Transverse Posterior Canal Stenosis as a Predictor of Redundant Nerve Roots in Lumbar Stenosis.

Objectives: Redundant nerve roots (RNR) of the lumbar cauda equina is an important imaging presentation associated with lumbar spinal stenosis (LSS) and considered a potentially powerful prognostic indicator of poor functional recovery after surgery for symptomatic LSS. However, factors contributing to RNR remain undefined. This study aimed to investigate the effects of sagittal and transverse stenosis of the lumbar spinal canal on RNR formation.

Methods: A retrospective case-control study was conducted in 124 LSS patients over 18 years of age. They were divided into a RNR group and a non-RNR group. Correlations of LSS imaging parameters and pathogenic factors with RNR formation were analyzed.

Results: Excluding 16 cases of non-degenerative LSS, 108 patients were finally included for analysis, including 33 patients (30.6%) in RNR group and 75 patients in non-RNR group. Age, included angle of the ligamentum flavum, maximum thickness of the ligamentum flavum, area of the dural sac, total area of the bilateral facet joints, and transverse diameter of the posterior spinal canal (PSC) showed statistically significant differences between the two groups (p≤0.001). The optimal cut-off point for the transverse diameter of PSC was 9.94mm. There was a significant positive correlation of transverse diameter of PSC and area of the dural sac with the presence of RNR (r=0.5897, p<0.001).

Conclusions: Transverse stenosis of PSC is the key factor contributing to RNR formation in LSS patients and the value < 10mm can be used to predict the risk of RNR formation in LSS patients.