Study on the Risk Factors of Meniscus Extrusion in Patients with Medial Meniscal Injury

Objective: This study aimed to investigate the risk factors for medial meniscus extrusion and to construct a logistic regression model based on radiography and magnetic resonance imaging (MRI). Methods: A retrospective analysis was conducted on 156 patients with medial meniscus injuries admitted from August 2020 to June 2023. Based on an extrusion value of ≥3 mm on non-weight-bearing coronal MRI, the patients were divided into an extrusion group (71 cases) and a non-extrusion group (85 cases). Univariate unconditional logistic regression analysis was initially performed to screen for potential risk factors. Subsequently, multivariate unconditional logistic regression analysis was applied to identify independent risk factors for meniscus extrusion and to establish the logistic regression model. The diagnostic accuracy of the model was evaluated using the receiver operating characteristic(ROC) curve. Results: A univariate analysis revealed that the extrusion group had higher values for age, female proportion, meniscus tears at various locations (anterior horn/body/root), knee Kellgren-Lawrence (K-L) grade ≥Ⅲ, cartilage injury Recht grade > Ⅲ, and presence of genu varum. Multivariate logistic regression showed that based on radiography indicators, the knee K-L grade ≥Ⅲ (OR=0.051) and presence of genu varum (OR=0.152) were independent risk factors for extrusion. The area under the ROC curve of medial meniscus extrusion was 0.902, with a sensitivity of 80.0% and specificity of 100%. After combining MRI indicators, medial meniscus root tear (OR=0.053), knee K-L grade ≥Ⅲ (OR=0.160), cartilage injury Recht grade > Ⅲ (OR=0.184), and presence of genu varum (OR=0.177) were independent risk factors for extrusion. The area under the ROC curve of medial meniscus extrusion was 0.975, with a sensitivity of 100% and specificity of 87.5%. Conclusion: The medial meniscus root tear, knee K-L grade ≥Ⅲ, cartilage injury Recht grade > Ⅲ, and presence of genu varum were the primary risk factors of medial meniscus extrusion. The radiography model can serve as a clinical screening tool, while the model combining MRI offers more accurate assessment of individual risk, supporting the development of personalized intervention strategies (such as meniscus repair combined force line correction).