CT patterns of facet fracture dislocations in the thoracolumbar region.

Thoracolumbar facets are not as commonly dislocated as are those of the cervical spine. It is, however, crucial to make an early and accurate diagnosis of thoracolumbar facet dislocation since the injury may be unstable and require reduction and internal fixation. This paper presents three major CT patterns of thoracolumbar facet fracture dislocation. The first represents anterior subluxation of the vertebral body with anteriorly locked facets. The second is a lateral vertebral body subluxation with laterally locked facets. The third is an acute kyphosis with little vertebral body subluxation but superiorly dislocated facets. Since the vertebral body subluxation may be missed on axial CT images, these facet-dislocation patterns should be recognized by identifying the paired superior and inferior facets and establishing their congruency. Identification of the facets is accomplished by their orientation with respect to the vertebral body (superior facets are directed posteromedially and inferior facets are directed anterolaterally) as well as by the shape of the articular surface (superior facet articular surface is concave, inferior facet articular surface is flat or convex).