---

- Discussion:
    - AC arthritis or AC joint osteophytes can result in impingement and mechanical irritation to the rotator cuff tendons;
    - similar phenomenon can occur after displaced AC separations;
    - greater tuburosity fractures can cause impingement on the rotator cuff if the fragment rotates superiorly;
    - humeral neck fractures that heal in a varus position will cause the greater tuberosity to tilt more superiorly;
- Functional Causes:
    - loss of normal humeral head depression by the rotator cuff tear or weakness from a C5-6 lesion or suprascapular nerve palsy, or biceps tendon rupture