A new section of shoulder magnetic resonance imaging(MRI) used to assess fat infiltration of rotator cuff muscles

Background Accurately assessing the degree of fat infiltration in the rotator cuff muscles is essential. However, in patients with massive rotator cuff tears and significant retractions, assessing fat infiltration of the rotator cuff in the traditional scapular Y-view of Shoulder MRI is not very accurate. Purpose This study aimed to evaluate the reliability and reproducibility of the suprascapular notch sagittal section (r-view) for assessing fatty infiltration in the supraspinatus and infraspinatus muscles, with comparative analysis against the Y-view assessment results. Methods Magnetic resonance imaging data from 91 patients with rotator cuff tears(RTCs) were retrospectively analyzed. The patients were divided into three groups on the basis of the extent of retraction of rotator cuff tears. Fat infiltration of rotator cuff muscles was independently graded by three orthopedic surgeons via the Goutallier classification. The interclass and intraclass correlation coefficients(ICCs) were calculated to assess the consistency and repeatability of grading fat infiltration in the supraspinatus and infraspinatus using Y view and r view. The Wilcoxon rank-sum test was used to compare categorical variables of 3 groups (fat infiltration of the supraspinatus and infraspinatus graded in Y view and r view). Results In the 3 groups of patients, regardless of the supraspinatus or the infraspinatus, the interclass coefficients of fat infiltration grade in the r view were ≥ 0.80, with excellent interobserver agreement and reliability of evaluation. The intraclass coefficients of each reader for grading fat infiltration of the supraspinatus and infraspinatus in the r view were ≥ 0.80, indicating excellent intraobserver agreement and reproducibility. In the group with the most severe rotator cuff tear retraction, there was a significant difference in the degree of fat infiltration between Y view and r view. (P < 0.01) Conclusion The r view utilized in this study is a new section for assessing the fat infiltration of the supraspinatus and infraspinatus. In contrast to the conventional Y view, assessing fatty infiltration of the supraspinatus and infraspinatus muscles in the r view demonstrates better reliability and reproducibility, with less influence from tendon retraction. Levels of Evidence : Level III