 In the thoracic and lumbar regions, it presents a series of dentations with intervening concave margins.The posterior longitudinal ligament is narrow at the vertebral bodies, where it covers the basivertebral veins, and widens at the intervertebral disc space.It weakly prevents hyperflexion of the vertebral column and limits spinal disc herniation, although it is much narrower than the anterior longitudinal ligament, such that spinal disc herniations usually occur in a posterolateral direction.