Relative risk factors of nerve root sedimentation sign (SedSign) in patients with severe central lumbar spinal stenosis (LSS)

The incidence of nerve root sedimentation sign (SedSign) was evaluated to explore potential pathogenesis in patients with severe lumbar spinal stenosis (LSS). In a total of 209 patients with severe LSS, 290 intervertebral levels were narrow, among which 248 showed a positive SedSign, giving a prevalence of 85.52%. Those levels with a positive SedSign were further analyzed relative to those with a negative SedSign. There was no significant difference between the two groups for the cross-sectional area (CSA) or the posteroanterior diameter (PAD). In contrast, there was a significant difference between the groups for the grade of degenerative facet joint (DFJ) (p < 0.05), the thickness of ligamentum flavum (TLF) (p < 0.01), and the cross-sectional area difference (CSAD) (p < 0.01). In addition, receiver operating characteristic (ROC) curves were used to identify associated factors. The area under the ROC curve for PAD was 0.608 (p < 0.05), for DFJ was 0.634 (p < 0.05), for TLF was 0.74 (p < 0.01), and for CSAD was 0.911 (p < 0.01). In summary, a positive SedSign has notable advantages in assisting with the diagnosis of severe LSS. Compression of the dural sac from the rear may be the main risk factors of a positive SedSign.