Sex determination by the length ratio of metacarpals and phalanges: X-ray study on Iranian population

Background: In forensic anthropological identification, we usually use body remains. Accurate sex estimation from these remains is very important and needs the knowledge of specific population standards of that area. Sometimes, human remains are damaged by environmental circumstances. So, we must examine single bones for sex estimation. One of the relatively resistant bones to environmental conditions are hand bones. Specific hand phalanges and metacarpals have significantly different dimensions in two sexes depending to each population and can be a helpful tool to estimate the gender of individuals. The aim of this study was to investigate the possibility of estimating gender using phalanges and metacarpals dimensions in Iranian people. Methods: This prospective study was conducted on the X-ray images of adult people hands between the months of March and September 2017. They referred to Shafayahyaian Hospital, the educational and referral center of orthopedic disease of Iran University of Medical Sciences, in Iran. 200 adult persons (100 male and 100 female) without any background of specific disease, entered in our study. In each case, the length of D: distal phalanx, M: middle phalanx, P: proximal phalanx, MC: metacarpal, Fl: finger length, and T: total (Distal phalanx+middle phalanx+proximal phalanx+soft tissue of the finger tip) were measured in millimeter and reported in ratio. All analyses were done using SPSS software, version 20 (SPSS Inc., Chicago, IL, USA). Results: Student t-test showed that many ratios were significantly different between two genders. It is concluded that the length ratio of metacarpals and phalanges could be used for sex determination. The most valuable ratios were FL1/FL3 and MC4/MC5. Multivariate logistic regression test reported an equation by which the gender is predictable. Z= 5.856+ -3.904 X FL1/FL3+ -1.865 X MC4/MC5. Conclusion: If “Z=0”, the gender is male and if “Z=1”, it is female without any doubt. In our knowledge, this study provides the first population sex estimation formulae from the hand bones in Iranian population. However, we need further studies in larger groups to use this equation for sex determination in forensic contexts.