MRI Radiological Predictors of Requiring Microscopic Lumbar Discectomy After Lumbar Disc Herniation.

Abstract

Retrospective cohort study. To investigate radiological differences in lumbar disc herniations (herniated nucleus pulposus [HNP]) between patients receiving microscopic lumbar discectomy (MLD) and nonoperative patients. Patients with primary treatment for an HNP at a single academic institution between November 2012 to March 2017 were divided into MLD and nonoperative treatment groups. Using magnetic resonance imaging (MRI), axial HNP area; axial canal area; HNP canal compromise; HNP cephalad/caudal migration and HNP MRI signal (black, gray, or mixed) were measured. <i>T</i> test and chi-square analyses compared differences in the groups, binary logistic regression analysis determined odds ratios (ORs), and decision tree analysis compared the cutoff values for risk factors. A total of 285 patients (78 MLD, 207 nonoperative) were included. Risk factors for MLD treatment included larger axial HNP area (<i>P</i> < .01, OR = 1.01), caudal migration, and migration magnitude (<i>P</i> < .05, OR = 1.90; <i>P</i> < .01, OR = 1.14), and gray HNP MRI signal (<i>P</i> < .01, OR = 5.42). Cutoff values for risks included axial HNP area (70.52 mm², OR = 2.66, <i>P</i> < .01), HNP canal compromise (20.0%, OR = 3.29, <i>P</i> < .01), and cephalad/caudal migration (6.8 mm, OR = 2.43, <i>P</i> < .01). MLD risk for those with gray HNP MRI signal (67.6% alone) increased when combined with axial HNP area >70.52 mm² (75.5%, <i>P</i> = .01) and HNP canal compromise >20.0% (71.1%, <i>P</i> = .05) cutoffs. MLD risk in patients with cephalad/caudal migration >6.8 mm (40.5% alone) increased when combined with axial HNP area and HNP canal compromise (52.4%, 50%; <i>P</i> < .01). Patients who underwent MLD treatment had significantly different axial HNP area, frequency of caudal migration, magnitude of cephalad/caudal migration, and disc herniation MRI signal compared to patients with nonoperative treatment.