Plantar Pressure-Paraspinal Surface Electromyography Associations and Within-Participant Surface Electromyography Changes Under Orthotic Insoles in Idiopathic Scoliosis: A Pilot Study.

Abstract

To examine associations between plantar pressure and paraspinal surface electromyography amplitude in idiopathic scoliosis and to describe within-participant changes in paraspinal surface electromyography symmetry under ordinary (nonorthotic) versus orthotic insole conditions. A cross-sectional observational correlation study and a single-arm, within-participant repeated-measures comparison. Hospital. Twenty-four patients (N=24) with idiopathic scoliosis and without organic lower-limb or ankle disease. After baseline testing, participants wore customized biomechanical orthotic insoles in their usual footwear during daily activities for 1 week (familiarization period). Regional plantar load distribution across predefined foot regions, expressed as a percentage of body weight, and paraspinal surface electromyography amplitude (root mean square) were measured; the symmetry index was calculated from bilateral root mean square values. The root mean square of the convex-side apical vertebra showed a moderate negative correlation with concave-side forefoot load (Spearman ρ=-0.55; P=.006) and a moderate positive correlation with convex-side rearfoot load (ρ=0.55; P=.005). During walking, symmetry index was significantly lower under the orthotic insole condition than under the ordinary condition (orthotic vs ordinary: 35.57% vs 46.35%; P=.004). No significant difference in standing symmetry index was observed between conditions (P=.408). Plantar pressure distribution was associated with paraspinal muscle activation in idiopathic scoliosis, consistent with a potential foot-spine neuromuscular coupling relationship. Orthotic insoles were associated with greater paraspinal activation symmetry during walking; these findings may provide preliminary guidance for further exploration of integrated foot-spine rehabilitation strategies.