Associated factors and effects of coronal vertebral wedging angle in thoracic adolescent idiopathic scoliosis

Background: Adolescent idiopathic scoliosis (AIS) causes vertebral wedging, but associated factors and the impact of vertebral wedging are still unknown. We investigated associated factors and effects of vertebral wedging in AIS using computed tomography (CT). Methods: Preoperative patients (n = 245) with Lenke types-1 and 2 were included. Vertebral wedging, lordosis, and rotation of the apical vertebra were measured by preoperative CT. Skeletal maturity and radiographic global alignment parameters were evaluated. Multiple regression analysis was performed on associated factors for vertebral wedging. Side-bending radiographs were evaluated using multiple regression analysis to calculate the percentage of reduction of Cobb angles to determine curve flexibility. Results: The mean vertebral wedging angle was 6.8 +/- 3.1 degrees. Vertebral wedging angle was positively correlated with proximal thoracic (r = 0.40), main thoracic (r = 0.54), and thoracolumbar/lumbar curves (r = 0.38). By multiple regression, the central sacral vertical line (p = 0.039), sagittal vertical axis (p = 0.049), main thoracic curve (p = 0.008), and thoracolumbar/lumbar curve (p = 0.001) were significant factors for vertebral wedging. In traction and side-bending radiographs there were positive correlations between curve rigidity and the vertebral wedging angle (r = 0.60, r = 0.59, respectively). By multiple regression, thoracic kyphosis (p < 0.001), lumbar lordosis (p = 0.013), sacral slope (p = 0.006), vertebral wedging angle (p = 0.003), and vertebral rotation (p = 0.002) were significant factors for curve flexibility. Conclusions: Vertebral wedging angle was found to be highly correlated to coronal Cobb angle, with larger vertebral wedging indicating less flexibility. (c) 2023 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.