Case history: avascular necrosis

PUBLISHED : Tuesday, 05 February, 2013, 12:00am
UPDATED : Monday, 18 February, 2013, 5:00pm

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.

Alcohol and long-term steroid use are also known culprits. Brockwell explains that both substances affect fat metabolism and can lead to clotting of small blood vessels. He says that steroids are a common component in traditional medicine, and long-term use can give rise to AVN.

In many cases, however, the cause of AVN is unknown. Chan fell into this category.

Brockwell says that mild cases of AVN can resolve on their own once blood supply is re-established. But once the bone dies and collapses, the only option facing patients is a total hip replacement. In such an operation, the entire head and neck of the femur are removed and replaced with an artificial ball and socket joint.

It [BHR] uses a more durable material for the artificial ball and socket joint than conventional ones, and presents less risk of joint dislocation

Brockwell says that although such a method works well, it lasts only about 20 years as the artificial implants wear out. Furthermore, the range of motion for the hip is not as wide as for the natural and undamaged hip, and the hip joint is at risk of dislocation.

Hence, young patients like Chan are often reluctant to undergo hip replacement surgery because they face the high possibility of having to do it again in 10 or 20 years' time.

Chan refused the surgical option and tried to manage his pain with analgesics and by minimising his activity. Three years after the onset of AVN in his left hip, Chan was diagnosed with AVN in his right hip, too.

In 2003, Chan chanced upon a health forum that introduced a new type of therapy for AVN sufferers. Called Birmingham Hip Resurfacing (BHR) surgery, the method removes only the damaged bone and conserves more natural bone compared to the traditional method. It uses a more durable material for the artificial ball and socket joint than conventional ones, and presents less risk of joint dislocation.

Brockwell says retaining more natural bone gives rise to a greater range of motion and better function. He says this is especially important for Asians, who are more likely to squat or sit on the floor, which BHR enables one to do.

Studies show that patients who undergo BHR walk 10 per cent faster, have a higher level of sporting activity and a lower mortality rate at six years after the hip surgery than those who undergo traditional hip replacement, Brockwell says.

Although the longevity of the BHR joint compared to the conventional hip replacement surgery is unknown, the promise of better function was enough to sway Chan. The following year, Chan underwent BHR for his left hip. He was discharged from the hospital four days later and returned to sports in six months. In 2006, Chan underwent BHR for his right hip.

He reports a better range of motion in his hips than before AVN struck. "Not only can I return to my original duties, I run four kilometres each day and go hiking regularly."