Methods: Biomechanical cadaveric study. Objective: To evaluate whether pre-tapping reduces the risk of pedicle fractures following pedicle screw instrumentation.

Background: Pedicle screw instrumentation is the standard for rigid fixation of the thoracolumbar spine. While complications such as screw loosening and misplacement are well-documented, pedicle fractures are rare and poorly understood. Pre-tapping, a technique used during screw insertion, has been proposed to enhance fixation strength and potentially reduce the risk of fractures. However, its biomechanical effects on pedicle integrity remain unclear.

Methods: Twenty lumbar vertebrae (L1-L5) were harvested from four cadavers. Preoperative CT scans were used to plan screw trajectories and assess bone mineral density (BMD). Each vertebra was alternately instrumented with screws using pre-tapping and non-pre-tapping techniques. Biomechanical testing measured maximum bending force to failure under a flexion moment. Pedicle fractures were classified based on CT imaging, and statistical analysis was performed to evaluate factors influencing fracture risk.

Results: The maximum bending force to failure showed no significant difference between pre-tapping (103.9±47.5 Nm) and non-pre-tapping (98.1±43.4 Nm) groups (P=0.321). Pre-tapping significantly reduced maximum insertion torque (1.30±1.05 Nm vs. 2.91±2.65 Nm, P=0.025). Pedicle fill was a significant predictor of bending force (β=222.29 Nm, P=0.035), while BMD and pedicle diameter were not. Fracture patterns did not differ significantly between groups (P=0.384).

Conclusions: Pre-tapping does not significantly influence the biomechanical stability of pedicle screws or the risk of pedicle fractures under flexion moments. However, pedicle fill is a critical factor in screw fixation strength. These findings suggest that optimizing pedicle fill is more relevant than pre-tapping in enhancing construct stability.