Avascular necrosis of the femoral head

　　Multiple primary diseases are related to avascular necrosis of the femoral head, some of which have been confirmed as triggering factors. The most common sites of traumatic avascular necrosis are the femoral head, humeral head, ankle bone, and scaphoid bone. Trauma can lead to avascular bone necrosis due to obstructed blood supply, at the same time, a functional patent anastomosis will form between the small arteries supplying the femoral head and humeral head, which is a common phenomenon in the population.

　　Dislocation of the hip joint tears the ligaments and joint capsule, and the damaged blood vessels are often located at the folds of the joint capsule. After hip dislocation for more than 12 hours, 52% of patients develop avascular necrosis, while the incidence of bone necrosis is 22% for those who recover within 12 hours. The incidence of avascular necrosis and collapse after fixation surgery for fractures is 11%-45%, which is unrelated to the surgeon's technique and the method of fixation device.

　　Late-stage avascular necrosis of the femoral head is prone to complications such as limping in patients, which gradually worsens, manifesting as a significant feeling of leg shortening, difficulty in walking, and pain. Therefore, it should attract the high attention of both doctors and patients.

　　The early stage of avascular necrosis of the femoral head commonly presents the following main clinical symptoms:

　　1. The first symptom to appear is hip pain and distension, which can be persistent or intermittent, and pain may alternate in both sides of the lesion.

　　2. Normal or slightly reduced hip joint activity, especially obvious limitation of internal rotation.

　　3. Intermittent limping.

　　4. Pain on the greater trochanter叩击痛, deep tenderness in the local area, tenderness at the insertion of the adductor muscles, positive Thomas sign, positive sign of the 4-letter test.

　　The specific preventive measures for avascular necrosis of the femoral head include the following aspects:

　　1. Bracing should be immediate after fracture. Do not try to stand up or move the hip joint before visiting the doctor to prevent further vascular injury. When moving the patient, do so smoothly and avoid excessive traction of the hip joint.

　　2. Treatment should be initiated as soon as possible after fracture; the longer the time, the higher the necrosis rate.

　　3. The reduction must be accurate. The higher the quality of reduction, the lower the necrosis rate.

　　4. Strive for one-time reduction; repeated reduction will increase vascular injury.

　　5. Strive for closed reduction; if it fails, surgical reduction can be performed. During surgery, soft tissue stripping should be minimized to prevent further damage to blood supply.

　　6. Choose a fixation method with minimal trauma and good stability. Multi-needle fixation causes the least damage and is a good fixation method.

　　7. Elderly patients with subcapital fractures can directly undergo total hip arthroplasty to shorten the treatment cycle.

　　There are many methods for diagnosing avascular necrosis of the femoral head, among which the most commonly used examination methods are as follows:

　　1. X-ray examination

　　X-ray examination is the main basis for diagnosis, and sometimes an accurate diagnosis can be made without other imaging methods. The classic Ficat staging divides it into the following five stages:

　　In stage 0, there are no clinical manifestations at all. X-ray examination is normal, and bone scan shows decreased uptake.

　　In stage I, there are no or only slight manifestations. X-ray examination is normal, bone scan shows a cold area in the femoral head, pathological examination finds infarction in the load-bearing area of the femoral head, and a large number of necrotic bone marrow cells, osteoblasts, and osteocytes are visible in biopsy.

　　In stage II, clinical manifestations are slight. X-ray examination shows changes in the density of the femoral head (in stage IIA, sclerosis or cysts appear, the contour of the femoral head is normal; in stage IIB, the crescent sign appears), bone scan shows increased uptake, pathological examination finds spontaneous repair in the infarcted area, and new bone deposition is visible between the necrotic trabeculae in biopsy.

　　In stage III, there are mild to moderate clinical manifestations. X-ray examination shows that the femoral head loses its spherical contour and collapses, bone scan shows increased uptake, pathological examination finds subchondral fractures, the necrotic area collapses, and trabeculae and bone marrow cells are visible on both sides of the fracture line in biopsy.

　　In stage IV, clinical manifestations are obvious. X-ray examination shows narrowing of the joint space, changes in the acetabulum, increased uptake on bone scan, pathological changes of osteoarthritis, and degenerative changes in the acetabular cartilage as seen in biopsy.

　　The X-ray tomography of the femoral head is of great value in detecting early lesions, especially in the examination of the crescent sign, so for those with early stage avascular necrosis of the femoral head, X-ray tomography can be performed.

　　2. CT examination

　　CT can detect small lesions early and differentiate whether there is bone collapse and its extension range, thus providing information for the selection of surgical or treatment plans. In the early stage of osteonecrosis, inside the femoral head, the inner part of the primary pressure trabeculae and the primary tension trabeculae combine to form a distinct area of increased bone density, which appears as a radiating image in the axial view and is called the star sign, which is the diagnostic basis for early osteonecrosis; in the late stage of osteonecrosis, the axial CT scan can show limited annular areas of decreased density in the middle or edge, and the three-dimensional images displayed by CT scan can provide relatively accurate information for evaluating the degree of avascular necrosis of the femoral head.

　　3. Magnetic resonance imaging (MRI)

　　Magnetic resonance imaging (MRI) is an effective non-invasive early diagnostic method. It has obvious sensitivity and specificity for bone necrosis and can detect lesions earlier than CT, distinguishing between normal and necrotic bone and bone marrow, as well as repair zones.

　　4. Bone blood flow dynamic examination

　　It is generally believed that for patients with normal X-ray films or only mild osteoporosis, no clinical symptoms or mild pain, and limited hip joint movement, bone blood flow dynamic examination can help confirm the presence of early avascular necrosis of the femoral head, with an accuracy rate of up to 99%.

　　5. Arteriography

　　Currently, most scholars believe that the cause of avascular necrosis of the femoral head is damage to the blood circulation supplying the femoral head. The abnormal changes found in angiography can provide evidence for the early diagnosis of avascular necrosis of the femoral head.

　　6. Radioisotope scanning

　　This examination is a safe, simple, highly sensitive, painless, and non-invasive examination method, which is of great value for the early diagnosis of avascular necrosis of the femoral head, especially when X-ray examination shows no abnormalities, but clinical suspicion of bone necrosis is high, it can usually be 3-6 months earlier than X-ray films.

　　7. Pathological tissue examination

　　Pathological tissue examination is limited to surgical cases, and the pathological diagnosis of bone necrosis is based on bone marrow fibrosis, fat cell necrosis, trabecular bone necrosis, and some repair findings, such as microvascular regeneration and granulation tissue.

　　Patients with avascular necrosis of the femoral head should pay attention to the following points in diet:

　　1. Properly match staple foods

　　The staple food for patients with avascular necrosis of the femoral head should be mainly rice, noodles, and mixed grains, but attention should be paid to a variety of types and appropriate proportions of coarse and fine grains.

　　2. Avoid eating spicy foods

　　Patients with avascular necrosis of the femoral head should not eat spicy foods and should eat more fresh vegetables and fruits.

　　3. Reduce the intake of sweet and greasy foods

　　If patients with avascular necrosis of the femoral head consume too much rich and greasy food and have little physical activity, it will increase blood lipids, increase blood viscosity, and slow blood flow, which is not conducive to the repair of the femoral head.

　　4. Reduce the intake of alcohol

　　Drinking白酒 and beer is harmful to the human body with avascular necrosis of the femoral head, and there is no benefit. Only drinking a small amount of wine has the effect of softening blood vessels.

　　There are many treatment methods for avascular necrosis of the femoral head, but there is still no effective treatment that can prevent the progression of the disease or delay the destruction of the femoral head and hip joint degeneration after subchondral bone collapse. Currently, the appropriate treatment measures are mainly selected based on its stage.

　　I. Non-surgical Treatment: Young patients have a good potential for self-repair. With the growth and development of adolescents, the femoral head can often be remodeled to achieve satisfactory results. For adult patients with stage I or II lesions with a small range, non-surgical treatment can also be adopted:

　　1. Unilateral hip joint lesions should strictly limit weight-bearing on the affected side, and crutches or walking aids can be used for walking.

　　2. Bilateral hip joint lesions should be bedridden or use a wheelchair.

　　3. If hip pain is severe, lying in bed and applying lower limb traction can alleviate symptoms.

　　4. Physical Therapy.

　　5. Traditional Chinese Medicine, such as Guguling Capsules.

　　During conservative treatment, X-ray films should be taken regularly until the lesion is completely healed before weight-bearing is allowed.

　　II. Surgical Treatment: Different methods are used according to the stage of the lesion:

　　1. Femoral Head Drilling and Bone Grafting: This operation is suitable for stage II. By decompressing the necrotic area of the femoral head, it is conducive to reconstructing the blood supply of the femoral head, and the patient should start using the lower limb continuous passive exercise device as soon as possible after surgery. When getting out of bed, the patient should use crutches, and the operated side should avoid bearing weight for at least half a year.

　　2. Intertrochanteric Rotation Osteotomy: This operation is suitable for stage II. By changing the load-bearing surface of the femoral head, it allows the normal cartilage of the femoral head to bear stress, thereby alleviating symptoms and improving function.

　　3. Multiple Vascular Bundles or Blood-Perfused Iliac Bone Transplantation: This operation is suitable for stages II and III. It clears the ischemic necrotic area of the femoral head, fills the necrotic area using methods such as the iliac bone with the deep iliac vessels and the sartorius iliac bone flap, etc., to improve the blood supply to the femoral head, and promote the restoration of the deformed femoral head to its original shape as much as possible, thereby improving the function of the hip joint to a certain extent.

　　4. Artificial Joint Replacement: This operation is suitable for stages III and IV and is divided into artificial femoral head replacement and total hip replacement. It can eliminate pain and improve or even completely restore function.

　　5. Hip Arthrodesis: This operation is commonly used for patients who stand for long periods of time, frequently walk, and those who are not suitable for other surgeries. It often leads to complete loss of joint movement and a higher chance of non-healing or delayed healing after surgery, so it should be approached with great caution.