What is Perthes Disease?
Perthes disease, also called Legg-Calvé-Perthes disease, is a rare condition of the hip that affects only children. It develops when there is a temporary loss of blood supply to the rounded head of the femur (thigh bone) – the “ball” part of the “ball and socket” hip joint.
Blood supply is important for bone, as it delivers oxygen and nutrition to the bone. Lack of blood supply causes bone cells to die. This process is called osteonecrosis, or avascular necrosis. The ball part of the femur can eventually collapse when the bone is weakened, if the blood supply is interrupted long enough. When the blood supply returns to the ball of the femur, the bone can improve its strength, but the shape of the femur can be permanently distorted.
How common is Perthes disease?
Perthes disease is rare, afflicting about one in 10,000 children. Perthes disease usually affects children between the ages of four and eight years, but the range can extend to between two and 12 years old. Both hips are affected in up to 15% of children.
Who gets Perthes disease?
Perthes disease is five times more common in boys than in girls.
Perthes disease often affects children who are very active, even athletic. Children tend to be smaller than average for their age. The disease is also more common in Asians, Eskimos and Caucasians. There is a much lower incidence rate in Native Americans, people with African heritage, Polynesians, Blacks and in Australian aboriginals.
Exposure to secondhand smoke may also increase your child's risk of Perthes disease, although the exact reasons why are not known.
What are the causes of Perthes diseases?
Technically, the ball of the femur dies because the blood supply to it is temporally cut off. The reason(s) why this happens are not well understood. There is some evidence that genetics may play a role, but more study is needed. The lack of a steady blood supply to the ball of the femur causes a sequence of events. First, bone cells in the head of the femur die. Next, weakness in this area causes the head of the femur to eventually collapse (usually occurs over a two-year period), and lose its roundness – this is called “fragmentation.” The damaged bone tissue is then absorbed by the body. When the blood supply returns, new bone tissue beings to grow and take the shape of a new femur head. This stage can last a few years. Lastly, the bone heals into its final shape, though this final shape is not always a perfect, round head.
How well the head of the femur heals into a rounded shape depends on the extent of the bone collapse and how old your child is at the time that the disease process started. Bone tends to reshape better in younger children and improves as the child grows.
What are the symptoms of Perthes disease?
The first symptoms of Perthes disease are usually a limp or a change in the way your child walks or runs. Your child may not even notice or feel these changes. You, as the parent, may be the first to see them while watching your child play.
Other symptoms include:
- Pain in the hip area, or in the groin, thigh, or even the knee.
- Irritation and inflammation in the hip area that may result in muscle spasms.
- Pain with activity; relief when rest.
- Stiffness or decreased motion in the hip joint
Pain may occur “on and off” for months. Pain occurs without an injury associated.
Some children don’t feel much or any pain at all. Perthes disease might not be discovered until an X-ray is taken due to a fall or other injury and the image shows your child is affected by this condition.
If your child has any of the above symptoms and you suspect he or she may have Perthes disease, it is important to contact your healthcare provider, who can begin to investigate.