Age over 65 years and high levels of C-reactive protein are associated with the risk of preoperative deep vein thrombosis following closed distal femur fractures: a prospective cohort study

BACKGROUND: In this study, we investigated the epidemiological characteristics and predictors of preoperative new-onset deep vein thrombosis (DVT) in adult patients with closed distal femur fractures (DFFs). METHODS: The study was designed as a prospective cohort trial at the Third Hospital of Hebei Medical University. From October 2018 to June 2020, a total of 160 patients with closed DFFs were enrolled to assess the location and prognosis of preoperative DVT. The patients were followed up for 2 months. Duplex ultrasonography (DUS) was used to diagnose patients with DVT. The patients were divided into two groups (DVT group and non-DVT group). The DVT was then classified into proximal, distal, and mixed thromboses. The Mann-Whitney U test or t test, receiver operating characteristic (ROC) analyses, univariate Chi-square analyses, and multiple logistic regression analyses were used to analyze the adjusted predictors of DVT. RESULTS: The overall incidence of preoperative DVTs was 52.5% (n = 84), which was diagnosed at a mean period of 3.1 days after injury. Among patients diagnosed with DVTs, 50.0% (n = 42) had distal thrombosis while 47.6% (n = 40) had mixed thrombosis. The calf muscle veins were the most common sites of DVTs (90.5%, n = 76). Of note, 45.2% (n = 38) of diagnosed DVTs were completely recanalized at a mean period of 12.0 days after the initial (first) diagnosis. Multivariate analysis revealed that age of ≥ 65 years of age (odds ratio [OR], 4.390; 95% confidence interval [CI] 1.727–11.155; p = 0.002), C-reactive protein (CRP) levels exceeding 11 mg/L (OR 4.158; 95% CI 1.808–11.289; p = 0.001), platelet (PLT) levels over 217 × 109/L (OR, 2.55; 95% CI 1.07–6.07; p = 0.035), D-dimer levels over 1.0 mg/L (OR 3.496; 95% CI 1.483–8.237; p = 0.004), and an American Society of Anesthesiologists (ASA) score of III-V (OR 2.753; 95% CI 1.216–6.729; p = 0.026) were the independent risk factors of preoperative DVT. CONCLUSIONS: High levels of CRP, PLT, D-dimer, ASA, and ≥ 65 years of age increase the risk of preoperative DVTs in adult patients with closed DFFs. Thus, the prediction of preoperative DVTs can significantly be improved by identifying older patients over the age of 65, and establishing the biochemical cut-off values of CRP, PLT, ASA, and D-dimer. TRIAL REGISTRATION: No. 2018-026-1, 24 October 2018, prospectively registered. This trial was registered prospectively on 24 October 2018 before the first participant was enrolled. This study protocol conformed to the Declaration of Helsinki and approved by the Institutional Review Board. The ethics committee approved the study on the factors of prognosis for patients with fractures. Data used in this study were obtained from the patients who underwent orthopedic surgery between October 2018 and June 2020.