The detection of deep venous thrombosis by impedance plethysmography in hip surgery patients.

Cuff impedance plethysmography has been performed on 120 patients undergoing total hip replacement surgery, all of whom have had venography. The low incidence of thrombosis (17.5%) precluded any accurate data on sensitivity, but specificity was 85%, positive accuracy 48%, negative accuracy 92% and validity 82%. There was a high false positive rate in the first postoperative week (40% of 25 negative venograms). The technique is of value for the exclusion of thrombi in such patients after the eighth postoperative day. Venography will still be required for the positive identification of thrombi in any research protocol.