Osteonecrosis is the death of a segment of bone caused by a lack of blood supply. It can result from an injury or occur spontaneously. Symptoms usually seen include pain, limitation of movement and, when the lower limb is affected, limp. Stopping smoking and alcohol abuse, as well as reducing the use or dose of corticosteroids can reduce the risk of developing osteonecrosis. Different surgeries can be done if non-surgical measures, which include rest, physical therapy, and pain relievers, do not relieve symptoms. In later stages, a prosthesis may be necessary to relieve pain and maintain function.

Also called “bone infarction”, osteonecrosis is characterized by the abnormal and premature death of bone tissue as well as by its decomposition and destruction, due to a defect in intraosseous vascularization.

The limb most commonly affected is the hip, followed by the knee and shoulder. In the case of the hip, osteonecrosis can affect the femoral head and lead to its partial or total destruction. In the case of the knee, osteonecrosis affects the internal condyle of the femur, that is, the area that articulates with the tibia to make the knee joint work, and causes the destruction of the bone by necrosis.

The wrist, the ankle as well as the front part of the foot, that is to say the metatarsals in particular those near the big toe, are less frequently affected. Rarely, osteonecrosis affects the shoulder in isolation, without the hip also being affected.

Osteonecrosis of the jaw has features that differ from osteonecrosis at other sites. It touches the mandibular bone and bares the jaw.

The most common cause of osteonecrosis is traumatic. Non-traumatic osteonecrosis, on the other hand, affects men more often than women, is observed especially between the ages of 30 and 50 and is bilateral in more than 60% of cases, that is to say it often affects both hips or both shoulders. In about 20% of people with osteonecrosis, the cause is unknown.

Traumatic osteonecrosis

The most common cause of traumatic osteonecrosis is a displaced fracture, where a bone breaks into at least two parts and moves in such a way that the fractured ends do not line up. The type of displaced fracture that causes osteonecrosis most commonly affects the hip and occurs most often in older people.

Another cause of traumatic osteonecrosis is dislocation, which is seen when the two bony ends of a joint completely separate from each other, as in the case of hip dislocation.

A displacement fracture or dislocation can damage the blood vessels that supply the upper thigh bone, resulting in the death of that part of the bone. This bone death occurs less often in other areas of the body.

Non-traumatic osteonecrosis

Non-traumatic osteonecrosis, which occurs without trauma or direct injury, is caused by a disorder causing blockage of the small blood vessels that supply certain areas of the bone, such as:

• chronic excessive alcohol consumption (more than three drinks per day for several years);
• treatment with corticosteroids given in high doses and / or for long periods;
• blood clotting disorders such as a deficiency in protein C, protein S, antithrombin III or the presence of anti-cardiolipin antibodies;
• high dose bisphosphonate treatment of osteoporosis;
• chemotherapy;
• Cushing’s syndrome;
• decompression sickness (decompression sickness) occurring in divers who ascend too quickly to the surface;
• Gaucher’s disease;
• high blood lipid levels (hyperlipidaemia);
• HIV infection;
• liver disease;
• lupus and another autoimmune connective tissue disease;
• various disorders such as chronic renal failure and rare genetic mutations;
• an organ transplant;
• pancreatitis;
• radiation (radiotherapy);
• sickle cell anemia;
• smoking;
• obesity;
• a tumor.

General symptoms

Areas affected by osteonecrosis may remain asymptomatic for weeks or even months after vascular injury. Usually the pain comes on gradually, but it can also come on suddenly. Due to bone necrosis and sagging of the affected bone, the pain increases and is aggravated by movement and carrying loads. The person avoids moving the joint to reduce pain. These are usually relieved by rest. If the affected bone is in the lower limb, standing or walking worsens the pain and lameness develops.

Specific joint symptoms

Osteonecrosis of the hip causes pain in the groin that can radiate to the thigh or buttock. Movement becomes limited and lameness may occur.

Spontaneous osteonecrosis of the knee usually causes sudden pain along the inner part of the knee without triggering trauma. This area can be tender and the joint often swells with a buildup of fluid. Bending the knee can be painful and those affected may limp.

Osteonecrosis of the shoulder often causes less pain and discomfort than in the hip and knee.

Prevention

To reduce the risk of osteonecrosis, these are:

• limit the use of corticosteroids only when absolutely necessary, at doses as low and for as short a duration as possible;
• follow established decompression rules for diving and working in a pressurized environment;
• avoid excessive consumption of alcohol and tobacco;

Treatment

Osteonecrosis resolves spontaneously in some people if it is diagnosed early enough, if the affected area is small, and it is not in the major weight-bearing region.

Management of osteonecrosis includes:

• non-surgical measures to relieve symptoms such as taking anti-inflammatory drugs and other pain medications, reducing activity and strain, and physical therapy;
• surgeries aimed at stimulating bone repair and slowing or preventing the progression of the disease, such as surgical decompression which involves making one or more small holes in an attempt to reduce the pressure inside the bone and forcing the production of new cells. This can be followed by the injection of the person’s own bone cells into these small holes, which improves clinical results;
• bone grafting, or transplantation of bone from one site to another, to support the area of ​​bone that is weakened and stimulate new bone formation in the affected area;
• an osteotomy, a procedure designed to preserve the affected joint. This is done especially in the hip region and may be appropriate for young people with mild collapse, for whom central decompression or other interventions are not recommended;
• total joint replacement with a prosthesis, or arthroplasty, an effective procedure for relieving pain and allowing recovery of range of motion, if osteonecrosis has caused significant joint collapse and osteoarthritis. This is frequently the case when the hip is affected.

Osteonecrosis of the jaw, for its part, requires specific treatment by a specialist in stomatology.