Surgeons disagree about whether to replace the entire knee or just the damaged compartment in patients with medial osteoarthritis, and no robust evidence settles the debate. This matters because both total knee replacement (TKR) and unicompartmental knee replacement (UKR) are standard procedures, yet no large, long-term trial has compared their clinical and cost effectiveness head-to-head. Surgeons choose based on personal preference rather than data, meaning patients may receive one operation or the other without knowing which offers better outcomes or value for the NHS. The TOPKAT trial will recruit 500 patients across sites where surgeons either agree to randomise by device (the same surgeon performs both operations) or by expertise (surgeons specialising in one technique work alongside those specialising in the other). Patients will be followed long-term to measure pain, function, complication rates, and costs. If successful, the trial will give surgeons and patients clear evidence on which procedure works better and at what cost. That could change surgical practice across the NHS, reduce variation in care, and help the health service allocate resources more effectively for one of the most common orthopaedic procedures in the UK.
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In the majority of patients with osteoarthritis of the knee the disease originates in the medial compartment. There are two different approaches to replacing this arthritic area. Some surgeons feel that it is always best to replace both the knee compartments with a Total Knee Replacement. (TKR). Others feel it is best to replace just the damaged component of the knee with a Unicompartmental Replacement (UKR). There is little agreement amongst knee surgeons. Both interventions are established and well documented procedures, yet little evidence exists to support their practices. Each intervention is considered standard care. There exists little evidence, however, to prove the clinical and cost effectiveness of either management option. The aim of TOPKAT will be to assess the clinical and cost effectiveness of Total Knee Replacements versus Unicompartmental Knee Replacements in patients with medial osteoarthritis. This will be examined using an appropriate patient base and long term assessments. The trial has a combined device/expertise based allocation depending on the local situation. Surgeons who are in equipoise and have sufficient experience to perform both TKR and UKR, randomisation and allocation can be based on "device" (UKR or TKR). The same surgeon will perform the operation for both arms of the study. For surgeons who hold a preference for one treatment over the other, an "expertise" based randomisation will then occur. UKR surgeons will work alongside TKR surgeons. Patients recruited to the study from these sites will be randomised to one of the treatment options and treated by the appropriate surgeon In such cases the patient is internally referred to the other surgeon's operating list. Patients will be recruited by their consultant knee surgeons in collaboration with the local research team. TOPKAT are hoping to recruit 500 patients altogether, with 250 per arm of the trial.
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