Which structure is in contact with the posterior surface of the dens?

Which structure is in contact with the posterior surface of the dens?

• A. Posterior longitudinal ligament
• B. Transverse ligament of the atlas
• C. Alar ligaments
• D. Nuchal ligament

Answer: (B)

The key idea is that the dens (odontoid process) of the axis acts as a pivot within the ring formed by the atlas. The transverse ligament of the atlas completes that ring behind the dens, running between the atlas’s lateral masses and holding the dens against the anterior arch. Because of this arrangement, the posterior surface of the dens sits in contact with the transverse ligament. This close contact is critical for stability; tearing the transverse ligament allows posterior displacement of the dens and can threaten the spinal cord. Other structures don’t share this direct posterior relationship: the alar ligaments run from the dens to the occipital bones, the posterior longitudinal ligament lies along the vertebral canal’s posterior aspect, and the nuchal ligament is a superficial neck structure.

The key idea is that the dens (odontoid process) of the axis acts as a pivot within the ring formed by the atlas. The transverse ligament of the atlas completes that ring behind the dens, running between the atlas’s lateral masses and holding the dens against the anterior arch. Because of this arrangement, the posterior surface of the dens sits in contact with the transverse ligament. This close contact is critical for stability; tearing the transverse ligament allows posterior displacement of the dens and can threaten the spinal cord. Other structures don’t share this direct posterior relationship: the alar ligaments run from the dens to the occipital bones, the posterior longitudinal ligament lies along the vertebral canal’s posterior aspect, and the nuchal ligament is a superficial neck structure.