Heat transfer in bone during drilling

grantor: University of TorontoA numerical simulation was used to perform a parametric analysis of the thermal impact of bone drilling operations. The following parameters were varied: drill rotational speed, feed rate, helix angle, point angle, drill diameter, and the density, specific heat, and thermal conductivity of bone. The maximum temperature and resultant thermal damage increase with drill rotational speed. The temperature rises with feed rate from 0.45 to 1.8 mm/s, and decreases slightly up to the maximum feed rate of 4.5 mm/s. In the range of helix/point angle combinations examined, the minimum temperature rise occurs at 38° helix angle and 130° point angle. The maximum temperature increases with drill diameter. The temperature and thermal damage decrease with increasing thermal property values. An experimental investigation of the thermal conductivity of bovine cortical bone was also conducted. The conductivity was found to be 0.58 ± 0.018 W/mK in the longitudinal direction, 0.53 ± 0.030 W/mK in the circumferential direction, and 0.54 ± 0.020 W/mK in the radial direction. These results indicate that bone can be considered thermally isotropic for modelling purposes.M.A.Sc