What is the minimum effective wearing dosage of orthotic intervention in adolescent idiopathic scoliosis?

Abstract

This study aimed to estimate the minimum effective orthosis-wearing time (MEWT) needed to prevent curve progression and reduce surgical risk in adolescent idiopathic scoliosis (AIS). This retrospective study analyzed 281 patients with AIS who completed orthotic treatment. Compliance was measured using both objective temperature sensors and subjective self-reports, categorized into four daily wear-time levels: 0 to 6, 6 to 12, 12 to 18, and 18 to 24 h. Treatment outcomes at endpoint were classified as improvement (> 5° decrease), stabilization (± 5°), deterioration (> 5° increase), or surgical deterioration (Cobb angle > 50° or requiring surgery). Associations between compliance and outcomes were examined, and MEWT thresholds were estimated within risk-stratified subgroups based on baseline clinical risk factors. Patients wearing orthoses for 0 to 6 and 6 to 12 h/day showed significantly lower improvement rates and higher deterioration rates than those in the 12 to 18 and 18 to 24 h/day groups. No significant differences in treatment outcomes were observed between the 12 to 18 and 18 to 24 h/day groups, nor between the 0 to 6 and 6 to 12 h/day groups. Risk-stratified logistic regression models showed that MEWT estimates for curve deterioration ranged from 9.3 to 21.6 h/day, depending on target risk (20% to 5%) and Risser sign. For surgical deterioration, MEWT estimates at the 5% target risk ranged from 8.1 to 20.6 h/day. However, for patients with Risser 0 and a baseline Cobb angle > 30°, the model-derived MEWT estimates for target risks of 2% or lower exceeded 24 h/day and were therefore considered clinically infeasible. Although orthosis wear of 12 h per day or more was associated with better outcomes in group-level comparisons, MEWT is not uniform and varies by baseline clinical risk factors. Integrating objective compliance monitoring with risk-adapted targets may support personalized orthotic prescriptions, facilitate shared decision-making, and optimize treatment effectiveness.