Venous thromboembolism (VTE)—that is, deep venous thrombosis (DVT) and pulmonary embolism (PE)—are common complications after major hip or knee surgery. Without thromboprophylaxis, the incidence of DVT in patients undergoing major orthopaedic surgery is more than 50%, and fatal PE is reported to occur in 1–6% of these patients.1 These data are based on investigations in which predominantly osteoarthritis (OA) patients were studied. Only a few (small) studies were performed in rheumatoid arthritis (RA) patients: Abernethy reports an incidence of DVT of more than 70% and overall incidence of PE of approximately 2% in RA patients who have undergone a knee arthroplasty,2 and Kelly reports, in his review,3 an incidence of fatal PE of approximately 1% in RA patients undergoing total hip replacement and not receiving thromboprophylaxis (table 1). The risk of developing DVT seems to be similar for RA patients undergoing total hip replacement and those undergoing knee replacement surgery.4

Data are conflicting regarding the risk for developing VTE for RA patients in comparison with OA patients undergoing major orthopaedic surgery. Similar incidences of VTE have been reported for OA patients undergoing major orthopaedic surgery,5 ,6 whereas one large retrospective study indicated a possibly lower rate of thromboembolic complications in RA patients (table 1).7 In this investigation, inhospital morbidity and mortality of 721 RA patients and 8859 OA patients, who underwent an elective hip replacement operation, were analysed retrospectively. The incidence of thromboembolic events was 0.3% in the RA group versus 1.2% in the OA group (p = 0.07). At first sight, these very low incidences of VTE are remarkable, but they are probably related to a very short observation period and underdiagnosing, by only observing clinical VTE. Hence, the incidence of …