Risk factor of residual leg numbness after lumbar microdiscectomy for lumbar disc herniation

Although patients with lumbar disc herniation (LDH) can achieve significant relief from lower back and leg pain after lumbar microdiscectomy, a few patients complain of discomfort due to residual leg numbness (RLN). This study aimed to identify potential risk factors for RLN after lumbar microdiscectomy. We prospectively collected and analyzed patients with LDH who underwent microdiscectomy between September 2016 and December 2020. All included patients had preoperative LN symptoms. Patients with RLN were defined as those with LN at the last follow-up. The relationships between RLN and sex, age, body mass index (BMI), current smoking status, diabetes mellitus, revision surgery, preoperative LN Numeric Rating Scale (NRS) score, duration of preoperative LN, RLN at discharge, sagittal range of motion (SROM), Modic change, disc Pfirrmann grade were analyzed. The RLN was observed in 33.5% (112/334) of patients at the last follow-up. No significant differences were observed in age, sex, BMI, current smoking status, or diabetes between the RLN and non-RLN groups. The preoperative LN NRS score, preoperative LN duration, rate of RLN at discharge, and revision surgery were significantly higher in the RLN group than those in the non-RLN group. Multivariate logistic regression analysis identified the preoperative LN NRS score, duration of preoperative LN, RLN at discharge, revision surgery, and SROM as risk factors for RLN in the long-term follow-up. Patients with higher preoperative LN NRS scores and SROM, longer preoperative LN duration, RLN at discharge, and revision surgery were more likely to experience RNL after lumbar microdiscectomy.