STANDARDS: There is insufficient evidence to support treatment standards. GUIDELINES: There is insufficient evidence to support treatment guidelines. OPTIONS: Treatment of atlas-axis combination fractures based primarily on the specific characteristics of the axis fracture is recommended. External immobilization of most C1-C2 combination fractures is recommended. C1-Type II odontoid combination fractures with an atlantodens interval of 5 mm or more and C1-hangman's combination fractures with C2-C3 angulation of 11 degrees or more should be considered for surgical stabilization and fusion. In some cases, the surgical technique must be modified as a result of loss of the integrity of the ring of the atlas.