Clinical Outcomes in Patients Receiving Venous Thromboembolism (VTE) Prophylaxis after Orthopedic Surgery (OS). A Systematic Review and Meta-Analysis of Proportions.

Major VTE is the most frequent complication of OS. Current recommendations are to administer prophylaxis with an anticoagulant agent for at least 7–10 days. Numerous studies have evaluated different agents for this purpose. Although the most recent studies are usually methodologically sound, several studies have been hampered by inappropriate designs and insufficient sample sizes. In order to help with the design of future trials we conducted a systematic review of randomized trials evaluating short-term (< 15 days) administration of anticoagulants for VTE prophylaxis in OS and performed a MA of simple proportions to estimate the overall incidence of major VTE (proximal VTE, pulmonary embolism (PE), or death from PE), total VTE (proximal and distal VTE, PE or death from PE), and major bleeding episodes (as defined by the authors and defined using a definition similar to the one proposed by the International Society on Thrombosis and Haemostasis-ISTH). We included randomized trials comparing different drugs for VTE prophylaxis in OS (hip and knee arthroplasty and hip fracture surgery) using systematic evaluation of VTE (ultrasound or venography, pulmonary angiography, tomographic angiography, or ventilation perfusion lung scan). Heterogeneity of proportions was evaluated using a chi ² test and pooled estimates of proportions were obtained using a fixed or a random effects model as appropriate. In the latter the weights were estimated as proposed by Laird and Mosteller. We retrieved 55 studies (135 research arms) which enrolled 42,131 patients. The percentage and variance of major and total VTE and major bleeding are shown in table 1. The total number of events and the number of evaluable patients are shown in table 2. We found differences in the percentage of clinical outcomes associated with the use of different agents for VTE prophylaxis after OS, however, because of the analytical strategy used no estimation of odds or risk reduction can be derived from this data. We believe that these estimates will be of help for the design of future studies.