The Shoulder AP View in Radiology: An Essential Projection for Shoulder Evaluation

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In the field of radiology, the shoulder AP view is a fundamental and standard projection used in the two-view shoulder series. This projection allows for a comprehensive radiographic examination of the entire shoulder girdle, including the clavicle, scapula, glenohumeral joint, acromioclavicular joint, and sternoclavicular joint, all in their natural anatomical positions.

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Indications:The shoulder AP view is particularly valuable in assessing potential fractures or dislocations of the proximal humerus and shoulder girdle in cases of trauma. It is also a useful tool for detecting degenerative diseases, such as calcium deposits in bursal structures, muscles, or tendons around the shoulder.

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Patient Position: To obtain an accurate shoulder AP view, the patient should ideally be in an erect position. The midcoronal plane of the patient should be parallel to the image receptor, meaning their back is against the receptor. The affected glenohumeral joint should be centered on the image receptor, and the patient’s affected arm should be in a neutral position by their side. Additionally, the patient should be slightly rotated about 5-10° towards the affected side to ensure the body of the scapula is parallel to the image receptor.

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Technical Factors: The shoulder AP projection is taken as an anteroposterior (AP) view. The centering point for the X-ray beam should be 2.5 cm inferior to the coracoid process or 2 cm inferior to the lateral clavicle at the level of the glenohumeral joint. Proper collimation is essential to include the relevant structures while avoiding unnecessary exposure to other areas. The exposure settings typically range from 60-70 kVp and 10-18 mAs, and the distance from the X-ray tube to the image receptor (SID) should be 100 cm. A grid may be used to enhance image quality, although its use can vary depending on the department’s protocols.

• 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)

Image Evaluation: When evaluating the resulting image, the entire clavicle should be clearly visualized alongside the glenoid cavity and scapula in the AP position. There should be a slight overlap of the humeral head with the glenoid, indicating correct positioning. Importantly, there should be no foreshortening of the scapular body, which could occur if there was improper patient rotation during positioning.

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Practical Considerations: Performing the shoulder AP view does not require particularly demanding technical factors, and there is limited room for positioning errors, except for over or under rotation to compensate for the scapular body. An open glenohumeral joint on the image can be a sign of over-rotation towards the affected side, leading to an overly anterior view of the glenoid. While this may still be diagnostically useful for shoulder pathologies, it does not accurately represent the surrounding structures.

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In conclusion, the shoulder AP view is a crucial and routine projection used in radiology to assess various shoulder conditions and pathologies. Proper patient positioning and technical accuracy are essential to obtain clear and reliable images for diagnosis and treatment planning. Radiologists and healthcare professionals rely on this view to gain valuable insights into shoulder anatomy and pathology, enabling them to provide the best possible care to their patients.