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 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.
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