Cruciate ligament of the atlas
The cruciate ligament of the atlas (also known as the cruciform ligament) is an important ligamentous complex that holds the posterior dens of C2 in articulation at the median atlantoaxial joint. It lies behind a large synovial bursa (surrounded by loose fibrous capsule) and consists of two bands:
- longitudinal band: attaches the body of the C2 (axis) to the clivus and foramen magnum in the midline, lying between the apical ligament and tectorial membrane. It is relatively weak and hence does not contribute any significant stability.
- transverse band (also known as the transverse atlantic ligament): attaches to a small tubercle on the medial cortex of the C1 (atlas) lateral masses on both sides anterior to the tectorial membrane and dura. It passes posterior to the dens, with a small intervening synovial capsule, fixing the dens to the posterior margin of the anterior arch of the atlas. It is the strongest ligament in the whole spine and arguably the most important!