Sex Differences in the Femur and Acetabulum: Biomechanical Analysis with Forensic Significance
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Knowing the relationship between pelvic and femur morphology is essential for understanding femoral developmental plasticity, sexual dimorphism, and morphological changes associated with habitual load levels. The purpose of this Master’s thesis is to examine how pelvic dimensions influence the shape of the femur within a biomechanical framework in a modern American White population. Specifically the research examines the relationship between sex differences in biacetabular breadth and femoral functional angles, and whether these differences are significant enough to provide a forensically relevant equation for estimating sex with the femur. Sexual dimorphism in pelvic dimensions and femoral angles of 30 males and 30 females were analyzed using landmarks on a 3D Cartesian coordinate system with geometric morphometric techniques to provide a visual representation of overall shape change in the femur and pelvis between males and females. A Principle Component Analysis (PCA) with Procrustes coordinates revealed significant shape differences in epicondylar breadth, acetabular version, and iliac flare between males and females. Analysis of the raw metric data also showed significant sexual dimorphism in the biacetabular breadth, biomechanical neck length, femoral neck-shaft angle, femoral angle of version, and the bicondylar angle. A Discriminant Function Analysis (DFA) was utilized for the forensic application component with a classification percentage of 85, with a stepwise procedure. Regression analysis demonstrated significant relationships to exist between several variables, including biacetabular breadth, the neck-shaft angle, and the bicondylar angle. The findings also show that the neck-shaft angle and biomechanical neck length are correlated with the bicondylar dimensions. Overall, this research indicates that the femoral and pelvic morphological traits are multi-factorial and reflect biomechanical adaptations to varying dimensions among humans, which has applications for reconstructing modern and fossil human femoral plasticity and variation.