Extract
Throughout the spine, the vertebral bodies are separated from one another
by intervertebral discs. The intervertebral discs provide strength between
adjacent segments and limit movement by resisting compressive, rotational, and
shear forces placed on the spine. In contrast, the highly mobile
occipitocervical (atlanto-occipital and atlantoaxial) joints are synovial
joints whose articulations are devoid of an intervertebral disc; instead, they
are supported by capsuloligamentous attachments. This region is the most
mobile portion of the cervical spine, with nearly one-half of cervical
flexion-extension and cervical rotation occurring across these cartilaginous
articulations. However, the anatomical structures that allow this increased
mobility also predispose the joints to instability.