Is there any evidence, for or against, thromboprophylaxis in patient in lower

Evidence supports the use of thromboprophylaxis in patients with lower limb fractures managed conservatively with casts when the risk of venous thromboembolism (VTE) outweighs the risk of bleeding. NICE guidelines (NG89) recommend considering pharmacological prophylaxis with low molecular weight heparin (LMWH) or fondaparinux sodium for individuals with lower limb immobilisation whose VTE risk is higher than their bleeding risk, including those managed non-surgically in casts NICE NG89.

Systematic reviews and meta-analyses of randomized controlled trials demonstrate moderate-quality evidence that LMWH significantly reduces the incidence of deep vein thrombosis (DVT) in adult patients with lower limb immobilisation by about half when compared to no prophylaxis or placebo (odds ratio ~0.45), including in conservatively managed patients with fractures immobilised in plaster casts Zee et al. 2017 Horner et al. 2020. Evidence also shows fondaparinux may be even more effective than LMWH, although derived from fewer studies Horner et al. 2020.

Although the absolute risk of pulmonary embolism (PE) and symptomatic VTE in this population is relatively low (approximately 1.8% to 5.5% without prophylaxis), thromboprophylaxis reduces symptomatic VTE events (odds ratio ~0.40) Zee et al. 2017 Horner et al. 2020. The risk of major bleeding associated with thromboprophylaxis in this outpatient group is very low and not conclusively increased, with primarily minor bleeding events reported Zee et al. 2017 Horner et al. 2020. No deaths due to PE were reported in the analyzed trials Zee et al. 2017.

The current NICE guideline defines lower limb immobilisation as any clinical decision that prevents normal weight-bearing or use of the affected limb, thereby warranting individual VTE risk assessment NICE NG89. Clinical decision-making should include assessment of patient-specific risk factors (such as age, BMI, injury pattern, and comorbidities) to personalize thromboprophylaxis decisions Horner et al. 2020. However, available risk assessment models lack robust external validation and thus should be applied cautiously NICE NG89 Horner et al. 2020.

Pharmacological prophylaxis is generally recommended for the duration of lower limb immobilisation (commonly four to six weeks) or until the person regains mobility NICE NG89. Shared decision-making with patients regarding the benefits and risks of thromboprophylaxis is essential, including provision of education on VTE symptoms and strategies to mitigate risk such as hydration and mobilisation of the unaffected limb Horner et al. 2020 NICE NG89.

There is no current trial evidence supporting the use of direct oral anticoagulants (DOACs) for thromboprophylaxis in this setting, so LMWH or fondaparinux remain the recommended pharmacological agents NICE NG89 Horner et al. 2020. Mechanical prophylaxis such as intermittent pneumatic compression may be considered if pharmacological methods are contraindicated NICE NG89.