An analysis of bone drilling process using finite element analysis

Abstract

The bone drilling process has been used in orthopedic surgical procedures to remove bones and create artificial joint holes. Heat generation due to the cutting temperature is a critical problem, which leads to permanent damage to bone tissues and thermal necrosis. Previous studies noted that the temperature changes during the drilling process depend on the cutting forces. Temperatures above 50 degrees C can damage the surface of the drilled hole. Machining parameters such as the feed rate affect the generation of the cutting force and temperature. Low ranges of surface velocity and feed rate significantly increase the surgery time, thereby increasing the thermal exposure time. Therefore, selecting the appropriate cutting parameters considering the machining time is essential to improve the bone surgery process. A bone cell has anisotropic material properties owing to is orientation. Bones consist of osteons and lamellae, which is analogous to the fiber and matrix in composites such as carbon fiber-reinforced polymer. The finite element (FE) method can be used to analyze the mechanism of the composites machining process, and this requires the use of a failure model. Hill's potential theory is used in the failure analysis of anisotropic materials. Although Hou's failure model yields better analysis results than Hill's theory, the former is suitable for predicting the failure of brittle materials. Bones are more ductile than composites owing to the presence of minerals and moisture. This paper proposes an FE analysis model for three-dimensional orthopedic surgical drilling to predict the cutting force. The performance of the FE model was validated by comparing the obtained results with the cutting force measured during experiments using bovine orthopedic bone. Orthopedic bone has an anisotropic structure. The structure consists of packed osteons and lamellae, reflecting a directional property similar to that of the composites structure. Therefore, the FE model considered the anisotropic material behavior with a failure criterion. The Hashin and Puck models were implemented in the FE model to analyze the failure of the osteons and lamellae, respectively. The thrust force is higher than the radial and tangential forces, which contributes to temperature increase during the drilling process. Therefore, the thrust forces obtained from the experiment and FE model at various drilling parameters were compared to validate the performance of the FE model. At a higher feed rate, the FE model yielded good prediction accuracy with a low error of approximately 3.37 %. Based on the predicted thrust force, the heat generated on the surface of the drilled hole was calculated to predict the degree of necrotic surface.