Fig. 2.

Construction of reference planes. a: Front view of relevant anatomical landmarks. b: Top view of relevant anatomical landmarks. c: Three reference planes—SRP, sagittal reference plane (plane through N, Ba, and IF); FHP, Frankfort horizontal plane (plane perpendicular to the SRP and passing through two points: the midpoint of IAF-L and IAF-R and the midpoint of Or-L and Or-R); and CRP, coronal reference plane (plane passing through S and perpendicular to the SRP and FHP)