Sensory integration and spinal structure in AIS: is there a functional–structural association?

Adolescent idiopathic scoliosis (AIS) is characterized by three-dimensional spinal deformities and often co-occurs with balance impairments. However, it remains unclear whether postural deficits in AIS are statistically associated with spinal morphology, or instead reflect independent alterations in sensorimotor integration. This study aimed to examine whether postural control performance under sensory challenge is statistically associated with three-dimensional spinal morphology in adolescents with AIS. A total of 64 young adults (35 with AIS, Cobb angle 10°–39°; and 29 healthy controls) were assessed using a cross-sectional design. Postural control was evaluated via the modified Clinical Test of Sensory Interaction and Balance (mCTSIB), which included four standard sensory conditions and an additional vestibular-challenging task involving rhythmic head movements. Spinal morphology was measured using the DIERS 4D Formetric system. Between-group differences were analyzed using Mann–Whitney U tests. Within-group correlations were tested via Spearman’s coefficients, and intergroup differences in correlation strength were evaluated using Fisher Z-transformation with false discovery rate (FDR) correction. AIS participants exhibited significantly greater postural instability in two sway parameters—mediolateral (ML) average velocity and path length—but only under the most challenging vestibular condition (FoEC-HDM; p < 0.01). Five spinal parameters also differed significantly between groups (p < 0.05). However, no significant correlations were observed between postural control and spinal morphology within either group. No intergroup differences in correlation strength were identified after FDR correction. In yong adults with mild to moderate AIS (Cobb angle 10°–39°), postural instability and structural spinal deformities appear to be coexisting but statistically independent. No significant associations were found between spinal morphology and postural control under sensory challenge. These findings suggest that balance impairments may reflect central sensorimotor alterations rather than curve severity.Future studies should examine whether such independence persists across broader severity ranges or curve types in AIS.