Abstract
1. A detailed study of density variations with age in cortical bone samples from different areas of the femoral diaphysis has been carried out.
2. Bone of relatively high density and, conversely, of low density was found to have a spiral pattern along the bone shaft.
3. Moving distally along the femoral shaft there was a transposition of the greatest density from the anterior to the posterior aspect.
4. In the erect body posture the femoral inclination is such that areas of denser bone might be expected to be aligned vertically because of the weight-bearing characteristics of the femur.
5. Most areas of the cortex tended to decrease in density after the age of fifty, the less dense areas changing more than those with an initial high density. Thus, osteoporosis tended not only to maintain but to accentuate the spiral pattern of density distribution by increasing the difference between dense and less dense bone.
6. In the distal region of the diaphysis bone resorption was greatest anteriorly but hardly affected the posterior aspect. A densitometric comparison between these two sites provided a clear indication of the effect of osteoporosis.
