Quantitative radiology: radiogrammetry of cortical bone

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Abstract
There is a large variability in amount of bone [2nd metacarpal] within 1 age and sex group which is partly due to skeletal size differences. The relative indices which were introduced to correct skeletal size differences, are insufficient since skeletal size differences still exist. The variability is reduced when the data are divided into strata of skeletal size. Since cortical area shows the best correlation with outer diameter within each age group and since cortical area represents best the ash content of the bones, the values of this index are most suited to be grouped according to outer diameter. In differentiating pathological from physiological bone loss, this procedure is an improvement on the previously published indices of amount of bone. When comparing different populations, this method has advantages since skeletal size differences are eliminated. Comparing 7 populations it was found that populations living in the USA have more bone for a given skeletal size than populations in Europe or Nigeria. Bone loss with age is a general phenomenon but differences in rate of loss are observed between the sexes and between ethnic different populations. The decrease of bone mass is faster after the age of 50 yr in woman than in men. Blacks living in the USA loose bone with age than whites. Radiogrammetry of cortical bone in groups gives useful information on bone remodelling during aging and in pathological conditions. At an individual level, it is difficult to evaluate changes on a short term basis with radiogrammetry. Radiogrammetry of cortical bone is a simple and reproducible method which measures bone mass indirectly. Changes in cortical width show a high degree of correlation with the changes in mass of cortical bones but trabecular bone is not measured. This is a serious handicap, since most of the metabolic diseases of the skeleton affect trabecular bone to a greater extent than cortical.