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» Review and Update on a Childhood Hip Disorder
Review and Update on a Childhood Hip Disorder

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If you are looking for information on Legg-Calvé-Perthes Disease, look no further. In this review article, Dr. Harry K. W. Kim from the Center for Excellence in Hip Disorders (Dallas, Texas) provides us with an in-depth update on this hip disorder in children.

Legg-Calvé-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 Perthes disease. It was named in honor of the three physicians who each separately described the disease. Boys are affected five times more often than girls. In 10 to 15 per cent of children with this disease, both hips are affected.

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. Hip pain, limited hip motion, and a limp bring the child into the physician's office for diagnosis. The blood supply eventually returns, and the bone heals. But how the bone heals determines how much problem the condition will cause in later life. This condition can lead to serious problems and even permanent deformity in the hip joint later in life.

Understanding what part of the hip is affected may help in visualizing the problem. The hip joint is where the thighbone (femur) connects to the pelvis. The joint is made up of two parts. The upper end of the femur is shaped like a ball. It is called the femoral head. The femoral head fits into a socket in the pelvis called the acetabulum. This ball and socket joint is what allows us to move our leg in many directions in relation to our body.

In the growing child, there are special structures at the end of most bones called growth plates. The growth plate is sandwiched between two special areas of the bone called the epiphysis and the metaphysis. The growth plate is made of a special type of cartilage that builds bone on top of the end of the metaphysis and lengthens the bone as we grow. In the hip joint, the femoral head is one of the epiphyses of the femur.

The capital femoral epiphysis is somewhat unique. It is one of the few epiphyses in the body that is inside the joint capsule. (The joint capsule is the tissue that surrounds the joint.) The blood vessels that go to the epiphysis run along the side of the femoral neck and are in danger of being torn or pinched off if something happens to the growth plate. This can result in a loss of the blood supply to the epiphysis.

Perthes disease results when the blood supply to the capital femoral epiphysis is blocked. There are many theories about what causes this problem with the blood supply, yet none have been proven. There appears to be some relationship to nutrition. Children who are malnourished are more likely to develop this condition.

Children who have abnormal blood clotting also (a condition called thrombophilia) may have a higher risk of developing Perthes disease. These children have blood that clots easier and quicker than normal. This may lead to blood clotting that blocks the small arteries going to the femoral head.

As a result of new evidence, the certainty of thrombophilia as a cause of Perthes is now under debate. This will remain an area of study until scientists clear up the significance of thrombophilia as a possible cause of Perthes.

There is some new evidence that Perthes disease is genetic as a result of a mutation (abnormal change) in the type II collagen (fibers that make up soft tissue structures). Previously there was no known increase in risk for children whose parent had Perthes disease as a child. But this belief may no longer be accurate.

Studies among Asian families who have many members with this disease have been found with this mutation in the type II collagen gene. Scientists think that the mutation results in weakening of the hip joint cartilage that also affects the blood vessels within the cartilage.

Whatever the true cause of ischemia (lack of blood to the area), the result is bone death (called necrosis) of the femoral head. Without a normal blood supply, the bone loses its strength and shape. The loss of bone density and softening of the head result in a misshapen head. With the hip supporting the weight of the body, tiny microfractures in the necrotic bone fail to heal. This is another reason why normal wear and tear results in deformity.

Treatment is centered around the main goal of preventing deformity of the femoral head. When prevention isn't possible, then minimizing the damage to this area is the next best approach. Treatment varies depending on the age of the child at the time of diagnosis. Long-term management for adults affected by this condition during childhood is another aspect of treatment.

The surgeon's challenge is being able to tell which child needs surgery and when. X-rays and MRIs are used to get a handle on where the bone is affected, how much damage is present, and what kind of blood supply is present.

Studies show that surgery is needed when there is a large area of the femoral head and epiphysis affected. Earlier treatment (in children up to eight years old) yields better results. Treatment is more difficult when the femoral head has already fragmented and/or collapsed.

Reference: Harry K. W. Kim, MD. Legg-Calvé-Perthes Disease. In Journal of the American Academy of Orthopaedic Surgeons. November 2010. Vol. 18. No. 11. Pp. 676-686.

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