Measurement · EFFMAND
Effective mandibular length (Co–Gn)
Loading the reference ceph.
Definition
The straight-line distance from Condylion (the most posterosuperior point of the condyle) to Gnathion (the chin point) — McNamara's 'effective length' of the mandible.
How
Measure the linear distance Co→Gn in mm. It is compared against effective midfacial length (Co–A) via the maxillomandibular differential, not read in isolation.
Purpose
Quantifies how much mandible the patient actually has, on the same axis the jaw 'works' along. Paired with Co–A it separates a truly short mandible from one that is normal-sized but positioned back — a key distinction for functional-appliance vs camouflage planning.
High
Above the norm reads as a long mandible for the face (contributes to a Class III / prognathic pattern).
Low
Below the norm reads as a short mandible (micrognathia / Class II from mandibular deficiency — the most common Class II etiology).
This is a reviewed tracing on one real cephalogram — the same ceph on every page in Learn — so Effective mandibular length (Co–Gn) here is a real reading and not a diagram.