Age and in-brace Cobb angle predict brace failure in adolescent idiopathic scoliosis.

Purpose: This study aimed to identify independent risk factors for brace treatment failure, examine the correlation between initial in-brace Cobb angle and curve progression, and assess the relationships among age, curve type, initial in-brace Cobb angle, and treatment success.

Methods: Eighty consecutive patients (76 girls and 4 boys; mean age: 12.0 ± 1.2 years) commenced treatment with an underarm brace and were followed for a minimum of 2 years after brace initiation. Brace treatment failure was defined as a final Cobb angle of ≥ 50°, surgery, or curve progression ≥ 6°. A spinal surgeon evaluated standing long-cassette antero-posterior radiographs the pre-treatment, initial in-brace, and final follow-up time points. Multivariate analysis was conducted to classify patients into the bracing success and failure groups. We employed receiving operator characteristic analysis to determine cut-off values based on age and initial in-brace Cobb angle.

Results: The cohort of 80 patients were followed for a mean of 3.1 ± 1.2 years. Overall success rate was 62%, with 19 patients requiring surgery and 30 experiencing bracing failure. Bracing success cases exhibited significantly lower pre-treatment Cobb angle (29.1° vs. 31.7°; P = 0.038), lower initial in-brace Cobb angle (15.5° vs. 21.0°; P < 0.001), and higher in-brace correction rate (48.6% vs. 32.9%; P < 0.001). Multivariate analysis identified younger age (+ 1 year, odds ratio 0.44; P = 0.006) and higher initial in-brace Cobb angle (+ 10°, odds ratio 5.0; P = 0.009) as independent predictors of treatment failure, with cut-off values of 12 years and 16°, respectively.

Conclusion: For patients aged ≥ 12 years, controlling Cobb angle to < 16° at the initial underarm brace fitting may prevent significant curve progression and reduce the likelihood of surgery.