The clinical and cost-effectiveness of elective primary total knee replacement with PAtellar Resurfacing compared to selective patellar resurfacing. A pragmatic multicentre randomised controlled Trial with blinding (PART)
Every year, over 100,000 people in the UK have a total knee replacement, and surgeons must decide whether to replace the kneecap’s underside with a plastic prosthesis or leave the natural bone in place. This trial addresses a gap left by NICE, which recommends always resurfacing the patella but found insufficient evidence on a middle-ground strategy: selective resurfacing, where the decision is made during surgery based on the condition of the patient’s own kneecap and symptoms. The always-resurface approach costs more upfront—longer theatre time, higher implant costs, and added risk of early complications—but can reduce the chance of ongoing pain that later requires a second operation. Selective resurfacing could offer the best of both, but no robust trial has compared them directly. If the research shows selective resurfacing is as effective as always resurfacing, it could change surgical practice across the NHS. Patients would avoid unnecessary implants and extra surgical risk, while the health service could save on implant costs and theatre time. If always resurfacing proves superior, the trial will confirm current NICE guidance with stronger evidence. Either way, the 530-patient randomised trial will give surgeons and commissioners a clear, cost-effectiveness answer.
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BACKGROUND: Total knee replacement (TKR) is commonly used for treating severe arthritis, with over 100,000 performed annually in the UK. During TKR, surgeons can resurface the patella (replace the under surface of the kneecap with a plastic prosthesis) or leave the native patella to articulate with the femoral implant. Resurfacing the patella is initially more expensive (longer theatre time, higher implant cost, risk of additional post-operative complications), but in the long-term it can reduce the risk of on-going pain which can result in further surgery to resurface the patella. NICE recommends always resurfacing the patella rather than never doing so. NICE did not find sufficient evidence on selective resurfacing (intraoperative decision based on the state of the patellar surface and the patients’ symptoms) to make a recommendation on that strategy, but did recommend specific research was conducted on this question. If effective, selective resurfacing could result in optimal individualised patient care. AIM: To evaluate the clinical and cost-effectiveness of elective primary TKR with always patellar resurfacing compared to selective patellar resurfacing. DESIGN: Patient and assessor-blinded multicentre, pragmatic two-group randomised superiority trial. SETTING: NHS hospitals in England. POPULATION: Adults having primary TKR for osteoarthritis. EXCLUSION CRITERIA: Patellar thickness insufficient for resurfacing (checked intraoperatively). Primary TKR with the need for constrained implants. INTERVENTIONS: Randomisation to always patellar resurfacing, or selective patellar resurfacing. OUTCOME MEASURES: Primary: Oxford Knee Score (OKS) at 1 year, a validated patient reported outcome measure (PROM). Secondary: PROMs at 3 months, 6 months and 1 year, including the Knee Injury & Osteoarthritis Outcome Score, OKS, and EQ-5D-5L; postoperative complications, resource use and costs within 1 year. SAMPLE SIZE: The OKS minimally clinically important difference is 4 points (standard deviation 10 points). A study of 530 patients (265/group) will provide 90% power with 5% statistical significance (2-sided) to detect this effect size allowing for 10% loss to follow-up, up to 40% resurfacing in the selective group, 5% not resurfacing in the always group and an 82% efficiency gain from repeated OKS at baseline, 3 months, 6 months and 1 year. ANALYSIS: Primary statistical and economic analyses will be intention-to-treat and follow a pre-specified analysis plan. Results will be reported following CONSORT and CHEERS guidelines. We will estimate effectiveness and cost-effectiveness beyond the trial using modeling. PROJECT TIMETABLE & RECRUITMENT RATE: Study duration 48 months: 6m set up, 24m recruitment (8m internal pilot, 16m main trial), 12m for patient follow-up, 6m analysis and report. Longer-term outcomes will be assessed with routinely collected data (subject to further funding). The study aims to recruit a mean 2.8 patients/centre/month. ANTICIPATED IMPACT & DISSEMINATION: Results will be disseminated to researchers, healthcare professionals, the public, and stakeholders (commissioners, regulators and NICE) through open access peer-review publications, presentations, and other media. The trial will demonstrate if selective or always patellar resurfacing is the most clinically and cost-effective approach. This research has the potential to improve outcomes and prevent complications for people having primary TKR.
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