Title: Total or Partial Knee Arthroplasty Trial (TOPKAT)
Funder: Department of Health and Social Care

Abstract: 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.

Lay abstract: Osteoarthritis of the knee affects a large proportion of the population and this is set to increase over time. Quite often the arthritis is limited to one area of the joint, particularly the inside of the joint (closest to midline of the body). Patients with this disease can either have a partial knee replacement (unicompartmental replacement) or a total knee replacement. The partial knee or unicompartmental replacement (UKR), as its name suggests, involves the removal and replacement of only the diseased part of the joint. Total knee replacement (TKR) involves removal and replacement of the entire knee joint. Total knee replacement is easier to do and considered more reliable (lower failure/revision rate) but it involves cutting away healthy parts of the joint. Partial or UKR is more difficult to do but retains healthy tissue and usually achieves better functional results but can have an increased failure/revision rate. There are also significant cost advantages for the healthcare system for partial knee replacements. Unfortunately we do not know which type of replacement, overall, is best for these particular patients. There is no good direct evidence. Hence, we intend to perform a large scale, well designed NHS clinical trial to directly compare the two types. A clinical trial involves the recruitment and measurement of patients over time, usually after some type of medical intervention. In this case the intervention is a knee replacement. The research will be carried out at the local hospital or institution where the patient would normally have their knee replacement. Measurements and questions will be asked in clinic. The measurements taken to assess which type of knee replacement is better will be predominantly patient based. This means that the measurements directly assess how the patient, rather than the surgeon, feels about the outcome after their operation. A specific ethical issue exists with this type of study. Surgeons can often have a preference of one type of knee replacement over another, either because they believe it gives better results or because they perform one operation better then the other. Clearly this would bias the trial and therefore it is important that only the surgeons who are impartial, and who can do both operations well, can recruit patients. In this situation, when allocating patients to groups the allocation is termed a "device" based allocation. However, as there may not be enough surgeons who remain impartial (known as in "equipoise") another form of allocation can also take place. In this case the surgeon with a preference must work alongside another surgeon who prefers the other type of knee replacement. Following randomisation (allocation to one of the two groups) the patient would then have their operation carried out by the surgeon with the appropriate expertise for their allocated operation (either UKR or TKR). Such a study is known as an "expertise" based allocation and will require each hospital unit to have at least one surgeon who would normally implant a UKR for medial arthritis and one surgeon who would normally implant a TKR for medial knee arthritis. The team assembled for this study is a first class, high profile team of academics, clinicians and researchers. Such a trial requires the right blend of multidisciplinary skills - clinicians, experienced trialists, statisticians, health economists, trial managers and information technologists, all of which are included. The trial will be co-ordinated from Oxford University, which has a good track record in orthopaedic research, and with expert guidance and mentoring from senior researchers in the trials unit at Aberdeen. The Oxford and Aberdeen groups have previously and successfully collaborated on several big clinical trials. As the trial involves many centres (to make it generalisable across the country) all the data will be collected using a confidential and secure internet system. The trial will also involve leading orthopaedic knee surgeons from all round the UK and draw on the expertise of a variety of collaborators including pain experts, epidemiologists and orthopaedic engineers.

Research activity codes: 6.4 SURGERY
Health categories: MUSCULOSKELETAL