Lower-extremity venous thrombosis in patients with acute hip fractures: determination of anatomic location and time of onset with compression sonography

Patients with acute hip fractures are at increased risk for the development of lower-extremity deep venous thrombosis and its major complication, pulmonary embolism. It is furthermore recognized that the risk of clinically important pulmonary embolism depends to some degree on the anatomic location of the preexisting thrombosis. Because of the increased risk of thromboembolic disease, most patients with hip fracture are treated with one of several prophylactic regimens. The potential for effective prophylaxis may depend on the time of onset of the venous thrombosis. We used compression sonography to determine the anatomic location and time of onset of deep venous thrombosis in patients with hip fractures being treated with antithrombotic prophylaxis. Ninety-six patients had compression sonography of the injured extremity perioperatively and serially until discharge. Ninety-three also were examined with contrast venography when the sonogram suggested thrombus or at discharge if all sonograms were normal. Twenty areas of thrombus were identified in 18 patients, thereby yielding a prevalence of thrombosis of 19%. All patients were asymptomatic. Above-knee clot was diagnosed in 14 (78%) of these 18 patients. Nine (64%) of the 14 patients with significant clot had the abnormality on their first perioperative investigation (in eight of nine cases, the clot was adjacent to the fracture site), before any means of prophylaxis could have been initiated. Significant thrombosis developed in six patients later in their course (in only one case was the clot related to the fracture site), and the thrombus was an extension of below-knee clot in the minority of the patients. We conclude that although currently acceptable prophylaxis may decrease the frequency of thrombosis, it does little to prevent above-knee clot, which often antedates the initiation of therapy. Furthermore, as the clinical diagnosis of deep venous thrombosis is difficult in patients with acute hip fracture, serial compression sonograms are recommended so that patients with unsuspected clot may be treated with appropriate anticoagulation and/or caval interruption.