Quantification of Changes in Chin Morphometric Parameters Following Feminization Genioplasty

Genioplasty is frequently performed in facial feminization surgery, typically aiming to reduce chin height and projection for more feminine appearance. Quantification of the bony changes occurring during surgery have to date not been published. This study presents a method for segmentation of the chin using CT imaging to quantify changes to the chin after feminization genioplasty. CT scans of 21 patients before and after feminization genioplasty were segmented in Mimics to isolate the chin region. Surface area, volume, vertical chin projection, and horizontal chin projection were measured before and after surgery. Patient outcomes were evaluated using the FACE-Q and World Health Organization Quality of Life patient-reported outcome measures. Surface area, volume, and vertical chin projection demonstrated statistically significant decreases after surgery. The magnitude of changes in surface area and vertical chin projection were significantly associated with their presurgical values. In particular, patients with greater presurgical vertical projections experienced greater decreases in vertical projection after surgery, with some patients having increases in postsurgical vertical projection. Patient FACE-Q scores improved significantly on all scales, including chin, jawline, and neck satisfaction. This study demonstrates a method for evaluating bony changes on CT scan after feminization genioplasty. The measured changes cohere with the changes expected to create a more feminine chin. Furthermore, changes created by feminization genioplasty are in the context of the patient's overall facial harmony and are not uniform across all patients.