Objective:

To explore the association between D-dimer levels and the likelihood of preoperative deep vein thrombosis (DVT) in patients with ankle fractures.

Approach:

• Study Design: Retrospective study of ankle fracture patients admitted to Xi'an Honghui Hospital from January 2024 to November 2025.
• DVT Identification: Preoperative DVT was identified using Doppler ultrasound.
• Statistical Analysis: Multivariate logistic regression and generalized additive models were used to analyze the relationship between D-dimer levels and DVT.

Key Findings:

• 13.45% of the 818 patients developed preoperative DVT.
• D-dimer was identified as an independent risk factor for preoperative DVT (OR = 1.14, 95% CI: 1.03–1.26, P = 0.010).
• A nonlinear relationship was found between D-dimer levels and DVT risk, with an inflection point at 3.92 mg/L.

Interpretation:

Below the threshold of 3.92 mg/L, each 1 mg/L increase in D-dimer was associated with a significantly higher odds of DVT (OR = 1.60, 95% CI: 1.24–2.06, P < 0.001).

Limitations:

• Retrospective design may introduce selection bias.
• Data collected from a single hospital may limit generalizability.

Conclusion:

D-dimer is independently associated with preoperative DVT in ankle fracture patients, and the relationship appears to be non-linear.