Influence of surgical drills wear on thermal process generated in bones.

The influence of the wear rate of drills used in bone surgery on the temperature distribution in the femur models (Sawbones) is presented in the paper. Surgical drills of diameter d = 4.5 mm and diverse edge geometry (90° and 120°) were selected for the study. In order to carry out thermal analysis with the use of finite element, experimental studies of wear process were necessary. These studies, among others, consisted in determination of average values of axial forces and cutting torques as a function of the number of drilled holes. The study showed an impact of the drill geometry on values that describe cutting process. It was found that the greatest values of torques and axial cutting forces occur in drills of point angle of 120°. Next, in order to determine the effect of wear rate on the generation of temperature in the cutting zone, thermal analysis of the drilling process using the finite element method was carried out. It was found that higher temperatures in the bone are observed for drilling with the use of the drill of point angle equal to 120°, as in the experimental study. For the tools of such edge geometry the wear of cutting edge is more intensive and the generated temperature in femur for the wear land VBB = 0.32 mm has reached the critical value associated with the process of thermal necrosis.