Background:

Progressive C-shaped scoliosis with marked pelvic obliquity is common to spinal muscular atrophy (SMA). Reducing the number of procedures with effective deformity control is critical to minimize the risk of pulmonary complications. This study reports the preliminary results of magnetically controlled growing rods (MCGR) in SMA-related collapsing spine deformity.

Methods:

Inclusion criteria for this retrospective review were: (1) SMA type 2 patients, (2) early onset scoliosis (below 10 y), (3) collapsing spine deformity with pelvic obliquity, (4) growth-friendly scoliosis treatment with MCGR, (5) in between 2014 and 2017. Extracted data included demographic and clinical information, radiologic parameters, surgical details, and final status of the patients.

Results:

A total of 11 patients (7 boys, 4 girls) were included. The average age at index surgery was 8.2 (6 to 10) years. Dual MCGR was implanted in 8 patients. In 3 patients, because of curve rigidity and inability of apex to be brought into the stable zone, apical fusion with gliding connectors (convexity) and a single MCGR (concavity) was preferred. Instrumentation included the pelvis in 9 and stopped at the lumbar spine (L3) in 2 patients at the index procedure. Average preoperative deformity of 81.8 degrees (66 to 115) decreased to 29 degrees (11 to 57) postoperatively and was 26 degrees at average 35 months (16 to 59). Pelvic obliquity of 20.9 degrees (11 to 30) decreased to 4.9 degrees (2 to 8) after index surgery and was 6.5 degrees (2 to 16) at the last follow-up. T1-S1 height of 329 mm (280 to 376) after index surgery increased to 356 mm (312 to 390) after 9.2 (4 to 20) outpatient lengthening. No neurologic, infectious, or implant-related complication was recorded. Distal adding-on deformity occurred in 2 patients without initial pelvic fixation.One patient deceased secondary to pneumonia at 16 months after surgery.

Conclusions:

Short-term results indicate that MCGR may be a good option in SMA-associated collapsing spine deformity to reduce the burden of repetitive lengthening procedures. The authors recommend apical deformity control in the convex side in case of curve rigidity. In addition, including the pelvis in the instrumentation at index surgery is critical to prevent distal adding-on.

Level of evidence:

Level IV-retrospective case series.