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

Abstract

Redundant nerve roots (RNR) of the lumbar cauda equina are 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. A retrospective case-control study was conducted in 124 LSS patients over 18 years of age. They were divided into an RNR group and a non-RNR group. Correlations of LSS imaging parameters and pathogenic factors with RNR formation were analyzed. Excluding 16 cases of nondegenerative LSS, 108 patients were finally included for analysis, including 33 patients (30.6%) in the RNR group and 75 patients in the 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 2 groups (P ≤ 0.001). The optimal cutoff point for the transverse diameter of PSC was 9.94 mm. 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). Transverse stenosis of PSC is the key factor contributing to RNR formation in LSS patients, and the value <10 mm can be used to predict the risk of RNR formation in LSS patients.