A meta-analysis of methods to prevent venous thromboembolism following total hip replacement

While several methods of prophylaxis have been shown to reduce the risk of venous thromboembolism following total hip replacement, the safest and most effective agent is unclear. To clarify this issue, we performed a meta-analysis of the randomized trials of methods used to prevent venous thromboembolism following total hip replacement.

English-language human studies articles from 1966 through 1993 were obtained from a MEDLINE database search with indexing terms including thromboembolism, hip replacement or hip prosthesis, and randomized controlled trials. Additional references were obtained from study bibliographies.

The following criteria were used to select studies for inclusion: study design--randomized clinical trial; study population--patients undergoing elective total hip replacement; interventions--aspirin, warfarin, dextran, heparin, low-molecular-weight heparin, compression stockings; and outcomes--venous thromboembolism, major hemorrhage.

Methodological and descriptive data from each study were abstracted by one author who was blinded to quantitative outcomes data.

Ninety-one treatment groups and 25 control groups were identified from 56 trials. Four treatment groups were excluded because of rarely used combinations. Trial populations were clinically homogeneous. When compared with the control arm, all treatments except aspirin reduced the risk of all deep venous thromboses (risk differences range, 0.18 to 0.31; all P values < .05). All treatments except aspirin reduced the risk of proximal venous thrombosis (risk differences range, 0.09 to 0.18; all P values < .05). Only low-molecular-weight heparin and stockings reduced the risk of pulmonary embolism, both with risk differences equal to 0.02. The crude risks of clinically important bleeding as defined by the individual trials were 0% for stockings, 0.3% for controls, and 1.8% for low-molecular-weight heparin.

The results suggest that low-molecular-weight heparin and compression stockings have the greatest relative efficacy in preventing venous thromboembolism following total hip replacement. Low-molecular-weight heparin may be more effective, though at a small risk of clinically important bleeding.