The hip resurfacing devices are metal-on-metal articulating devices which differ from total hip replacement devices because they are more bone conserving and retain the natural geometry (so-called large ball THR devices share this trait). A THR requires that the upper portion of the femur bone be cut off to accept the stem portion of a THR device. The femur cap of the hip resurfacing devices does not require the femur bone be cut off; instead the top of the femoral head is shaped to closely fit the underside of the cap. Both hip resurfacing and hip replacement require that a cup is placed in the acetabulum of the hip socket. The main advantage of the hip resurfacing surgery is that when a revision is required, there is still an intact femur bone left for a THR stem. When a THR stem requires a revision, the metal stem in the femur has to be removed and often more bone is lost in the process of removal and replacement with a larger diameter stem. Having a hip resurfacing at a younger age means that a revision will likely be easier to perform when required.
Recent studies have shown that the outcome of a hip resurfacing is dependent on surgeon experience and that proper positioning of hip resurfacing components is crucial. Therefore, in addition to ensuring that a proven device is used, patients should take care in selecting a surgeon with experience and a good track record.
Although formal labeling restrictions exist in some countries, including the United States, hip resurfacing may allow younger, active people to return to many activities they enjoyed prior to their hip problems, which is an advantage over a traditional hip arthroplasty. The large size cap and cup of the hip resurfacing devices are the same size as a person's original ball and socket and thus are less prone to dislocation.
An often forgotten but very important advantage of hip resurfacing and thereby the retention of the femoral neck is the fact that hip resurfacing has the least measurable amount of "stress shielding" when compared to any type of THR. This means that with hip resurfacing the femur's upper portion fully retains its natural mechanical characteristics under load, also ensuring less disturbance of the processes that place inside bone that is alive.
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