Unit 4 of 7
Frankfort and the ramus
The horizontal the head is levelled by, and the two points behind the jaw.
The card
Frankfort horizontal is the plane a head is levelled on, and it is built from the two hardest points on a lateral cephalogram. This unit is deliberately fourth: Porion is the point everybody gets wrong first, and it goes much better once you have placed twenty other things.
- Porion is the roof of the external auditory meatus — not the ear-rod ring that sits over it and is brighter.
- Orbitale is the lowest point of the bony orbital rim, averaged where the two orbits do not superimpose.
- Articulare is a crossing, not a bone: the posterior ramus against the base of the skull. Condylion is the top of the condyle itself.
- FMA is Frankfort against the mandibular plane, and it is the vertical read the whole Tweed philosophy is built on.
What you will place