Size Matters: Which Adolescent Patients Are Most Likely to Require Surgical Decompression for Lumbar Disk Herniations?

BACKGROUND: Lumbar herniated nucleus pulposis (HNP) occurs infrequently in the pediatric/adolescent population. A minority of patients with radicular symptoms fail to improve with conservative management and require discectomy. The authors hypothesize that children who ultimately require surgical intervention have an underlying lumbar stenosis predisposing them to continued symptoms. METHODS: Pediatric patients with a lumbar HNP on advanced imaging were retrospectively identified at a tertiary pediatric orthopaedic institution. Patients with spondylolisthesis, fractures, previous spine surgery, or structural thoracolumbar scoliosis were excluded. On sagittal magnetic resonance imagings, measurements were taken of the L4 and L5 vertebral body diameters (VBD) and canal diameters (CD) by 2 independent reviewers. Statistical analysis was performed using 2 sample T tests followed by logistic regression analysis. This was utilized to identify significant associations between CD and need for surgical decompression. RESULTS: A total of 76 patients (37 males/39 females) were identified with a lumbar HNP from 2001 to 2016. Eleven patients underwent discectomy. Sixty-five patients were managed conservatively. Age at magnetic resonance imaging was not different between groups (15.1±1.7 vs. 14.9±2.2 y, P=0.82). VBD at L4 and L5 were not different between groups (P=0.2 and 0.36, respectively). The reviewers had fair to good (0.584-0.854) interrater reliability correlation coefficients. CD was decreased in the surgically treated cohort at L4 (11.6±1.6 vs. 14.2±2.1 mm, P=0.0002) and at L5 (10.1±1.3 vs. 14.2±2.2 mm, P<0.00001). The ratio of CD:VBD was lower in the surgically treated group at L4 (0.36±0.06 vs. 0.46±0.08, P=0.0002) and L5 (0.31±0.68 vs. 0.45±0.08, P<0.00001). Patients with a L4 CD<12.6 mm were 18.8× more likely to require surgical decompression. 100% of patients with a L5 CD<12.36 mm ultimately underwent surgical decompression. CONCLUSIONS: Adolescent patients with congenital lumbar stenosis that develop a lumbar HNP are significantly more likely to require surgical decompression to relieve persistent radicular symptoms. A L4 CD<12.6 mm and a L5 CD<12.36 mm were highly correlated with the need for decompression. LEVEL OF EVIDENCE: Level III-prognostic study.