Background. Emerging research evidence indicates that standing MRI reveals abnormalities that are missed on supine MRI. Our previous study demonstrated that the dural sac cross-sectional area (DCSA) on MRI was reduced significantly from supine to standing position, and the DCSA changes significantly correlated with symptoms in patients with lumbar spinal stenosis. However, the correlation between dynamic plain radiographs and DCSA in patients with degenerative spondylolisthesis (DS) remains to be fully elucidated. The purpose of this study was to investigate the dynamic changes and correlations between standing MRI and plain radiographs in patients with DS.
Methods. Patients with DS exhibiting translation of 2 mm or more on neutral standing radiograph from January 2015 to October 2022 were retrospectively enrolled in this study. The translation in plain radiographs, and in supine and standing MRI, as well as the DCSA in MRI, were recorded by two independent observers. Interobserver and intraobserver correlation coefficients were calculated. The translations between flexion and extension standing radiographs, translations between supine and standing MRI, translations between neutral standing radiograph and standing MRI, and the DCSA between supine and standing MRI were calculated and compared. The correlation between neutral standing radiograph and MRI (supine and standing), and correlation between translations from flexion to extension radiographs and DCSA changes from supine to standing MRI were analyzed.
Results. A total of 56 consecutive patients (34 males and 22 females) with an average age of 58.2 years were enrolled. Standing MRI demonstrated significantly larger translation and smaller DCSA than supine MRI, and smaller translation than neutral standing radiograph (all p < .05). The interobserver and intraobserver correlation coefficients ranged from 0.76 to 0.87 mm, and from 0.77 to 0.90 mm, respectively. The translations of neutral standing radiograph showed significant correlation with that observed on standing MRI (r = 0.63, p < .05). Furthermore, the translations from flexion to extension standing radiographs correlated strongly with DCSA changes from supine to standing MRI (r = 0.72, p < .05).
Conclusions. Standing MRI demonstrated a significantly larger translation and smaller DCSA than supine MRI. And the translations in dynamic radiographs correlated strongly with the DCSA changes detected on standing MRI. These results suggest that standing MRI may be a useful imaging study for detecting translations in patients with DS. Further studies are warranted to reveal more values of the findings on standing MRI and provide clinical significance in patients with DS.
