Answer: Unilateral Facet Dislocation

Normal L & R superior articular facets overlap/aligned to the C6-C7 where 1 is shifted anterior(red dash)

-Ant & post vertebral lines (green) ?ok

-Spinolaminar line (orange)=broken

-Poseriort spinous line (purple) = gap

Perched facet = subluxed joint with tip of inferior facet resting on tip of super facet of lower body

Dislocated/jumped/locked facet = complete dislocation with inferior tip ANTERIOR to superior facet of lower body (thus “locked”)

Get the CT and ALWAYS look for the fracture!

Unilateral jumped facets can be tough on X-ray as the vert body doesn’t have to displace much (vert lines ok).

ALWAYS look at spinolaminar & posterior spinous lines!

Facets = “shingles on a roof"

Any abrupt change/rotation should be concerning!

For completeness, here is a bilateral facet dislocation.

ALL spinal lines disrupted. No rotation. Both inferior facets jumped and locked anterior to the superior facets of the lower body.

- MRI=diffuse ligamentous injury

- neurologically devastating