A Prospective Cohort Study of the Epidemiology of Symptomatic Venous Thromboembolism (VTE) after Isolated Leg Fractures Distal to the Knee without Thromboprophylaxis.

The reported incidence of deep vein thrombosis (DVT) using routine venography in patients with isolated leg fractures distal to the knee is as high as 40%. However venography is a very sensitive screening test primarily detecting asymptomatic, distal thrombi whose clinical relevance is uncertain. Therefore venography may not be the best outcome measure to assess the clinical burden of symptomatic VTE, or as an endpoint for trials of thromboprophylaxis. We report preliminary results from the first, multicenter, prospective study designed to define the incidence of symptomatic VTE in patients with such fractures. From August 2002 to April 2004, 1808 consecutive patients with fractures of the patella, fibula and foot (treated conservatively or operatively) and tibial fractures (treated non operatively) were screened for entry at 5 hospitals in Ontario, Canada. Patients were enrolled after informed consent was obtained, in person or by telephone, within 96 hours of the injury. Patients with major trauma, active cancer and previous VTE were excluded. Thromboprophylaxis was not allowed. Patients were followed prospectively for 3 months, with telephone calls at 14 days, 6 weeks and 3 months. Education regarding symptoms of DVT and pulmonary embolism (PE) was provided at study entry and patients were asked about specific symptoms at follow up. Suspected DVT and PE were investigated in a standardized manner. At the time of this writing, 826 enrolled patients have completed 3 months of follow up. The mean age was 45 years (range 16 to 93) and 59.5% of this cohort was female. Most injuries were caused by falls (75%), followed by sports injuries (16%), vehicular accidents (5%) and occupational injuries (4%). 15% of patients had other minor injuries. 99% of these fractures were unilateral and 97% were closed. Fractures of the fibula were the commonest (38%), followed by metatarsal (29%), phalanges (13%), calcaneus, talus or tarsal (10%), tibia (10%) and patella (7%). Only 11% of fractures were surgically treated. 88% of patients received a cast or splint for a mean duration of 41 ± 20 days. Four patients received anticoagulant prophylaxis (outside study protocol) for subsequent major surgery for another reason within the study period. Complete follow up was available for 97.5% of this cohort. 2.5 % of patients either withdrew consent for the follow up or could not be contacted despite numerous attempts at follow up. By 3 months, only 7 patients had sustained a symptomatic VTE (2 proximal DVT, 3 calf DVT, 2 PE) with no fatal PE - an incidence of 0.9% (95% C.I. 0.3 to 1.8%). So far, our results provide reassurance that symptomatic and fatal VTE are infrequent complications after these fractures without thromboprophylaxis, and highlight the discrepancy between clinical endpoint studies and studies using venography. They also suggest that routine thromboprophylaxis may not be warranted in these patients. Despite the large sample size, the low event rate does not allow us to define a subgroup of patients who may be at higher risk for VTE.