Table 1 Reference landmarks, planes and measurements

landmarks

 Porion

The superior surface of the external auditory meatus

 Orbitals

The midpoint of the infra-orbital margin

 Nasion

Nasofrontal suture at the midline

 Basion

Middle point on the anterior margin of foramen magnum

 A point

The most prominent anterior aspect of the condyle

 B point

The most prominent posterior aspect of the condyle

 C point

The most superior aspect of the glenoid fossa

Planes

 Frankfort horizontal (FH) plane

The plane that passes through the right porions and bilateral orbitales

 Midsagittal plane

The plane that is perpendicular to the Frankfort plane and passes through the Na and Ba

Lines

 Line A

The line that is tangent to point A from point C

 Line B

The line that is tangent to point B from point C

 Line C

The line that is parallel to the FH plane and intersects the glenoid fossa

Measurements

 AS

The vertical distance from point A to the glenoid fossa

 PS

The vertical distance from point B to the glenoid fossa

 SS

The vertical distance from point C to the condyle