Pediatric emergency medicine trisk 3609 3609

Abnormal posterior cervical line is also shown E: Dens fracture (arrow ) with anterior subluxation of the dens on the body of C2 (A : Reprinted with permission from Swischuk L Emergency Radiology of the Acutely Ill or Injured Child 2nd ed Baltimore, MD: Williams & Wilkins; 1986:572.) Atlantoaxial Subluxation Atlantoaxial (AA) subluxation is a result of movement between C1 and C2 secondary to transverse ligament rupture or a fractured dens ( Fig 112.25 ) Ligament instability may be precipitated by tonsillitis, cervical adenitis, pharyngitis, arthritis, or connective tissue disorders Approximately 15% of patients with Down syndrome have radiographically demonstrated AA subluxation and therefore should be discouraged from contact sports The presence or absence of AA subluxation in patients with Down syndrome, once believed to be a static phenomenon, may actually be transient and/or progressive This ligament instability may progress to ligament rupture with minor trauma Subluxation caused by a transverse ligament disruption is evidenced by a widened predental (periodontoid, atlantodental interval) space on a lateral radiograph ( Fig 112.25 ) Rotary subluxation can be classified as follows: type I (no displacement of C1), type II (3 to mm C1 on C2 anterior displacement), type III (more than mm C1 on C2 anterior displacement), and type IV (posterior displacement of C1 on C2) Normal predental measurement in children is less than mm compared with less than mm in adults This space is wider in children than in adults for the same reasons as described for pseudosubluxation Steele’s rule of three states that the area within the ring of C1 consists of one-third odontoid, one-third spinal cord, and one-third connective tissue ( Fig 112.26 ) Therefore, limited space is available for dens movement or predental space widening without neurologic compromise Neurologic symptoms are often not seen until the predental space exceeds to 10 mm A dens fracture is the cause of AA subluxation more often than ligamentous disruption in a young child because the weakest part of the musculoskeletal system in a child is the osseous component ( Fig 112.25 ) Neurologic damage can occur from direct spinal cord injury or secondarily from vertebral artery damage Cervical Distraction Injuries Cervical distraction injuries may result from rapid acceleration- or decelerationtype incidents, such as high-speed motor vehicle collisions, pedestrian accidents or infant abusive head trauma ( Fig 112.27 ) This type of injury, although uncommon, is reported to be approximately 2.5 times more common in children than in adults Cervical distraction injuries may be obvious or subtle on the initial lateral radiograph Measurements for potential distraction injuries include the