Sexual Dimorphism of Frontal Sinus: A 2-Dimensional Geometric Morphometric Analysis on Lateral Skull Radiographs

Abstract

• Sex identification is a keystone in forensic investigation. • Frontal sinus is a reliable method of sex identification. • Geometric morphometric analysis provides better accuracy in sex identification. • Frontal sinus is a novel tool for sex identification among Malaysians. Sex identification is vital in establishing biological identity of unknown remains. In cases of fragmented skeletons, the resiliency of the frontal sinus suggests its potential in establishing biological identity. The traditionally used linear measurement has low reliability and is size-oriented, whereas geometric morphometrics is efficient as being reliable in characterising the shape. However, the frontal sinus approach for sex identification among Malaysians is yet to be explored. This study aims to evaluate sexual dimorphism of frontal sinus among Malaysians using the two-dimensional (2D) geometric morphometrics method. Lateral skull radiographs of 453 adult Malaysian, comprising 228 males and 225 females, were retrieved retrospectively. Eight 2D landmarks were applied to the lateral skull radiographs using TPSDig2 software. 2D geometric morphometric analysis was performed by MorphoJ software. The Principal Component Analysis (PCA) showed that the first three Principal Component (PCs) exhibit 83.0% of the total variance of the frontal sinus shape. Procrustes analysis of variance (ANOVA) revealed significant differences in centroid size and shape ( p -value < 0.05) of frontal sinus between sexes. Discriminant Function Analysis (DFA) after cross-validation demonstrated a classification accuracy of 78.5% in males and 82.7% in females, with an average of 80.6%. High classification accuracy suggests that frontal sinus is a valuable tool for sex identification using 2D geometric morphometrics. The significant sexual dimorphism of the frontal sinus shape indicates its capability to aid in forensic investigation. To the best of our knowledge, this is the first study which showed such findings among Malaysian population.