AVNFH is also known as “aseptic necrosis of femoral head” or “ischemic necrosis of femoral head”. Its cause and mechanism are still unclear, with high disability rate in the late stage, seriously endangering people’s physical and mental health, and has attracted great attention from orthopedic surgeons at home and abroad. It has attracted great attention from orthopedic surgeons at home and abroad. How to achieve early diagnosis, early treatment and early prevention is the key to the treatment of this disease. Our department adopts comprehensive treatment by drug injection. The basic knowledge of the disease and precautions are listed below for patients’ reference.
1. Risk factors for the occurrence of femoral head necrosis and the characteristics of the femoral head itself.
1.1. Hyperadrenocorticism or increased exogenous corticosteroids. Clinically, it is common to see patients with ischemic necrosis of the femoral head due to long-term or intermittent high-dose use of adrenocortical steroids (hereinafter referred to as steroids). With long-term hormone application, lipids in the blood often have changes of unknown nature; at the same time, bone marrow adipocytes increase in size, forming fat emboli and blocking blood vessels; in addition, hormones can cause increased blood pressure, arteriosclerosis and osteoporosis, resulting in microfractures, and these changes may be involved in ischemic necrosis of bone tissue. It is difficult to determine the relationship between the dose and duration of steroid application and morbidity.
1.2. Alcoholism. The incidence of ischemic necrosis of the femoral head in chronic alcoholics is between 10% and 20%, which may be related to the fact that alcoholics are prone to repeated trauma, large alcohol intake tends to cause fatty liver and intravascular microthrombosis. Lymphoma and other patients treated by local radiation therapy can also cause osteonecrosis. In addition, hyperlipidemia, gout, arteriosclerosis, burns, etc. are also related to osteonecrosis.
1.3. Decompression sickness (diving sickness). Some scholars found that the incidence of osteonecrosis in diving workers was 20% when they conducted a census of diving workers.
1.4. Radiation therapy. When radiotherapy is given to women with cervical cancer, the area near the pelvis is the area of multiple radiation concentration. In addition to direct killing of bone marrow cells and bone cells, high-dose irradiation can also cause intraosseous arteritis and lumen narrowing or occlusion at a later stage, leading to ischemic necrosis of the femoral head.
1.5. Characteristics of the femoral head itself: Osteonecrosis can occur in any part of the human body, and the incidence of femoral head necrosis is the highest, which is mainly determined by the biomechanical and anatomical aspects.
1.5.1. Heavy load: The hip joint is the largest joint in the human body, supporting the weight of the whole trunk, and the pressure between the head and the socket is bound to increase. Keeping such a large pressure for a long time will not only easily cause structural damage, but also affect local blood circulation. Shear force in the hip joint is not perpendicular to the joint force line at the two bone ends like other weight-bearing joints, therefore, the physiological pressure on the head and neck of the femur is much greater than that on other joints.
1.5.2. Large range of motion: The hip joint is second only to the shoulder joint in terms of range of motion, and has the functions of extension, adduction, abduction, rotation, etc. It can accomplish all axial movements, and there are more chances of injury.
1.5.3. Low 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, and the anastomosing branches of the vessels are small and weak. When one vessel is blocked and the other cannot compensate in time, it will cause the blood supply to the femoral head to be impaired. Especially in children aged 3 to 9 years, the round ligament artery is not yet involved in the blood supply to the femoral head, and the blood supply from the nutrient artery in the marrow cavity of the femoral neck of the diaphysis is blocked by the epiphyseal plate, so the blood supply to the femoral head epiphysis in children is entirely supplied by the supporting band artery (artery of the joint capsule).
The upper supporting band artery is the most important, mainly emanating from the medial rotor femoral artery, forming a rotor femoral vascular ring with the ascending branch of the lateral rotor femoral artery, and then reaching the inferior cephalic sulcus immediately after the femoral neck and entering the femoral head. The joint capsule at this location is particularly thick and the gap is particularly narrow, so the vessels are easily compressed and embolized, resulting in secondary ischemic necrosis of the femoral head epiphysis.
2.Early diagnosis
Lack of typical clinical features of the onset, some patients will start to experience pain in the hip, low back and leg pain, knee pain, weakness or numbness in the lower limbs, and other symptoms.
Doctors tend to examine the patients with low back and knee pain only locally and ignore the examination of the hip joint, which brings hidden problems to the early diagnosis. Patients often have “resting pain” which is not relieved after resting; clinical symptoms do not match the signs; some patients with AVNFH can have severe pain and dysfunction even with minor trauma, which is not in line with the pathogenesis of trauma. The clinical symptoms are related to exertion, cold and weather changes; therefore, the patient or the doctor mistakenly believes that it is rheumatism without detailed examination leading to delayed diagnosis.
In clinical examination, the “4” test is a very clinically significant test for hip diseases; most patients do not have a positive straight leg raise test but a positive “4” test. The hip joint internal rotation and extension test is often positive; its large clinical data prove that its positive rate is much higher than that of the “4” test in patients with AVNFH.
At present, the auxiliary examinations for early diagnosis of this disease include imaging (including X-ray CT, MRI), nuclear scan, FEB and other examinations; among them, X-ray plain film examination is still in an important position. If AVNFH is suspected in the X-ray plain film, CT or MRI is performed selectively. In CT films, the appearance of thickened trabeculae, clumped or stellate distortion, large mesh, or vacuolation signs, as well as the appearance of “bilateral signs” concentric with the femoral head in different views can provide an early diagnosis of AVNFH.
The presence of effusion in the joint cavity or bone marrow edema on MRI should be taken into account for additional examination. Other tests such as nuclear scan or FEB can be chosen depending on the condition.
3.Early treatment
The aim is to improve or restore local blood circulation to prevent further necrosis, to promote the regeneration of new bone to prevent the collapse of the femoral head, and to enhance functional exercises to improve and restore the function of the joint. Treatment methods can be broadly divided into two categories: conservative therapy and surgical therapy. The treatment of early AVNFH patients should be decided according to the specific situation of the doctor and the patient: first of all, the cause or possible factors causing AVNFH should be removed, such as abstaining from alcohol, stopping hormonal drugs, controlling blood sugar or actively treating some primary diseases. Furthermore, early treatment should take into account the patient’s wishes. The patient’s wishes differ from family to family and from the patient’s situation in society.
It is important to choose the treatment method flexibly according to the patient’s wishes. Non-surgical treatment methods include non-weight bearing rest therapy, electrical stimulation, and pharmacological treatment. Pharmacological treatments include vasodilators, anticoagulants, lipid-lowering drugs and Chinese herbal medicine, all of which are effective.
Regular review in early treatment is a problem that cannot be ignored. At present, there is no special treatment method, and the duration of the disease varies. Therefore, the follow-up work during and after treatment should be strengthened clinically. The disappearance of clinical symptoms during treatment does not mean that osteonecrosis has stopped; clinical observation shows that the severity of clinical symptoms does not represent the severity of osteonecrosis; clinically, in some patients after treatment, although the clinical symptoms have improved, the phenomenon of osteonecrosis has increased; so it is very important to review every 3 months during and after treatment.
Without proper treatment, more than 80% of patients will have collapsed and deformed femoral head within 4 years and need to undergo total hip replacement. Therefore, the goal of treatment for femoral head necrosis is to prevent or delay the collapse and deformation of the femoral head and postpone the time of joint replacement by providing appropriate treatment based on early diagnosis.
4. Early prevention of disability
The traditional concept is to prevent the collapse of the femoral head by bed rest, lower limb traction and avoiding weight-bearing with the help of crutches; however, clinical experience proves that early functional exercises and weight-bearing on the basis of effective treatment measures are beneficial to the functional recovery of the hip joint. In addition, prolonged bed rest can easily lead to disuse osteoporosis of the affected limb, and slight weight-bearing can cause the collapse of the femoral head; due to prolonged bed rest, blood circulation and tissue metabolism are slowed down, which is not conducive to the repair of necrotic bone; meanwhile, the disuse atrophy of the affected limb muscles and contracture of tendons and ligaments further aggravate the dysfunction of the hip joint.
Patients with femoral head necrosis should not stand or walk for too long because of the high pressure in the hip joint, but they need to do some easy outdoor activities because the right exercise is good for promoting the regeneration and repair of femoral head necrosis, improving the function of the hip joint, relieving muscle spasm and reducing pain. Patients with osteonecrosis of the femoral head should walk with the help of crutches, and patients with bilateral osteonecrosis of the femoral head should walk with the help of double crutches.
If the condition allows and the body condition is good, you can insist on riding a bicycle or tricycle for outdoor activities every day. Because the hip joint activity is limited after femoral head necrosis, the bone quality is fragile, the reaction ability is reduced, and fracture is easy to occur, so it is necessary to prevent falling during the activity to avoid fracture.
Patients with femoral head necrosis can do some simple functional exercises in bed to improve the blood circulation of the femoral head and relieve the spastic muscles of the hip and thigh, thus reducing the pain caused by muscle spasm. Exercises for patients with femoral head necrosis should not be too strenuous or too strenuous, and can be done comfortably, such as lying on the bed, lifting both legs and doing bicycle movements; or holding the lower part of the knee joint with both hands, extremely bending the knee, so that the hip joint to the maximum range, but should not be excessive, and should be tolerated to the degree of functional exercises for different patients with different symptoms to take different exercise methods.
In case of contracture or spasm of the iliofemoral ligament, the patient should lie flat or with the hip padded;
Patients with pubofemoral ligament spasm or contracture should strengthen the practice of hip valgus function by lying down with both lower limbs straight, bending the affected limb at the hip and knee and putting the ankle joint on top of the knee joint on the healthy side (just like the “4” test) and then practicing hip valgus;
The patient should practice the “eight” squatting exercises, where the two feet are separated while the toes are pointing inward and the feet are kept in the “eight” shape and squatting exercises are performed; practice the reverse “Chaplin pace” when walking in general. The “Chaplin stride” is good for the exercise of the sciatic femoral ligament.
Functional exercises should be based on the patient’s specific condition, highlight the focus, gradually increase the intensity of the exercise, while the principle of active exercises as the main, passive exercises to supplement.
The “sun” can promote the synthesis of vitamin D in the skin and body, and vitamin D can promote the absorption of calcium and phosphorus in the body and reduce the loss of calcium and phosphorus components in the bones, which is beneficial for maintaining the bone mass of the femoral head and promoting the regeneration and repair of necrotic bone.