Computed Tomography-Guided Navigation of Thoracic Pedicle Screws for Adolescent Idiopathic Scoliosis Results in More Accurate Placement and Less Screw Removal

Study Design. Retrospective study of computed tomography-guided navigation (CTGN) of thoracic pedicle screw placement in patients with adolescent idiopathic scoliosis (AIS). Objective. To compare the accuracy and safety of thoracic pedicle screw placement and frequency of intraoperative removal using CTGN versus conventional freehand technique in AIS. Summary of Background Data. Even in experienced hands, more than 10% of the thoracic pedicle screws are misplaced. CTGN may improve accuracy and safety, but there is little published data on its efficacy. Methods. We reviewed intraoperative computed tomographic images in a consecutive series of AIS cases undergoing posterior fusion during a 1-year period. Three types of screws were identified: an optimal screw-the central axis is in the plane and axis of the pedicle with the tip completely within the vertebral body; an acceptable screw-the majority of its shank is outside the central axis of the pedicle, but not potentially unsafe; and a potentially unsafe screw-(1) the central axis of the screw traversed the canal, (2) left anterior/lateral vertebral body perforation, risking the aorta, or (3) any screw repositioned or removed after the postimplant computed tomography. Results. In 42 patients, 485 screws were evaluable with a visible pedicle and screw (300 navigated and 185 non-navigated). Screws were classified as follows: optimal screws, 74% CTGN versus 42% non-navigated; acceptable screws, 23% CTGN versus 49% non-navigated; and potentially unsafe, 3% CTGN versus 9% non-navigated (P < 0.001). A potentially unsafe screw was 3.8 times less likely to be inserted with navigation (P = 0.003). The odds of a significant medial breach were 7.6 times higher without navigation (P < 0.001). A screw was 8.3 times more likely to be removed intraoperatively in the non-navigated cohort (P = 0.003). Conclusion. CTGN resulted in more optimally placed thoracic pedicle screws, fewer potentially unsafe screws, and fewer screw removals.