Case 8 - "Locked Facets" (Cervical Spine Facet Joint Dislocation)

This case demonstrates bilateral cervical spine facet joint dislocation, which is commonly called jumped or locked facets.  Facet joint subluxation, perched facets, or locked facets all fall under the hyperflexion type of injury and can be unilateral or bilateral. When there is true facet joint dislocation, as was present in this case, you also have a translational injury as noted by the anterolisthesis of C6 on C7. In the setting of cervical spine trauma, a lot of trauma centers are performing a CTA of the neck as their initial cervical spine evaluation in order to asses for bony injury and associated vascular injury. If not performed, this patient would require a CTA of the neck as well.

When evaluating the cervical spine in the setting of trauma, I always start with the sagittal series because I want to be most attuned to looking for facet joint alignment and widening of the posterior elements of the spine, which is often quite subtle, more so than perched or locked facets. Facets are considered subluxed when there is less than 50% overlap of the articular surfaces or there is more than 2mm of diastasis.

Normal facet articulation on the axial images - the facet look like a hamburger  with two 'bony buns'

Reverse Hamburger Bun Sign - the facets are dislocated

Locked Facets - The red lines show where the superior and inferior facets should be articulating.

The arrows show the areas of bony avulsion from the vertebral body, which was ripped of by the anterior and longitudinal ligaments.

For further reading, this is a great radiographics article, which further describes cervical spine trauma and also delves into the SLIC morphology score for surgical vs. nonsurgical management.

MDCT of Blunt Cervical Spine Trauma in Adults (Dreizin, et al)