Prophylactic LMWH not associated with prevention of VTE after arthroscopy or casting: The POT-KAST and POT-CAST trials

1. Prophylactic low-molecular-weight heparin (LMWH) for 8 days post knee arthroscopy demonstrated no change in the incidence of venous thromboembolism (VTE) or major bleeding events compared to placebo.

2. Prophylactic LMWH during the full period of immobilization due to casting of the lower extremity demonstrated no change in the incidence of VTE or major bleeding events compared to placebo.

Evidence Rating Level: 1 (Excellent)

Study Rundown: Arthroscopic knee surgery is the most commonly performed orthopedic procedure worldwide. While it has been established that knee arthroscopy, and also casting of the lower leg, increase patients’ risk for VTE, it is uncertain whether pharmacologic thromboprophylaxis after these procedures is an effective means of risk reduction. The Prevention of Thrombosis after Knee Arthroscopy (POT-KAST) and the Prevention of Thrombosis after Lower Leg Plaster Cast (POT-CAST) trials were performed to compare LMHW and placebo on the basis of their effectiveness in the prevention of symptomatic VTE.

In both the POT-KAST and POT-CAST trials, no significant difference was observed in the frequency of symptomatic VTE between the groups. In both trials, no significant difference was observed in the frequency of major bleeding events between the groups. These results are strengthened by the multi-center, placebo-controlled design of the studies; however, the non-blinded group assignments cannot be excluded as a limitation.

Click to read the study, published today in NEJM

Relevant Reading: Incidence and risk factor analysis of symptomatic venous thromboembolism after knee arthroscopy

In-Depth [randomized controlled trial]: This study reports the findings of two parallel, multicenter, open-label, randomized, placebo-controlled trials. The primary outcomes for this study included the overall incidences of symptomatic VTEs and major bleeding within 3 months after the procedure. In the POT-KAST trial (n = 1451), VTE occurred in 5 of the 731 patients (0.7%) of patients who received LMHW and in 3 of the 720 patients (0.4%) who received placebo (RR 1.6, 95%CI 0.4 to 6.8). Major bleeding occurred in 1 of 731 patients (0.1%) of patients who received LMWH and in 1 of 720 (0.1%) patients who received placebo. In the POT-CAST trial (n = 1435), VTE occurred in 10 of the 719 (1.4%) of patients who received LMWH and in 13 of the 716 patients (1.8%) who received placebo (RR 0.8, 95%CI 0.3 to 1.7). No major bleeding events occurred in either group and the most common adverse event was infection.

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