Quantitative Analysis of Lower Facial Feminization: Cephalometric and AI-Based Evaluation of Surgical Outcomes in Transgender Patients.

[INTRODUCTION] Facial feminization surgery (FFS) aims to modify masculine facial characteristics to achieve traditionally feminine aesthetics. The lower jaw plays a pivotal role in gender recognition. This study quantitatively evaluates the outcomes of narrowing genioplasty and long-curved ostectomy in transgender patients using cephalometric and AI model (ChatGPT-4o)-based analyses.

[METHODS] A retrospective review was conducted on 50 male-to-female transgender patients who underwent FFS between 2019 and 2023. Preoperative and postoperative cephalometric x-rays assessed changes in gonial width, chin width, chin length, and SN-NP angle. In addition, an AI model analyzed jaw morphology using clinical photographs to evaluate gender classification and confidence levels. Statistical analyses included paired t tests and Random Forest analysis to identify significant factors influencing feminization outcomes.

[RESULTS] Postsurgical cephalometric analysis revealed significant reductions in gonial width (10.6±4.2 mm; P<0.001) and chin width (7.9±2.4 mm; P<0.001). AI-based assessments demonstrated an 89.5% reclassification rate of male-to-female gender estimation and increased confidence levels (mean improvement: 10.3%; P<0.001). Random Forest analysis identified gonial and chin width as the most influential factors in feminization. These findings emphasize the transformative impact of FFS in reshaping the lower jaw.

[CONCLUSION] The authors found that the FFS of the lower jaw significantly enhances feminization outcomes, as validated by cephalometric and AI-based analyses. Especially, gonial width and chin width are crucial factors that affect gender recognition. Thus, to maximize feminization effects in lower jaw surgery, overcorrection of feminine characters of the jawline, such as a tapered chin and slender jaw width, might be advised.