In a prospective, randomized trial, we compared the efficacy of a
combination of antithrombin III and heparin with that of dextran 40 as
prophylaxis against venous thrombosis after total knee arthroplasty.
Ascending venography identified thrombosis in about one-third of the
patients who received the combination of antithrombin III and heparin,
compared with about four-fifths of those who received dextran (p less than
0.001). In both groups, the patients who had venous thrombosis had a
significantly lower concentration of antithrombin III postoperatively than
those who did not have thrombosis. Venous thrombosis occurred in all
patients in whom the concentration of antithrombin III was less than 65 per
cent postoperatively. These findings demonstrated that, after total knee
replacement, the combination of antithrombin III and heparin effectively
reduces the incidence of postoperative venous thrombosis and is
significantly better than dextran. Furthermore, the findings suggested a
relationship between postoperative deficiency of antithrombin III and the
occurrence of thrombotic complications.