Analysis of Cephalometric Points in Male and Female Mandibles: An Application to Gender-Affirming Facial Surgery

Abstract

Gender-affirming facial surgery is a common intervention for transgender patients because of its ability to decrease the frequency of misgendering. Many anatomic targets can be addressed, but the mandible is the primary aspect of the lower third of the face that is manipulated during these procedures. This study’s objective is to quantify the differences in cephalometric measurements between male and female mandibles on maxillofacial imaging, with the goal of identifying surgical targets for gender affirmation. A nonrandomized, retrospective, single-institution, case-control study of 387 patients who underwent maxillofacial computed tomography during 2017-2020 was performed. After excluding patients with imaging that did not capture the entire head or had deforming pathology of the face, a total of 113 patients were included. Cephalometric measurements that corresponded to areas reported by patients as sources of dysphoria were selected for analysis. These included mandibular width, ramus height, lateral flare, masseter volume, total face height, and the values of the mandibular angles in degrees. The relationship of masseter volume to the other measurements was also characterized. Significantly greater masseter volume was seen in males compared with females, and a greater masseter thickness was also seen in males. The mandibular angle was more acute in males than females. Aggregate analysis of muscle volume and thickness was positively correlated with ramus height, lateral flare, and mandibular width. Ramus, mental, and total facial height correlated directly with patient height in males but not in females. These data provide a normative baseline for planning lower facial gender-affirming surgery.