Treating children with Perthes hip disease presents some interesting challenges. Current approaches include non-weight-bearing (not putting any weight on the leg) for long periods of time. This method is not necessary for younger children (before age six) because they tend to have a good prognosis. It is reserved more for older children but who may be less compliant (cooperative) with the idea of never putting any weight on the affected leg.
Perthes disease is a condition that affects the hip in children between the ages of four and eight. The condition is also referred to as Legg-Calve-Perthes disease in honor of the three physicians who each separately described the disease.
In this condition, the blood supply to the growth center of the hip (the capital femoral epiphysis) is disturbed, causing the bone in this area to die. The blood supply eventually returns, and the bone heals. How the bone heals determines what problems the condition will cause in later life.
In this study, researchers used piglets to simulate Perthes disease in order to study whether or not weight-bearing is harmful to the healing process. At the same time, they evaluated the effect of non-weight-bearing compared with weight-bearing. A group of 16 piglets were surgically altered to stop blood flow to the hip. Half the group were allowed to put weight on that leg; the other half were not allowed weight-bearing.
Eight weeks later, the hips were examined closely using X-rays, microscopic analysis, and micro-CT scans. They found much more flattening of the epiphysis in the femoral head (round bone at the top of the thigh bone) in the group allowed to put weight on the hip. The non-weight-bearing group was protected from deformity but the bone wasn’t perfectly preserved.
Due to the lack of blood supply and hip joint loading (both needed to maintain normal bone balance) there were still some changes observed in the femoral head in the non-weight-bearing group. But the important finding of this study was that non-weight-bearing DOES help protect the hip and helps prevent significant deformity. Maintaining as much integrity, shape, form, and structure of the femoral head also reduces the risk of collapse of the bone.
The authors suggest that future treatment of Perthes hip disease include two things: non-weight-bearing status AND medications to decrease bone resorption and stimulate the formation of new bone. Non-weight-bearing does help increase return of blood to the epiphysis but it does not encourage new bone growth. Combining drug treatment with conservative care (non-weight-bearing) might reduce the time older children have to remain non-weight-bearing and thus increase compliance.
The results of this study must be evaluated in light of the fact that animals were used. Human reactions are not always exactly the same as animals. Because the blood supply was cut off to the femoral head in the piglets, total femoral head involvement was present. This isn’t always the case with children who may have only a portion of the femoral head affected.
And finally, young piglets were used (the equivalent of a four or five year old child). Results might be different for older piglets representing older children. More study is needed in this area to understand: 1) the process by which Perthes develops, 2) the role of weight-bearing versus non-weight-bearing in the development of deformity, and 3) how medications might help enhance bone growth and speed up the healing process.