Preoperative D-Dimer and Documented Perioperative Deep Vein Thrombosis in AO/OTA 43A-B Distal Tibial Fractures: Association and Diagnostic Discrimination in a Single-Center Retrospective Cohort Study

Background:D-dimer is associated with fracture-related deep vein thrombosis (DVT), but evidence in narrowly defined distal tibial fracture cohorts is limited.We evaluated diagnostic discrimination and exploratory incremental value in adults with AO/OTA 43A-B fractures. Material/Methods:This retrospective cohort included 86 adult patients treated from 2019 to 2025; a total of 22 patients had documented perioperative DVT.Logistic regression, receiver operating characteristic analysis, Box-Tidwell linearity and leave-one-out influence assessments, and repeated nested 5-fold cross-validation were used.Youden-cutoff measures were considered same-cohort apparent estimates.The intervals from injury to D-dimer sampling and from sampling to duplex ultrasonography were not standardized under the retrospective institutional workflow. Results:Median preoperative D-dimer was 10.92 mg/L fibrinogen-equivalent units (FEU) with DVT and 2.94 mg/L FEU without DVT (P < 0.001).Each 1-mg/L FEU increase was associated with higher adjusted DVT odds (odds ratio, 2.60; 95% CI, 1.53-4.43).No departure from linearity was detected (P = 0.753), and leave-one-out estimates remained positive.The apparent same-cohort AUC was 0.929 (95% bootstrap CI, 0.860-0.983).The same-cohort cutoff of 6.87 mg/L FEU had apparent sensitivity of 81.8% and specificity of 96.9%.The averaged out-of-fold AUC increased from 0.644 to 0.915 after adding D-dimer; Brier score decreased from 0.186 to 0.080. Conclusions:Under the observed institutional workflow, preoperative D-dimer was associated with documented perioperative DVT.The 6.87-mg/L FEU cutoff is a candidate for prospective validation, not an established imaging threshold, and D-dimer should not replace duplex ultrasonography.