Osteonecrosis

Introduction to osteonecrosis The so-called osteonecrosis refers to the necrosis of the living tissue components of human bones. Motherland medicine refers to osteonecrosis as osteoplasia. Many parts of the human body can cause osteonecrosis. There are many reasons for osteonecrosis. In the clinic, femoral head necrosis is the most common. For osteonecrosis, the human body may occur in any part. Only 40 cases of ischemic necrosis have been found. The incidence of femoral head necrosis is the highest, which is mainly determined by biomechanical and anatomical features. basic knowledge The proportion of illness: 0.002% Susceptible people: no specific population Mode of infection: non-infectious Complications: osteoarthritis

Cause of osteonecrosis

Causes

Osteonecrosis is not a single disease, but a common sign caused by a variety of factors. The reasons are now described as follows.

Traumatic factors (35%):

Traumatic osteonecrosis is an ischemic necrosis that occurs as a result of trauma causing damage to a major blood supply to a certain part of the bone. Typical cases are sub-fractures of the femoral neck or dislocation of the hip, due to the joint support band that supplies blood to the femoral head. Injury of the arteries leads to avascular necrosis of the femoral head. In addition, fractures of the talus and lunate bone, dislocation, and fractures of the scaphoid and lumbar bones can also cause ischemic necrosis due to damage to the blood supply. The reason is relatively clear, is caused by blood supply disorders of the large vascular system, collectively referred to as traumatic ischemic osteonecrosis.

Occupational factors (15%):

It is well known that changes in air pressure in the surrounding environment can endanger human health. For example, divers engaged in underwater operations, as well as operators in other high-pressure environments and professional practitioners in high-altitude flights, can cause blood supply to blood vessels during rapid decompression. Osteonecrosis occurs in the form of a disorder, which is called decompression osteonecrosis.

Drug factors (20%):

A large number of clinical cases have shown that long-term use of more than the physiological requirements of adrenal corticosteroids, easy to cause femoral head necrosis, in addition, radiation exposure, alcoholism, pancreatitis, sickle cell anemia, Gaucher disease, liver disease, polycythemia, diabetes, Obesity, hyperuricemia, etc. can also induce the disease. It is unclear how all these factors cause or induce osteonecrosis, but it is speculated that most of them are related to hormones.

Other factors (10%):

In recent years, there have been clinical studies showing that there are many factors in such patients, so the cause of the disease may be the result of multi-factor combination.

Pathogenesis

Under normal conditions, the metabolic process of bone tissue is very active, with new bone formation and bone resorption, and is shaped to adapt to the needs of mechanical changes or changes in internal biochemistry, the mechanical and chemical stimulation of living bone tissue. The response is a change in the shape, volume and structure of the bone by altering the rate of bone formation or bone resorption.

The repair process of bone belongs to another complicated process of change. Regardless of the cause of death of the bone, the repair response is basically the same. The only difference between the repair of the dead bone and the reaction of the living bone is that when the dead bone is repaired, The repair material is not from the dead bone itself, but from adjacent living bone, connective tissue and blood-borne osteoblasts.

Clinical observation and animal experiments have shown that when bone tissue is necrotic, its pathological changes can be divided into the following two stages.

1. The first stage of the elimination phase, which is characterized by local necrosis of bone tissue and intramedullary cells. The capillaries and bone marrow matrix are gradually dissolved, transferred and absorbed, and finally the dead bones disappear, but this is not easy in large bones. carry out.

2. The second phase of the repair phase begins with the proliferation of stromal cells and capillary endothelial cells adjacent to the undifferentiated bone, followed by the proliferation of capillaries and undifferentiated interstitial cells to the trabecular space between the trabecular bones. Infiltration, gradually replaces necrotic bone marrow, and the posterior interstitial cells differentiate into osteoblasts on the surface of necrotic trabeculae, forming new reticular primitive bone on the trabecular bone, and then forming lamellar bone, wrapping the dead bone trabeculae. The bone mass is increased in the local unit volume. At this time, the local bone density is increased on the X-ray film. After that, the necrotic bone trabeculae wrapped by the new bone is gradually absorbed and replaced by the new living bone. Mostly the lamellar bone, and finally the repaired trabecular bone is further shaped, and the new reticular primitive bone is replaced by lamellar bone. This process is not balanced, the necrotic bone is different, and the repair process It is also different. When the margin has been in the repairing trabecular bone shaping stage, the central part may still be in the initial stage, that is, the undifferentiated stromal cells and capillary endothelial cells proliferate.

The process of such proliferation and absorption is that the latter is larger than the former, and thus the joint degeneration of the cartilage is eventually formed.

Due to the different causes of osteonecrosis, the speed, extent and extent of these reactive changes can vary widely. For example, after renal transplantation, interstitial and capillary endothelial cells are still intact due to osteonecrosis due to extensive use of adrenal corticosteroids. Hyperplasia, and spread to the bone marrow space of the necrotic trabecular bone, but can be differentiated into osteoblasts, so there is very little new bone formation on the surface of the trabecular bone in the necrotic area, and some other causes of special hair Osteonecrosis, often with a large number of cell proliferation, and differentiation into osteoblasts, quickly formed a large number of new bone.

It is clear that the repair of osteonecrosis caused by traumatic ischemia is more complete. When the repaired tissue crosses the fracture line, the proliferation, spread and new bone formation of the cells are relatively rapid and develop.

The repair process of the cortical bone is more difficult, the bone is absorbed in a large amount, but there is little new bone formation, so that there is a large amount of bone loss in the subchondral area. In this case, if the dead bone is not absorbed, the mechanical strength can be maintained. It has not changed for several years; once it is absorbed in a large amount, it is easy to produce subchondral fracture due to stress, which is why the crescent-shaped transparent area is displayed on the X-ray film.

Osteonecrosis prevention

In addition to eliminating the cause, various measures should be taken to increase local blood supply, reduce load and promote joint function recovery. Chinese medicine believes that osteonecrosis is mostly caused by heat poisoning, qi stagnation and blood stasis, rotten bone and bad marrow, and blood deficiency and deficiency, when it is clearing heat and stagnation, replenishing liver and kidney for treatment.

Osteonecrosis complications Complications osteoarthritis

With lameness and increased pain, hip function is gradually limited, and the hip joint can be stiff and disabling in the late stage.

Osteonecrosis symptoms common symptoms joint pain elderly hip pain hip soreness discomfort

Chronic medical history, such as history of trauma, excessive application of hormones and excessive drinking history, early local pain symptoms, from mild to heavy, late dysfunction can also occur, limb malformation, so that the function is completely lost.

According to X-ray findings and bone biopsy results, Hungerford and Zizic divided the femoral head necrosis caused by alcoholism into the following four phases:

1. The first phase of the X-ray film is normal, and a biopsy of the bone is required to make a diagnosis.

2. The second phase of X-ray film showed positive findings, showing atypical signs of idiopathic femoral head necrosis, but the articular cartilage bone plate was normal.

3. The third phase showed a specific change, showing that the anterior and posterior cranial bones of the femoral head were hardened, with speckled osteoporosis, inferior or indirect lines under the cartilage, and the femoral head lost its normal spherical shape.

4. The 4th X-ray film showed a late change, at which time the femoral head was significantly deformed and the joint space was narrow or disappeared.

Examination of osteonecrosis

The laboratory examination of the disease is mainly based on CT and MRI. In recent years, with the extensive development of CT and MRI imaging techniques, not only can clearer images be obtained than conventional X-ray films, but lesions can be detected early. The positive ones can be selected earlier than 1 to 3 months earlier than the X-ray film, and compared with the X-ray film.

Diagnosis and diagnosis of osteonecrosis

diagnosis

The diagnosis of osteonecrosis is mainly based on chronic medical history, clinical manifestations and imaging studies. In particular, the latter is not only conducive to the diagnosis and differential diagnosis of the disease, but also important for the determination and staging of the disease, the choice of treatment methods and the prognosis. According to the X-ray film, the osteonecrosis of the adult can be staged. However, the causes are different, their stages are also inconsistent, and the opinions of various experts are not uniform.

Differential diagnosis

Osteonecrosis needs to be differentiated from various injuries, especially common diseases in the predilection site. For example, cases involving femoral head necrosis often require differential diagnosis with hip tuberculosis, hip suppurative inflammation, rheumatoid arthritis, rheumatism, hip tumors, and hip disorders of various ages; wrists The scaphoid necrosis, lunate bone necrosis and talus necrosis of the foot and ankle need to be differentiated from local frequently-occurring diseases.

The material in this site is intended to be of general informational use and is not intended to constitute medical advice, probable diagnosis, or recommended treatments.