Reference points and lines describing the head posture on two-dimensional generated lateral cephalogram [31].
FH = Frankfurter horizontal through or and po; or = orbitale, the most inferior point of foramen orbitale; po = porion, the most inferior point of apertura acusticus.
NL = nasal line through sp and pm; sp = spinal point, the apex of in the anterior nasal spine; pm = pterygomaxillare, the intersection between the nasal floor and the posterior contour of the maxilla.
OPT = odontoid process tangent through cv2ip and cv2tg; cv2ip = the most posteroinferior point on the corpus of C2; cv2tg = the tangent point on the dorsal contour of the odontoid process of C2 to a line from cv2ip.
CVT = cervical vertebra tangent through cv4ip and cv2tg; cv4ip = the most posteroinferior point on the corpus of C4.
VER = true vertical line; HOR = true horizontal line.
Postural angles are indicated in black.