Establishment and assessment of rat models of glucocorticoid-induced osteonecrosis

To establish the rat models of glucocorticoid-induced osteonecrosis and evaluate the osteonecrosis by high-resolution micro-CT and histomorphology.

Totally 30 Sprague-Dawley male adult rats (age:12 weeks; body weight:400-450 g) were randomized into two groups:one group received two doses of intraperitoneal injection of lipopolysaccharide (20 μg/kg) at an interval of 24 hours, 24 hours later, the rats received three doses of intramuscular injection of methylprednisolone (40 mg/kg) at an interval of 24 hours; in the control group,the rats received same amount of normal saline. Four weeks later, 5 rats in each group were sacrificed randomly.Eight weeks later, all the remaining rats were sacrificed and the femur specimens were scanned by micro-CT. The trabeculae parameters of the femoral head were calculated. The hematoxylin and eosin staining were performed to calculated the success rate.

The incidence of osteonecrosis was 80% in the experimental group. The micro-CT demonstrated broken and cystic degeneration. The quantitative analysis showed that the bone volume/total volume (experimental group:0.55 ± 0.13 vs.

0.68 ± 0.12;P<0.05), bone surface area / bone volume (experimental group:20.45 ± 5.13 vs.

24.00 ± 5.20;P<0.05), and trabeculae number(experimental group: 5.67 ± 0.50 vs.

6.24 ± 0.96; P<0.05) were significantly lower in experimental group than those in control group.

A rat model of glucocorticoid-induced osteonecrosis was successfully established by lipopolysaccharide and methylpredniso- lone. High-resolution micro-CT is useful for the qualitative and quantitative analyses of the morphology and structure of trabeculae, showing good consistence with the histomorphological findings.