Femoroacetabular Impingement

Femoroacetabular impingement (FAI) syndrome is a dynamic clinical disorder in which morphologic abnormalities of the acetabulum and/or femur combined with vigorous hip motion cause repetitive abutment between the femoral head-neck junction and acetabular rim. FAI is classified as cam (loss of femoral head-neck offset and asphericity), pincer (acetabular overcoverage) or combined type and has been increasingly recognized as a common cause of hip pain and functional limitation. Symptomatic FAI occurs predominantly in young, white, nonobese patients without prior hip disease. The etiology of FAI is controversial and likely multifactorial, with both genetic and acquired mechanisms proposed. There is growing evidence that participation in aggressive athletic activities during adolescence increases the risk of cam development due to repetitive injury to the proximal femoral physis. Sports at risk include football, hockey, soccer, and dance. Up to 50% of asymptomatic hips demonstrate radiographic FAI, particularly in athletes, highlighting the importance of considering symptoms and examination findings when making the diagnosis of FAI syndrome. Patients often report a gradual onset of motion- or position-related groin pain. Examination typically reveals limited hip motion, usually restricted internal rotation in flexion, and pain with provocative impingement tests. Numerous imaging parameters have been described to identify cam (a angle, head-neck offset) and pincer (center edge angle, acetabular index, crossover sign, and posterior wall sign) morphology on radiographs. While the natural history of FAI syndrome is thought to involve progressive chondrolabral damage leading to early osteoarthritis, currently there is no evidence that surgical treatment prevents or delays onset of osteoarthritis. (C) 2019 Elsevier Inc. All rights reserved.