Hip Resurfacing

Hip resurfacing is similar to total hip replacement, except that the top of the femur is capped with a spherical surface (sort of like capping a tooth) rather than cutting off the ball and placing a stem into the femur. Otherwise, the ball moves within an artificial hip socket very similarly to a hip replacement.

Hip resurfacing is not new. A number of the procedures were performed in the early 1980's. However, the engineering and materials were not yet advanced enough, and most designs 20 years ago utilized a metal cap that moved within a plastic liner cemented into the patient's acetabular socket. With these early designs, the cement interface frequently failed and the plastic wore out, leading to early failure in young patients.

The concept has now been revisited, primarily by British surgeons. McMinn and others in Birmingham, England, have developed a newer variation that involves a metal cap that moves smoothly in a highly polished metal socket (both parts are made of cobalt chrome). This device is known as a Birmingham Hip Resurfacing arthroplasty, and while there are some competing designs likely to obtain approval soon, at the time of this writing, this is the first of the newer generation hip resurfacing device approved by the FDA for use in America. It was approved in 2006 and has been been adopted here as American surgeons learn the surgical technique. After visiting surgeons in England, Dr. John Keggi and I together performed the first Birmingham hip resurfacing (BHR) in Connecticut in November 2006, and within a few months, the surgery has now become more widely available by other orthopaedic surgeons as well.

Who Is A Candidate For Hip Resurfacing?

This type of surgery has several distinct advantages and disadvantages when compared to total hip replacement. For the right patient, it is an excellent alternative to total hip replacement, and overseas there is now 10 year follow-up with over 60,000 patients, so far with spectacular results. However, not all of the patients who arrive in my office requesting the procedure are good candidates for it.

The procedure is principally designed for younger, more active patients who need a greater range of motion than typical total hip replacement patients. It is also for patients who need to be able to eventually participate in impact activities such as running. Activities such as hiking, swimming, cycling, doubles tennis, and golfing can all be accomplished just fine with a total hip replacement, but for patients who want to continue to participate in jogging, downhill skiing, martial arts, or other rigorous activities this represents the best option available.

The FDA currently recommends that candidates be 65 years or younger for men, and 60 years or younger for women. This is primarily because of the increased bone density needed to support the cap, and it is possible to fracture the bone at the neck of the femur. Some patients outside of this age range can be considered, although a bone density scan may be needed to determine that bone quality is adequate. Similarly, some younger patients may not be candidates
if they have soft or osteoporotic bone.

Because of the metal on metal bearing surface and subsequent accumulation of metal ions in the body, patients with true metal allergies or kidney disease are also not good candidates (the kidneys are responsible for excreting metal ions). For this reason, we also will typically avoid women of childbearing age who may potentially become pregnant (a ceramic total hip is a better choice for those patients).

Finally, because the resurfacing relies on the bone of the femoral neck and head to support the metal cap, patients who have significantly abnormal bone anatomy are not good candidates. This may include those with previous fractures or surgeries, or patients who have such advanced degenerative disease that there is insufficient bone stock to support a resurfacing. These patients are better served with total hip replacements.

Advantages of Hip Resurfacing

There are several advantages to hip resurfacing. The first is increased range of motion. Because the diameter of the ball (femoral head) within the socket (acetabulum) is the largest size possible, the allowable range of motion is much better than that of total hip replacement and begins to approach that of a normal hip.

The metal on metal surface also lasts a very long time with very minimal wear. The bearing itself will last many years; the wear rate is much better than that of metal on plastic (polyethylene) and approaches that of ceramics. Typically, the bone it is attached to wears out (loosening) before the implant fails.

The metal on metal surface is also durable enough to allow impact activities, which should generally be avoided with ceramic hips.

Another advantage is that when a resurfacing does eventually wear out, it can be converted to a normal total hip replacement relatively easily. In comparison, most total hip replacements require more complex revisions (to remove a stemmed component from the femur) and revision prostheses. The resurfacing "cap" is simply removed similarly to a normal femoral head when converting to a total hip replacement.

Disadvantages of Hip Resurfacing

As I frequently explain to patients who arrive for evaluation for hip resurfacing, there are some disadvantages that they need to be aware of. As noted previously, one disadvantage is the metal on metal wear and the accumulation of metal ions in the body. Although there is a large amount of data from over 60,000 Birmingham hip resurfacings worldwide, as well as data on other metal on metal hip devices going back at least 40 years, there has not been any decisive indication that the metal ion accumulation is responsible for any detrimental problems in most patients. However, we may yet find in the decades ahead that there is a small increased chance of problems from heavy metal ion accumulation. This would also present a problem for the (very rare) patient who has a true metal allergy.

Another disadvantage is that there is some risk of the femur breaking. The neck of the femur, or the part just below the ball, can fracture either during or after the procedure if it is not strong enough. This risk is low, however.

One more disadvantage is that although the resurfacing is less invasive to the bone, and patients retain more "factory original" parts, most surgeries to perform hip resurfacing actually are more invasive than traditional total hip replacements. This is because the femoral neck and "ball" are cut away with total hip replacement, leaving room to work on the socket (acetabulum). If the bone of the femoral neck is to be spared for hip resurfacing, this necessitates extensive soft tissue releases to get the femoral head out of the way so that the socket may be worked on.

The Future of Hip Resurfacing

In most of the world, hip resurfacing is conducted via a posterior approach that requires splitting gluteus maximus and completely detaching gluteus medius, piriformis, quadratus, obturator, and gemelli muscles from the bone in addition to releasing the entire hip capsule circumferentially. This often results in a pronounced limp until the muscles have healed sufficiently.

We recently began performing anterior Birmingham Hip Resurfacings (e.g., from the front) in 2007 after working on adapting the approach at the cadaver laboratory at Yale and working on the necessary modifications for 6 months. At the time of this writing, our practice has been able to offer this surgery with a direct anterior approach that does not require detaching any of the above muscles, only releasing the capsule, because the approach is from the front of the hip. This better preserves the blood supply to the femoral head as well. Early results have been very promising with this new procedure and approach, and thus far patients have had faster rehabilitation and few significant complications. It remains a very active area of research and will be followed in the years ahead.

Please remember the information on this site is for educational purposes only and should not be used to make a decision on a condition or a procedure. All decisions should be made in conjunction with your surgeon and your primary care provider.