What is impingement, what causes it after resurfacing, what are the symptoms and what do you advise patients to do if they experience it?

Dr. Thomas Gross
Impingement in hip resurfacing is painless. I have seen it many times as a focal area of neck narrowing on XR.I am aware of one small report on painful impingement. I am skeptical. I believe those patients may have had pain from another cause. At any rate, the evidence presented was anecdotal and did not convince me that a cause and effect relationship existed. it is talked about a lot by the experts, but convincing evidence is lacking.

I understand impingement to be as Dr. Ganz described it in hips with certain deformities (without implants).There is cam and pincer type. People with these deformities have them from an early age and are asymptomatic for many years except possibly noticing a lack of motion of their hips. These deformities do cause extra stress on the hyaline and labral cartilage of the hip joint. Eventually these cartilage structures fail. This is when pain starts. Hip Impingement DOES NOT hurt. Cartilage tears as a result of impingement HURTS. I have seen hundreds of hip XR with hip impingement deformities that are painless (on the opposite hip of patients that I resurface). With time, many of these patients become painful when they develop cartilage damage.

Therefore, it is unlikely that impingement after hip resurfacing hurts. there is no cartilage to tear. I think that patients who hurt after resurfacing may have other problems such as:
Failure of bone ingrowth into the socket: sometimes difficult to diagnose. serial XR over 6 months to 2 years are best.
Psoas tendonitis: a clinical diagnosis. No exact diagnostic test exists. Psoas injection may help.
Wear related inflammation: metal ion testing and MRI are helpful.
If you have a painful hip resurfacing, careful evaluation by an experienced resurfacing surgeon may lead to the answer. Sometimes it takes quite some time to come to a conclusion. For example the XR changes of socket failure of ingrowth can sometimes take years to develop.


Dr. Peter Brooks
Femoroacetabular impingement (FAI) is being increasingly recognized as a major cause of early adult hip arthritis, especially in men (in women, dysplasia is more common). In FAI there is abnormal hitting of the ball against the edge of the socket during motion, due to deformity of the ball, socket, or both. As one bone hits the other ("impingement") there can be damage to the cartilage and labrum which leads to arthritis.

In the most common form, there is a bony bump on the front of the femoral neck. Many patients have to turn their leg outwards as the flex up, due to this. They cannot bring their knee straight up to the chest, it has to turn.

Operations have been developed to remove this bump, as well as other impinging bone, and to repair the labrum. Some can even be done arthroscopically.

Unfortunately, if there is even a bit of arthritis already present, these operations do not last long, so most surgeons go ahead and recommend total hip replacement or resurfacing.

Total hip replacement generally removes so much bone that the impinging bone is taken as well, so impingement is unusual after THR.

With hip resurfacing, however, the surgeon must take into account all the deformity of the femoral neck and socket. Realizing that a great many patients being resurfaced have FAI, and the femoral neck is preserved, you can see that simple resurfacing without addressing the impingent can result in impingement after surgery.

The experienced hip resurfacing surgeon will remove the offending bone from the femoral neck and the edge of the socket.

Failure to address impingement during resurfacing can lead to several problems. First, there may be persistent pain. This may be one reason that resurfacing has a higher incidence of groin pain than traditional total hip replacement, where the femoral neck is gone, and cannot impinge. Secondly, whenever there is bumping together of bone during movement, the ball and socket may be pried apart. In going in and out this way, edge wear is set up leading to higher metal debris, ion levels, etc.

Thirdly, range of motion may be limited, so that it may continue to be difficult to reach socks and shoes, like it was before surgery.

Another source of post-operative impingement is component malposition. Here, a socket that is facing too much to the front or back (called anteversion and retroversion), or is too horizontal, results in impingement of the femoral neck against the edge of the socket. This leads to notching of the neck and limited motion.

Impingement is an interesting an important topic, whether it occurs before or after hip resurfacing. The fact that it is much more likely with resurfacing than with replacement is another reason that hip resurfacing is a more difficult procedure."