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

Digital histological images were captured with a microscopic imaging system (Leica DM5500; Leica Microsystems, Wetzlar, Germany). The presence of osteonecrosis (ON) was examined with the established criteria, i.e., diffused presence of empty lacunae or pyknotic nuclei of osteocytes in trabecular bone accompanied by surrounding necrotic bone marrow [24] . The rat with at least one ON lesion in the proximal femur, distal femur, proximal tibia or distal tibia was considered as ON þ rat, whereas that with no ON lesion was considered as ONÀ rat. Histomorphometric analysis was carried out on the metaphysis of the proximal tibia in a 2mmewide area 2 mm below the growth plate, and 3mmewide area of bone marrow from the end of the distal tibia using OsteoMeasure Histomorphometry System (Osteometrics Inc, Atlanta, GA, USA) and analysed according to a standard histomorphometry protocol [25] . The osteoblast surface (Ob. S/BS), osteoclast number (N.Oc/BS) and marrow fat fraction were determined on the red marrow region in the proximal tibia, and marrow oedema fraction was determined on the yellow marrow region in the distal tibia.