MRI evaluation of the hydration status of non-pathological lumbar intervertebral discs in a pediatric population.

INTRODUCTION: The intervertebral disc (IVD) is made up of the annulus fibrosus (AF) and the nucleus pulposus (NP) - an inert hydrated complex. The ability of the IVD to deform is correlated to that of the NP and depends on its hydration. As the IVD ages, its hydration decreases along with its ability to deform. In adolescent idiopathic scoliosis, one of the etiological hypotheses pertains to the IVD, thus making its condition relevant for the diagnosis and monitoring of this pathology. HYPOTHESIS: IVD hydration depends on sex, age and spine level in an asymptomatic pediatric population. The corollary is data on a control group of healthy subjects. MATERIAL AND METHODS: A cohort of 98 subjects with normal spine MRI was enrolled; their mean age was 13.3 years. The disc volume and hydration of each IVD was evaluated on T2-weighted MRI sequences, using previously validated image processing software. This evaluation focused on the lumbar spine, from the thoracolumbar junction to the lumbosacral junction. It was assumed that IVD hydration was related to the ratio of NP and AF volumes. A mixed multivariate linear analysis was used to explore the impact of age, sex and spinal level on disc hydration. RESULTS: Disc hydration was higher overall in boys than in girls, but this difference was not significant. Hydration increased with age by +0.005 for each additional year (p=0.0213). Disc hydration appears to be higher at the thoracolumbar junction than the lumbar spine, although this difference was not significant. CONCLUSION: Through this MRI study, we established a database of non-pathological lumbar disc hydration as a function of age, sex and spinal segment along with 95% confidence intervals. LEVEL OF EVIDENCE: IV.

Surgical management of burst fractures in children and adolescents: A Multicentre Retrospective Study.

BACKGROUND: Spinal fractures are rare in children, in whom they contribute only 2% to 5% of all traumatic spinal injuries. The management of burst fractures is well standardised in adults but remains controversial in paediatric patients, due to specific growth-related considerations. The objective of this study was to assess the clinical and radiographic outcomes of surgical management in a multicentre cohort of paediatric patients with burst fractures, in order to devise an optimal therapeutic strategy. HYPOTHESIS: A therapeutic strategy for burst fractures in children and adolescents can be devised based on data from a patient cohort and on previously published information. MATERIAL AND METHODS: Patients younger than 18 years who were managed surgically for one or more burst fractures (Magerl A3) were included in this retrospective multicentre study. Clinical, radiographic, and surgical data were collected before surgery, within 3 months after surgery, and 2 years after surgery. The primary surgical approach was posterior in all patients. Computed tomography (CT) was performed post-operatively to assess the extent of anterior bone loss in order to determine whether anterior fusion was required. The 26 included patients had a mean age of 15±1 years. The thoraco-lumbar spine was involved in 15 (57%) patients. Surgery consisted in correction by instrumentation and posterior fusion only in 14 patients and in posterior correction with anterior fusion in 12 patients. In 10 (38%) patients, the instrumentation extended one vertebra above and one vertebra below the fractured vertebra. RESULTS: Significant correction of the vertebral kyphosis was achieved (17°±11° before vs. 4°±2° after surgery, p=0.001). Anterior and posterior vertebral heights were significantly increased (15±3mm vs. 20±3mm, p=0.01 and 23±4mm vs. 26±4mm, p=0.04, respectively). DISCUSSION: The decision to perform surgery rests on the degree of kyphosis and presence of instability. Anterior bone grafting can be added if the instrumentation is short or a bone defect persists after posterior correction. Correction of the local kyphosis is important to prevent sagittal malalignment with its adverse functional consequences in adulthood. Neural decompression must be performed in patients with neurological deficits. LEVEL OF EVIDENCE: IV.