Today we’re going to discuss Legg-Calve-Perthes disease. The learning objectives today are, one, to describe the epidemiology and etiology of Legg-Calve-Perthes, to understand the clinical presentation and differential diagnosis of Legg-Calve-Perthes, and to learn the basic management of Legg-Calve-Perthes. Legg-Calve-Perthes is one of the most common hip disorders in pediatrics. It is also known as idiopathic osteonecrosis, as the etiology of Legg-Calve-Perthes is unfortunately still unknown. It is caused by the lack of blood supply to the femoral epiphysis, but why this happens is not quite clear. The overall incidence of Legg-Calve-Perthes in the US is estimated to be one in 12,000 children, so it is rare. Boys are affected more than girls, with a ratio of 4 to 5:1. Interestingly, Caucasians are the most affected race, and Legg-Calve-Perthes occurs rarely in African-Americans and Asians. The age of onset is typically in school-age children with a peak incidence between five to seven years old. Bilateral hip involvement can occur, but it is rare, typically affecting only about 10% and 20% of patients. Interestingly, the exact cause of Legg-Calve-Perthes is not known. Multiple etiologies have been proposed, including infection, trauma, or a thrombophilic state. Abnormalities in clotting, such as a Factor V Leiden mutation or protein C and S deficiency could play a role in increased clotting. The proposed theory is that increased clotting causes venous thrombosis, which in turn impedes arterial blood flow to the femoral epiphysis. Regardless of initial cause, the known end result is loss of blood supply to the proximal femoral epiphysis, which is the growth plate of the femoral head. The lack of blood flow leads to ischemia, then osteonecrosis, and then eventually remodeling. Pediatric patients with Legg-Calve-Perthes will commonly present with limp and pain, but it’s important to know that patients may complain of pain localized to the hip or groin, or it can be referred to the thigh or knee. Limp may be more prominent after strenuous activity or at the end of the day. Other signs and symptoms include refusal to walk, limitation in hip movement, such as internal rotation, and abduction of the hip, leg-length discrepancy secondary to adduction contracture, or true shortening of the involved side from the femoral head collapse. Once Legg-Calve-Perthes is suspected, it’s important to quickly diagnose and refer to a pediatric orthopedist. The first test order is a plain routine radiograph. Two views, AP and lateral, both hips should be obtained. It is important to note that radiographic changes may not be visible until six weeks from the first onset of symptoms. So a normal X-ray initially does not rule out Legg-Calve-Perthes. Radiographs are used not only to diagnose, but also to stage, provide prognosis, follow the disease, and to assess any changes in management. An MRI can be more helpful, as it is more sensitive in detecting early disease. So it could be considered if X-rays are negative. Other diagnoses to be considered include transient synovitis, Slipped Capital Femoral Epiphysis, or SCFE, JIA, or osteonecrosis secondary to either HIV or sickle cell disease. Transient or toxic synovitis is a benign, self-limited disorder causing acute hip pain. It is thought to be secondary to infection or trauma. The key to differentiating transient synovitis from Legg-Calve-Perthes is timing. Transient synovitis should resolve within approximately one week without treatment, whereas Legg-Calve-Perthes will continue to progress. SCFE is a non-inflammatory condition where the femoral head is displaced from the neck. SCFE commonly presents in overweight males between the ages of 10 to 14. Juvenile Idiopathic Arthritis, or JIA, is an autoimmune disorder characterized by arthritis lasting more than six weeks, as well as systemic symptoms. Once diagnosis is suspected or confirmed by imaging, the patient should be referred to a pediatric orthopedic surgeon. The management of Legg-Calve-Perthes is controversial. The main goal is containment, or rather, preservation of the native joint. If possible, non-operative treatment includes limiting activity and weight-bearing exercises. NSAIDs, or non-steroidal anti-inflammatory drugs, are used for their anti-inflammatory properties. Physical therapy is also important for strengthening muscles around the hip joint. If the decision is made to operate, surgical treatment includes osteotomy of the proximal femur. Overall prognosis is good, and most patients with Legg-Calve-Perthes will resolve within one to two years. Prognosis is better for patients diagnosed before age five or six. This is due to the fact that children less than age six have better remodeling potential of the femoral head. Other negative prognostic factors include the extent of necrosis of the epiphysis and duration of the disease prior to diagnosis and treatment. It is important to note that children born with Legg-Calve-Perthes are also at risk for a degenerative joint disease due to permanent distortion of the femoral head as adults. In summary, Legg-Calve-Perthes is an idiopathic disorder due to avascular necrosis of the femoral epiphysis. It most commonly presents in young children aged five to seven. The most common symptoms are limp or pain, and the pain may be in the hip, thigh, or knee. The goal of treatment is to protect the native joint as long as possible, although surgery may be required.