Risk of Hip Impingement DevelopingAthletes using hip flexion while trying to internally rotate the hip may end up with some difficulty with this motion if the femur collides with the pelvis. A painful condition called femoroacetabular impingement or FAI may develop.
Left untreated, FAI can progress to become hip arthritis. That would not be good for the young soccer player, swimmer, cyclist, or rowing athlete with the potential for FAI. The authors of this study thought perhaps it would be possible to predict, recognize, and treat early on to avoid late complications like osteoarthritis. They specifically studied individuals with the cam type of FAI.
Here's a bit of background information to help explain cam impingement. Femoroacetabular refers to the place in the hip where the round head of the femur (thigh bone) comes in contact with the acetabulum or hip socket. Two types of impingement are known to cause pinching of the soft tissues in this area.
The cam-type impingement 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 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.
The rim of the cartilage hangs too far over the head. When the femur flexes (bends) and internally rotates, the cartilage gets pinched. Over time, this pinching or impingement of the labrum can cause fraying and tearing of the edges and/or osteoarthritic changes at the impingement site.
As we mentioned right at the first, every time the athlete bends the hip up fully combined with internal rotation of the hip, the femur jams into the pelvis. Besides pain, the athlete experiences decreased hip motion, and difficulty with activities like sitting, climbing stairs, squatting, changing clothes, driving, and sports participation.
Three groups of participants were examined and compared to look for risk factors that might predict the development of cam impingement. The first (control) group was completely normal with no symptoms and no evidence of impingement. The second group had a known problem with cam impingement. And the third group had obvious hip changes consistent with a diagnosis of cam impingement but no symptoms of any kind.
Hip motion was measured. CT scans and X-rays were taken. Various angles and ratios were calculated. A special three-dimensional (3-D) motion picture was taken to look for abnormal hip movement/motion patterns.
A special software program was used to help analyze and compare kinematics (joint motion) of the different patients. They also looked at shape and fit of the femoral head in the acetabulum in relationship to hip joint kinematics.
They were able to see that the control group had no risks that might predict the development of femoroacetabular impingement (FAI). Patients in the group without symptoms but obvious changes seen on X-rays were more likely to develop hip impingement compared with the control group but less likely when compared with the group who already had known FAI.
The predictive risk factors for the development of cam-type FAI included: 1) cam size (larger has worse prognosis), 2) acetabular coverage, and 3) amount of femoral rotation or twist called anteversion or retroversion (depending on which direction the hip is twisted). Up to 15 per cent of the general population has one or more of these predictive factors.
It's clear that people without symptoms and no sign of hip problems don't need any further treatment or intervention. At the same time, those with painful, limited hip motion and clearly documented femoroacetabular impingement (FAI) need careful management. Surgery is done to reshape the femoral head and reduce the risk of osteoarthritis.
But what should be done to best aid those individuals in the middle group? Remember, these are the folks who have some anatomic changes in the hip suggestive of FAI but no symptoms yet. The authors suggest more research is needed before suggestions and guidelines can be issued.
Questions to be answered by future studies include: 1) Is there any cartilage damage occurring in people with signs of impingement but no symptoms? 2) Should sports participation be discouraged? 3) Or is it only necessary to limit the use of certain hip positions? 4) Will the group with signs of FAI but no symptoms eventually develop a full blown case of FAI?
Emmanual A. Audenaert, MD, et al. Hip Morphological Characteristics and Range of Internal Rotation in Femoroacetabular Impingement. In The American Journal of Sports Medicine. June 2012. Vol. 40. No. 6. Pp. 1329-1336.
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