Increased Glenoid Retroversion Is Associated With Increased Rotator Cuff Strength in the Shoulder

Background: The rotator cuff muscles are critical secondary stabilizers in the shoulder. Increased glenoid retroversion and rotator cuff strength have been associated with the risk of posterior shoulder instability; however, the effect of increased glenoid retroversion on rotator cuff strength remains unclear. Purpose/Hypothesis: The purpose was to examine the association between glenoid version and rotator cuff strength in the shoulder in a young and healthy population with no history of shoulder instability. The hypothesis was that increased glenoid retroversion would be associated with increases in rotator cuff muscle strength. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A prospective cohort study was conducted over a 4-year period within a high-risk population to identify the risk factors for shoulder instability. Analyzed participants included 574 freshmen entering a United States service academy. Baseline data collected upon entry into the study included magnetic resonance imaging measurements of glenoid version. Rotator cuff strength was also assessed at baseline using a handheld dynamometer. Internal and external rotation strength were assessed with the glenohumeral joint positioned in neutral and in 45 degrees of abduction. The current study represents an analysis of the baseline data from this cohort. Results: The mean age, height, and weight of participants was 18.77 +/- 0.97 years, 176.81 +/- 8.48 cm, and 73.80 +/- 12.45 kg, respectively. The mean glenoid version at baseline was 7.79 degrees +/- 4.85 degrees of retroversion. Univariate linear regression analyses demonstrated that increased glenoid retroversion was associated with increased internal and external rotation strength of the rotator cuff in neutral and 45 degrees of abduction (P < .001). Similar results were observed in multivariable models controlling for important confounding variables. Conclusion: The results of this study demonstrate that as glenoid retroversion increases, internal and external rotation strength of the rotator cuff also increase in a young and healthy athletic population. These compensatory changes may contribute to increased glenohumeral dynamic stability in the presence of worse static stability with increasing retroversion.