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What Happens in Children with Legg-Calve-Perthes Disease When They Become Adults?

That's a long title but it reflects a long journey from childhood into adult years with a condition called Legg-Calvé-Perthes (LCP) disease. What happens to these children with and without treatment? How does the disease affect them as adults? These are the questions addressed in this review article on the natural history of LCP.

Legg-Calvé-Perthes disease affects the hip (or hips) of children between the ages of four and eight most often. But the disease can show up later in the teen years. The condition develops after there has been an interruption in blood flow to the growing centers of the hip.

Those growth centers (called the capital femoral epiphyses) are located at the round top of the femur (thigh bone). Without enough blood, the bone starts to die, a process referred to as necrosis.

The dead bone cells are eventually replaced by new bone cells but this can take several years. In the meantime, pressure and load from weight on the bone causes it to flatten. The smooth, round head of the femur that sets inside the hip socket (acetabulum) becomes oval-shaped (ovoid) or misshapen. Instead of fitting tightly inside the acetabulum, bone extrudes or expands outside the confines of the socket.

In severe cases (and especially in children who develop this condition after age eight), the deformed hip may develop early arthritis. In a small number of children who don't have signs of LCP until into their teen years, the chances of full recovery is very slim. That's because the bone never gets the full blood flow back that it needs to remodel.

In all cases, the more flattened the bone and the more misshapen the round femoral head becomes, the more likely degenerative arthritis will occur at an early age. The reason for this is that joint surfaces need to be evenly matched or congruent. Without this tight fit, the bones rub against each other unevenly. Over time with repeated movements, the joint degenerates where the greatest amount of pressure has been applied.

How does knowing the natural history and prognosis of Legg-Calvé-Perthes disease help children and teens with this problem? Studies show that isotope and MRI scans show the pattern of lost blood even before X-rays. Since the disease is self-limiting (the body heals itself), identifying this problem early may help.

Giving the hip every opportunity to heal itself by limiting load on the joint may prevent the flattening of the femoral head and deformity that can develop. The only problem is -- it can take two to four years for the necrotic bone to get resorbed and replaced by new bone. And in some cases, new bone never forms. Instead, there is new granulation (healing) tissue, but that area doesn't harden into bone, it just forms cartilage.

The physician will be able to follow the healing process using X-rays and MRIs. These imaging studies show the four stages of LCP. These four stages are 1) necrosis (death of bone cells), 2) fragmentation (breakdown of dead bone), 3) regeneration of bone (new bone forms), and finally, 4) healed replacement of normal bone tissue.

Fractures of the weakened bone develop in about one-third of the children during the fragmentation phase. That's when the head of the femur becomes deformed and extrusion (spread of bone out from under the hip socket) occurs. Fractures can also develop when new bone is forming. X-rays help show this as well.

There are some other complications that can develop during healing. During the fragmentation stage, there is the possibility of bone cysts forming and osteoporosis (brittle, weak bone) developing. These problems resolve slowly as the full healing process proceeds from beginning to end.

Fusion of the growth plate too soon can also occur. There is a poorer prognosis if this happens. The neck of the femur (connects the long shaft of the bone to the round head) stops growing. The effect of this complication is that the affected leg will be shorter than the other leg.

Along with changes on the femur side of the hip, there can also be changes in the acetabular (socket) side. Thickening of the joint cartilage as well as changes in the shape and size of the acetabulum can affect final outcomes.

In summary, the greater the degree of blood loss and bone changes associated with Legg-Calvé-Perthes (LCP) in childhood, the worse the final results as an adult. Age is the determining factor in this condition. Recovery is more likely in children under the age of eight. Development in teens is infrequent but with a poorer prognosis.

But the good news is that many children have mild LCP, and they are able to heal and recover fully even without treatment. The hip actually remodels itself and remains smooth moving. Early degenerative hip arthritis does not always occur and these children have no hip problems in adulthood related to their childhood history of Perthes disease.

Reference: Benjamin Joseph, MD, MS Orth, MCh, Orth. Natural History of Early Onset and Late-Onset Legg-Calvé-Perthes Disease. In Journal of Pediatric Orthopaedics. September 2011. Vol. 31. No. 2. Supplement. Pp. S152-S155.