Predictability of Supine Radiographs for Determining In-Brace Correction for Adolescent Idiopathic Scoliosis

Study Design. Retrospective radiographic study. Objective. To assess whether flexibility as revealed by the supine radiograph, predicts in-brace curve correction. Summary of Background Data. Currently there is no consensus regarding a standard method to assess curve flexibility and immediate brace effectiveness in treating adolescent idiopathic scoliosis (AIS). Brace fabrication methods may be variable but ideally it should achieve maximal curve correction. Curve flexibility governs the degree of curve correction in-brace and hence dynamic radiographs are commonly performed prior to brace fitting. Methods. This was a radiographic analysis of AIS patients treated with underarm bracing. Correlation of pre-brace, supine, and immediate in-brace Cobb angles was performed. Relationship with possible contributing factors including age, sex, body height, weight, age at menarche and Risser staging was studied. Major and minor curves were compared independently for correlation but the regression model was constructed based on the major curve only. Results. From 105 patients with mean age of 12.2 +/- 1.2 years at brace fitting, supine Cobb angle measurement has significant correlation with immediate in-brace Cobb angle (r = 0.740). Univariate analyses showed no significant relationship with age, weight, height, date of menarche, Risser stage or pre-brace Cobb angle. Our regression model (in-brace Cobb angle = 0.809 x supine Cobb angle) had good fit of the data. Conclusion. Supine radiograph predictably determines the flexibility of the scoliotic curve to brace treatment. It can be used as a guideline to determine the amount of correction achievable with brace-wear. The effectiveness of the brace is dependent on the inherent flexibility of the curve rather than its size or type.