Pediatric emergency medicine trisk 902
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fracture can sometimes be mistaken for the normal or physiologic subluxation that
exists in the C2–C3 or C3–C4 regions in approximately 25% of children younger
than 8 years and may also be seen up to 16 years of age. This radiographic
pseudosubluxation is caused by ligamentous laxity, relatively horizontal facet
joints, weak neck muscles, and cartilage artifact. Distinguishing between a subtle
hangman’s fracture and pseudosubluxation can be accomplished using Swischuk’s
“posterior cervical line,” as described in Figure 112.18 . A value of more than 1.5
to 2 mm suggests an occult hangman’s fracture as the source of the anterior
subluxation of C2 on C3. The increase in magnitude of the distance between the
cortex of the spinous process of C2 and the posterior cervical line in a hangman’s
fracture is the result of anterior displacement of the skull, C1, and the anterior
portion of C2 on the remainder of the lower cervical spine. Nontraumatic
subluxation has also been reported at the C5/C6 and C6/C7 spinal levels, although
subluxation at these lower levels should always be fully investigated for potential
ligamentous injury.
FIGURE 112.24 Hangman’s fracture. A 7-week-old infant with fracture through the posterior
elements of C2 as indicated by the arrow. (Reprinted from Sumchai A, Sternback G. Hangman’s
fracture in a 7-week-old infant. Ann Emerg Med 1991;20:87. Copyright © 1991 American
College of Emergency Physicians. With permission.)
FIGURE 112.25 A: Diagrammatic representation of transverse ligament disruption (left ) and
dens fracture (right ). The arrows indicate the direction of movement that resulted in the noted
injury. B: Widened predental space on initial lateral radiograph in a 15-year-old girl (actual
measurement was 4 mm). C: Flexion radiograph in the same patient demonstrating increased
predental space with evidence of transverse ligament disruption. D: Dens fracture with anterior
subluxation of C1 and the dens on the remainder of the spinal column. Arrow indicates fracture.
