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Arthroscopic knee surgery and lower-leg casting are common clinical situations for which intervention to prevent deep venous thrombosis might seem reasonable. However, evidence to support thromboprophylaxis following these procedures is mixed, and the 2012 guideline from the American College of Chest Physicians does not recommend pharmacologic prophylaxis after either of them (Chest 2012; 141[2 Suppl]:e278S). Now, Dutch researchers have conducted two large trials to address this issue.
In one study, about 1500 patients who underwent knee arthroscopy (most commonly for meniscectomy) were randomized to low-molecular-weight heparin (LMWH) or no LMWH for 8 days after the procedure. During 3 months of follow-up, very few patients — five in the LMWH group and three in the control group — developed symptomatic venous thromboembolism. One patient in each group experienced major bleeding.
In the other study, about 1500 patients who had at least 1 week of lower-leg casting (most commonly for metatarsal or ankle fractures) were randomized to LMWH for the full period of immobilization or no LMWH. During 3 months of follow-up, 10 LMWH patients and 13 control patients developed symptomatic venous thromboembolism (a nonsignificant difference). No patient had major bleeding.
van Adrichem RA et al. Thromboprophylaxis after knee arthroscopy and lower-leg casting. N Engl J Med 2016 Dec 3; [e-pub]. (http://dx.doi.org/10.1056/NEJMoa1613303)
Comment
These studies indicate convincingly that routine thromboprophylaxis is not warranted after knee arthroscopy and after casting for lower-leg fractures. Although these patients were not screened for asymptomatic deep venous thrombosis, the goal is to prevent symptomatic thromboembolism — which occurred in very few treated or untreated patients. However, the authors suggest that thromboprophylaxis might be appropriate for selected high-risk patients; in population-based observational studies by this research team, patients who developed venous thrombosis after knee arthroscopy or lower-leg casting tended to have additional risk factors for thrombosis.