What is Perthes disease?
Perthes disease is a rare childhood disorder that affects the hip. It happens when the blood supply to the round head of the femur (thigh bone) is temporarily interrupted. Without an adequate blood supply, bone cells die, a process called avascular necrosis.
Although the term “disease” is still used, Perthes is actually a multifaceted process of stages that can last numerous years. As the condition progresses, the weakened bone in the head of the femur (the “ball” of the “ball” joint in the hip) gradually begins to collapse. Over time, the blood supply to the head of the femur returns, and the bone begins to grow again.
Treatment for Perthes emphasizes helping the bone grow back into a more rounded shape that still fits into the hole of the hip joint. This will help the hip joint to move normally and prevent hip problems in adulthood. The long-term prognosis for offspring with Perthes is good in most cases. After 18 to 24 months of treatment, most children return to their daily activities without major limitations.
Perthes disease, also known as Legg-Calve-Perthes
What causes perthes disease?
Technically, the ball of the femur dies because the blood supply is temporarily cut off. The reasons for this are not well understood. There is some evidence that genetics may play a role, but more studies are needed. The lack of a constant supply of blood to the ball of the femur causes a sequence of events. First, the bone cells in the head of the femur die.
Then weakness in this area causes the head of the femur to eventually collapse (usually over a two-year period) and lose its roundness; This is called “fragmentation”. The body then absorbs the damaged bone tissue. When the blood supply returns, new bone tissue begins to grow and takes the shape of a new head of the femur. This stage can last a few years. Finally, the bone recovers its final shape, although this final shape is not always a perfect round head.
How the head of the femur recovers and becomes rounded depends on the extent of the bone collapse and the age of your child at the time the disease process began. Bone tends to remodel better in younger children and improves as the child grows.
Risk factors for perthes disease
Risk factors for Legg-Calve-Perthes disease include:
- Although Legg-Calve-Perthes disease can affect children of almost any age, it usually begins between the ages of 4 and 10.
- The gender of your child. Legg-Calve-Perthes is about four times more common in boys than girls.
- White children are more likely to develop the disorder than black children.
- Genetic mutations. For a small number of people, Legg-Calve-Perthes disease appears to be connected to mutations in certain genes, but more studies are needed.
Perthes disease symptoms
The usual presenting symptom is limpness. This can be accompanied by pain, not just in the hip, but also in the knee, groin, or thigh. There may be stiffness in the affected hip (less movement than the other hip).
Perthes disease diagnosis
Hip X-rays can suggest and/or verify the diagnosis. Radiographs usually show a flattened and then fragmented femoral head. A bone scan or MRI can be helpful in making the diagnosis in cases where the x-rays are inconclusive. Simple radiographic changes are usually delayed 6 weeks or more from the clinical onset, so a bone scan and MRI are performed for early diagnosis.
The MRI results are more accurate, that is, 97-99% versus 88-93% on plain radiography. If an MRI or bone scans are necessary, a positive diagnosis is based on irregular areas of vascularization at the epiphysis of the femoral head (the developing femoral head)
Perthes disease treatment options
It is very important to keep the joint moving. This is because the cartilage in the femoral head relies on the fluid in the joint, called synovial fluid, for its nutrition. Moving the hip helps supply the cartilage with this fluid.
It is also important to keep the head in the hip socket so that when the bone re-forms, it is as round and as well shaped as possible. Sometimes your child’s hip becomes stiff and may need help keeping the ball in the cup. Your doctor may recommend a period of casting, braces, and/or physical therapy to help achieve this.
Surgery may be warranted to treat Legg-Calve-Perthes disease, but it is often not recommended for children younger than 6 years old. The goal of surgery is containment. The imprint is to keep the femoral head within the acetabulum. To do this, the pediatric orthopaedic surgeon can alter the angle of the femoral and/or acetabulum bones and fix them in a more anatomically correct position. This procedure, called an osteotomy, allows the femoral head to grow into its normal spherical shape.
Prevention of perthes disease
- Limit activity: Evading high-impact activities, such as running and jumping, will help release pain and protect the femoral head. Sometimes your doctor may also recommend crutches or a walker to prevent your child from putting too much weight on the joint.
- Physiotherapy exercises: Hip stiffness is common in children with Perthes disease, and physical therapy exercises are recommended to help restore range of motion to the hip joint. These exercises usually focus on hip abduction and internal rotation. Parents or other caregivers are often needed to help the child complete the exercises.
Complications of perthes disease
Complications of this condition include:
- The head of the femur may lose its normal spherical shape and collapse
- Degenerative joint disease can occur
- The affected leg may lose some of its movement and become shorter than the other leg.
- Children with Perthes disease are at higher risk of developing hip arthritis later in life.
- Irregular contouring, flattening, or fungal growth on the head
- Shortening and widening of the neck
- Flattening of the vertical wall of the acetabulum