Determination of Sex from the Foramen Magnum using 3DCT: A Nepalese Study

Background Identification is of utmost importance in any medicolegal investigation with sex determination being one of the principle indicators of identity. Sexing of bones becomes easy when the skeletal remains are complete. However, the problem arises when the bones are fragmented. Many researchers have undertaken several studies in different populations to determine the sex with reasonable accuracy using numerous measurements of the skull including those of the foramen magnum. Objective The present study was aimed to find the sexual dimorphism of the foramen magnum in the Nepalese population by analyzing the antero-posterior length, transverse diameter and area of the foramen magnum. Method The antero-posterior length and transverse diameter of the foramen magnum were measured using three-dimensional computed tomography (3DCT) images of the head in a cohort of 100 Nepalese subjects. Radinsky's and Teixeria's formulae were used to calculate the area of the foramen magnum. Discriminate function analysis was used to analyze sex differences. Result Mean values of antero-posterior length and transverse diameter of the foramen magnum in males were higher than in females. The mean of the area calculated using Radinsky's formula was smaller than that calculated by Teixeira's formula and the areas calculated were higher in males. The measurements of the foramen magnum and the areas calculated showed significant difference (p<0.001) between males and females. Discriminate function analysis for the measurements of the foramen magnum and the areas calculated showed high predictability for both the sexes. Discriminate function analysis showed a maximum predictability of 75%. Conclusion Considering the percent of predictability of sex from the various variables related to the foramen magnum in the Nepalese population, it can be concluded that its restricted applicability in forensic investigations should be constrained to cases of fragmentary skull bases.