Is the Measurement of Pedicle Axial Axes on Computed Tomography in Adolescent Idiopathic Scoliosis Also a Guide for Safer Screwing?

To evaluate the effect of pedicle angle measurement in preoperative axial computed tomography in patients with adolescent idiopathic scoliosis (AIS) on correct thoracic screw placement in free-hand technique on 3-dimensional printing AIS models. In this study, 14 3-dimensional spine models with a scale of 1:1, including the entire spine of a patient with Lenke type 1 curve, were used. Group 1 included screwing applications with unknown pedicle axial angles, and group 2 included screwing applications with known pedicle axial angles. The number and direction of screws in malposition were recorded. In addition, medial encroachment distances of the screws were classified as 0–4 mm and greater than 4 mm, and lateral encroachment distances were classified as 0–6 mm and greater than 6 mm. Evaluation parameters were compared statistically between the groups. The number of screws in the correct position in group 1 was lower than that in group 2 (P < 0.05). The medial and lateral malposition rate in group 1 was greater than that in group 2 (P < 0.05). The medial encroachment rate of 4 mm and greater and lateral encroachment rate of 6 mm and greater in group 1 was greater than that in group 2 (P < 0.05). The medial encroachment rate of 0-4 mm and lateral encroachment rate of 0-6 mm were similar between groups 1 and 2 (P > 0.05). Measurement of pedicle axial axes of preoperative thoracic vertebrae on computed tomography in patients with AIS offers more reliable screwing in free-hand technique.