In order to overcome various issues (including small sample size, short follow up, bias in patient selection) associated with the studies described above, TOPKAT was set up (Beard et al, 2013). The aim of TOPKAT is to assess the clinical and cost effectiveness of TKAs compared to UKAs in patients with medial compartment osteoarthritis. The design of the study is a single layer multicentre superiority type randomised controlled trial of unilateral knee replacement patients. It aimed to recruit 500 patients from approximately 28 secondary care orthopaedic units from across the UK including district general and teaching hospitals. The study is pragmatic in terms of implant selection for the knee replacement operation. Participants will be followed up for 5 years. The primary outcome is the Oxford Knee Score, which will be collected via questionnaires at 2 months, 1 year and then annually to 5 years. Secondary outcomes will include cost-effectiveness, patient satisfaction and complications data. Patient recruitment has been completed. Preliminary analysis of the one year data does show small but significant advantages of UKA with some outcome measures. No firm conclusions can be drawn from this study until five year data is available (Beard et al, 2016).
