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- See:
      - Anterior Dislocation
      - Posterior Dislocations:

- Discussion:
    - note: w/ true AP of shoulder there should be no overlap of the humerus over the glenoid;

- Greater Tuberosity and Acromio Humeral Interval;
    - AP in ext. rot. brings greater tuberosity into clear prominence;
    - this x-ray taken w/ pts arm at side, hand supinated, & elbow extended;
    - gives good visualization of the greater tuberosity;
    - measurement of the acromiohumeral interval also can be done more accurately on the external rotation view;

- Calcific Tendonitis:
    - AP w/ arm in internal rotation is taken with the arm at the side, elbow extended, and the forearm pronated;
    - may also be helpful in calcific tendinitis, esp in the supraspinatus;

- AC Joint View: (see AC joint)
    - AP w/ arm in 100 deg of abduction provides best view of AC joint;
    - this projection allows the AC joint to clear the overlying scapular or acromial neck, so degeneration or osteophytes can be seen better;
    - this view is a useful one in pts with true adhesive capsulitis;

- Technique:
    - taken w/ pt's back flat on cassette & x-ray beam at right angles to this plane and centered on the shoulder;
    - the scapula sits obliquely on the chest wall, and the glenoid surface is tilted approx. 35 to 40 deg anteriorly;
    - the posterior aspect of the affect shoulder is placed up against the x-ray plate & opposite shoulder is rotated out approx. 40 deg;
    - angled AP radiograph (body turned 35-40 toward cassette), shows glenoid fossa in profile

- Note Neck Shaft angle:
    - angle created at intersection of lines that are perpendicular to anatomic neck and parallel to shaft of humerus;
    - avg angle 143 deg (134 to 166) - angle is less in external rotation and angle is more in internal rotation