The topographical anatomy of the lumbar epidural space.

Although clinically important, the lumbar epidural space is inconsistently described in textbooks of both anatomy and anaesthetics. This anatomical study of twelve cadavers was performed in an attempt to clarify the description of this region. The dura mater, which possesses a midline fold in a very few cases, is apposed to the walls of the vertebral canal, and attached to them by connective tissue, which is sufficient to allow for displacement of the dural sac during movement of the spine and venous engorgement. Between the dura mater and the vertebral canal is a thin layer of areolar tissue. This contains the internal vertebral venous plexus and a posterior deposit of fat which lies in a recess between the ligamenta flava. These findings are discussed in relation to previous studies in an attempt to arrive at a cohesive description of the epidural region.