Frequently Asked Questions
IPSG members weigh in on parent’s questions.
What causes Perthes?
On the most basic level, Perthes is caused by a temporary loss of blood flow to the ball of the hip joint, but the reason for that loss of blood flow isn’t known. Research associations have been made to family history, injury, clotting diseases, ADHD, and second hand smoke exposure; but the exact cause of Perthes remains unknown.
How long will it last?
The initial symptoms of Perthes can last months to years, but the effects can be life long. The symptoms of Perthes aren’t consistent. Some patients will have days or weeks at a time with little pain and minimal limp; however, for some time periods children will have more severe symptoms. The initial, active part of Perthes lasts 2 to 4 years.
Why isn’t my child supposed to run or jump?
Some children will be recommended to avoid running and jumping activities depending of the severity and stage of their Perthes. The femoral head or ball of the hip joint becomes soft like play dough and can become misshapen. The thought is that the increased forces from running and jumping can cause the femoral head to change shape.
What is perfusion MRI?
Perfusion MRI (magnetic resonance imaging) is an imaging study without radiation that evaluates the blood flow into the ball of the hip joint (femoral head). Depending on the age of the child, sedation or anesthesia may be required to get this test as the child must lie still for 30-45 minutes. Our study group believes that the perfusion MRI helps give an estimate of disease severity to help determine treatment.
What should I expect if my child has hip surgery involving the bone?
This of course depends on the child, the doctor, and the disease. Here are some generalized expectations that can vary widely.
The children with osteotomies tend to spend one to three nights in the hospital. They may or may not require a cast after surgery. If they are casted, then it is usually for 6 weeks. Most children take oral pain medicine for about a week after surgery. They are typically out of school for one week. Their doctor usually will want to see them post operatively around 1-2 weeks and again at 6 weeks. They will be intermittently followed with visits and x-rays until maturity. Your child will have limited weight bearing for at least 6 weeks and sometimes up to 6 months. They will typically need a lesser surgical procedure for the removal of the metal implant 6-12 months down the road.
Will my child play sports again?
Yes. Almost all children with Perthes will remain physically active. In fact, physical fitness is key to long term health of the hip. However, many doctors may recommend a period of time when the child should avoid high impact sporting activities. Some families choose to limit certain activities, or even change sports altogether, if the patient experiences too much discomfort with the sport.
What is a Petrie cast?
A Petrie cast is a cast on each leg from the thigh to the ankle with a bar in between holding the legs widely apart. This cast is typically placed in the operating room with the child under anesthesia. It is commonly done in conjunction with an injection into the hip joint called an arthrogram. This helps the surgeon better evaluate the hip. A release of a tight muscle in the thigh is also commonly done at the same time. The casts are usually maintained for 6 weeks. During this time the mobility of the child is limited to using a wheelchair and to a lesser extent a walker.
What is the risk that it will happen to the other hip?
The best studies on Perthes list less than 15% as the risk of developing Perthes in the other hip. It depends a bit on the age at which the first hip develops disease. Younger children may be at greater risk of the developing the disease in the other hip than older children. The other hip can develop the disease many years after the diagnosis of the initial hip.
How can I help?
There is still a long way to go in understanding and treating Perthes disease, and support and help from all families is important.
The various ways to help involve:
- Enrolling your child in a study and stay in the study.
- Actively share information about IPSG.
- Donate to IPSG to support research.
- Share your experience.
- Visit and Like us on Facebook, and promote our page.
Do you have an unanswered question?
The International Perthes Study Group wants to hear from you! Contact us with any additional Perthes questions. Please remember each child is different and treatment as well as progression is specific to each case. The best way to ensure a positive outcome is through the expertise of a pediatric orthopaedic surgeon.