Describe the two types of locked facet injuries.

Unilateral: Rotation injury of the upper cervical vertebrae resulting in rupture of the apophyseal joint ligaments and facet joint dislocation; the facet joint may lock in an overriding position.

Bilateral: Injury resulting from extreme hyperflexion and leading to complete anterior dislocation of the vertebral body; it is associated with a very high risk of cord damage.