Study design: To assess the rate of decline in pulmonary function in Duchenne muscular dystrophy (DMD) before and after posterior spinal fusion for scoliosis.
Objective: To compare the rate of respiratory decline using percent normal forced vital capacity (%FVC) measurements before and after posterior spinal fusion.
Summary of background data: Posterior spinal fusion for scoliosis is used widely in DMD, although the long-term pulmonary effects have not been well established.
Methods: Fifty-six patients were assessed. Percent forced vital capacity was the outcome parameter with data analysis using a mixed-model repeated-measures ANOVA and paired t tests. Group 1: Inclusion criteria were a diagnosis of DMD, 2 or more pulmonary function tests presurgery, and 2 or more postsurgery. Group 2: The rates of respiratory decline before and after spinal fusion for the whole study population were determined by within-subjects mixed-model regression analysis to account for the varying number of FVC studies between patients and unequal spacing between tests.
Results: Group 1: 20 patients. Mean length of time of respiratory value determination was 2.5 +/- 1.0 years presurgery and 5.6 +/- 2.8 years postsurgery. Mean rate of decline presurgery was 8.0% +/- 4.1% per year, which decreased to 3.9% +/- 1.9% per year postsurgery (paired t test = 4.58, P < 0.0001). Group 2: 56 patients. The respiratory value determinations ranged from 4 years presurgery to 8 years postsurgery. The rates of respiratory decline based on the whole study population were 4% per year presurgery, which decreased to 1.75% per year postsurgery (F-test comparison of slopes = 19.71, P < 0.0001).
Conclusions: Posterior spinal fusion for scoliosis in DMD is associated with a significant decrease in the rate of respiratory decline postsurgery compared with presurgery rates.