Case history: avascular necrosis

Mr Chan was an active 30-year-old fireman who had to meet the gruelling physical demands of his job. But in 1997 a deepening pain in his left hip eventually left him unable to walk for more than five minutes without resting.

Walking up and down stairs, getting in and out of vehicles and any other activity where he had to bend at the hip became excruciatingly painful. Aware of his discomfort, his work supervisor gave him a desk job to minimise his physical activity and pain.

An orthopaedic specialist diagnosed Chan (whose name has been changed for reasons of patient confidentiality) as suffering from avascular necrosis, or AVN, which is a common cause of hip joint damage in Asians.

Avascular necrosis is a condition in which the bone dies because it isn't getting enough blood. It commonly afflicts the shoulder and hip joints, but can also affect other large joints like the knee, elbow, ankle and wrist.

According to Dr Jason Brockwell, a specialist in orthopaedics and traumatology, the hip joint is particularly susceptible to AVN because the head of the thigh bone, or femur, is a cul de sac when it comes to blood supply with only one route for the blood to travel in and out. Hence, if the blood supply to the femoral head is reduced or interrupted, there is no alternative blood supply.

Although the cause of AVN is a disrupted blood supply, the cause for the disruption is not always clear. Trauma or injury of some kind can sometimes precede AVN, as can radiotherapy and diseases such as sickle-cell disease, atherosclerosis, gout and diabetes.