| Summary: | <p>The Oxford Unicompartmental Knee Replacement (OUKR) is an effective treatment for symptomatic end-stage anteromedial osteoarthritis. In contrast with data from specialist centres, the National Joint Registries suggest a higher revision rate than total knee replacement. The cementless version of the OUKR was introduced to prevent cementation errors, improve fixation, reduce the incidence of radiolucent lines and ultimately reduce the discrepancy between the results of specialist centres and National Joint Registries. There are, however, anecdotal reports of tibial plateau fractures with cementless fixation. The aim of this thesis was to assess the clinical outcome and key biomechanical aspects of the fixation of the cementless OUKR.</p> <p>A systematic review demonstrated that modern cementless unicompartmental knee replacements (UKRs) are safe and effective.</p> <p>The cementless OUKR had a 10-year survival of 97% and 88% good or excellent clinical results in a prospective, consecutive case series of 1000 cases from two centres.</p> <p>The primary stability of the cementless OUKR relies on the interference fit. The 5-year results of a randomised controlled trial using radiostereometric analysis demonstrated that cementless components are as stable as cemented. Although sufficient in providing component stability, the interference fit could be excessive increasing the risk of fracture. A biomechanical test was carried out to study the effect of interference on the force required to implant the tibial component (push-in force) and the fixation strength (pull-out force). The results demonstrated that a reduction of the interference up to 50% significantly reduces the force required to implant the components without affecting their primary stability.</p> <p>In conclusion, the cementless fixation of the OUKR is safe and effective, with excellent long-term survival. The stability of cementless components is reliable and at least as good as that of the cemented implant. However, the interference fit around the tibial component is excessive. A reduced interference fit could decrease the risk of fracture without affecting the stability of the components.</p>
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