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AOD

Last modified by Hussein Abdallah on 2025/05/26 03:25

 

NOTE: pediatric AOD is described separately here: https://pittnsgy.myxwiki.org/xwiki/bin/view/Consults/Pediatric/AOD

FACTS

Internal decapitation 2/2 ligamentous injuries. Patients can present intact (20%), paralyzed, or dead.  

  • more common in peds (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

Traynelis classification

1 - forward 

2 - up 

3 - backward 

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CONSULT

HPI 

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) 

FOCUSED EXAM

spine exam

look for lower cranial nerve deficits as well  

IMG 

obtain CT C-spine, XR Cervical 

All patients: BAI/BDI, ADI, Condylar gap (CCI=AOI), Powers ratio

Peds: C2 prevertebral soft tissue, lateral mass interval 

BAI / BDI 

1745437001172-148.png

Condylar gap (CCI) = AOI 

1745437020944-669.png

Powers ratio (BC/AO)

1745437064480-366.png

A/P

 [ ] Type 1 and 3 (forward and backward dislocation) Treated with longitudinal traction + surgery

Normal cranio-cervical measurements

 XRCT
 AdultsPediatricsAdultsPediatrics
BAI-4 mm <= BAI <= 12 mm 0-12 mm (should never be negative)same as XR, but less reliable 
BDI< 12mm unreliable (ossification of odontoid tip) < 8.5mm< 10.5 mm 

AOI = CCI

(Condylar gap)

<= 2mm<= 5mm< 1.4mm (95%ile)< 2.5 mm (single measure) or < 4.0 (average 8 measurements in 2 planes) 
Powers ratio (BC/AO)< 1< 0.9 < 1 < 0.9 
X-line
(occipital axial lines method) 		    
Lateral mass interval