Sexual dimorphism and determination using foot outlines, foot print angles, and foot indices

Sex determination is one of the fundamental procedures in the forensic investigation during personal identification. Foot dimensions, prints, indices, and angles are assessment tools used by podiatrists and forensic anthropologists. The arch index remains a tool for clinical evaluation of the incidence of pes planus by clinicians. This cross-sectional study was performed to investigate sexual dimorphism and discriminate sex using foot and footprint dimensions, foot angles, and foot indices among the Ebira ethnic group of Nigeria. Bilateral foot outlines and prints were obtained from 317 females and 283 males using a digital Vernier caliper, improvised footpad, and A4 paper. The results revealed that in the right foot and print, the males' bare right foot length (BRFL), bare right foot breadth (BRFB), right arch index (RAI), right Chippaux-Smirak index (RCSI), right footprint angle (RFPA), right ball angle (RBA), and all the measurements of the corresponding toes in the prints are significantly greater (p < 0.05) than the females. The same trend was also observed in the left footprint except for the left ball angle (LBA). The stepwise, binary logistics regression model for sex determination showed that bare left foot breadth (BLFB) and bare right foot length (BRFL) were the single best predictors of sex with an accuracy of 72.5% and 71.7% accuracy. Other foot variables marginally increased the percentage accuracy at each step. The receiver operating characteristic (ROC) curve analysis confirmed the sexing potential of the bare left foot breadth and bare right foot length to be 79%. Sexual dimorphism exists in all the foot dimensions, arch indices, Chippaux-Smirak indices, footprint angles, and ball angles, except the left ball angle. The sexual dimorphism in the foot variables forms the basis of sex determination, with left foot breadth and right foot length as the best sex predictors. Therefore, 25 cm can be regarded as the cut-off point for foot length and 9 cm as the cut-off point for foot breadth among this tribe.