Wearing a brace for idiopathic scoliosis above 18 hrs/day shows a dose-response effect on the outcomes improvement and end-of-treatment Cobb angle below 30 degrees.

purposeThe Brace Adolescent Idiopathic Scoliosis Trial (BrAIST) reported a bracing dose–response curve in AIS for brace-wearing time (BWT) up to 18 h/day (h/d) on the outcome end-of-treatment < 50°. We aimed to examine the dose–response curve for this and other relevant outcomes in cases of BWT > 18 h/d.

methodsDesign: Retrospective secondary analysis of consecutively collected data. Participants: braced AIS patients with curves < 45° and a subgroup with BrAIST inclusion criteria. Treatment: different braces, prescribed 18 to 24 h/d, according to curve topography, Cobb angle and a shared decision-making approach. We divided patients into BWT quartiles and developed dose–response curves using the BrAIST methodology for the end-of-growth outcomes END < 50°, END < 30°, avoidance of progression, and improvement.

resultsWe included 884 patients (85% female), with a mean age of 13.0 ± 1.3 years and a mean Cobb angle of 28 ± 7°. In the higher BWT quartiles, we found larger scoliosis curves but also better final Cobb angle results. The dose–response curves showed statistically significant improvements for the outcomes END < 30° and improvement (outcomes improvements ranging 45–60% and 25–35%, respectively). The outcomes END < 50° and avoiding progression showed a ceiling effect due to a very high success rate (range 97–98% and 85–87%, respectively).

conclusionBWT > 18 h/d is associated with avoiding surgery (END < 50°), reduced progression, and increased improvement rates, and achieving END < 30°, which is particularly relevant because it reduces the risk of problems in adulthood. Decisions on daily BWT should be based on the desired outcomes and an honest conversation with the patients and parents.