LAUSR

OBJECTIVE To assess the dynamic change of the dural sac size in patients with lumbar spinal stenosis (LSS) from supine to standing position and their correlations with clinical symptoms. METHODS A final of 110 patients with LSS were prospectively enrolled to undergo both supine (0°) and standing (78°) MRI. Dural sac cross sectional area (DCSA) and dural sac anteroposterior diameter (DAPD) at the most constricted spinal level in supine and standing MRI were measured and compared. The clinical symptoms were assessed by duration of disease, claudication distance, visual analogue scale (VAS) of leg pain, and Chinese Oswestry Disability Index (ODI) score of low back pain. The correlation between the above parameters and clinical symptoms were analyzed by Pearson correlation coefficients (r). RESULTS Mean minimum DCSA and DAPD in standing position were significantly (both p values < 0.01) smaller than that in supine position. DCSA and DAPD in standing MRI and their changes had better correlation with the intermittent claudication distance and VAS score of leg pain than that in supine position. A more than 15 mm2 reduction of DSCA was observed in patients with shorter claudication distance and severer VAS of leg pain (both p values < 0.01). CONCLUSIONS Dural sac size on MRI was reduced significantly from supine to standing position. Standing MRI and the changes of DCSA significantly correlated with claudication distance and VAS of leg pain in LSS patients. Therefore, standing MRI provides more radiologic information correlating with clinical symptoms in LSS patients than supine MRI does.