Metal-on-Metal Hip Resurfacing Viable Option for Younger PatientsHip fusion for younger patients is not the viable option it once was because of its problematic outcomes. Total hip arthroplasties (THAs) or hip replacements are not always a first option for younger patients either because of the arthroplasty's limited survivorship. Because of these issues, the metal-on-metal hip resurfacing (MOMHR) has been tested as a potential treatment for this patient group.
Originally, there were concerns that MOMHR caused problems because of lack of blood supply to the femoral head (head of the thigh bone) or because of femoral head loosening of fracture. However, studies have shown that the procedure can be successful as long as the soft tissue covering the femoral neck is kept intact.
Researchers were also concerned about how the bone cement would affect the healthy bone next to it, due to the high temperatures needed. This was addressed by making some changes in the way the cement was applied.
The author of this article looked at the outcomes of MOMHR compared with hip arthroplasties, or replacements. Unfortunately, studies of more than 10 years aren't available and shorter periods are not as reliable in order to show long-term outcomes. In one study of five years minimum, there was a 98 percent success rate of 144 hips. In another study, using the same system, there was a 99.14 percent success rate out of 230 MOMHR procedures.
some issues that have been brought forth that concerned doctors about the MOMHR included the issue of metal ions, the biomechanics of resurfacing, and bone preservation. In terms of the metal ion issues, there concerns about metal ion exposure that could cross the placenta if a woman was pregnant. However, studies have shown no ill effect on the fetus.
Regarding the biomechanics of MOMHR, it became obvious that the higher volume hip surgeons were able to use templating in order to improve success. Studies have investigated the issue of leg length, comparing MOMHR with arthroplasty and have found that leg lengths and gait analysis were more favorable with the MOMHR than with the arthroplasty.
Bone preservation is less of an issue with MOMHR, however, in some cases, more bone may be removed with MOMHR, depending on the technique and location, when compared to a hybrid arthroplasty.
The author concludes that the current study findings have been adequate for the US FDA to approve its use. There are other designs that will become available, but the MOMHR has given doctors hope that arthroplasties can be avoided in the younger patient population. The success for the procedure lies on proper patient selection and surgeon experience.
William Macauley. Hip Reconstruction - Total hip resurfacing: a viable alternative to total hip arthroplasty in the young active hip patient in the United States? In Current Orthopedic Practice. March/April 2008. Vol. 19. no. 2. pp. 107-109.
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