The Knee Arthroplasty versus Joint Distraction Study for Osteoarthritis (KARDS): lessons learnt from an internal pilot trial.

Background: Patients with symptoms of pain and restricted function related to knee osteoarthritis are typically offered a knee replacement. However, a proportion remain dissatisfied with their outcomes, and the failure risk is disproportionately higher in the young. Knee joint distraction may be an intervention to postpone the time to knee replacement in this patient population. Objective and main outcome measure: The primary objective of the Knee Arthroplasty versus Joint Distraction Study for Osteoarthritis (KARDS) was to evaluate the effectiveness of knee joint distraction compared to knee replacement based on patient-reported pain 12 months post surgery using the Knee Injury and Osteoarthritis Outcomes Score pain score as the primary outcome. Design and methods: KARDS was an open-label, two-arm individually randomised controlled non-inferiority trial with an embedded 12-month internal pilot phase and process evaluation to evaluate recruitment feasibility. A hybrid expertise design was used to account for surgeon expertise and potential lack of individual equipoise. The trial was closed to recruitment early following cessation of elective orthopaedic surgery secondary to COVID-19 pandemic. Descriptive statistics are reported. Setting: United Kingdom National Health Service Trusts. Participants: Adult patients aged < 65 years with symptoms severe enough to warrant knee replacement, in the opinion of the treating clinician. Interventions: Participants were randomised to receive either knee joint distraction (static distraction of 5 mm, using external fixator for 6 weeks) or knee replacement. Results: Twenty-four participants were randomised from a single centre between March 2021 and October 2022 with minimum 3-month safety follow-up post surgery. Eleven participants were randomised to knee joint distraction and 13 to knee replacement. Seventeen patients were male (71%), median age 60 (47-65) years. One patient withdrew due to being medically unfit for surgery and two received a different treatment than which they were randomised (one crossover from each arm). The median Knee Injury and Osteoarthritis Outcomes Score pain score in the knee joint distraction group improved from 38.9 (22-50) at baseline to 55.6 (0-100) at 12 months, corresponding scores in the knee replacement improved from 30.6 (6-36) to 75.0 (50-100). Adverse events were more common with knee joint distraction, pin site infection being the commonest complications ( Conclusion: Reduced research capacity and the suspension of elective surgery following the COVID-19 pandemic caused significant recruitment barriers. Despite early termination, KARDS demonstrated that patients were willing to be recruited to a trial investigating a novel treatment for knee osteoarthritis and the trial was feasible and implementable. The limited results indicated that the technique is safe with no safety concerns. Clinical and cost-effectiveness of knee joint distraction remains uncertain. The embedded KARDS process evaluation has provided helpful insights. Limitations: Reduced research capacity at sites and suspension of elective surgery services within the United Kingdom following COVID-19 caused significant recruitment barriers to KARDS. All the recruited patients in both arms of the study were White. Future work: As a commissioned piece of research with delivery significantly impacted by the National Health Service environment post-COVID and the impact on National Health Service surgical services, the research question remains highly relevant. Any future research in this field can be helped by the pilot data published here along with the lessons learnt. Funding: This synopsis presents independent research funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme as award number 17/122/06.