Foot (weight-bearing medial oblique view)

The weight-bearing medial oblique view of the foot is a specialised projection that places the foot under normal weight-bearing conditions.  The projection is utilised to assess the foot under stress and better demonstrate structural and functional deformities. 

Indications

This projection is utilised to assess the structural integrity of the foot. If the patient is able, weight-bearing views should be performed in acute and follow-up settings ¹. 

This view is key to the assessment of foot alignment and the diagnosis of abnormalities causing malalignment and foot pain, i.e. Lisfranc injury. Bilateral projections may be requested for comparison purposes.

Ultimately the radiographer will determine if the projection is safe to perform.

Patient position

• the foot is planted on the detector (often a detector cover) with the lower leg perpendicular to the floor (weight-bearing surface)
• patient distributes weight evenly across both feet

Technical factors

• angled medial oblique projection
• centring point
  • ​base of the third metatarsal
  • central beam is angled approximately 15-20 degrees medial i.e. angled latero-medial to mimic a rolled medial oblique projection
    • given the rolled oblique projection isn't a natural weight-bearing projection, patients tend to distribute weight unevenly the angled projection is preferred to ensure a true weight-bearing projection has been performed
• collimation
  • anterior to the skin margins of the distal phalanges 
  • medial/lateral to the skin margins
  • posterior to the calcaneum 
• orientation
  • ​portrait
•  detector size
  • 18 cm x 24 cm
• exposure​
  • 50-60 kVp
  • 3-6 mAs
• SID
  • 100 cm
• grid
  • no

Image technical evaluation

• 1st metatarsal has even concavity
• the spaces between the 2nd to 5th metatarsal are equal, yet the bases are overlapping
• intertarsal space between the medial and intermediate cuneiform should be opened

Useful measurements

• hallux valgus angle
• hallux interphalangeal angle 
• intermetatarsal angle
• distal metatarsal articular angle
• AP talo-first metatarsal angle
• intermetatarsal angle
• first to second metatarsal distance
• medial cuneiform to second metatarsal distance
• talonavicular coverage angle

Practical points

As these views are often requested to rule out Lisfranc injuries, remember to encourage your patient to place normal, even weight distribution on their feet, instead of forcing their weight on them.

Ensure ample warning is provided to the patient of the x-ray tube's close proximity to their torso. To prevent patients from burning themselves, remind them not to use the often overheated tube as weight support.