Head kinematic analysis in idiopathic scoliosis: a case-control study

Idiopathic scoliosis (IS) is a three-dimensional spinal deformity associated with impaired sensorimotor integration and diminished postural control; however, the role of head postural stability control remains unclear. This study aims to investigate head postural stability control strategies in IS patients during static and dynamic tasks and their associations with spinal radiographic parameters.

A total of thirty patients with IS and thirty healthy individuals participated in three standing tasks (firm surface, foam surface, and single-leg stance), a 10-m walking test, and stair ascent and descent activities. Head accelerations were recorded using a wearable triaxial accelerometer, and eleven parameters of postural stability were subsequently calculated. Differences between the two groups and correlations with spinal radiographs were analyzed.

Patients with IS demonstrated greater head sway during static balance tasks. On firm-surface standing, root mean square (RMS), range of acceleration displacement (RANGE), mean anteroposterior displacement (APD), sway jerkiness (JERK), and sway path length (SPL) were significantly higher than in healthy controls, and the between-group differences were further amplified under eyes-closed conditions (p < 0.05). During foam-surface standing, peak acceleration (PA), RANGE, and APD were markedly elevated (p < 0.05). In single-leg stance, RMS, PA, and RANGE in the anteroposterior direction were consistently higher in patients (p < 0.05). In contrast, dynamic tasks showed a more conservative control strategy: head acceleration fluctuations in the anteroposterior direction were reduced during walking and stair ascent, while no group differences were observed during stair descent. Correlation analyses indicated that APD was positively associated with the C2-C7 sagittal vertical axis (C2-C7SVA) (p < 0.05), whereas anteroposterior acceleration measures showed significant negative correlations with pelvic incidence(PI) and thoracic kyphosis(TK) (p < 0.05).

Patients with IS employ two distinct strategies for head posture control: exaggerated swaying during static balance and restricted movement during dynamic activities. These patterns may reflect compensatory mechanisms designed to address sensorimotor deficits. Future individualized rehabilitation programs for IS should comprehensively consider the impact of head motor control on overall balance function.