Avascular necrosis (AVN) is defined as cellular death of bone components due to interruption of the blood supply. The bone structures then collapse, resulting in pain, loss of joint function and long-term joint damage. AVN is also known as osteonecrosis, aseptic necrosis, and ischemic bone necrosis.
AVN usually involves the epiphysis (end part of a long bone), such as the femoral and humeral heads and the femoral condyles, but small bones can also be affected. In clinical practice, AVN is most commonly encountered in the hip.
Most available data regarding the natural history, pathology, pathogenesis, and treatment of AVN pertains to femoral head necrosis.
AVN is associated with numerous conditions. Patients taking corticosteroids and organ transplant recipients are particularly at risk of developing AVN. AVN of the jaw has been described in patients taking bisphosphonates and, more recently, denosumab.
For full discussion of this entity, see Bisphosphonate-Related Osteonecrosis of the Jaw.
For diagnosis, plain radiography is the most appropriate initial imaging study, although findings are unremarkable in the early stages of AVN.MRI is the most sensitive and specific imaging modality. See Workup.
Early diagnosis and appropriate intervention can delay the need for joint replacement. However, most patients present late in the disease course. Without treatment, the process is almost always progressive, leading to joint destruction within 5 years. See Treatment.
For patient education information, see Avascular Necrosis (Aseptic Necrosis or Osteonecrosis).