Abstract:Objective To construct a visualized model for early warning of contralateral ligament injury risk after arthroscopic anterior cruciate ligament (ACL) reconstruction, and to conduct internal validation of the warning model, with a view to providing a concise, intuitive, and efficient individualized assessment tool for medical staff to evaluate the risk of contralateral ligament injury in patients with ACL injury after surgery.Methods 583 patients with ACL injuries who underwent arthroscopic ACL reconstruction surgery from January 2021 to January 2024 were selected. Excluding 51 cases those were lost to follow-up or had incomplete data, clinical data of 532 patients were finally included. According to whether there was a contralateral ligament injury, patients were categorized into an occurrence group (n = 42) and a non-occurrence group (n = 490). Data from the two groups of patients were compared using single-factor analysis. R software was employed to obtain predictive factors and regression coefficients through multivariate binary Logistic regression analysis. A visual nomogram early warning model was established, and internal and external validations were conducted using calibration curves, C index, and decision curves to assess consistency, discrimination, and clinical utility.Results Multivariate Logistic regression analysis revealed that athletes, females, knee joint buckling, positive Lachman test results at 6 weeks post-surgery, International Knee Documentation Committee (IKDC) score at 3 months post-surgery, age < 20 years, and preoperative posterior tibial slope (PTS) were influencing factors for contralateral ligament injury after arthroscopic ACL reconstruction (P < 0.05). Based on this, a visual nomogram warning model was established using R software. After Bootstrap testing, the model demonstrated a C index of 0.892. Draw the receiver operating characteristic curve (ROC curve), the model's area under the curve (AUC) values in the internal and external validation sets were 0.820 (95%CI: 0.751 ~ 0.890) and 0.799 (95%CI: 0.712 ~ 0.886), respectively. The calibration curves indicated that the slopes in both the internal and external validation sets were approximately 1. In the decision curve, the model demonstrated significant net benefit in both the internal and external validation sets.Conclusion The contralateral ligament injury after arthroscopic ACL reconstruction is influenced by age, gender, positive Lachman test at 6 weeks postoperatively, knee joint buckling, IKDC score at 3 months postoperatively, preoperative PTS, and athlete status. The visualized early warning model constructed based on these factors has good clinical application value and can guide clinicians to carry out targeted interventions.