Analysis and optimization of cortical bone drilling process based on stochastic optimization

The process of bone drilling is essential in orthopedic surgery and fracture treatment, involving the machining of anisotropic composite materials that exhibit significant hardness and strength. This technique is commonly employed to access underlying tissues, place implants, or remove damaged tissue. However, the challenging nature of this process can lead to high shear forces and elevated temperatures, which pose a risk of thermal necrosis - a condition that damages bone tissue due to excessive heat generated during surgery. When drilling temperatures exceed the critical threshold of 47°C, it can result in the death of bone tissue cells, contributing to micro-cracks, and layering within the bone structure. This study examines the effects of key drilling parameters - rotational speed, feed rate, and tool diameter - and is divided into two main sections: laboratory experiments and statistical modeling using Analysis of Variance (ANOVA). A sensitivity analysis was also performed to assess how optimal parameter values influence output temperature. The results emphasize the significance of temperature control during the drilling process and demonstrate that optimizing these parameters greatly improves bone drilling procedures.To manage temperature effectively, researchers employed the Simultaneous Perturbation Stochastic Approximation (SPSA) optimization algorithm, recognized for its high accuracy and efficiency. Laboratory drilling tests were carried out using the optimal values derived from this optimization process, confirming its effectiveness. Additionally, the findings indicate that temperature fluctuations are influenced by the type of bone, its softness or hardness, and the inherent properties of anisotropic composite materials, which can also contribute to higher temperatures during drilling. Overall, this research underscores the vital importance of parameter optimization in enhancing outcomes in orthopedic applications and reducing the risks associated with thermal necrosis.