From the Guidelines
To read a shoulder X-ray for dislocation, it is essential to examine multiple views, including anteroposterior (AP) in internal and external rotation, axillary lateral, and scapular Y views, as recommended by the most recent guidelines 1. When evaluating a shoulder X-ray for dislocation, first examine the glenohumeral joint where the humeral head should sit centered in the glenoid fossa. Look for abnormal positioning of the humeral head relative to the glenoid - anterior dislocations (most common) show the humeral head displaced forward and medially, posterior dislocations show displacement backward, and inferior dislocations show downward displacement. Some key points to consider when reading a shoulder X-ray for dislocation include:
- Comparing the alignment with the contralateral shoulder if available
- Checking for associated findings like Hill-Sachs lesions (compression fracture on the posterolateral humeral head) in anterior dislocations or reverse Hill-Sachs lesions in posterior dislocations
- Looking for Bankart lesions (avulsion of the anterior-inferior labrum) and fractures of the greater tuberosity
- Understanding that the axillary view is particularly important as it shows the relationship between the humeral head and glenoid in the axial plane, and the scapular Y view helps distinguish anterior from posterior dislocations by showing the humeral head position relative to the "Y" formed by the scapular body, acromion, and coracoid process, as noted in 1 and further emphasized in 1. The importance of using multiple views is highlighted by the fact that acromioclavicular and glenohumeral dislocations can be misclassified on AP views alone 1. Additionally, radiography should be performed upright because malalignment of the shoulder can be underrepresented on supine radiography 1.
From the Research
Reading a Shoulder X-ray for Dislocation
To read a shoulder X-ray for dislocation, it is essential to understand the anatomy and mechanism of dislocation of the shoulder, as discussed in 2. The evaluation of a shoulder X-ray involves identifying osseous abnormalities and determining the direction of instability.
- Key factors to consider when reading a shoulder X-ray include:
- Detection of Hill-Sachs lesions, which are often visible in antero-inferior instability 3
- Identification of Bankart lesions, which can be more difficult to detect on conventional radiography 3
- Use of special views, such as the Garth view, to detect antero-inferior instability impaction fractures at both the humeral and glenoid sides 3
- The radiographic evaluation of the dislocated shoulder can be aided by special views, as presented in 2, which can help demonstrate acute and previous shoulder dislocations.
- An understanding of the intricate network of bony, ligamentous, muscular, and neurovascular anatomy of the shoulder, as discussed in 4, is required to properly identify and diagnose shoulder pathology, including dislocation.
- Advanced cross-sectional imaging techniques may be necessary for accurate quantification of bony abnormalities and detection of lesions to the soft-tissue stabilizers of the shoulder, as noted in 3.