Obesity increases the risk of recurrent herniated nucleus pulposus after lumbar microdiscectomy

Background contextRecurrent herniation of the nucleus pulposus (HNP) frequently causes poor outcomes after lumbar discectomy. The relationship between obesity and recurrent HNP has not previously been reported.PurposeThe purpose of this study was to investigate the association of obesity with recurrent HNP after lumbar microdiscectomy.Study designRetrospective Cohort.Patient sampleWe reviewed all cases of one- or two-level lumbar microdiscectomy from L2–S1 performed by a single surgeon with a minimum follow-up of 6 months.Outcome measuresThe primary clinical outcomes were evidence of recurrent HNP on magnetic resonance imaging (MRI) and need for repeat surgery.MethodsAll patients with recurrent radicular pain or new neurological deficits underwent a postoperative MRI scan. Recurrent HNP was defined as a HNP at the same side and same level as the index procedure.ResultsSeventy-five patients were included in the study. The average body mass index (BMI) was 27.6±4.6. Thirty-two patients received an MRI scan. The time from operation to repeat MRI scan varied widely (3 days to 15 months). Eight patients (10.7%) had recurrent HNP. Four patients had persistent symptoms requiring reoperation (5.3%). The mean BMI of patients with recurrent HNP was significantly higher than that of those without recurrence (33.6±5.1 vs. 26.9±3.9, p<.001). In univariate analysis, obese patients (BMI ≥30) were 12 times more likely to have recurrent HNP than nonobese patients (odds ratio [OR]: 12.46, 95% confidence interval [CI]: 2.25–69.90). Obese patients were 30 times more likely to require reoperation (OR: 32.81, 95% CI: 1.67–642.70). Age, sex, smoking, and being a manual laborer were not significantly associated with recurrent HNP. A logistic regression analysis supported the findings of the univariate analysis. In a survival analysis using a Cox proportional hazards model, the hazard ratio of recurrent HNP for obese patients was 17 (OR: 17.08, 95% CI: 2.85–102.30, p=.002).ConclusionsObesity was a strong and independent predictor of recurrent HNP after lumbar microdiscectomy. Surgeons should incorporate weight loss counseling into their preoperative discussions with patients.