Procedures · Extremities2 min read5-question check
Shoulder
External rotation profiles the greater tubercle; Grashey opens the glenoid; trauma means no arm rotation.
Patient and part
Erect is preferred. For the AP shoulder in external rotation, supinate the hand so the humeral epicondyles are parallel to the IR. For internal rotation, turn the back of the hand against the thigh so the epicondyles are perpendicular to the IR. Neutral rotation, palm against the thigh, sits in between. For the Grashey method, rotate the patient 35 to 45 degrees toward the affected side, a posterior oblique, so the scapula lies parallel to the IR. For trauma, the scapular Y is a PA oblique with the patient turned 45 to 60 degrees, affected side toward the IR. The transthoracic lateral puts the affected side against the IR with the opposite arm raised over the head.
Central ray
Use 40 inches, about 100 cm. For the AP shoulder, center 1 inch, 2.5 cm, below the coracoid process. For the Grashey, center to the glenohumeral joint, about 2 inches, 5 cm, medial and inferior to the superolateral border of the shoulder. For the scapular Y, center to the scapulohumeral joint. For the transthoracic lateral, center to the surgical neck, angling 10 to 15 degrees cephalad if the patient cannot raise the other arm, and use a breathing technique to blur the ribs and lung markings.
What a good image shows
External rotation shows the greater tubercle in profile on the lateral side, a true AP of the humerus. Internal rotation is a lateral of the humerus and shows the lesser tubercle in profile medially. The Grashey shows the glenoid cavity in profile with an open glenohumeral joint space. On the scapular Y, the scapular body is seen on end, the acromion and coracoid form the arms of the Y, and the humeral head normally sits over the center. An anteriorly dislocated head lies under the coracoid.
Fixing it
A closed joint on a Grashey means wrong body rotation; adjust within 35 to 45 degrees. If the greater tubercle is not in profile on an external rotation view, the arm was not fully rotated. With a suspected fracture or dislocation, never rotate the arm. Take the arm as it lies and add a scapular Y or transthoracic lateral.
Clinical Example
An ED patient holds his arm away from his body after a fall. You take an AP without moving the arm, then a scapular Y. The humeral head sits beneath the coracoid, confirming an anterior dislocation.
Common Mistakes
- Rotating the arm for external and internal views when a fracture is suspected.
- Turning the patient away from the affected side for the Grashey.
- Calling internal rotation a true AP of the humerus; it is a lateral.
Why It Matters
Rotating a fractured humerus can displace fragments. The registry tests which rotation profiles which tubercle and which views to use in trauma.
Key Relationships
- External rotation: greater tubercle in profile laterally
- Internal rotation: lesser tubercle in profile medially
- Grashey: 35 to 45 degree posterior oblique, glenoid in profile
- Suspected fracture: no arm rotation