Alar ligament

Ligaments of the upper cervical spine

The alar ligaments are important structures in the upper cervical spine that play a crucial role in stabilizing the head and neck. These ligaments are paired and connect the sides of the dens (odontoid process) of the axis (C2 vertebra) to the medial sides of the occipital condyles of the occipital bone.

Anatomy

The alar ligaments are strong, fibrous bands that are approximately 10 mm in length and 3 mm in diameter. They are located on either side of the dens and extend laterally and slightly upward to attach to the occipital condyles. The ligaments are covered by the tectorial membrane and are situated anterior to the cruciate ligament of the atlas.

Function

The primary function of the alar ligaments is to limit the rotation of the head and atlas on the axis. They prevent excessive rotation and lateral flexion, thereby stabilizing the atlanto-axial joint. This stabilization is crucial for maintaining the integrity of the cervical spine and protecting the spinal cord from injury during head movements.

Clinical significance

Injuries to the alar ligaments can occur due to trauma, such as whiplash injuries in motor vehicle accidents. Damage to these ligaments can lead to instability of the atlanto-axial joint, resulting in pain, reduced range of motion, and in severe cases, neurological deficits due to spinal cord compression. Diagnosis of alar ligament injuries often involves imaging techniques such as MRI or CT scan.

Related structures

The alar ligaments are closely associated with several other important structures in the cervical spine, including:

• The transverse ligament of the atlas, which stabilizes the dens against the anterior arch of the atlas.
• The apical ligament of the dens, which extends from the tip of the dens to the anterior margin of the foramen magnum.
• The tectorial membrane, which is a continuation of the posterior longitudinal ligament and covers the alar ligaments.

Gallery

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  Alar ligaments shown in relation to the atlas and axis.

Related pages

• Cervical vertebrae
• Atlanto-axial joint
• Spinal cord
• Whiplash (medicine)