Quantitative observations on mineralized and non-mineralized bone in the iliac crest.

The amounts of mineralized bone and osteoid in thin undecalcified sections of iliac crest have been measured in 68 control subjects at necropsy using a point-counting method. The effect of varying the site selected for quantitative study on the value obtained for total bone mass has been investigated in decalcified sections of iliac crest. The total bone mass shows individual variation within a fairly constant range with a mean of 22.7 +/- 0.5% up to the age of 50 years and then progressively falls to a mean of 15.5 +/- 1.1% for individuals aged > 50 years. Some of the lowest values in the range 5.5 to 16.4 (mean 8.9 +/- 1.9%) were observed in elderly women in the seventh to ninth decades. It is concluded that so-called senile osteoporosis is usually a manifestation of a normal aging process. In controls osteoid accounts for only about 0.1% of the area measured and for a maximum of 1.8% of bone with a mean mineralization of 99.5%. Osteoid is patchily distributed and the maximum number of birefringent lamellae in any seam is four. The results of quantitative histology carried out in different parts of the iliac crest indicate that there are variations with the distance of the site from the anterior superior spine and its depth below the crest surface. The importance of this in relation to the site and size of iliac crest biopsies used for quantitative histology is discussed. There is a significant correlation between the values for total bone mass when estimated by the point-counting technique in undecalcified sections and by a volumetric method using blocks of bone.