RESUMO
Objective To study the mechanism of steroid induced necrosis of femoral head. Methods The cell experiment of effect of dexamethasone on the osteoblast in vitro and animal experiment of steroid induced necrosis of femoral head. Results The cell experiment showed that dexamethasone played two roles to bone marrow' mononucleate cells in vitro. The first was that it can prevent the cells from differentiating into the osteoblasts and the second was that it can cause fatty degeneration. The animal experiment showed the number of vacant bony lacunae in femoral head, the average diameter of fat cells in marrow cavity were increased and the number of blood vessles in subchondral areas was decreased with large doses of dexamethasone. Conclusions The mechanism of steroid induced necrosis of femoral head was that dexamethasone can inhibit the grouth of the osteoblasts directely, and cause fatty proliferation of bone marrow resulting in disorder of micro circulation and osteonecrosis in the femoral head.