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Significant correlation seen between posterior acromial morphology, shoulder instability
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There was a significant correlation between specific acromial morphology and the direction of glenohumeral instability, according to results.
“In shoulders with posterior instability, the acromial is situated higher and is oriented more horizontally in the sagittal plane than in normal shoulders and those with anterior instability; this acromial position may provide less osseous restraint against posterior humeral head translation,” the authors wrote.
Researchers performed a retrospective study of 41 patients with unidirectional posterior instability and 41 patients with unidirectional anterior instability. Patients with instability were compared to 53 control patients with no instability, degenerative glenohumeral changes or acromial changes. Posterior acromial tilt, anterior acromial coverage, posterior acromial coverage, posterior acromial height and critical shoulder angle were among the radiograph measurements assessed.
Results from the logistic regression model showed posterior acromial height had the most significant correlation with posterior instability. Patients with posterior instability compared with patients with anterior instability had a significantly greater posterior acromial height. The odds ratio for posterior instability was 39 when investigators used a posterior acromial height cutoff of 23 mm. Shoulders with posterior instability compared with normal shoulders were significantly different with regard to posterior acromial height and posterior acromial coverage. However, in shoulders with anterior instability, no difference was seen compared with normal shoulders apart from the anterior acromial coverage. – by Monica Jaramillo
Disclosures: The authors report no relevant financial disclosures.
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