Background: Spinal muscular atrophy (SMA) is caused by abnormalities of the survival motor neuron (SMN) 1 gene, leading to a loss of spinal cord alpha motor neurons. Disease-modifying agents (DMA) targeting the involved genes (SMN1 and SMN2) have improved gross motor function, but impacts on post-operative outcomes after scoliosis correction remain unclear.
Objectives: The purpose of this study was to evaluate post-operative outcomes following scoliosis surgery, specifically analyzing the impact of functional level, genetic severity, and DMA use. We hypothesized that genetic severity by decreased SMN2 copy # would increase the risk of post-operative complications by Clavien-Dindo (CD) grading (1-2=less severe, 3-5=more severe), while DMA use would be protective.
Results: 74 patients (40% female) with SMA type I(21,28%), II(40,54%), III(11,15%), unknown (2,3%) met the inclusion criteria, with total post-operative follow-up duration 8.0±4.1 years. Surgery type was posterior spinal fusion for 53(72%) and growing rods for 21(28%), with mean age at surgery 12.0±2.4 and 6.2±2.9 years, respectively. Primary curve and pelvic obliquity correction was 44±20° (74±22° preop, p<0.001) and 11±9° (17±11° preop, p<0.001), respectively. DMA treatment was utilized preoperatively and post-operatively for 17(23%) and 57(77%) patients, mean duration 2.2±0.8 years and 3.8±1.3 years, respectively. SMN2 copy # was available for 31(42%) patients: 13(42%) <3, 18(58%) ≥3. Postoperative complication rates were not significantly influenced by SMA type or SMN2 copy number. DMA use before surgery was associated with: similar rates of postoperative complications but were less severe (6 vs 28% CD 3-5 grades, for DMA vs no DMA use, respectively, p=0.05), decreased days intubated (0.2 vs 1.6, p<0.0001), and decreased hospital length of stay (LOS, 4.6 vs 11.0 days, p=0.0001). Overall, %FVC decreased from preoperative to final follow-up (60.0% to 51.8%, p=0.002), unrelated to surgery type (p=0.98), DMA use (p=0.26), or SMN2 copy # (p=0.27).
Conclusions: Post-operative complications, though high in frequency overall, were typically less severe (CD 1-2) with preoperative DMA treatment. Pulmonary function was not improved after scoliosis surgery at final follow-up, nor was it affected by fusion vs growth friendly procedures, DMA treatment, or disease severity. Improvements in hospital LOS and days intubated postoperatively are potential benefits of preoperative DMA treatment.