Gelenk-Klinik

Femoroacetabular Impingement (FAI) What is a hip impingement syndrome? With femoroacetabular impingements (FAI), the hip joint (femoral head) and the socket (acetabulum) lie too closely together. When the hip is flexed strongly, the bones collide and can injure or wedge in structures close to the joint, such as the hip labrum or the acetabulum. Strong stabbing pain occurs in the groin area. What are the origins of FAI? FAI is a condition associated with an abnormal shape of the hip and the socket. Due to an anatomic mutation, friction arises between the hip and socket during certain movements. The repeated bumps that occur, cause the joint to lock and create damage to the labrum and the articular cartilage. If untreated, this may cause hip joint arthritis.

Hip impingement Show film

How many different types of hip impingement are there?
FAI generally occurs as two forms:

1. CAM Impingement
The Cam form describes the femoral head as abnormally big, in a way that there is a lack of the normal waisting of the femoral head-neck junction. Consequently, there is a loss of roundness which contributes to abnormal contact between the head and socket during powerful movements (i.e. when playing sports). The cartilage of the cotyloid cavity may become dismantled from the rim towards the centre, and labral tears may occur. Cam impingement is common within athletic young men.

2. Pincer Impingement

The pincer form is typically secondary to a socket that is too deep, but with a normal femoral head shape. Therefore, the femoral neck collides with the cotyloid cavity and pushes away the labrum. The femoral head/neck junction is also affected. This form typically exists within women aged between 30 and 40 years.

How is it diagnosed?

It is diagnosed through a provocation test, in which two swift movements are made instantaneously triggering typical groin pain. These movements are conducted by the doctor, whilst the patient lies supine. (The examiner adducts one leg to the body, while turning it to the centre of the body.) On the X-rays, the abnormal proportions of the femoral head and the cotyloid cavity can clearly be seen.

Further signs of FAI are bony spines on the femoral neck. Damage of the labrum as well as the soft tissue can be visualised by means of an MRT.

Treatment options

The pain can be relieved by means of medical treatment or electrotherapy, therapeutic baths and mudpack applications. However, as the mechanical problems persist and the joint continues to be damaged through movement, surgical treatment is inevitable. This orthopaedic operation is performed arthroscopically (keyhole surgery). With this simple intervention, the precise degree of damage can be assessed, and the impingement can often be treated during the arthroscopy. Thus the labrum can be fixed on the outer rim of the socket; misshaped femoral heads, joint cavities or joint necks can be trimmed and adapted or a joint neck can be reconstructed. The target for therapeutic measures is pain-free movement for patients and the slowing down or avoidance of deterioration caused by the hip impingement syndrome (i.e. increasing arthritis).