Osteonecrosis

Question 1

What is it?

Answer 1

Ischaemic bone necrosis of all types

Ischaemia- bone marrow cells die within 12 hours followed by bone cells (osteoblasts etc.) in 12-24hrs

Question 2

What are the different types of osteonecrosis?

Answer 2

Osteonecrosis of long bones

• bone infarction
• involves trabecular bone and bone marrow in medulla
• cortex has different blood supply

Osteonecrosis in the epiphysis

• called avascular necrosis
• can involve cortex also

Question 3

What are the causes?

Answer 3

Interrupted arterial supply e.g. fractures

Interrupted venous drainage and retrograde arterial stoppage e.g. thrombosis

Question 4

What are the risk factors?

Answer 4

Fracture e.g. NOF/Scaphoid
Idiopathic e.g. Perthe's disease
Bone marrow infiltration e.g. malignancy
Alcohol abuse
Cushings/exogenous steroid/chemo
Infection e.g.SA

Question 5

Which bones are commonly affected?

Answer 5

Head of femur
Proximal scaphoid
Lunate
Body of talus

Question 6

What are the symptoms?

Answer 6

Well advanced at presentation
Pain
Stiffness
Swelling
In a joint but can be over bone

Question 7

What are the investigations?

Answer 7

XR

• Sclerosis
• Flattening
• Subchondral radiolucent lines- crescent sign
• Collapse of cortex

Can take 6 months for changes to show

MRI can show earlier

Question 8

What is the treatment?

Answer 8

Treat underlying cause
Prevent complications- stop fracture by weight relief or splint
Surgery where needed