Sex estimation using the second cervical vertebra: a morphometric analysis in a documented Portuguese skeletal sample

Biological sex estimation is one of the main parameters required in the construction of a biological profile of an unknown deceased person. In corpses in an advanced state of decomposition, skeletonized or severely mutilated, bone analysis may provide the only way to access biological sex. Although the hip bones are the most dimorphic and useful bones for sex estimation, they are often badly preserved and/or fragmented or may not even be present in some cases. For that reason, it is necessary to develop sex estimation methods based on bones less dimorphic. In this study, 13 dimensions of the second cervical vertebra were measured in order to quantify sex-related variation and to generate a simple predictive model based on logistic regression analysis. For logistic regression fitting, 190 individuals from the Coimbra Identified Skeletal Collection were used as a training sample. The resulting model was also evaluated in an independent test sample composed of 47 individuals from the Identified Skeletal Collection of the 21st Century (University of Coimbra). The developed logistic regression model correctly estimated known sex in 86.7 to 89.7 % of the cases. The second cervical vertebra demonstrated to be a useful alternative for sex estimation when other skeletal elements are not available or suitable for analysis. This method seems promising but more reliability studies are required for a more robust validation.