How long it takes for a subtrochanteric neck fracture to become necrotic depends on the patient’s own factors, age, and the extent of the fracture, and should be analyzed on a case-by-case basis. Usually, if the patient is older, the chance of necrosis of subtrochanteric fracture is higher. After conservative treatment or surgical internal fixation treatment, clinical observation and regular review of x-ray films are required. The earliest appearance of femoral head necrosis is 3-6 months, when the fracture ends begin to resorb and the femoral head collapses. However, some patients in the clinic will have bone healing after femoral neck fracture, but necrosis will reappear later, so continuous observation for 3-5 years is needed. With the extension of time, the chance of femoral head necrosis becomes smaller and smaller. Patients with subtrochanteric femoral neck fractures need to follow the doctor’s orders and have regular follow-up X-rays after surgery to observe the fracture healing. After the fracture has healed, it is necessary to continue to review X-rays regularly to observe for ischemic necrosis of the femoral head.