The wrist series is comprised of a posteroanterior, oblique, and lateral projection. The series examines the carpal bones (namely, the scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate and hamate). It also examines the radiocarpal joint along with the distal radius and ulna.
Lateral wrist radiograph
The purist definition of a true lateral wrist radiograph is defined by the scaphopisocapitate relationship as “...the palmar cortex of the pisiform should be overlaying the central third of the interval between the palmar cortices of the distal scaphoid pole and the capitate head..." 1.
The anecdotal definition of a lateral wrist is that the distal radius and ulna are superimposed as well as all the carpal bones.
The positioning of a lateral wrist radiograph has a barrage of academia attached to it, the central theme to that being simply that the pronation-supination movement of the wrist from a PA view to lateral does not result in an orthogonal view of the distal radioulnar joint.
Effect of pronation-supination
When the distal radioulnar joint undergoes pronation-supination at the wrist level, the radius can undergo a rotation of up to 180°, yet the ulna will undergo limited to no movement within the arc of a circle. To translate this into everyday terms, isolated rotation at the wrist from the PA position means that the radius moves around a stationary distal ulna, resulting in a lateral view of the distal radius but not the ulna.
Radiographers and clinicians alike should consider this when assessing and requesting a wrist series, respectively: if the ulnar styloid has not changed profile from the PA view to the lateral view, it is not technically an orthogonal view of the PA wrist. As quoted in the Radiology of Emergency Medicine, ‘...one view is no view‘ 2.
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