Interrelationships among 3D spinal alignment variables during active self-correction in adolescents with idiopathic scoliosis.

PURPOSE: This study aimed to (1) determine whether active three-dimensional (3D) self-correction induces immediate changes in spinal alignment compared with passive standing, (2) examine associations between anthropometric variables and spinal alignment parameters, and (3) identify coupled predictive relationships among alignment parameters during self-correction in adolescents with idiopathic scoliosis (AIS). METHODS: Fifty-four adolescents with AIS (mean age 16.96 ± 2.61 years) were assessed using the DIERS Formetric 4D surface topography system under two conditions: passive standing and active self-correction following a standardized 30-minute training session. Measured variables included trunk inclination, lateral deviation, surface rotation, thoracic kyphosis, and lumbar lordosis. Between-condition differences were analyzed using the Wilcoxon signed-rank test. Associations with anthropometric variables were examined using Spearman's correlation. Multiple linear regression models were applied to identify predictors of correction magnitude based on baseline alignment parameters. RESULTS: Significant improvements were observed during active self-correction in trunk inclination, lateral deviation, surface rotation, thoracic kyphosis, and trunk length (p 0.05), except for a weak correlation between trunk inclination and body weight (r = -0.233). Regression analyses demonstrated that correction magnitude was strongly associated with baseline alignment parameters, with substantial explanatory power (R² up to 0.720). Significant cross-planar relationships indicated interdependence among coronal, sagittal, and transverse parameters. CONCLUSION: Active 3D self-correction produces immediate, measurable improvements in spinal alignment in AIS. Correction responses are primarily determined by baseline biomechanical alignment rather than anthropometric factors and exhibit coupled, multi-planar interactions, supporting integrated PSSE approaches targeting coordinated control across all planes.