Anderson and D'Alonzo classification of odontoid process fracture

Last revised by Mohammad Taghi Niknejad on 4 Jun 2024

The Anderson and D'Alonzo classification is the most commonly used classification of fractures of the odontoid process of C2 1.

Another classification system is the Roy-Camille classification, which aids more in the management of odontoid fractures.

Classification

  • type I

    • rare

    • fracture of the upper part of the odontoid peg (generally oblique)

    • 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 IIa

    • ​type II fractures with comminution at the odontoid base

    • Hadley 2 described this type of fracture which has a significantly increased risk of nonunion when treated non-operatively compared with classical type II fractures

    • represents 5-10% of type II fractures

  • 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

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