Abstract:Objective To investigate the relationship between skeletal muscle mass index (SMI) and non-traumatic rotator cuff tear(RCT) in patients with type 2 diabetes mellitus (T2DM). Methods The clinical data of 180 T2DM patients who were hospitalized in the Department of Endocrinology and Orthopedics, the Third People's Hospital of Jinzhong from June 2020 to December 2022 were retrospectively analyzed. According to the results of MRI and medical history, the patients were divided into T2DM+RCT group (n=80) and T2DM+ non-RCT group (n=100). The general data, body fat ratio, skeletal muscle mass, duration of diabetes, glycosylated hemoglobin (HbA1c) and other factors were compared between the two groups. Binary logistic regression was used to analyze the risk factors for non-traumatic RCT in T2DM patients. The receiver operating characteristic (ROC) curve was used to analyze the predictive value of various factors for non-traumatic RCT in T2DM patients. Results The proportion of female, body weight, body mass index(BMI), duration of diabetes, body fat ratio and HbA1c level in T2DM+RCT group were higher than those in T2DM+ non-RCT group (P< 0.05). The SMI was lower than that of the T2DM+ non-RCT group ［6.10 (5.50,7.18) kg/m²vs 5.40 (4.50,6.10) kg/m²,Z=4.443,P<0.01］. Binary logistic regression analysis showed that SMI, BMI, duration of diabetes and HbA1c were influencing factors for RCT. The ROC curve showed that the optimal cut-off value of SMI in diagnosing RCT in T2DM patients was 5.15 kg/m², with a sensitivity of 48.80% and a specificity of 82.00%, and AUC=0.693 (95%CI: 0.614-0.771). The combination of SMI, BMI, duration of diabetes and HbA1c had the highest diagnostic value, with a sensitivity of 81.30% and a specificity of 91.00%, and AUC=0.926 (95%CI: 0.885-0.966). Conclusion There is a correlation between SMI and non-traumatic RCT in diabetic patients, which has a particular predictive value for non-traumatic RCT.