Femoroacetabular Impingement (FAI)

Femoroacetabular impingement, also known as FAI or hip impingement, is a condition in which there is abnormal contact between the ball (aka the femoral head) and the rim of the socket (the acetabulum). The condition is now thought to be a major contributor to the development of arthritis of the hip joint.

Femoroacetabular impingement can be classified as:
• cam type
• pincer type
• combination of cam and pincer

In cam type, the impingement occurs because of the presence of build-up of bone (a "bump" or "cam") on the front of the femoral head and neck. This build-up may be the result of an abnormality of the growth plate in the femoral head that occurs during growth. Impingement occurs when the bump rolls into the socket during movement of the joint. This ultimately can result in tearing of the labrum and injury of the cartilage on the inside of the socket.

In pincer type, the socket is too deep or has abnormal anatomy that restricts motion of the joint and causes damage to the labrum or cartilage.

In most cases, FAI involves a combination of both cam and pincer type impingement.

Femoroacetabular Impingement Symptoms

Stiffness of the hip and episodic groin pain are the initial symptoms of hip impingement. The groin pain is usually worsened with activity requiring the hip to move near the extremes of motion (i.e., flexion of the hip joint). As the condition progresses, pain may be present with more subtle activities, such a prolonged sitting or walking up a hill. Pain that occurs at night or with walking on level ground may herald the onset of early arthritis of the joint.

Femoroacetabular Impingement Diagnosis

Your orthopedic physician can usually make the diagnosis by examining the hip joint. Patients with hip impingement often will have loss of motion of the joint and pain with certain hip maneuvers. Regular X-rays will often confirm the diagnosis. An MRI of the hip done after dye is injected into the joint (an "MR Arthrogram" will allow better visualization of the bone and cartilage in and around the joint. In certain cases, a CT scan with 3-dimensional reformatting will assist your orthopedist with surgical decision making.

Nonsurgical treatment of Femoroacetabular Impingement

  • Medications
  • Activity modification-cessation of the motion that causes the symptoms
  • Physical therapy

Surgical treatment of Femoroacetabular Impingement

Your orthopedic physician may recommend arthroscopic or open surgery of the joint. Arthroscopic surgery is a minimally invasive procedure that can remove the source of impingement and remove or repair a torn or damaged labrum. This surgery may prevent further damage that could require more extensive surgery.

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