Ground reaction force loading asymmetry and spinal alignment in adolescents with idiopathic scoliosis: A retrospective observational study

BackgroundIn adolescent idiopathic scoliosis (AIS), treatment decisions emphasize radiographic deformity and curve progression, whereas left-right walking load imbalance is less often quantified because gait-laboratory assessment is not routinely available.ObjectiveTo identify radiologic features associated with asymmetric walking load-sharing and with asymmetry magnitude among asymmetric participants.MethodsThis single-center retrospective cross-sectional study included 180 adolescents with AIS. Peak vertical ground reaction force from three valid force-plate strikes per limb was normalized to body weight, and an asymmetry index (AI) was calculated. AI ≥ 0.10 was used as a pragmatic exploratory threshold for asymmetric loading. Candidate radiologic variables included Cobb angle, lumbar lordosis, thoracic kyphosis, apical vertebral rotation, apical vertebral translation, coronal balance, sagittal balance, pelvic torsion, and pelvic obliquity. Sensitivity analyses included alternative AI thresholds, ridge regression, and walking-speed-adjusted models.ResultsOverall, 132/180 participants (73.3%) were asymmetric. Pelvic obliquity was positively associated with asymmetric loading classification, and this association was directionally consistent across AI cut-offs of 0.08, 0.10, and 0.12. Among asymmetric participants, continuous AI reflected a multivariable radiologic pattern involving axial rotation, coronal and sagittal balance, apex level, pelvic alignment, and sagittal curvature. Ridge regression showed broadly similar coefficient directions but more conservative cross-validated performance. Walking speed adjustment did not materially alter the main interpretation.ConclusionWalking load-sharing asymmetry was common in AIS. Pelvic obliquity was the most clinically coherent classification correlate, while AI magnitude reflected interdependent spinopelvic alignment patterns rather than Cobb angle alone.