Elbow (acute flexion AP views)

The elbow acute flexion AP views are modified elbow AP projections for patients who cannot straighten their arm for examination. It is comprised of two views demonstrating the distal humerus and proximal forearm structures without distortion.

Indications 

This is a modified projection (chosen by the radiographer when a conventional AP is not possible) for patients who are unable to straighten their arm due to pain. It is often conducted in the context of suspected supracondylar fractures in younger patients, however, can also be utilized in acute elbow imaging following trauma.

Patient position

Distal humerus projection

• the patient is seated alongside the table

• the distal humerus is placed on the image receptor with the arm remaining in flexion 

• the forearm is supported by a sponge 

• if possible the hand is supinated

Proximal forearm projection

• the patient is sat high in relation to the table 

• the patient then places the posterior aspect of the forearm on the IR 

• patient may have to stand for this projection

• ensure the patient's head is turned away as they may tend to lean towards the region of interest

Technical factors

• anteroposterior projection

• centering point

  • distal humerus projection

    • perpendicular to the humerus at the level of the elbow joint 

  • proximal forearm projection

    • perpendicular to the forearm at the level of the elbow joint 

• collimation

  • superior to the distal third of the humerus

  • inferior to include one-third of the proximal radius and ulna

  • lateral to include the skin margin 

  • medial to include medial skin margin 

• orientation  

  • portrait

• detector size

  • 18 cm x 24 cm

• exposure

  • 50-60 kVp

  • 2-5 mAs

• SID

  • 100 cm

• grid

  • no 

Image technical evaluation

• distal humerus projection

  • the distal humerus should demonstrate little signs of distortion, with the proximal forearm structures notably foreshortened and distorted

• proximal forearm projection

  • the proximal forearm structures including the ulna, radial tubercle and radial head should demonstrate little signs of distortion, with the distal humerus notably foreshortened and distorted

  • the radial head would be seen end-on with open elbow joint space demonstrated

Practical points

This is not a requestion view, rather a modified projection of the AP view and patient positioning is limited by pain/injury. As patients requiring this projection will be in pain, it is important to physically show the projection before asking them to do it. 

If a patient presents after closed reduction in a back slab, their forearm may often be pronated as this provides the most stable configuration for the elbow joint. This will result in the proximal radius and ulna crossing over each other (see case 1).