The applications of three-dimensional computed tomography images of the greater sciatic notch for sex determination in forensic anthropology aspect in Thai population

Background: The identification of highly decomposed corpses or skeletons remains a significant challenge for forensic medical examiners. The pelvic bone, recognized for its reliability in sex determination, is frequently utilized through visual assessment as an initial step in such cases. However, the subjectivity of this method has prompted research into more accurate and objective approaches than traditional anatomical morphological evaluations. Objective: The research was aimed to identify practical osteometric parameters of the greater sciatic notch, measured using a postmortem computed tomographic (PMCT) program, that have significant differences between male and female adults and provide high accuracy for sex determination in the Thai population. In addition, equation with high accuracy for sex determination using discriminant function analysis (DFA) was also developed. Materials and methods: This study analyzed 385 Thai adults aged over 20, whose postmortem computed tomography (PMCT) scans included the hip region with an intact greater sciatic notch. The sample comprised 129 females and 256 males. The analyzed 6 osteometric parameters include two distances: PIIS-IS; the distance between the posterior inferior iliac spine (PIIS) and the ischial spine (IS), PIIS-SP; the distance between PIIS and Separating point (SP), a ratio of PIIS-SP to PIIS-IS (PIIS- SP/PIIS-IS), and three angles: Angle between planes passing PIIS and IS, and PIIS and DP (PIISA); Angle between planes passing PIIS and DP, and IS and DP (GSNA) and Posterior part when the GSNA is divided by DP-SP plane (GNSPA). Discriminant function analysis was used for data evaluation. Results: Three-dimensional measurements of the greater sciatic notch demonstrated high reliability, with intra- and inter-observer ICC values exceeding 0.8 (p<0.05). All five measurements and the ratio achieved over 92% accuracy in multivariate analysis for cross-validated cases. DFA confirmed the suitability of all parameters for inclusion in the discriminant equation, which provided thresholds for sex determination: D<-1.03 indicated male, D>2.04 indicated female, and intermediate values were indeterminate, accounting for 67.73% of population variance. Conclusion: This study demonstrates that all the selected measurements of the greater sciatic notch can effectively differentiate between male and female adults through the application of discriminant function with an overall accuracy of 92%.