Radiology #4: Flexion-distraction
- nicholaschapmannz
- Jun 16
- 2 min read
Updated: Jun 16
The Patient
A 55 year old man is brought in by EMS following a high-speed motor vehicle crash. He was the restrained driver of one of the two involved vehicles. He is not able to provide any history, as his GCS on arrival is 8, and you intubate him prior to CT.
The Pictures
What do you think?
click to reveal the answer
That's right - there's a C6/7 unilateral facet joint dislocation.
These are the most commonly missed cervical spine injury on plain film x-ray [1] - which thankfully is fast becoming a rare choice of imaging modality for the assessment of cervical spine injury.
There are a few features visible that are consistent with a unifacet dislocation.
First and foremost is the anterolisthesis of C6 on C7. If you look at the left hand image below, you can very clearly see that there is disruption of both the anterior and posterior vertebral lines (shown in red). If you were to guess what proportion of C6 overhangs the top of C7, you'd probably say about 25%. This is consistent with a unilateral facet dislocation. A bilateral facet dislocation on the other hand is usually >50% displaced.
Secondly, you can see on the right hand image that the inferior articular facet of C6 has slipped up and over the superior articular facet of C7 below it (shown by the red arrow). Here it is "locked" in position. Compare this with the facet joints above it, where the alignment is correct.
These injuries are typically stable if there is no associated fracture, but about 30% are associated with neurological deficit (often due to radiculopathy rather than spinal cord injury). They can also be associated with disc herniation causing spinal stenosis or cord contusion/haematoma however. Identification is important because with prompt reduction neurological outcomes are usually good.
Thanks to Dr Nick Chapman for submitting this case.
References
click to see references
[1] Leong N, Lim E, Ho CL. Radiological signs in traumatic cervical facet joint dislocations. J Belg Soc Radiol. 2021;105(1):8.
[2] Shapiro SA. Management of unilateral locked facet of the cervical spine. Neurosurgery. 1993;33(5):832-7.
