Avascular Necrosis

Avascular necrosis is a disease caused by dimished vascular supply to bone. The underlying cause is currently not fully known. The most common sites for avascular necrosis are in the hip, knees, and shoulder. A number of theories have been promoted to explain this disease. These include an increased tendency to form blood clots within bone, an increase in size of the fat cells within the bone, and a decrease in the drainage of venous blood from bone. Patients often present with achy pain in the joint. The radiographs are initially completely normal. As the disease progresses, the bone can become increasingly dense and collapse away from the overlying articular cartilage. As a result, the cartilage is no longer supported. In the hip, the previously spherical femoral head can become flattened. As the femoral head becomes flattened, the adjacent cartilage of the hip socket is also damaged leading to an arthritic joint. In the early stages of treatment, prior to collapse of the bone, drilling of the involved region has lead to pain relief and potentially an improved prognosis. This procedure known as “core decompression” has less effective results as the degree of involvement goes up. A large number of surgical procedures have been used to treat more advanced cases of avascular necrosis including realignment of the bone (osteotomy), supporting the bone with a graft from the fibula, as well as hip replacement surgery in the most severe cases. One potential treatment option is to try to improve the healing potential of the bone during a core decompression. This can be done by injection of bone marrow concentrate from the patient into the drill hole of a core decompression. Results of this procedure have led to a very low rate of progression in a number of studies from Europe. The bone marrow concentrate contains a relatively high number of cells, known as stem cells. These stem cells have a high potential to make healthy bone in the diseased femoral head. In cases where the head has collapsed and is no longer spherical, various options include partial resurfacing of the joint with metal or a cartilage graft, rotation of the head to bring a stronger bony support into the area of weightbearing, or joint replacement. In general, the unifying goal of treatment of avascular necrosis of the femoral head is based on minimizing the risk of progression and making every effort to preserve the patient’s own hip joint.