Spine - 2026-04-15 - Journal Article
Pretapping Is Not Effective in Preventing Pedicle Fractures in Lumbar Spinal Instrumentation: A Biomechanical Cadaveric Study.
Bauer DE, Mari Major L, Wigger O, Rohner R, Farshad M, Widmer J, Betz M
Topics
Key Takeaway
Pretapping reduced insertion torque by 55% (1.30 vs 2.91 Nm, P=0.025) but did not alter maximum bending force to failure (103.9 vs 98.1 Nm, P=0.321) or pedicle fracture patterns, while pedicle fill was the only significant predictor of fixation strength (β=222.29 Nm, P=0.035).
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Summary
This study asked whether pretapping reduces pedicle fracture risk during pedicle screw instrumentation by testing 20 lumbar vertebrae from 4 cadavers under alternating pretapped and non-pretapped conditions with biomechanical flexion-to-failure testing. Maximum bending force to failure was equivalent between groups (103.9 vs 98.1 Nm, P=0.321) and fracture patterns did not differ (P=0.384), despite pretapping significantly lowering insertion torque. Pedicle fill was the sole significant predictor of construct strength (β=222.29 Nm, P=0.035), with BMD and pedicle diameter failing to reach significance.
Key Limitation
The sample of only 4 cadavers (20 vertebrae) is grossly underpowered to detect clinically meaningful differences in the rare outcome of pedicle fracture, making all negative findings inconclusive.
Original Abstract
STUDY DESIGN
Biomechanical cadaveric study.
OBJECTIVE
To evaluate whether pretapping reduces the risk of pedicle fractures following pedicle screw instrumentation.
SUMMARY OF BACKGROUND DATA
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. Pretapping, 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 pretapping and non-pretapping 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 pretapping (103.9±47.5 Nm) and non-pretapping (98.1±43.4 Nm) groups ( P =0.321). Pretapping significantly reduced maximum insertion torque (1.30±1.05 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.