Technical note: A stereological analysis of the cross-sectional variability of the femoral osteon population

Unbiased selection of regions of interest (ROIs) and unbiased definition of histological structures are needed to improve the repeatability of microscopic methods for age at death determination and to reduce operator subjectivity. We present results obtained by selecting ROIs according to stereological principles on a sample of 28 femoral cross sections of Caucasoid males aged 20-89 years. A regular grid was overlaid on the cross section, and the ROIs were selected as close as possible to the periosteum in the anterior, lateral, and medial regions. The areas consisting of all intact secondary osteons plus fragments were outlined and osteon population density, percent osteon population, area, and perimeter were calculated using stereological methods and software. Overall, the analyses of intra- and inter-section variability showed no significant difference between the ROIs, i.e., the location within the cross section of the ROIs does not affect the outcome of the analyses. The individual variability was found to be higher in adults aged 30-55 years than in other age ranges. ranges.