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Ligaments of the vertebrae - ...


Description

The first two cervical vertebrae, the atlas and the axis, and their associated serial homologue, the occipital bone at the base of the skull, form the most mobile of the vertebral joints. These specialized vertebral elements allow for the wide range of motion of the cranium. In conjunction with their specializations and range of motion, a varied array of important ligaments support these boney elements.

Atlanto-occipital joints and ligaments

Often considered to be a hinge joint because of its primary uniaxial range of movement (as in shaking your head “yes”), the atlanto-occipital joints occur between the reciprocally curved surfaces of the two occipital condyles and the articular facets on the lateral masses of the atlas. While the primary axis of movement is the nodding movements of flexion and extension of the head in the anteroposterior plane, a small amount of side to side bending (lateral flexion), and rotation is possible at this joint surface. The primary ligaments of the joint are the fibrous membrane of the joint capsule, the anterior atlanto-occipital membrane, and the posterior atlanto-occipital membrane.

Atlanto-axial joints and ligaments

This is a group of three synovial joints that occur between the first two cervical vertebrae, the atlas and the axis. The altlanto-axial joint complex consists of two somewhat planar lateral joints between the articular facets of the lateral masses of the respective bones, and a median pivot joint where the dens of the axis fits into a fibro-osseous tunnel formed by the anterior arch and transverse ligament of the atlas. The principal motion at this joint is rotational movement in the transverse plane, as if one is shaking their head to say “no.” In addition to the transverse ligament mentioned above, the fibrous capsules of the lateral joints and the alar ligaments, which attach between the dens and the medial aspect of the occipital condyles, are primarily responsible for limiting the rotational movements of the joint.

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