Femoroacetabular Impingement

The cause of femoroacetabular impingement (FAI) is variable. It is most clearly attributed to developmental abnormalities of the hip that occur during the childhood growing years. Perhaps more commonly, it is associated with osteophytes (bone spurs) that form during adulthood. The most easily diagnosed type is an abnormal shape of the femoral head and neck. There is a prominence of the bone on the front of the femoral head and, when the hip is flexed upward, this bony prominence engages with the front of the acetabulum. The result is breakdown of both the labrum and articular cartilage. The less distinct type of FAI is a lip of bone overhanging the front of the acetabulum. Because of its location, it is harder to see on regular x-rays. The lip of bone pinches the labrum and causes it to tear. Many individuals may have this abnormally shaped bone without symptoms and do not require specific treatment. Symptoms usually occur as a consequence of cartilage breakdown and, if arthroscopy is needed to address the cartilage damage, it then becomes important to assess for impingement as the underlying cause and it can be addressed at the same time.

Management of impingement was originally described with open techniques. However, most cases can now be managed with a less-invasive arthroscopic approach. This advantage is especially evident in more advanced cases. Once the articular loss has become severe, correcting the impingement becomes less critical since the irreversible damage has already been done. Sometimes it is simply hard to tell the severity of the articular loss prior to surgery. Arthroscopy has the advantage of allowing assessment of the severity of the articular damage in addition to addressing the impingement. If the joint is beyond help, at least the surgery has not been too extreme.