Accuracy of thoracic pedicle screw using ideal pedicle entry point in severe scoliosis

Background The ideal pedicle entry point for the thoracic spine is described as the base of the superior facet at the junction of the lateral and middle thirds of the pedicle. Investigators have reported its accuracy in curves less than 90°. Questions/purposes Our aim was to measure the accuracy of this entry point for pedicle screw insertion in severe and rigid scoliotic curves. Patients and Methods We retrospectively measured the accuracy of thoracic pedicle screws in 26 patients with severe and rigid scoliosis (Cobb angle ≥ 90° ) inserted using the free-hand technique and the ideal pedicle entry point. Placements of thoracic pedicle screws were reviewed on postoperative CT scans, and the incidence and severity of penetration were determined. Screws penetrating medially up to 2 mm and laterally up to 4 mm were considered within the safe zone. Results One hundred sixty-eight (34.8%) of 482 inserted screws breached pedicle walls; 64 (13.2%) and 104 (21.6%) screws breached pedicle walls medially and laterally, respectively. Four hundred thirty-seven screws were within the safe zone, representing an accuracy rate of 90.7%. The accuracy rates of inserted screws in upper, middle, and lower thoracic pedicles were 93.4%, 87.7%, and 92%, respectively. Conclusions Use of the ideal pedicle entry point is safe and accurate for thoracic pedicle screw placement in rigid curves of 90° or greater. Level of Evidence Level II, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.