Determination of Sexual Dimorphism of the Human Sacrum Based on Receiver Operating Characteristic Curve Analysis of Morphometric Parameters

Background Sex estimation of unidentified incomplete skeletons poses a challenge to paleoanthropologists and forensic experts. The sacrum is a part of the axial skeleton and contributes to the formation of the pelvic girdle. It is a significant bone for the identification of the sex in the human skeletal system due to associated functional differences of the pelvic bones in males and females. However, there is a lack of cognizance of different morphometric parameters of the sacrum which may be crucial for determining sex, particularly when a part of the bone is available. This study aimed to recognize the best morphometric parameters for the identification of the sex of the sacrum even when fragmented bones were available and compare the various parameters for sexual dimorphism in different populations. Methodology The study was conducted on 110 dry adult human sacra in the anatomy department. Out of these, 42 sacra were female and 68 were male. Morphometric measurements were performed with the help of a digital vernier caliper. Statistical analysis was performed using SPSS version 17.0 (SPSS Inc., Chicago, IL, USA). Morphometric measurements of male and female sacra were compared using Student’s t-test. The receiver operating characteristic (ROC) curve analysis was performed to establish the most appropriate cut-off values for each parameter. Results The mean sacral length measured from the promontory to the apex of the sacrum was higher in males compared to females (p < 0.001), whereas the sacral index was higher in female sacra in comparison to male sacra (p < 0.001). Furthermore, the mean height of the first posterior sacral foramina (PSF) was higher in male sacra bilaterally (p < 0.05). On ROC analysis, the area under the curve was 0.994 for the sacral index and 0.862 for the sacral length. Conclusions In this study, the sacral index was noted to be the most important morphometric parameter for the identification of the sex of the sacra. Additionally, the height of the S2 body, the height of the first anterior sacral foramina, and the height of the first PSF can be contemplated with an accuracy of 60-70% if only a part of the sacrum is available for determining the sex. Hence, this study emphasizes the significance of morphometric parameters of the sacrum in the determination of sex, especially in forensic cases when the skull and pelvis are fragmented or unavailable.