This mono-centric, open-label study is undertaken to validate the effects of Dabigatran on coagulation parameters in plasma samples of 70 patients after hip or knee replacement surgery treated with Dabigatran 150-220 mg/d. Plasma samples are obtained by blood collection before, after 2 hours and after 12-14 hours after Dabigatran dosing in steady state (on 3rd - 5th day).