Frankfort Horizontal Plane
Pronunciation: FRANK-fort hoh-RIZ-on-tal plane
A standardised cephalometric reference plane defined by the inferior margin of the orbit (orbitale) and the superior margin of the external auditory meatus (porion), used to orient the skull for radiographic analysis.
Full Definition
The Frankfort Horizontal Plane is a widely adopted craniometric reference line that connects the point porion (upper border of the external auditory meatus) to the point orbitale (lowest point of the orbital rim). It serves as a horizontal baseline in lateral cephalometric tracings against which other planes and angles are measured. When a patient is positioned with this plane parallel to the floor, the head is considered to be in natural head position. Editors must be careful to capitalise 'Frankfort' as it is an eponymous geographic reference, and to note the accepted variant spelling 'Frankfurt' used in some European literature.
Usage
Usage note: Both 'Frankfort' and 'Frankfurt' are acceptable; verify house style and apply consistently throughout the document.
In Context
- "The clinician measured the mandibular plane angle relative to the Frankfort Horizontal Plane to assess the patient's vertical skeletal pattern." — Clinical case report
- "Inconsistent orientation of the Frankfort Horizontal Plane between serial radiographs may introduce superimposition error." — Research methods section