Gray:The alar ligaments

From Head-neck-joints instability conditions

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The Alar Ligaments

Easy to understand illustration

The alar ligaments connect the sides of the dens (on the axis, or the second cervical vertebra) to tubercles on the medial side of the occipital condyle. They are short, tough, fibrous cords that attach the skull to C1 vertebra and function to check side-to-side movements of the head when it is turned.

The alar ligament is also known as the "check ligament of the odontoid."

The Alar Ligaments (ligamenta alaria; odontoid ligaments) (Fig.: Membrana tectoria, transverse, and alar ligaments)

The alar ligaments are strong, rounded cords, which arise one on either side of the upper part of the odontoid process, and, passing obliquely upward and lateralward, are inserted into the rough depressions on the medial sides of the condyles of the occipital bone. In the triangular interval between these ligaments is another fibrous cord, the apical odontoid ligament, which extends from the tip of the odontoid process to the anterior margin of the foramen magnum, being intimately blended with the deep portion of the anterior atlantoöccipital membrane and superior crus of the transverse ligament of the atlas. It is regarded as a rudimentary intervertebral fibrocartilage, and in it traces of the notochord may persist. The alar ligaments limit rotation of the cranium and therefore receive the name of check ligaments.

(Fig.: Median sagittal section through the occipital bone and first three cervical vertebræ )

In addition to the ligaments which unite the atlas and axis to the skull, the ligamentum nuchæ (Grey Anatomy, page 290) must be regarded as one of the ligaments connecting the vertebral column with the cranium.