The impact of intervertebral morphological structure on the cobb angle in patients with adolescent idiopathic scoliosis

Objective: We aimed to investigate how the heights of the vertebral bodies on the concave and convex sides, as well as the differences between these heights, affect the Cobb angle in patients presenting with adolescent idiopathic scoliosis (AIS). Materials and Methods: Radiographs and computed tomography (CT) images of 23 patients aged 13-18 years diagnosed with AIS were retrospectively analyzed. The heights of the vertebral bodies on the concave and convex sides were measured and compared with the curvatures determined using the Cobb method. The contributions of the vertebral body Cobb angle and the intervertebral disc Cobb angle to the total Cobb angle were also evaluated. Results: The vertebral body Cobb angle contributed an average of 52% to the total Cobb angle, while the intervertebral disc Cobb angle contributed an average of 48%. A stronger correlation was observed between the intervertebral disc Cobb angle and the total angle than between the vertebral body Cobb angle and the total angle. Conclusion: The reduced heights of both the intervertebral disc and the vertebral body on the concave side compared to the convex side indicate that as the difference between these values decreases, these components progressively move away from the apical vertebrae. This causes greater wedging at the apex and reduced wedging in adjacent segments, consequently increasing the total Cobb angle. Although the vertebral body Cobb angle contributes more numerically to the total Cobb angle, the relationship between the intervertebral disc Cobb angle and the total Cobb angle was found to be statistically stronger.