The diagnosis or exclusion of fractures of the axis (C2) poses particular problems. The anatomy is complex, resulting in a myriad of overlapping structures on radiographs. Furthermore, fractures of the axis are minimally displaced and, therefore, difficult to identify with certainty. Over half (55%) involve the odontoid, 25% are hangman's fractures, and the remainder include miscellaneous fractures of the body, neural arch, and spinous process.Approximately 1.5% of fractures of the cervical spine involve C2, of which 40% are associated with head injuries and 20% with other fractures of the spine. The most common combination is a fracture of the axis associated with a second, fracture of the atlas: for instance, a hangman's fractiire of C2 with a fracture of the neural arch of C1 (see Figure 3). However, associated fractures and fracture dislocation of the lower cervical spine and cervi-cothoracic, junction are not unusual, occurring in approximately 8%. Thus, when a, fracture Of C1 or C2 is identified, one is still obligated to see all seven cervical vertebrae. Less commonly, the second injury is located in the mid-thoracic spine or thoracolumbar junction.Injuries of the craniovertebral junction infrequently result in spinal cord injury at this level. When a neurologic deficit is encounted and a fracture of C1 or C2 is identified, it is qiiite likely that a second, lower level injury accounts for the deficit. Under these circumstances, the entire spine should be examined in the anteroposterior and lateral projections to exclude injury at a lower level.
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