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Perthes disease

Mate pona papatoiake

Diagram showing avascular necrosis, or Perthes disease, in the hip joint

Perthes disease is a condition that affects the upper end, or head of the thigh bone (femur), where it forms one part of the hip joint. It's also known as avascular necrosis.

It happens in tamariki (children) when, as their thigh bone is growing, the round head of the bone (the ball that fits inside the hip socket) softens, flattens and then gradually re-forms. It's caused by a lack of blood supply to the bone, but we do not know why it happens.

Perthes disease happens much more often in boys than in girls. It usually develops between the ages of 4 and 10 years, when the ball is particularly vulnerable to its blood supply being cut off.

Watch this video to learn more about Perthes disease.

Symptoms of Perthes disease

Perthes disease develops slowly over many weeks. It usually only happens in one hip.

The tamaiti (child) will usually have a limp. They may also have pain in their hip or knee, but not all tamariki children do. Some will have muscle spasms and stiffness in the hip.

The symptoms of Perthes disease usually last from 18 months to two years.

In about one in eight cases the other hip is also affected, either at the same time or later. If your child complains about their good leg aching, tell your doctor.

Diagnosing Perthes disease

Doctors may suspect Perthes disease if a tamaiti child limps for more than 48 hours. Your tamaiti will need X-rays to confirm the diagnosis – Perthes disease cannot be diagnosed by blood tests.

The younger the tamaiti is when Perthes is diagnosed, the better the outcome.

Treating Perthes disease

Many tamariki with Perthes disease simply need to be watched, have regular X-rays, and avoid some physical activities. Sometimes they will need a period of bed rest, with no physical activity. Some tamariki may also need to use crutches or a wheelchair, to avoid putting weight on the affected leg.

Occasionally a tamaiti will need surgery to protect the ball of the thigh bone from becoming deformed.

Tamariki can, and should, go to school as normal, but they may have to avoid some physical activities. They may need to do this for up to four years, as their body replaces the soft, fragmented bone with strong new bone.

How Perthes disease affects your child's future

Perthes is a self-limiting disease and will eventually get better, even though it may take a long time. Most tamariki will eventually have no pain in their hip and a good range of movement. A few will be left with some stiffness and pain.

Because we do not know exactly what causes Perthes disease, we cannot always predict the results. But because the outcome is usually worse if treatment is delayed (even if the treatment is just to avoid some activities), or if a child is diagnosed after the age of 8, it's very important to diagnose it early.

Written by HealthInfo clinical advisers. Last reviewed June 2022.

Sources

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Review key: HIBOW-85151