Cutting Behavior of Cortical Bone in Different Bone Osteon Cutting Angles and Depths of Cut

Cortical bone is semi-brittle and anisotropic, that brings a challenge to suppress vibration and avoid undesired fracture in precise cutting process in surgeries. In this paper, a novel analytical model is proposed to represent cortical bone cutting processes. The model is utilized to predict the chip formations, material removal behavior and cracks propagation under varying bone osteon cutting angles and depths. Series of orthogonal cutting experiments were conducted on cortical bone to investigate the impact of bone osteon cutting angle and depth of cut on cutting force, crack initialization and propagation. The observed chip morphology highly agreed with the prediction of chip formation based on the analytical model. The curly, serrated, grainy and powdery chips formed when the cutting angle was set as 0 degrees, 60 degrees, 90 degrees, and 120 degrees, respectively. Cortical bone were removed dominantly by shearing at a small depth of cut from 10 to 50 mu m, and by a mixture of pealing, shearing, fracture and crushing at a large depth of cut over 100 mu m at different bone osteon angles. Moreover, its fracture toughness was calculated based on measured cutting force. It is found that the fluctuation of cutting force is suppressed and the bone material becomes easy to remove, which attributes to lower fracture toughness at bone osteon cutting angle 0 degrees. When the cutting direction develops a certain angle to bone osteon, the fracture toughness increases then the crack propagation is inhibited to some extent and the fluctuation of cutting force comparatively decreases. There is a theoretical and practical significance for tools design and operational parameters choice in surgeries.

Automated summary

A novel analytical model is proposed to study cortical bone cutting processes, and a series of experiments are conducted to investigate the impact of cutting angles and depths on cutting force and crack propagation. The experimental results highly agree with the model prediction, and the cutting depth and angle have significant effects on chip morphology and material removal behavior.