Femoroacetabular impingement (FAI)

General information

Femoroacetabular impingement is a pathologic process in which the femoral head or neck chronically traumatizes the articular acetabular labrum or edge of the acetabulum.

The disease is caused by various congenital or acquired disorders of the relationship between the head of the femur and the acetabulum, including disturbances in their shape and configuration.

Classification

Three types of femoroacetabular impingement are distinguished:

1. Acetabular type (pincer) – characterized by abnormal anatomy of the acetabulum with unchanged proximal femur. In this variant of impingement, the acetabulum overlaps too much, as if overhanging the femoral head, and when bending in the hip, both the articular labrum filling the cavity and the cartilage covering the femoral head are injured. The acetabular type occurs more often in young and middle-aged women. Predisposing factors are increased anteversion of the acetabulum, coxa profunda, retroversion of the acetabulum (as a manifestation of dysplasia), and acquired factors are acetabular floor protrusion, protruding anteroposterior edge of the acetabulum, and retroversion of the acetabulum (as a consequence of trauma).

2. Femoral type (cam) – movement is impeded by a deformity at the base of the femoral head. This type is characterized by abnormal morphology of the femoral head-neck junction with an intact acetabulum. 

In this type of impingement, the femoral neck thickens (tubercle, excrescence), and the femur, when moving, inserts into the unchanged acetabulum and traumatizes the articular labrum.

The femoral type develops more often in young males. The cause of thickening on the femoral neck is either congenital: ellipse-shaped shape of the femoral head, protruding joint of the femoral head and neck, or acquired – epiphyseolysis, Perthes disease, aseptic necrosis of the femoral head, consequences of acetabular fractures.      

3. Mixed type – occurs most commonly in approximately 86% of patients with femoroacetabular impingement.

Symptoms of femoroacetabular impingement

• groin pain
• pain above the acetabulum with irradiation to the outside of the thigh
• pain with hip flexion and internal rotation
• onset after minor trauma
• pain increases after prolonged sitting or after significant strain on the hip joint
• pain is directly proportional to the load on the hip joint
• Patients younger than traditional coxarthrosis patients

Diagnosis of femoroacetabular impingement

Clinical examination and the doctor’s performance of special diagnostic tests. Diagnostic tests should be performed by a doctor with specific skills, good knowledge of anatomy, and experience performing them on many patients. The diagnostic informativeness of some tests is very high and allows 80-90% confidence to suspect femoroacetabular impingement even before the use of X-ray or MRI diagnostics.

The most sensitive is the impingement test, which measures pain during hip flexion and internal rotation.  

Additional tests may include:

• Apprehension test – pain in extension and external rotation;
• FABER test – the patient is lying on his back, legs bent at the knees with the soles of the feet touching each other. The doctor presses lightly on the knees, bringing them closer to the bed. The vertical distance from the knees to the bed is then measured. The test is considered positive if the vertical distance from the knee to the couch is greater on the affected side;
• asymmetry of external rotation – the damaged side will have less external rotation. 

MRI, in addition to the signs we see on the images, helps us evaluate the presence of free fluid in the joint cavity and damage to the joint’s soft tissue components.

Treatment of femoroacetabular impingement

Treatment of femoroacetabular impingement can be either conservative or surgical.

Conservative treatment consists of the patient’s compliance with a pain-free exercise regimen, anti-inflammatory treatment in case of exacerbation, taking chondroprotectors, and undergoing a course of physiotherapeutic procedures. Intra-articular platelet-rich plasma injections into the hip joint (“growth factors,” PRP) have a perfect clinical effect.

However, the primary treatment method for femoroacetabular impingement is surgical intervention, as it is possible to permanently eliminate the causes of impingement and its consequences only in this case. Hip arthroscopy is the most modern method of surgical treatment of femoroacetabular impingement. With the help of arthroscopy, we can perform the following manipulations: eliminate the overgrowth on the femoral neck by performing femoral neck repair, we can also perform resection of the overhanging edge of the articular socket, suture or remove damaged parts of the articular labrum, treat articular cartilage, remove formed exostoses and cysts, etc.

With untimely or inadequate treatment, femoroacetabular impingement leads to the early development of hip arthrosis, which is already a more serious disease, the result of which may be the replacement of the affected joint with an artificial one.                 

To perform quality hip arthroscopy and maximize successful results, three conditions are necessary:

1. Sufficient level of equipment for arthroscopy. It is necessary to have a complete set of high-tech equipment. The absence of at least one device or instrument makes it impossible to perform hip arthroscopy. 
2. Experienced orthopedic surgeon. Hip arthroscopy is a technologically more complex operation than, for example, knee arthroscopy or even shoulder arthroscopy. 
3. Adequate anesthesia care 

All these treatment options are available in more than 600 hospitals worldwide (https://doctor.global/results/diseases/femoroacetabular-impingement-fai). For example, Surgery for hip impingement can be done in following countries:

Turkey$3.6 K in 14 clinics

Germany$16.3 K in 35 clinics

United States$19.8 K in 15 clinics

China$21.4 K in 6 clinics

Israel$26.3 K in 13 clinics.

Rehabilitation after hip arthroscopy

In order to consolidate the success of treatment after hip arthroscopy, proper rehabilitation is essential. Naturally, the rehabilitation program should be prepared individually for each patient, but there are fundamental principles that are the same for all patients.

All patients are required to walk on crutches for two weeks after surgery with a small support on the operated limb. After two weeks, the patient is allowed to step on the leg according to tolerance. Gradually, if the patient has the correct gait pattern, he is allowed to give up first one crutch and then walk without crutches at all.

There are several stages of rehabilitation after hip arthroscopy.

• Stage 1 is the period from the end of surgery to the end of the second week, 
• Stage 2 – week 3 through week 6, 
• Stage 3 – 7th to 12th 
• Stage 4 is from the 3rd month until recovery. 

Each stage has its recommendations and limitations. 

In the first stage, the patient should perform isometric contraction of the thigh, buttock, and abdomen muscles, passive hip flexion, and internal rotation.

In the second stage, active movements and stretching exercises are added, and standing exercises and high-saddle bicycles are allowed.

In the third stage, the patient must regain full range of motion and pump the muscles. Exercises with resistance and additional weight are allowed. Of the training machines allowed, the exercise bike and stepper are allowed. Also, at this stage, effective classes in the pool will be allowed.

The last stage is the finish line to recovery. At this stage, we continue to strengthen muscles and pay special attention to proprioception.