Anatomy and biomechanics of thoracic pedicle screw instrumentation

Purpose of review: Thoracic pedicle screws are commonly used for fixation, with previous studies reporting various insertion techniques, anatomic concerns, and clinical results. However, the optimal biomechanic insertion techniques have only recently been elucidated. The purpose of this review is to summarize the recent literature in terms of the anatomy and biomechanics of thoracic pedicle screw instrumentation. Recent findings: A straightforward trajectory for pedicle screw instrumentation has been found to be biomechanically superior to the anatomic trajectory in terms of insertion torque and pullout strength. Further, undertapping the pedicle path seems to have a significant effect on pullout strength regardless of sagittal trajectory. When compared with hooks, thoracic screws are superior in terms of axial and tangential fixation strength, but this is not significant in severely osteoporotic vertebrae (bone mineral density < 100 mg/mL). Summary: The understanding of optimal thoracic pedicle screw biomechanics continues to evolve. Further work on the biomechanics of thoracic pedicle screw constructs is still needed.