What is Femoroacetabular Impingement?
Femoroacetabular impingement (FAI) is a condition that causes hip pain due to mechanical interference caused by abnormal shape or deformities in the hip, specifically in the upper part of the thigh bone (proximal femur) and/or hip socket (acetabulum). This interference happens during high-range or repetitive abnormal movement where the bony protrusions of these areas come into contact, damaging the tissues of the femoroacetabular joint (hip joint). This continuous repetitive damage can, in turn, cause hip pain and affect movement over time.
The irregular bone features leading to FAI are known as a “cam deformity” and a “pincer lesion”. A cam deformity is an abnormal bony bump at the connection or “junction” of the femoral head (top of the thigh bone) and the neck, leading to a non-spherical, or not perfectly round, shape, most commonly observed in the front and upper section of this area. A pincer lesion, on the other hand, is an abnormal overhang on the outer front edge of the hip socket, causing excessive coverage of the femoral head. This overhang can also contribute to the impingement, causing pain. We can see both cam and pincer lesions in X-ray images. Patients may have one or both deformities, with both being more common in patients who experience symptoms.
When the hip joint experiences impingement, the deformed femoral head (the cam) can collide with the rim of the hip socket, causing the labrum (a ring of soft tissue around the socket) and the cartilage to be pinched. This can cause the cartilage to wear out and the labrum to tear over time.
As a result of damage to the labrum and cartilage, FAI can lead to hip osteoarthritis (a joint disease that affects the cartilage) over time. Diagnosis relies on the patient’s history, a physical examination, and X-ray imaging of the hip and pelvis bones. Initial treatment usually involves non-surgical methods but, if these methods do not work, a surgeon who specializes in the treatment of bones and muscles (orthopedic surgeon) may consider surgery.
What Causes Femoroacetabular Impingement?
Femoroacetabular impingement, a hip condition causing pain and damage, is still being studied to understand its causes. There’s evidence that genes might play a role in the abnormal hip structure involved in this condition. Some studies have looked at specific genetic variations, like GDF5, FRZB, DIO2, and HOX9.
One study found that the FRZB gene affected the shape of the top part of the thigh bone (femur) as shown on X-rays. This change in shape was linked to an increased risk of osteoarthritis in the hip. The DIO2 gene was also connected to a specific shape of the femur and a higher risk of hip osteoarthritis. Looking at the HOX9 gene in a Japanese population, it was found to contribute to a specific hip lesion.
Studies also suggest a higher chance of femoroacetabular impingement in athletes because of a particular deformity called “cam deformity”. Teenage athletes involved in high-intensity sports were found to be ten times more likely to have a cam deformity and impingement compared to teenagers not involved in high-intensity sports. It’s thought that more stress on the hip during growth can cause extra bone to form, which results in a cam deformity and subsequent impingement.
Femoroacetabular impingement has also been noticed in patients with a history of slipped capital femoral epiphysis (SCFE). SCFE is a condition where the growth plate in the hip slides out of place during childhood. Even after surgery to fix it, there can be lasting changes to the shape of the hip that can cause impingement.
Risk Factors and Frequency for Femoroacetabular Impingement
Femoroacetabular impingement (FAI) is a health issue found in roughly 10 to 15% of the adult population. Often, FAI affects adolescents and young adults before arthritis symptoms appear on X-rays. The prevalence of this condition can be higher amongst athletes, with around 55% reporting symptoms. However, it’s interesting to note that some individuals have the physical features of FAI, but do not experience any symptoms.
- In a study by Frank and team, 37% had cam deformity and 67% had pincer deformity, even though these individuals didn’t have symptoms.
- When looking at athletes, 54.8% showed cam deformity and 49.5% pincer deformity.
- Compared to non-athletes, who showed lower rates of 23.1% for cam deformity.
- Cam deformity is more common in men, showing in 9 to 25%, while in women it is 3 to 10%.
- On the other hand, pincer lesions occur more frequently in women (19.6%) than in men (15.2%).
Signs and Symptoms of Femoroacetabular Impingement
When diagnosing hip pain, it’s important to understand the patient’s medical history. Doctors will ask about past episodes of trauma, infection, hip diseases like slipped capital femoral epiphysis or Legg-Calve-Perthes disease, as well as any involvement in sports or other physical activities. One common cause of hip pain is femoroacetabular impingement, which typically comes on gradually and may become worse with movement like squatting, driving, and sitting for extended periods. This condition can cause pain not just in the hip, but also in the groin and thigh areas. Some patients may describe their pain with a ‘C sign’, using their finger and thumb to indicate where it hurts. Additional symptoms could include clicking, popping, and catching sensations in the hip, which may suggest further injury.
The physical exam for a patient with hip pain includes observing their walk, testing their hip movement and strength, and performing special tests to pinpoint the source of the pain. A telltale sign of hip muscle weakness or failure is an abnormal gait known as Trendelenburg gait or abductor lurch. Patients with femoroacetabular impingement often show a decrease in hip flexibility and rotation, as well as pain when the hip is flexed, adducted, and internally rotated — a positive “anterior impingement sign”. Doctors might also perform a test called the FABER (hip Flexion, ABduction, and External Rotation) to check for damage to the labrum, a rubbery tissue that follows the outside rim of your hip joint socket. Snapping hip syndrome, a condition where the hip makes a snapping or popping noise when it’s moved, might also be identified during the exam. It’s crucial to separate this from impingement, although both may occur together.
Testing for Femoroacetabular Impingement
After your doctor has examined you and thinks you may have a hip issue like femoroacetabular impingement (which is when the ball and socket of the hip joint don’t fit together properly), they will likely order X-rays of the hip to get a better look. The X-rays should include images taken while you’re standing, looking at the hip from the front and the side. These pictures will allow the doctor to see the structure of your hip and its bones and see if there are any abnormalities.
Standing X-rays in particular can help to spot conditions like arthritis or hip dysplasia, which are conditions affecting the hip joint and can cause pain. Symptoms of femoroacetabular impingement, such as abnormal growth around the hip joint (known as cam and pincer lesions), can also be detected using these X-rays. Hip dysplasia, which is when the hip socket is too shallow and doesn’t properly cover the ball of the hip joint, can be identified by measuring the lateral center edge angle (LCEA). If this measurement is less than 25 degrees, it could indicate hip dysplasia.
The doctor will also examine the X-rays for a condition called a pincer deformity, which is an excess bony growth on the edge of the hip socket, and a cam deformity, which is an excess bony growth on the ball of the hip joint.
Other X-ray views, like the false profile view and Dunn view, can also help give a detailed picture of the hip. The false profile view helps see how much of the hip is covered by the acetabulum (the socket of the hip joint), by measuring the anterior center edge angle (ACEA). If this measurement is less than 25 degrees, it could suggest hip dysplasia. A pincer deformity might show up as an increased angle (over 40 degrees). The Dunn view, a side view taken at an angle, can further help see a cam deformity.
Your doctor may also use magnetic resonance imaging (MRI), which provides a three-dimensional view of the hip joint, to see things in more detail. An MRI can help to see if the labrum (the ring of cartilage surrounding the hip socket) or cartilage has been damaged. It also helps to spot other conditions that may cause hip pain, such as avascular necrosis (a condition where bone tissue dies due to lack of blood), stress fractures (small cracks in the bone), and tendonitis (inflammation in a tendon).
Treatment Options for Femoroacetabular Impingement
Femoroacetabular impingement (FAI), a hip joint problem, can be managed using both non-surgical and surgical methods. We usually try non-surgical treatments first before considering surgery. These mainly include physical therapy, modifications to daily activities, and pain medication (usually anti-inflammatory drugs). For some, an injection into the joint, containing a local anesthetic and a steroid, can help with both diagnosis and easing the pain. If these methods don’t work, and if the pain is significantly affecting a person’s quality of life, then we may consider surgery.
When it comes to surgery, we generally focus on removing any extra bone causing the impingement and repairing any necessary soft tissue. These surgeries can be done using a traditional ‘open’ method or through a less invasive process known as arthroscopy. One way the surgery can help is by removing extra bone found on the femoral head-neck junction, a procedure known as a femoral osteoplasty. If a pincer lesion, an extra bit of bone, is found on the acetabulum, the cup-shaped socket part of the hip joint, we perform an acetabular osteoplasty. Getting rid of the extra bone can improve the range of motion of the hip joint and reduce pain.
Sometimes, the ring of rubbery tissue around the socket, known as the labrum, may also be damaged due to the impingement. If it’s spotted during the surgery, it can be either repaired or cleaned out, depending on the extent of the damage. If we find damaged cartilage from the impingement, we can stimulate new cartilage growth. Just bear in mind that this new cartilage would be a bit different from the original one, known as articular cartilage.
Now, if the images show hip arthritis, surgery for FAI is not recommended because it does not address arthritic pain. Rather, patients with hip arthritis should receive treatment specifically for arthritis. For severe arthritis cases, a hip replacement might be considered if all other treatment options have been tried. Additionally, some patients may present with hip dysplasia (a misalignment of the hip joint) along with FAI. In these cases, optimal results are obtained when both the problems are treated. A surgical procedure performed on the bony socket (the acetabulum) in the hip, known as a pelvic osteotomy, is sometimes used to improve the alignment of the hip joint and coverage of the ball-shaped head of the femur (the thigh bone).
FAI surgeries traditionally involved an open surgical dislocation of the hip. However, hip arthroscopy is now becoming more popular because it may have fewer surgical risks and complications. Even though the traditional open procedure gives us a better view and allows for more work to be done, recovery is longer due to more significant tissue cuts. Hip arthroscopy, which is more technically challenging, disrupts less soft tissue and involves a smaller incision, which can lead to a faster recovery. Research indicates that results from arthroscopy are similar to those from traditional open techniques for FAI.
What else can Femoroacetabular Impingement be?
Identifying femoroacetabular impingement (a condition causing hip pain) from other similar conditions is crucial. Some of the important conditions to keep in mind are infections, tumors, and fractures. Infections like septic arthritis or bone infections usually result in acute pain, difficulty in weight bearing and fever. Doctors usually use methods like X-ray, MRI and lab tests to confirm these causes. Fractures and tumors are also identified using these methods.
Other conditions causing hip pain, although not urgent, include things like:
- Osteonecrosis (bone death due to lack of blood supply)
- Hip dysplasia (a condition where the hip socket doesn’t fully cover the ball portion of the upper thighbone)
- Iliopsoas tendinitis (inflammation of a specific hip tendon)
- Greater trochanteric bursitis (inflammation of the bursa in the hip)
- Gluteal tendinopathy (a condition causing pain in the buttocks)
- Arthritis (inflammation of the joints)
- Iliotibial band syndrome (a condition causing knee pain)
- Snapping hip syndrome (a condition where a person feels a snapping sensation in the hip when walking or running)
- Lumbar radiculopathy (a condition causing back pain and numbness)
All of these conditions have specific identifying characteristics and symptoms and are diagnosed using either X-rays, MRIs, lab tests, or clinical assessment.
What to expect with Femoroacetabular Impingement
“Femoroacetabular impingement” is a term doctors use to talk about a condition where the bones in your hip joint don’t fit together properly. This irregular fit can lead to damage in the tissues and cartilage of the hip, increasing the risk of developing osteoarthritis, which is a type of arthritis that occurs when flexible tissue at the ends of bones wears down.
Doctors believe that having surgery to treat femoroacetabular impingement might help delay the onset of arthritis. The problem is that this kind of surgery is still relatively new, so we don’t have a lot of information about its long-term effects. However, the information we do have, suggests that it is promising. In fact, a study that looked at both open and minimally invasive (arthroscopic) surgeries showed that over 90% of patients were still doing well five years after their procedures.
Despite these promising results, we still need more research to understand the long-term effects of these treatments.
Possible Complications When Diagnosed with Femoroacetabular Impingement
Surgeries for a hip condition called femoroacetabular impingement can lead to various complications. These can be grouped into serious and minor issues.
Serious problems may include breaking of the thigh bone because too much of the bone is removed during surgery, and a drastic increase in abdominal pressure due to accidental leakage of fluid during the surgery. Surgeons suggest removing no more than 30% of the thigh bone to avoid increasing the risk of breakage. Other serious complications include lung clots, deep joint infections, death of bone tissue due to lack of blood supply, and hip dislocation after the operation.
Minor issues might be bruises, blood clots in the deep veins, superficial infection, and irregular bone formation around the hip. You might also feel discomfort and numbness in the outer thigh due to injury to a nerve during surgery. Temporary numbness in the groin area may also occur if too much pressure is applied during surgery, alongside instances of pain during intercourse. The most frequent complications are bruises and nerve damage due to traction. Irregular bone growth can often be controlled or prevented using anti-inflammatory medicines like indomethacin after surgery.
Here are the listed complications:
- Major complications:
- Bone fracture at the thigh
- Increased abdominal pressure
- Deep joint infections
- Bone tissue death due to lack of blood supply
- Postoperative hip dislocation
- Minor complications:
- Bruises
- Blood clots deep in the veins
- Numbness and discomfort in the outer thigh
- Temporary numbness in the groin area
- Pain during intercourse
- Superficial infection
- Irregular bone formation around the hip
Recovery from Femoroacetabular Impingement
If you’ve had surgery for something called femoroacetabular impingement, you will usually stay off your operated leg (assuming a weight-bearing status) for around 2 to 6 weeks. This amount of time varies depending on the surgeon’s instructions. The aim of not bearing weight is to avoid putting unnecessary pressure on the reshaped parts of your thigh bone or hip socket, and to protect any repairs that have been done to the labrum (a ring of cartilage that surrounds the hip socket).
Physical therapy will usually start soon after your surgery. The focus, for the first 3 to 4 weeks, will be on passive movements of the hip. This means you will perform exercises that involve moving your hip without engaging your muscles. After about four weeks, you’re typically able to start bearing weight on your leg and can begin exercises that involve active movements, which is when you use your muscles to move your hip.
From 4 to 8 weeks after surgery, you will slowly gain strength and learn how to walk again correctly. Then, from 8 to 12 weeks, the focus of your therapy will shift towards regaining full hip strength, improving your core strength, balance, and proprioception, which is the ability to sense the position and movement of your body parts.
After 12 weeks, the exercises will become more intense, including activities like jogging, jumping, and agility exercises. The ultimate goal of all this is to get you ready to go back to playing sports or other exercise activities that you enjoyed before the surgery.
Preventing Femoroacetabular Impingement
People diagnosed with femoroacetabular impingement, a condition where the hip bones are abnormally shaped and rub against each other, should be aware of the increased risk of developing arthritis in the future. This risk remains, no matter what type of treatment they receive, including non-surgical or surgical options.
Surgery can be carried out to effectively manage symptoms and enhance life quality. However, it’s still uncertain whether surgery can delay or prevent the onset of hip arthritis, a condition causing inflammation and stiffness in hip joint.
It’s vital that patients comprehend that even after having surgery, they might still develop arthritis in the future, experience arthritis-related pain, and potentially need a hip replacement surgery. Therefore, it is crucial for patients to actively participate in making treatment decisions considering the potential risks and benefits.
