Variation in cortical bone histology within the human femur and its impact on estimating age at death

Histological methods for the estimation of age at death using cortical bone are based on the evaluation of microstructural changes over time. Since histological analysis is a destructive method, most techniques attempt to limit the amount of cortical bone needed for analysis. Sample location, however, can have a significant effect on the accuracy of these methods. Furthermore, research demonstrates that both intersection and intrasection variation is present at the midshaft of the femur, which is the primary location for estimating age at death in humans. This research determines the extent of regional variation within the adult human femur and its effect on age estimation. Secondary osteon lamellae and Haversian canal ratio and cortical thickness were quantified. Thompson's All Males Left Femur regression equation was used to estimate age. Results show that significant regional variation occurs in the estimated ages derived from the posterior aspect of the femoral shaft and significant intrasection variation occurs in age estimates from the mid and mid-distal cross-sections. Thus, the inter and intrasection variation that occurs in bone remodeling within the femoral cortex has the potential to produce significant differences amongst age estimates taken from various femoral diaphyseal locations compared to the age estimated from the standard location used in Thompson's core method (1978). The results indicate that the use of this histological method is dependant on the ability to correctly identify the four anatomical locations, but the extracted core used for age estimation is not necessarily confined to the anterior midshaft.