AAOS Comprehensive Orthopaedic Review 4: Print + Ebook (AAOS - American Academy of Orthopaedic Surgeons)

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72 | Imaging of the Shoulder and Elbow

TABLE 1 Special Radiographic Views of the Shoulder View Indication Technique Serendipity Sternoclavicular joint

With patient supine, 40° cephalic tilt view centered on sternum

West Point

Anterior glenoid bone loss

Patient is prone with the involved shoulder raised above table level Centered on axilla with beam directed 25° downward and 25° medial AP with 10° cephalic tilt centered over acromioclavicular joint Patient position is supine Only one-half the voltage of a routine shoulder AP view (soft-tissue view) should be used With patient supine, the affected arm is placed on the top of the head with the fingers toward the back of the head; the beam is centered over the coracoid process with 10° cephalic tilt Patient is seated; cassette is placed posterior and parallel to the spine of the scap ula; the beam is directed 45° to the plane of the thorax and 45° caudally Patient is seated; cassette is placed on the table behind the patient and patient leans back 30° with the beam straight up and down from superior to inferior

Zanca

Acromioclavicular joint

Stryker notch Evaluate Hill-Sachs lesion after dislocation

Apical oblique Evaluate for glenoid rim fracture in instability

Velpeau

Evaluate glenohumeral alignment in posttrau matic, painful shoulder

d. The critical shoulder angle is normally 30° to 35°. Increased values are considered a risk factor for rotator cuff tears and decreased values are associated with glenohumeral osteoarthritis. 1. Indications a. Glenoid bone loss: CT with three-dimensional reconstructions is the advanced imaging study of choice for determining the extent of glenoid bone loss in the setting of shoulder instability ( Figure 1 ). b. Glenoid version: CT with three-dimensional reconstructions is the preferred modality for determining version and assessing glenoid bone stock. Three-dimensional reconstruc tion has been shown to be more accurate than two-dimensional imaging for assess ing glenoid version. Numerous preoperative planning tools have been developed using CT data for dealing with difficult glenoid recon struction cases. c. Fractures: CT can be used to further evaluate complex fractures of the proximal humerus and glenoid to identify fracture patterns and quantify fragment displacement, which may affect treatment decisions ( Figure 2 ). CT does not consistently improve the reliability of the Neer classification system. d. Soft-tissue pathology: The use of CT is typi cally reserved for patients who are unable to undergo MRI. Nonarthrographic CT is useful

in evaluating the rotator cuff musculature and can demonstrate muscle atrophy and fatty infiltration that are seen in chronic rotator cuff disease. CT arthrography can be used to detect full-thickness rotator cuff tears or assess rota tor cuff healing after repair. CT arthrogram

6 | Shoulder and Elbow

B. CT

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Figure 1 Three-dimensional sagittal CT image of the shoul der shows anterior glenoid bone deficiency in the setting of shoulder instability.

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AAOS Comprehensive Orthopaedic Review 4