Turning-Point Impact Compromises the Biomechanical Integrity of Cortical Bone During Oscillating Sawing.

PURPOSE: Oscillating bone sawing is widely used in orthopedic surgery, where preserving the mechanical integrity of the prepared bone surface is essential for implant stability. However, the influence of turning-point impacts on the biomechanical integrity of the prepared bone surface remains unclear. This study aimed to quantify the effects of turning-point impacts on surface integrity and the mechanical properties of cortical bone.

METHODS

Oscillating sawing experiments were performed on bovine cortical bone using conventional and optimized trajectories. Dynamic sawing forces were measured to quantify turning-point impact events. Surface damage was characterized by scanning electron microscopy and digital microscopy. Local and global mechanical properties were evaluated by flat-punch and conventional compression tests, respectively.

RESULTS

The conventional trajectory generated pronounced turning-point impact forces, accompanied by extensive surface cracks and breakout defects. In contrast, the optimized trajectory significantly suppressed turning-point impact forces (p < 0.001) and preserved groove wall surface integrity. Consequently, both the local (p < 0.001) and global (p = 0.001) compressive strengths increased, whereas the elastic modulus remained unchanged. These findings indicate that turning-point impacts primarily reduce failure strength by introducing localized microstructural defects while largely preserving bulk elastic stiffness.

CONCLUSION

Turning-point impacts compromise the biomechanical integrity of cortical bone by reducing the load-bearing capacity of implant-relevant bone surfaces. Suppressing these transient impacts helps preserve implant-relevant bone surface integrity and may improve the stability of the bone-implant interface. These findings provide a biomechanical basis for future real-time impact monitoring and adaptive control in surgical robotics to prevent impact-induced damage.