gms | German Medical Science

Objective: Mono- and multisegmental congenital and acquired fusions of the dorsal facet joint structures are common incidental findings on CT imaging of the cervical spine. Our study analyzed differences in injury pattern of the upper cervical spine between patients with and without dorsal fusion.

Methods: 342 patients with injuries of the upper cervical spine from the period 2004-2020 were retrospectively examined and spinal CT, MRI and X-ray function images were evaluated. We paid special attention to differences in injury pattern with regard to the presence of traumatic spondylolysis C2 and odontoid fractures according to the classification by Anderson D'Alonzo.

Results: Dorsal fusion of cervical segments was found in 82 patients (24%). Among these, in 46 cases at least the C2/C3 segment was involved (unilateral n=24, bilateral n=22). In this subgroup, odontoid fractures were the predominant injury pattern in 43 patients (93%; type II n=35, type III n=8). Traumatic spondylolysis C2 was present in 8 patients (17%, unilateral n=3, bilateral n=5). Taking into account common intersections, traumatic spondylolysis C2 (unilateral n=3, bilateral n=1) was found in four patients suffering from odontoid fractures (type II n=1, type III n=3). In the subgroup without dorsal fusion C2/C3 (n=296), 200 patients (68%, Fisher’s exact test p=0.002; type II n=142, type III n=56) harbored odontoid fractures and 60 patients (20%) traumatic spondylolysis C2 (20%, unilateral n=16, bilateral n=44).

Conclusion: Fusion of dorsal cervical facet joint structures is a common phenomenon and highly variable. Especially fusion of the key segment C2/C3 is accompanied by a high rate of odontoid fractures, preferably due to an altered biomechanical stress on this segment.