Longitudinal pulmonary outcomes after posterior spinal fusion in Duchenne muscular dystrophy: a retrospective cohort study

Introduction Whether posterior spinal fusion (PSF) alters pulmonary decline in patients with Duchenne muscular dystrophy (DMD) remains uncertain. This study evaluated longitudinal changes in pulmonary function, respiratory muscle strength after PSF, examined whether the magnitude of scoliosis correction was associated with postoperative pulmonary outcomes Methods We retrospectively reviewed patients with DMD who underwent PSF and had pulmonary function testing before and after surgery. The primary outcome was forced vital capacity (FVC) percent predicted, assessed preoperatively, at approximately 5–6 months postoperatively, and at final follow-up of approximately 2 years. Measured FVC, the FEV 1 /FVC ratio, and maximal inspiratory (MIP) and expiratory (MEP) pressures were secondary outcomes. Results Sixteen nonambulatory male patients were included at a mean age of 17.9 ± 2.9 years. The mean Cobb angle improved from 63.6° ± 15.4° preoperatively to 19.1° ± 13.3° postoperatively. Mean FVC percent predicted was unchanged from the preoperative to the early postoperative assessment (41.0% ± 15.5% vs 41.1% ± 18.0%; P = 0.511) but decreased to 34.4% ± 13.7% at final follow-up (mean change, − 8.9 percentage points; P = 0.006). MEP decreased during the early postoperative period ( P = 0.010) and no longer differed from baseline at final follow-up, whereas MIP was unchanged throughout. The magnitude of curve correction was not significantly associated with change in FVC percent predicted at either interval (ρ = − 0.45, P = 0.106 and ρ = − 0.43, P = 0.122). An association in the same direction with measured FVC (ρ = − 0.62, P = 0.019 and ρ = − 0.65, P = 0.012) was confined to the intervals spanning surgery and was absent between the early postoperative and final assessments (ρ = − 0.18, P = 0.565). Conclusions In nonambulatory patients with DMD, FVC percent predicted was unchanged early after PSF and declined by approximately 2 years, a trajectory consistent with the natural history of the disease. Greater curve correction was not associated with better pulmonary outcomes. These findings do not support pulmonary preservation as an expected benefit of deformity correction and reinforce the functional, postural, and quality-of-life goals of PSF.