A novel diagnostic method to predict subscapularis tendon tear with sagittal oblique view magnetic resonance imaging

Purpose: To find novel measurement guidelines correlating with known tear size on two sagittal oblique views (en-face view and Y-view). Methods: From a series of arthroscopic rotator cuff repair cases between 2012 and 2015, 50 patients were randomly selected from each of six subscapularis tear classifications. Due to rarity of type IV lesions, 272 shoulders were included. En-face view and Y-view in sagittal plane MRI were selected. Image evaluation was retrospectively performed by two researchers independently. In en-face view, anatomical line connecting the coracoid tip to the glenoid base designated as the base-to-tip line was used for thickness measurement and classification. Grading according to base-to-tip line, overlapped segment of base-to-tip line, thickness of subscapularis, and fluid accumulation were measured. In Y-view, a tangent line was drawn through the scapular spine and the coracoid. Parallel lines were then made. Grading according to tangent line, vertical length, cephalic width, caudal width, and fluid accumulation was measured. Results: In en-face view, grading according to base-to-tip line and overlapped segment of base-to-tip line showed differences in subscapularis tendon tear types IIB, III, and IV compared to the normal group. Thickness of subscapularis showed differences in types III and IV. No significant difference was observed in fluid accumulation. In Y-view, grading according to tangent line, vertical length, cephalic width, and fluid accumulation showed significant differences in types III and IV. Caudal width in Y-view was significantly different only in type IV. Conclusion: Several measurement parameters in two additional views in sagittal–oblique MRI (en-face view and Y-view) showed different degrees of subscapularis tendon tears. Grading of base-to-tip line is easy to use and helps diagnose partial subscapularis tear. Level of evidence: III.