Hideki Tsutsui

Corticosteroid Enhances the Experimental Induction of Osteonecrosis in Rabbits With Shwartzman Reaction

Bacterial endotoxic reactions can cause osteonecrosis in humans by disseminated intravascular coagulation. The authors first used a combination of the Shwartzman reaction and corticoid injections in rabbits to develop a new animal model of osteonecrosis. This model showed a significantly higher incidence and wider area of osteonecrosis in the femur and humerus than that found in rabbits with either Shwartzman reaction or steroid injection alone. Osteonecrosis was observed in several foci that were distributed from the diaphysis to the epiphysis in both bones. Histologically, the bone marrow cells underwent necrosis, whereas the bone trabeculae demonstrated either empty lacunae or pycnotic nuclei of osteocytes. Exogenous steroids appeared to potentiate the Shwartzman reaction and the magnitude of osteonecrosis, perhaps by increasing endothelial damage and hypercoagulability of those intraosseous and extraosseous vessels that subsequently thrombosed. This model may not only be useful in clarifying the etiology and early pathogenesis of human osteonecrosis after corticoid therapy, but also in designing Pharmaceuticals for prevention and early treatment.

Histopathologic alterations of retinacular vessels and osteonecrosis

To probe into the pathogenesis of osteonecrosis of the femoral head, the authors obtained 37 asymptomatic human femoral heads at autopsy; of these, 13 were cases of high dosage corticosteroid therapy (steroid group) and 24 were cases without steroid therapy (nonsteroid group). The steroid group included two asymptomatic cases of osteonecrosis incidentally recognized. These femoral heads then were studied histologically and morphometrically using 2-mm stepwise tissue sections of the whole femoral head and serial sections to examine the histopathologic alterations of superior retinacular arteries and veins in detail. There was no significant difference in the luminal stenotic rate of the superior retinacular arteries between the steroid and nonsteroid groups. However, the draining veins morphometrically were more stenotic or obliterated in the steroid group than were those in the non-steroid group. In fact, the number of stenotic veins was significantly greater in the steroid group. These findings indicate that the stenotic changes of the draining veins may participate in the development and progression of steroid induced osteonecrosis of the femoral head.