Fig. 3.

Morphometric parameters concerning course of the VA and screw placement inside C1-2. VAG distance between mid-sagittal-line C2 and vertebral artery groove C2—own results, EVA distance between entry point of vertebral artery to mid-sagittal-line C2, SFFA superior frontal facet angle C2, SFA superior facet angle C1 and C2, iFBW inferior frontal body width, PW width between mid-sagittal-line C2 and medial offset of superior facet C2 including the ‘real’ pedicle C2, IHLM internal height of lateral mass, m/f data separated for male and female specimen