Avascular necrosis (AVN) may be defined as death of bone tissue secondary to loss of the blood supply. This leads to bone destruction and loss of joint function. It most commonly affects the epiphysis of long bones such as the femur.

Causes

• long-term steroid use
• sickle cell
• connective tissue disease
• chemotherapy
• alcohol excess
• trauma

Features

• initially asymptomatic
• pain in the affected joint

Investigation

• plain x-ray findings may be normal initially. Osteopenia and microfractures may be seen early on. Collapse of the articular surface may result in the crescent sign
• MRI is the investigation of choice. It is more sensitive than radionuclide bone scanning

Management

• joint replacement may be necessary