Prophylactic Anticoagulation for Lower Limb Immobilization

Quick Takes

  • Patients with lower limb trauma and immobilization are at increased risk of venous thromboembolism (VTE).
  • The TRiP(cast) score can be used to identify patients at low risk of VTE who can safely avoid anticoagulation thromboprophylaxis.
  • Future studies are needed to identify which patients with lower limb immobilization are at sufficiently high risk to warrant anticoagulation thromboprophylaxis.

Study Questions:

What is the safety of withholding anticoagulation for patients with lower limb trauma at low risk for venous thromboembolism (VTE), as defined by the TRiP(cast) score?


The authors performed a stepped-wedge, multicenter, cluster-randomized trial with blinded outcome assessment in 15 emergency departments in France and Belgium. Following a randomized starting order, sites implemented use of the Thrombosis Risk Prediction for Patients With Cast Immobilisation-TRiP(cast)-score [TRiP(cast)], to identify patients at low risk of VTE due to lower extremity trauma and casting in whom prophylactic anticoagulation is not necessary in contrast to the control practice of anticoagulation at the discretion of the treating physician. The primary outcome was the 3-month cumulative rate of symptomatic VTE for patients at low risk, defined as a TRiP(cast) score <7. The prespecified safety rate was <1% with an upper 95% confidence interval (CI) of <2%. Both symptomatic VTE and bleeding outcomes (major plus clinically relevant nonmajor) were assessed at all sites in the control (pre-implementation) and post-implementation (intervention) phases.


Between June 2020 and September 2021, 15 clusters including 2,120 patients were included. Of the 1,505 patients analyzed from sites following implementation, 1,159 (77.0%) were considered low risk and no anticoagulation was recommended. In this low-risk group, 1,123/1,159 (96.9%) did not receive any anticoagulation prophylaxis. The rate of symptomatic VTE among this low-risk population was 0.7% (95% CI, 0.3-1.4%; n = 8/1,159). There was no difference in the rate of symptomatic VTE or bleeding between the sites during the control or post-intervention phases.


The authors conclude that patients with a TRiP(cast) score <7 who are not receiving anticoagulation have a very low risk of VTE. They also conclude that a large proportion of patients with lower limb trauma and immobilization can safely avoid thromboprophylaxis.


Lower extremity trauma and immobilization is a well-known risk factor for VTE. Some clinicians recommend prophylactic anticoagulation to reduce the risk of VTE. This study evaluated the effectiveness of a thrombophylactic avoidance strategy using the TRiP(cast) score. In many regions, it is uncommon to use thromboprophylaxis in general. The fact that more than 3-in-4 patients were at low risk and can safely avoid anticoagulation therapy according to this score supports the current approach in many regions of not using anticoagulation in general. However, it does not provide guidance on which patients are at high risk for VTE and should receive anticoagulation thromboprophylaxis.

Clinical Topics: Anticoagulation Management, Pulmonary Hypertension and Venous Thromboembolism, Vascular Medicine, Anticoagulation Management and Venothromboembolism

Keywords: Anticoagulants, Venous Thromboembolism

< Back to Listings