Mechanistic Model to Predict Forces in Bone End Milling: An Experimental Study Intended for Bone Grafting Surgery

In orthopedic surgery, subtractive manufacturing processes, such as drilling, sawing, grinding, and milling, are employed for implant placement, fracture fixation, and reconstruction surgery. If the forces resulting from the bone cutting processes are uncontrolled, mechanical damage (e.g., microcracks and bone fragmentations) is observed in the local host bone. In this study, the use of the end milling process for harvesting bone grafts was investigated. Importantly, the mechanistic model for the prediction of bone end milling forces was developed, considering the axial, tangential, and radial force components, geometry of the end milling cutter, and mechanical properties of the bone. First, an analytical description of the milling forces resulting from the end milling process was developed. Second, the cutting and edge force coefficients were calculated. Third, the axial, tangential, and radial forces resulting from the end mill cutter were predicted from the mechanistic model. To validate the end milling forces predicted from the mechanistic model, different sets of experiments were conducted. It was verified that the forces predicted from the mechanistic model agreed well with the validation experiments. The outcomes of this study can be used to pre-estimate the forces resulting from the end milling cutter, and therefore, mechanical damage can be avoided.