51 patients undergoing elective total knee and hip arthroplasty were randomized to receive thromboprophylaxis with either subcutaneous injection of fondaparinux (2.5 mg) or aspirin (325 mg) plus compression stockings. The purpose of this study was to determine whether a correlation exists between changes in thrombogenicity due to surgical trauma, and transfusion rates. Seven patients received a blood transfusion, and these patients had lower thrombin-induced platelet fibrin clot strength compared to patients who did not, at all time points. However, significance was only achieved prior to and immediately following surgery, suggesting a potential correlation. All other coagulation factors were not significant.