Comparison of heat dissemination from longitudinal and torsional mode ultrasonic shears using infrared thermal imaging and thermocouples

S.S Ching, Prof M.J. McMahon, Academic Unit of Surgery, The General Infirmary at Leeds, Yorkshire, UK

This study compared both waveguide blade and tissue temperatures generated by LOTUS and Harmonic Scalpel shears in vitro.

Using a digital infrared camera, thermographic still images and video were recorded as both devices cut into bovine muscle tissue. In addition, 0.8mm thermocouple needles were positioned at defined distances from the blade to measure thermal spread during and after cutting.

At a mean distance of 3.70mm (p=0.843) from the Harmonic Scalpel blade the temperature of the tissue rose by 8.27ºC (p=0.150). At a mean distance of 3.75mm (p=0.843) from the LOTUS blade the temperature rose by 10.17ºC (p=0.150). The median surface temperature at the edge cut by the Harmonic Scalpel was 78ºC and by LOTUS was 69ºC. This difference was attributed to the generation of surface friction by the longitudinal device.