Evaluation of complete and incomplete subscapularis tendon tear on preoperative magnetic resonance imaging

Background: This study aims to evaluate the significance of preoperative magnetic resonance imaging findings to predict subscapularis tear confirmed at arthroscopic surgery. Methods: Sixty-four consecutive shoulders that underwent preoperative magnetic resonance imaging examination and arthroscopic shoulder operations were retrospectively reviewed. Under arthroscopic examination, complete subscapularis tear was defined as a full-thickness tear and incomplete subscapularis tear as tendon detachment larger than 5 mm from the insertion on the joint side. Results: In arthroscopic findings, they were included 11 shoulders with complete subscapularis tear, 13 with incomplete subscapularis tear, and the remaining 28 shoulders without subscapularis tear. Subscapularis discontinuity by axial magnetic resonance imaging had the highest sensitivity and specificity in detecting complete subscapularis tear compared with other magnetic resonance imaging findings. Long head biceps subluxation or dislocation showed significantly higher prevalence in the complete and incomplete subscapularis tear groups than in the group with no tear. Incomplete subscapularis tear groups had a higher incidence of superior subscapularis recess fluid, and this fluid was present in all the shoulders with incomplete subscapularis tear. Conclusions: The presence of subscapularis discontinuity is useful for diagnosis of complete subscapularis tear. In addition, in cases of incomplete subscapularis tear, the presence of superior subscapularis recess fluid had 100% sensitivity. Thus, this finding may be a characteristic diagnosis of subscapularis tear including incomplete tear.