Sex Estimation Through External Occipital Protuberance Morphology: A CT Scan Study in Northwest India

Objectives

This study aims to evaluate the types, prevalence, and forensic utility of external occipital protuberance (EOP) morphology for sex estimation in a Northwest Indian population using computed tomography (CT) imaging.

Materials and Methods

CT scan data of 331 adult individuals (167 males, 164 females), aged 18 to 75 years, were analyzed. EOP morphology was classified into three distinct types: Type 1, Type 2, and Type 3. Morphometric measurements—including total EOP length (TEOP) and angle at apex of EOP (AAEOP)—were obtained using the Radiant DICOM Viewer. Statistical analysis, including discriminant function analysis, was employed to assess the predictive accuracy of EOP features for sex estimation.

Results

The analysis revealed significant sexual dimorphism in EOP morphology. Type 1 was more frequent in females (33.8%), while Type 3 was more common in males (38.3%). Male individuals showed greater EOP thickness and more pronounced cranial landmarks such as the superior and inferior nuchal lines and the external occipital crest. Discriminant function analysis yielded an overall sex estimation accuracy of 89.4%, with higher classification rates in older age groups. Among the variables, TEOP and AAEOP were the most reliable predictors, achieving classification accuracies of 81.9% and 76.1%, respectively.

Conclusion

EOP morphology demonstrates clear sexual dimorphism and proves to be a reliable indicator for sex estimation in the studied Northwest Indian population. The high classification accuracy, particularly in older age groups, supports the integration of EOP-based assessment into forensic protocols. This study highlights the importance of population-specific data and encourages further research on cranial features in underrepresented regions to enhance forensic identification methods.