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What is Perthes' disease?
Perthes' disease (also known as Legg-Calve-Perthes' disease) occurs in children when blood supply is disrupted to the top of the thighbone (femur), leading to pain and damage in the hip joint.
Perthes' disease is about five times more common in boys than girls and tends to occur in children between 2-12 years of age  .
The head or ball of the femur sits in the socket of the hip joint. The ball shape allows the leg to move and rotate within the joint.
In Perthes' disease, the blood supply to the head of the femur is interrupted or stopped. Why this occurs is unknown.
Without blood supply, the bone tissue becomes damaged and begins to die. This leads to a flattened, abnormally-shaped head of the femur that does not fit well inside the socket, which can result in inflammation, pain and a reduced ability to move the leg, particularly turning it inwards.
The blood supply usually restores itself, although this can take around 2-5 years. During this time, the bone is soft and prone to damage. As the blood supply is restored, the head of the femur begins to regenerate; however, it can develop in an abnormal shape, leading to further problems with the hip.
Perthes' disease can run in some families, although this only occurs in a relatively small percentage of cases.
Signs and symptoms
Symptoms of Perthes' disease tend to develop gradually and include:
- A limp in the affected leg;
- Pain that may appear to be coming from the hip, groin, knee or thigh, and;
- Stiffness and reduction in the range of motion in the affected hip.
Eventually, Perthes' disease can also lead to:
- Weakness of the thigh muscle, and;
- Shortening of the affected leg.
Around one in five children with Perthes' disease will be affected in both legs  .
It is important to note that limping in children can be caused by a range of conditions, including some that require immediate medical attention. Fever can be a sign of serious illnesses, so if your child has a fever or seems generally unwell and develops a limp at the same time, promptly seeking medical assessment is important. Perthes' disease does not cause fever.
Methods for diagnosis
When Perthes' disease is being diagnosed, it is important that other causes of limp are ruled out.
Your doctor may ask about:
- Pain and symptoms associated with the symptoms;
- Anything that may have caused an injury, and;
- Any recent infections or illnesses.
A complete physical examination can include:
- Measuring the child's temperature to detect any fever;
- Looking for masses or pain in the abdomen, near the bellybutton or in the scrotum area of boys;
- Looking for bruising and other signs of trauma;
- Measuring leg length;
- Examining the bones and joints to test their function (including the legs, hips and spine), and;
- Assessing gait (how a child walks) and other movement.
The child may be asked to walk or perform certain movements so that their ability to move the affected hip may be assessed.
Further tests may be recommended to investigate possible underlying health conditions. Blood tests may help to rule out other causes of limp such as infection or inflammatory conditions.
X-rays are commonly used to view bones and joints. If further investigation is required, CT, MRI and ultrasound scans may be recommended. A bone scan may be used to help identify areas of the bone that are damaged.
Types of treatment
Treatment will vary from child to child. Older children, especially girls, are more likely to require more complex treatment.
There is no way to restore blood supply to the femur, so treatment is aimed at:
- Relieving pain or discomfort;
- Keeping damage to the head of the femur to a minimum;
- Promoting healthy regrowth of damaged bone by keeping the head of the femur inside the hip socket, and;
- Helping the child maintain mobility and movement in their hip joint.
Treatments may include:
- Pain-relief medications such as ibuprofen and paracetamol to help manage pain;
- Rest and avoiding strenuous physical activity to prevent further damage to the bone;
- Physiotherapy and exercises to help keep the hip joint flexible. Swimming is a good activity for children with Perthes' disease;
- Crutches, to reduce the amount of weight the child places on the joint;
- Splints, plaster casts or braces that put the legs into a wide-legged stance to help to keep the head of the femur in the correct position in the hip joint, and;
Surgery is generally only recommended for more severe cases of Perthes' disease, when other treatments are not possible or have failed to keep the head of the femur in the hip socket.
Surgeries that may be recommended include:
- Tenotomy, in which the tendon of a muscle that has contracted and become too tight is cut, so that it becomes longer;
- Femoral osteotomy, in which the femur is remodelled so that the head fits into the hip socket more securely. A plate and metal screws are inserted to hold the bone into position while it heals, and;
- Pelvic osteotomy, in which the hip socket (acetabulum) is reshaped so that the head of the femur fits into the socket more securely. Metal screws are inserted to hold the bone in position while it heals.
While most children who have Perthes' disease recover well, if the head of the femur does not regrow correctly, it can increase the risk of conditions such as arthritis of the hip earlier in life than generally occurs. This may require a hip replacement.
In most cases, the blood supply to the top of the femur gradually restores itself and the head of the femur regrows into a normal shape so that the hip joint functions well. However, this can take a number of years and during this time, the bone can be soft and fragile, so it is important to follow treatment recommendations to minimise damage.
Perthes' disease cannot be prevented; however, following treatment recommendations can help to limit the damage caused to the affected leg while the head of the femur recovers.