[Lead deposits in bone--the roentgen picture as a demonstration method?]

Current concepts concerning the deposition, distribution and radiological demonstration of lead in the skeleton were investigated in five series of rats; some of these were young and others more than a year old. 10 mg of lead acetate/kg body weight were administered over a period of five to 41 days, giving a minimum of 8.4 mg and maximum of 40.4 mg of lead. A comparable control group was given similar amounts of sodium acetate. The distribution and concentration of lead in the femur was determined by the use of 210Pb. Contact autoradiographs showed band-shaped lead accumulation in the endosteal and periosteal growth regions. The degree of darkening depended on the amount of lead administered and permitted a rather coarse quantitative relationship to be drawn. Measurements of radioactivity produced similar distribution patterns. The relationship of lead concentration of epi- and metaphysis to the diaphysis averaged 2:1. The factor mainly responsible for lead deposition depended on the metabolic potential of the tissue, which itself depends largely on the growth regions. Radiologically, there was definite evidence of demineralization in the areas of lead deposition; this could be confirmed histologically by lack of trabeculae, thinning of the cortex and destruction of bone matrix. Despite its much greater absorption co-efficient, the tiny quantities of lead, compared with the bone mass (even in the highest concentrations in our experiments) cannot be detected radiologically. Biophysical calculations have been made which indicate that similar conditions occur in man. Radiological examination of the skeleton, which is used as a screening method for chronic lead poisoning, is not suitable for this purpose.