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

Background context: Recurrent 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. Purpose: The purpose of this study was to investigate the association of obesity with recurrent HNP after lumbar microdiscectomy. Study design: Retrospective Cohort. Patient sample: We 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 measures: The primary clinical outcomes were evidence of recurrent HNP on magnetic resonance imaging (MRI) and need for repeat surgery. Methods: All 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. Results: Seventy-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). Conclusions: Obesity was a strong and independent predictor of recurrent HNP after lumbar microdiscectomy. Surgeons should incorporate weight loss counseling into their preoperative discussions with patients.