Impaired trunk sensorimotor control during isometric force reproduction involving rotation and extension in adolescents with idiopathic scoliosis

Background Adolescent idiopathic scoliosis (AIS) affects 2% to 3% of adolescents and may involve alterations in sensorimotor integration. Although proprioceptive feedback from trunk muscles is essential for spinal alignment, trunk sensorimotor control remains poorly characterized in AIS. This study assessed trunk sensorimotor control in adolescents with AIS using an isometric force reproduction task and determined whether impairments emerge specifically during trunk rotation conditions requiring asymmetric loading.Methods In this cross-sectional controlled laboratory study, 24 adolescents with AIS and 20 age- and sex-matched controls produced isometric trunk extension forces at 2 amplitudes (15% and 30% MVC) and 5 orientations (0°, ±10°, and ±20° rotation) with real-time visual feedback, then reproduced these forces without feedback following a 5-second delay. Amplitude and directional force reproduction errors (constant and absolute) were computed and expressed as a percentage of maximal voluntary contraction and degrees, respectively.Results In the neutral position, no group differences were observed. During trunk rotation at 15% MVC, AIS participants exhibited significantly larger amplitude constant errors (overshooting) compared with controls, and performance varied across rotation angles. At 30% MVC, amplitude overshooting persisted in the AIS group. Directional accuracy was modulated by rotation angle in both groups, with larger errors at more extreme rotations (±20°). Exploratory correlations suggested a possible association between younger age and larger amplitude errors in AIS participants, a pattern not observed in controls.Conclusions Adolescents with AIS exhibited force reproduction deficits specifically during combined extension and rotation, suggesting altered trunk sensorimotor control under asymmetric loading.