Abstract: Objective To examine the causes of incision infections following lower extremity open fractures and develop a predictive model for assessing the risk.Methods A total of 104 patients with open fractures of the lower extremity,who received internal fixation from January 2022 to August 2023.According to whether there was incision infection after the operation,the patients were divided into infection group and non-infection group.The aim of the study was to analyze the distribution of pathogenic bacteria causing postoperative incision infections.Single-factor and multifactor Logistic regression analyses were employed to examine the factors influencing postoperative incisional infections.Subsequently,a risk prediction model for these infections was developed.The predictive capacity of this model was assessed using ROC curves.Results In the cohort of 104 patients with open fractures of the lower limb,the occurrence rate of postoperative incision infections was 19.23%.A total of 45 non-repeated pathogenic bacteria were isolated,among which gram-positive bacteria accounted for 53.33%,gram-negative bacteria 42.22%,fungi 4.44%.Gram-positive bacteria showed 100% resistance to ampicillin/sulbactam and penicillin,while resistance rates for erythromycin and clindamycin exceeded 90%.Among gram-negative bacteria,resistance rates to cefazolin,sulfamethoxazole/trimethoprim,levofloxacin,ampicillin/sulbactam,ciprofloxacin,and gentamicin were all above 67%.Notably,resistance rates for cefazolin,sulfamethoxazole,and trimethoprim surpassed 90%.Univariate and multifactorial Logistic stepwise regression analysis highlighted that time elapsed from injury to surgery,duration of surgery,length of hospital stay,perioperative prophylactic medication,and Gustilo classification were significant risk factors for postoperative incisional infections in patients with the condition (P<0.05).The ROC curves illustrated that the risk prediction model accurately forecasted the incidence of postoperative incisional infections in patients with open fractures of the lower extremity,with an area under the curve of 0.861 (95%CI:0.811 to 0.911),boasting a sensitivity of 90.50% and a specificity of 72.92%.Conclusion The main pathogen of wound infection after open fracture of lower extremity is Gram-negative,the time from injury to operation,operation time,hospitalization time,prophylactic medication during perioperative period and GUSTILO classification were the influencing factors of postoperative wound infection.In addition,the establishment of risk prediction model has a good prediction effect on the incidence of postoperative wound infection in patients with this disease.

Key words: lower limb fracture, wound infection, pathogen, model construction