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Odontoid fracture

The odontoid process fracture (also known as the PEG or dens fracture) occurs where there is a fracture through the odontoid process of C2.

The commonest classification of these fractures is the Anderson/D'Alonzo classification:

  • type I: fracture of the upper part of the odontoid peg; it's rare and potentially unstable
  • type II: fracture at the base of the odontoid; unstable, and has a high risk of non-union
  • type III: through the odontoid and into the lateral masses of C2; best prognosis for healing because of the larger surface area of the fracture

Differential diagnosis

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