Definition of FAI (Femoroacetabular Impingement)

Femoroacetabular impingement (FAI) is an abnormal contact between the femoral head-neck junction and acetabular rim.

Most patients complain of pain in the groin, but pain may also radiate to your lower back, buttock or knees. The pain is often made worse with activity (including sports) and in positions where the ball and socket impinge such as: sitting in low chairs, getting up from chairs, climbing stairs, driving and putting on shoes and socks.

Some patients also have mechanical symptoms of ‘clunking’ and ‘clicking’ in the hip.

Hip and groin injuries account for 5-6 % of athletic injuries and is a significant cause of morbidity in athletes.

There is greater reporting for acetabular labral tears and intra-articular cartilage damage in athletes and dancers. FAI is implicated in both these.

Prevalence

FAI is most commonly seen in young atheletic persons of 20-40 years.  

Gender differences

CAM type FAI – young males

Pincer type FAI – middle aged women

Precursor to early hip Osteoarthritis

Acetabular labral pathology secondary to FAI leads to osteoarthritis due to repetitive microtrauma of the femoral neck bump (CAM lesion) against the acetabular rim.

Anatomy

Hip is a ball and socket joint consisting of the femoral head and the acetabulum of the pelvis, it enables a wide range of movement and three degrees of freedom.

Articular cartilage is predominently composed of type II collagen. The central acetabular floor is non-articular, being a fatty layer.

The ligamentum teres joins the femoral head to the acetabulum, and may play a role in stability.

Etiology

Morphologic changes in proximal femur or acetabulum lead to abnormal contact during hip flexion. Abnormal abutment of femoral head-neck junction and acetabular rim leads to pain and decreased hip ROM. In the long term this can lead to tearing at chondrolabral junction, cartilage delamination and eventual progression to Osteoarthritis.

CAM lesion

It is a bony prominence at anterolateral head-neck junction. It causes injury to anterior-superior aspect of acetabulum with fraying/detachment of labrum and delamination of cartilage. It lead to osteoarthritis superiorly in the hip joint. It is more common in young athletic males.

PINCER lesion

It is defined as an overcoverage of femoral head by acetabulum.  Acetabulum impinges on neck of femur. It leads to posterior-inferior (contre’-coup injury) causing cartilage wear-off in the posteroinferior part of the acetabular cup or central OA.It is more commonly seen in Middle-aged persons and often in females.

Is FAI Dangerous?

FAI is not life threatening but it can severely impact your quality of life and function. It can affect anyone: elite athletes and the active individual, manual labourers and office workers. Untreated in the short term, FAI causes ongoing pain and disability. Untreated in the long term, cartilage damage becomes permanent and may ultimately result in the hip joint wearing out prematurely and developing osteoarthritis.

What is the Treatment?

Analgesics such as Paracetamol and anti-inflammatories can help relieve symptoms. Avoidance of the ‘impingement position’ is encouraged. Injections into the hip joint can help relieve severe symptoms temporarily. Unfortunately however, none of these modalities treat the underlying cause. Femoroacetabular Impingement (FAI) is best treated with hip arthroscopy (or ‘key-hole surgery’).

All aspects of FAI can be treated successfully via hip arthroscopy:

• Abnormal ball (cam lesion)
  The abnormal bone is removed and reshaped to prevent further impingement and to protect the hip from further damage. This also improves your range of motion.
• Abnormal socket (pincer lesion)
  The abnormal bone is removed to prevent further impingement and to protect the hip from further damage.
• Labral tears
  These can be repaired and stabilised. Specialised anchors are used to re-attach the torn labrum.
• Articular cartilage damage
  If caught early, articular cartilage damage can be repaired and stabilised. Otherwise, unstable flaps can be removed and the underlying bone prepared to encourage new cartilage to form, a process known as ‘micro-fracture’.
• Ligament teres tears
  These can be trimmed, tightened and stabilised. Any inflamed tissue is removed.
• Bone cysts
  These can be removed or filled with a bone graft.

Participating and completing a tailored exercise program before (ie. pre-hab) and after surgery (ie. rehab) with a trained physiotherapist will achieve the best result for you after surgery.

FAQ

When can I walk?

Full weight-bearing and walking is allowed immediately. Initially, this will be aided by crutches. Most people will walk independently by 10-14 days post-operatively.

When can I drive?

You should not drive for 48 hours after an anaesthetic. After 48 hours, your ability to drive will depend on the side you had your operation, left or right, and the type of vehicle you drive, manual or automatic. If you had a left hip procedure and drive an automatic, you can drive whenever you feel comfortable. Otherwise, it is reasonable to drive when you are confident with walking and can fully weight-bear on your affected side.

When can I work?

Your return to work will vary depending on the procedure performed and type of work you are engaged in. Most people can return to office work within 2 weeks. Labour intensive work however, may require you to take 4-6 weeks before returning to full duties.

When can I play?

Low impact activities, such as cycling and swimming, can be commenced from week 4. If your procedure involves bone removal, high impact activities, such as running and jumping, are best avoided for 6 weeks post-surgery. Sport specific re-training can commence from week 6, with the aim to return to elite level sports 3 months post-surgery.

How long will I take to heal?

The wounds take 7-10 days to heal. Most patients improve dramatically in the first 6 weeks. Occasionally, there are periods where the hip may become sore and then settle again. This is part of the normal healing process. It takes three months for your hip to fully recover from hip arthroscopy. Continued improvements may be gained up to 1 year post-surgery.

How much pain will I experience?

Your experience of pain will vary depending on the procedure performed and the amount of pre-existing damage in the hip. Most patients are pleasantly surprised at how little pain they have after the procedure. Local anaesthetic is injected before and after the procedure to minimise any pain you may feel.

Will FAI return?

The symptoms of FAI occur when impingement occurs between the ball and socket of your hip. Once the abnormal growth of bone in your hip joint has been removed, it is unlikely to grow back. The risk of ongoing damage to the hip is now low as the cause of FAI has been removed.

What are the risks of hip arthroscopy for the treatment of FAI?
Complications are not common but can occur. Prior to making any decision to have surgery, it is important that you understand the potential risks so that you can make an informed decision on the advantages and disadvantages of surgery. The following list is by no means exhaustive, so it is important to discuss your concerns with your your surgeon.

Some patients occasionally report numbness or tingling in the groin or inner thigh. This usually resolves with time. It is quite normal to experience some swelling and discomfort in the leg, thigh and buttock region. This is expected and will also resolve with time. It is important to avoid high impact activities during the early phase of recovery to minimise the risk of fracture.

Other general surgical risks include: risk of infection, bleeding and clots in the leg (DVT) or lung post-operatively.

Apart from surgical risks, medical (including allergies) and anaesthetic complications can occur, and these can affect your general well being and health.

Other conditions which cause hip pain

Hip Labral tear

Hip Osteoarthritis

Avascular necrosis (AVN) of femoral head

Watch the procedure