F2 and deep vein thrombosis: According to the P value, disease duration > 8.5 years, operation time > 169 min, intraoperative blood loss > 102 ml, BMI > 26.7 kg/m2, preoperative D-dimer > 0.29 mg/L, prothrombin time < 10.7s and INR < 0.98 were finally analyzed in the univariate analysis and multivariate logistic regression model to demonstrate the risk factors of DVT.