Posterior lumbar epidural fat as a functional structure? Histologic specificities.

Abstract

A topographic and histologic study was done to describe the location of the lumbar epidural fat and to find potential tissular specificities. To search for possible histologic characteristics of posterior lumbar epidural fat, which so far has been described as semifluid tissue, and to determine whether posterior lumbar epidural fat is not a simple incidental tissue. The lumbar epidural fat on two fetuses was studied. In adults, subcutaneous fat and posterior lumbar epidural fat were taken from seven corpses. The authors obtained 13 posterior lumbar epidural fat pads (two at L1-L2, three at L2-L3, six at L3-L4, and two at L4-L5) and four subcutaneous fat pads. The authors studied abdominal axial histologic sections in two fetuses, histologic multiplanar sections in seven adults, and semithin sections in four adults of posterior lumbar epidural fat and subcutaneous fat. Fetal distribution of epidural fat was circumferential. Adult epidural fat distribution was limited to the posterior part of the vertebral canal and located at the disc level. Fascicles of connective tissue were less numerous and thinner in posterior lumbar epidural fat than in subcutaneous fat. Organized sliding spaces were found in the posterior epidural fat ped. Posterior lumbar epidural fat is not a simple incidental tissue and shows specific histologic features: sliding spaces and rarefaction of connective tissue that could explain semifluid features of the tissue. These characteristics suggest a functional role of posterior epidural fat in the lumbar spinal unit.