Perthes disease or Legg Calve Perthes disease is a rare bone condition that affects children. In Perthes disease, necrosis of the femoral head (the ball) of the femur takes place due to temporary interruption of blood supply to the femoral head.1 The ball and socket joint of the hip becomes weak due to femoral head bone necrosis. This causes the round shape of the ball to lose its roundness and turn oval. The oval shape of the femoral head makes it difficult for the ball and socket joint to align in place during movement and may lead to displacement of the joint. The interrupted blood supply to the femoral head is restored after sometime and the bone begins to heal.
The cause of this temporary interruption of blood supply to the femoral head has been linked to genetic predisposition and precipitation by environmental factors.
What Are The Symptoms Of Perthes Disease?
The symptoms of Perthes disease are all related to the temporary interruption in blood supply and its complications. Generally, only one joint is affected. Since Perthes disease affects the ball and socket joint of femur and hip, the most common initial symptom is the change in walking and running motion of the affected child. This is most apparent during a physical activity such as sports and the child may develop a strange style of running.
The child may even develop a limp due to discrepancy in the leg length measurement or due to pain while walking. Initially, the limp is slight, but with passing time, if no intervention is carried out, it becomes worse. The joint becomes stiff and the range of motion of the affected ball and socket joint is limited to a certain degree, so the child may have limited range of movement of the hip joint.
The child may even experience pain on the affected side of the hip, groin, thigh and/or knee. There may also be cramps on the affected side. The pain may worsen with activity and alleviate with rest. Due to the sequelae of the above symptoms, there might be thigh muscle atrophy of the affected side making the muscles of the thigh thinner and leaner as compared to the other leg.
Risk factors and Causes of Perthes disease
The risk factors associated with Perthes disease include age, gender, ethnicity and family history of the patient.1 Generally, children between the ages of 4 to 8 years are more affected with this condition. Males are more commonly affected than females, ratio being 5:1; however, it presents with more severity in girls. It is more common in white children as compared to black children. In some cases, it has been shown to run in families.
Although, the exact cause of Perthes disease condition is unknown, it has been linked to genetic mutation of certain genes. It has also been linked to environmental factors such as malnutrition of the child during the growth phase of the child, which might lead to interruption in the blood supply of the femoral head. There is still ongoing research regarding the etiology of Perthes disease.
Complications of Perthes Disease
Children affected by Legg Calve Perthes disease have a greater risk of developing osteoarthritis later in life.2 Perthes disease is self-limiting and takes around 1-2 years for the necrosed bone to be replaced by normal bone. If the femoral head does not heal properly or does not maintain the round shape of the ball of the femoral head, then this leads to problems later in life. This could be attributed to the fact that without the proper shape of the ball, there will be more friction between the head of femur and the socket (acetabulum) of pelvic bone. This friction leads to early wearing of the joint causing arthritis. Generally, children affected can live about 40 years of life without having arthritis, but it also depends on the severity of the disease. Children diagnosed later in life have a greater chance of developing complications.