Double-Blinded Randomized Study of the Correlation between Simple Radiography and Magnetic Resonance Imaging in the Evaluation of the Critical Shoulder Angle: Reproducibility and Learning Curve

To evaluate the feasibility of magnetic resonance imaging (MRI) to obtain the critical shoulder angle (CSA) comparing the results obtained through radiography and MRI, and assess the learning curves. In total, 15 patients were evaluated in a blinded and randomized way. The CSA was measured and compared among groups and subgroups. The mean angles measured through the radiographic images were of 34.61 ± 0.67 and the mean angles obtained through the MRI scans were of 33.85 ± 0.53 ( = 0.29). No significant differences have been found among the groups. The linear regression presented a progressive learning curve among the subgroups, from fellow in shoulder surgery to shoulder specialist and radiologist. There was no statistically significant difference in the X-rays and MRI assessments. The MRI seems to have its efficacy associated with more experienced evaluators. Data dispersion was smaller for the MRI data regardless of the experience of the evaluator.