Determining the Causal Effect of Statins on Reducing the Incidence of Venous Thromboembolism after Ankle Fractures

Abstract

Category: Ankle; Other Introduction/Purpose: It can be challenging to decide when to give preventative medication for venous thromboembolism (VTE). It is challenging to identify VTE in its early phases, and surgeons disagree on when prophylaxis should be given and when to suspect VTE. Additionally, patients who are not at a high risk of VTE are advised not to take prophylaxis due to the potential risk of bleeding adverse events and the evidence does not fully support providing prophylaxis in isolated foot and ankle procedures (BAE). The effectiveness of prevention, particularly in isolated foot and ankle fractures, is debatable, and research into how patients react to statins is necessary. By utilizing causal inference techniques, this research simulates a randomized control trial (RCT) from observational data. Methods: Out of a total of 1,175 patients, 238 had confirmed VTE 180 days after the incidence of ankle fracture (Case group, n=238). The inclusion criteria were 1- ankle fracture diagnosed by a physician and confirmed radiologically via X-ray or CT scan; 2- Age of 18 years or older; 3- Symptomatic VTE confirmed by a clinician and through radiologic (Duplex ultrasound, CT angiography, and/or angiography). To infer causal effects, we took the three following steps: first, the causal diagram must be created. Second, the set of variables necessary for causal inference must be identified. Third, the average treatment effect should be estimated for different treatment regimens. Results: Table 1 shows the incidence of VTE among patients who had VTE chemoprophylaxis. A non-significant 2.9% increase in VTE incidence was found, 95% CI [-1%, 7%]. The results state that, if a patient is already taking Statins, the incidence of VTE is reduced by 1%, 95% CI [-4.2%, 2.8%] as compared to patients who are not taking the drug which is not statistically significant. This indicates that there is no significant difference between administering VTE prophylaxis or not, in patients that are already consuming Statins. On the contrary, for patients in the sample that are not already taking Statins, the VTE incidence increases by 6%, 95% CI [1.6%, 10%] compared to no treatment administration which is significant since the confidence interval does not contain 0. Conclusion: Our findings provide more evidence that VTE prophylaxis may not, on average, be successful in lowering the incidence of VTE after ankle fracture, particularly in individuals who do not take Statins. To put it another way, doctors may decide not to give extra prophylaxis to avoid VTE in isolated ankle fractures if a patient is on Statins. Here, we established the causal inference methodology that can help us reproduce the results of an expensive RCT.