The Powers Ratio is Determined by Drawing a Line from the Basion (B) to the Posterior Arch of the Atlas (C) and a Second Line from the Opisthion (O) to the Anterior Arch of the Atlas (A). The Length of the Line Bc is Divided by the Length of the Line Oa, Producing the Powers Ratio.

(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.)