A 7-year-old German Shorthaired Pointer dog was referred following a road traffic accident with neck pain. CT study of the spine revealed axial and rotational malalignment between C7 and T1 secondary to the left cranial articular process of T1 (arrowhead on images below) being wedged dorsal to the caudal articular process of C7 (arrow on images below). A small bone fragment was located dorsal to the luxated cranial articular facet joint surface of T1. In addition, soft tissue attenuating material was present ventrolateral on the left side at cranial T1 causing mild extradural cord compression (not shown on the images below).

This type of facet injury is very important to identify on imaging in terms of surgical management as any attempt to try to reduce the luxation ventrally in view of spinal fixation would fail due to the locked facet. The parasagittal views are particularly useful to identify locked facet joints (as shown across) where the caudal articular facet of C7 (arrow) slips under the cranial articular facet of T1 (arrowhead) on the bottom right image (normal position shown on the bottom left image).

This dog was managed via a dorsal approach to perform left-sided C7/T1 facetectomy to allow retrieval of extradural material on that side (disc material) and 'unlock' the facet as well as perform a reduction of the luxation by placing a transarticular screw in the C7/T1 facets on the right side; this was followed by a ventral approach to place a plate on the ventral surface of C7 and T1. Recovery was uneventful.
 

For further reading on this rare type of cervical spinal injury:

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Remember to check the facet position next time you have a cervical subluxation!

Courtesy of Dr Andrew ​Levien, surgery specialist and co-founder of Veterinary Specialists of Sydney (VSOS), Australia.