EMRad: Approach to the Traumatic Foot X-ray

Radiology teaching during medical school is variable, ranging from informal teaching to required clerkships [1].^​​ Many of us likely received an approach to a chest x-ray, but approaches to other studies may or may not have not been taught. We can do better! Enter EM:Rad, a series aimed at providing “just in time” approaches to commonly ordered radiology studies in the emergency department. When applicable, it will provide pertinent measurements specific to management, and offer a framework for when to get an additional view, if appropriate. We recently covered the elbow, wrist, and ankle: now, the foot x-ray.

Learning Objectives

1. Interpret traumatic foot x-rays using a standard approach
2. Identify clinical scenarios in which an additional view might improve pathology diagnosis

Why the foot matters and the radiology rule of 2’s

The Foot

• The foot is a complex part of human anatomy and is a frequent cause for a visit to the Emergency Department [2].
• Simple foot injuries can have substantial morbidity, including loss of function, arthritis, and impaired quality of life [3].

Before we begin: Make sure to employ the rule of 2’s [4]

• 2 views: One view is never enough.
• 2 abnormalities: If you see one abnormality, look for another.
• 2 joints: Image above and below (especially for forearm and leg).
• 2 sides: If unsure regarding a potential pathologic finding, compare to another side.
• 2 occasions: Always compare with old x-rays if available.
• 2 visits: Bring patient back for repeat films.

An approach to the traumatic foot x-ray

1. Adequacy (AP, Oblique, Lateral)
2. Bones
3. Cartilage/Joints
4. Consider an additional view

1. Adequacy

• A standard foot x-ray series consists of the AP, lateral and oblique
  • AP: all metatarsals should be visible
  • Oblique: should be taken with foot angled 30-40 deg medially
    • This view is best used in the evaluation of midfoot and forefoot [5].
  • Lateral: should include projection of ankle in addition to foot [5].
    • The base of 1st, 2nd, and 3rd metatarsals should align with three cuneiform bones [5].
    • The Metatarsophalangeal joints should be clear [5].

2. Bones

• On AP and Oblique:
  • Talus (Hindfoot)
  • Navicular (Midfoot)
  • Cuboid (Midfoot)
  • Cuneiforms (Midfoot)
  • Metatarsals (Forefoot)
  • Phalanges (Forefoot)
• On Lateral:
  • Talus (Hindfoot)
  • Navicular (Midfoot)
  • Calcaneus (Hindfoot)

3. Cartilage/Joints

• Lisfranc Joint complex, best appreciated on AP and oblique view
  • A normal joint complex on AP view:
    • Alignment of the lateral edge of the base of the 1st metatarsal and the lateral edge of the medial cuneiform (Figure 2, line 1)
    • Alignment of the medial edge of the base of the 2nd metatarsal and the medial edge of the middle cuneiform (Figure 2, line 2) [6]

• • A normal joint complex on oblique view:
    • Alignment of the lateral edge of the shaft of the 3rd metatarsal and the lateral border of the lateral cuneiform (figure 3, line 4)
    • Alignment of the medial border of the 4th metatarsal with the medial border of the cuboid (figure 3, line 5) [6].

4. Consider an additional view

“Weight-Bearing” Foot AP or lateral

• When: Obtain a “weight-bearing” view if there is any concern for Lisfranc injury
• Why: Weight-bearing views may not show diastasis of joint [2].
  • Pearl:  Consider CT as you may diagnose concomitant fractures

Calcaneus view

• Check out the EMRad ankle post for more information on this view.

References

1. Schiller, P. et al. Radiology Education in Medical School and Residency. The views and needs of program directors. Academic Radiology, Vol 25, No 10, October 2018. PMID: 29748056
2. Wedmore, I. et al. Emergency Department evaluation and management of foot and ankle pain. Emerg Med Clin N Am 33. Issue 2. May 2015. PMID: 25892727
3. Flaherty, E. et al. Emergency Imaging of Foot Trauma. Semin Roentgenol. Volume 51. Issue 3. Dec 2015. PMID: 27287956.
4. Chan, Otto. Introduction: ABCs and Rules of Two. ABC of Emergency Radiology, Third Edition. Edited by Otto Chan. 2013 John wiley & Sons, Ltd. Published 2013.
5. Nicholson, D et al. The Foot. ABC of Emergency Radiology. BMJ. Volume 307. October 1993. PMID: 7902156
6. Englanoff, G. et al. Lisfranc Fracture-dislocation: A frequently missed diagnosis in the Emergency Department. Annals of Emergency Medicine. Volume 26. Issue 2. August 1995. PMID: 7618790

 

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