Curve evolution during bracing in children with scoliosis secondary to early-onset neurofibromatosis type 1: indicators of rapid curve progression

BACKGROUND: Scoliosis secondary to neurofibromatosis type 1 (NF1) in children aged <10 years is an important etiology of early-onset scoliosis (EOS). This study was performed to investigate the curve evolution of patients with EOS secondary to NF1 undergoing bracing treatment and to analyze high-risk indicators of rapid curve progression. METHODS: Children with EOS due to NF1 who underwent bracing treatment from 2010 to 2017 were retrospectively reviewed. The angle velocity (AV) at each visit was calculated, and patients with rapid curve progression (AV of >10°/year) were identified. The age at modulation and the AV before and after modulation were obtained. Patients with (n = 18) and without rapid curve progression (n = 10) were statistically compared. RESULTS: Twenty-eight patients with a mean age of 6.5 ± 1.9 years at the initial visit were reviewed. The mean Cobb angle of the main curve was 41.7° ± 2.4° at the initial visit and increased to 67.1° ± 8.6° during a mean follow-up of 44.1 ± 8.5 months. The overall AV was 6.6° ± 2.4°/year for all patients. At the last follow-up, all patients presented curve progression of >5°, and 20 (71%) patients had progressed by >20°. Rapid curve progression was observed in 18 (64%) patients and was associated with younger age at the initial visit and a higher incidence of modulation change during follow-up (t = 2.868, P = 0.008 and <0.001, respectively). The mean AV was 4.4° ± 1.2°/year before modulation and 11.8° ± 2.7°/year after modulation (t = 11.477, P < 0.010). CONCLUSIONS: Curve progression of >10°/year is associated with younger age at the initial visit, and modulation change indicated the occurrence of the rapid curve progression phase.