Francis CW, Pellegrini VD Jr, Marder VJ, Totterman S,
Harris CM, Gabriel KR, Azodo MV, Leibert KM.
Comparison of warfrain and external pneumatic compression in prevention of venous
thrombosis after total hip replacement.
JAMA 1992 Jun 3;267(21):2911-5

Department of Medicine, University of Rochester, School of Medicine and
Dentistry, NY 14642.

OBJECTIVE--To compare the effectiveness and safety of warfarin and external
pneumatic compression (EPC) in prevention of venous thrombosis after total hip
replacement. DESIGN--Prospective, randomized trial in consecutive patients, with
blinded assessment of the primary end point. SETTING--University medical center
and large community hospital. PATIENTS--Patients over age 18 years scheduled for
elective primary total hip replacement were eligible. Of 254 patients
interviewed, 232 were randomized, 220 patients had surgery and received
prophylaxis, and 201 had venography. INTERVENTIONS--Patients were randomly
assigned to prophylaxis with a device providing bilateral sequential EPC to both
the calf and thigh or to receive warfarin in a low-intensity regimen beginning 10
to 14 days preoperatively. Prophylaxis was continued until venography. MAIN
OUTCOME MEASURES--Venous thrombosis was diagnosed by venography between
postoperative days 6 and 8. Bleeding was assessed by surgical blood loss,
transfusion requirements, changes in hematocrit, and clinically identified
bleeding complications. RESULTS--The total incidence of venous thrombosis was
virtually the same in the warfarin and EPC groups (31% vs 27%), but the
distribution of thrombi was different. Proximal thrombosis occurred in 12% of
patients in the EPC group compared with only 3% in the warfarin group (P = .012,
95% confidence interval for difference, 2% to 18%). In contrast, calf vein
thrombosis was more frequent in the warfarin group (21%) than in the EPC group
(12%) (P = .021, 95% confidence interval for difference, 0% to 18%). Most
proximal thrombi in EPC-treated patients were located within 15 cm of the femoral
head and were not continuous with thrombi in deep calf veins. The high incidence
of proximal thrombosis in the EPC group resulted in termination of the study by
the safety monitoring committee. Blood loss and bleeding complications were
similar in the two groups. CONCLUSION--Warfarin therapy is significantly more
effective than EPC in preventing serious proximal vein thrombosis after total hip
replacement. The greater effectiveness of warfarin therapy in preventing proximal
vein thrombi and of EPC in preventing thrombosis in the calf suggests that there
are differences in the pathogenesis of thrombosis in these two locations.