Standardizing ordinal subadult age indicators: Testing for observer agreement and consistency across modalities.

Skeletal and dental data for subadult analyses obtained from dry bones or various types of medical images, such as computed tomography (CT) scans or conventional radiographs/x-rays, should be consistent and repeatable to ensure method applicability across modalities and support combining study samples. The present study evaluates observer agreement of epiphyseal fusion and dental development stages obtained on CT scans of a U.S. sample and the consistency of epiphyseal fusion stages between CT scans and projected scan radiographs/scout images (U.S. CT sample), and between dry bones and conventional x-rays (Colombian osteological sample). Results show that both intra- and interobserver agreements of scores on CT scans were high (intra: mean Cohen's kappa=0.757-0.939, inter: mean Cohen's kappa=0.773-0.836). Agreements were lower for dental data (intra: mean Cohen's kappa=0.757, inter: mean Cohen's kappa=0.773-0.0.820) compared to epiphyseal fusion data (intra: mean Cohen's kappa=0.939, inter: mean Cohen's kappa=0.807-0.836). Consistency of epiphyseal fusion stages was higher between dry bones and conventional x-rays than between CT scans and scout images (mean Cohen's kappa=0.708-0.824 and 0.726-0.738, respectively). Differences rarely surpassed a one-stage value between observers or modalities. The complexity of some ossification patterns and superimposition had a greater negative impact on agreement and consistency rates than observer experience. Results suggest ordinal subadult skeletal data can be collected and combined across modalities.

A morphometric analysis of prognathism and evaluation of the gnathic index in modern humans.

Subnasal prognathism is a morphological feature often described in studies of paleoanthropology, bioarchaeology, and forensic anthropology. This trait is commonly quantified using the gnathic index, which compares basion-prosthion and basion-nasion lengths. This study used geometric morphometrics to assess whether the gnathic index is a reliable indicator of subnasal prognathism and to explore the effects of sex, population, and allometry on this trait. Nineteen craniofacial landmarks were collected from three-dimensional cranial surface scans of 192 individuals across five population groups. Generalized Procrustes analysis and principal components analysis were employed to identify shape components related to changes in subnasal prognathism, comparing component scores to gnathic index values. M/ANOVAs were used to determine the effects of sex and population on prognathism, and linear regression served to assess static allometry. The gnathic index was significantly correlated with PCs 1 and 3, which appeared to capture prognathic shape change, but also with PCs 2 and 6, which reflected other craniofacial shape changes. Population differences in levels of prognathism were identified, but no significant effects of sex or allometry were found. The results show that, although the gnathic index correlates with prognathic shape variation, it is also influenced by other variables, such as the relative position of basion. In this sense, the gnathic index serves to illustrate the shortcomings of linear measurement analysis as compared to landmark configurations. Further, the results demonstrate that subnasal prognathism is a complex feature in need of redefinition.