Peg fractures are classified according to the Anderson and D’Alonzo system [16].
| Type I | Fractures involve the upper portion of the odontoid process only. These are stable injuries, but there is a risk of avascular necrosis. |
| Type II | Fractures involve the base of the odontoid process. These are unstable injuries and usually require operative intervention. |
| Type III | Injuries extend into the body of C2. These are stable injuries. |