Performance of three mathematical models for estimating age-at-death from multiple indicators of the adult skeleton.

The mathematical method which will achieve the most accurate and precise age-at-death estimate from the adult skeleton is often debated. Some research promotes Bayesian analysis, which is widely considered better suited to the data construct of adult age-at-death distributions. Other research indicates that methods with less mathematical complexity produce equally accurate and precise age-at-death estimates. One of the advantages of Bayesian analysis is the ability to systematically combine multiple indicators, which is reported to improve the age-at-death estimate. Few comparisons exist between Bayesian analysis and less complex mathematical models when considering multiple skeletal indicators. This study aims to evaluate the performance of a Bayesian approach compared to a phase-based averaging method and linear regression analysis using multiple skeletal indicators. The three combination methods were constructed from age-at-death data collected from 330 adult skeletons contained in the Raymond A Dart and Pretoria Bone Collections in South Africa. These methods were tested and compared using a hold-out sample of 30 skeletons. As is frequently reported in literature, a balance between accuracy and precision was difficult to obtain from the three selected methods. However, the averaging and regression analysis methods outperformed the Bayesian approach in both accuracy and precision. Nevertheless, each method may be suited to its own unique situation-averaging to inform first impressions, multiple linear regression to achieve statistically defensible accuracies and precisions and Bayesian analysis to allow for cases where category adjustments or missing indicators are necessary.

Facial approximations: Characteristics of the eye in a South African sample.

Although guidelines for facial approximations, including those for the eye, are in use in South Africa, limited data on African populations exist to confirm its validity. As precise placement of the eyes in facial approximations is of importance for facial recognition, this study tested established guidelines by measuring specific instrumental dimensions. Forty-nine cadavers from the Sefako Makgatho Health Sciences University and the University of Pretoria were dissected to determine the position of the canthi and the size and position of the eyeball in the orbit. Thirty cone beam computer tomography scans and 30 computer tomography scans from the Oral and Dental and Steve Biko Hospitals respectively were used to determine the size of the eyeball. Results from this study were compared to the published guidelines. The most prominent discrepancies included a more rectangular shape of the orbit, an oval shaped eyeball and a different position of the canthi. In African faces, the medial canthus was found to be located higher than the lateral canthus. The distance between the endocanthion and superior orbital margin was 17.7mm and the exocanthion and superior orbital margin 19.5mm. Inter-population differences may have an effect on facial approximations and its accuracy as is often demonstrated in practice. The findings of this study should be taken into consideration when designing population specific guidelines for reconstruction of the eye in South Africans of African ancestry.

The changing face of tuberculosis: trends in tuberculosis-associated skeletal changes.

Tuberculosis remains a major health problem in many areas of the world. Previous research suggested that the frequency of bone lesions has decreased in the modern (but pre-antibiotic) period, and that the predominantly spinal involvement have changed to affect other parts of the skeleton, in particular ribs. The purpose of this study was to investigate whether bone lesions associated with TB became more or less common in the post-antibiotic period, and if the pattern of skeletal involvement has changed. The skeletons of 147 individuals from South Africa who died from TB were assessed. These were divided into three groups - those dying before 1950 and presumed to have had no antibiotic intervention (n = 52); those dying between 1950 and 1985 presumed to have been treated with antibiotics (n = 34); and those dying after 1985 where co-infection with HIV and drug-resistant disease emerged (n = 61). Overall, 33.3% of all individuals showed signs that could be associated with TB, with corresponding figures in each of the three groups being 21.1%, 38.2% and 41.0%. The increase from group 1 to 3 was statistically significant. Rib lesions are becoming more common, while spinal lesions are decreasing. It may be suggested that patients are surviving for longer due to antibiotic treatment, allowing more time for the development of lesions.