Cortical Bone Longitudinal-Torsional Ultrasonic Vibration-Assisted Milling for Multi-Tooth Cutter under Flexible Fixation Condition

In orthopedic surgery, the patient’s skin directly contacts the operating table, and the bone cannot be completely fixed. Currently, most studies on bone cutting are conducted under rigid fixation conditions, which cannot reflect the cutting conditions of bone surgery. To address this gap, this study proposes a multi-tooth cutter longitudinal-torsional ultrasonic vibration-assisted milling (LTUVAM). Pressure plates and bolts are used for the flexible fixation of bone tissue to simulate clinical surgical conditions. The results indicate that the multi-tooth cutter of LTUVAM can reduce cutting forces, suppress burr formation, and produce smaller chips. Compared with straight-edge cutters, the resultant cutting forces of sinusoidal- and corn-edge cutters decreased by 22.3%–46.8% and 29.5%–52.3%, respectively. The multi-tooth cutters also suppressed cutting force fluctuations, leading to a more stable cutting process. In addition, the mechanisms of cutting force reduction, burr suppression, and chip formation in LTUVAM were discussed. This study reveals the cutting performance of cortical bone under flexible fixation conditions and provides an effective technical approach to reducing cutting force and surface damage in clinical bone cutting.