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Femora Acetabular Impingement (FAI)

The hip joint disease called femoraacetabular impingement (FAI) is relatively common cause of pain around the hips. It shows its pain symptoms as soon as the femoral neck and the socket edge strike. Bony anomalies are often located at the transition point between the femoral head and the femoral neck ( Cam-Impingement, Nockwellen) or at the articular cavity ( Pincer-Impingement).
There are various possible causes for CAM-Impingements, such as bony formations (osteophytes) at the femoral neck or improperly healed diseases in children and adolescents (e.g.: M. Perthes, Epipyseolysis capitis femoris) (Figure 1). Pincer-Impingements can be congential (e.g.: Articular Cavity Retroversion, Protrusio acetabuli) or acquired (z.B. degenerative bone formations) (Figure 2).

Figure 1: Typical CAM-Impingement with a missing contouring at the femoral head neck transition

Figure 2: Typical Pincer-Impingement with an Articular Cavity Retroversion (white = anterior socket edge, grey = posterior socket edge)

In either case mechanical problems appear: Due to the strike between the femoral head-neck transition and the anterior socket edge, the labrum and also the joint cartilage can get damaged (Figure 3). In many cases this leads to premature osteoarthrosis.

Figure 3: CAM-Impingement (A), Pincer-Impingement (B) : Strike between the femoral neck and the socket edge.

Affected patients often complain about pain in the groin area which appears during a seated position or sports (e.g.: hurdle race, volleyball).
Typically, due to the bony pathology, at this disease there is no recovery with conservative treatment methods.

As with many other diseases, clinical and further diagnostic measures play a stering role at the diagnosis of a femoral acetabular impingement.
It is notable that affected patients are usually in pain while diffracting and bracing the internally rotated hip joint (impingement test). Thereby the femoral head-neck transition is pressed against the anterior socket edge. If there is any misalingment in this area, a full and proper movement is not possible. In this test the specialist can take references to a damaged labrum.
Conventional x-rays of the joint may confirm bony misalingements.Nowadays the MRI, with the use of contrast agents, is a essential complementary examination. Further phatologies and possible consequential damages can be registered prior to surgery which than can be planned exactly.

As mentioned earlier the treatment of the femoral acetabular impingement is usally in the form of an arhroscopical treatment. This allows the specialist to remove the bone formations via 2-4 small skin incisions and special instruments so that the patient has a full and pain free movement on all three levels (Figure 4).

Figure 4: Arthroscopical Removement of CAM-Impingements too a Femoral Head-Neck Transition Reshaping

In case of extended, in the dorsal direction reaching pathologies minimally invasive techniques are used which enable to remove all pathologies. In some instances, a luxation of the hip joint is necessary to perform an adequate treatment.

The duration of the stay in hospital can take anywhere from 3 days to up to a week, depending on the extent and technique of the operation.
The follow-up treatment also depends on the extent of surgical treatment. That is why every patients gets an individual program of physiotherapeutic exercise.

Arthroscopical treatment of the femora-acetabular Impingements (FAI)
(Source: courtesy of Fa. Arthrex Inc.)