Sex estimation from foramen magnum dimensions in an Indian population

Identification of skeletal remains is vital in forensic investigations. The need for methods to estimate sex from cranial fragments becomes apparent when only a part of skull is brought for identification. The present research is an attempt to study the sexual dimorphism of the anteroposterior diameter, transverse diameter and area of foramen magnum in a population of costal Karnataka region using statistical considerations. Ninety adult dry skulls of known sex (50 male and 40 female) were included in the study. Morphometric analysis of foramen magnum was conducted using vernier calipers and the area of foramen magnum was calculated. The anteroposterior diameter, transverse diameter and area of foramen magnum are found to be significantly larger in males than females. Binary Logistic Regression (BLR) analysis was performed to derive models for estimation of sex from the different measurements of foramen magnum and Receiver Operating Characteristic (ROC) curve was drawn for the predicted probabilities obtained from BLR analysis. The predictability of foramen magnum measurements in sexing of crania was 65.4% for transverse diameter and 86.5% for the anteroposterior diameter. For the area of foramen magnum that was calculated using the formula derived by Radinsky and Teixeria, the predicted probabilities were observed to be 81.6% and 82.2% respectively. When anteroposterior and transverse diameter were used together in BLR analysis the predictability of sex increased to 88%. However, considering the overlapping in the male and female values for the foramen magnum measurements it is suggested that its application in sex estimation should be restricted to cases where only a fragment of base of the skull is brought for examination. In such cases, the anteroposterior diameter and area of the foramen magnum can be employed as better tools for sexing the skulls than the transverse diameter of the foramen magnum.