As early as 1965, it has been recognized by some authors that a structural abnormality of the hip joint may be a cause of the majority of cases of idiopathic osteoarthritis (1). The deformities were variously described as a head tilt (1,2), pistol grip (3), or postslip deformity (4). In the last decade through a series of publications by Ganz’s group (5,6,7,8,9,10), the concept of femoroacetabular impingement (FAI) has reached a greater audience and is now a major area of scientific investigation and clinical management (11).

FAI is caused by a mechanical conflict between the bony contours of acetabular rim and the femoral head–neck junction during hip movement. Two distinct mechanisms have been defined (10). Cam impingement, in which an abnormal head–neck junction with decreased offset is forced into acetabulum causing increased shear stresses, leading to outside-in abrasion of the articular cartilage of the acetabulum which over time leads to damage of the chondrolabral junction. Over time the acetabular damage, which can be quite significant, also can lead to a tear or detachment of the labrum itself. Pincer impingement is due to an acetabular deformity that causes a relative anterior overcoverage of the femoral head, which can be global (protrusio) and local (acetabular retroversion). This leads to localized abutment of the femoral head–neck junction against the acetabular rim. With repeated impact this leads to damage to the labrum and subsequent degeneration, cyst formation or ossification, in addition there is damage to the adjacent rim cartilage (12). With more forced movement, contact of the femoral head–neck junction against the acetabular rim can act as a fulcrum causing leverage of the femoral head inside the acetabulum and subsequent damage to the posterior acetabular cartilage, producing a contrecoup lesion. Cam impingement appears to be more common in younger, athletic males and pincer impingement is more common in middle-aged females. Though these two separate mechanisms have been described, up to 45% may be a combined deformity (3,13). A recent study has suggested that the cam deformity is the main deformity leading to hip pain, especially with an alpha angle greater than 60 degrees (13).

Though there is no published data on the natural history of untreated cases of FAI showing a direct link to progression to osteoarthritis, there is some data to support that anterior impingement is associated with osteoarthritis of the hip (14,15). Currently the indication for surgical treatment of FAI is persistent hip pain with associated labral–chondral damage. Many authors believe that by correcting the deformity one may be able to prevent or delay the onset of osteoarthritis.

Surgical dislocation utilizing a trochanteric slide combined with an anterior hip dislocation was developed by Ganz et al. and allows a 360-degree view of the femoral head and acetabulum (16). With this technique both acetabular and femoral deformities can be easily addressed. The technique has proven to be both effective and safe in the treatment of FAI (5,17,18). However there are concerns with the inherent morbidity associated with this technique, especially trochanteric nonunion and painful hardware requiring reoperation for removal (18,19).

Less invasive techniques such as hip arthroscopy are becoming more commonly used to treat FAI, reports have shown results approaching those of the surgical dislocation (20,21). The disadvantages are difficulty in adequately judging the degree of correction of the femoral osteochondroplasty as well as dealing with complex combined deformities (22).

To avoid the morbidity of surgical dislocation and provide better visualization of the cam deformity than arthroscopy, some authors started to use a mini-anterior or Hueter approach facilitating access to the deformity as well as permitting direct visualization while performing the correction (23,24). This approach is usually combined with arthroscopy to deal with the central compartment damage at the acetabular–labral junction (25,26,27,28). Table 44.1 summarizes the advantages and disadvantages of the various techniques to FAI.

This approach is what many surgeons will recognize as the distal portion of the Smith-Petersen approach to the hip. Carl Hueter was in fact the first person to describe this in 1883, and it was popularized by the Judets for performing total hip arthroplasty (29). Smith-Petersen himself modified the approach, with the proximal extension, allowing exposure of the hip and outer wing of the ilium. He also described the usage of this approach for correcting what is essentially femoroacetabular impingement which he called coxae senilis/coxa plana: “A plastic procedure has been proposed for the relief of hip joint conditions resulting from interference with the normal mechanics of the hip joint” (30).

The basis of this muscle-splitting approach is the true internervous plane between tensor fascia lata (TFL) and gluteus medius laterally (superior gluteal nerve) and sartorius and rectus femoris (femoral nerve) medially. In the classical approach the plane between TFL and sartorius is opened, but this can damage the lateral cutaneous femoral nerve (LCFN). Letournel described a modification in which the medial aspect sheath of TFL is opened longitudinally and the dissection remains in the sheath as the dissection is taken deeper reducing the risk of damage to the LCFN (31).