The ring of C2 and evaluation of the cross-table lateral view of the cervical spine.

The cross-table lateral view is essential in the initial workup of a trauma patient with a suspected cervical-spine injury. The identification of the radiographic "ring" of C2 on the cross-table lateral view is discussed. When a type III odontoid fracture is present, the ring of C2 is disrupted. We propose that "identification of the ring of C2" should be added to the emergency physicians' systematic checklist when clearing a cross-table lateral view of the cervical spine.