Amy Beresheim

This study examines the influence of human adult body size and bone mass on cortical bone histomorphometry, and explores microstructural variation in mid-thoracic ribs. The sample consists of 213 individuals (n female = 82, n male = 131, mean age-at-death = 47.96 AE 15.71 years) from the Kirsten Skeletal Collection, Stellenbosch University, South Africa. Maximum femur length and femur maximum head diameter are used as proxies for height and weight; total cross-sectional area, endosteal area, and cortical area are used to derive measures of bone mass. Histomorphometric variables include osteon population density (OPD) and osteon area (On.Ar). Partial correlations, controlling for age, test for significant relationships among variables. A hierarchical regression model is used to determine unique variable contributions to On.Ar and OPD. Body size measurements do not correlate with either bone mass or histomorphometric variables, suggesting that size-standardization may not be necessary in studies of rib bone microstructure. Age is the most significant factor affecting OPD, while OPD is the best predictor of On.Ar. These findings suggest that age-related secondary osteon crowding affects osteon geometry. Understanding the biological mechanisms that direct bone remodeling and determine microstruc-tural variation is essential for interpreting histological data. Anat Rec, 2018.

Objectives: Normal human bone tissue changes predictably as adults get older, but substantial variability in pattern and pace remains unexplained. Information is needed regarding the characteristics of histological variables across diverse human populations. Methods: Undecalcified thin sections from mid-thoracic ribs of 213 skeletons (138 M, 75 F, 17–82 years, mean age 48 years), are used to explore the efficacy of an established age-at-death estimation method and methodological approach (Cho et al.: J Forensic Sci 47 (2002) 12-18) and expand on it. The ribs are an age-balanced sample taken from skeletonized cadavers collected from 1967 to 1999 in South Africa, each with recorded sex, age, cause of death and government-defined population group (129 " Colored, " 49 " Black, " 35 " White "). Results: The Ethnicity Unknown equation performs better than those developed for European-Americans and African-Americans, in terms of accuracy and bias. A new equation based solely on the study sample does not improve accuracy. Osteon population densities (OPD) show predicted values, yet secondary osteon areas (On.Ar) are smaller than expected for non-Black subgroups. Relative cortical area (Ct.Ar/Tt.Ar) is low among non-Whites. Conclusions: Results from this highly diverse sample show that population-specific equations do not increase estimate precision. While within the published range of error for the method (624.44 years), results demonstrate a systematic under-aging of young adults and over-aging of older adults. The regression approach is inappropriate. The field needs fresh approaches to statistical treatment and to factors behind cortical bone remodeling. Am J Phys