Purpose: Among patients with isolated below-knee fractures, venography studies detect deep vein thrombosis (DVT) in 20 – 40%. The clinical relevance of these thrombi is unknown. We conducted the first randomized, double-blind, multicentre study designed to assess the effectiveness and safety of low molecular weight heparin compared to placebo in preventing CIVTE in patients with isolated fractures of the distal leg.

Method: Consecutive patients with fractures of the tibia, fibula or ankle requiring surgery were randomized to dalteparin 5000 U or placebo once daily SC within 72 hours of fracture for 14 + 2 days. Patients were screened using proximal duplex ultrasound at day 14, and followed up at 6 wks and 3 mos. Clinically suspected VTE was investigated using standardized algorithms with central, blinded adjudication.

Results: From August 2002 to October 2006, 134 patients were randomized to dalteparin and 131 to placebo. 98% of patients completed 3 mo follow-up. Overall, 5 patients had CIVTE (2 asymptomatic DVT, 2 symptomatic DVT, 1 nonfatal PE); 2 (1.5%) in the dalteparin arm and 3 (2.3%) on placebo (p=0.68). There were no major bleeds.

Conclusion: The overall incidence of CIVTE after surgically-repaired, isolated tibia, fibula and ankle fractures was so low (1.9%; 95% CI 0.7 to 4.7%), with no observed differences between dalteparin and placebo either for CIVTE or safety, that recruitment was stopped early. This study also demonstrates the large discrepancy between trials that utilize venographic and CIVTE outcomes.