Osteonecrosis of the femoral head is also known as ischemic necrosis of the femoral head, aseptic necrosis of the femoral head or osteoembolism of the femoral head. There are many causes of osteonecrosis of the femoral head, and there are nearly 70 known factors, except for traumatic necrosis which directly destroys the blood supply of bone, leading to the occurrence of ischemia and hypoxia of bone cells and finally the death of bone cells, the relationship between other factors and osteonecrosis is not very clear.
The exact incidence of osteonecrosis of the femoral head in China is not clear. According to the data, the annual incidence of new cases of osteonecrosis of the femoral head in the United States is 15,000 to 20,000 cases, and the cumulative number of such cases in the country is between 300,000 and 600,000. In Japan, there were 4,000 new cases in 1994. Based on this projection, the new cases in China should be between 75,000 and 150,000 per year, and the accumulated cases are between 1.5 million and 3 million. Since corticosteroid abuse is common in China and alcoholism is serious, the actual number of cases will be higher than this.
Post-traumatic osteonecrosis caused by hip fracture is a common cause of osteonecrosis. Femoral neck fracture, traumatic dislocation of the hip joint, and femoral head fracture can all cause femoral head necrosis. An obviously displaced femoral neck fracture interrupts the blood flow supplying the femoral head, and necrosis begins eight hours after the injury. About 80% of femoral neck fractures cause varying degrees of ischemia to the femoral head, but about 30% eventually collapse . Osteonecrosis is related to the external force of the trauma, the degree of displacement and the appropriateness of the treatment.
Medical trauma, such as forceful massage, femoral neck osteotomy and synovectomy, can also cause osteonecrosis of the femoral head. The incidence of osteonecrosis of hip dislocation is 4% to 10%, and its occurrence is related to delayed reset and the degree of trauma.
The following are the high-risk triggers of osteonecrosis of the femoral head.
(1) Adrenocorticotropic hormone is the most common cause of femoral head necrosis in the country. According to statistics, prednisone 30mg daily for one month will cause osteonecrosis in about 1/3 of people. There is a greater risk of high-dose shock therapy in the short term.
(2) Alcoholic osteonecrosis is common in the northern part of China. May be related to alcohol-induced disorders of fat metabolism in the liver. According to statistics, if you drink more than 450ml of alcohol per week, long-term drinking can occur osteonecrosis, but individual differences are great.
(3) Decompression disease or Caisson’s disease. This kind of osteonecrosis can occur from high pressure state back to atmospheric pressure state, can also occur from atmospheric pressure to low pressure state, such as plateau life and diving workers.
(4) Sickle cell anemia. The incidence of osteonecrosis is between 12% and 20%, due to increased blood viscosity, slowing blood flow and forming blood clots.
(5) Idiopathic osteonecrosis, which Chandler called the “coronary heart disease” of the hip joint. Some of the causes are unknown, while others are due to a combination of factors. In recent years, due to advances in research, many patients have found the cause, so the proportion of patients diagnosed with idiopathic osteonecrosis is decreasing.
Most patients with osteonecrosis of the femoral head are asymptomatic in the early stages. Pain is the most common symptom in the early stages in some patients. The pain most often occurs at the base of the thigh and radiates to the inner thigh and knee, leading some patients to suspect a knee problem, and some patients may experience hip pain. The pain can be sudden or insidious and progressive. The severity of pain varies widely from patient to patient. If the pain does not disappear at rest, worsens with joint movement or even limping, and the movement of the hip joint is limited (especially with internal rotation), then femoral head necrosis should be highly suspected.
Differentiation of pain
Femoral head necrosis is only one of the many causes of hip pain. There are many other diseases that can cause hip pain.
1, traumatic: such as soft tissue injury around the hip joint, fracture, dislocation, acetabular glenoid margin injury;
2, developmental: such as structural changes caused by hip dysplasia;
3, neurological: such as hip joint peripheral nerve entrapment syndrome;
4, inflammatory: such as rheumatoid arthritis, ankylosing spondylitis, osteoarthritis of the hip joint;
5, infectious: such as hip tuberculosis, septic arthritis, osteomyelitis; hip joint tumor;
6, radiological pain: such as lesions of the lumbar spine and so on dozens or even hundreds of common disorders can cause pain around the hip joint and cause walking limp.
The importance of early detection of femoral head necrosis
It is clinically found that if osteonecrosis of the femoral head is not treated effectively before the femoral head collapses, more than 80% of patients will collapse within 2 to 3 years, and 78% of the collapsed necrotic femoral head will develop to the extent that artificial joint replacement is required within 2 years, and the long-term efficacy of artificial joint replacement for young and middle-aged patients is poor compared to that of older patients. There are no drugs with proven efficacy to cure femoral head necrosis.
Early detection means that the correct diagnosis of the disease is made before the femoral head collapses, i.e., when it is asymptomatic, which is difficult. Patients with hip trauma, fractures, and those with risk factors for femoral head necrosis need to be especially alert.