Findings of the second cervical vertebra indices in males and females showed that in all cases, the dimensions of collected indices from the vertebrae of males are greater than that of females, but in 9 out of 15 indices, this difference was statistically significant. These 9 indices were including AMA, LMA, DSD, DMFS, CMFS, LMFS, AMD, DSMC, and LMFI. Among the 9 variables which had a significant correlation with sex, 2 variables of LMSF and AMA considered as the independent predictive of sex with an odds ratio of 2 and 1.47, respectively and they had diagnostic accuracy of 81.4%. This indicates the presence of sexual dimorphism in the measurements of the Iranian vertebrae. The most significant mean difference was found in the linear dimensions of the second vertebra of LMA and AMA between the two sexes.
In a study on the cervical vertebra of skeletal specimens, the 15 linear indices of cervical vertebra were examined, which were largely in accordance with the metric dimensions measured in our study [1]. The size of the examined dimensions was slightly different from the dimensions of our study [1]. In all cases, dimensions were higher in males, but the LMA and DSMC indices had the most difference between the two sexes [1]. In their study, four indices including CMA, LMA, LMFSD, and DSMC were independent predictors of sex with a predictive accuracy of 87% between sexes [1]. In another study by Marlow et al., 9 indices of cervical vertebra dimensions were measured, some of these dimensions are similar to those measured in our study. All of these dimensions in males were significantly larger than females [3]. Of these dimensions, XSL, SFS, SFT, LVF, and XDH were sex-independent predictors that provided a total of 77% sex diagnostic accuracy [3].
In comparison of our study with the above-mentioned studies on second cervical vertebral indices, a few points were noted: First, in all of the mentioned cases, as well as our study, the upper fast was considered as an independent predictor of sex; Second, the diagnostic accuracy of sex determination in different dimensions was significant in all cases; Third, although all dimensions were larger in males than females, but the mean difference was low even in significant indices suggesting that it is essential to be more focused on practical points of these low rates of mean difference.
In terms of a seventh cervical vertebra of current study, the 10 linear indices were investigated. All dimensions in this vertebra were higher in males than in females, and statistically significant correlations with sex were observed in 4 indices including the LSF, LIVB, WIVB, and LSP. Of these four indices, only two variables LIVB and LSP were independent sex predictors. The two variables had a diagnostic accuracy of 78.6%. In confirmation of the findings of the current study, assessment of the seventh cervical vertebra dimensions amongst the three groups of whites, blacks, and South Africa tribes showed that the anterior posterior’s length, width and height of the vertebra were greater in males than females [26].
Studies have shown that the dimensions of the cervical vertebrae are correlated with skeletal dimensions and the larger dimensions of the skeletal vertebrae in males are attributed to the larger body size of them [27]. However, in this study, both the dimensions of the vertebral bodies and their posterior pectorals were statistically significant with sex. In the present study, relationships between age and dimensions of the vertebrae were observed. Correlation between age and cervical vertebral dimensions was mostly positive and weak. Considering the age range of the population was under the 69 year, the possibility of degenerative changes in the vertebra should be considered, which affects the dimensions of the vertebra. Other studies have shown the relationship between age and dimensions of cervical vertebra [4, 28].
All dimensions measured for the second and seventh cervical vertebrae were higher in men than women in this study. The height of the second vertebra and the transverse diameter of the upper fast were independent sex predictors, with an accuracy of 81.4%. In the seventh vertebra, the anterior-posterior of the vertebral body and the posterior length of the vertebra were independent predictors of sex, which had an accuracy of 78.6% in sex determination. The results of this study showed a high accuracy of cervical vertebral dimensions in sex determination of skeletal remains in the Iranian population.