Sexual Dimorphism and Population-Specific Sex Estimation Equations Using Morphometric Analysis of Dry Lumbar Vertebrae in a Northeastern Thais

Sex estimation from skeletal remains, particularly incomplete or fragmented ones, is crucial for forensic anthropology.This study aimed to investigate the morphometric characteristics of the lumbar vertebrae and their potential for sex estimation in the Northeastern Thai population.A cross-sectional study was conducted using 1000 identified dry lumbar vertebrae (L1-L5) collected in the Unit of Human Bone Warehouse for Research, Department of Anatomy, Faculty of Medicine, Khon Kaen University, Thailand.Eight morphometric parameters were measured using a digital Vernier caliper.The independent t-test and discriminant function analysis were performed to evaluate sexual dimorphism and generate equations.The results showed that most parameters on all lumbar levels of males were significantly greater than those of females (p < 0.05).Discriminant function analysis revealed that L2 had the strongest association between the discriminant function and sex groups.The correct classification rates determined by sex estimation equations ranged from 77.80 % to 85.00 %.Interestingly, the highest accuracy rate was achieved by the equation for L1 (85.00 %).Among all parameters in both males and females, the width of the pedicle isthmus and the distance from the junction of the superior facet and transverse process to the anterior cortex on the right side at L1 were systematically selected to be used in the equation of sex classification for the highest correct classification rate.This present study also attempted to compare sex estimation accuracy among populations as previously documented and showed that the upper lumbar vertebrae had higher reliability.These findings have contributed to the knowledge of population-specific sex estimation methods for applying dry lumbar vertebrae as a reliable skeletal element for sex determination in forensic contexts.