Age and sex estimation from the human clavicle an investigation of traditional and novel methods

This study investigates skeletal maturation and sexual dimorphism in the human clavicle in the American population. Specifically, traditional methods of age and sex estimation were compared to novel approaches. Transition analysis, or probit regression, was used to study secular trends in epiphyseal union of the medial clavicle. A Bayesian approach was used to develop age-at-fusion ranges that are less sensitive to the effects of developmental outliers and age mimicry. Linear regression was used to evaluate the sexing accuracy of three commonly-used clavicular measurements and six newly developed measurements. Additionally, a statistical clavicle atlas was used to explore size and shape dimorphism. For the epiphyseal union study, clavicles from 1,289 individuals from cohorts spanning the 20th century were scored with two scoring systems. A simple 3-phase scoring system proved the least subjective, while retaining accuracy levels.Significant secular trends were apparent in the onset of skeletal maturation, with modern Americans transitioning to fusion approximately 4 years earlier than early 20th century Americans and 3.5 years earlier than Korean War era Americans. Consequently, the secular trend towards earlier maturation appears to have occurred primarily during the latter half of the 20th century. These results underscore the importance of using modern standards to estimate age in modern individuals. For the sexual dimorphism study, all analyses were performed on three dimensional models of CT scanned clavicles. Linear discriminant analysis was performed on nine computer-automated measurements from 1,414 clavicle models. Cross-validated accuracy rates of the best models hovered around 92%. Two new measurements of the lateral end proved to be useful sex estimators, whereas accuracy rates from the medial end were low.Additionally, sex-specific statistical atlases were used to visualize areas of highest dimorphism. A statistical treatment combining Principal Components Analysis (PCA) and Fisher's Discriminant Ratio (FDR) showed high magnitudes of curvature difference between males and females, particularly in the anterior and superior curvature of the midshaft and the posteriorly oriented curvature of the lateral end. The areas highlighted by the PCA-FDR method show promise as new sexing criteria for the human clavicle.