Measurement · SADDLE
Saddle angle (N-S-Ar)
Loading the reference ceph.
Definition
The first Björk polygon angle: at Sella, between the anterior cranial base (S→N) and the line down to Articulare (S→Ar).
How
At S, measure the angle between S→N and S→Ar (norm ≈ 123°).
Purpose
Fixes where the condyle 'hangs' from the cranial base: a large saddle angle sets the TMJ (and mandible) back and predisposes to a retrognathic profile; a small one seats the jaw forward. One of the three angles whose sum predicts growth rotation.
High
Above the norm reads as posterior condylar position — retrognathic tendency, adds to the polygon sum (clockwise growth).
Low
Below the norm reads as anterior condylar position — prognathic tendency, subtracts from the sum (counterclockwise growth).
This is a reviewed tracing on one real cephalogram — the same ceph on every page in Learn — so Saddle angle (N-S-Ar) here is a real reading and not a diagram.