Table 2 The landmarks and the reference plane
Landmark (abbreviation) | Definition |
|---|---|
Landmarks | |
Na (nasion) | “V” notch of frontal and nasal bones |
Ba (basion) | Most inferior point of the occipital bone |
Or (orbitale) | Most inferior point of the orbital contour |
Po (porion) | Most superior point of the external auditory meatus |
Se (sella) | Center of sella turcica |
Anterior nasal spine (ANS) | Tip of the anterior nasal spine |
B point (B) | Deepest point between pogonion and lower incisal alveolus |
CV1 | Most anterior inferior point of the anterior arch of the atlas |
CV2 | Most anterior inferior point of the body of the 2nd cervical vertebra |
CV4 | Most anterior inferior point of the body of the 4th cervical vertebra |
Reference plane | |
Frankfort horizontal (FH) plane | Faces through the right porion and both sides of the orbitalia |
Midsagittal plane | A plane perpendicular to the FH plane passing through Na and Ba |
Sella vertical (SV) plane | A plane perpendicular to the FH plane passing through Se, Ba, and Na |
CV1 plane | A plane parallel to the FH plane passing through CV1 |
CV2 plane | A plane parallel to the FH plane passing through CV2 |
CV4 plane | A plane parallel to the FH plane passing through CV4 |