Anterior Nasal Spine
A bony projection at the midline of the base of the nasal aperture, used as a cephalometric landmark denoted ANS.
Full Definition
The anterior nasal spine (ANS) is a sharp bony process projecting anteriorly at the inferior margin of the piriform aperture of the maxilla. On lateral cephalograms it is identified as a pointed projection and serves as the superior reference point for measuring lower anterior facial height (ANS to Me). Together with the posterior nasal spine (PNS), it defines the palatal plane. Editors should ensure ANS is not confused with 'nasion' (the frontonasal suture landmark) or 'anterior cranial base' measures. In cephalometric tables, ANS is typically denoted in uppercase without periods.
Usage
Usage note: Abbreviate as ANS (no periods). Do not confuse with nasion (N), which is on the frontonasal suture, not on the maxilla.
In Context
- "The palatal plane was constructed by joining the anterior nasal spine to the posterior nasal spine." — Cephalometric tracing instructions
- "Lower anterior facial height was measured from the anterior nasal spine (ANS) to menton (Me), recording 68 mm." — Cephalometric analysis report