VTE Prophylaxis After Knee Arthroscopy and Leg Casting
What is the incidence of symptomatic venous thromboembolism (VTE) after knee arthroscopy or lower leg casting in patients who do and do not receive prophylactic anticoagulation?
The authors conducted two parallel, pragmatic, multicenter, randomized, controlled, open-label trials with blinded outcome adjudication. The first trial (POT-KAST) included patients undergoing knee arthroscopy. The second trial (POT-CAST) included patients treated with lower leg casting. Patients were randomly assigned to prophylactic dose low-molecular-weight heparin (LMWH) or no anticoagulation therapy. The two primary outcomes were symptomatic VTE and major bleeding within 3 months.
In the POT-KAST (knee arthroscopy) trial, 1,543 patients underwent randomization, and VTE occurred in 5/731 (0.7%) of the treatment group and 3/720 (0.4%) in the control group (relative risk [RR], 1.6; 95% confidence interval [CI], 0.4-6.8). Major bleeding occurred in one patient (0.1%) in each of the treatment and control groups. In POT-CAST (leg casting), 1,519 patients were randomized, and VTE occurred in 10/719 (1.4%) of the treatment group and 13/716 (1.8%) of the control group (RR, 0.8; 95% CI, 0.3-1.7). No major bleeding occurred in either group.
The authors concluded that VTE prophylaxis with LMWH did not prevent symptomatic VTE in either knee arthroscopy or lower leg casting populations.
While the use of LMWH or other antithrombotic agents are well established to prevent deep-vein thrombosis among patients undergoing major orthopedic surgeries (e.g., hip and knee arthroplasty), this study suggests that VTE prophylaxis may not be necessary for more minor surgeries (specifically knee arthroscopy) or lower leg casting. In fact, the results of these two studies contradict meta-analyses of smaller studies in each population. Importantly, this study established symptomatic VTE (not a combination of symptomatic and asymptomatic VTE) as the primary outcome, which was relatively rare in both treatment groups of both trials. This is somewhat different from prior trials where screening ultrasound was performed routinely and symptoms were assessed afterwards. Clinicians should discuss the risks and benefits of VTE prophylaxis with patients undergoing knee arthroscopy or lower leg casting, and can be re-assured if patients elect to forego VTE prophylaxis.
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