One hundred years ago, three physicians (Drs. Legg, Calvé, and Perthes) reported on a bone condition in children’s hips they named after themselves: Legg-Calvé-Perthes disease (Pethes for short). Perthes is caused by a spontaneous loss of blood to the femoral head (round ball of bone at the top of the thigh bone). Necrosis (bone death), then collapse of the hip, and early arthritis are the natural results of this condition.
Since that time, there have been ongoing efforts to understand the cause(s) of this disease and find ways to treat it successfully. In the last few years, there has been some breakthrough in research on animals that might help humans.
In this article, Dr. Harry K. W. Kim, a well-known orthopedic surgeon and expert in the treatment of this condition, brings us up-to-date on current concepts and treatment of Legg-Calvé-Perthes disease. An important feature of this new information is the results of treatment for different age groups.
Until recently, all treatment (operative and nonoperative) was focused on a concept called hip modeling. The goal of treatment has been to mold the femoral head back into a round (spherical) shape and keep it in the hip socket (acetabulum). According to several large studies, the results of this approach have been only “modestly successful.”
Less than half the children treated for Pethes disease end up with a spherical, well-contained femoral head. And no one has been able to identify why some children respond to treatment while others do not. Some experts think there is a need to work more with the cause of the problem (loss of blood to the hip, impaired healing, altered biology) rather than just the effects of the disease (femoral head necrosis, deformity, and collapse).
Dr. Kim reviews current theories regarding the pathogenesis of Perthes disease. Most of the newer information comes from experimental studies on pigs and dogs. It’s looking more and more like a complex problem with multiple causal factors — not just one effect.
The new theories include ischemic injury leading to changes in the mechanical properties of the articular (joint) cartilage, change in mineral content of the bone, disruption of the growth plate, and an impaired repair process.
And with this new understanding comes an effort to rethink our current treatment approaches. For example, it is believed that putting load on the deformed hip will make the problem worse. So sometimes are restricted from weight-bearing activities in order to reduce the load on the hip. But whether or not this treatment strategy really makes a difference is unknown.
Another new approach is the use of antiresorptive therapy to combat the excess bone resorption. Medications known as bisphosphonates are being used in investigational (animal) studies. These drugs inhibit or prevent bone cells from being broken down. The optimal type of drug (local injection versus systemic application), amount of drug (dosage), timing of drug use (based on child’s age), and duration of drug therapy remain to be determined.
A third therapeutic option is called bone anabolic therapy. With this type of treatment, bone stimulating proteins called bone morphogenetic protein (BMP2) are used to speed up bone growth. The substance is injected into the hip to improve bone healing and preserve the round shape of the femoral head.
Studies using BMP2 for Perthes have all been done on animals with no studies on children yet. Long-term results and safety issues must be explored first before children could receive these new, as yet still experimental treatments.
But as Dr. Kim points out, improved understanding of the pathogenesis of this condition is starting to open doors. New avenues for research centered on pathologic-based rather than symptom-based treatment are being explored. The hope is to find some way to prevent Perthes from developing in the first place. A second goal is to treat the condition quickly and successfully when it does occur, thus preventing some of the long-term effects today’s generation with Perthes will suffer later in life.