Pediatric emergency medicine trisk 3610 3610

atlantooccipital and C1–C2 interspinous distances The atlantooccipital distance should not exceed mm The C1–C2 interspinous distance should not exceed 10 mm Sun’s ratio, C1–C2:C2–C3, >2.5 suggests potential ligamentous instability Sun’s ratio, as well as a ratio of measurements of the basion to the posterior arch of C1 (BC) and the opisthion to the anterior arch of C1 (OA), is demonstrated in Figures 112.27 and 112.28 If the BC:OA ratio is more than one, it signifies atlantooccipital dislocation, an often fatal injury Neurologic deficits may develop from direct spinal damage or associated carotid or vertebral artery injury Distraction injuries may also be seen with difficult newborn deliveries These injuries may not be visible on a plain radiograph because the pediatric cervical spine can transiently distract in before residual radiographic evidence of spinal column separation is present However, the spinal cord can distract only 0.25 in before permanent neurologic damage occurs A CT scan should be obtained in patients with potential atlantooccipital dislocation An MRI scan is useful in evaluating an infant with diminished motor activity and who is suspected of having a distraction injury FIGURE 112.26 A cross section through the ring of C1 demonstrates Steele’s rule of three The space between the cervical cord and dens allows limited movement between C1 and C2 without immediate neurologic compromise