Femoroacetabular Impingement - Causes, Symptoms, and Management

Introduction

The hip joint is a type of ball and socket joint. The ball is the femoral head or the upper portion of the femur bone (thigh bone), and the socket is formed by the acetabulum (a part of the pelvic bone). The acetabulum is protected by a fibrocartilage called the labrum, which creates a tight seal around the socket and also provides stability to the hip joint. The articular cartilage forms the covering of the ball and socket and provides a smooth, friction-free surface when the bones glide across each other during various movements.

What Is Femoroacetabular Impingement?

The term femoroacetabular impingement (FAI) was coined and described by Ganz in 2003. He identified FAI as the primary source of early osteoarthritis based on his clinical experience and after analyzing more than 600 surgical hip dislocations. It is also known as hip impingement. Femoroacetabular impingement occurs due to the formation of excess bone around the head and neck of the femur bone, resulting in an irregular shape. When the femur and acetabulum do not fit together properly in the joint socket, these bones rub against each other during movements. Over time, this causes pain, restricted motion, friction, and impingement, causing tears in the labrum or damage to the joint or the articular cartilage, further increasing the risk for osteoarthritis.

What Are the Types of Femoroacetabular Impingement?

There are three types of femoroacetabular impingement which include;

• Cam Lesion: It is a type of FAI in which the femoral head is abnormal in shape. Instead of a ball shape, it appears to be a bony bump and does not fit properly into the acetabulum. On flexion of the hip, it rubs against the acetabulum and causes damage to the labrum and the articular cartilage.

• Pincer Lesion: This occurs when excess bone forms at the rim of the acetabulum. The head of the femur rubs against this region, leading to the crushing of the labrum under the acetabular rim.

• Combined or Mixed Lesion: It is a condition in which both the femoral head and rim of the acetabulum are abnormal in shape due to excess bone growth.

What Are the Causes of Femoroacetabular Impingement?

The exact cause of the excess bone formation is not known. However, according to several studies, it may be due to genetic factors or intense participation in sports during adolescence when the bones are still developing can also be a causative factor. According to research, hip disorders such as slipped femoral epiphysis and Perthes disease have also been associated with femoroacetabular impingement. Individuals with developmental anomalies such as an abnormally shaped femoral head or acetabulum are also at risk of developing FAI.

What Are the Symptoms of Femoroacetabular Impingement?

The most common symptoms of FAI include;

• Sharp and stabbing pain in the hip or groin, which increases during physical activities. Pain is usually mild and remains for several years, but gradually, the symptoms may worsen and prevent the individual from participating in sports activities.

• Pain can also occur in the lower back, buttock, thigh, and knee regions.

• Pain can also develop due to sitting for long periods of time with hips flexed at a 90-degree angle.

• Stiffness in the affected area.

• Popping or clicking sensation.

• The limited movement causes difficulties during daily activities such as sitting, squatting, tying shoelaces, etc.

How Is Femoroacetabular Impingement Diagnosed?

• The healthcare provider initially reviews the medical history of the patient and then performs a physical examination. The doctor questions any past injury to the hip joint or a disorder and asks about the patient’s involvement in sports or other intense physical activities. The patient is asked to perform certain movements, such as turning, bending, flexing, rotating, etc., to evaluate the gait, and the patient is assessed based on the range of motion of the hip joint.

• An impingement test may be performed wherein the patient is asked to bring the knee up towards the chest and rotate it inwards towards the opposite shoulder. If this causes hip pain, the test is positive for impingement.

• An anesthetic test may also be performed by injecting a local anesthetic agent into the hip joint, and if it provides temporary relief from pain, it confirms the diagnosis of FAI.

• The doctor also recommends certain imaging tests such as X-rays, computed tomography (CT scan), or magnetic resonance imaging (MRI) scans of the hip to confirm the diagnosis. These not only determine the shape of the bones but also help identify the damage caused to the labrum or the articular cartilage.

How Is Femoroacetabular Impingement Managed?

Femoroacetabular impingement can be managed by surgical or non-surgical methods, depending on the condition of the patient. If left untreated, FAI can lead to an increased risk of development of arthritis in the affected hip.

1. Non-surgical Treatment: Non-surgical methods are initiated before considering surgery. These include;

• Medications: Non-steroidal anti-inflammatory drugs (NSAIDs) such as Ibuprofen, Naproxen, etc., are prescribed, which reduce the pain and inflammation at the joint. Intra-articular injections, which consist of a local anesthetic and a steroid, may also be recommended in some cases to alleviate the symptoms.

• Physical Therapy: Targeted exercises and stretches help stabilize and strengthen the hip muscles, improve the range of motion, and reduce the symptoms.

• Lifestyle Modification: It involves taking adequate rest and avoiding or reducing physical activities that cause or aggravate the symptoms.

2. Surgical Treatment:Surgery is recommended for patients whose symptoms do not improve with non-surgical modalities. The main aim of the surgery is to shave or remove the part of the bone causing impingement and to treat or prevent further damage to the hip joint, labrum, and articular cartilage. However, severe damage may not be completely fixed by the surgery. Some of the surgical methods include;

• Arthroscopy: It is a procedure wherein the surgeon uses an instrument called an arthroscope to view the inner aspect of the hip. It consists of a small camera and thin instruments to perform small incisions. It is performed by using a high-speed burr and shaving down the bump on the femoral head or trimming the bony rim of the acetabulum, thus repairing the damage to the articular cartilage and the labrum. It also minimizes soft tissue damage when compared to open surgery.

• Open Surgery: It involves removing or reshaping the bone and also addressing the underlying issues that contribute to the condition. Some severe cases of femoroacetabular impingement may even require a large incision to treat the condition. Open surgery provides better visualization of the affected area but requires a long period to recover due to more soft tissue involvement.

Conclusion

Femoroacetabular impingement is a condition in which excess bone grows along one or both the bones of the hip joint, resulting in an irregular shape. The exact cause for the same is unknown; however, it may begin in adolescence and continue over time if left untreated. It is treated conservatively or through surgery, depending on the severity of the condition. FAI is managed by a collaboration consisting of surgeons, nurses, and physical therapists. With appropriate therapy and rehabilitation, an excellent outcome can be achieved by the patients.