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- See:
      - Infraspinatus: primary external rotator of humerus;
      - Posteior Deltoid
      - Teres Minor

- Discussion:
    - the posterior rotator cuff is important for maintenance of necessary force couples in axial (transverse) and coronal planes.
    - preoperative muscle testing of the external rotators is  a valid means of assessing posterior cuff;
   - maintenance of external rotation strength tend to have intact infraspinatus & teres minor, even though top of humeral head may be uncovered