A new landmark for measuring the Ischium-Pubis index for sex determination by using three-dimensional models of South Korean population

The Ischium-pubis index (IPI) is one of the parameters of sex determination using the hip bone. IPI is defined as the percentage of the pubis length to the ischium length. On dry bones, the combined starting point of the lengths of the pubis and ischium is in the acetabulum. In this study, we evaluated the accuracy of IPI determination by using three-dimensional computational models. We compared the accuracy of three acetabular landmarks: the traditional acetabulum notch, the deepest point of the acetabulum and the point on the superior acetabulum border. The deepest point of the acetabulum was newly defined to facilitate the computational measurement. One-hundred models reconstructed from computed tomography scans of Korean adult cadavers were measured for the pubic and ischium length. After computer-assisted landmark indication procedure on software that enables three-dimensional model handling, measurements were automatically calculated. In the Korean adult population, measurements involving the deepest point of the acetabulum have shown the highest accuracy, 91%. We compared our results with those of the former reports on pubis length, ischium length, and IPI.