Hip Revision Surgery : Identification of Genetic Markers and Evaluation of Novel Treatment Strategies

Abstract: Total hip arthroplasty (THA) is, despite its overall good outcome, for some patients followed by hip revision surgery. This seems in parts to be because of genetic susceptibility to revision surgery. The most common reason for revision surgery is aseptic loosening followed by periprosthetic joint infection and dislocation. Cups made of porous tantalum (TM cups) were thought to be favorable in revision surgery to address aseptic loosening, but they seem to confer an increased risk of dislocation. The effectiveness and biocompatibility in vivo of TM cups have not been researched. Dual mobility cups (DMCs) with two articulating surfaces are proposed to prevent dislocation to a higher degree than standard polyethylene liners.Our hypotheses were that TM cups are superior to their historical treatment alternative in terms of re-revision rates; that the combination of DMC cemented into TM cups would decrease the risk for dislocation after revision surgery; that tantalum ion liberation is marginal after the use of TM cups; and that certain risk genes are associated with an increased risk for revision surgery after total joint arthroplasty.Studies I&II were register-based cohort studies comparing the implant survival of TM cups and conventional acetabular reinforcement rings (study I), and the combination of TM cups/DMC with TM cups/standard polyethylene liners (study II). We found that TM cups perform equally well as reinforcement rings, but that the two implants differ in their failure mechanisms. Cementing a DMC into TM cups adequately addressed the issue of recurrent dislocation. In study III we investigated whether tantalum ion liberation does occur after implantation of a TM cups and how this affects patients’ immunological response by comparison of three groups: primary non-tantalum THA, primary tantalum THA and revision tantalum THA. We found the highest concentration of tantalum ions in the revision cases, yet tantalum ions were not associated with an immunological response, and we found no signs of alteration in the investigated lymphocyte subsets. Study IV aimed to identify possible risk genes for revision surgery after total hip or knee replacement by a genome wide association study. We found six significant risk genes for the endpoint revision surgery for any reason, and three for the endpoint revision due to aseptic loosening. We found a variety of suggestive risk genes within the region coding for the ABO-system.In conclusion, the novel treatment options TM cups and DMC show good results in hip revision surgery, but longer follow-up is warranted. The use of porous tantalum seems not to be associated with the immunological activation that can be observed in metallosis. The risk for revision surgery is associated with certain risk genes.