Factors affecting nostril shape in Asian noses

BACKGROUND: Because few studies have been performed regarding the factors affecting nostril shape in Asian noses, this study was undertaken to determine them. METHODS: A total of 20 fresh cadaver noses were classified into horizontal and vertical types and dissected. The authors investigated the presence, volume, and insertions of muscles surrounding the ala; alar cartilage shape; footplate segment ratio of the medial crus; and the characteristics of tip supporting structures. RESULTS: Horizontal nostril types had larger dilator naris anterior and posterior muscular components. In particular, the insertion of the dilator naris posterior muscle extended to the midpoint between the alar base and the nasal tip, whereas that of the vertical type was limited to the alar base. Insertion of the depressor septi nasi muscle was also more extensive in horizontally oriented nostrils. In terms of the shape of the lower lateral cartilage, the horizontal nostril type had a predominantly concave configuration of the lateral crus, whereas the vertical nostril type had the opposite concave configuration. A significant difference was also noted in the footplate segment ratio of the medial crus. However, no differences were observed in terms of the shape of the medial crus and the characteristics of the tip supporting structures. CONCLUSIONS: Nostril shape is mainly affected by the volume of the dilator naris anterior and posterior muscle, the insertions of the dilator naris posterior and the depressor septi nasi muscle, the shape of the lateral crus, and the footplate segment ratio.