In order to quantify age-related changes in the structural integrity of the human femur, data from four sites on each of 37 left femoral shafts was analyzed. Measurements of bone specific gravity were converted to estimates of material strength in bending using empirical relations reported in the literature. Structural strength was determined by measuring cross-sectional moments of inertia. These data were then used to calculate the bending strength of the femoral shaft as functions of position, age, and sex.
The results indicate that the material strength of femoral bone decreases with age equally in males and females. In males this decrease is compensated by increases in section modulus so that the overall strength of the shaft remains constant. In females, the section modulus decreases with age, exacerbating the effects of material weakness and leading to greatly reduced femoral strength in old age. These results are supported by related experimental evidence from the literature. Additional useful engineering data on the structural properties of the femoral shaft are also reported.