Perthes disease (also known by the longer name: Legg-Calvé-Perthes) 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 Perthes 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.
That may sound like a grim picture. Don’t let this information discourage you. The upside is that the disease is usually self-limiting (the body heals itself). 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 healing process can take two to four years for the necrotic bone to get resorbed and replaced by new bone. Studies show your best chances for recovery are to follow your physician’s advice carefully and give yourself a chance to heal naturally.
Everyone is different — there are different stages and severity of this condition. Your physician is the best one to give you more information as it relates specifically to you. It sounds like he or she is willing to level with you so don’t hesitate to ask for more information at your next appointment.