Outcomes of Primary Posterior Spinal Fusion for Scoliosis in Spinal Muscular Atrophy: Clinical, Radiographic, and Pulmonary Outcomes and Complications.

BACKGROUND: Spinal muscular atrophy (SMA) is a progressive neuromuscular disease commonly including progressive scoliosis resulting in severe deformity and negatively affecting pulmonary function. Surgical correction and stabilization of this progressive deformity is generally recommended; however, the timing and method of surgical fixation remains controversial.

METHODS: Retrospective review of clinical, radiographic, and pulmonary function data from 16 children with SMA and surgically treated scoliosis between 1985 and 2013. Radiographic data included direct measures of major curve, coronal balance, pelvic obliquity, T1-T12 height, T1-S1 height, and T1-rod length. Estimations of rib collapse, thoracic cavity shape, and space-available-for-lung (T6:T12, width ratio; T6:T10, rib-vertebral-angle difference ratios; and lung height) were determined. Eleven patients were able to complete pulmonary function testing. Results were compared with published outcomes for growing rod constructs.

RESULTS: Posterior spinal fusion was performed at an average age of 9.8±3.6 years. The mean age at most recent follow-up was 19.4 years (range, 10 to 37 y), with a mean follow-up of 10.1 years (range, 3.1 to 26 y). Radiographic measurements improved from preoperative to latest follow-up as follows: major curve, 78±20 degrees to 27±24 degrees; coronal balance, 4.1±4.0 cm to 1.9±2.2 cm; pelvic obliquity (median), 23 to 5 degrees; T1-T12 height, 19±3 cm to 22±3 cm; T1-S1 height, 31±7 cm to 36±6 cm; T1-rod length, 0.8±1.1 cm (postop) to 2.8±1.6 cm (final); and space-available-for-lung ratio, 0.88±0.26 to 0.95±0.25. Rib collapse continued throughout the follow-up period in all but 1 patient. Pulmonary function testing demonstrated a decrease in rate of decline in forced vital capacity and forced expiratory volume when comparing preoperative with postoperative rates. Mean length of stay was 7.8±4.4 days. Complications included reintubation for low tidal volumes (n=1), pneumonia (n=1), superficial wound breakdown (n=1), and superficial infection (n=1).

CONCLUSIONS: Definitive posterior spinal fusion for treatment of scoliosis associated with SMA is effective at controlling curve progression and pelvic obliquity without negatively impacting the space-available-for-lung ratio, trunk height, or pulmonary function at 10 years follow-up.

LEVEL OF EVIDENCE: Therapeutic Level IV.