Task-specific compensatory joint control strategies in adolescent idiopathic scoliosis during dynamic balance tasks

Adolescent idiopathic scoliosis (AIS) involves subtle postural control deficits, but the underlying joint-level strategies remain unclear. Conventional center-of-pressure (COP) metrics quantify balance but do not reveal how specific joints contribute to compensation. To investigate multi-segmental compensatory strategies in AIS by examining joint kinematics and their associations with COP metrics during dynamic balance tasks. Thirty-five AIS participants and twenty-nine matched controls performed anterior-posterior (A-P) and medio-lateral (M-L) balance tasks on an unstable platform. Three-dimensional joint kinematics were captured using wearable inertial sensors (STT system), synchronized with COP recordings. Joint features included range of motion (ROM), bilateral asymmetry (diff), and mean orientation. Group comparisons and correlation analyses were conducted with FDR correction for multiple testing. AIS participants showed a markedly broader distribution of significant joint-COP correlations than controls, particularly in M-L tasks (52 vs. 7 associations). These correlations spanned cervical, upper limb, pelvic, and lower limb segments, indicating a diffuse compensatory control strategy. In contrast, controls showed localized associations, mainly at the hip and knee. However, most direct group differences at the joint level did not remain significant after FDR correction. This study provides a comprehensive evaluation of multi-segmental joint-COP associations across both A-P and M-L balance tasks using wearable inertial sensors. Compared with previous work focusing on isolated kinematics or global COP outcomes, our approach integrates joint-level motion and stabilometric data to characterize distributed compensatory strategies in AIS. Individuals with AIS exhibited widespread compensatory recruitment-especially under M-L demands-indicating adaptive yet inefficient balance control that may increase long-term postural risk. These findings highlight the need for rehabilitation strategies targeting trunk-hip coordination to reduce compensatory overload in distal joints.