Procedures · Upper Extremity

Hand Positioning Series

Explore the hand's anatomy, then use Practice mode to position the PA, oblique, and lateral projections yourself.

hand · Extended

Right

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The routine hand series

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

PA hand

Posteroanterior projection · hand pronated

Demonstrates: The whole hand and wrist plus about an inch of distal forearm, with the metacarpophalangeal and interphalangeal joint spaces open. The thumb is the exception: because it sits rotated about 90 degrees to the other digits, a PA of the hand gives an OBLIQUE of the thumb, never a true PA of it.
Part position: Seated at the end of the table with the hand and forearm extended. The hand is pronated with the palmar surface in contact with the image receptor and the fingers spread slightly, and the long axis of the hand and forearm is aligned with the long axis of the receptor.
Central ray: 90° to the image receptor, centered to the third metacarpophalangeal joint.
Why it is positioned this way: Pronating the hand flat is what puts the phalanges parallel to the receptor, and that parallelism is the whole reason the joint spaces open — a beam that meets a joint at an angle projects the two bone ends over each other instead of through the gap. Spreading the digits keeps their soft tissues from overlapping. The thumb cannot be fixed by this position: its own plane sits at roughly 90° to the palm, so it is obliqued here by anatomy, which is why a thumb injury gets its own projection rather than being read off the hand.

Also covered by this projection

AP handThe hand supinated instead of pronated. It is not the routine, because the digits then sit further from the receptor and the joint spaces suffer, but it is what a patient who cannot pronate gets.

PA oblique hand (45° lateral rotation)

PA oblique projection · lateral rotation 45°

Demonstrates: The metacarpals and phalanges turned off the true frontal, so a fracture line hidden by superimposition on the PA is thrown into profile. The midshafts of the metacarpals stay separate while their distal heads begin to overlap.
Part position: Seated at the end of the table as for the PA, hand pronated on the receptor, then the entire hand and wrist rotated laterally 45 degrees so the thumb side lifts and the ulnar side stays down. A radiolucent wedge or step block supports the digits so they stay separated and parallel to the receptor.
Central ray: 90° to the image receptor, centered to the third metacarpophalangeal joint.
Why it is positioned this way: The support block is the part that is easy to skip and it is doing real work. Rotated 45 degrees with nothing under them, the fingers sag away from the receptor and are no longer parallel to it, so their joint spaces close and the midphalanges foreshorten — The unsupported version is an option only for the METACARPALS, and it is not recommended when the digits are the point. Rotation without support trades one hidden fracture for another.

Also covered by this projection

Oblique for the metacarpals (digits not parallel)The same 45 degree rotation with the digits left unsupported and flexed. It is acceptable when the metacarpals are what is being examined, and not recommended when the digits are, because the phalanges foreshorten and their joint spaces close.

“Fan” lateral hand (lateromedial)

Lateromedial projection · thumb side up, digits fanned

Demonstrates: The hand in true lateral, with the metacarpals superimposed on one another and the distal radius and ulna superimposed — while each finger, fanned away from its neighbours, is seen in its own lateral profile with its joint spaces open. The thumb is projected free of the rest of the hand.
Part position: Seated at the end of the table with the long axis of the hand aligned with the receptor, then the hand and wrist rotated into the lateral position with the thumb side up. The thumb and index finger are brought together tip to tip, and the remaining three fingers fanned out and separated beneath them, each digit supported on a radiolucent block — so that every digit is separated while the metacarpals stay unrotated in true lateral.
Central ray: 90° to the image receptor, centered to the second metacarpophalangeal joint.
Why it is positioned this way: This projection has to satisfy two demands that pull against each other. Superimposed metacarpals are what proves the hand is truly lateral, so the metacarpals must not rotate. But four fingers stacked on top of each other in that same position are unreadable. Fanning the digits answers the second demand without disturbing the first, because the fan happens at the finger joints while the metacarpals hold still — which is exactly why each digit needs its own support rather than being left to drop.

Also covered by this projection

Lateral in extensionThe same true lateral with the fingers and thumb extended and superimposed on one another rather than fanned. It is the alternative used to localise a foreign body, where superimposing the digits is the point rather than the problem.

Lateral in flexionThe same true lateral with the fingers in a natural flexed position and the thumb lightly touching the index finger. It shows anterior or posterior displaced metacarpal fractures and is often less painful for an injured patient.

Procedures lessonHand & wrist