We performed a prospective randomised controlled trial of a new mechanical method of prophylaxis for venous thrombo-embolism in 60 patients undergoing knee replacement surgery. The method uses the A-V Impulse System to produce cyclical compression of the venous reservoir of the foot. The overall incidence of deep-vein thrombosis was 68.7% in patients receiving no prophylaxis and 50% in those using the device. The difference was not significant. There was, however, a reduction of the extent of thrombosis in the treated group. There were 13 major calf-vein thrombi and six proximal-vein thrombi in the control group compared with only five major calf-vein thrombi in the treated group. This difference was significant (p = 0.014). No patient developed clinical features of a pulmonary embolism.

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.

A prospective study involving 500 consecutive patients undergoing hip replacement was performed to find out whether a combination of heparin and dihydroergotamine was effective in preventing postoperative fatal and non-fatal emboli. Deep-vein thrombosis was demonstrated in 131 cases (26.2%), in 99 of whom thrombi were confined to the ipsilateral (operated) limb and in 13 to the contralateral limb; 19 patients developed bilateral thrombi. Nine patients (1.8%) died during the first four weeks after operation, before they were discharged from hospital; in one, major emboli were demonstrated in the right pulmonary artery. Three of the 500 patients developed non-fatal pulmonary emboli. Excessive bleeding occurred in 21 (4.2%) and in 19 of these prophylaxis was discontinued. Wound haematomas developed in 25 patients (5.0%); only six required evacuation but in none of these six did deep infection occur while in hospital; in three patients, however, the wound haematoma prolonged the stay in hospital. Thus the combination of heparin and dihydroergotamine proved an effective prophylaxis against pulmonary embolism in patients undergoing total hip replacement. The risk of bleeding complications is wholly acceptable when balanced against the advantages of the therapy.