The Anatomy of the Lumbar Epidural Space using Magnetic Resonance Imaging

MRI(Magnetic Resonance Imaging) have provided for greater image resolution, detailed tissue contrast without use of contrast media and images acquired in any plane. The purpose of this study was to examine the anatomy and dimension of the epidural space using MRI(Magnetic Resonance Imaging) and to compare the information obtained with that from other investigative technique. The anatomy of the lumbar epidural space was studied retrospectively using lumbar MRI scans of 90 patients. The epidural width(E.W.) is divided into three distance between the anterior surface of the ligamentum flavum and the dura at the caudal end of the lumbar segment(A), at the mid point of the ligamentum flavum(B) and at the cranial end of the lumbar segment(C). The distance from skin to supraspinous ligament(S-L) and from supraspinous ligament to epidural space(L-E) were measured. And then with adding both the distance, We measured the distance from skin to epidural space(S-E). Results were as follows; I) Posterior to the dural sac, epidural fat which is of high signal(white) on Tlw(T1 weighted) image is demonstrated at levels Tl I-T12 to L5-Sl giving 'Saw toothed' pattem to the epidural space. The fat is divided into segments by the interposing laminar, and the epidural space is deeper at cranial end than caudal end. 2) It was the relatively wide epidural space in L2-3 and L3-4 level, and the narrowest epidural space in L5-Sl level. 3) The distance from skin to supraspinous ligament was noted marked variation(2-40mm) according to the individual disparity. And the distance from supraspinous ligament to epidural space is 17-43mm. In distance from skin to epidural space, the most narrow place is Ll-21evel (37.95±7.65mm). The most deep place is IA-5 level(46.35±7.20mm). As the age increase, epidural width is decreased at L3-4 level (p<0.05).(Korean J Anesthesion 1995; 29: 539~545)