When performing an AP projection of the humerus how far above the level of the shoulder should the top of the IR be placed?

Citation, DOI & article data

Citation:

Murphy, A. Shoulder (AP view). Reference article, Radiopaedia.org. (accessed on 08 Sep 2022) https://doi.org/10.53347/rID-45849

The shoulder AP view is a standard projection that makes up the two view shoulder series. The projection demonstrates the shoulder in its natural anatomical position allowing for adequate radiographic examination of the entire clavicle and scapula, as well as the glenohumeral, acromioclavicular and sternoclavicular joints of the shoulder girdle. 

On this page:

This view helps in visualizing potential fractures or dislocations to the proximal humerus and shoulder girdle in a trauma setting. Additionally, this view is useful in assessing for degenerative diseases which may be seen as calcium deposits in bursal structures, muscles or tendons around the shoulder.

• patient is preferably erect
• midcoronal plane of the patient is parallel to the image receptor, in other words, the patient's back is against the image receptor
• glenohumeral joint of the affected side is at the center of the image receptor
• affected arm is in a neutral position by the patient side
• the patient is slightly rotated 5-10° toward the affected side. Therefore, the body of the scapula is laying parallel with the image receptor

• anteroposterior projection
• centering point
  • 2.5 cm inferior to the coracoid process, or 2 cm inferior to the lateral clavicle at the level of the glenohumeral joint
• collimation
  • superior to the skin margins
  • inferior to include one-third of the proximal humerus
  • lateral to include the skin margin
  • medial to include the sternoclavicular joint
• orientation  
  • landscape
• detector size
  • 24 cm x 30 cm
• exposure
  • 60-70 kVp
  • 10-18 mAs
• SID
  • 100 cm
• grid
  • yes (this can vary departmentally)

• the entire clavicle is visualized alongside the glenoid cavity and scapula in the AP position
• a slight overlap of the humeral head with the glenoid
• no foreshortening of the scapular body (as per the patient rotation discussed in the positioning)

The technical factors of this examination are not particularly demanding, and there is not much room for positioning error other than over or under rotation to compensate for the scapular body.

An open glenohumeral joint is a sign of over rotation toward the affected side. This results in a more AP glenoid view, and although diagnostically relevant to shoulder pathology, it is not an accurate representation of the surrounding structures.

References

Related articles: Imaging in practice

Promoted articles (advertising)

When performing an AP projection of the humerus how far above the level of the shoulder should the top of the image receptor be placed?

When performing AP projections of the shoulder the central ray should be directed?

Where is the central ray directed for an AP projection of the humerus?

Where should the center of the IR be positioned for a lateral projection of the shoulder?