Early dynamic changes within the spine following posterior fusion using hybrid instrumentation in adolescents with idiopathic scoliosis: a gait analysis study

Introduction In adolescent idiopathic scoliosis (AIS) patients, mechanical consequences of posterior spinal fusion within the spine remain unclear. Through dynamic assessment, gait analysis could help elucidating this particular point. The aim of this study was to describe early changes within the spine following fusion with hybrid instrumentation in adolescents with idiopathic scoliosis, using gait analysis Materials and methods We conducted a single-centre prospective study including AIS patients scheduled for posterior spinal fusion (PSF) using hybrid instrumentation with sublaminar bands. Patients underwent radiographic and gait analyses preoperatively and during early postoperative period. Among gait parameters, motion of cervicothoracic, thoracolumbar and lumbosacral junctions was measured in the three planes. Results We included 55 patients (mean age 15 years, 84% girls). Fusion was performed on 12 levels and mean follow-up was 8 months. There was a moderately strong correlation between thoracolumbar sagittal motion and lumbosacral junction pre-and postoperatively (R = − 0.6413 and R = − 0.7040, respectively, all p < 0.001), meaning that the more thoracolumbar junction was in extension, the more lumbosacral extension movements decreased. There was a trend to significance between postoperative SVA change and thoracolumbar sagittal motion change (R = − 0.2550, p = 0.059). Discussion This is the first series reporting dynamic changes within the spine following PSF using hybrid instrumentation in AIS patients. PSF led to symmetrization of gait pattern. In the sagittal plane, we found that thoracolumbar extension within the fused area led to decreased extension at cervicothoracic and lumbosacral junctions. Even though consequences of such phenomenon are unclear, attention must be paid not to give a too posterior alignment when performing PSF for AIS patients.