Posterior Nasal Spine
The most posterior midline bony projection of the hard palate, used as a cephalometric landmark and denoted PNS.
Full Definition
The posterior nasal spine (PNS) is the pointed posterior tip of the horizontal plate of the palatine bone, situated at the midline of the posterior hard palate. On lateral cephalograms it marks the posterior end of the palatal plane (ANS-PNS line) and is used in assessing palatal inclination relative to other reference planes. In dentofacial orthopedics, PNS is relevant in evaluating the effects of maxillary impaction or downward rotation on palatal plane changes. Editors should note PNS is frequently cited alongside ANS in cephalometric data tables and must not be confused with 'pterygomaxillary fissure,' which is a different radiographic landmark in the same region.
Usage
Usage note: Abbreviate as PNS (no periods). Distinguish from pterygomaxillary fissure, which is lateral and superior, not a midline hard-palate landmark.
In Context
- "The palatal plane, constructed from the anterior nasal spine to the posterior nasal spine, was inclined 8° to the Frankfort horizontal." — Cephalometric analysis
- "Post-surgical superimposition revealed a 3 mm superior repositioning of the posterior nasal spine following Le Fort I impaction." — Surgical outcome report