Abstract: BACKGROUND: Cortical bone drilling, cutting, friction, and heat generation can easily cause local temperature rise. If it exceeds the bone tissue tolerance threshold and continues to act, it can lead to complications such as bone necrosis, delayed healing, or prosthesis loosening. The coupling of commonly used clinical parameters such as rotational speed, feed rate, and irrigation significantly affects the degree of thermal accumulation, and there is an urgent need to establish a quantitative tool that can predict the temperature field and heat affected zone to define the safe operating window.
OBJECTIVE: To establish a temperature prediction model for cortical bone in orthopedic surgery by analyzing the temperature distribution of cortical bone at different depths and radial directions. 
METHODS: A three-dimensional transient heat transfer control equation was established to describe the cortical bone drilling process. The moving/distributed heat source method was introduced to characterize the interface heat input caused by the shear of the anterior cutting surface and the friction of the posterior cutting surface, and the temperature field evolution at different radial and depth positions was calculated. Using the inverse heat transfer method, the distribution ratio of heat flux and heat between the tool chip bone interface was inverted under the constraint of a finite temperature sequence of measurement points. The model prediction was further validated through experimental comparison.
RESULTS AND CONCLUSION: (1) Inverse heat transfer inversion showed that approximately 11.7% of the total heat entered the cortical bone solid under given operating conditions. (2) The established temperature prediction model exhibited good consistency with fresh pig bone drilling experiments in terms of peak temperature, temperature rise starting point, and temperature time curve morphology, confirming the reliability of the model in characterizing spatiotemporal temperature distribution. (3) In terms of spatial distribution, the closer to the pore wall (radius X approaching 2.0 mm), the earlier the temperature rise and the higher the peak value. Along the depth direction (z=0-5 mm), the temperature rise first occurred near the surface and gradually extended to the deeper part. (4) The heat affected zone increased with the increase of rotation speed: Under the conditions of a drill diameter of 4 mm and a feed rate of 60 mm/min, the heat affected zone was about 0.71 mm at 800 r/min and about 0.86 mm at 1 000 r/min. (5) The above results indicate that increasing the rotation speed will increase the bone thermal load and heat affected zone thickness while controlling the drill diameter and feed rate. Therefore, in clinical practice, it is necessary to synergistically optimize the rotational speed and cooling/irrigation strategy to reduce the risk of thermal bone injury. This model can be used for preoperative parameter screening and intraoperative risk assessment, providing quantitative basis for developing a "safety parameter window," improving cutting tools and irrigation plans, and enhancing patient outcome performance.

Key words: ">cortical bone drilling, temperature estimation, thermal injury, orthopedic surgery, temperature prediction model