This study tests whether the critical shoulder angle (CSA) separates patients with rotator cuff tears from those with glenohumeral osteoarthritis and controls. It also compares how reliably the CSA can be measured on radiographs versus MRI. Three age-matched groups of 10 patients each were measured by three independent observers.
When you evaluate a shoulder pain patient, look at the CSA on a true AP radiograph before ordering anything fancy. A CSA above 35° should raise your suspicion for a rotator cuff tear; below 30° points you toward glenohumeral osteoarthritis. This is a two-second measurement that helps you predict which pathology you are dealing with.
The practical trap this paper closes is the instinct to trust MRI for bony angles. MRI reads the CSA off separate oblique slices, and in arthritic shoulders osteophytes and fat suppression blur the glenoid, so MRI falsely pushes OA values above the 30° threshold. Measure the CSA on plain film, not MRI.
Remember the CSA reflects deltoid force direction: high angle drives superior shear on the cuff, low angle drives joint compression. It predicts the type of disease, not the tear size, so use it as a screening and mechanistic tool, not a severity grade.
This study tests whether the critical shoulder angle (CSA) separates patients with rotator cuff tears from those with glenohumeral osteoarthritis and controls. It also compares how reliably the CSA can be measured on radiographs versus MRI. Three age-matched groups of 10 patients each were measured by three independent observers.
When you evaluate a shoulder pain patient, look at the CSA on a true AP radiograph before ordering anything fancy. A CSA above 35° should raise your suspicion for a rotator cuff tear; below 30° points you toward glenohumeral osteoarthritis. This is a two-second measurement that helps you predict which pathology you are dealing with.
The practical trap this paper closes is the instinct to trust MRI for bony angles. MRI reads the CSA off separate oblique slices, and in arthritic shoulders osteophytes and fat suppression blur the glenoid, so MRI falsely pushes OA values above the 30° threshold. Measure the CSA on plain film, not MRI.
Remember the CSA reflects deltoid force direction: high angle drives superior shear on the cuff, low angle drives joint compression. It predicts the type of disease, not the tear size, so use it as a screening and mechanistic tool, not a severity grade.