MIDLINE SAGITTAL VIEW OF THE LUMBAR SPINE The posterior epidural space (shown in orange) is segmented by areas where the dura contacts bone. The posterior epidural space compartments have their greatest anteroposterior dimension at their superior end. The anterior dura is fused with the posterior longitudinal ligament and the annular ligament at the level of each intervertebral disc, which divide the anterior epidural space into vertical segments. The posterior longitudinal ligament separates from the anterior dura at the lumbosacral junction and the anterior epidural space becomes filled with fat more inferiorly.