The Journal of Arthroplasty Vol. 12 No. 6 1997 Incidence of Fatal Pulmonary Embolism After 1,390 Knee Arthroplasties Without Routine Prophylactic Anticoagulation, Except in High-risk Cases S. Ansari, MS (Surg), MS (Orth), FRCS, David Warwick, MD, FRCS, C. E. Ackroyd, MA, FRCS, and J. H. Newman, MA, FRCS Abstract: A consecutive series of 1,390 primary total knee arthroplasty (TKA) procedures (1,201 patients, 1,600 arthroplasties) performed between January 1980 and July 1994 were reviewed to establish the incidence of death from pulmonary embolism (PE). Nine hundred twenty-three bi- or tricompartment TKAs and 467 unicompartment TKAs were performed as one-stage procedures. Chemical throm- boprophylaxis was used only in high-risk cases in which there was a history of pre- vious thromboembolism or obesity. There were no deaths from PE after unicom- partment arthroplasty procedures. Autopsy confirmed PE as the cause of death in 2 patients following bi- and tricompartment TKAs (0.22%; 95% confidence interval [CI], 0.03-0.8%). The incidence was higher for one-stage bilateral TKA as 1 of the autopsy-confirmed deaths occurred in this group 0.7% (95% CI, 0.02-3.78%). Two other deaths were certified without postmortem examination (pneumonia and myocardial infarction in each case). As PE could not be ruled out as the cause of death in the latter 2 cases, these were considered as possible PE deaths to provide the maximum possible death rate that could result. Thus, the maximum possible incidence of fatal PE after TKA without routine use of chemical anticoagulation was 0.4% (95% CI, 0.1-1.I%). It is concluded that the risk of fatal PE after unilat- eral TKA and unicompartment knee arthroplasty is low. The risk of clinical, nonfa- tal thromboembolic events, which might themselves warrant prophylaxis, was not quantified in this article. Key words: total knee arthroplasty, pulmonary embolism, thromboprophylaxis. The risk of fatal pulmonary embolism (PE) after knee arthroplasty has not been well defined. The prevalence of venographic deep vein thrombosis (DVT) after total knee arthroplasty (TKA) is 25-84% [1-4], whereas that of scintigraphic PE is From the University of Bristol, Bristol Royal Infirmary, and the Avon Orthopaedic Centre, Bristol, United Kingdom. Reprint requests: Dr. S. Ansari, % R. W. Jackson, MD, Baylor University Medical Center, George Truett James Orth Institute, 3500 Gaston Avenue, Dallas, TX 75246. © 1997 Churchill Livingstone Inc. 7-11% [4,5]. Although these figures from radio- graphic screening studies may suggest that the risk of fatal PE is also high, this may not be so. Most thrombi after TKA are confined to the calf [4,5]; such thrombi probably have a low risk of embotiza- tion [6,7], although this is controversial [8,9]. The use of thromboprophylaxis carries side- effect and cost considerations. Most randomized clinical trials of thromboprophylactic measures use the venographic prevalence of DVT as an outcome measure, with the underlying assumption that any reduction is extrapolated to a reduced fatal PE rate; 599