Wrist x-rays are commonly used for the assessment of the wrist following trauma. This is usually a fall onto an outstretched hand.
It is useful to have a systematic approach; I tend to start proximally and work distally looking at structures on both views together:
- distal radius
- distal ulna
- lateral alignment
- scaphoid and other carpals
Check the contour of the visualised distal radius on the AP and lateral views.
On the AP, the distal radial articular surface should cup the carpals and the most distal portion of the articular surface should be the radial styloid. On the lateral, the radial surface should be smooth. Look for lucent fracture lines traversing the radius.
Distal radial cortical irregularity or a lucent line traversing the metaphysis points towards a distal radial fracture: look for an ulnar styloid avulsion or intra-articular extension.
Check the ulna styloid
Isolated ulnar injuries are not as common as radial injuries. However, trace the cortex of the ulna and ensure that there isn't a small avulsion from the ulnar styloid.
Scaphoid and carpals
The most commonly injured carpal bone is the scaphoid. It is also important because of the risk of avascular necrosis.
Look specifically at the cortex of the scaphoid on all views (most commonly fractured carpal bone) looking specifically for a scaphoid fracture. Trace the cortex of the remaining carpal bones.
On the lateral view, a line drawn through the distal radius, lunate and capitate should be smooth. In a distal radial fracture, this line will help to determine whether there is dorsal or palmar angulation.
The lunate should sit within the cup of the distal radius. The capitate should sit in the cup of the lunate. If there is focal disruption of the line, there has been carpal dislocation (perilunate dislocation or lunate dislocation).
On the AP, the articular surfaces of the carpal rows should form three smooth lines. Trace each of the arcs and ensure that there is a 1-2 mm joint space between each of the carpal bones.
If there is widening of the space between the scaphoid and lunate, think scapholunate dissociation.
The joint space between the distal carpal row and the metacarpals should be visible all the way along. If the metacarpals are sitting over the distal carpal row (e.g. 5th metacarpal over the hamate) think about carpometacarpal dislocation.
Trace each of the bases of the metacarpals. A proximal thumb metacarpal fracture can present with pain of the radial border of the hand and mimic a scaphoid fracture.