Avascular necrosis

Avascular necrosis
Other names	Osteonecrosis,[1] bone infarction,[2] aseptic necrosis,[1] ischemic bone necrosis[1]
Femoral head showing a flap of cartilage due to avascular necrosis (osteochondritis dissecans). Specimen removed during total hip replacement surgery.
Specialty	Orthopedics
Symptoms	Joint pain, decreased ability to move[1]
Complications	Osteoarthritis[1]
Usual onset	Gradual[1]
Risk factors	Bone fractures, joint dislocations, high dose steroids[1]
Diagnostic method	Medical imaging, biopsy[1]
Differential diagnosis	Osteopetrosis, rheumatoid arthritis, Legg–Calvé–Perthes syndrome, sickle cell disease[3]
Treatment	Medication, not walking on the affected leg, stretching, surgery[1]
Frequency	~15,000 per year (US)[4]

Avascular necrosis (AVN), also called osteonecrosis or bone infarction, is death of bone tissue due to interruption of the blood supply.^[1] Early on, there may be no symptoms.^[1] Gradually joint pain may develop, which may limit the person's ability to move.^[1] Complications may include collapse of the bone or nearby joint surface.^[1]

Risk factors include bone fractures, joint dislocations, alcoholism, and the use of high-dose steroids.^[1] The condition may also occur without any clear reason.^[1] The most commonly affected bone is the femur (thigh bone).^[1] Other relatively common sites include the upper arm bone, knee, shoulder, and ankle.^[1] Diagnosis is typically by medical imaging such as X-ray, CT scan, or MRI.^[1] Rarely biopsy may be used.^[1]

Treatments may include medication, not walking on the affected leg, stretching, and surgery.^[1] Most of the time surgery is eventually required and may include core decompression, osteotomy, bone grafts, or joint replacement.^[1]

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]