Femoroacetabular Impingement (FAI)

Cam, pincer or mixed (Ganz)

Key Concepts

Femoral-acetabular impingement (FAI) results from anormal contact between the proximal femur and the acetabulum during the terminal phase of the hip range of motion. This contact between the two bony surfaces causes damage to the acetabular labrum and the cartilage tissue that lines the acetabular cavity and femoral head internally, and may lead to joint wear and early arthrosis.

Two types of conflict have been described: cam, more common in young males, and pincer, more common in middle-aged women. Cam results from the loss of the habitual sphericity of the femoral head, with decreased offset between neck and head, causing apposition to the acetabulum. This type of conflict usually occurs in flexion leading to joint injury and labrum tear. The pincer results from abnormal contact between part or the whole acetabular wall and the junction between femoral neck and head, thus causing acetabular overcrowding, which may be global in the deep thigh or focal in the anterosuperior region of the acetabulum, in the case of acetabular retroversion. This type of deformity may originate intra-substance lesion of the labrum and contra-rotation lesion in the postero-inferior region of the acetabulum.

What causes it?

The causes may be idiopathic, traumatic or sequel to childhood hip diseases.

How does it manifest?

The most frequent symptoms are pain in the anterior (inguinal) and lateral (gluteal) hip area “C-sign”. It can course with stiffness, claudication and rebound. The onset of the complaints may be insidious or acute traumatic. The complaints are usually mechanical and are associated with certain types of movements or positions such as getting in and out of the car, sitting for a long time (driving), moving from sitting to standing, and crossing or bending the leg. The pain can be accentuated by sporting activity and hip strain and is common in martial arts practitioners, yoga, footballers, hockey players and dancers.

The diagnosis is made on the basis of a specific clinical examination and with the use of auxiliary diagnostic tests. As the anatomical variability of the hip is very great, it is necessary to take X-rays in specific positions for a morphological study. At the same time, it is necessary to carry out a complementary study with computerised tomography for a more detailed study of the bone morphology of the hip and pelvis. The joint study is done using magnetic resonance to assess the labrum, cartilage tissue and other joint and periarticular structures. Often, when there is diagnostic doubt, it is necessary to perform a therapeutic test by infiltrating the joint with local anaesthetic.

How is it treated?

The treatment can be medical or surgical.

Medical: change or adaptation of daily activities and suspension of physical activities, as well as the use of anti-inflammatory or analgesic medication. Physiotherapy, namely with specific muscular reinforcement, can increase the hip’s range of movement and reinforce the muscles of that joint, relieving the joint complaints.

Surgical: surgery involves reconstructing the anatomy, correcting the conflict factors and associated lesions. This correction should be done without delay in individuals with complaints before irreversible lesions are established in the cartilage tissues of the acetabular head and bottom. The technique favoured by the team is hip arthroscopy. In very specific cases, it may be necessary to resort to surgical dislocation of the hip. Complications of hip arthroscopy: general 1.4% (pudendal, femoral, sciatic or lateral femorocutaneous nerve neuropraxia); rare abdominal compartment syndrome; joint instability; under-correction, cam and pincer deformities; over-correction may lead to femoral neck fracture; heterotropic calcifications 1.6%.