There is a condition of the hip called femoroacetabular impingement (FAI) that can lead to early hip osteoarthritis. In an effort to prevent arthritis, there are some experts who suggest routine screening for this problem and early treatment.
But the cost of performing X-rays and/or MRIs on everyone may not yield cost-effective results. That's why these Canadian researchers tested 200 adult volunteers (ages 21 to 50) for the presence of femoroacetabular impingement (FAI). None of them had any previous hip problems.
Impingement refers to some portion of the soft tissue around the hip socket getting pinched or compressed. Femoroacetabular tells us the impingement is occurring where the femur (thigh bone) meets the acetabulum (hip socket). There are several different types of impingement. They differ slightly depending on what gets pinched and where the impingement occurs.
The goal of the study was to determine the prevalence of the Cam-type of FAI in the general adult population. Prevalence refers to how many people have a particular condition at any one point in time. The cam-type of impingement is the most likely to set up conditions ripe for joint wear and tear. This type occurs when the round head of the femur isn't as round as it should be. It's more of a pistol grip shape. It's even referred to as a tilt or pistol grip deformity. The femoral head isn't round enough on one side (and it's too round on the other side) to move properly inside the socket.
The result is a shearing force on the labrum and the articular cartilage, which is located next to the labrum. The labrum is a dense ring of fibrocartilage firmly attached around the acetabulum (socket). It provides depth and stability to the hip socket. The articular cartilage is the protective covering over the hip joint surface. This abnormal contact between the femur and acetabulum is the leading cause of labral tears and degenerative hip arthritis. The authors tried to establish what might be considered normal in terms of the femoral head-neck contours. Knowing what falls within the range of normal limits helps identify those who are outside those parameters. Measures used to assess the volunteers for the presence of Cam-type femoroacetabular impingement (FAI) included hip internal rotation, positive impingement sign, and contour/angle of the femoral head-neck junction. MRIs were used to provide information on hip contours and angles. With 200 volunteers enrolled in the study, there were a total of 400 hips to report data on.
A study like this that recruits volunteers from the general population and checks to see how many have femoroacetabular impingement is helpful. By studying people who have no symptoms but who have the problem, it is possible to see over time whether or not they will develop arthritis. It also helps find risk factors for impingement. In this study, they specifically looked at age, gender (male versus female), body-mass index (a measure of obesity), and ethnicity. These potential factors may put people at increased risk for impingement and then for going on to develop arthritis later.