Patient: Description (onset time, main symptoms, hospital visited, etc.): Male, 16 years old, right femoral neck fracture, on June 22, 2010, under lumbar anesthesia, closed reduction hollow tension screw oblique internal fixation, and right lower limb skin traction and anti-infection treatment, now discharged from the hospital. What should be done to prevent femoral head necrosis? How should I guide the patient to exercise and how to control the amount of exercise? Thank you, doctor! Doctor: The percentage of femoral head necrosis in femoral neck fracture is 5-30% depending on the fracture, and the percentage of femoral head necrosis in young people is definitely violent injury, if the surgery is too long from the injury, such as more than 24 hours, the necrosis rate will increase more than 1 times. When the fracture heals when fully weight bearing, on the other hand, femoral head necrosis is not terrible, early detection early treatment success rate is very high, afraid of misdiagnosis or delay, the general course of the disease 4 months will appear femoral head collapse, so should be in six months, 1 year, 1.5 years, 2 years, 3 years …… review nuclear magnetic.