Anderson and Montesano Classification of Occipital Condyle Fractures.

Type I: Injuries are comminuted, usually stable, impaction fractures caused by axial loading. Type II: Injuries are impaction or shear fractures extending into the base of the skull and are usually stable. Type III: Injuries are alar ligament avulsion fractures and are likely to be unstable distraction injuries of the craniocervical junction.

(From SchoenfeldAJ, LeHV, BonoCM. Cervical spine fractures and dislocations. In: TornettaP III, RicciWM, OstrumRF, et al., eds. Rockwood and Green’s Fractures in Adults. Vol 2. 9th ed. Philadelphia: Wolters Kluwer; 2020:1817–1899.)