This study asks whether acromial shape, measured before any shoulder pathology developed, predicts future disease. Using 20-year-old preoperative radiographs, the authors measured critical shoulder angle (CSA) and acromion index (AI), then re-examined patients two decades later. It is the first attempt to test these measures with true premorbid data rather than radiographs of already-diseased shoulders.
The key teaching point: association is not causation. Almost every study linking CSA or AI to cuff tears and OA used radiographs of shoulders that were already diseased, so the measured angle could be a result of the pathology rather than its cause.
This is the first study to measure CSA and AI before disease onset and follow patients 20 years. Neither measure predicted future rotator cuff tears or osteoarthritis. Practically, this weakens the rationale for lateral acromioplasty to prevent cuff disease. As long as the deltoid insertion is intact, the resultant deltoid force vector is unchanged regardless of how the acromion is trimmed.
Weigh this against the limitations. The cohort was small and underpowered (30 patients versus the 204 needed), so treat the result as hypothesis-generating rather than definitive. The debate over whether acromial shape causes cuff disease remains unsettled.
This study asks whether acromial shape, measured before any shoulder pathology developed, predicts future disease. Using 20-year-old preoperative radiographs, the authors measured critical shoulder angle (CSA) and acromion index (AI), then re-examined patients two decades later. It is the first attempt to test these measures with true premorbid data rather than radiographs of already-diseased shoulders.
The key teaching point: association is not causation. Almost every study linking CSA or AI to cuff tears and OA used radiographs of shoulders that were already diseased, so the measured angle could be a result of the pathology rather than its cause.
This is the first study to measure CSA and AI before disease onset and follow patients 20 years. Neither measure predicted future rotator cuff tears or osteoarthritis. Practically, this weakens the rationale for lateral acromioplasty to prevent cuff disease. As long as the deltoid insertion is intact, the resultant deltoid force vector is unchanged regardless of how the acromion is trimmed.
Weigh this against the limitations. The cohort was small and underpowered (30 patients versus the 204 needed), so treat the result as hypothesis-generating rather than definitive. The debate over whether acromial shape causes cuff disease remains unsettled.