Lumbar degenerative spondylolisthesis (LDS) is a common degenerative disease that particularly affects the elderly. LDS can occur in any segment of the spine but is most commonly found in the L4/L5 segment. In the present study, a quantitative study of lumbar MRI measurements was conducted to identify predisposing factors indicative of spinal instability in patients with L4/L5 LDS. In total, 81 patients [58 patients in the stable group (SG) and 23 patients in the unstable group (UG)] who were diagnosed with L4/L5 LDS on X-ray and MRI between January 2021 and January 2022 were included in this study. Disk height, disk signal intensity on T1-weighted (T1W) and T2-weighted (T2W) images, facet joint fluid thickness, and ligamentum flavum thickness were measured on MRI, and the differences in these parameters between the two groups were evaluated. The receiver operating characteristic curve was generated, and the area under the curve (AUC), cut-off value, sensitivity (Se), specificity (Sp), positive predictive value (PPV), and negative predictive value (NPV) were calculated for parameters found to be significantly different between the two groups. The facet joint fluid was significantly thicker in the UG than in the SG (P<0.01), and a cut-off value of 1.45 mm was found to have an AUC of 0.77 and an SE, SP, PPV, and NPV of 73.9, 67.2, 69.3, and 69.77%, respectively. No significant differences were identified between the two groups for mean disk height, ligamentum flavum thickness, or disk signal intensity on T1W or T2W images. The facet joint fluid thickness on axial T2W images may represent a useful predictor of spinal instability in patients with LDS. Therefore, spinal instability should be assessed, and additional evaluation methods, such as standing lateral flexion-extension radiographs, should be performed when facet fluid is detected on lumbar MRI.
Keywords: degenerative spondylolisthesis; facet joint fluid; lumbar MRI; segmental instability; standing lateral and flexion-extension films.
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