Anatomy, Back, Posterior Longitudinal Ligament

The posterior longitudinal ligament is one of the three more important ligaments that contribute to stability in the spine. This ligament passes along the posterior aspect of the vertebral body inside the vertebral canal from the body of the axis to the sacrum. The ligament is composed of longitudinal fibers that are denser than the anterior longitudinal ligament. However, like the anterior longitudinal ligament, the denser fibers are deeper and span one vertebra, while the superficial fibers span three to four. The superficial layer is a continuation of the tectorial membrane at the axis, and the deep layer is a continuation of the cruciform ligament at the atlas.  The fibers are wider at the intervertebral spaces and are more adherent to the annulus fibrosus of the intervertebral discs than at the vertebral body, where they are thinner. This phenomenon is more visible in the posterior ligament than in the anterior. Therefore, the posterior longitudinal ligament is much thinner than the anterior longitudinal ligament, which is significant for the pathophysiology of disc herniations occurring posterolaterally.