The natural history of curve behavior after brace removal in adolescent idiopathic scoliosis: a literature review

Purpose: Brace treatment is the most common nonoperative treatment to prevent curve progression in adolescent idiopathic scoliosis (AIS). The goal of this review and analysis is to characterize curve behavior after completion of brace treatment and to identify factors that may facilitate the estimation of long-term curve progression. Method: A review of the English language literature was completed using the MEDLINE (PUBMED) database of publications after 1990 until September 2020. Studies were included if they detailed a minimum of 1 year post-brace removal follow-up of AIS patients. Data retrieved from the articles included Cobb angle measurements of the major curves at “in-brace,” weaning, and follow-up visit(s) for all patients described and for subset populations. Results: From 75 articles, 18 relevant studies describing a follow-up period of 1–25 years following brace removal were included in the analyses. The reviewed literature demonstrates that curves continue to progress after brace treatment is completed with three main phases of progression: (i) immediate (upon brace removal) where a mean curve progression of 7° occurs; (ii) short term (within five years of brace removal) where a relatively high progression rate is evident (0.8°/year); and (iii) long term (more than five years after brace removal) where the progression rate slows (0.2°/year). The magnitude and rate of curve progression is mainly dependent on the degree of curve at weaning as curves weaned at < 25° progress substantially less than curves weaned at ≥ 25° at 25 years. Conclusion: Curves continue to progress after brace removal and the rate and magnitude of progression are associated with the curve size at weaning, with larger curves typically exhibiting more rapid and severe progression. This analysis provides physicians and patients the ability to estimate long-term curve size based on the curve size at the time of weaning. Level of evidence: IV.