Anderson-D'Alonzo

C2 (odontoid) fractures

Type I

Through tip of dens. Unstable (may have associated atlanto-occipital dislocation or disruption of transverse ligament). Treat with collar or halo vest.

Type II

Through base of dens. Unstable, treat with halo vest or surgical fixation.
Preference for surgery when:

Note: children < 7 years almost always heal with immobilization alone.

Type III

Through body of C2. Can be unstable, treat with halo vest.

Reference

Greenberg's Handbook of Neurosurgery, 7th edition