[Thrombosis prevention in outpatients with lower limb injuries]

The antithrombotic effect of a low molecular weight heparin was examined in a prospective randomized trial of 204 outpatients (121 men, 83 women, mean age 34.7 [16-76] years) who required immobilization with a plaster cast because of injury to the lower limb. Subjects in group I (n = 99) received a daily subcutaneous injection (36 mg) of heparin fragment calcium throughout their period in plaster (mean of 15.6 [7-66] days), while group II subjects (n = 105, mean period in plaster 15.7 [7-41] days) acted as untreated controls. Thrombosis was diagnosed by compression sonography, and positive findings were confirmed by phlebography. Thrombosis occurred in 24 patients altogether, 6 in group I (6.1%) and 18 in group II (17.1%) (P less than 0.05). While patients with thromboses had a mean of 1.96 risk factors overall, those in group I had a mean of 2.6 risk factors. Patients without thrombosis had a mean of 1.24 risk factors. The rate of thrombosis was higher in patients with fractures (4 out of 27 in group I; 10 out of 35 in group II) than in those with ligament and soft-tissue injuries (2 out of 72 in group I; 8 out of 70 in group II). The severity of trauma is apparently an important thrombogenic factor.--General thrombo-prophylaxis seems advisable for surgical outpatients requiring immobilisation treatment with a plaster cast.