What is the recommended protocol for ordering foot and ankle x-rays?

Standard Protocol for Ordering Foot and Ankle X-rays

For optimal diagnosis of foot and ankle injuries, radiographs should include three standard views: anteroposterior (AP), lateral, and medial oblique projections for the foot, and AP, mortise, and lateral projections for the ankle, preferably with weight-bearing if the patient can tolerate it. 1, 2

Standard Views Required

Foot X-rays:

• Anteroposterior (AP) view
• Lateral view
• Medial oblique view

Ankle X-rays:

• Anteroposterior (AP) view
• Lateral view
• Mortise view (AP view with 15-20° internal rotation)

Weight-bearing Considerations

• Weight-bearing radiographs are preferred when possible, as they can reveal dynamic abnormalities such as:

  • Joint malalignment
  • Joint subluxation
  • Fracture displacement
  • Lisfranc injuries

• When to use non-weight-bearing views:

  • Patient unable to bear weight due to pain
  • Risk of further displacement of joints/bones
  • Limited mobility of the patient

Special Considerations

1. Bilateral comparison:

   • When possible, obtain bilateral plain X-rays for comparison purposes 1
   • Particularly valuable for suspected Charcot neuro-osteoarthropathy

2. Additional specialized views when indicated:

   • Sesamoid axial view for hallux MTP joint injuries
   • Broden view for calcaneal fractures
   • Stress views for suspected ligamentous injuries

3. When standard X-rays are negative but clinical suspicion remains high:

   • MRI is indicated for persistent pain (>1 week) with negative radiographs (sensitivity 93-96%, specificity 100%) 1, 2
   • CT for complex midfoot fractures (25% of midfoot fractures identified on CT are missed on radiographs) 1, 2

Clinical Pitfalls to Avoid

• Inadequate coverage: Ensure the entire foot is included, particularly the base of the fifth metatarsal which is a common fracture site 2

• Relying solely on two views: Although some studies suggest two views may be sufficient for fracture detection 3, 4, the addition of the oblique view increases diagnostic confidence and reveals unique abnormalities in 4.8% of cases 5

• Missing subtle injuries: Initial radiographs may miss up to 10% of fractures that become visible only on follow-up imaging 2

• Failing to consider advanced imaging: When radiographs are normal but clinical suspicion remains high, advanced imaging should be considered:

  • MRI for suspected occult fractures or soft tissue injuries
  • CT for complex midfoot fractures or preoperative planning
  • Ultrasound for suspected foreign bodies or tendon injuries 1

Evidence-Based Approach to Ordering

1. Initial evaluation: Standard three-view radiographs of the foot and/or ankle

2. If radiographs are negative but clinical suspicion remains high:

   • For suspected occult fracture: MRI without contrast
   • For complex midfoot injuries: CT without contrast
   • For suspected tendon abnormality: MRI or ultrasound
   • For suspected foreign body (non-radiopaque): Ultrasound

3. For specific conditions:

   • Suspected Lisfranc injury with normal radiographs: MRI or CT 1
   • Suspected Charcot neuro-osteoarthropathy with normal radiographs: MRI 1
   • Suspected osteochondral lesion with normal radiographs: MRI 1

By following this standardized protocol for ordering foot and ankle X-rays, clinicians can optimize diagnostic accuracy while minimizing unnecessary radiation exposure and healthcare costs.