FEMOROACETABULAR IMPINGEMENT (FAI)
Femoroacetabular impingement (FAI) is a condition caused by misshapen bone(s) in the hip. The hip joint is a “ball and socket” type joint comprised of two bones – the femoral head (ball) and a part of the pelvis called the acetabulum (socket). In normal hips, the ball and socket glide smoothly without any restraint. However, in patients with FAI, the ball and/or socket are misshapen, and the bones make abnormal contact with each other (e.g. “impinge”). This abnormal contact between the bones may lead to damage to the labrum (rim of cartilage surrounding the acetabulum) and/or to the articular cartilage that lines the ends of the bones.
FAI is thought to be due to a combination of genetic and developmental influences. Some people are born with a misshapen hip whereas other patients may develop a misshapen hip later in life (for example, from participation in certain sports). There are two types of FAI: CAM impingement and pincer impingement. In the majority of cases, patients have a mixed type of impingement, which includes a combination of CAM and pincer impingement.
CAM Impingement: this type of impingement occurs as a result of an abnormal shape to the femoral head. Instead of being round, the femoral head has a “bump” on one side, which leads to abnormal contact with the socket (acetabulum) with hip motion.
Pincer Impingement: this type of impingement occurs when the socket is deeper or extends further than normal around the ball. With hip motion, the labrum and cartilage between the ball and the socket can be “pinched” and may tear.
- Catching in the groin
- Groin pain or thigh pain with squatting down and bending the hip
- Pain and instability with activity and/or sports that require repetitive motion of the hip
Diagnosis And Treatment
Dr. Keller considers each patient’s symptoms, as well as a detailed physical examination, x-rays, and usually and MRI of the hip to make the diagnosis of FAI. Non-surgical treatment includes rest, activity modification, physical therapy to strengthen the hip and core muscles, and non-steroidal anti-inflammatory drugs. Injections, including steroid injections, are also helpful as they serve a dual purpose: to reduce pain and as a diagnostic test to determine if all of the patient’s pain is from the inside of the hip joint. If the patient fails non-operative management, then Dr. Keller may recommend surgery.
If surgery is necessary, Dr. Keller usually recommends an arthroscopic approach to the hip using two or three small incisions. During surgery, Dr. Keller introduces a camera into the hip through one incision and instruments into the hip though the other incisions. The two major bony procedures that are performed for impingement are femoroplasty and acetabuloplasty.