Definition
Osteonecrosis (also known as bone necrosis, bone infarction) is an infarction of a whole bone or a part of a bone, which leads to the death of tissue (= necrosis). In principle, osteonecrosis can occur in any bone in the body (even in the big toe: Renander’s disease). However, there are some preferred localizations. These include the femoral head, the parts of the femur and tibia close to the knee joint, the head of the humerus and the vertebral bodies. People of all ages can be affected by this clinical picture.
Causes
A bone infarction is caused by the occlusion of a blood vessel that is responsible for supplying the respective bone (section). As a result, the tissue at this point is no longer (sufficiently) supplied with blood, oxygen and nutrients, causing it to die. There are many reasons for such an occlusion.
There are different forms of osteonecrosis depending on the underlying cause: septic osteonecrosis, which occurs either during or as a result of an infection, and aseptic bone necrosis, which is not caused by an infection. Often an injury (trauma) is the cause, which is why this variant is also called (post)traumatic bone necrosis. A special form of osteonecrosis is the development during therapy with bisphosphonates, which mostly manifests itself in the jawbone.
Bisphosphonates are drugs that are used, for example, to treat osteoporosis. They are deposited on the surface of bones and ensure that the degradation of bone is inhibited. At the same time, however, they also inhibit the formation of new blood vessels in the bone tissue, making bones that have been previously damaged, for example by trauma or infection, particularly susceptible.
Symptoms
The main symptom of osteonecrosis is a severe pain in the affected area. This is often accompanied by a limited range of motion. If it is a part of the bone near the joint, it can also lead to joint effusion or swelling of the joint.