The pathological changes after the femoral neck fracture are as follows: one week after the femoral neck fracture, a large bone marrow bleeding can be seen in the femoral head, the bone marrow sinusoidal gap is expanded, but the bone cells have not appeared atrophy for the time being; at three weeks after the femoral neck fracture, the bone marrow cells are reduced, the fat cells are increased and deformed, and the bone cells have appeared atrophy at this time; six weeks after the femoral neck fracture, the bone marrow cells are obviously reduced, the fat cells Six weeks after the fracture of the femoral neck, the bone marrow cells are obviously reduced, the fat cells are necrotic, some of the trabeculae appear empty bone sockets, there are osteoblasts on the surface of the trabeculae, and fibrous changes appear in the bone marrow; three months after the fracture of the femoral neck, the trabeculae become hypertrophic, and the necrotic trabeculae are surrounded by laminar new trabeculae; six months after the fracture, a small cystic necrotic area is formed, surrounded by proliferating fibrous tissue, and in some patients, the trabeculae are necrotic or absent, and a large number of osteoblasts can be seen. After femoral neck fracture, microthrombi are found in the blood vessels of the femoral head, of which there are relatively few in the arteries and more in the veins. These microthrombi are able to partially or even completely block the blood vessels, thus causing a vicious cycle of femoral head ischemia. The femoral neck fracture causes ischemic necrosis of the femoral head, which varies greatly over time, but there are two kinds of pathological changes of femoral head necrosis usually found, one is segmental necrosis of the weight-bearing area, which eventually collapses and is clinical ischemic necrosis of the femoral head, and the other is idiopathic small focal necrosis, which is osteoporotic on X-ray, but shows abnormal signals in the femoral head on MRI. In idiopathic ischemic necrosis of the femoral head, there is an increase in adipose tissue and hypertrophy of adipocytes in the femoral head in the early stage. The most obvious pathologic changes of early idiopathic ischemic necrosis of the femoral head have been found to be intraosseous hemorrhage and its residuals.