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.
Treating children with Perthes hip disease presents some interesting challenges. As you have found out, 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.
A recent study that might help answer your question caught our attention. 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.
It may seem like limiting the activity of a young child is harmful and that is normally true. But in the presence of Perthes hip disease (which can have serious long-term consequences later in life), following your physician’s guidance now will potentially pay off. There are no guarantees with this type of treatment. Some children still need surgery and some will develop degenerative arthritis early in adult life. But right now, it’s the treatment advised based on evidence from many animal and human studies.