Spontaneous induced bone fusion in minimally invasive fusionless bipolar fixation in neuromuscular scoliosis: a computed tomography analysis.

Abstract

Posterior spinal fusion (PSF) at skeletal maturity is still the gold standard in children with neuromuscular scoliosis (NMS) who underwent fusionless surgery. The aim of this computed tomography (CT) study was to quantify the spontaneous bone fusion at the end of a lengthening program by minimally invasive fusionless bipolar fixation (MIFBF), that could avoid PSF. NMS operated on with MIFBF from T1 to the pelvis and at final lengthening program were included. CT was performed at least five years postoperatively. The autofusion was classified as completely or not fused at the facets joint (on both coronal and sagittal plane, right and left side, from T1 to L5), and around the rods (axial plane, right and left side, from T5 to L5). Vertebral body heights were assessed. Ten patients were included (10.7y±2 at initial surgery). Mean Cobb angle was 82±20 preoperatively and 37±13 at last follow-up. CT were performed on average 6.7y±1.7 after initial surgery. Mean preoperative and last follow-up thoracic vertebrae height were respectively 13.5 mm±1.7 and 17.4 mm±1.7 (p<0.001). 93% facets joints were fused (out of 320 analyzed joints), corresponding to 15/16 vertebral levels. Ossification around the rods was observed in 6.5±2.4 levels out of 13 in the convex side, and 4.2±2.2 in the concave side (p=0.04). This first computed quantitative study showed MIFBF in NMS preserved spinal growth, while it induced 93% of facet joints fusion. This could be is an additional argument when questionning the real need for PSF at skeletal maturity.