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Extended prophylactic treatment after hip or knee replacement reduces risk of venous thrombosis


Patients are at a substantially reduced risk of venous thrombosis after hip or knee replacement if they are given extended anti-clotting prophylactic treatment after surgery and discharge from hospital, conclude authors of a meta-analysis published in this week's issue of THE LANCET.

The optimum duration of prophylaxis against venous thromboembolism (VTE) after total hip or knee replacement is uncertain. Daniel Quinlan from King's College Hospital, London, UK, in conjunction with colleagues from Australia and Canada, identified randomised trials comparing extended-duration prophylaxis using heparin or warfarin with placebo or untreated control in patients undergoing elective total hip or knee replacement. Two reviewers independently extracted data on study design, venographic VTE (including deep vein thrombosis and pulmonary embolism) with and without symptoms, death, and bleeding outcomes.

Nine studies met the investigators' inclusion criteria (encompassing around 4000 patients), eight with low-molecular-weight heparin, and one with unfractionated heparin. Extended-duration prophylaxis for 30-42 days significantly reduced the frequency of symptomatic VTE compared with controls (1.3% compared with 3.3%). There was a greater risk reduction in patients undergoing hip replacement (1.4% compared with 4.3%), compared with knee replacement (1% compared with 1.4%). A significant reduction in venographic deep vein thrombosis without symptoms was also observed (9.6% compared with 19.6%).

The investigators conclude that among patients undergoing total hip or knee replacement, extended-duration prophylaxis significantly reduces the incidence of symptomatic VTE. The reduction in risk is equivalent to about 20 symptomatic events per 1000 patients treated.

Daniel Quinlan comments: "There has been intense debate in recent years about the optimal duration of thromboprophylaxis after hip and knee arthroplasty. Our data provide, for the first time, clear evidence that these patients benefit from extended duration thromboprophylaxis. A second important finding of our study is that there was a parallel reduction in symptomatic events and in asymptomatic events detected by screening ascending contrast venography. This suggests that venography remains a valid surrogate measure of outcome in venous thromboembolism prevention trials."


Contact: Dr Daniel J Quinlan, Department of Radiology, King's College Hospital, Denmark Hill, London SE5 9RS, UK; T) +44 (0) 20 7346 4164; F) +44 (0) 20 7346 3157; E)

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