A Study On The Method Of Measuring The Critical Shoulder Angle With MRI

PURPOSE:To find a new method to accurately measure the critical angle of shoulder on MRI.METHODS:The imaging datas of patients who accepted true anteroposterior(AP)radiographs and shoulder MRI examinations at the same time in Xiangya Third Hospital of Central South University from January 2021 to March 2022 were retrospectively analyzed,including 26 cases with rotator cuff tears as the experimental group and 29 cases without rotator cuff tear as the control group.The critical shoulder angle was measured and analyzed by traditional methods and new methods proposed in this experiment.RESULTS:In the experimental group,the average CSA measured by the traditional measurement method was 35.1 ° ± 2.7 °,and the average CSA measured by the new measurement method was 34.4 ° ± 2.6 °.In the control group,the average CSA measured by the traditional measurement method was 32.4 °± 2.3 °,and the average CSA measured by the new measurement method was 32.4 °± 2.3 °.There was no statistically significant difference in CSA measured by traditional measurement method and new measurement method in all subjects(P >0.05),and there was a statistically strong correlation between CSA measured by the two measurement methods in all subjects(r = 0.852,P<0.001).According to ROC curve analysis,the cut-off value of critical shoulder angle measured by the new measurement method is 34.25 °,the sensitivity is 0.58,and the specificity is 0.83.The accuracy of the cut-off value in predicting rotator cuff tear is medium(AUC = 0.709,P<0.05).CONCLUSION:The new method proposed in this experiment is feasible to accurately measure the CSA on shoulder MRI after innovatively excluding the possible measurement deviation caused by the glenoid version.