This study reports on postoperative changes of intra and epidural space of both degenerative lumbar spinal canal stenosis(DLSCS) and degenerative spondylolisthesis(DO)on MRI. 48cases(DLSCS:20cases, DO:28cases)were investigated in this study. All cases performed bilateral wide fenestration.

The average age of these patients was 65 years and average follow-up period was 60 months. The average improvement ratio(%) of JOA score was 68% at the last follow-up. Symptomes had deteriorated in 8 cases, according to an increase in the volume of the postlaminectomy membrane, at the last follow-up. There were 8 cases(29%)in DO. showing an increase of % slip on X-ray at the last follow-up, accompanied with both a slight decreasing of the cross-sectional area(CSA)of dural sac and a slight deterioration of clinical results.

Discussion: Symptomes in around 17% of the cases deteriorated, and there were three factors on MRI ; a poor expansion of the dural sac, a grouping of the cauda equina, and a decrease in the CSA of the dural sac.