Femoroacetabular impingement: the past, current controversies and future perspectives.

Femoroacetabular impingement (FAI) is a clinical syndrome in which the anatomical abnormalities of the femoral ead and/or the acetabulum result in abnormal contact between the femur and acetabulum during normal hip motion, leading to cartilage and/or labral damage and hip pain. It is often subdivided into cam-type and pincer-type impingement, which results from a reduction in femoral head-neck offset (cam) or over-coverage or focal/global acetabular retroversion (pincer). There is also mixed-type FAI in which both cam- and pincer-type deformities develop in the same hip. FAI has been considered a precursor to secondary osteoarthritis (OA) especially in cam-type impingement, but there is still no conclusive evidence about pincer-type impingement leading to OA.[1] In the United States, FAI surgery rate increased seven-fold among newly trained orthopaedic surgeons between 2006 and 2010, and this is projected to increase further.[2] The number of FAI-related publications increased five-fold between 2005 and 2010, showing a recent boom in FAI-related research.[3] Despite the large increase in the number of hip arthroscopies performed on FAI patients, the optimal diagnostic approach and treatment of FAI remains uncertain and controversial