Quantitative Analysis of Male Versus Female Frontal Bone and Orbital Skeletal Morphology.

Background: As the field of facial feminization surgery expands, plastic surgeons have increasingly sought to better understand differences in skeletal morphology between men and women. This study investigated sex-based differences in the frontal bone and orbital regions by quantitatively describing morphological variability in an adult cisgender population.

Methods: We reviewed healthy adults who underwent head computerized tomography imaging before orthognathic surgery. Standardized sets of 501 digital landmarks were used to capture surface morphometrics of the forehead, supraorbital ridges, and orbital rims. All landmarked crania were aligned using Generalized Procrustes Analysis. Principal component analysis evaluated the contribution of sex to the overall variance in coordinates. Using robust rank aggregation, a ranked list of important landmarks or "features" most predictive of sex was generated after integrating mean feature differences, linear discriminant analysis, and random forest importance scores.

Results: A total of 154 patients were analyzed, including 70 (45%) men and 84 (55%) women imaged at 23.6 ± 7.7 and 26.0 ± 11.1 years of age, respectively. A list of 119 important features with significant aggregate rank scores (P < 0.05) demonstrated the greatest sex-based variability at the (1) upper forehead, (2) glabella and medial brow prominences, and (3) outer infraorbital rims, primarily in the posterior/anterior direction.

Conclusions: We identified key anatomical regions of the upper facial third with the greatest sex-based variability. Our findings provide an objective framework upon which continued investigations of skeletal dimorphisms may be performed and provide preliminary data to help guide preoperative counseling and surgical planning for facial feminization surgery.