Background: We evaluated the anterior shoulder translation at 90 degree abduction in the scapula plane at various external and internal rotations.
Methods: Forty patients with recurrent anterior shoulder instability were enrolled in this study. They all underwent operative treatment and had Bankart lesion as the main pathology of recurrent anterior dislocation. The mean age at surgery was 28 years old (13-73 years old). Under general anesthesia at supine position, the examiner kept the shoulder at 90° abduction, drew the humeral head (HH) anterior, and assessed the shift of HH to glenoid from maximum external rotation to maximum internal rotation at every 10 degree interval.
Results: There was no case of HH movement over the glenoid rim and it never reduced spontaneously (grade 3), 6 cases where HH moved over the rim but reduced spontaneously (grade 2), 21 HH run on the rim (grade 1), and 11 cases where HH slightly moved in the healthy shoulder. In the disease shoulders, 7 shoulders were grade 3, 26 shoulders were grade 2, and 5 shoulders were grade 1. Twenty-seven healthy shoulders with grade 1 and 2 showed translation over grade 1 in the middle range of rotation and no translation at maximum external and internal rotation. Comparing the healthy to the disease side in the same laxity grade, there was no significant differences in grade 1 and 2 in Mann-Whitney U test.
Conclusion: The anterior translation was one of the important factors to make laxity symptomatic in anterior shoulder instability, however, the other factors such as pain or catching sensation may be related to being symptomatic or not.
