Predicting final results of brace treatment of adolescents with idiopathic scoliosis: first out-of-brace radiograph is better than in-brace radiograph-SOSORT 2020 award winner

Purpose In-brace radiograph of adolescents with idiopathic scoliosis (AIS) has been shown to reflect brace efficacy and the possibility of achieving curve correction. Conversely, the first out-of-brace radiograph could demonstrate the patient's ability to maintain the correction. We aimed to determine which of the two radiographs is the best predictor of the Cobb angle at the end of treatment (final radiograph). Design Retrospective cohort study of a prospective dataset. Methods The population was selected based on the following inclusion criteria: AIS, age 10-18 years; Risser score 0-2; Cobb angle 25-40 degrees; brace treatment; availability of all radiographs. Statistics: Pearson correlations provide a first exploration of data. The univariate and multivariate logistic regression model tested the predictors. Finally ROC curve provided a check of model accuracy. Results A total of 131 patients were included (mean age 13.0 +/- 1.3, Cobb angle 33.2 +/- 5.5 degrees; 78% females). At the end of treatment, 56% had stabilised, 9% had progressed, and 44% had improved. The difference between the in-brace and final radiographs was 8.0 +/- 6.0 degrees, while the difference between the first out-of-brace and final radiographs was 1.8 +/- 5.2 degrees. The best predictor of final outcome was the first out-of-brace radiograph (0.80), compared to in-brace (0.68) and baseline (0.59) radiographs. The best cut-offs to predict avoidance of progression were 30% and 10% of the correction rates for the in-brace and first out-of-brace radiographs, respectively. Conclusion The first out-of-brace radiograph predicts end results better than the in-brace radiograph. It offers an excellent clinical reference for clinicians and patients. The first out-of-brace radiograph should be considered an essential element of future predictive models.