Deep vein thrombosis after elective knee surgery. An incidence study in 312 patients.

The incidence of venous thromboembolism after elective knee surgery has previously been studied almost exclusively in patients receiving total knee replacements, in whom the risk of a deep vein thrombosis is approximately 60%. We report the results of ipsilateral ascending venography in 312 patients undergoing a wide variety of elective knee operations under tourniquet ischaemia, none of whom received any specific prophylaxis against thromboembolism. Total knee replacement was confirmed to carry a high risk with ipsilateral deep vein thrombosis in 56.4% and symptomatic pulmonary embolism in 1.9%. By contrast, arthroscopy was associated with a low incidence of venous thrombosis (4.2%). Meniscectomy, arthrotomy, patellectomy, synovectomy and arthrodesis were all high-risk procedures, particularly in patients over 40 years of age, and were associated with deep vein thrombosis rates of 25% to 67%. On the basis of these findings, we advise prophylaxis against venous thromboembolism in all patients over 40 years of age undergoing elective knee surgery other than arthroscopy.