Wrist (horizontal beam lateral view)
The horizontal beam lateral wrist view is a modified lateral projection when performing the three view series of the wrist and carpal bones in trauma. It is the orthogonal projection of the PA wrist without any patient movement, making it the most appropriate projection for patients in pain.
- patient is supine
- affected arm is placed by the patient's side on a pillow or foam block
- image receptor is placed leaning against the aforementioned foam block or pillow with the long axis of the image receptor in line with the long axis of the affected limb
- lateral projection
- the ulnar aspect of the mid carpal region
- anteroposterior to the skin margins
- distal to the mid way up the metacarpals
- proximal to include one quarter of the distal radius and ulna
- 24 cm x 30 cm
- 50-60 kVp
- 3-5 mAs
- 100 cm
Image technical evaluation
The academic rule of a true lateral wrist radiograph is defined by the scaphopisocapitate relationship as “...the palmar context 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”
There is superimposition of the carpal bones, including the distal portion of the scaphoid and the pisiform. The radius and ulna are also superimposed.
The aim of the horizontal beam lateral wrist is to avoid patient movement whilst achieving a diagnostic radiograph that rivals the quality of a walk in patient.
This projection is paramount in the correct diagnosis of wrist fractures and consequently the patient's management.
The tricky part of the projection is keeping the image receptor upright against the foam block during the exam, this is easily aided using towels and sandbags. On occasion the patient may be well enough to help but this is a last resort.
The correct way of explaining this projection is that it is exactly 90° to the PA projection with no patient supination/pronation. It is harder to do but your patient will thank you when they don't have to twist into difficult positions with a broken wrist.