Mechanical effects of erbium:YAG laser bone ablation

When intending to use pulsed erbium:YAG laser radiation for the ablation of small bones, e.g., the ossicular chain or footplate, not only temperature and thermal damage, but also mechanical side effects become important. In studies on desiccated bone the total recoil momentum caused by laser ablation was measured using a sensitive pendulum. The momentum depends linearly on the radiant energy of the laser pulse with a slope of 10(-4) kg m s-1/J. The temporal course of the recoil force during ablation observed by means of a piezoelectric transducer is nearly proportional to the laser pulse intensity. By evaluating recoil momentum and mass loss data, the average initial velocity of the plume was calculated to be 230 to 280 m s-1. The kinetic energy is approximately 1% of the input energy. The measurements support to the hypothesis of a thermally induced explosive process.