Studies of skeletal remodeling in aging men.

Senile osteoporosis in the male skeleton was studied in midshaft cross-sections from the femur, humerus, and metacarpal of 42 white male cadavers, aged 37 to 96 years. The cortical area (AC) and polar moment of inertia (J) of each section were measured. Cortical porosity and haversian canal density were also measured as functions of position in the sections, and the sizes of osteons and haversian canals in the femur were studied. In addition, the density and cross-sectional geometry of the neck of the femur were determined in 10 subjects. Age-related increases in porosity at each skeletal site are compensated by concomitant increases in cross-sectional geometry. These increases in J and AC are limited, however, being reversed at age 80 in the femur and humerus, and at age 60 in the metacarpus. Intracortical porosity was found to be localized in each bone in ways consistent with Wolff's law. The number of haversian canals/mm2 increased with age, but the size of haversian canals did not. Osteon size decreased with age. Osteon distribution patterns in the femur were consistent with random rather than directed patterns of osteon placement.