Factors that influence outcome in bracing large curves in patients with adolescent idiopathic scoliosis

Study Design. A retrospective review of 51 patients with adolescent idiopathic scoliosis (AIS) treated with a Boston brace for curves ranging from 36 degrees to 46 degrees. Objectives. To determine what radiographic or clinical observations may be predictive of outcome. Summary of Background Data. Patients with AIS who are braced for curves > 35 degrees are less likely to respond to conservative treatment then patients of similar maturity with smaller curves. Methods. Skeletally immature patients with AIS with no history of prior treatment were treated with a Boston brace. Cobb angles, vertebral tilt angles, coronal decompensation, apical vertebral translation(s), apical vertebral rotation, lateral trunk shift, rib vertebral angle difference, pelvic tilt, and the lumbar pelvic relationship (LPR) were measured at brace prescription, initial in-brace, brace discontinuation, and follow-up. Results. At the time of brace discontinuation, 31 patients (61%) were judged treatment successes. With follow-up observation, an additional eight patients progressed beyond 5 degrees, and a total of 16 patients (31%) required surgical correction. Only patients with double curves were found to have radiographic values predictive of outcome. The LPR angle, the association between the thoracic curve vertebral tilt angles and the amount of in-brace correction of the Cobb angle, were significant predictors. A patient's reported wear schedule significantly influenced outcome. Conclusions. Patients with a double curve pattern in which the thoracic curve is > 35 degrees and the LPR angle is > 12 degrees are significantly more likely to demonstrate curve progression. In-brace correction for double curves of at least 25% and a patient's ability to wear the orthosis > 18 hours/day significantly increased the likelihood of success.