Destruction of bone tissues is known as osteonecrosis. Our bones are made of living cells. Just as any other body cell, the bone cells too need nourishment and oxygen supplied through the blood stream for survival. In healthy people, new bone cells replace the old cells, thereby maintaining the normal density of the bones. Osteonecrosis develops when the bone cells start breaking down owing to absence of blood supply. This is a painful condition that may affect one or several bones.
Although osteonecrosis can affect people of either gender at any age, it is more common between 30 and 60 years of age. At the early stage of the disease, the symptoms are similar to that of arthritis. It causes severe joint pain that persists even while resting. The upper leg, upper arm, ankles, knees and shoulders are common sites of osteonecrosis.
Causes Of Osteonecrosis
Severe bony injury is the most common cause of osteonecrosis. Dislocation or fracture of a joint or any other form of physical trauma that disrupts blood flow to the bone triggers osteonecrosis. The bone cells cannot survive without nourishment. Over time the rate of destruction of bone cells overtakes formation of new bones, leading to severe bone pain and debility.
Long-term alcohol abuse can cause osteonecrosis. Excessive alcohol intake for a prolonged period stimulates fat buildup in the blood vessels, which narrows the blood vessels and slows down blood flow. Osteonecrosis develops when fatty substances clog blood vessels that supply blood to the bones.
Corticosteroid-induced osteonecrosis occurs following prolonged use of high doses of corticosteroid medicines. Corticosteroids trigger mobilization of fats from the liver into the blood vessels. The lipids block the ends of the arteries that supply blood to the bones. Corticosteroid-induced osteonecrosis is more common in people suffering from lupus and vasculitis.
Bisphosphonates are drugs used for treating osteoporosis. Osteonecrosis of the jaw is a rare side effect of the drug. Risk of osteonecrosis is especially high in cancer patients on high dose bisphosphonate therapy for at least 12 months. Although the mechanism that causes osteonecrosis of the jaw following bisphosphonate use is not well understood, scientists believe that reduction in formation of blood vessels, reduced ability of the bone to repair itself and infections may cause osteonecrosis.
Diseases that impair blood flow to the bones are common causes of osteonecrosis. Diseases commonly associated with osteonecrosis include Gaucher’s disease, sickle cell anemia, lupus and HIV. Gaucher’s disease is a rare genetic disorder that stimulates build-up of fatty substances in the bone marrow, which by increasing pressure inside the bone, reduces blood supply to the bone.
People suffering from sickle cell anemia do not have sufficient red blood cells for carrying oxygen that may lead to osteonecrosis by decreasing supply of oxygenated blood to the bones. Lupus and HIV accelerate deterioration of the bone health, resulting in death of bone cells.
Osteonecrosis can develop owing to radiation therapy in cancer patients. Local radiotherapy can damage the blood vessels supplying blood to a bone at the site of the radiotherapy treatment. Reduction of blood supply to the bone increases destruction of the bone cells, leading to osteonecrosis.