Estimation of sex from sternal measurements in a Western Australian population

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In Australia, particularly Western Australia, there is a relative paucity of contemporary population-specific morphometric standards for the estimation of sex from unknown skeletal remains. This is largely a historical artefact from lacking, or poorly documented, repositories of human skeletons available for study. However, medical scans, e.g. MSCT (multislice spiral computed tomography) are an ingenious and practical alternative source for contemporary data. To that end, this study is a comprehensive analysis of sternal sexual dimorphism in a sample of modern Western Australian (WA) individuals with a main purpose to develop a series of statistically robust standards for the estimation of sex. The sample comprises thoracic MSCT scans, with a mean of 0.9 millimeter (mm) slice thickness, on 187 non-pathological sterna. Following 3D volume rendering, 10 anatomical landmarks were acquired using OsiriX(®) (version 3.9) and a total of 8 inter landmark linear measurements were calculated using Morph Db (an in-house developed database application). Measurements were analyzed using basic descriptive statistics and discriminant function analyses, with statistical analyses performed using SPSS 19.0. All measurements are sexually dimorphic and sex differences explain 9.8-47.4% of sample variance. The combined length of the manubrium and body, sternal body length, manubrium width, and corpus sterni width at first sternebra contribute significantly to sex discrimination and yield the smallest sex-biases. Cross-validated classification accuracies, i.e., univariate, stepwise and direct function, are 72.2-84.5%, with a sex bias of less than 5%. We conclude that the sternum is a reliable element for sex estimation among Western Australians.