Quantitative Analysis of Sexual Dimorphism in Three-Dimensional Facial Anthropometry in Contemporary Thai Population: Implications for Facial Feminization Surgery

Abstract

Facial feminization surgery (FFS) reshapes masculine facial attributes to align with feminine norms, yet normative anthropometric data for Asian populations remain sparse. We therefore quantified sex-related 3-dimensional (3D) facial metrics in healthy Asian adults to delineate dimorphic benchmarks for surgical planning. We prospectively recruited 40 healthy Asian adults (20males, 20females; age 18 to 45years, mean 28.6years; body mass index 21.8 kg/m2) and obtained 3D images with the VectraXT3D system. Linear and angular metrics for the upper, middle, and lower facial thirds were compared between sexes with independent-samples ttests (α=0.05). Male faces showed greater vertical dimension (196.7 mm versus 190.3 mm, P=0.023), broader zygomatic (127.9 mm versus 120.7 mm, P<0.001), and mandibular widths (124.4 mm versus 113.8 mm, P<0.001). They also had longer noses (43.7 mm versus 37.9 mm, P<0.001) with increased tip projection (23.9 mm versus 19.8 mm, P<0.001) and more acute glabellar (146.8° versus 150.9°, P=0.025) and nasofrontal (137.1° versus 142.6°, P=0.011) angles. Female faces displayed increased forehead convexity (ratio 1.030 versus 1.011, P<0.001), steeper palpebral slant (9.4° versus 6.2°, P<0.001), and wider columella-labial angle (109.6° versus 104.6°, P=0.032). They also exhibited a more obtuse gonial angle (135.4° versus 129.6°, P=0.002) and shorter upper lip (23.9 mm vs. 26.0 mm, P=0.007). Age and body mass index did not differ between sexes. These quantitative benchmarks delineate sexual dimorphism in Asian visages and furnish evidence-based targets for FFS planning. Effective FFS should reduce bony and soft-tissue prominence, create obtuse angles, and incorporate targeted lifting to reproduce the feminine template, thereby enhancing gender-affirming outcomes.