Physical Therapy in San Jose, Los Gatos, Foster City and Burlingame for Hip

If you've ever had squeaky shoes while trying to sneak into a movie theatre, church, synagogue, or down a quiet hallway, you know how annoying it can be. Imagine if that noise was coming from your hip replacement! At least with a squeaky pair of shoes, you can take them off. Squeaky hip replacements are not so easy to correct.

The problem of squeaking hips after joint replacement has increased in the last 10 years with the increased use of hard-on-hard bearings. What do we mean by hard-on-hard bearings? The two main parts of the hip that are replaced include the round head at the top of the femur (thigh bone) and the cup-shaped hip socket.

The materials used for these component parts can be ceramic-on-ceramic, metal-on-metal, or metal-on-polyethylene (plastic). Metal-on-metal and ceramic-on-ceramic are the hard-on-hard bearings. Ceramic-on-polyethylene and metal-on-polyethylene are considered hard-on-soft bearings.

So what is it about the hard bearings that leads to squeaking in some patients but not in others? This question has puzzled many surgeons for quite a while now. Research into the problem is beginning to shed some light on the situation. It appears that there are three main factors involved and usually more than one reason for the squeaking.

Patient factors such as body size and mass (larger), height (taller), and activity (hip flexion) may be part of the problem. There's not much a person can do about their height to change the squeaking. But they can be advised to avoid activities or movements that cause the squeaking.

Sometimes, it's not the patient at all but rather the way the implant was placed in the hip. The wrong angle, a slight twist of the cup (socket) piece, or a little bit of both has been linked with squeaking.

But the most likely factor is the implant itself and in particular, the materials it is made of. The newer implants made of titanium alloy are more flexible and less stiff. This feature could increase the vibrational force that creates friction and squeaking. Other contributing factors include loss of fluid lubricating the hip, tiny particles of metal or other debris from the implant, or damage to the surface of the implant.

When surgeons remove squeaking hips, they often find a stripe along the implant where stress and friction have worn it down. Since squeaking occurs most often with hip flexion (bending, walking), the location of the stripe suggests edge-loading wear. Edge-loading refers to the upper/outer (superolateral) edge of the liner of the socket coming in contact with the upper (superior) surface of the femoral head.

Squeaking doesn't develop until the patient has had the implant for quite a while (six months or more). The time delay is consistent with the stripe wear just described as well as the loss of lubricating fluid. Likewise, metal debris caused by impingement (one part of the implant is pinching against another) accumulates over time.

What can be done about this problem? Well, the first step is to determine what's causing the problem and find ways to avoid it in future patients. But for those who already find it impossible to sneak into a room after a meeting has already started -- that requires a different solution.

Since pain is not usually an issue and the hip moves just fine, removing and replacing the implant isn't the first treatment choice. Often the squeaking is intermittent (comes and goes). Having the patient pay attention to when the hip squeaks and then avoiding those movements or activities is the first step.

But if the problem continues, the patient should see his or her surgeon for a follow-up evaluation. It could be that the cup liner is cracked or fractured and needs to be replaced. If the cause is a malpositioned implant or imbalanced soft tissue tension, then surgery may be needed to correct those issues.

Efforts are being made to improve implant design while studying the causes of squeaking hips. The hard-on-hard bearings (metal-on-metal and ceramic-on-ceramic) are still great implants (especially for young, active patients) so there's no need to stop using them. We just need to find ways to prevent the problem -- perhaps better surgical techniques will be part of the solution. Only time will tell.

Reference: William L. Walter, MBBS, FRACS, PhD, et al. A Review of Squeaking Hips. In Journal of the American Academy of Orthopaedic Surgeons. June 2010. Vol. 18. No. 6. Pp. 319-326.