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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