Femoroacetabular Impingement Syndrome

Femoroacetabular Impingement Syndrome

Femoroacetabular impingement (FAI) or hip impingement syndrome refers to the constellation of signs and symptoms brought about by abnormal contact between the acetabulum and femoral head-neck junction. This contact or impingement might occur within the normal physiologic range of motion as a result of subtle osseous abnormalities of the acetabulum or femur where the femoral neck transitions to the head. Alternatively, the impingement can occur in an otherwise morphologically normal hip as a result of extreme range of motion activities. Recurrent impingement can result in injury to the acetabular labrum and adjacent cartilage. Recent investigation has indicated that this abnormal impingement might lead to early degenerative changes in the hip joint and might, in fact, be the underlying etiology in most osteoarthritis cases previously identified as idiopathic (Ganz 2003; Beck 2004; Goodman 1997; Lavigne 2004; Tanzer 2004; Wagner 2003).

Two different joint morphologies have been proposed as a cause for femoro acetabular impingement that may lead to labral failure (Lavigne 2004). A larger femoral head may lead to “cam” impingement whereby the head prematurely impacts the antero-superior aspect of the acetabular rim during active hip motions causing acetabular cartilage and labral damage. “Pincer” impingement occurs when a normal femoral head is paired with an abnormal acetabulum (e.g., coxa profunda or acetabular retroversion). This type initially affects only the labrum.

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