Bony Anatomy
- The scapula is a mostly flat, roughly triangular-shaped bone that is suspended off the posterolateral chest wall through the acromioclavicular articulation.
- The scapular spine arises from the upper posterior surface and gives rise superolaterally and anteriorly to the acromion.
- The coracoid process arises from the anterosuperior scapular neck. It runs in a superomedial direction before turning lateral and anterior as it thins at its “beak.”
- The glenoid face is nearly perpendicular to the scapular body and forms the medial side of the glenohumeral articulation. Average glenoid version ranges from 5 degrees of anteversion to 15 degrees of retroversion.
- A majority of the scapular body bony surface area is only a few millimeters thick, limiting fixation constructs to the peripheral borders, scapular spine, glenoid neck, and coracoid.
- Imaging of the scapular body is complicated by the overlying thoracic wall and spine, while the acromion is difficult to image because of the overlying distal clavicle.
- Because of the complex anatomy and overlying structures, scapular fractures are easily missed or underestimated by plain radiographs.
Radiographic Anatomy
AP and Grashey AP View
- In the AP view, the glenohumeral articulation should be seen free from overlying structures, but the scapular body invariably overlies the thoracic wall, including the ribs and the lung fields. The medial border and inferior angle of the scapula should be included on the radiograph.
- Minimally displaced scapular body fractures, particularly over the medial half of the scapula, are difficult to appreciate secondary to overlying structures (Fig. 2-1A and B).
Figure 2-1 Suboptimal technique and overlying structures resulted in a missed diagnosis of a medial scapular body fracture (arrows). This injury was recognized on subsequent CT scan as part of a trauma protocol.
- To best visualize the glenohumeral joint, the beam should be rotated approximately 35 degrees aiming from the midline to lateral in order to profile the scapula, in line with the glenoid, generating a Grashey or “True AP” view (Figs. 2-2 and 2-3).
Figure 2-2 The AP view fails to demonstrate the scapula body en fasse and exposes the surface of the glenoid fossa (orange). Note the orientation of the coracoid process (yellow).
Figure 2-3 Note the difference in orientation of the glenoid (orange) in profile and the coracoid process (yellow), as well as their radiographic representation with a Grashey AP view.
- Due to the slightly concave nature of the glenoid surface, the Grashey view allows confirmation that screws do not protrude into the glenohumeral joint (Fig. 2-4).
Figure 2-4
- The Grashey view is often best to ensure reduction of fracture fragments with spikes that exit the lateral border of the scapula. These fragments often have extension into the glenoid face, and articular reduction can be partially assessed with this view (Fig. 2-5A and B).
Figure 2-5
- The lateral and posterior displacement of the caudal fracture fragment can be due to the pull of the infraspinatus, teres major and minor, the latissimus dorsi, and the long head of the triceps, depending on the size of the fracture fragment.
- Overlying structures may obscure bony anatomy on the Grashey view, particularly toward the medial half of the scapula.
Lateral View (Scapular Y View)
- The humeral head should remain centralized within the bony “Y” formed from the confluence of the scapular spine (posteriorly), coracoid (anteriorly), and scapular body (inferiorly).
- From this sagittal profile, fractures of the scapular body, spine, acromion, and coracoid base can be visualized.
- The lateral view can appreciate the degree of scapular sagittal plane fracture displacement (Fig. 2-6A and B).
Figure 2-6
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