11/13/24, 7\:34 PM Guide | Shoulder x-ray interpretation

Shoulder x-ray interpretation

Table of contents

Introduction

Shoulder X-rays are common investigations in every Emergency Department, typically in the context of trauma, with shoulder
dislocations being the most common pathology.
An important distinction to note is what we mean when we request a “shoulder X-ray”
. In most clinical scenarios this refers to a
radiograph of the glenohumeral joint. However, for the purposes of this guide, we will also include the clavicle and the
acromioclavicular joint in order to form a more complete “shoulder girdle X-ray” interpretation guide.

Con

Begin by con
Patient details (name, date of birth, unique identi
Date and time the radiograph was taken
If previous radiographs are available, these should also be reviewed to provide a point of reference. This is especially important
in the context of dislocations, where a history of recurrent dislocation may indicate the need for operative intervention.

Acquire all necessary views

Ideally, a shoulder radiograph series will provide adequate views of the clavicle, acromioclavicular joint (ACJ), glenohumeral
joint (GHJ) and the scapula. However, it is worth being aware that if you are unable to get an adequate view of the clavicle or the
scapula, more speci
views are required will largely be dictated by the patient’s history and the
Typical shoulder X-ray views include\:
Antero-posterior (AP) view
Lateral/scapula Y view (named due to the “Y” shape of the scapula in this view)
An axial view can also be used as an alternative to the scapula Y view if the patient is unable to tolerate the positioning
required to obtain this view.
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Figure 1. A normal AP view [1]

Interpretation

A structured approach to shoulder X-ray interpretation is discussed below.

Adequacy

Check the radiograph’s adequacy to ensure you are able to clearly see all relevant structures.

Alignment

Given that the most common reason a shoulder X-ray is requested is to look for dislocation or successful subsequent
relocation, being familiar with alignment is arguably the most important part of shoulder X-ray interpretation.
AP view
“ball”).
When looking at the GHJ, the glenoid fossa (the “socket”) should be visible as a concavity medial to the humeral head (the
Scapular Y/lateral view
The humeral head lies on top of the glenoid fossa, with the coracoid process anterior to it (the side of the ribcage represents
anterior in this view).
Anterior shoulder dislocation
Anterior shoulder dislocation is signi
dislocations.
Typical X-ray
AP view\: the humeral head will lie medial and inferior to the glenoid fossa.
Lateral view\: the humeral head will lie anterior and inferior to the glenoid fossa.
The humeral head will also lie inferior to the coracoid process and this is typically most obvious in the lateral view.
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Figure 3. AP view of anterior shoulder dislocation [3]
Posterior shoulder dislocation
Posterior shoulder dislocation is both signi
previously mentioned, if X-ray
imaging modality (e.g. CT).
Typical X-ray
AP view\: the glenohumeral joint will be widened and the humeral head will take on a classic “light bulb” appearance due to
forced internal rotation of the humerus.
Lateral view\: the humeral head will lie posterior to the glenoid fossa.
Figure 5. AP view of posterior shoulder dislocation [5]
Acromioclavicular joint dislocation
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The AC joint is visible in all views and is probably best assessed in the AP view. In this view, you should see the inferior borders
of the acromion and the clavicle line up in a healthy individual.
If they don’t, you should look closely at the distance between\:
the acromion and the clavicle
the clavicle and the coracoid process
Widening of the gap between the acromion and clavicle may indicate pathology a
a tear).
Widening of the gap between the clavicle and the coracoid process may indicate pathology a
ligament (e.g. a tear).
Figure 6. AP view of acromioclavicular joint dislocation [6]
A note on “normal” distances
When assessing for joint disruption (especially AC joint) you will need to be familiar with commonly measured distances
at the shoulder joint.
7
The acromioclavicular distance should be between 5-8mm\:
>8mm = injury to the acromioclavicular ligament
The coracoclavicular distance should be between 11-13mm\:
>13mm = injury to the coracoclavicular ligament
The acromiohumeral distance should be between 7-12mm\:
\<7mm = possible supraspinatus tendon tear (a common rotator cu
>12mm = joint widening (e.g. due to e
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Figure 7. AP view of a normal acromioclavicular joint with yellow lines to illustrate the alignment of the inferior aspect of the acromion process and distal
clavicle, and green lines to indicate acromioclavicular (1), coracoclavicular (2) and acromiohumeral (3) distances8. The projection of this image is
suboptimal and makes the acromiohumeral distance slightly harder to see. Figure 1 of the normal AP shoulder demonstrates this distance more clearly
[7]

Bones

In all views, follow the outline of the cortex (outer white edge) of each bone, not forgetting to look at the ribs as well. This is
doubly true in the context of trauma, as rib fractures and the subsequent complications may be missed by a distracting injury
like a fractured humerus or dislocated shoulder. As with all radiographs, make sure you don’t stop looking once you have found
a fracture or the speci
doesn’t rule out the possibility of other bony injuries). This can sometimes be di
prevented by being thorough and having a framework or system to follow.
Figure 8. AP view XR with clavicle fracture [9]
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Soft tissue

Look around the bones and joints for any signs of darkening/
which suggests a fracture even if one cannot be seen.
You can also sometimes see calci
impingement (although this is unlikely to be the reason for a shoulder X-ray request in an Emergency Department setting).
Figure 10. Calci

Review areas

Even though you requested a shoulder X-ray, due to the nature of the imaging technique you will be given an image that
contains more than just the shoulder girdle. It is incredibly easy to get “tunnel vision” and focus entirely on the shoulder.
Special care should be taken to review the rest of the radiograph, especially the lungs and the ribs, as well as any other areas
included in the image. In the context of trauma, rib fractures and pneumothoraces are common and may not be noticed if the
patient’s main complaint is shoulder pain.
Although much less common, it is also important to check the lungs for malignancy, as a Pancoast tumour may be visible in the
apex of the lung.
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