Investigation of retrieved femoral heads and cups

Retrieved ceramic femoral heads and acetabular cups were investigated. On the basis of the case studies, the reasons for revision are discussed. Wear patterns and wear rates were found to differ from those observed in hip simulating testing. Monolithic ceramic cups showed a high wear rate. Owing to their limited range of motion, ceramic ,,mushroom heads" are associated with impingement that leads to a high risk of cup loosening, high wear rates and in vivo fractures. The combination of ceramic ,,mushroom heads" and cups is not recommended. An evaluation of complications shows that some can be explained by patient behaviour - e.g. Japanese sitting position, horse riding. Designers need to develop new concepts offering a larger range of motion, for example, with head diameters of 32 and 36 nun that reduce-the risk of impingement, subluxation and dislocation, while increasing the range of motion. The potential of ceramic/ceramic coupling has been known since the 70s, and ceramic concepts for total hip replacement are currently experiencing a renaissance, although further developments are still possible.