Procedures · Upper Extremity

Humerus Positioning Series

Compare the AP and rotational lateral projections of the routine humerus series.

humerus · AP

Right

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The routine humerus series

The projections this region is examined with. Set them up yourself in Practice positioning.

AP humerus

Anteroposterior projection · arm extended, hand supinated

Demonstrates: The entire humerus on one image, including both the shoulder and the elbow joint. At the proximal end a true frontal projection shows the greater tubercle in profile on the lateral side and the humeral head partly in profile medially, with the glenoid cavity barely overlapping it. At the distal end both the medial and the lateral epicondyle are thrown into profile.
Part position: Erect or supine, with the body rotated toward the affected side as far as it takes to bring the shoulder and proximal humerus into contact with the cassette. The humerus is aligned with the long axis of the receptor, and the receptor height is set so that the shoulder and elbow joints sit the same distance from its two ends. The hand and forearm are extended as far as the patient can tolerate, the arm is abducted slightly, and the hand is gently supinated until the epicondyles are parallel to the receptor and the same distance from it.
Central ray: 90° to the image receptor, centered to the midpoint of the humerus.
Why it is positioned this way: Two adjustments build this projection and they are independent of each other. Supinating the hand is what levels the epicondyles, and that is a check you make with your fingers rather than your eyes: palpate both and confirm they are the same distance from the receptor. When they are, the beam meets them edge-on and throws both into profile, which is the whole test for rotation at the distal end. It matters because pronating instead rolls the radius across the ulna and turns the humerus in with it, so the shoulder quietly becomes an oblique and the greater tubercle slides off the lateral margin. Rotating the BODY toward the affected side is the second adjustment, and it does something different — it closes the gap between the shoulder and the receptor, so the proximal humerus is not magnified and blurred while the elbow, lying flat, is sharp.

Also covered by this projection

Both joints on one imageThe receptor goes portrait and has to be long enough for the whole bone, because the projection is not finished unless the shoulder and the elbow are both on it. On a tall patient a 14 × 17 inch receptor may need to be placed diagonally to catch both. Collimate on the sides to the soft tissue of the humerus and shoulder, and let the lower border take in the elbow joint plus at least an inch — 2.5 cm — of the proximal radius and ulna.

Do not rotate an arm that may be brokenSupinating the hand means turning the whole humerus, and that is exactly what a fractured or dislocated humerus must not do. If either is suspected, leave the arm as it lies and get the second projection with a horizontal beam instead — the trauma lateral for the mid and distal shaft, or the transthoracic lateral for the proximal end. Both are alternates to the rotational lateral on the next tab, not additions to the routine.

Rotational lateral humerus

Lateromedial or mediolateral projection · arm internally rotated until the epicondyles sit at 90° to the receptor

Demonstrates: A lateral of the entire humerus, again with both joints on the image. A true lateral announces itself at the distal end, where the two epicondyles land directly on top of one another instead of side by side. At the proximal end the lesser tubercle has come round into profile on the medial side, where the lower part of the glenoid cavity partly covers it.
Part position: For the lateromedial, erect with the back to the receptor and the elbow partially flexed, the body rotated toward the affected side as far as it takes to bring the humerus and shoulder into contact with the cassette, and the arm then rotated inward until the epicondyles stand at 90° to the receptor. For the mediolateral, the patient instead faces the receptor and is obliqued 20° to 30° round from a PA, with the elbow flexed 90°, which is what brings the humerus into close contact from that side. Either way the receptor height is set so the shoulder and elbow joints sit the same distance from its two ends.
Central ray: 90° to the image receptor, centered to the midpoint of the humerus.
Why it is positioned this way: Compare this tab with the AP and notice what has not changed: the tube. The central ray sits at 90° to the receptor and enters the same point on the arm in both projections, and the scapula behind it has not shifted at all. Everything different about this image comes from the arm having turned a quarter of a circle inward, which is why the projection is called a ROTATIONAL lateral — you make the lateral by rotating the part, not by moving the equipment. Follow what that quarter-turn does. The line between the epicondyles starts out lying flat along the receptor, and turning the arm stands it up on end until it runs straight down the beam; once it does, the two epicondyles are one behind the other and project on top of each other. The same movement carries the lesser tubercle, which faces forward when the hand is supinated, round to face inward, where it lands over the bottom of the glenoid cavity — and it swings the greater tubercle off the lateral margin round to face the tube. So the two tubercles are the fastest way to read which projection you are looking at: greater tubercle on the outer edge means AP, lesser tubercle on the inner edge means lateral.

Also covered by this projection

Lateromedial or mediolateral — same arm, opposite sidesThe routine names both and either will do. With the back to the receptor and the arm rotated inward, the outer surface of the arm ends up facing the tube, so the beam runs from the lateral side through to the medial one. Turn the patient round to face the receptor and oblique 20° to 30° from a PA, and the beam runs the other way, entering medially and leaving laterally. The arm is in the same position for both; what changes is which side the tube is on, and therefore which of the two names the projection gets.

What the elbow is doingFlex the elbow for this projection — partially for the lateromedial, and to 90° for the mediolateral — because that is what lets the arm lie comfortably against the receptor. Nothing you are graded on depends on the angle: both checks for a true lateral are the epicondyles stacking and the lesser tubercle coming into profile, and the elbow changes neither.

When the arm must not be turnedThis projection is built entirely out of rotating the humerus, so it is off the table the moment a fracture or dislocation is suspected. Use a horizontal beam instead and leave the arm alone: the trauma lateral covers the mid and distal shaft, and the transthoracic lateral covers the proximal humerus by shooting through the opposite side of the chest. Both are ways of getting a lateral without asking the injured bone to move.

Procedures lessonShoulder girdle