It is the idiopathic avascular osteonecrosis of the capital femoral epiphysis of the femoral head. It is caused by an interruption to the blood supply of the head of the femur close to the hip joint. It is equivalent to adult avascular necrosis.
It is also known as Perthes disease, ischemic necrosis of the hip, coxa plana, osteochondritis and avascular necrosis of the femoral head, or Legg–Perthes Disease or Legg–Calve-Perthes Disease (LCPD).
The first signs are complaints of soreness from the child, which are often dismissed as growing pains, and limping or other guarding of the joint, particularly when tired. The pain is usually in the hip, though can also be felt in the knee (so-called 'referred pain'). In some cases, pain is felt in the unaffected hip and leg. This is due to the child favoring the injured side and placing the majority of the weight on the "good" leg. It is predominantly a disease of boys (4:1 ratio). Whereas Perthes is generally diagnosed between 5 and 12 years of age, it has been diagnosed in children as young as infants. Typically the disease is only seen in one hip, bilateral perthes is seen in about 8-10% of children diagnosed.
Diagnosis is made predominantly by X-ray study, together with physical examination (MRIs have also been found useful for judging the extent of the deformity). Sufferers typically have limited range of motion in their hip, particularly when rotating the joint.
Treatment has traditionally centered on removing pressure from the joint until the disease has run its course. Options have included bed rest and traction (to separate the femur from the pelvis and reduce wear), often for several months or even years. Plaster casts were also popular, again to isolate the joint. Recent evidence suggests that these methods are not effective, and treatment seems to be moving towards a mixture of careful monitoring, physiotherapy, and surgical intervention when necessary.To maintain activities of daily living, a custom orthoses may be used. These devices internally rotate the femoral head and abduct the leg(s) at 45 degrees. Orthoses can start as proximal as the lumbar spine (LSO),and extend the length of the limbs to the floor. Most functional bracing is achieved using a waist belt and thigh cuffs derived from the Scottish-Rite Orthosis . These devices are typically prescribed by a physician and implemented by a certified orthotist. For older children, the distraction method has been found to be a successful treatment by using an external fixator which relieves the hip from carrying the body's weight. This allows room for the top of the femur to regrow and shape better.
Modern treatment focuses on removing pressure from the joint in concert with physiotherapy. Pressure is minimized on the hip through use of crutches or a cane, and the avoidance of running-based sports. Swimming is highly recommended - it allows exercise of the hip muscles with the full range of motion, while reducing the stress to a minimum. Physiotherapy treatment generally involves a daily series of exercises, with weekly meetings with a physiotherapist to monitor progress. These exercises focus on improving and maintaining a full range of motion of the femur within the hip socket. Performing these exercises during the healing process is essential to ensure that the femur and hip socket have a perfectly smooth interface. This will minimize the long term effects of the disease.
Perthes is a long-term problem - treatment is aimed at minimizing damage while the disease runs its course, not at 'curing' the disease. As sufferers age, problems in the knee and back can arise secondary to abnormal posture and stride adopted to protect the affected joint. The condition is also linked to arthritis of the hip and other joints, though this appears not to be an inevitable consequence. Hip replacements are relatively common as the already damaged hip suffers routine wear; this varies by individual, but generally is required any time after age 50.
Caucasians are affected more frequently than other races, males are affected 4-5 times more often than females, suggesting a partial sex-linked genetic inheratance of the syndrome. 1 in 100 male children of adults with Legg–Calvé–Perthes syndrome also exhibit the syndrome. It is most commonly seen in persons aged 3-12 years, with a median of 6 years of age. In the US, 1 in 1200 children younger than 15 years will have this disease while in the UK the incidence is higher, with Ireland having the highest percentage. It is also found in Latin Americans, Asians and Inuit Indians.