Trauma X-ray - Upper limb
Wrist

The standard wrist views are Posterior-Anterior (PA) and Lateral. In certain circumstances further views are helpful so that the 8 overlapping bones are more easily seen.

The wrist comprises the scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate and hamate bones. The radiocarpal, distal radioulnar and carpometacarpal joints can also be considered part of the wrist.

When assessing the wrist it is important to assess the bones and the joint spaces separating them.

Scaphoid fractures

The scaphoid bone is the most commonly fractured wrist bone. X-rays are indicated if there is post-traumatic wrist pain with 'anatomical snuff box' tenderness. In this case 2 extra views are added to the standard views (oblique, and PA with ulnar deviation).

Despite these additional views 30% of scaphoid fractures remain occult on any image taken at the time of injury. The long-term consequences of not treating a scaphoid fracture can be significant. There is a high risk of non-union, with or without avascular necrosis of the proximal fracture component. It is therefore essential that patients clinically suspected to have a scaphoid fracture are treated as such, even if a fracture is not visible on the X-ray. These patients should then be followed up clinically with repeat X-rays if still tender.

In many departments MRI is performed if there is persistent pain/tenderness with no visible fracture on X-ray at 10 days. Local protocols must be adhered to.

This is a classic exemplum of 'TREAT THE PATIENT AND NOT THE X-RAY.'

Triquetrum fracture

Triquetrum fractures are often only seen on the lateral image. Soft tissue swelling can provide an important clue to the presence of fractures such as this, or elsewhere in the wrist.

Hamate fracture

If a carpal bone injury is suspected and not visible on the PA or lateral image, then a request for other views can be made. For example, a hamate fracture is often poorly visualised on the standard views and may be best seen on an oblique view. Like many other carpal injuries this fracture can have significant long term clinical consequences if not identified.

Wrist joints

There are numerous joints of the wrist, named according to their relative bones. These joints should be uniform in width and similar to that of the carpometacarpal, radiocarpal, and distal radioulnar joints.

Scapholunate ligament injury

The most commonly injured carpal ligament is the scapholunate ligament. Tearing of this ligament results in widening of the scapholunate space to greater than 2mm on an X-ray, or such that it is obviously wider than the other intercarpal spaces. This injury is best seen when the wrist is stressed in ulnar deviation.

If scapholunate ligament injury is suspected then orthopaedic/hand surgeon referral is required.

Carpal dislocation

The most common dislocations of the wrist involve the lunate.

'Lunate dislocation' is a term used to describe dislocation of the lunate from the radius, usually with accompanying dislocation of the capitate from the lunate.

'Peri-lunate dislocation' is a term used to describe dislocation of the capitate from the lunate.