Change of the airway space in mandibular prognathism after bimaxillary surgery involving maxillary posterior impaction

Maxillofacial Plastic and Reconstructive Surgery

Table 3 Anatomical limits of the airway

Region	Limit	Anatomical
Nasopharynx	Anterior	Frontal plane perpendicular to FH passing through PNS
	Posterior	Soft tissue contour of the pharyngeal wall
	Upper	Soft tissue contour of the pharyngeal wall
	Lower	Plane parallel to FH passing through ANS and extended to the posterior wall of the pharynx
Oropharynx	Anterior	Frontal plane perpendicular to FH passing through PNS
	Posterior	Soft tissue contour of the pharyngeal wall
	Upper	Plane parallel to FH passing through ANS and extended to the posterior wall of the pharynx
	Lower	Plane parallel to FH plane passing through C2ai
Hypopharynx	Anterior	Frontal plane perpendicular to FH passing through PNS
	Posterior	Soft tissue contour of the pharyngeal wall
	Upper	Plane parallel to FH plane passing through C2ai
	Lower	Plane parallel to FH connecting the base of the epiglottis to the entrance to the esophagus

Abbreviations: FH Frankfort horizontal plane, ANS anterior nasal spine, PNS posterior nasal spine, C2ai anteroinferior point of secondary cervical vertebrae