“Soft-Tissue Response to Hard Tissue Changes Following Facial Feminization Surgery: A Three-Dimensional Region-Based Study”

BACKGROUND: Facial feminization surgery (FFS) involves bony modifications of the forehead, chin, and mandible. Accurately estimating the millimeter-level bony modification required to achieve the desired aesthetic outcome remains a challenge. Presented is the first analysis comparing bone anatomic changes to perceived soft tissue changes in FFS. METHODS: Computed tomography (CT) scans were obtained pre- and postoperatively, while three-dimensional (3D) photographs were acquired preoperatively and ≥6 months postoperatively (N = 70). Cephalometric and anthropometric landmarks were used to calculate bony and soft tissue parameters. Correlations and soft tissue-to-bony change ratios were computed for five paired parameters across facial regions. Multivariable regression assessed body mass index (BMI), age at surgery, duration of hormone therapy, and local soft tissue thickness as predictors of the soft tissue response ratio. RESULTS: Significant correlations were observed between soft tissue and bony changes for all paired measures. In the gonial region, soft tissue reduction exceeded bony reduction (response ratio 1.85 [95% CI: 1.02-2.67]). Ratios were near 1:1 for forehead projection (0.98 [95% CI: 0.92-1.14]) and lower for the bossing angle (0.70 [95% CI: 0.51-0.89]), chin horizontal projection (0.83 [95% CI: 0.37-1.30]), and chin vertical projection (0.52 [95% CI: 0.03-1.01]). Variability in response ratios across regions paralleled differences in soft tissue thickness. Within regions, however, soft tissue thickness, BMI, age, and duration of hormone therapy were not significant predictors. CONCLUSIONS: Our findings suggest that the soft tissue response to bony change is region-specific and variable. Recognizing regional patterns may enhance surgical planning precision.