Sex estimation based on the anthropometric measurements of thyroid cartilage using discriminant analysis

Background The morphometric analysis of the individual bones of the human skeleton can be used to estimate the sex of unidentified corpses. Our aims were as follows: to test whether thyroid cartilage can be used for forensic purposes as a predictor of biological sex; to establish the level of sexual dimorphism of the thyroid cartilage in a sample of adult subjects from a population of European Russia; and to test the accuracy of the morphometric parameters obtained from the thyroid cartilage. Results The thyroid cartilage from 100 adults of known age (50 males and 50 females) was obtained during forensic examination; morphometric tests were conducted using Vernier Digital ROKTOOLS ABS DIN 862 0-200/6 inch with measurement accuracy ± 0.01 mm. The measured parameters were N = 31 for each subject. Intra- and inter-observer reproducibility was tested. Multivariate statistical analysis was applied to the measurements. To check the data set for normal distribution, the Kolmogorov-Smirnov test was used. Finally, to estimate the sex of the observed individuals, a stepwise discriminant analysis was conducted, using the Wilks’ lambda selection method. The most significant parameters were the outer distance between bases of inferior horn; the inner distance between distal ends of inferior horns; distance between distal ends of left superior and inferior horns; left superior horn length (distance between left superior horn distal end and base); distance between superior and inferior notches; thyroid angle; left lamina height (vertical line along left lamina middle); horizontal distance between anterior intermedium line and the right lamina posterior edge; distance between inferior thyroid notch and line connecting left and right thyroid laminae; and left superior horn thickness at mid-line. The stepwise discriminant analysis resulted in an equation with ten parameters. Conclusions The results of the current study indicated that in the European Russian population, the equation obtained in the stepwise discriminant analysis makes it possible to predict sex with a probability of 100% on the validation set. On the test set, the resultant accuracy was 100% for females and 100% for males. Our findings confirm the scientific evidence that the thyroid cartilage has a pronounced sexual dimorphism.