Avascular necrosis

Avascular necrosis (AVN), also called osteonecrosis or bone infarction, is

About 15,000 cases occur per year in the United States.[4] People 30 to 50 years old are most commonly affected.^[3] Males are more commonly affected than females.^[4]

Signs and symptoms

In many cases, there is pain and discomfort in a joint which increases over time. It can affect any bone, and for in about half of affected people, multiple sites are damaged.^[5]

Avascular necrosis most commonly affects the ends of long bones, such as the femur. Other common sites include the humerus (upper arm),^[6][7] knees,^[8][9] shoulders,^[6][7] ankles and the jaw.^[10]

Causes

The main risk factors are

Prolonged, repeated exposure to high pressures (as experienced by commercial and military divers) has been linked to AVN, though the relationship is not well understood.^[14][15]

In children, avascular osteonecrosis can have several causes. It can occur in the hip as part of

• 
  Radiography of total avascular necrosis of right humeral head. Woman of 81 years with diabetes of long evolution.
• 
  Radiography of avascular necrosis of left femoral head. Man of 45 years with

  AIDS

  .
• 
  Nuclear magnetic resonance of avascular necrosis of left femoral head. Man of 45 years with AIDS.
• 
  The intravertebral vacuum cleft sign (at white arrow) is a sign of avascular necrosis. Avascular necrosis of a vertebral body after a vertebral compression fracture is called Kümmel's disease.^[20]
• 
  Pathology of avascular necrosis, with a photograph of a cross-section of the involved bone at top left. The reactive zone shows irregular trebaculae with empty lacunae, and fibrosis of the marrow space.

Types

When AVN affects the scaphoid bone, it is known as Preiser disease. Another named form of AVN is Köhler disease, which affects the navicular bone of the foot, primarily in children. Yet another form of AVN is Kienböck's disease, which affects the lunate bone in the wrist.^[21]

Treatment

A variety of methods may be used to treat

Other treatments include core decompression, where internal bone pressure is relieved by drilling a hole into the bone, and a living bone chip and an electrical device to stimulate new vascular growth are implanted; and the free vascular fibular graft (FVFG), in which a portion of the fibula, along with its blood supply, is removed and transplanted into the femoral head.[25] A 2016 Cochrane review found no clear improvement between people who have had hip core decompression and participate in physical therapy, versus physical therapy alone. There is additionally no strong research on the effectiveness of hip core decompression for people with sickle cell disease.^[11]

Progression of the disease could possibly be halted by transplanting nucleated cells from bone marrow into avascular necrosis lesions after core decompression, although much further research is needed to establish this technique.^[26][27]

Prognosis

The amount of disability that results from avascular necrosis depends on what part of the bone is affected, how large an area is involved, and how effectively the bone rebuilds itself. The process of bone rebuilding takes place after an injury as well as during normal growth.^[23] Normally, bone continuously breaks down and rebuilds—old bone is resorbed and replaced with new bone. The process keeps the skeleton strong and helps it to maintain a balance of minerals.^[23] In the course of avascular necrosis, however, the healing process is usually ineffective and the bone tissues break down faster than the body can repair them. If left untreated, the disease progresses, the bone collapses,^[28] and the joint surface breaks down, leading to pain and arthritis.^[1]

Epidemiology

Avascular necrosis usually affects people between 30 and 50 years of age; about 10,000 to 20,000 people develop avascular necrosis of the head of the femur in the US each year.^{[citation needed]}

Society and culture

Cases of avascular necrosis have been identified in a few high-profile athletes. It abruptly ended the career of

• Sperm whale skeletons can show damage from avascular necrosis caused by decompression.^[35]

References