Perthes disease, also known as Legg Calve Perthes disease or avascular necrosis, is a temporary bone disorder that affects hips of children.1 Basically, it is a childhood disorder that affects children between the ages of 4-8 years. It is five times more prevalent in boys than in girls, but if occurs in girls, the condition becomes more severe. Perthes disease, usually, affects only one hip and in 10-15% cases, it affects both the hips.
How Long Does Perthes Last?
The course of Perthes disease is very slow as bone remodeling takes several years. This is the reason why the symptoms of Perthes disease develop slowly over a period of time. Perthes is not a lifelong disability, but a temporary disability due to temporary interruption of blood to the head of femur. This leads to various temporary symptoms, some of which can also last for life if not managed properly or diagnosed late.
These symptoms of Perthes disease initiate with a change in the walking style of the affected child or a limping stride. This could be/could not be associated with pain in the hips, groin area, thigh or even a referred pain to the knee on the affected side. The movement of the child is also limited and there is stiffness along with reduced range of movement of the hip joint. The pain or limping may worsen with time, the thigh muscles also atrophy due to limited use, and there may be noticeable thinning of the thigh muscle. The pain may worsen with activity (such as sports) and alleviate with rest. Perthes may also result in leg length discrepancy and the affected leg may be shorter than the normal leg. This discrepancy could exacerbate limping and walking style of the affected child. The symptoms are fluctuant, which makes the diagnosis harder.
These symptoms of Perthes disease may last years, and recovery takes a long time. It may take 1.5 years for the complete recovery to take place and in some instances; it may even take more than 2 years to recover. Children who suffered from Perthes disease have a greater chance of osteoarthritis in adulthood.
Stages of Perthes Disease
Perthes disease is characterized by a condition in which there is temporary disruption of blood supply to the head of femur in its growing phase. The disruption in blood supply leads to necrosis of the femoral head (round in shape). After necrosis, the round shape of the femoral head changes to oval and this leads to misalignment of the ball and socket joint of the hip. Due to the change in shape of the femoral head, there are various complications leading to difficulty in hip and leg movement. The blood supply to the femoral head is reinstated, but not without temporary disability. The bone eventually remodels and there can be multiple cycles of bone breakdown and healing. The bone remodeling can be divided into four stages:
Necrosis: This stage starts with interruption of the blood supply to the femoral head and necrosis of the ball of femur.2 It is the initial stage and can last several months. The child begins to show signs of the Perthes disease such as a limp and change in walking style.
Fragmentation: In this stage, the femoral head that has undergone necrosis is replaced by woven bone, which is softer in consistency.2 It is in this period that the femoral head can be damaged as the head of femur is weak due to soft bone.
Reossification: The weaker bone is ossified into a stronger one. This stage of reossification can last for several years.
Healed: This is a stage when the regrowth of the bone is complete and the head of femur reaches its final shape. The roundness of the femur head depends on factors such as damage to the head at the time of fragmentation as well as the onset of the disease.
Doctors maintain the roundness of the femoral head by various treatment measures for keeping proper alignment of hip ball and socket joint.
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