Objective:To investigate the significance of bone mineral changes in the pathogenic process of steroid-induced osteonecrosis in rabbits. Methods:Seventy adult female Japanese White rabbits were randomly divided into five groups. Animals in steroid group received an intramuscular injection of methylprednisolone acetate （4 mg/kg） once a week

and killed in four different time after first treatment. Animals in control group received an intramuscular injection with the same volume of normal saline

while 150 kU penicillin was injected twice a week for preventing infection in all groups. The contents of serum calcium （Ca） and phosphorus （P） were determined and the bone mineral densities of the femoral head and neck were measured at the 2nd

4th

8th and 10th weeks after first treatment. Meanwhile the general condition such as weight

spirit and hair of rabbits was observed. Results:Compared with the control group

the weight of rabbits in steroid group lost since the first week

and progressively aggravated; the bone mineral density of the femoral head and neck was lowered since the 2nd and 4th week respectively （P<0.05

P<0.01）

and lowered more quickly in femoral neck than in femoral head. In steroid group

the bone mineral density of the femoral neck at the 10th week was significantly lower than that at the 8th week （P<0.05）. Compared with the control group

the serum levels of Ca and P in steroid group were lowered since the 2nd week （P<0.05

P<0.01）. In steroid group

the serum Ca level at the 10th week was lower than that at the 8th week

and the serum P level waslowered more quickly than Ca level was. Conclusion:Osteonecrosis appears in rabbits shortly after corticoids are first administered

and osteonecrosis in rabbits is chronologically associated with the onset of hypocalcaemia

hypophosphatemia and lowered bone mineral density. Steroid-induced osteonecrosis may be relevant to bone mineral loss and density lowering of the femoral head and neck.