Perthes' Disease

What is Perthes' disease?

Perthes' disease is a condition of the hip which occurs in some children. It was first described in 1910 by three separate doctors and so it is sometimes called Legg-Calve-Perthes Disease after each of these doctors.

What happens in Perthes' disease?

   

The problem occurs in the femoral head. This is the rounded top of the femur (the thigh bone) which sits inside the acetabulum (the hip socket). Something happens to the small blood vessels which supply the femoral head with blood. So, parts of the femoral head lose their blood supply. As a result, the bone cells in the affected area die and so the bone 'softens', and can fracture, break up, and become distorted. The severity can vary.

It is not clear why this blood vessel problem occurs in the femoral head. It is not due to injury, or to a general blood vessel problem. A child with Perthes' disease is usually otherwise well.

Over several months the blood vessels regrow, and the blood supply returns to the 'dead' bone tissue. New bone tissue is then laid down and the femoral head regrows and remodels over several years. This is similar to how bone reforms and remodels after any 'normal' fracture or break to a bone, but takes longer.

Who gets Perthes' disease?

About 1 in 10,000 children between the ages of 2 and 15 years develop Perthes' disease each year. It occurs most commonly between the ages of 4 and 8 years. About four boys are affected for every one girl. It usually only occurs in one hip, but in about 1 in 8 cases it occurs in both hips (at separate times).

What are the symptoms of Perthes' disease?

Symptoms tend to develop gradually and can include:

• Limp. This may gradually become worse over a few weeks. However, the limp is often painless.
• Pain in the hip and groin area. The pain may radiate to the knee or thigh (referred pain). In some cases, pain in the knee is the first symptom.
• Stiffness and reduced range of movement of the affected hip.
• In time, the affected leg may become slightly thinner (wasted) as it is not used as much as the other leg.

How is Perthes' disease diagnosed?

A GP will normally refer a child with suspected Perthes' disease to a specialist. Tests which may be done include:

• X-rays of the hip. X-ray pictures can show a femoral head which is broken or damaged. A typical appearance is a 'flattened' femoral head when it should normally look rounded in the hip socket. However, the X-ray can be normal in the early stages of the disease before the 'softened' bone breaks. An X-ray every few months can show the progress of the breakdown, and then healing as new fresh bone is made and gradually 'remodelled'.
• Bone scan. This may be done to confirm Perthes' disease in the early stages when the X-ray picture is normal, but symptoms suggest that Perthes' disease is the problem.
• An MRI scan or other tests are sometimes used to asses the extent of the damage.

What is the treatment for Perthes' disease?

The aim of treatment is to promote the healing process and to ensure that the femoral head remains well seated in the hip socket as it heals and remodels. Treatments advised can depend on the age of the child and the severity of the condition. Treatments may include 'observation', bed rest and crutches, a plaster cast or special leg brace, or surgery.

Observation and conservative treatment
Until recently most children with Perthes' disease were treated with a plaster cast or brace, or surgery. However, it is now known that at least half of cases heal well without any treatment, particularly children aged five and under, and milder cases. So, in some cases a specialist may simply review the child every now and then to check that the femoral head remains in the right place as it heals. Advice may include to encourage swimming (to keep the hip joint active in the full range of movements), but to avoid heavy impact on the joint such as running or jumping.

Bed rest and/or crutches
May be needed for a short time at first if symptoms are bad.

Plaster casts or a special brace
These may be considered in more severe cases or in older children. The aim is to keep the femoral head well positioned in the hip socket. So these devices keep the leg slightly abducted (slightly pointing outwards). The child can walk and weight bear in these devices but they may need to be worn for many months.

Surgery
An operation may be considered in severe cases to keep the femoral head in place whilst it heals.

What is the outcome (prognosis)?

In most cases the femoral head regrows and remodels back to normal or near normal. The function of the hip then returns to normal. It can take two or more years for this to occur after the condition first develops. The main concern is that the femoral head may not reform properly which occurs in some cases. In this situation a permanent deformity may remain and cause permanent stiffness and/or premature arthritis in the joint.

Factors which may affect outcome include:

• Age. The younger the child when the condition develops, the better the chance of a good outcome. This is because they have longer to grow and this gives more time for the hip to remodel before the child finishes growing. Children who develop Perthes' disease after about the age of 8-9 have the highest risk of persisting problems.
• Gender. For any given age when the condition develops, boys have a better chance of a good outcome than girls. This may be because girls tend to finish growing a bit earlier than boys.
• Severity. The more severe the condition (which can be judged by the X-ray pictures of the hip), the greater the risk that problems will persist.

Further help and information

Perthes Association
PO Box 773, Guildford, GU1 1XN
Helpline: 01483 306637    Web: www.perthes.org.uk

Perthes Association Scotland
29 Leander Crescent, Deanpark Estate, Renfrew, PA4 0XB
Tel: 0141 885 0001 or 0141 561 0001

© EMIS and PIP 2004   Updated: June 2004   Review Date: July 2005   CHIQ Accredited