Brace Treatment Is Associated with Lower Curve Progression in Moderate Adolescent Idiopathic Scoliosis, While Psychosocial Outcomes Are Driven by Depressive Symptoms and Curve Progression

Background: The impact of thoracolumbosacral orthosis (TLSO) bracing on sagittal spinopelvic alignment and psychosocial outcomes in adolescent idiopathic scoliosis (AIS) remains debated. Methods: This retrospective comparative study included 120 girls (10–18 years) with AIS (baseline Cobb angle 20–40°) and skeletal immaturity (Risser 0–1). Patients were managed with a thoracolumbosacral orthosis (TLSO) brace (n = 60) or observation alone (n = 60). Standing posteroanterior and lateral full-spine radiographs were obtained at baseline and at 24 ± 6 months; follow-up radiographs were acquired out of brace after a standardized 48 h brace-free interval. They were used to measure coronal and sagittal spinopelvic parameters. Patient-reported outcomes included the Scoliosis Research Society-22r (SRS-22r), Pediatric Quality of Life Inventory (PedsQL), Spinal Appearance Questionnaire (SAQ), Trunk Appearance Perception Scale (TAPS), and Beck Depression Inventory (BDI). The primary endpoint was curve progression (≥5° increase or exceeding 40°) at 24 months. Multivariable regression was used to adjust for baseline Cobb angle and maturity. Mean follow-up was 24 ± 6 months. Results: Mean Cobb change was +1.2° in the brace group vs. +7.3° in the observation group (group × time interaction p < 0.001). Progression (≥5°) occurred in 15% vs. 45%, respectively, and 18% of observed patients exceeded 40° (risk ratio 0.33, 95% CI 0.17–0.65; number needed to treat 4, 95% CI 3–7). Sagittal spinopelvic parameters showed no significant group-by-time interaction. No significant between-group differences were observed in SRS-22r, PedsQL, SAQ, TAPS, or BDI at baseline or follow-up. Patients with curve progression exhibited worse appearance-related scores. In multivariable analysis, depressive symptoms were the strongest determinant of PedsQL (β = −0.55, p < 0.001). Conclusions: Brace treatment was associated with reduced curve progression in girls with moderate AIS. Over approximately two years of follow-up, we did not observe clinically relevant between-group differences in sagittal spinopelvic alignment or psychosocial patient-reported outcomes. Given the retrospective, non-randomized design and self-reported adherence, psychosocial findings should be interpreted cautiously and require confirmation in prospective, objectively monitored, psychologically informed bracing studies.