Age changes in bone mineralization, cortical thickness, and haversian canal area.

Age-related changes in femoral cortical bone were quantified in an age-graded series of human cadavers. Variables included in this study were cortical thickness, bone mineral content, cortical bone density, summed Haversian canal area, Haversian canal number, and mean Haversian canal area. Females showed significant (P less than 0.05) decreases in cortical thickness, bone mineral content, and cortical bone density when plotted against age. Males exhibited slight nonsignificant declines for cortical thickness, bone mineral content, and cortical bone density. Both males and females exhibited significant (P less than 0.05) age-related increases in summed Haversian canal area values and Haversian canal number. Females as a group were found to exhibit significantly (P less than 0.05) larger mean Haversian canal area values compared with males, but the male group exhibited more Haversian canals per unit area of cortical bone compared with females. Intercorrelations between the bone mineral index and summed Haversian canal area and between cortical bone density and summed Haversian canal area define the role of increasing Haversian canal number and mean canal size per unit area of cortical bone as a factor in the reduction of bone mass as a function of age. Partial correlations between the bone mass variables and the variables assessing Haversian canal size and number further support this argument.