What anatomy is demonstrated on the lateral scapular projection when the upper limb is slightly abducted the elbow flexed and the forearm resting on the posterior thorax?

Citation, DOI & article data

Citation:

Murphy, A. Shoulder (lateral scapula view). Reference article, Radiopaedia.org. (accessed on 09 Oct 2022) //doi.org/10.53347/rID-48252

The lateral scapula shoulder or Y view is part of the standard shoulder series.

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Orthogonal to the AP shoulder (note: as is an axillary view); this view is a pertinent projection to assess suspected dislocations, scapula fractures, and degenerative changes. It is also useful in seeing both the coracoid and acromion process in profile.

• erect or sitting, facing the upright detector
• rotated in an anterior oblique position so the anterior portion of the shoulder is touching the upright detector
• the hand is placed on the patient's abdomen with the arm flexed
• degree of anterior rotation can vary from patient to patient
• scapula should be end-on to the upright detector, and this can be done via palpation of the scapula border

• posteroanterior lateral projection
• centering point
  • the level of the glenohumeral joint on the posterior aspect of the patient (5 cm below the top of the shoulder)
  • central to the medial scapula border
• collimation
  • laterally to include the skin margin
  • medially to cover the entirety of the medial scapula
  • superior to the skin margin
  • inferior to the inferior angle of the scapula
• orientation  
  • portrait                        
• detector size
  • 24 x 30 cm
• exposure
  • 60-70 kVp
  • 10-20 mAs
• SID
  • 100 cm
• grid
  • yes

• the scapula is clearly demonstrated in a lateral profile, giving the clear appearance of a ‘Y’
• acromion and the coracoid process form the upper arms of the ‘Y’
• if intact, the humeral head is superimposed at the base of the ‘Y’

The lateral scapula projection can be technically demanding, especially when patients are in pain. An anecdotal method amongst radiographers is to feel for the medial border of the scapula and line it up with the anterior portion of the acromion and x-ray straight down the line.

The idea being, if they are lined up there will be a superimposition of the medial and lateral borders of the scapula and hence a perfect lateral position, although this isn't always the case.

The best defense against positional errors is having a thorough understanding of radiographic anatomy and how it changes positionally when assessing for under/over rotation of the lateral shoulder, assess the borders of the scapula.

Over rotation in this projection refers to the patient's unaffected side sitting too far away from the image receptor, otherwise known as lying ‘too square’ to the detector.

Over-rotation is clearly established as the lateral border of the scapula (significantly thicker than the medial) is projected over the thorax along with the humeral head; to adjust this, rotated the unaffected side towards the image receptor slightly.

Under rotation in this projection refers to the patient's unaffected side sitting too close to the image receptor, otherwise known as lying ‘flat’ to the detector.

The lateral border, as well as the humeral head, will be sitting overly lateral in the image; to fix this, rotated the unaffected side away from the detector to increase obliquity.

Some departments will recommend a 15-degree caudal angle to achieve the ‘perfect’ lateral shoulder; it should be noted this is an entirely different projection known as an ‘outlet projection’ used primarily for the visualization of the supraspinatus outlet; often aiding in the investigation of impingement, spurs and calcifications.

References

Related articles: Imaging in practice

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Citation, DOI & article data

Citation:

Murphy, A. Shoulder (AP view). Reference article, Radiopaedia.org. (accessed on 09 Oct 2022) //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. 

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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

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