SummaryThe effect of subcutaneous low-dose heparin on postoperative deep-vein thrombosis (D. V. T.) (diagnosed by the 125I-labelled fibrinogen test) has been investigated in a trial of 143 patients undergoing the operation of total hip replacement. Two randomized studies were carried out: in one the scanning for D.V.T. was carried out daily for 7 days post operatively and in the other for 15 days. In both, the incidence of D.V.T. was significantly lower in the heparin-treated patients (P<0.005). Bilateral D.V.T. was also prevented (P<0.05), through the extension of D.V.T. to the distal veins of the thigh was not significantly reduced. Heparin treatment was, however, followed by a higher incidence of severe postoperative bleeding (P< 0.02) and wound haematoma formation (P< 0.005), and the postoperative haemoglobin was significantly lower than in the control group (P<0.005). A higher number of transfused blood units was also needed by the heparin treated patients (P<0.001).

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The efficacy of low-dose heparin in patients undergoing hip surgery is not established. 95 patients over the age of 40 undergoing an elective operation of hip-replacement arthroplasty have been randomly allocated to two groups on the basis of numbered sealed envelopes. 45 patients received 5000 units of subcutaneous calcium heparin preoperatively and 8-hourly after this until they were fully mobile (days of treatment: mean 14.1, SD ±5.0), 50 patients received no treatment and acted as controls. The two groups were comparable in respect to age, weight, blood-group, previous disease, findings on admission, type of operation and other drugs used. The 125I-fibrinogen-uptake test was used to diagnose DVT by injecting in all patients 100 μCi postoperatively on the day of operation and scanning the legs for seven days. The frequency of DVT was 42% (21/50) in the control group and 20% (9/45) in the treated group. The difference is statistically significant (P < 0.05) using a χ2 test with Yates’ correction. Since Hampson et al. (Lancet ii, 795, 1974) have recently suggested that low-dose heparin has no significant effect on the frequency of DVT after total-hip replacement arthroplasty but appears to delay its onset, a new trial is presently being carried out in which 100 μCi of 125I fibrinogen are injected twice and the legs scanned for 14 days.