What is Perthes’ disease?
Perthes’ disease, also known as Legg-Calve-Perthes’ is a disorder affecting one or both hips. It most commonly affects children between the ages of 4 and 10 and is 4 times more common in boys. Perthes’ is usually self-limiting, however complications can last into adulthood so timely investigation and treatment is important.
The hip is a ball and socket joint in which the ball is the top (head) of the thighbone (femur) and the socket is located at the side of the pelvis. In Perthes’ disease, for reasons not yet fully understood the normal blood supply to the head of the femur is interrupted, preventing nutrients and oxygen getting to the bone. Without nutrients or oxygen the femoral head breaks down and collapses in a process called avascular necrosis. Following this new blood vessels form and bone regrows, and in most cases the hip joint heals (although this can take 2-3 years).
Although healing occurs, if the condition is not recognised, the shape of the femoral head may be affected long term. This compromises the joint as the ball and socket no longer fit together well, which may cause long-term pain and increase the risk of early onset arthritis.
The symptoms of Perthes’ disease usually come on gradually, and do not start after a traumatic event such as a fall. Most commonly the child limps due to a painful hip, which worsens with activity. The pain may also radiate to the thigh, knee, groin or buttock and can sometimes present just as knee pain without symptoms being felt in the hip. There may also be limited movement and stiffness on the affected side, and in more severe cases muscle wasting. In up to 15% of cases Perthes’ disease occurs in both hips, therefore symptoms may present on both sides.
What is the likelihood of Perthes’ disease?
Perthes’ disease is relatively rare, occurring in 1 in 10,000 children. It usually occurs between the ages of 4 and 10 and is 4 times more common in boys. Other risk factors include Caucasian ethnicity, delayed bone growth and short stature.
When a doctor suspects a child has Perthes’ disease, they will first take a history. This will include discussion of the symptoms, and some more general information about the child’s medical history and health. They will then examine the hip, looking particularly for pain and a reduced range of movement, and also observe the child walking.
X-rays are then used to confirm a diagnosis of Perthes’ disease. Due to the risk of the condition affecting both hips, the unaffected side is also X-rayed. If the diagnosis is not clear on these images, occasionally it may also be necessary to do an MRI.
The choice of treatment for Perthes’ disease is dependent on the age of the child, and also the severity of the condition as this can vary between individuals.
In children under 6, surgery is not usually required. They may undergo a period of bedrest, occasionally with the affected leg in a traction device to ensure its position is optimal while healing occurs. Following this, they begin to move the hip, strengthen the surrounding muscles and gradually increase weight-bearing activity under guidance of a specialist children’s physiotherapist. X-Rays are taken at regular intervals to ensure the joint is healing in the correct shape. During the healing process it is also advised to avoid high impact activities such as trampolines and bouncy castles.
For children over 6, treatment is more complex. In those with milder variants of Perthes’ disease, rest and physiotherapy may still be an option. However in more severe presentations, containment is required. This immobilises or reconstructs the hip in order to maintain the shape of the femoral head. It is achieved either by plaster cast/brace or surgery.
- Plaster casts/braces hold the legs apart and turned outwards and are usually worn for up to a year.
- Surgical procedures usually involve making a break through the top of the thigh bone and resetting it into a position that encourages the hip to heal in the correct shape. Following surgery, crutches are initially required. Following this a period of rehabilitation will be supervised by a specialist children’s physiotherapist.
In the long term, studies have not shown a significant difference in outcomes between children who wear a cast/brace and those who have surgery. The decision as to which treatment to have is made on an individual basis after discussions between the family and surgeon.
What is the Long Term Impact of Perthes’ Disease?
For children diagnosed with Perthes’ disease under 6 years old, the outcome is usually very good regardless of the treatment. This is because younger children have more potential for bone growth, and therefore the femoral head is more likely to heal into the correct shape.
In older children, and those with more complicated disease the femoral head may have some residual deformity even following treatment. Around 50% of these children will then go on to develop early arthritis and are likely to require hip replacement surgery by the time they are 50 years old.