Pronation Adaptation During Gait in Adolescents with Thoracic Idiopathic Scoliosis

Adolescent idiopathic scoliosis (AIS) is associated with altered trunk posture and asymmetric lower limb biomechanics. Although gait asymmetries have been observed in AIS, phase-specific compensatory adaptations in dynamic foot posture remain underexplored. The pronation-supination index (PSI) offers a detailed view of foot posture during specific stance phases. This study aimed to analyse PSI values across five gait phases in adolescents with thoracic AIS, focusing on convex-concave foot asymmetry.Methods. Thirty adolescents diagnosed with thoracic/thoracic dominant AIS (Lenke types 1–4) were included (mean age 14.90±2.92 years; 23 female). The mean major Cobb angle was 35.27±8.64. PSI data were collected using the dynamic pedobarographic system while participants walked barefoot at a self-selected pace. PSI was calculated separately for the convex and concave feet during five stance phases: foot contact, early-midsupport, midsupport, late-midsupport, and toe-off. Side to side comparisons were conducted using paired t-tests.Results. PSI was significantly higher on the convex side during the foot contact phase (54.01±3.91 vs. 52.13±4.70, p = 0.044), indicating increased pronation. No significant differences were found in PSI during early-midsupport, midsupport, late-midsupport, or toe-off phases (p > 0.05). Conclusion. Foot pronation increases specifically during initial contact on the convex side in adolescents with thoracic AIS. This reflect a selective pronation strategy at initial contact to maintain balance and compensate for coronal trunk asymmetry. These findings may have clinical relevance for developing targeted interventions that address dynamic gait stability in AIS patients.Keywords:Adolescent idiopathic scoliosis; gait adaptation; pronation-supination index.