Odontoid fracture

Last revised by Craig Hacking on 8 Feb 2024

Odontoid process fracture, also known as a peg or dens fracture, occurs where there is a fracture through the odontoid process of C2.

Pathology

The mechanism of injury is variable, and can occur both during flexion or extension, and with or without compression 5.

Classification

There are two classification systems 5,6

  • Anderson and D'Alonzo

    • most commonly used, describes level of fracture line (i.e. through tip, base, or lateral masses)

    • Type I: Avulsion fracture of the upper dens; usually stable

    • Type II: Transverse fracture of the base of dens; unstable

    • Type III: Fracture at the body of C2

  • Roy-Camille classification

    • has been shown to better correlate with prognosis

    • describes plane of fracture and displacement

Differential diagnosis

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