Introduction. Redundant nerve roots (RNRs) are often observed in lumbar spinal stenosis (LSS). Several studies have demonstrated that RNRs are a factor contributing to poor postoperative outcomes in LSS patients. However, there have been few studies that evaluated the clinical significance of RNRs in LSS patients using patient-oriented questionnaires. The purpose of this study was to investigate the postoperative outcomes of LSS with RNRs using the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ).
Methods. A total of 227 patients (149 males and 78 females, mean age 72.4±8.5 years at surgery) who underwent posterior decompression for LSS at our hospital were included in this study. All patients were followed up at least 2 years after surgery. According to the findings of preoperative MRI, patients were divided into the RNRs (R) group and the non-RNRs (NR) group. Patient background, the number of affected vertebrae, surgical factors (operation time, blood loss, complications), JOABPEQ efficacy rate, and VAS scores (back pain, leg pain, leg numbness) before and at 2 years after surgery were compared in the two groups. The R group was further divided into loop shaped (L group) and serpentine shaped (S group) groups based on the shape, and the subgroup analysis between L and S groups was performed.
Results. The R and NR group consisted of 98 (71 males and 27 females, mean age 71.7 years) (43.2%) and 129 (78 males and 51 females, mean age 73 years) (56.8%) patients. There were no differences in all domains of patient background, surgical factors, and preoperative JOABPEQ and VAS scores between the two groups. While all VAS scores and the efficacy rate in the pain disorder domain(p=0.06), lumbar function domain(p=0.57), and mental health domain (p=0.20) of the JOABPEQ at 2 years after surgery were comparable, the efficacy rates in the walking ability domain (73.1% vs. 59.4%, p=0.04) and the social life function domain (63.4% vs. 49.2%, p=0.04) of the JOABPEQ were higher in the R group compared to the NR group, In the subgroup analysis, L and S group consisted of 43 and 55 patients. The efficacy rates in all domains of the JOABPEQ at 2 years after surgery were not significantly different between the L and S group.
Discussion. The prevalence rates of the RNRs in patients with LSS in this study was 41.7%, which was similar to previously reported percentages. Postoperative outcomes of LSS with RNRs have been reported through the analyses of JOA score, which is a physician-based outcome, and are therefore still controversial. Our results suggests that the posterior decompression surgery can provide the significant improvement of walking ability and social life function in LSS patients with RNRs compared to those without RNRs. In addition, although many previous reports have shown that the loop shaped RNRs is associated with poor postoperative outcomes, this study suggests that the shape of RNRs may not affect postoperative outcomes. Further studies are needed to explore the subtypes and extent of RNRs.