Ankle (horizontal beam lateral view)

The ankle horizontal beam lateral view is a modified lateral view part of a three view ankle series.

Indications

This projection is used to assess the distal tibia and fibula, talus, navicular, cuboid, the base of the 5^th metatarsal and calcaneus. It is a highly adaptable projection that can be used in trauma or with patients who are unable to ambulate to the desired standard lateral position.

Patient position

• patient is in a supine position
• this projection can be done from either side depending on the makeup of the room and the patients' pathology
  • if projection is mediolateral, the non-affected leg is raised/placed on a stand in a flexed position to avoid superposition 
  • if projection is lateromedial, both legs can lay in their natural AP position 
• foot in dorsiflexion if possible 

Technical factors

• mediolateral/lateromedial horizontal beam projection
• centring point
  • mediolateral
    •  bony prominence of the medial malleolus of the distal tibia
  • lateromedial 
    • bony prominence of the lateral malleolus of the distal fibula
• collimation
  • anteriorly from the hindfoot to the skin margins of the most posterior portion of the calcaneus
  • superior to examine the distal third of the tibia and fibula
  • inferior to the skin margins of the plantar aspect of the foot
• orientation
  • portrait or landscape 
• detector size
  • 18 cm x 24 cm
• exposure
  • 50-60 kVp
  • 3-5 mAs
• SID
  • 100 cm
• grid
  • no

Image technical evaluation

The distal fibula should be superimposed by the posterior portion of the distal tibia.

The talar domes should be superimposed allowing for adequate inspection of the superior articular surface of the talus.

The joint space between the distal tibia and the talus is open and uniform.

Practical points

In situations where the patient cannot be moved, this projection can be invaluable as it requires little to no patient movement and can be replicated in ICU wards.

If possible, placing a radiolucent immobilisation sponge under the ankle in question will prevent any artefacts from bed/pillows that are native to trauma rooms. 

Superior-inferior malalignment of the superior aspect of the talus is resultant of the tibia not lying parallel to the image receptor. To adjust this, angle the tube superior-inferior to mimic the tibia laying parallel. This is not ideal but in trauma, it may be the only option. 

Anterior-posterior malalignment of the talar domes is due to over or under rotation of the foot. To adjust this, angle the tube anterior-posterior to mimic correct positioning. This is not ideal but in trauma, it may be the only option.