode perpendicular to the waveguide (), generating torsional mode ultrasonic vibrations in the horn () and waveguide (), or in a flexural mode parallel to the waveguide (), generating longitudinal mode ultrasonic vibrations in the horn () and waveguide (). The transducer stack () may be tuned by adjusting the length, mass and/or position along the shaft () of the threaded element (), the back plate () and/or a second threaded element () mounted to the back plate (). Motion sensors () may be mounted to the horn (). Torsional vibrational modes of the horn () and waveguide () may be identified by motion amplitude of a peripheral sensor () exceeding that of a near-axial sensor (). The operation of the transducer stack () may be controlled in response thereto.

Ultrasonic transducer system

Apparatus () for generating torsional-mode ultrasonic vibrations comprises a stack of axially-polarized piezo-electric ceramic rings () having a torsional converter () mounted coaxially to either one face of the stack or to two opposite faces thereof. Each torsional converter () has a cross-sectional inhomogeneity comprising a plurality of helically-extending grooves () extending substantially from end to end of the converter. The grooves () each have a length, measured axially along the converter (), of approximately half the wavelength of ultrasonic vibrations therein. When the stack is energized, the stack and the converter () or converters () resonate together in a purely torsional-mode vibration. The apparatus () is compact and axisymmetric, and is straightforward to incorporate into a simple tool handpiece. The ultrasonic vibrations may be transmitted along a conventional elongate waveguide () of a tool to a distal operative tip (). A very high amplitude torsional oscillation may thus be induced at the operative tip () of the tool. Alternatively, a further converter element () may be located at a distal end of the waveguide () in order partially to convert torsional-mode to longitudinal-mode vibrations for tool operative tips requiring combined-mode oscillations.

Torsional mode ultrasonic generator

An ultrasonic surgical tool has an elongate waveguide operatively connected or connectable to a source of ultrasonic vibrations. An operative element at a distal end of the waveguide has a diameter less than that of the waveguide. A connecting portion of intermediate diameter may connect the operative element and the waveguide. A proximal end of the operative element forms a first step junction, located at a nodal plane of ultrasonic vibrations in the waveguide and operative element, producing a velocity amplitude gain across the step junction. A second zero-gain step junction between the connecting portion and the waveguide is located at an anti-nodal plane. The operative element may include a curved distal cutting and welding element having a pair of elongate welding grooves defining a cutting edge. Alternatively, the operative element may include a welding element having a flat or slightly ridged operative face.

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South Devon, United Kingdom

Michael James Ede