[Posterior epidural adipose tissue and the narrow lumbar canal: replacement tissue or cause of impingement?].

The role played by the epidural fat has been reported in lipomatosis induced by exogenous glucocorticoids and in severe obesity with lipomatosis. The role played by the "normal" posterior epidural fat (PEF) in lumbar canal stenosis (LCS) is less well known. The purpose of this study was to determine the part taken by PEF in LCS patients without endocrine disease, corticosteroid therapy or obesity. For this, we tried to specify the amount and distribution of PEF among the soft tissues in the vertebral canal, to demonstrate the involvement of PEF in dural sac compression, to describe the radiological features observed in cases of LCS and to look for associated morphological factors. The records of 30 LCS patients without exogenous or endogenous lipomatosis and in whom the essential pathogenic factor in 40 levels was PEF were reviewed retrospectively. At disc level, PEF was evaluated in the lower part of the mobile segment by means of CT or MRI axial sections cut through one or two spaces between L2-L3 and L4-L5. Measurements were made in 25 men (80%) and 6 women (20%) aged from 33 to 83 years (mean: 58 years). Most patients were suffering from lumbar pain, radiculopathy and/or neurogenic intermittent claudication. The data measured were: antero-posterior (AP) diameter of the dural sac, AP diameter of the bony lumbar canal (BLC), interligamentous distance (ILD) opposite the articular facets, and surface of PEF. The soft elements present on the midline--anterior epidural space (AES) and posterior epidural (PEF)--were expressed as percentage of the AP diameter of the bony lumbar canal.(ABSTRACT TRUNCATED AT 250 WORDS)