A Preliminary Study Using Visual Assessment of Variation in Proximal Ulnar Morphology: Implications for Sex, Age, and Population Estimation

Abstract

The purpose of this preliminary study was twofold: (1) to examine the morphology of the proximal ulna by way of visual assessment (i.e., morphoscopic analysis) in order to gauge any variability between the sexes, adult ages and populations (African American and European American) and (2) to explore the possibility of utilizing a morphoscopic method in mass grave or mass disaster field settings where quantitative approaches would be prohibitive due to time and equipment constraints. The proximal ulna is an area of interest because it forms the elbow joint along with the proximal radius and distal humerus. And, whereas joints are areas of the skeleton that show sexual dimorphism as well as age-related and or biomechanical changes such as osteoarthritis, it was hypothesized that shape differences exist between females and males, and young, middle and older adult age groups, though perhaps not between populations (i.e., African American and European American), since most population differences are found in the skull and femur. This study was undertaken as well because of the paucity of information on ulnar variation of this nature in the published literature. In this study, proximal ulnar morphology was largely characterized by a visual evaluation of torsion. A method was developed to assess this torsion, and the morphological data were collected for right and left ulnae from 64 individuals (n=128), aged 22 to 101 years, from the Robert J. Terry Skeletal Collection, Smithsonian Institution, National Museum of Natural History. Gross observations of raw data and results of certain statistical tests indicated that proximal ulnar morphology varied by sex and population; but, no clear distinctions among adult age groups could be determined. Because of small sample sizes, no definitive conclusions were drawn. Further testing on larger sample sizes is recommended. This study contributes novel information about proximal ulnar morphological variation, which, to date, has received little attention in osteological research.