Fig. 13

Facet joint injury spectrum resulting from hyperflexion distraction. Parasagittal CT images. a The C4–C5 facet joint shows diffuse widening—diastasis (black arrow), and the C5–C6 facet joint shows focal anterior widening (white arrow), suggestive of distraction injury and partial disruption of facet joint capsule. Articular surfaces are congruent and no uncovering of the inferior articular process noted at any of the injured levels. b C5–C6 facet joint subluxation (black arrow), suggested by non-congruent articular surfaces of the facet joint with anterosuperior displacement of the inferior articular process of C5, resulting in partial uncovering of the superior articular surface of C6. However, some apposition of articular surface is still intact. C6–C7 facet joint dislocation (white arrow) suggested by anterior and superior translation of inferior articular process of C6 resting on the top of the C7 articular process, resulting in complete loss of articular apposition and uncovering of C7 articular facet. A facet joint injury as seen at C6–C7 is also named as a “perched facet”. c C6–C7 facet joint dislocation with further anterior translation of the inferior articular process (white arrow), now resting anterior to the C7 articular pillar. This injury is also called a “locked” or “jumped facet”