Skeletal Maturity, Brace Compliance, and In-Brace Correction Rate Are Important Factors Associated with Cobb Angle Progression after Brace Treatment in Patients with Adolescent Idiopathic Scoliosis

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Introduction: This study investigated brace treatment for patients with adolescent idiopathic scoliosis (AIS) to comprehensively evaluate the factors associated with curve progression, including the effects of in-brace correction rate (ICR) and objective brace compliance. Additionally, it aimed to establish a clinically useful optimal ICR threshold for effective curve progression control.

Methods: In this single-center retrospective analysis of prospectively collected data, 116 patients with AIS, with Cobb angles of 20°-40° and at least 1-year follow-up were included. Patients whose Cobb angles progressed by >5° were classified into the progressed group, whereas the others were categorized into the non-progressed group. Bracing time was objectively assessed using a thermometer.

Results: In this study, 19 (16.4%) patients were assigned to the progressed group. Open triradiate cartilage was significantly more frequent in the progressed group (22.2% vs. 2.6%, p= 0.011) whereas no significant differences were observed in demographics or pre-brace Cobb angles. The progressed group demonstrated a lower ICR (26.8% vs. 39.5%, p= 0.002) and shorter bracing time at 6 months (14.0 hours vs. 17.4 hours, p= 0.042). Multivariate logistic regression analysis revealed that Sanders grade (1-4), ICR, and bracing time were independently associated with Cobb angle progression (odds ratios: 7.01, 0.95, and 0.89, respectively; all p< 0.05). Based on receiver operating characteristic curve analysis, the ICR threshold of 38.3% was identified to achieve a clinically significant negative predictive value of 95%.

Conclusions:Under objective bracing time monitoring, skeletal maturity, ICR, and bracing time were crucial factors in preventing curve progression 1 year after brace initiation in patients with Cobb angles of 20°-40°. An ICR of 38.3% is recommended as the target when bracing adjustments are feasible.