Odontoid process fracture, also known as a peg or dens fracture, occurs where there is a fracture through the odontoid process of C2.
The mechanism of injury is variable, and can occur both during flexion or extension, and with or without compression .
There are two classification systems
- Anderson and D'Alonzo
- most commonly used
- describes level of fracture line (i.e. through tip, base, or lateral masses)
- Roy-Camille classification
- has been shown to better correlate with prognosis
- describes plane of fracture and displacement