Wrist (lateral view)

The lateral wrist view is part of a three view series of the wrist and carpal bones. It is the orthogonal projection of the PA wrist.

Indications

The lateral wrist radiograph is requested for myriad reasons including but not limited to trauma, suspected infective processes, injuries the distal radius and ulna, suspected arthropathy or even suspected foreign bodies. 

What is probably more useful is remembering that a lateral wrist radiograph will not rule out a forearm fracture given the limited coverage (for this, one would request a forearm series).

Patient position

• patient is seated alongside the table
• the affected arm if possible is flexed at 90° so the arm and wrist can rest on the table
• abduct the humerus so that it is parallel to the image receptor
• shoulder, elbow, and wrist should all be in transverse plane, perpendicular to the central beam
• wrist and elbow should be at shoulder height which makes radius and ulna parallel (lowering the arm makes radius cross the ulna and thus relative shortening of radius)

Technical factors

• lateral projection
• centering point: mid carpal region
• collimation
  • anteroposterior to the skin margins
  • distal to the midway up the metacarpals
  • proximal to include one-quarter of the distal radius and ulna
• orientation: portrait
• detector size: 18 cm x 24 cm
• exposure
  • 50-60 kVp
  • 3-5 mAs
• SID: 100 cm
• grid: no

Image technical evaluation

The academic rule of a true lateral wrist radiograph is defined by the pisoscaphocapitate relationship, where the palmar cortex of the pisiform should lie centrally between the anterior surface of the distal pole of the scaphoid and the capitate, ideally in the central third of this interval ¹.

There is a superimposition of the carpal bones, including the distal portion of the scaphoid and the pisiform. The radius and ulna are also superimposed. The ulnar styloid can be seen posterior.

Practical points

The positioning of a lateral wrist radiograph has a barrage of academia attached to it, the central theme to that being, simply 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.

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 the radius moves around a stationary distal ulna, resulting in a lateral view of the distal radius but not the ulna.

To overcome this, it is recommended you abduct the humerus, so the entire forearm is lateral rather than simple pronation-supination at the wrist.

Wrist radiographs are very common in emergency departments, and they are often associated with FOOSH injuries and be quite painful.

Due to the non-urgent nature of a "? Fractured wrist", patients will often be triaged to a lower category and left waiting for longer than multi-trauma patients; an understandable factor in emergency hospitals.

It is important to remember this when examining your patient; it is easy to forget that simply lifting your hand up and placing it on an image receptor could result in substantial pain and more often than not the pain has not been addressed yet. Offer to move things around to assist in positioning, simple things like lowering/raising the table go a long way and result in a better experience for the patient.

It is also possible to achieve the lateral wrist with the patient supine in bed, by simply following the basic positioning principles, the image receptor can be placed next to the patient on the bed under the affected wrist.