First, the femoral head necrosis is how to get the main reasons for the occurrence of femoral head necrosis are three: First, hormonal drugs caused by. That is, before the patient got femoral head necrosis, had applied a lot of hormone drugs, such as cortisone, prednisone, dexamethasone and other drugs, three months and six months or a year after the occurrence of hip pain, that is, got femoral head necrosis; two is traumatic femoral head necrosis. That is, caused by hip fracture, dislocation and sprain and contusion, etc.; third is a large number of alcohol abuse caused by the necrosis of the femoral head. In addition, there are a small number of hip dysplasia, blood disease, large bone disease, hypertension, radiation disease, can also cause necrosis of the femoral head. Second, ischemic necrosis of the femoral head and what factors are related to the cause of ischemic necrosis of the femoral head is not very clear, the factors that cause ischemic necrosis of the femoral head are summarized into two categories: traumatic and non-traumatic. Traumatic factors include femoral neck fracture, hip dislocation and other traumatic injuries around the hip joint. There are many non-traumatic factors, mainly long-term or massive application of hormones and alcoholism. Third, how long will drinking alcohol lead to ischemic necrosis of the femoral head According to the statistics of more than 300 cases of patients. Drinking half a kilogram of liquor every day, femoral head necrosis may appear in about 10 years, and drinking 1 kilogram of liquor every day, femoral head necrosis may appear in about 5 years. This is one of the main reasons for the apparent increase in ischemic necrosis of the femoral head in recent years. Fourth, what are the symptoms of osteonecrosis of the femoral head? After getting femoral head necrosis, the initial pain is before and after the root of the hip bone, especially the pain in the inner part of the thigh root is its characteristic. At first, it is intermittent pain, later it is persistent pain, and the pain increases when the activity increases and is relieved after rest. The second is the dysfunction of hip joint activities. Such as extension, flexion, abduction, adduction, rotation, etc. It is not possible to hitch up the “two legs”, can’t get the leg, and then walk with limp, thigh muscle atrophy, can’t squat and other symptoms. V. Why will the femoral head necrosis appear claudication Claudication is one of the main clinical manifestations of femoral head necrosis. There are three main causes of claudication: pain, functional limitation and shortening of the affected limb. When the affected limb is in pain, the affected foot lifts up quickly as soon as it hits the ground, while the healthy foot lands heavily and for a long time, so that a fast and a slow limp occurs. The functional limitation caused by femoral head necrosis is mainly manifested by the spasm of the affected hip adductor muscle, and the hip joint often shows flexion and adduction deformity and cannot be straightened and abducted, forming a relative one long and one short, resulting in claudication. In patients with femoral head necrosis, the femoral head collapses at a later stage, resulting in shortening of the affected limb by more than 1 cm, forming an absolute one long and one short, and limping. If the claudication is triggered by pain or functional limitation, the claudication disappears naturally after the pain disappears and the muscle spasm is relieved. If the claudication is triggered by collapse of the femoral head, it will remain with the patient for life. This is one of the reasons why patients with femoral head necrosis need crutches. Six, osteonecrosis why easy to occur in the femoral head human body in any part may occur osteonecrosis, ischemic necrosis alone has been found more than 40, and the highest incidence of femoral head necrosis, which is mainly determined by the biomechanical and anatomical characteristics. (1) Heavy load. The hip joint is the largest joint in the human body, supporting the weight of the entire upper body, and the weight-bearing area accounts for only 1/4 of the femoral head, and the pressure between the head and the socket is high. Maintaining this high pressure for a long time not only easily causes damage to the bone structure, but also affects the local blood circulation. (2) High shear force. The hip joint is different from other weight-bearing joints as the two bone ends of the joint force line vertical, the femoral stem and the femoral head and neck form an angle of 132 degrees, the gravity of the trunk is from the acetabulum through the femoral head and neck to the femoral stem, the force line is not vertical, it forms a shear force. Therefore, the physiological pressure on the head and neck is much greater than that on other joints. (3) Large range of motion. The range of motion of the hip joint is second only to the shoulder joint in flexion, posterior extension, abduction, adduction, and rotation. With a large range of motion, there are more chances of injury. (4) Less blood supply. The blood supply of the femoral head mainly relies on the lateral supporting band and the medial supporting band arteries emanating from the extracapsular arterial ring. The amount of anastomotic branches of the vessels is small and weak, and when one vessel is blocked and the other cannot compensate in time, it will cause the impaired blood supply to the femoral head, and the loss of blood supply to the bone tissue of the femoral head forms ischemic necrosis of the femoral head.