Effects of steroids on femoral diaphyseal intramedullary circulation in rabbits.

We examined the effect of steroid treatment on the intraosseous femoral vasculature in rabbits, with particular emphasis on the morphologic changes in bone marrow sinusoids and central veins. Adult rabbits were divided into three treatment groups: group A, untreated control; group B, animals were treated with intramuscular injections of methylprednisolone acetate (4 mg/kg/week) for 4 weeks; and group C, rabbits which received injections for 8 weeks. Examination of the intraosseous femoral vasculature was performed using microangiography, scanning electron micrography using a corrosion cast method, and retrograde venography. Bone marrow sinusoids of group C were dilated and the network of anastomosed vessels was irregular compared with those of group A. Changes in group B were intermediate between the control rabbits and group C. Retrograde venography of the central vein showed an irregular course and frequent narrowing of the signal. There were no arterial changes in the steroid-treated groups. These findings indicate that steroid therapy does not induce arterial ischemia but rather intraosseous venous stasis extending from bone marrow sinusoids to the central veins. These changes are attributable to bulging or dilatation of sinusoids, a rise in intraosseous pressure, and reduced blood flow.