Perthes’ disease is a rare childhood disorder that affects the hip. It is also know as Legg-Calve-Perthes’ disease after the three doctors who first described it. It occurs when the blood supply to the femoral head (the ball of the hip joint) is temporarily disrupted leading to softening and collapse of the femoral head. Without an adequate blood supply the bone of the femoral head dies (avasular necrosis). Over time the blood supply returns and the hip heals however during this time there is a risk that the hip will become deformed and lead to problems in the future. This process usually takes on average 2 years.
Although Perthes’ disease is a well-known hip condition in children, the exact cause is not known.
Who gets Perthes’ disease?
The condition affects approximately 1 in every 1200 children. Children aged 3 – 12 years of age can get it however 4-8 years of age is the most common age of presentation. Boys are five times more likely to be affected than girls. There is evidence of a genetic component so it sometimes runs in families. In 10% of cases it can affect both hips but rarely at the same time.
What are the symptoms?
Symptoms may appear suddenly or may appear slowly over a period of weeks.
A limp - this is sometimes the earliest sign noticed by parents and is most obvious during play and sporting activities.
Pain - in the hip and groin that is worse when the child is more active. Sometimes pain may be felt in the knee only and this is known as “referred pain”.
Stiffness – the child may complain of stiffness in the hip joint and a lack of movement compared with the other side.
Thinner leg - In time, the muscles of the thigh of the leg can become thinner (known as muscle wasting) as a result of decreased use.
Shorter leg – in time, if deformity develops, one leg may be shorter than the other
The diagnosis is made by a doctor with a combination of physical examination of the affected hip and an x-ray of both hip joints. Occasionally further tests including an MRI scan or a bone scan may be needed to make the diagnosis.
Doctors may also wish to perform blood tests to out rule any infection in the hip joint, but there is no blood test for Perthes’ disease itself.
Stages of Disease
A child with Perthes’ disease can expect to have several x-rays taken over a two-year period, or longer. These x-rays help doctors assess how the hip will remodel and identify any potential problems for the child’s hip. In general the appearance on hip x-rays will worsen during the early stages of treatment before gradual improvement is seen as the bone heals.
There are four stages of Perthes’ disease seen on x-ray
Initial stage – this is when the blood supply to the hip has been disrupted and the bone begins to die. It is at this stage when most children develop limp and pain in the affected hip.
Fragmentation stage – the blood supply has returned and the dead bone is removed from the hip and new softer bone is formed.
Reossification stage – the softer bone is replaced by harder more mature bone.
Healing and remodeling – the new bone has formed and the hip continues to remodel any deformity until the child has reached skeletal maturity
What is the treatment?
The aim of treatment is to
Relieve the child’s pain
Promote the natural healing process of bone
Keep the femoral head well positioned in the hip socket
Maintain the movement of the hip joint
There are many treatments for Perthes’ disease, and your doctor will take into consideration several factors before deciding on a method of treatment. The type of treatment depends on:
The age of the child
The degree of damage to the femoral head (the ball of the hip joint)
The stage of disease at which the child is diagnosed
Treatment varies from simple observation in outpatients to surgery depending on these factors.
If the hip is in good position and pain is controlled with simple painkillers, the child will be seen regularly in the outpatient department for x-rays to monitor the hip over time. Occasionally physiotherapy is needed to maintain movement and the child may have to reduce certain activities during this process. The child will be followed until the hip has healed
If the child has significant hip pain, muscle spasm and reduced movement, they may be admitted to hospital for bed rest and simple traction. Traction helps reduce the pain in the hip by resting the joint. Once the pain has settled, they will be followed in the outpatient department as above. They may occasionally need crutches to walk when they first leave hospital but not in the long term.
Surgery is considered in older children who develop Perthes’ disease after the age of 8 and those who have extensive involvement of the femoral head. Children whose femoral head is no longer well positioned in the hip socket may also require surgery to improve the shape and function of the hip as it heals. There are many different surgical procedures, which may be carried out, and the surgeon will discuss the best option depending on the child’s individual problem.
In most cases the long term outcome is good for Perthes’ disease with the hip healing to normal or near normal appearance and children grow into adulthood without further hip problems.
The main concern is that during the disease process the femoral head becomes deformed and flattens. It can end up looking more like a rugby ball than a football. This can lead to stiffness of the hip in the long term and the development of arthritis at an early age (30-40 years of age). Occasionally a total hip replacement may be needed at this point if arthritis has developed.
Factors that are associated with a poor outcome are
Age: onset of symptoms after the age of 8 years is associated with a worse outcome, as the child does not have the same remodeling ability of their hip as younger children.
Gender: though more common in boys, Perthes’ disease often affects girls more severely leading to an increased chance for a poorer outcome. This is because girls tend to finish their growing sooner than boys and thus have less remodeling ability
Severity of the disease: which is judged on the x-rays taken of the child’s hip.