Purpose of the study: There are limited data on the behaviour of intervetebral discs below arthrodesis for scoliosis. We have developed a reproducible MRI protocol for measuring the volume of the different components of the intervertebral disc and an original method for measuring disc hydration (ratio between the volume of the nucleus and the global volume). The discs studied were below fusions. The purpose of this study was to search for correlations between the disc volume and hydration and clinical outcome assess on standard x-rays.

Material and method: This was a prospective study conducted from 2005 to 2008. The series included 46 children with idiopathic scoliosis requiring arthrodesis (41 girls, 5 boys, mean age 15 years). The protocol included anteroposterior and lateral x-rays and MRI pre- and postoperatively and at 3 months and 1 year. 3D MRI reconstruction relied on a standard protocol validated in our research laboratory. These reconstructions produced a measurement of disc volume and its state of hydration. Two groups were identified using the plain x-rays: group A with what was considered to be a good result, well balanced spine and a horizontal disc subjacent to the arthrodesis; group B with what was considered a poor result with an unbalanced spine or oblique subjacent disc. Two groups were also defined as a function of postoperative reduction of the COBB angle. Group A’, reduction > 65% and group B’ reduction < 65%. Student’s t test was used for the statistical analysis.

Results: MRI series were obtained in 46 patients at 3 months and 28 at 1 year. At 3 months, there was an increase in nuclear volume (9.3%, p=0.056), global volume (5.2%, p=0.0017) and hydration (4.6%, p=0.056). At 1 year, the significant increases were, respectively, 15.4, 5.3 and 11.6%. At 3 months, there was a significant increase in disc volume in the groups A and A’. In group B, increase in disc volume (4.%, p=0.02) and hydration (13.9%, p=0.07) was only seen at 1 year.

Conclusion: This work enabled us to establish a significant correlation between increased disc volume and hydration as measured on the MRI and clinical outcome as assessed on the plain x-rays.

Purpose of the study: The effect of idiopathic scoliosis surgery on walking capacity has rare been studied. Results published in the literature have been discordant: reduced velocity, step rate and stride length for Lenke et al; no change for Engsber et al. We conducted a prospective study to analyze gait parameters after surgery for idiopathic scoliosis.

Material and methods: This study was conducted in 46 patients who underwent surgery for idiopathic scoliosis. Mean age was 15 years (range 12–22). Mean angle was 56° (range 40–94°). A posterior approach was used for reduction and fusion in all patients. Mean postoperative angle was 20° (range 8–64°). There were no neurological, mechanical or infectious complications. Gait analysis was performed with a locometer to record spatial and temporal gait parameters preoperatively then postoperatively at 10 days, and 3, 6, and 12 months. ANOVA was performed.

Results: Preoperatively, mean±SD values were: velocity: 1.48±0.14 m/s; step rate: 132±9 steps/min; stride length 67±6.7 cm; balancing time: 0.39±0.03 s; double-stance time 0.07±0.03 s. These values were lower than reported for health adults using the same measurement instrument. All parameters were modified immediately after surgery (p< 0.05) but there was no significant difference between the pre- and postoperative values at 3, 6, and 12 months.

Conclusion: Corrective fusion via a posterior approach for the treatment of idiopathic scoliosis does not affect spatial and temporal gait parameters.

Purpose of the study: Surgical strategies for high-grade spondylolisthesis are controversial. The main subject of debate concerns the indications for reduction or in situ fusion. We present mid-term results obtained in a series of patients with high-grade spondylolisthesis treated by posterior reduction and fusion.

Material and methods: Sixteen patient who had undergone surgery for spondylolisthesis of the superior isthmus > 50% were reviewed. Mean age was 12 years (range 9–16 years). Preoperatively, all patients were symptomatic with lumbalgia, truncated radicular pain, and gait anomalies. Surgical treatment consisted in a single posterior approach, L5 laminectomy, curettage of the L5-S1 disc combined with excision of the S1 dome, L4-S1 instrumented reduction, anterior L5-S1 and posterolateral L4S1 arthrodesis. Postoperative immobilization was achieved with a resin lumbar cast with crural stabilization for three months then a lumbar orthesis for three months. Clinical and radiographic outcome was assessed at 44 months on average (range 10–260 months).

Results: Clinically, 14 patients were pain free and had resumed their former activities. One patient complained of intermittent pain. No improvement was observed in one patient. Radiographic results were: displacement 78% (range 52–100%) preoperatively and 30% (8–95%) at last follow-up. The L5S1 displacement angle was 14° kyphosis (range 8–30°) preoperatively and 9° lordosis (range 3–12°) at last follow-up excepting one case with complications. The pelvic incidence was 85° (range 65–100°) preoperatively and 74° (range 50–90°) at last follow-up. Complications: There was one early infection treated by wash-out debridement and antibiotics without removing implants. Disassembly of the implanted material in one patient with a poor clinical result led to complete recurrence and lumbosacral kyphosis. Sacral screw fracture was diagnosed in six patients on average one year after surgery but without any progression or recurrence of the displacement. There were no neurological complications.

Discussion and conclusion: Posterior reduction enables restoration of a good sagittal balance. More than the reduction, it is particularly important to restore the lumbosacral junction in a lordosis position to guarantee long-term stability. This technique is a difficult surgical challenge and raises the risk of recurrence and potential neurological complications.