This research assesses histological age estimation using the anterior femur and explores the biological limitations of bone turnover as an age indicator.
This study found that histological analysis of the anterior femur provides reliable age estimates at death. The described regression model is most accurate for individuals over 50 years old. The procedures tested in this research will improve the accuracy of estimating age for older adults. The study sample included femur cross-sections from 319 individuals (169 males and 150 females) whose age at death was known. The topographic sampling method was used to assess 10 columns from the periosteal to the endosteal cortex, which is located at the anterior femur midshaft. Using a Merz counting reticule at 200x magnification, 50 percent of the microscopic fields were assessed in each column by alternating fields. This sampling strategy accounted for 95 percent of the remodeling variability within the anterior cross-section. Osteon areas and cortical widths were calculated using imaging software. Statistical analyses were performed in SPSS 19 in order to examine the relationship of the cortical bone histomorphometrics to sex and age. Stepwise linear regression was used to develop the age prediction equations. Two variables - fragmentary osteon density and mean osteonal cross-sectional area - require log transformation to meet normality requirements. Analysis of observer error was performed using several procedures for evaluating method repeatability. Pearson correlations showed moderate and strong relationships with age for all collected variables except intact secondary osteon density. Due to this finding, constituent variables for osteon population density should remain separate in the regression model. One-way ANOVA and ANCOVA analyses found that the variables, with the exclusion of intact secondary osteon density, show some significant sex differences at the 0.05 level. The described method has several advantages over previous methods. 27 tables, 13 figures, 75 references, and a listing of the means of dissemination of research results