In 1986, the FDA defined bone discontinuity as “at least 9 months after injury and fracture with no tendency to heal further for 3 months. However, this criterion does not apply to every fracture. Fractures of long bony cadres take a long time to heal and cannot be considered as osteonecrosis for at least 6 months, especially if there are local complications such as infections, which are diagnosed clinically by X-ray examination in combination with the above symptoms. The typical X-ray features of osteonecrosis are: 1) gap at the fracture end; 2) sclerosis of the fracture end with a smooth and clear fracture surface; 3) closure of the bone marrow cavity; 4) no trabeculae formation between the bone scabs The diagnosis of osteonecrosis is made by clinical or X-ray confirmation of fracture healing arrest without connection.