Patterns of age-related cortical bone loss (osteoporosis) within the femoral diaphysis.

The rate and degree of cortical bone loss was examined at five sites along the femoral diaphysis in males and females aged 20 through 55+ from an archeologically excavated Amerindian population. Age-related remodeling within the diaphysis was evaluated using measures of cortical thickness, cross-sectional area, and diaphyseal diameter. The results tend to confirm previous studies indicating: 1. a high degree of association between endosteal bone loss and the aging process after the third decade of life; 2. that osteoporotic hone loss is both relatively and absolutely greater among females than among males, and; 3. that bone growth at the sub-periosteal surface continues through the decades studied in both sexes. This study found further that: 1. differential rates of cortical bone loss and associated remodeling are found within the femoral diaphysis, and; 2. these remodeling differences appear to be sex-specific. The reduction in cortical thickness and cross-sectional area was most apparent in the proximal one-third of the femoral diaphysis among the females, and in the distal one-third of the femoral diaphysis among the males. Cortical bone loss tended to be offset to varying degrees in both sexes by apposition at the sub-periosteal surface, which appeared to act as a compensatory factor bringing about an increase in diameter in those areas of the diaphysis where the greatest amount of endosteal resorption occurred.