Figure 1: Hip resurfacing
Since the 1990's there has been a significant increase in the number of hip resurfacings being carried out in the UK. This type of implant was developed in Birmingham and still remains the market leader. It was developed on the basis that it was an optimal implant to use in younger patients, as it conserved bone on the femoral side and the large head gave greater stability. However, as more and more implants have been implanted and other companies have developed their own versions, which had different geometries, problems have emerged. It has become clear that a minority of patients will develop soft-tissue reactions due to the production of metal debris. It seems to be more common in those with smaller femoral head sizes. It is currently only recommended in males under the age of 55 and is not carried out by Professor Fehily due to these problems. Following multiple reports of problems with these implants, the numbers being implanted in the UK have dropped significantly.
Problems have also emerged with implants where there is a large metal head on a stem. Recent evidence has shown that these implants (which were implanted because the surgeons felt that they were more reliable then the resurfacing implants) may actually be doing worse then the resurfacing ones. It is thought that this is due to wear at the junction between the head and the stem.
Patients who do develop problems will usually be within 5 years of their surgery. They will have a deep seated pain. There may or may not be a squeak as the metal components rub against each other.
Plain x-rays may show that the cup was mal-positioned and more vertical then recommended. However problems can occur even in implants that have been well positioned. On the x-ray, there is usually no evidence of loosening and no indication of the soft-tissue damage that may be present.