Ancestry evaluation from subtrochanteric shape of femur using Tallman and Winburn's Adjusted Platymeric Index: A validation study in the Northern Thai population

Abstract

Background: Ancestry estimation of unidentified human skeletons using metric parameters of bones other than the skull, such as the subtrochanteric shape of the femur, is a challenging method in cases with limited information from cranial examination. The results of multiple studies show that the subtrochanteric shape can differentiate Asian and non-Asian individuals. However, the cut-point of the platymeric index for subtrochanteric shape might need adjustment for each region or country for higher accuracy, due to interpopulation and intrapopulation variation. Objectives: This study aims to validate the cut-point adjusted for the Thai population suggested by Tallman and Winburn and observes the differences between each sex within the same population. Materials and methods: The researchers conduct the study by collecting and calculating multiple parameters (such as femoral subtrochanteric diameters and shape, and platymeric index) from 130 northern Thai individuals collected from the Chiang Mai University bone collection, then making comparisons with the traditional cut-point, and comparing these parameters between different populations and sex. Results: The results show that the accuracy of ancestry estimation is improved from 46.38% to 57.49%, using an adjusted cut-point. This study also notes that the platymeric index of the northern Thai samples is significantly higher (p<0.05) than the north-eastern samples recorded by Tallman and Winburn. Moreover, the index of the male Thai samples is significantly higher (p<0.05) than the female samples from the same bone collection. Conclusion: This study approves the use of the adjusted cut-point in the northern Thai region and indicates an intrapopulation variation and sexual dimorphism of subtrochanteric shape which might influence ancestry assessment.