perched facet joint
Perched facet joint is a vertebral facet joint whose inferior articular process appears to sit 'perched' on the ipsilateral superior articular process of the vertebra below.
Any further anterior subluxation will result in dislocation, with one facet "jumping" over the other and becoming locked in this position (see jumped facet joint).
Pathology
Unilateral perched facet results from flexion-rotation force. Perched bilateral facets are also possible.
Radiographic features
Plain radiograph
- malalignment of the lateral masses
- the tips of adjacent facets touch each other i.e. inferior articular process of a vertebra appears to sit 'perched' on the superior articular process of the vertebra below
CT
- distracted facet with uncovering of the articular surface
Complications
- spinal cord injury, especially with bilateral involvement, or in the setting of canal stenosis
- vertebral artery injury, e.g. dissection, thrombosis
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