Open camera or QR reader and scan code to access this article and other resources online. Sex Differences in Adult Facial Three-Dimensional Morphology: Application to Gender-Affirming Facial Surgery Jordan J. Bannister, BASc, 1 Hailey Juszczak, MD, 2 Jose David Aponte, MSc, 3 David C. Katz, PhD, 3 P. Daniel Knott, MD, 2 Seth M. Weinberg, PhD, 4 Benedikt Hallgrı ´msson, PhD, 3 Nils D. Forkert, PhD, 5 and Rahul Seth, MD 2, * Abstract Background: Gender-affirming facial surgery (GFS) is pursued by transgender individuals who desire facial features that better reflect their gender identity. Currently, there are a few objective guidelines to justify and facilitate effective surgical decision making. Objective: To quantify the effect of sex on adult facial size and shape through an analysis of three- dimensional (3D) facial surface images. Materials and Methods: Facial measurements were obtained by registering an atlas facial surface to 3D sur- face scans of 545 males and 1028 females older than 20 years of age. The differences between male and female faces were analyzed and visualized for a set of predefined surgically relevant facial regions. Results: On average, male faces are 7.3% larger than female faces (Cohen’s D = 2.17). Sex is associated with significant facial shape differences ( p < 0.0001) in the entire face as well as in each sub-region considered in this study. The facial regions in which sex has the largest effect on shape are the brow, jaw, nose, and cheek. Conclusions: These findings provide biologic data-driven anatomic guidance and justification for GFS, particularly forehead contouring cranioplasty, mandible and chin alterations, rhinoplasty, and cheek modifications. Introduction Facial appearance serves a major role in communication and social interaction. This is evidenced by the exis- tence of an area in the human brain dedicated to the identification of sex, identity, age, and race at a sin- gle glance. 1 This fact poses a unique challenge to the transgender population, which was recently estimated to be roughly 1 million people in the United States. 2 Facial surgery enables structural changes to the face, which can help a patient to fully assume a facial ap- pearance that is concordant with their gender identity, thereby reducing misgendering and gender dysphoria 1 Department of Biomedical Engineering, University of Calgary, Calgary, Canada.. 2 Division of Facial Plastic and Reconstructive Surgery, Department of Otolaryngology - Head and Neck Surgery, University of California San Francisco, San Francisco, California, USA. 3 Department of Cell Biology and Anatomy, Alberta Children’s Hospital Research Institute and McCaig Bone and Joint Institute, Cumming School of Medicine, University of Calgary, Calgary, Canada. 4 Department of Oral and Craniofacial Sciences, Center for Craniofacial and Dental Genetics, University of Pittsburgh, Pittsburgh, Pennsylvania, USA. 5 Department of Radiology, Alberta Children’s Hospital Research Institute and Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Canada. *Address correspondence to: Rahul Seth, MD, Division of Facial Plastic and Reconstructive Surgery, Department of Otolaryngology- Head and Neck Surgery, University of California San Francisco, 2320 Sutter Street, San Francisco, CA 94115, USA, Email: rahul.seth@ucsf.edu Facial Plastic Surgery & Aesthetic Medicine Volume 0, Number 0, 2022 ª American Academy of Facial Plastic and Reconstructive Surgery, Inc. DOI: 10.1089/fpsam.2021.0301 1 Downloaded by 44.201.69.196 from www.liebertpub.com at 07/01/22. For personal use only.