[Distension of the inter-facet joints in MRI: and indirect sign of an existing underestimation of spondylolisthesis and canal stenosis].

The authors present two observations of degenerative spondylolisthesis causing canal stenosis in which the stenosis was not apparent on MRI examination, due to reduction of spondylolisthesis in the supine position. In these cases, MR images of the facet joints showed unusual large areas with hypersignal on T2 weighted images suggestive of fluid collection. Observation of such images on supine MRI images should raise the suspicion of a spondylolisthesis existing on standing examination but reduced by the supine position, possibly leading to underestimating the canal stenosis.