Preoperative Venous Thromboembolism in Elderly Patients with Hip Fractures: Independent Risk Factors and Interactions Between D-Dimer and Clinical Variables.

ObjectivesTo explore independent risk factors for preoperative venous thromboembolism (VTE) and to evaluate the predictive value of D-dimer levels and their interactions with key clinical variables.MethodsIn total, 1,004 elderly patients with hip fractures (≥60 years) admitted between December 2012 and February 2023 were retrospectively analyzed. Routine preoperative lower-extremity venous ultrasonography was performed to screen for deep vein thrombosis (DVT), and computed tomography pulmonary angiography was conducted when pulmonary embolism (PE) was clinically suspected. Multivariable logistic regression identified independent risk factors and interaction analyses assessed modifiers of the D-dimer-VTE association. Model performance was evaluated by ROC curves and AUC.ResultsThe incidence of preoperative VTE was 21.4% (215/1,004, 95% CI: 19.0%-24.1%), comprising 21.2% (213/1,004, 95% CI: 18.8%-23.9%) for DVT and 0.9% (9/1,004, 95% CI: 0.5%-1.7%) for PE, with seven patients having both DVT and PE. Multivariable logistic regression identified the following independent predictors: cardiovascular disease (OR = 2.787, 95% CI: 1.985-3.950, p < 0.001), injury-to-admission time of >1 day (OR = 2.471, 95% CI: 1.483-4.085, p < 0.001), history of VTE (OR = 3.676, 95% CI: 1.285-10.964, p = 0.016), shortened activated partial thromboplastin time (APTT) (OR = 0.941, 95% CI: 0.909-0.972, p < 0.001), and lower hemoglobin (OR = 0.983, 95% CI: 0.975-0.991, p < 0.001). D-dimer alone had poor discrimination for VTE (AUC = 0.533). Interaction analysis showed that sex (p for interaction = 0.018), injury-to-admission time (p for interaction = 0.002), and bedridden time (p for interaction < 0.001) significantly modified the association between D-dimer and preoperative VTE risk. The baseline multivariable model yielded an AUC of 0.728 for predicting VTE, which improved to 0.742 after including D-dimer interaction terms (ΔAUC = 0.013, 95% CI: 0.000-0.027, p < 0.05).ConclusionsCardiovascular disease, injury-to-admission time of >1 day, a history of DVT or PE, shortened APTT, and lower hemoglobin were identified as independent risk factors for preoperative VTE in elderly patients with hip fractures. Although D-dimer alone demonstrated limited discriminatory ability, incorporating its interactions with sex, injury-to-admission time, and bedridden time improved predictive performance.