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Case 5

Bilateral locked facets

A young man with back pain after a fight

This man presented to the Accident and Emergency Department late one night having become inebriated and picked a fight. He was kicked to the ground and stamped upon by his assailants. He complained of a pain over his back.

On examination there was a large swelling in the region of the thoracolumbar junction. Neurological examination was entirely normal - indeed after the examination he attempted to assault several members of staff and was wrestled to the ground!

Look at the AP and lateral views of his lumbar spine. What abnormalities do you see? What further investigation might you request?

Findings

On the lateral spine there is anterior collapse of the body of T12, with a small anterior bone fragment visible. The body of T11 is displaced anteriorly relative to T12, with a major step in the line of the posterior longitudinal ligament.

On the AP film it is difficult to appreciate the some loss of height of T12. The major observation to make is the increased gap between the spinous processes of T11 and T12, when compared with the rest of the spine. This alone strongly suggests a major flexion injury such as a Chance fracture or facet fracture/dislocation.

On the CT the diagnosis becomes clearer. There is little in the way of fractures (just the small anterior fragment on image 3). However the arrangement of the facet joints is clearly abnormal when compared with the level below (Image 6). The posterior facing facets of T12 are "bare", while those of T11 have moved superiorly by two or three images, and anteriorly. They are now "locked" in front of their counterparts from the vertebra below.

Diagnosis

Facet dislocation at T11/T12, bilateral locked facets.

Discussion

This is a major flexion injury of the spine. Unilateral locked facets, as well recognised in the cervical spine, is considered a stable injury. However bilateral locked facets is unstable as there is nothing to prevent further anterior slip of the upper vertebral body, compromising the cord as it does so.

This patient was taken to theatre where, under anaesthesia and muscle relaxants the injury was reduced relatively easily. The T11/T12 level was fused - the associated ligamentous injury is severe and predisposes to persistent instability at this level. The patient incured no neurological symptoms before or after surgery.

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