Which ligament prevents anterior translation of the atlas on the axis?

• A. An anterior longitudinal ligament
• B. Transverse ligament of the atlas
• C. Ligamentum flavum
• D. Posterior longitudinal ligament

Answer: (B)

At the atlantoaxial joint, keeping the atlas from sliding forward over the axis is crucial, and the key structure doing this is the transverse ligament of the atlas. This strong band runs behind the dens (odontoid process) and attaches to the inner sides of the atlas’s lateral masses, effectively holding the dens against the anterior arch of the atlas. By securing the dens in place, it forms a protective ring that prevents anterior translation of the atlas on the axis during movement. Without this ligament, the atlas could move forward relative to the axis, risking spinal cord compression.

Other ligaments have broader roles in spinal stability but don’t specifically prevent anterior translation of the atlas on the axis: the anterior longitudinal ligament runs along the front of the vertebral bodies and primarily limits hyperextension and overall anterior displacement; the posterior longitudinal ligament and ligamentum flavum contribute to stability within the canal and in controlling flexion, but they aren’t the primary restraint against atlas slipping forward.