The observation of femoral head osteonecrosis by Hematoxylin-Eosin staining. In the group A, it showed partial necrotic changes in bone trabeculae and slight accumulation of degenerative or necrotic medullary haematopoietic cells and fat cells in the surrounding bone marrow. A few apparent empty lacunae were observed. The increase of fibroblasts and osteoclasts were not obvious. In the group B, the bone trabecular became sparse and fracture, more empty lacunae were seen in it. Haematopoietic cells and fat cells showed necrotic changes, the fibroblasts and osteoclasts increased and accumulated, and many activated osteoclasts were observed and resorbing the necrotic bone trabeculae. The performance of osteonecrosis became more and more serious with time. There was no visible necrosis of bone or bone marrow in the group N. (Magnification 200×, scale bar represents 100 μm for all figures, the green arrow stands for the empty lacunae, the red arrow stands for the multinucleated giant cells or osteoclasts, and the blue arrow stands for the necrosis or fibrosis of bone marrow).Immune response associated with Toll-like receptor 4 signaling pathway leads to steroid-induced femoral head osteonecrosis. Tian L, Wen Q, Dang X, You W, Fan L, Wang K - BMC musculoskeletal disorders (2014). Not Altered. CC.