Evaluation of the effect of Rigo-Chêneau type brace on adolescent idiopathic scoliosis using computer-aided modeling and 3D surface analysis.

PURPOSE: Adolescent idiopathic scoliosis (AIS) is a three-dimensional spinal deformity and clinical follow-up mainly relies on the Cobb angle measured from two-dimensional radiographs. Since this measure may not fully reflect brace-induced changes in trunk shape and appearance, this study aimed to evaluate brace effectiveness by comparing Cobb angle changes with trunk surface remodeling assessed using radiation-free 3D surface scanning. METHODS: This retrospective study analyzed superimposed pre- and post-treatment trunk surface scans to generate 3D distance color maps and calculate RMS deviation metrics in 3D (RMS-3D) and 2D (RMS-2D). Signed Cobb angle change (ΔCobb; negative values indicate Cobb angle reduction) was used to retain the direction of radiographic change. Associations between ΔCobb and RMS metrics were examined using Pearson correlation analysis, and simple linear regression tested the predictive value of RMS-3D for ΔCobb. Absolute Cobb angle change (|ΔCobb|) was also evaluated as a secondary analysis. Statistical significance was set at p < 0.05. RESULTS: ΔCobb demonstrated significant positive correlations with RMS-2D (r = 0.711, p = 0.021) and RMS-3D (r = 0.795, p = 0.006), indicating significant associations between signed Cobb angle change and the surface-deviation measures. Simple linear regression showed that RMS-3D significantly predicted ΔCobb (slope = 4.43, p = 0.006), explaining 63.1% of the variance. In the secondary analysis, correlations between |ΔCobb| and RMS metrics did not reach statistical significance (|ΔCobb| vs. RMS-3D: r = - 0.509, p = 0.133; |ΔCobb| vs. RMS-2D: r = - 0.153, p = 0.672). Given the small sample size, these findings should be interpreted cautiously. CONCLUSION: Surface topography objectively quantified and visualized brace-induced trunk remodeling in AIS and may complement radiographic assessment in monitoring brace effectiveness.