Thigh and paraspinal muscles change after fusionless bipolar fixation for early onset scoliosis in type 2 spinal muscular atrophy: Modifications in the spinal and thigh muscles of subjects with SMA2 and early onset scoliosis.

Background: Spinal muscular atrophy is a severe, progressive autosomal recessive neuromuscular disorder associated with neuromuscular scoliosis. When bracing is not sufficient to control the deformity, early spinal surgery is required. To the best of our knowledge, no work in the literature have assessed modifications in spinal and thigh muscles of subjects with type 2 spinal muscular atrophy (SMA2) following spinal surgery.

Objective: This study aimed to better understand modifications in the spinal and thigh muscles of subjects with SMA2 and early onset scoliosis, before and after minimally invasive fusionless surgery.

Methods and settings: 20 SMA2 patients with confirmed scoliosis on bi-planar low-dose X-ray were included: 10 preoperative and 10 postoperative patients with a minimal follow-up of 5 years after surgery. The surgery consisted of a bilateral sliding rod construct extended from T1 to the sacrum, through a minimally invasive approach. All subjects had fat/water separation muscle magnetic resonance imaging from the spine to the thigh. The percentage of fat degeneration was compared before and after surgery. A quality-of-life survey was performed.

Results: Fat infiltration was diffuse and symmetric in both groups of patients, and on average six times more compared to control subjects previously published at thigh level. Adductors, sartorius, and gracilis were less affected with respectively, 51%, 56%, and 57% of fat fraction before surgery. Comparing the preoperative and postoperative groups, fat infiltration was higher in sartorius and multifidus after surgery (p < 0.05). No significant difference was found for the other muscles studied. These results did not affect quality of life.

Conclusion: This is the first study to compare fat infiltration of spinal and thigh muscles of SMA2 patients before and after minimally invasive surgery. Our results demonstrate that muscles were globally preserved apart from multifidus and sartorius which were more affected.