[Scanning electron microscopic observation of microvascular cast changes of bone following rigid limb immobilization]

This paper reported the results of scanning electron microscopic observation of microvascular cast changes of tibia following long cast immobilization of lower extremity. Beginning from 10 days after immobilization, the diameter of microvessels, particularly capillaries and sinusoids system in bone marrow, displayed severalfold enlargement compared with the control side. The changes became more obvious at 20 days. The number of sinusoids increased whereas the degree of dilatation declined at 40 days. The vessels within the epiphyseal region also showed more intense dilatation, growth of sinusoid-like structure and proliferation of sinusoidal and capillary system in marrow at 60 to 80 days. Similar changes in the cortical bone emerged as well at 80 days. The above-mentioned changes decreased at 100 days. These results pointed out that the pump effect of muscle on the blood flow in bone almost disappeared completely and disturbance of intraosseous venous drainage occurred. Under the condition of increased but unbalanced bone metabolism and turnover, the intraosseous microvascular system exhibited the described changes. Thus the total bone blood volume and the total bone blood flow increased.