The Critical Shoulder Angle combines three anatomic parts: glenoid inclination, lateral acromial roof extension, and acromial height. This study broke the CSA into those parts to find which one best separates rotator cuff tears from concentric osteoarthritis. It compared 70 shoulders with degenerative cuff tears against 54 with concentric OA using radiographs and CT.
When you measure a CSA and it is high, the reason is mostly how far the acromion extends laterally, not how the glenoid is tilted. That matters because surgeons are already doing arthroscopic lateral acromioplasty to lower a high CSA and reduce recurrent cuff tears. This paper gives anatomic support for correcting the lateral acromial roof rather than trying to alter glenoid inclination.
Remember the direction: high CSA (>35-38°) with large lateral acromial coverage points toward rotator cuff disease, while low CSA (<28-30°) points toward concentric OA. The two conditions have opposite anatomic profiles, which is why they rarely coexist early.
One caution the authors are clear about: this is a comparison of two disease groups with no normal controls, and it does not prove acromioplasty works. It tells you which sub-component matters, not that shaving it changes outcomes.
The Critical Shoulder Angle combines three anatomic parts: glenoid inclination, lateral acromial roof extension, and acromial height. This study broke the CSA into those parts to find which one best separates rotator cuff tears from concentric osteoarthritis. It compared 70 shoulders with degenerative cuff tears against 54 with concentric OA using radiographs and CT.
When you measure a CSA and it is high, the reason is mostly how far the acromion extends laterally, not how the glenoid is tilted. That matters because surgeons are already doing arthroscopic lateral acromioplasty to lower a high CSA and reduce recurrent cuff tears. This paper gives anatomic support for correcting the lateral acromial roof rather than trying to alter glenoid inclination.
Remember the direction: high CSA (>35-38°) with large lateral acromial coverage points toward rotator cuff disease, while low CSA (<28-30°) points toward concentric OA. The two conditions have opposite anatomic profiles, which is why they rarely coexist early.
One caution the authors are clear about: this is a comparison of two disease groups with no normal controls, and it does not prove acromioplasty works. It tells you which sub-component matters, not that shaving it changes outcomes.