Prevention of Venous Thrombosis after Total Hip Replacement

To the Editor: The study by Leyvraz et al. in the October 20 issue suggests that low-dose heparin adjusted according to activated partial thromboplastin time is more effective than the traditional fixed dose in prevention of deep-vein thrombosis after total hip replacement.¹ Although this approach appears interesting, there are several flaws in the design and analysis of the study that should be pointed out. First of all, the control group was treated with 3500 IU of subcutaneous heparin every eight hours, which represents an unusual and probably substandard antithrombotic prophylaxis, since even a dosage of 5000 IU every eight hours.