Avascular necrosis

Question 1

What is avascular necrosis?

Answer 1

This is a failure of the blood supply to the end of a bone, resulting in ischaemic necrosis of the bone and bone marrow

Question 2

Who is most at risk of avascular necrosis?

Answer 2

Males
Ages 35-50

Question 3

What are the most commonly affected bones in avascular necrosis?

Answer 3

Head of femur
Bones of the wrist
Head of humerus

Question 4

What are some factors that predispose to avascular necrosis?

Answer 4

• Alcohol
• Corticosteroids, Bisphosphonates
• Connective tissue disorders
• Decompression (The bends)
• Sickle cell disease
• Infection
• Pregnancy
• Pancreatitis
• Radiation

Question 5

How can alcoholism and steroid abuse cause avascular necrosis?

Answer 5

Alcoholism and steroid abuse alter fat metabolism, which can result in mobilisation of fat into circulation, which can lead to ischaemia

Question 6

Describe the pathophysiology of avascular necrosis

Answer 6

Trauma or blood obstruction ->

Hypoxic heath of bone and marrow ->

Stimulation of periostial nociceptors + Resorption of bone ->

Bone pain + Osteochondritis dissecans ->

Sclerosis, locking and bone collapse

Question 7

How will avascular necrosis present?

Answer 7

This can be asymptomatic, with normal examination in early stages of disease
In 80% of cases, it is bilateral

Question 8

What investigations are required in avascular necrosis?

Answer 8

MRI (Early)
X-ray (Late)

Question 9

How will avascular necrosis appear on MRI?

Answer 9

The “Hanging rope sign” is a ater sign of femoral head AVN, showing patchy sclerosis of the weight bearing area of the femoral head with a lytic zone underneath, formed by granulation tissue from attempted repair

Question 10

What makes avascular necrosis reversible or not?

Answer 10

If the articular surface has not yet collapsed, the AVN can be reversed

Question 11

How is reversible AVN managed?

Answer 11

• Bisphosphates
• Core decrompression - Drilling to decompress the bone and prevent further necrosis
• Curettage and bone grafting
• Vascularised fibular bone graft

Question 12

How is irreversible AVN managed?

Answer 12

If the articular surface has collapsed, generally joint replacemet is required in the hip, knee or shoulder to control symptoms

Rotational osteotomy can be considered if less than 15% of the femoral head is damaged

Fusion can be considered in the wrist, foot and ankle