What Is Legg-Perthes?
Perthes disease, also known as Legg-Perthes disease, is a childhood hip disorder that affects the ball part of the hip joint, which is called the femoral head. The blood supply to the femoral head is disrupted for an unknown reason and causes damage to the femoral head. Over a one- to two-year period, the bone in the femoral head is slowly removed and replaced with new bone.
The Legg-Perthes condition can cause hip joint pain and stiffness for a period of time. This disease tends to affect only one hip in 85 percent of patients although the remaining 15 percent of patients may be affected on the other side at a later time period during childhood. It is three to five times more common in boys than girls. The disease can be seen from age 2 to 14, but most commonly it is seen in 6- to 8-year-olds. Early diagnosis and treatment of Legg-Perthes disease can improve the long-term outcome. View more information from frequently asked questions about Legg-Perthes disease.
The cause of this disease is not known at this time, except for in rare cases where there is an extensive family history of the disease and both hips are affected. For unknown reasons, the blood circulation to the femoral head becomes disrupted. Because the blood supply is needed to keep cells alive, as it provides nutrients to the cells, the disruption of the blood supply causes cells in the bone to die. The bone death is called “necrosis” or “osteonecrosis.” View glossary of terms.
Stages of Legg-Calvé-Perthes Disease
a. Initial stage - The femoral head stops growing and remains smaller than the unaffected side.
b. Resorptive or fragmentational stage - During this stage, the dead bone is removed or reabsorbed by the healing process. Because the dead bone is removed from the femoral head and the loss of bone weakens the strength of the femoral head, it can become flattened or collapsed. With the removal of the dead bone, the femoral head starts to break up into fragments, thus the stage being called fragmentational stage. In some patients, this stage can take one to two years to complete.
c. Reossification stage - Slowly new bone starts to fill in the areas where the dead bone has been removed. Since ossification means bone formation, this stage is called the stage of reossification.
d. Healed stage - The femoral head has completely healed itself. Because the femoral head will heal itself, the disease is often said to be “self-healing” or “self-limiting.” However, it is important to know that self-healing does not mean that the femoral head will always heal back to its original round shape. The age of the patients at the time of diagnosis and the extent of the femoral head damage may affect how well the femoral head will heal itself back to its normal round shape.
How Is Legg-Perthes Disease Treated?
Various treatment methods exist for Perthes disease because the best treatment option depends on the age at onset of the disease, the amount of the femoral head involvement and the radiographic stage of the disease. No single treatment method will work on all patients. Also, no single treatment consistently prevents the development of femoral head deformity at this time. Thus, the treatment is individualized and several factors influence the doctor's decision-making: the age of the patient, the stage of the disease, the physical and X-ray findings and the patient's ability to comply with a doctor's recommendation.
The age of onset of the disease is an important factor that we consider along with history, physical examination and X-ray findings when we choose a treatment for the patient. Chief of Staff Dr. Tony Herring's 2007 study on young children (onset of disease before 6) suggests that most of the patients in this age group do well regardless of the type of treatment received. Given the results, we generally do not recommend surgical treatments for young children less than 6 years old with Perthes disease. Rather, we would recommend nonoperative treatments, such as decreasing the activity level and using crutches, a wheelchair or even rest when the symptoms are severe. Certain X-ray findings have shown a good outcome without major treatment in children younger than age 8 as well.
The recommendation for older children cannot be generalized. There is a general trend toward earlier intervention in older patients (age of onset after age 8). Treatment options for this age group include femoral and pelvic osteotomies in which femoral or pelvic bone are cut and repositioned to place the femoral head in a more protected position within the hip joint socket, called the acetabulum. There are other procedures, as well, such as the “shelf” procedure, that increases the coverage of the femoral head. Recently, the placement of an external fixator to distract the hip is also offered in some centers, but to our knowledge, the beneficial effect of hip distraction using an external fixator is uncertain at this time.
In terms of outcome, the study at TSRHC headed by Dr. Herring showed that the overall operative treatment group, those that received femoral or pelvic osteotomies, did better than the nonoperative group in children older than 8 at the age of onset of the disease. See more of this study. Other researchers have studied prolonged use of a wide abduction brace (A-frame brace) with decreased weight bearing to improve the outcome of the hip in older patients with Perthes disease. Another brace called Scottish Rite orthosis has shown mixed results and further studies are needed in determining the role of bracing in Perthes disease.
What Is the Outcome for Legg-Perthes Disease?
The outcome of the disease can be divided into short-term, meaning within a few years of disease onset, and long-term, meaning many years from the healed stage. In most patients, even if the femoral head is not round, the patient will be able to walk, participate in sports' activities and have an active lifestyle.
Only in the long-term, some patients with a moderate to severe flattening of the femoral head develop hip joint arthritis.
Some factors that affect the outcome for Legg-Perthes disease are:
A. Age: It is generally accepted that if the disease starts before the age of 6 years, the patient will have a better outcome even without specific treatment. Dr. Herring and co-authors reported that 80 percent of the children with the onset of the disease before age 6 had good outcomes with nonoperative treatments. When the onset of the disease is after age 8 (late-onset Perthes), it is generally believed that the outcome can vary.
B. Lateral pillar involvement of the femoral head: Studies by Dr. Herring show that the amount of loss of the height of the lateral pillar can predict clinical outcome. The lateral pillar refers to the lateral third of the femoral head. Lateral pillar type A refers to no loss of height. Type B refers to less than 50 percent loss of height. Type C refers to greater than 50 percent loss of height. Type B/C refers to in between type B and C.
C. The type C is generally associated with poorer outcome in late-onset Perthes disease.
Current research on Perthes disease at TSRHC and the Center for Excellence in Hip Disorders
Several studies are currently active in the Center for Excellence in Hip Disorders, led by Dr. Harry Kim.
Investigating the cause of the femoral head deformity
Investigating the role of MRI in assessing femoral head healing
Investigating the natural history of Perthes disease
Developing medical treatment for Perthes disease