The Effects of Adolescent Idiopathic Scoliosis on Axial Rotation of the Spine: A Study of Twisting Using Surface Topography

Axial twisting of the spine has been previously shown to be affected by scoliosis with decreased motion and asymmetric twisting. Existing methods for evaluating twisting may be cumbersome, unreliable, or require radiation exposure. In this study, we present an automated surface topographic measurement tool to evaluate global axial rotation of the spine, along with two measurements: twisting range of motion (T(ROM)) and twisting asymmetry index (T(ASI)). The aim of this study is to evaluate the impact of scoliosis on axial range of motion. Adolescent idiopathic scoliosis (AIS) patients and asymptomatic controls were scanned in a topographic scanner while twisting maximally to the left and right. T(ROM) was significantly lower for AIS patients compared to control patients (69.1° vs. 78.5°, p = 0.020). T(ASI) was significantly higher for AIS patients compared to control patients (29.6 vs. 19.8, p = 0.023). After stratifying by scoliosis severity, both T(ROM) and T(ASI) were significantly different only between control and severe scoliosis patients (Cobb angle > 40°). AIS patients were then divided by their major curve region (thoracic, thoracolumbar, or lumbar). ANOVA and post hoc tests showed that only T(ROM) is significantly different between thoracic AIS patients and control patients. Thus, we demonstrate that surface topographic scanning can be used to evaluate twisting in AIS patients.