What is FAI?
FAI stands for “femoroacetabular impingement,” or hip impingement for short. FAI occurs when extra bone around the hip bumps up against the labrum and cartilage in the hip joint, resulting in pain and ultimately stiffness and early arthritis.
Symptoms of FAI
FAI can start off with just mild pain in early stages. Most of the pain is felt in the groin area, although it sometimes hurts on the outside or back of the hip. In many cases the pain can progress to severe levels. Untreated FAI can lead to stiffness and early arthritis. Occasionally, labral tears or an inflamed psoas tendon can cause snapping or catching sensations in the hip.
Anatomy of the Hip Joint
The hip joint can be thought of as a ball-and-socket joint. The femoral head is the ball, and the acetabulum is the socket. The hip labrum serves as a gasket around the socket to add stability to the hip. Sometimes extra bone grows on either the ball or socket side. This extra bone results in an abnormal shape that not bumps against, or impinges, against other structures in the hip. The result of this can be anywhere from mild pain at first, to a tear of the labrum and damage to the cartilage.
When the extra bone occurs around the femoral head (or the ball), it is known as Cam Impingement. When it occurs around the acetabulum (socket) it is known as Pincer Impingement. When it occurs on both areas, it is mixed impingement. Both types of impingement result in similar symptoms, although each causes unique patterns of damage to the cartilage and the labrum.
Diagnosis of Hip Impingement
The diagnosis of FAI is made based off a thorough history and physical examination, and imaging tests consisting of x-rays, MRI, and sometimes ultrasounds. Injections can be used to both treat the pain and to identify the location of the pain. The abnormal bony shape causing FAI can usually be identified on plain x-rays, although sometimes a CT scan is performed to help see the deformity in 3 dimensions. The MRI can help identify tears to the labrum and damage to the cartilage.
Treatment of FAI
FAI is treated in many ways. In some cases, nonsurgical methods such as physical therapy or injections are helpful. In other cases, surgery is performed. Most the time, surgery is performed arthroscopically using 2-3 small incisions. An arthroscope (small camera made for the joint) is used to visualize the hip and assist in repairs. If there are labral tears, they are usually repaired back to the bone. The extra bone causing the impingement (either the cam or pincer lesion) is resected back to a more normal shape. Other conditions can be treated during the surgery including snapping of the psoas tendon.
More Femoracetabular Impingement Resources
Arthroscopic Treatment of FAI: