Chapter V-2. Type III Odontoid Fracture—the "Ring of C2"

A 41-year-old man was brought to the ED following a motor vehicle collision in which he was an unrestrained driver whose vehicle hit a roadway median divider. The automobile driver’s air bag deployed. At the scene, the patient was confused and “oriented times two.” Upon his arrival in the ED, his mental status was normal and he admitted to having had “a few beers.” He complained of lower back and neck pain.

The patient was hemodynamically stable. The only evident trauma was a left parietal scalp laceration and hematoma. His neurological examination was normal.

The chest and pelvis radiographs were negative for an acute injury. The cervical spine radiographs are shown in Figure 1.

• Are there any abnormalities?

Note: Loss of anterior vertebral body height at C4 is not an acute fracture. However, there is a second finding that represents an unstable cervical spine injury.

(Arrow = windshield glass lying next to the patient’s scalp.)

See patient outcome.

Lateral View—ABCS Approach

All seven vertebrae are visible (Figure 2). The patient’s position is slightly rotated, as evident by the lack of perfect overlap of the left and right articular facets at each vertebra.

The overall alignment of the vertebral bodies and spinolaminar line appears normal. The intervertebral disk spaces and the spaces between the spinous processes are uniform.

The prevertebral soft tissues are less than 5 mm at C1, C2, and C3. However, close examination of the contour of the prevertebral soft tissue reveals a slight focal convexity (bulge) anterior to the base of the dens (white arrowhead).

Examination of the bones of the lower cervical spine reveals narrowing of the anterior aspect of the C4 vertebral body (arrow,Figure 2). However, based on the radiographic findings and subsequent evaluation with CT and flexion/extension views, this represents an old injury rather than an acute fracture.

When examining the bones of the cervicocranium, several radiographic landmarks should be noted. These include the predental space, the posterior arch of C1, the dens, the C2 vertebral body, and the posterior arch of C2 (Figure 3).

A distinctive radiographic landmark overlies the body of C2—the “ring of C2” (Figures 3 and 4). This oblong-shaped ring is formed by cortical bone projecting ...