Direct treatment comparison of DAbigatran and RIvaroxaban versus NAdroparin in the prevention of venous thromboembolism after total knee arthroplasty surgery: design of a randomised pilot study (DARINA).

Introduction: Two novel agents, dabigatran and rivaroxaban, recently gained market authorisation for prevention of venous thromboembolism (VTE) after hip and knee arthroplasty. However, safety data of the new oral anticoagulants with a long-term use of 42 days are not available for total knee arthroplasty (TKA). Furthermore, there are no clinical trials comparing dabigatran and/or rivaroxaban with nadroparin, which is used in most Dutch departments of orthopaedic surgery. Our aim is to compare the 42-day use of dabigatran and rivaroxaban versus nadroparin after TKA in a clinical explorative pilot study by assessing the incidence of major bleeding and clinically relevant non-major bleeding using a standardised model of bleeding definitions. Methods and analysis: A randomised open-label pilot study was conducted. Patients >= 18 years and weighing more than 40 kg who were scheduled for a primary elective TKA were included. Patients were randomly assigned to three groups. Patients took either a daily oral dose of dabigatran etexilate 220 mg (n=50), 10 mg of oral rivaroxaban (n=50) or subcutaneous nadroparin 0.3 ml (n=50) for 42 days. The primary safety outcome measure was the incidence of bleeding events. Major bleeding events and clinically relevant non-major bleeding events were defined according to accepted guidelines. The secondary measures of this study were the occurrence of VTE, time until the bleeding event, compliance, duration of hospital stay, rehospitalisation, outpatient clinic visits and interventions following complications. Additionally, coagulation monitoring, knee flexion range of motion and Knee injury and Osteoarthritis Outcome Score were evaluated. Dissemination: The results of this trial provided insight into the validity of design for an adequately powered multicentre study investigating the safety of the new oral anticoagulants compared with nadroparin, an anticoagulant applied for prevention of VTE after knee arthroplasty in the Dutch situation.