Introduction
Perthes disease is a condition that affects the hip joint in children between 3 and 11 years old. The hip joint is made up the round head of the thigh bone, also known as the femoral head, which is shaped like a ball to fit comfortably into the cup shaped socket of the pelvis, also known as the acetabulum.
Perthes disease causes the femoral head to collapse and regrow. This happens in three stages over a period of 18 months to 2 years.
First months to 1 year: blood supply to the femoral head is interrupted. This causes the joint to become inflamed, stiff, and painful. Parts of the femoral head start to die and collapse. This gives the bone a misshapen appearance on x-rays.
1 to 3 years: the body absorbs the dead bone tissue and starts to grow new bone to replace it. The femoral head is soft as it regrows, meaning there is a risk of it becoming misshapen. The hip joint can be painful, and your child may walk with a limp.
1 to 3 years: the bone starts to harden and become round again.
The cause of Perthes disease is unknown. In most cases, it only happens in one hip joint.
Signs and symptoms
General symptoms of Perthes disease can include:
- an occasional limp in stage 1
- general knee pain
- worsening pain and increased limping as time goes on
- pain in the knee, thigh, or groin on movement or when putting weight through the leg
- decreased movement
- thinner thigh muscles on the affected leg
- uneven leg length, with the affected leg may becoming shorter.
Signs and symptoms of the disease can be difficult to detect, especially in the early stages. Symptoms can also be mistaken for general aches and pains from growing and physical activity.
Diagnosis
Your child’s doctor will refer them to an orthopaedic (bone and muscle) specialist to diagnose Perthes disease. They will take a medical history for your child, do a physical exam and scans including x-ray and MRI.
Treatment
The treatment your child’s doctor prescribes will depend on their age and how severe the disease is.
Because Perthes disease heals on its own over time, the goal of treatment is to:
- reduce pain
- increase movement
- reduce the risk of changes in shape to head of the femur.
Most children with Perthes disease will recover completely. It can take 2 - 5 years for the body to repair the damaged bone. If the femoral head is not seriously deformed, your child’s hip should recover and function normally again. If the femoral head grows back deformed, your child may develop constant stiffness and early arthritis in the hip.
Treatment for younger children (3 to 7 years)
In mild cases, children usually do not need immediate treatment.
Pain and stiffness can be treated by resting and reducing the amount of weight your child puts on their hip joint when moving. Your child will need to limit high-impact activities like running and jumping and replace them with gentle, low impact activities like swimming and riding a bike.
Your child will need regular check-ups with their doctor to monitor their hip joint growth.
Treatment for older children (7 to 11 years)
Bones begin to set in place as your child gets older, so treatment of Perthes disease in older children may need a more detailed assessment by their doctor.
Your child may need to use crutches or a wheelchair for up to a year to help with resting the joint. Supporting their body weight with equipment will also help to keep the femoral head snugly in the hip socket. If your child has pain or limited movement in the hip, their doctor may decide to use a brace or plaster cast to keep the hip joint in place.
Surgical treatment
Surgery may be needed for children who have a more severe case of Perthes disease, including cases where the femoral head has become misshapen and cannot be supported by a bast or brace.
The aim of surgery is to securely hold the femoral head in the socket. This will promote healing and good hip movement.
Management
Physical activity
Treatment of Perthes disease can be a long and slow process. Your child may be frustrated and anxious about not being able to exercise and play as much at an age where activity is important for socialisation and growth.
It is important to support your child to focus on low impact, gentle exercise and adapting other sports and activities to be gentler for their hip joint.
Speak to your child’s doctor about appropriate exercise and movement, and how to find other activities they can enjoy without impacting recovery.
Long term outlook
Most children will recover fully from Perthes disease, but it may take up to 5 years for the bone to return to normal. Length of recovery will usually depend on how old your child was when the disease started, and how much of the femoral head has been affected. Early diagnosis and treatment mean there is a higher chance of full recovery.
Children who have recovered fully from Perthes disease can still develop hip problems later in life. Your child’s orthopaedic specialist will follow-up with them as they grow to check for any issues that may develop.