The primary reason to make a shoulder x-ray is to confirm or exclude the presence of a fracture. Additionally, the image can provide information on the position of the shoulder joint, any bone abnormalities (including bone tumors) and soft tissue disorders (think of calcifications in the rotator cuff muscles). Many hospitals have their own protocol for shoulder imaging.
A standard image normally includes an anteroposterior (AP) image (fig 1). It can be made either in endorotation or in exorotation.
Figure 1. Anteroposterior (AP) image. a. Positioning. b. Image in endorotation. c. Image in exorotation.
Options then include a Y image (= scapulolateral image), an axialimage (arm in 30-degree abduction), and an apical oblique image (AP image where the beam is aimed 45 degrees craniocaudal).
Figure 2. Positioning (a) in a Y image (b).
Figure 3. Positioning (a) in an axial image (b).
Figure 4. Positioning (a) in an apical oblique image (b).
Each image has benefits and drawbacks. Axial (fig. 3) and Y images (fig. 2) effectively detect luxations. In the axial direction, the glenoid and humeral head can also be accurately assessed. A significant drawback is the abduction the patient must make (particularly for the axial image), which may be painful in a trauma setting. The Y image may be less painful, but the small glenoid/humeral head fragments may be missed. The benefit of the apical oblique image (fig. 4) is that the Hills-Sach lesions and glenoid fractures are reliably detected (see Luxations section). Additionally, patients generally find this image non-painful.
Acromioclavicular (AC) image
The AC joint is imaged from anterior to posterior. The beam is aimed caudocranial and may vary from 10-15° to 30-45° (fig. 5).
Figure 5. Positioning (a) in a 10-degrees acromioclavicular (AC) image (b).