The use of 3D surface analysis techniques to investigate the wear of matt surface finish femoral stems in total hip replacement

摘要

Total hip replacement is one of the most common surgical procedures carried out both in the UK and Worldwide. With an increasing number of younger patients undergoing the procedure, there is an emphasis on increasing the longevity of prostheses. The following reports on a number of component studies which, when combined give an insight into the mechanism of wear behind the loosening and failure of matt surface finish femoral stems. By examining stems which have been explanted from patients, a method of wear classification has been developed, and also 3D surface measurement techniques have been employed to quantify wear through parametric characterisation and also volume analysis. Initial findings suggested that the wear of matt finish femoral stems differs to that of smoother polished femoral stems. Studies also provide information regarding the nature of bone cement, its behaviour and the interaction between stem and cement following insertion of the stem. It was found that geometric change in bone cement occurred during polymerisation, and following curing. This geometric change presented itself in the form of differential shrinkage. This shrinkage of cement was observed initially through 3D surface topography analysis and later confirmed with geometric measurement techniques. The presence of voids between stem and cement give rise to the possibility of debris creation and transportation, adding to the evidence for a difference in wear mechanism between polished and matt surface finish femoral stems. Some progress was made towards replication of wear in vitro which has future possibilities for wear screening of materials and designs of future prostheses. The overall conclusion of the study suggests that the dominant wear mechanism which occurred between the stem and bone cement was abrasive in nature and this is likely to explain the accelerated wear of matt stems which has been reported by clinicians and researchers.