Legg-Calve-Perthes or 'Perthes' disease
In Perthes disease, the blood supply to the femoral epiphysis is interrupted, leading to avascular necrosis. The cause is unknown. Following avascular necrosis, the bone softens and breaks down, then over the following months to years, the blood supply regrows, and the bone reforms and remodels. In some cases this leads to severe deformity of the femoral head, and early osteoarthritis. Perthes disease is more common in boys and tends to present between the ages of 4 and 8.
Children present with hip or knee pain, and/or limping. The limp may be of insidious onset, and worsen with exercise. It is bilateral in 10-15% of cases. On examination, classical features are of restricted internal rotation of the hip, and restricted abduction.
If Perthes is suspected, anterior, posterior and lateral hip radiographs should be requested; these may be normal in early disease, or may show the typical appearance of an irregular femoral head. Bone scans, arthrograms or MRI are sometimes used to confirm the diagnosis.
Treatment aims to maintain a good range of movement, control pain, and minimise any future deformities of the femoral head. Physiotherapy is very important, but in a small number of cases, surgery may be required. Those who present at an older age, and with more advanced changes have a worse prognosis and are likely to develop early osteoarthritis.
The photograph shows Perthes disease at the right hip with fragmentation of the femoral head and shortening of the femoral neck.