Inter-tubercle angle measured on MRIs may serve as a predictor for degenerative subscapularis tears in patients diagnosed with rotator cuff tears under arthroscopy: a case-control study

BACKGROUND: Subscapularis (SSC) tears are very common, but the mechanism of the tear remains unclear. Previous studies have revealed that SSC tears have associations with the reduction of coracohumeral distance and increase of coracoid overlap. However, existing parameters cannot explain the predominance of articular-side tears. Thus, new signs need to be found. METHODS: A total of 51 patients who were diagnosed as SSC tears were retrospectively included in the study from 2023 to 2024. 42 rotator cuff tear patients without SSC tears were also enrolled as the control group. With the arm in neutral rotation, the coracohumeral distance (CHD), coracoid overlap (CO), intertubercular angle (ITA), and humerus head-glenoid cavity ratio (HCR) were measured on MRI images of the coracoid disappearance plane. Independent samples t-test was used for analyzing the difference. RESULTS: The mean ITA in patients with SSC tears was 90.2 ± 11.2° (range, 62.4-126.3°) and was significantly higher (P = 0.0002) than that in control group (79.5 ± 10.8°; range, 55.7-109.3°). The HCR between both groups showed no significant difference (P = 0.193). CHD and CO measurements were consistent with previous studies. CONCLUSION: Our study confirmed the association between ITA and SSC tears. Patients with SSC tears tended to have a bigger ITA. However, the tendency of SSC tears was independent of HCR. ITA may serve as a potential predictor for SSC tears. KEY TERMS: rotator cuff tear; coracohumeral distance; coracoid overlap; inter-tubercle angle; humerus head-glenoid cavity ratio; subscapularis tears.