Sexual dimorphism of the distal femur in a South African computer tomography sample

The distal femur offers reliable sex estimation markers. However, in the South African context standards for assessing sexual dimorphism from the distal femur has only incorporated limited measurements on skeletal remains. To enhance the applicability and reliability of standards, even if remains are fragmentary, the study aimed to collect an expanded set of landmarks from contemporary 3D computed tomography (CT) models to study sexual dimorphism in the distal femur. Nineteen landmarks were placed on 3D models of the CT scans of distal femurs belonging to Black South Africans (50 males and 50 females), aged 18-80 years, from which 15 linear measurements were calculated and analyzed using repeatability tests, student's t-test, Mann-Whitney test, discriminant function analysis (DFA), and geometric morphometrics. The measurements were repeatable and demonstrated significant sexual dimorphism, with males generally exhibiting larger dimensions. The distal epicondylar breadth (DEB) achieved the highest classification accuracies of 81 % in Blacks and 95 % in Whites. Discriminant function equations improved classification accuracies by 2 % in each population group respectively. Compared to linear dimensions, classification accuracies based on shape variation delivered similar percentages in Blacks but lower percentages in Whites. An expanded, accurate, and repeatable set of distal femoral measurements was produced to be applied as individual cut-off values or as part of discriminant function equations for sex estimation. The DEB was particularly valuable. Shape variation did not make a substantial difference and is not useful for fragmentary remains. The population variation observed underscores the importance of developing population-specific standards in forensic anthropology.