Another Assessment of Fat Degeneration of Retracted Supraspinatus Muscle

Background: The purpose of this study was to assess the relevance of preoperative magnetic resonance imaging (MRI) evaluation by occupation ratio (OR) at maximum diameter of supraspinatus muscle. Methods: Patients from the Inje University Sanggye Paik Hospital who received rotator cuff repair and underwent pre- and postoperative MRI were selected as subjects of this study. On T1-weighted MRIs, OR of fat and muscle at Y-shaped view, OR at a location on supraspinatus muscle where its diameter was maximum on coronal view, and pre- and postoperative Goutallier Classification and changes in the tangent sign were measured. Statistical significance of postoperative OR was assessed regarding time from symptom onset to surgery, size of rotator cuff tear, preoperative OR, and the difference between ORs measured at maximum diameter of supraspinatus muscle and Y-shaped view. Results: Preoperative OR at Y-shaped view was $52.28{\pm}8.57$ (32.5-65.3). Preoperative OR difference between maximum diameter and Y-shaped view was $13.76{\pm}10.51$ (2.38-42.04), and Pearson correlation coefficient was 0.604 (p=0.001). Postoperative OR at Y-shaped view was $63.77{\pm}9.35$ (37.3-76.1). Pearson correlation coefficient of pre- and postoperative Goutallier Classification was -0.579 (p=0.002) and Pearson correlation coefficient of the postoperative difference between ORs measured at maximum diameter of supraspinatus muscle and Y-shaped view was -0.386 (p=0.047). Conclusions: Fatty degeneration of supraspinatus muscle in rotator cuff tear patients should be evaluated not only in the conventional Y-shaped view, but also at location of maximum diameter of supraspinatus muscle to establish patients' therapeutic plan.