Radiographic signs of unilateral dislocation include:
- Anterior displacement of the superior vertebral body at the affected level less than 50% of the AP diameter of the inferior vertebral body.
- Malalignment of the spinous processes on AP view.
- The facets of the dislocated rotated superior vertebrae appear adjacent to one another rather than in profile, giving rise to a 'bow -tie' deorfmity.
Bilateral facet dislocations appear as both superior facets lying anterior to the inferior facets, with anterior displacement of the superior vertebral body greater than 50% of the AP diameter of the inferior vertebral body.
Diagnosis can also be made by CT scan.