A single fracture in the atlas ring: report of two cases and a review of the literature.

Atlas fractures commonly present more than two breaks in its ring structure because of the unique anatomy and the mechanism of injury. The incidence of a single break in the atlas ring is exceedingly rare. However, we encountered two cases of a single fracture of the atlas. One patient was struck by a falling tree on the right side of the head and the other was involved in a motor vehicle accident. Radiographs of the cervical spine failed to show a single fracture or other abnormalities. Computed tomography demonstrated the single fracture. The patients were treated conservatively with a cervical collar, and they both recovered completely. In this article, we present two cases of a single fracture of the atlas with a review of the literature.