The posterior ligamentous complex is injured in facet dislocations. The affected superior facet displaces into the neural foramen, frequently (73%) causing radiculopathy. About half have associated facet fractures.
Facet dislocations are either unilateral or bilateral:
- Unilateral facet dislocations are considered stable despite the ligamentous injury because the dislocated facet is 'locked'. About 12% still have associated spinal cord injury.
- Bilateral dislocations also involve injury to the anterior longitudinal ligament. These are unstable, and approximately 87% have associated spinal cord injury.