Optimization of drill bit design in bone drilling in order to mitigate the thermal necrosis by experimental and statistical approaches

Abstract Purpose Bone temperature rise during drilling and subsequent thermal necrosis are a serious threat to orthopedic surgeries as they can cause irreversible damage to bone cells and failure of fracture treatment. Part of the bone temperature rise is due to chip formation while the other part is related to the heat sources of drill bit-hole wall friction and chip-hole wall friction. The present study has examined reduction of frictional heating by changing the drill bit design with an experimental and statistical approach. Methods Drilling tests were performed on 31 surfaces with drills of different designs under conditions of rotational speed of 1000 r.min − 1 , feed rate of 50 mm.min − 1 , and hole depth of 8 mm on the bovine femur. Results The change in the diameter and length of the different sections of the drill bit had a significant effect on the bone temperature rise; in 21 cases it led to a decrease, while in 6 cases it resulted in an increase in the temperature compared to the result of the standard drill ( T m =24°C). In addition, by means of statistical analysis through Minitab software, a statistical model of bone temperature rise was developed based on the drill geometry and optimal values for the drill geometry were extracted. Conclusion The validation test performed on the optimal drill revealed an acceptable agreement of its result ( T m =8.6°C) with the value predicted by statistical analysis ( T m =8.8°C) as well as the possibility of preventing thermal necrosis by using this new design for the drill.