Age-related mineralization heterogeneity changes in trabecular bone of the proximal femur

Although there is extensive documentation in the literature regarding the importance of trabecular bone for proximal femoral integrity and fracture resistance, there remain gaps in our understanding of the basic mineral changes that may occur in trabecular bone attributable to aging. It is unclear what age-related changes take place in the trabecular bone of the proximal femur, a common fracture site in the elderly. It has been suggested that some explanation for conflicting reports on cancellous bone may be found at a microscopic level. The goal of this study was to document age-related changes in micromineralization in the proximal femur of Caucasian females using backscattered electron imaging technology. Proximal femurs were obtained from 11 young and 11 elderly females. Sections of bone from the superior and inferior neck and superior and inferior trochanter were analyzed in a scanning electron microscope using the backscatter technique to determine ash percent. Mean ash percent did not change with age in any of the four regions (P > 0.05). However, while the mean ash percent did not change, there was a dramatic increase in variability elderly age group and loss of mineral heterogeneity. This indicates that there are subpopulations with higher or lower ash percents than the mean in the elderly study group in this investigation. While variance changed dramatically, variance within individuals did not change significantly with age (P > 0.05). The results of this study suggest that changes in micromineralization may occur within an individual, adding a possible new dimension to our understanding of fracture risk in the elderly. Future studies should examine a longer population base to confirm this observation.