Coracohumeral Distances and Correlation to Arm Rotation An In Vivo 3-Dimensional Biplane Fluoroscopy Study

Background: Reduced coracohumeral distances have been reported to be associated with anterior shoulder disorders such as subscapularis tears, biceps tendon injuries, and leading edge supraspinatus tears. Purpose: To determine the variability in coracohumeral distance as a function of arm rotation in healthy male subjects. The null hypothesis was that no differences in coracohumeral distance would exist with respect to arm rotation. Study Design: Descriptive laboratory study. Methods: A total of 9 male participants who had full range of motion, strength, and no prior surgery or symptoms in their tested shoulders were enrolled in this institutional review board-approved study. Computed tomography scans of the shoulder were obtained for each subject. A dynamic biplane fluoroscopy system recorded internal and external shoulder rotation with the arm held in the neutral position. Three-dimensional reconstructions of each motion were generated, and the coracohumeral distance and coracoid index ( lateral extension of the coracoid) were measured. Results: The mean coracohumeral distance in neutral rotation was 12.7 +/- 2.1 mm. A significantly shorter minimum coracohumeral distance of 10.6 +/- 1.8 mm was achieved (P = .001) at a mean glenohumeral joint internal rotation angle of 36.6 degrees +/- 19.2 degrees. This corresponded to a reduction in coracohumeral distance of 16.4%(range, 6.6%-29.8%). Themean coracoid index was 14.2 +/- 6.8 mm. A moderate correlation (R = -0.75) existed between the coracohumeral distance and coracoid index. Conclusion: Coracohumeral distance was reduced during internal rotation. Decreased coracohumeral distance was correlated with larger coracoid indices.