This retrospective cohort study from Balgrist University Hospital compares acromial morphology on true lateral radiographs in 41 patients with recurrent unidirectional posterior instability, 41 age- and sex-matched patients with anterior instability, and 53 normal control shoulders — asking whether the shape and position of the acromion in the sagittal plane predicts the direction of glenohumeral instability.
When evaluating a young patient with recurrent posterior shoulder instability, measure posterior acromial height on the true lateral (Neer Y-view): a PAH above 23 mm carries an OR of 39 for posterior instability and should prompt consideration of whether bony acromial architecture — not just soft tissue laxity — is driving the problem.
A steep, overhanging "Swiss chalet" acromion is essentially incompatible with recurrent posterior instability and should raise doubt about the diagnosis if present.
This retrospective cohort study from Balgrist University Hospital compares acromial morphology on true lateral radiographs in 41 patients with recurrent unidirectional posterior instability, 41 age- and sex-matched patients with anterior instability, and 53 normal control shoulders — asking whether the shape and position of the acromion in the sagittal plane predicts the direction of glenohumeral instability.
When evaluating a young patient with recurrent posterior shoulder instability, measure posterior acromial height on the true lateral (Neer Y-view): a PAH above 23 mm carries an OR of 39 for posterior instability and should prompt consideration of whether bony acromial architecture — not just soft tissue laxity — is driving the problem.
A steep, overhanging "Swiss chalet" acromion is essentially incompatible with recurrent posterior instability and should raise doubt about the diagnosis if present.