The (T) thrombosis (I) in patients with (L) lower (L) limb (I) injuries (R)requiring (I) immobilisation (TILLIRI) study: A prospective observational multicentre study

Temporarily immobilising an injured lower limb is a recognised predisposing factor for the development of venous thromboembolism (VTE). We aim to conduct a prospective study to measure the incidence of VTE after temporary lower limb immobilisation. The study will also measure VTE risk factors in this patient cohort and identify those risk factors that are predictors of developing VTE. Finally, this study will validate the Thrombosis Risk Prediction for patients with cast immobilisation (TRiP (cast)) risk assessment model. The planned study design will be prospective and multicentre, including 15 participating sites within the Irish Network for VTE Research (INViTE). Consecutive patients aged 18 years and older with an immobilised injured lower limb will be eligible for inclusion. We will collect the relevant clinical variables at the index emergency department (ED) visit. The primary outcome will be the incidence of symptomatic VTE within three months after the injury. We will include VTE predictors in a multivariable logistic regression model, with VTE occurrence as the outcome variable. The TRiP (cast) model will be prospectively validated for first time using the Thrombosis In patients with Lower Limb Injuries Requiring Immobilisation (TiLLIRI) cohort. The association between lower limb immobilisation and VTE has been documented for over seventy-five years. However, the benefits of pharmacological thromboprophylaxis are still unclear. Identifying patients at a higher risk of VTE after immobilising an injured lower limb will help patient-focused benefit-risk analysis to inform clinical decision making and treatment decisions. The TiLLIRI study will address this critical clinical knowledge gap in the first-ever large prospective multicentre observational study of its kind. The results of this study are likely to inform future clinical trials and prospective management studies and to impact upon patient safety positively.