Table 2 Cephalometric landmarks and measurements of the upper airway
From: Cephalometric norms for the upper airway of 12-year-old Chinese children
| Variables | Definition |
|---|---|
| Landmarks | |
| Po | Porion, the mid point of the line connecting the most superior point of the external auditory canal on both sides |
| Or | Orbitale, the lowest point on the average of the left and right inferior borders of the bony orbit |
| ANS | Anterior nasal spine, the tip of the median, sharp bony process of the maxilla |
| PM | Pterygo-maxillare, the point at the junction fo the pterygo-maxilla and the posterior nasal spine |
| U | Uvula, the tip of the uvula |
| UPW | Upper pharyngeal wall, point of intersection of the line NL to the posterior pharyngeal wall |
| MPW | Middle pharyngeal wall, intersection of the perpendicular line from U to the posterior pharyngeal wall |
| LPW | Lower pharyngeal wall, intersection of the perpendicular line from V to the posterior pharyngeal wall |
| V | Vallecula, the intersection of the epiglottis and the base of the tongue |
| AH | Anterior hyoid, the most anterior and superior point on the body of the hyoid bone |
| C2 | 2nd cervical vertebrae, the point at the most anterior-inferior position on the second cervical vertebrae |
| C3 | 3rd cervical vertebrae, the point at the most anterior-inferior position on the third cervical vertebrae |
| FH | Frankort horizontal plane, line joining the Or to the Po |
| NL | Nasal line, line joining the ANS and Pm |
| CV | Cervical vertebrae, the line joining the C2 and C3 |
| Measurements | |
| PM-U (mm) | Length of soft palate, distance from PM to U |
| SPT (mm) | Soft palate thickness, represents the maximal thickness of the soft palate measured perpendicular to PM-U line |
| NL/PM-U (°) | Inclincation of the long axis of the soft palate relative to the nasal line |
| PM-UPW (mm) | Depth of the nasopharyngeal airway space from PM to UPW |
| U-MPW (mm) | Depth of the oropharyngeal airway space from U to MPW |
| PASmin (mm) | The shortest distance between the base of the tongue and the posterior pharyngeal wall, the narrowest sagittal airway space |
| V-LPW (mm) | Depth of the hypopharyngeal airway space from V to LPW |
| AH-FH (mm) | Position of the hyoid bone in vertical plane, from AH perpendicular to FH |
| AH-CV (mm) | Position of the hyoid bone in horizontal plane, from AH to CV and parallel to FH |