Vertebral Column Injury (specific injuries)

• 
  sudden spinal cord injury in association with os odontoideum after minor trauma have been reported.
  

• 
  most often, there is anterior instability, with os odontoideum translating forward in relation to body of C2.
  
• 
  at times, one will see either no discernible instability or “posterior instability” with os odontoideum moving posteriorly into spinal canal during neck extension.
  
• 
  degree of C1-C2 instability on XR does not correlate with presence of myelopathy; sagittal diameter of spinal canal at C1-C2 level < 13 mm does correlate with myelopathy detected on clinical examination.
  

1. 
   neurological symptoms → C1-2 fusion
   
2. 
   irreducible dorsal* cervicomedullary compression → occipital-cervical fusion ± C1 laminectomy
   
3. 
   associated occipital-atlantal instability → occipital-cervical fusion ± C1 laminectomy
   

N.B. Odontoid screw fixation has no role!

Hangman’s fracture (s. traumatic spondylolysis of C₂)

(unstable - but cord damage is rare because AP diameter of neural canal is greatest at C₂ level and because bilateral pedicular fractures permit spinal canal to decompress itself with forward displacement of C₂ body)

• 
  abrupt deceleration (e.g. hanging with knot in submental position, striking chin on steering wheel in head-on automobile crash) → cervicocranium (skull, atlas, and axis functioning as unit) is thrown into extreme hyperextension → bilateral pedicle fractures of axis (± broken subjacent disc bond → forward subluxation of C₂ on C₃).
  
• 
  cervical spine / spinal cord damage happens in only those hangings that involve fall from distance greater than body height.
  

Potential dislocation:

1. 
   fracture lines extending through pedicles of C₂ (i.e. anterior to inferior articular facets).
   
2. 
   disrupted posterior cervical line (base of C₂ spinous process lies > 2 mm behind posterior cervical line).
   
3. 
   prevertebral swelling (may cause respiratory obstruction!).