Alar ligaments

Study entry

Classification

Ligaments of the atlantoaxial joint.

Surfaces

They run from the sides of the dens of the axis to the lateral margins of the foramen magnum.

Capsule

Short, rounded cords about 0.5 cm in diameter. They join the skull to the upper cervical spine.

Movements

They act as check ligaments of the head. [CHECK: the OCR cuts off the sentence; usually described as limiting rotation]

Blood supply

Spinal branches of the segmental arteries of the level, which supply the bones, the periosteum, the ligaments and the meninges around the epidural space: in the neck, from the vertebral and ascending cervical arteries; in the thorax, from the posterior intercostals; in the abdomen, from the subcostal and lumbar arteries; in the pelvis, from the iliolumbar and the lateral and median sacral arteries.

Innervation

Meningeal (recurrent) branches of the spinal nerves. They arise just after the nerve forms, return through the intervertebral foramen and supply the periosteum, the ligaments (especially the anterior longitudinal), the meninges and the annuli fibrosi of the discs. They carry pain from these structures.

Clinical

They are weaker than the transverse ligament of the atlas and can rupture in craniovertebral injury.

Source: cap. 2, «Articulaciones craneovertebrales»; fig. 2-20 A; «Vascularización de la columna vertebral» e «Nervios de la columna vertebral»

Other structures in this region

• Ligamenta flava
• Cruciate ligament of the atlas (transverse ligament and longitudinal bands)
• Tectorial membrane
• Anterior and posterior atlanto-occipital membranes
• Lumbosacral joints
• Joints of the vertebral bodies (intervertebral discs)
• Zygapophysial (facet) joints
• Uncovertebral joints (of Luschka)