Changes in the composition of the human femur during growth

Abstract

The human femus was analyzed at various stages of growth between 12 weeks'' gestation and 35 years. In dry fat-free cortical bone the percentage of N fell and that of collagen rose. The contribution of the collagen nitrogen to the total nitrogen had nearly reached its mature value by 25-28 weeks'' gestation. The calcium/ nitrogen ratio rose during prenatal growth but, during the first 9 months of post-natal life, it did not rise further and may have fallen. The contribution of the epiphyses to the weight of the wet bone fell during growth. The percentage of collagen nitrogen in the epiphyses increased relative to that of total nitrogen, but there was little increase in the percentage of Ca until 5-9 months after birth. The calcium/phosphorus ratio in the epiphyses rose to its adult value by 5-9 months of age. The effect of the epiphyses on the composition of the whole bone is discussed. The rises in the percentage of calcium and in the calcium/nitrogen ration in the whole bone were delayed during the first 2-4 1/2 months after birth. The calcium/nitrogen and calcium/collagen ratios of the non-epiphysial parts of the femur fell during the first 5-9 months after birth and rose-again during later growth. This fall was attributed to a decrease in the degree of calcification of the metaphyses.