Pediatric emergency medicine trisk 3612 3612

FIGURE 112.28 Examples of methods to assess occipital/C1 relationships A, C1 anterior arch; B, basion (anterior margin of foramen magnum); C, anterior portion of the posterior ring of C1; O, opisthion (posterior margin of foramen magnum); and D, tip of the dens (odontoid process) These landmarks may not be easily visible on all radiographs A BC:AO ratio of more than 0.9 to 1.0 suggests anterior dislocation or subluxation of the atlantooccipital joint A BD distance of more than 10 to 12.5 mm should be suggestive of atlantooccipital dislocation A C1–C2:C2–C3 ratio of more than 2.5 suggests injury to the tectorial membrane and ligamentous instability