Sexual Dimorphism From Third Cervical Vertebra (c3) On Lateral Cervical Radiograph: A 2-dimensional Geometric Morphometric Approach

Sex identification is essential for the establishment of an accurate biological profile from skeletal remains in forensic anthropology. Conventional method using calipers is time-consuming and associated with a high margin of error especially in the case of highly fragmented skeletal remains. Geometric morphometric method is an approach which utilizes qualitative and quantitative description of biological forms according to geometric definitions of their shape. This study aimed to determine sexual dimorphism of third cervical (C3) vertebra on the lateral cervical radiograph by geometric morphometric method. Lateral cervical radiographs of 432 samples comprising of 262 males and 170 females of known individuals were retrieved retrospectively. The samples were adult Malaysian population aged from 20 to 60 years old. Eleven 2-dimensional (2D) landmarks were applied on the digitalized radiographs by TPSDig2 (Version 2.31) software. Geometric morphometric analysis was performed by MorphoJ software. Procrustes ANOVA showed that centroid size and shape are significantly different with p<0.001. Discriminant function analysis (DFA) showed 70% classification accuracy, with identification accuracy of 70.6% for males and 70.0% for females. There were significant differences between sex in the height of vertebral body, length of the superior articular process as well as length of the superior part of spinous process of C3 (p<0.05; Independent t-test). In conclusion, sexual dimorphism demonstrated in the C3 vertebra confirms the utilization of 2D geometric morphometric as one of the methods for sex estimation. To the best of our knowledge, this is the first study to report such findings among Malaysian population.