Measurement and analysis of brace-skin interface force in the treatment of scoliosis

Background Scoliosis is a spinal deformity characterized by a 3-dimensional (3D) distortion; however, the biomechanical interaction between bracing forces and the patient's trunk remains incompletely understood. Objectives The purpose of this study is to characterize the corrective forces exerted by scoliosis braces at the brace-skin interface during daily postures, thereby informing clinical decisions on dynamic brace adjustment/replacement to enhance treatment efficacy. Study design This is an experimental measurement study on scoliosis orthosis for the treatment of adolescent idiopathic scoliosis. Methods Thirty-one patients with adolescent idiopathic scoliosis (26 girls and 5 boys) were included. Brace-skin interface forces were quantified using a force collection system under 6 representative daily postures. The data were analyzed for force variations across postures/activities and correlations with scoliosis correction outcomes. Results Compared to standing (natural breathing) when first fitted, brace-skin interface forces differed significantly for all postures ( p < 0.05) except walking ( p > 0.05). However, after 3 months of brace wear, forces during walking and sitting showed no significant difference ( p < 0.05) compared with standing (natural breathing). Patients with right thoracic curves exhibited higher interface forces than those with right thoracolumbar curves. Importantly, no correlation was found between interface forces (after 3 months) and the percentage correction of Cobb angle or vertebral rotation (| r | < 0.41, p > 0.1). In summary, after brace intervention, the patient exhibited reductions in brace-skin interface force, Cobb angle, and vertebral rotation angle, indicating that this brace demonstrates efficacy in providing passive correction of scoliosis. Conclusions A comparative analysis revealed a marked reduction in brace-skin interface force after 3 months of brace adaptation, regardless of body postures or curve types. Notably, respiration postures (maximum inspiration/expiration) induced significant force fluctuations during daily activities. The short-term bracing intervention (3 months) is insufficient to drive measurable spinal structural remodeling, necessitating long-term orthotic engagement coupled with timely brace modifications or replacements.