Structural role of bone apatite in human femoral compacta.

Tensile and compressive strength of human femoral compacta have been shown to be related (P is greater than 0.005) to the average bone apatite crystallite length (D002) as determined by X-ray diffraction line breadth measurement. However, statistical variance of crystallite length was not sufficient to explain observed differences in mechanical properties, these differences being primarily due to variation in mineral density. Average bone apatite crystallite length was not found to change significantly with biological age (P=0.30) over the range 3 1/2 to 87 years. It is concluded that increased bone apatite crystallite length is detrimental to the structural role of the skeleton but that this is not a major factor in determining fracture incidence in the elderly.