An analytical and numerical approach to the determination of thermal necrosis in cortical bone drilling

In the process of repairing fractures in the bone region with orthopedic injuries, the application of supporting and strengthening the bone tissue with screws, wires, rods, and plates is a widely preferred internal fixation method. In this treatment process, it is necessary to drill the bone tissue to fix the screws. Due to the heat generated in the drilling process, mechanical and thermal damage occurs in the bone tissue. In this study, it is focused that the effect of different cutting conditions on the temperature distribution and necrosis zones in the drilling of human cortical bone. In this context, by selecting variable drill geometry (diameter, point angle, and helix angle) and variable cutting parameters (cutting speed and feed rate), temperature distribution and necrosis zones were investigated with finite element analyses and analytical calculations. When the findings were evaluated, it was understood that drill diameter and cutting speed did not have a significant effect on temperatures and necrosis zone at low cutting speeds. At high cutting speeds, it was observed that the feed rate and drill point angle had an indeterminate effect on the temperatures. The lowest temperature values were obtained at cutting speed of 750 rpm and a feed rate of 0.1 mm/rev for low cutting speeds, and cutting speed of 1500 rpm, helix angle of 10° and drill bit diameter of 2 mm for high cutting speeds. The narrowest necrosis zones were obtained at cutting speed of 250 rpm and feed rate of 0.1 mm/rev for both drill diameters. As a result, the effects of different drill geometry and cutting parameters were determined in order to obtain low temperature distribution and narrow necrosis zone in cortical bone drilling.