Morphometric analysis and spatial localization of the infraorbital foramen in adult dry human skulls: bilateral symmetry, sexual dimorphism, and accessory foramina.

Background: The infraorbital foramen (IOF) is a key anatomical landmark for infraorbital nerve block, maxillofacial surgery, and orbital reconstruction. However, its location and morphology exhibit considerable individual and population-based variation, emphasizing the need for population-specific morphometric data. Methods: This anatomical study evaluated 103 adult dry human skulls (206 hemimaxillae). Bilateral measurements of IOF coordinates, dimensions, and distances to adjacent anatomical landmarks, craniofacial measurements (bizygomatic width and upper facial height), IOF shape and orientation, and the presence of accessory infraorbital foramina (AIOF) were obtained. Morphometric indices, including the lateralization index, vertical position index, and alveolo-orbital ratio, were calculated. Bilateral and sex-related differences were analyzed using appropriate parametric statistical tests. Correlation analyses were performed to investigate relationships between IOF morphology and craniofacial dimensions. Spatial distribution of the IOF was evaluated using kernel density estimation, and receiver operating characteristic (ROC) analysis was performed to assess morphometric predictors of AIOF. Results: Significant bilateral differences were observed for horizontal and vertical IOF coordinates, lateralization index, and vertical position index, which were statistically different between sides, whereas foraminal diameters, IOF-infraorbital margin distance, IOF-alveolar crest distance, and alveolo-orbital ratio showed no significant side differences. Male skulls demonstrated significantly greater bizygomatic width, upper facial height, and horizontal and vertical IOF coordinates, whereas females exhibited significantly higher vertical position indices, with all these parameters being statistically different between sexes. Strong positive correlations were identified between craniofacial dimensions and IOF localization. AIOFs were identified in 18.4% of hemimaxillae without significant side predominance. Skulls with AIOFs exhibited significantly smaller vertical IOF diameters, shorter IOF-infraorbital margin distances, and higher alveolo-orbital ratios. ROC analysis demonstrated excellent predictive performance for mean vertical IOF diameter (AUC = 0.995) and mean IOF-infraorbital margin distance (AUC = 0.950). Conclusion: The infraorbital foramen demonstrates subtle bilateral asymmetry and significant sex-related variation that reflect overall craniofacial morphology. The integration of morphometric indices, spatial density mapping, and AIOF-related analyses provides a comprehensive framework for anatomical assessment of the infraorbital region. These findings offer clinically relevant reference data for infraorbital nerve block, maxillofacial surgery, orbital reconstruction, and related procedures involving the midface.