Accuracy of thoracic pedicle screw placement in adolescent idiopathic scoliosis patients using the entry point identified by new landmarks: a computed tomography study

Background Although thoracic pedicle (TP) screw has gained increasingly popularity in the surgical treatment of adolescent idiopathic scoliosis (AIS) patients, questions remain about the accurate selection of entry point for TP screw placement in these patient. The main objective of the present study was to evaluate the accuracy of TP screw placement in AIS patients using the entry point identified by new landmarks. Methods Thirty-four thoracic AIS patients treated with posterior TP screw instrumentation were included. All these TP screws were inserted through the entry point identified by new landmarks with free-hand technique. Postoperative CT scans were obtained to evaluate the screw position. The perforations of the pedicle were classified as grade 0 (no perforation), grade 1 (<= 2 mm), grade 2 (2.1-4 mm), grade 3 (4.1-6 mm) and grade 4 (6.1-8.0 mm). Screws in grade 0, displaced either medially or anteriorly in grade 1 and displaced laterally in grades 1 to 2 were considered acceptable. Results Of the 495 TP screws inserted, 34 (6.9%) screws were displaced with 7 screws (1.4%) displaced medially, 20 screws (4.1%) displaced laterally and 7 screws (1.4%) displaced anteriorly (P < 0.05). Among the 34 displaced screws, 11 screws (32.4%) were considered as grade 1, 14 screws (38.2%) as grade 2 and 9 screws (29.4%) as grade 3 (P < 0.05). The overall rate of acceptable screws was 97.8%. No screw-related complication was noted. Conclusion Our new method for selecting the entry point of TP screw in AIS patients is convenient and can achieve high accuracy of screw placement, which is worthy of being widely popularized.