Association Between Rotator Cuff Tears and Shoulder MRI Parameters: Importance of Arthroscopic Validation in Coronal Acromiohumeral Interval Measurement.

Background: Magnetic resonance imaging (MRI) measurement parameters-the standard noninvasive diagnostic method for rotator cuff tears (RCTs)-have been used to compare groups with and without RCTs. Arthroscopy is used in definitive diagnosis and treatment.

Purposes: To evaluate the association between RCT and shoulder angles and distances on MRI in patients with and without arthroscopically validated RCT and to determine whether the degree of rotator cuff fatty degeneration affects the MRI measurements.

Study design: Cross-sectional study; Level of evidence, 3.

Methods: Shoulder measurements on MRI were compared between patients with and without RCT as confirmed by shoulder arthroscopy performed by a single surgeon between 2019 and 2024, and non-RCT patients without arthroscopic confirmation. Interobserver reliability (Fleiss kappa coefficient) was calculated for the measurements. The groups were compared using the independent t test or the Mann-Whitney U test. The RCT group was further divided according to the level of fatty degeneration (Goutallier types 0-1-2 vs types 3-4) for subanalysis.

Results: In addition to the 368 RCT and 55 non-RCT patients with arthroscopic confirmation, there were 92 non-RCT patients without arthroscopic confirmation. The sagittal acromiohumeral interval (AHI) (8.32 vs 9.24 mm), coronal AHI (7.87 vs 8.96 mm), and coronal AHI/glenoid height ratio (22.63% vs 24.88%) were significantly lower in the patients with RCT (P < .001, P < .001, and P = .001, respectively). In contrast, the critical shoulder angle (CSA) (33.17° vs 31.92°) and the glenoid width/humeral head coverage ratio (57.52% vs 55.7%) were significantly higher in the patients with RCT (P = .037 and P = .017, respectively). Higher rotator cuff fatty degeneration levels (Goutallier types 3-4) further increased these differences within the patients with RCT (P < .001 for all). When the arthroscopically validated and nonvalidated non-RCT patients were compared, coronal AHI and AHI/glenoid height ratio values were found to be significantly lower in the nonvalidated group (P = .034 and P = .047, respectively).

Conclusion: In this study, RCT was associated with decreased sagittal AHI, coronal AHI, and coronal AHI/glenoid height ratios and increased CSA and glenoid width/humeral head coverage ratios.