European Spine Journal - 2026-08-08 - Journal Article
What is the minimum effective wearing dosage of orthotic intervention in adolescent idiopathic scoliosis?
Liu S, Hassan Beygi B, Kwan KYH, Li S, Luo C, Shang L, Zhou L, Yeng WC, Wong MS
Topics
Key Takeaway
In AIS patients completing orthotic treatment, wearing ≥12 h/day produced significantly better outcomes than <12 h/day, but minimum effective wearing time varied from 9.3 to 21.6 h/day depending on Risser sign and target deterioration risk, and exceeded 24 h/day (clinically infeasible) for Risser 0 patients with baseline Cobb >30° at the 2% surgical deterioration risk threshold.
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Summary
This retrospective study of 281 AIS patients examined whether a minimum effective orthosis-wearing time (MEWT) could be defined to prevent curve progression and surgical deterioration, using objective temperature-sensor compliance data categorized into four daily wear-time bands. Patients wearing 12–18 h/day performed equivalently to those wearing 18–24 h/day, and both outperformed the <12 h/day groups for improvement and deterioration rates. Risk-stratified logistic regression estimated MEWT for surgical deterioration at 5% target risk between 8.1 and 20.6 h/day, but for high-risk patients (Risser 0, Cobb >30°) the model-derived MEWT at ≤2% risk exceeded 24 h/day, rendering a safe threshold clinically unachievable.
Key Limitation
The retrospective design cannot exclude selection bias, as patients who completed orthotic treatment represent a compliant survivor cohort that systematically excludes early surgical conversions and dropouts, likely inflating the apparent efficacy of lower wear-time thresholds.
Original Abstract
PURPOSE
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).
METHODS
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.
RESULTS
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.
CONCLUSIONS
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.