Turning-Point Impact Compromises the Biomechanical Integrity of Cortical Bone during Oscillating Sawing
Purpose Oscillating bone sawing is widely used in orthopedic procedures such as total knee arthroplasty, where preservation of the mechanical integrity of the prepared bone surface is essential for implant stability. However, the reciprocating motion of oscillating saws can generate transient impact events near trajectory turning points, potentially inducing surface damage and reducing local load-bearing capacity. This study aimed to investigate the biomechanical consequences of turning-point impact loading during oscillating bone sawing. Methods Oscillating sawing experiments were performed on bovine cortical bone using a conventional trajectory and an optimized trajectory designed to suppress turning-point impacts. Dynamic sawing forces were measured to quantify impact events. Surface damage on the groove wall surface was characterized using scanning electron microscopy (SEM) and optical imaging. Local and global mechanical responses were evaluated using compression tests. Results The conventional trajectory produced pronounced periodic force spikes and generated extensive surface cracks and breakout regions. These impact-dominated events were associated with reduced local compressive strength of the prepared bone surface. In contrast, the optimized trajectory significantly suppressed peak impact forces, resulting in smoother groove wall surfaces with fewer defects. Consequently, the optimized trajectory increased the local compressive strength (p < 0.001) and improved the global compressive strength of the specimens (p = 0.001), while the elastic modulus remained largely unchanged. Conclusion Turning-point impacts during oscillating bone sawing compromise the biomechanical integrity of cortical bone by promoting surface damage and reducing local load-bearing capacity. Suppressing these transient impacts helps preserve the mechanical integrity of surgically prepared bone surfaces.