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

Abstract

Objective: 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.

Methods: 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.

Results: 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).

Conclusions: Measurement of pedicle axial axes of preoperative thoracic vertebrae on computed tomography in patients with AIS offers more reliable screwing in free-hand technique.

Keywords: 3D model; Adolescent idiopathic scoliosis; Malposition; Pedicle angle; Thoracic screw.