AOD

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FACTS

Internal decapitation 2/2 ligamentous injuries. Patients can present intact (20%), paralyzed, or dead.
  • more common in pediatrics (higher head to body ratio, less cupped condyles, increased ligamentous laxity)
  • tectorial membranes and alar ligaments primarily responsible for resisting distraction between O and C1
  • extremely unstable injury, these patients frequently deteriorate if they even make it to the hospital
  • Clinical manifestations can range from intact to paralyzed to dead
    • minimal deficits
    • cruciate paralysis / bulbar cervical dissociation (immediate pulmonary/cardiac arrest)
    • can be fatal (respiratory arrest from bulbar-cervical dissociation due to SCI at or above C3)
  • often associated with severe TBI

Traynelis classification of AOD

1 - forward (anterior)
2 - up (longitudinal)
3 - backward (posterior)
notion image

HPI

universal ROS

PHYSICAL EXAM

  • universal exam
  • detailed spine exam + lower cranial nerves

IMAGING

obtain CT C-spine, XR Cervical
Measure in all patients: BAI/BDI, ADI, Condylar gap (CCI=AOI), Powers ratio
Measure in peds: C2 pre-vertebral soft tissue, lateral mass interval

Condylar gap (C-C1 interval) = Atlanto-occipital interval (AOI)

  • modality: CT
  • definition: distance between occipital condyle and superior articulating facet
  • measure on sagittal and coronal
  • best diagnostic sensitivity and specificity for AOD
  • Pang: av

Atlantodental

BAI (Type 1/3)

  • modality: lateral XR
  • definition: distance from basion to line drawn along posterior wall of C2 VB (posterior axial line)
  • best to diagnose with lateral plain XR, but these measurements can be used for CT as well.
  • Adults: normal -4 to +12mm
    • >12mm: Type I / Type II
    • -4mm or less: Type III
  • Pediatrics: normal 0-12mm (should never be negative)

BDI (Type 2)

  • modality: lateral XR
  • definition: distance from basion to dens
  • better for adults (unreliable < 13 yr b/c variable age of ossification/fusion of ondontoid os)
  • Adults: normal < 8.5mm
  • Peds: normal < 10.5 mm (95% ile)
    • with os < 9.5 mm
    • without os < 11.5 mm

Powers ratio (BC/AO)

A/P

  • All patients need an occipital-cervical fusion
  • Halo is not adequate
  • Traction is contraindicated