Anderson and D'Alonzo classification of odontoid process fracture

The Anderson and D'Alonzo classification is the most commonly used classification of fractures of the odontoid process of C2.

Classification

  • type I
    • rare
    • fracture of the upper part of the odontoid peg (generally obliquely)
    • above the level of the transverse band of the cruciform ligament
    • usually considered stable
  • type II
    • most common
    • transverse course fracture at the base of the odontoid
    • below the level of the transverse band of the cruciform ligament
    • unstable
    • high risk of non-union
  • type III
    • through the odontoid and into the lateral masses of C2
    • relatively stable if not excessively displaced
    • best prognosis for healing because of the larger surface area of the fracture

Another classification system is the Roy-Camille classification.