Trial Lecture - time and place
See Trial Lecture.
Adjudication committee
- 1. opponent: Professor Nils Hailer, Uppsala University Hospital
- 2. opponent: Associate Professor Tatu J. Mäkinen, University of Helsinki
- 3. member of the adjudication committee: Associate Professor Kristina Lindemann, University of Oslo
Chair of the Defence
Professor Hanne Dagfinrud, University of Oslo
Principal Supervisor
Stephan Maximilian Röhrl, Oslo University Hospital
Summary
The final outcome of total hip arthroplasty depends not only on the skills of the surgeon, but also the quality of the implants that are used. Hip implant commerce has become a multimillion-dollar industry, which consequently has motivated development of numerous new implants, sometimes on the expense of proper testing prior to release. Another issue has been the lack of proper tools to evaluate and predict the implant durability. Radiostereometric analysis (RSA) has emerged as promising tool for this purpose, predicting long-term survival from measurements of early implant migrations. The purpose of this thesis was to review the issues of radiostereometric analysis, as well bone density measurements and other tools in the evaluation of new implants. We examined the effect of radiopaque cement on bone density measurements and found that its presence may cause an underestimation of bone density changes over time. We looked at three new hip implants with features that were thought to improve longevity; one cemented stem, one polyethylene cup and one cementless stem. Each were evaluated by radiostereometric analysis. The cemented stem exhibited a similar migration pattern to a well-documented control stem, predicting good long-term survival. Regarding the cemented cup, we specifically looked at surface wear, as this is associated with osteolysis and loosening. We measured low wear compared to current standards, also predicting good long-term survival. The cementless stem had similar migration profile to the stem with “standard” coating, again predicting good long-term survival, but not superiority over its older and cheaper counterpart.
Radiostereometric analysis has undisputedly evolved into the most accurate tool of evaluating hip implant survival. Nevertheless, it is still not a requirement prior to implant release. As we have highlighted the flaws of current methods of implant evaluation and regulations, we are hoping to create an incentive for improvement.
Additional information
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