Steroid-associated osteonecrosis animal model in rats

Zheng, Li-Zhen; Wang, Jia-Li; Kong, Ling; Huang, Le; Tian, Li; Pang, Qian-Qian; Wang, Xin-Luan; Qin, Ling

2, and one died at day 3 after LPS injection; three additional rats were supplemented for replacement. The total mortality rate was 15.8% (3/19) . The acute sicknesses were recovered at the second week. We defined the osteonecrosis-positive (ONþ) and osteonecrosis-negative (ONÀ) region by histological analysis on H&E-stained sections with the established criteria: the ON þ region showed diffused presence of empty lacunae or pyknotic nuclei of osteocytes in trabecular bone accompanied by surrounding necrotic bone marrow, whereas ONÀ region showed normal osteocyte with surrounding normal bone marrow [24] . At week 2, all the rats developed osteonecrosis based on histological evaluation with 100% incidence of SAON (8/8). Empty lacunae of osteocytes were found in the trabeculae. Oedema and fibrous marrow appeared in necrotic bone marrow. At week 6, six rats showed oedema and fibrous marrow and empty lacunae of osteocytes with 75% incidence of SAON (6/8). The proximal femur was the site of highest instance of ON 2 weeks after induction. At week 6, the instances of ON in the proximal femur, distal femur and proximal tibia were significantly decreased when compared with those at week 2, whereas the instance of ON in the distal tibia did not change statistically ( Fig. 2 and Table 1 ).