RELATIONSHIP OF THE DURA, HOFMANN LIGAMENTS, BATSON PLEXUS, AND A FIBROVASCULAR MEMBRANE LYING ON THE POSTERIOR SURFACE OF THE VERTEBRAL BODIES AND ATTACHING TO THE DEEP LAYER OF THE POSTERIOR LONGITUDINAL LIGAMENT - AN ANATOMICAL, RADIOLOGIC, AND CLINICAL-STUDY

With the advent of computed tomography (CT) and magnetic resonance ima ging (MRI), visualization of soft tissue structures in the spinal cana l, which were previously undetectable, is possible. This study was und ertaken to more accurately identify these soft tissue layers and to de termine factors such as when is a disc contained and when is it not; i n discography, when the disc leaks, into what layer is the contrast go ing; or when a nuclear fragment creeps upward or downward, just where is it. The works of Fick, Dommisse, Kikuchi, Schellinger, Hofmann, Bat son, and Parke were studied. The professors of anatomy of four major m edical schools were consulted along with several neuroradiologists and embryologists. Forty lumbar spines were dissected (20 fresh, 20 prese rved). Magnetic resonance imaging scans were taken. Photographs and ph otomicrographs were made. A fibrous membrane, first mentioned by Fick, can be identified lying anterior to the posterior longitudinal ligame nt and attaching to the deep layer of the posterior longitudinal ligam ent. It has been given relatively little attention in the past. This m embrane has about one fourth the toughness of the dura and is made up largely of fibrous tissue. The veins of Batson lie on its dorsal surfa ce and pierce it to go ventral to this membrane and enter the vertebra l body. Batson's plexus crosses the disc space. The peridural membrane extends from one side to the other, spanning the width of the vertebr al body and encircling the bony canal around the outside of the dura. There is a potential space between it and the dura. It does not cross the disc space. A probe can easily be passed posterior or anterior to it, between it and the posterior longitudinal ligament or between it a nd the vertebral body. We also identified Hofmann's ligament anterior to the dura, attaching the dura to the posterior longitudinal ligament . Laterally, tiny attachments between this fibrovascular membrane and the circumneural sheaths of the spinal nerves can be observed as the n erves enter the foramina. The posterior longitudinal ligament (PLL) is very tough and strong and seldom ruptures. The annulus frequently rup tures. Fragments of nucleus pulposus can creep out at the vertebral ri m and get under the PLL and the peridural membrane. Hematoma can form by the same route and have the exact appearance as a sequestrated disc . There is no periosteum inside the vertebral canal. With MRI, hematom as can be differentiated from an extruded fragment, They may cause sym ptoms similar to an extruded disc but will probably heal with time. In fection in the vertebral body may sometimes come posteriorly into the premembranous space but is blocked by the membrane and seldom breaks t hrough into the epidural space. Knowledge of structures in the vertebr al canal adds to our ability to interpret CT scans, MRI scans, and dis cograms. During surgery, one often wonders what tissue layer is being cut when an incision is made into the layers that are overlying a disc fragment that has crept caudally or cranially from its disc level of origin. Often this tissue layer appears far too thin and fragile to be the PLL. We know now that it is probably this fibrous membrane with t he veins of Batson on its posterior surface.