radER Case 13.2 (#14)

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Case

25 YOM presents to the ED complaining of sudden onset of right foot pain while playing football earlier today. He states that he was bearing all of his weight on his right foot at the time of the onset of pain. He states that his pain is significantly worsened with bearing weight and ambulation. He denies numbness and tingling. He denies any previous right lower extremity injuries. A right foot x-ray was obtained.

1. What abnormality should be identified in these radiographs?

2. What is the most common secondary/associated fracture involving the above abnormality?

3. Which statement is true of the proper treatment of the above injury?

Case 14 Answers

1. Correct Answer C. Lisfranc Fracture. Separation of the bases of the 1st and 2nd metatarsals should be evident in this film. It also appears as though there may be an avulsion fracture of the base of the 2nd metatarsal associated with the dislocation injury. No evidence of Jones or Pseudo-Jones fracture is noted in these views. No accessory bone is noted near the base of the 5th metatarsal to suggest Os peroneum. Os peroneum is very common seen in nearly 26% of foot x-rays and should not be mistaken for apophysis or avulsion fracture of the 5th metatarsal.

2. Correct Answer A. Base of 2nd Metatarsal Fracture is the most common fracture associated with a Lisfranc injury/dislocation.  Calcaneal fractures are not directly associated with Lisfranc dislocation fractures however should be suspected in MVC trauma patients that sustain Lisfranc injury. Cuboid fractures are seen as a result of Lisfranc dislocation however not as commonly as 2nd metatarsal fractures. Avulsion fractures of the 5th metatarsal are not commonly associated with Lisfranc dislocation.

3. Correct Answer B. ED Orthopedic consultation and evaluation. Lisfranc dislocation injuries all need to be evaluated immediately by an orthopedic surgeon. If unstable, surgery is the only corrective measure. The patient is to be NWB on the affected lower extremity. They should be placed in a short leg splint to stabilize/immobilize the foot and ankle.

Discussion:

Mechanism of Injury

  • Mechanism involves severe plantar flexion of the foot
  • May occur from sports-related injuries
  • Motor vehicle accidents
  • Falling from a height, down stairs or off a curb

Lisfranc ligament diagonally connects the 1st (medial) cuneiform with the base of the 2nd metatarsal. If it remains intact, either an avulsion of the lateral border of the 1st cuneiform or an avulsion of the base or medial border of the 2nd metatarsal occurs. If it tears, these fractures may not occur

Have a high index of suspicion as 20% of cases are undiagnosed due to other sustained trauma

Clinical findings

  • Pain at tarsal-metatarsal joints
  • Ecchymosis
  • Instability

Two basic types

A. Homolateral

  • All of the metatarsals are dislocated to the same side
  • More common than divergent
  • Usually involves the 2nd through 5th dislocated laterally
  • May involve all 5 metatarsals

B. Divergent

  • Usually more severe than homolateral
  • May be associated with a fracture of the 1st cuneiform
  • Usually involves medial displacement of the 1st metatarsal and lateral displacement of 2nd-5th metatarsals
  •  Occasionally may involve only medial displacement of only the 1st metatarsal

Fractures commonly associated with Lisfranc dislocations

  • Base of 2nd metatarsal (most common)
  • Cuboid
  • Fractures of shafts of metatarsals
  • Dislocations of the 1st (medial) and 2nd (middle) and cuneonavicular joints
  • Fractures of the tarsal navicular

Imaging

  • Conventional radiographs are usually sufficient to demonstrate the injury.

Normal alignment of the cuneiforms and the bases of the metatarsals

  • Lateral border of 1st metatarsal is aligned with lateral border of 1st (medial) cuneiform on AP view
  • Medial border of 2nd metatarsal is aligned with medial border of 2nd (intermediate or middle) cuneiform on AP view
  • Medial and lateral borders of the 3rd (lateral) cuneiform should align with medial and lateral borders of 3rd metatarsal on oblique view
  • Medial border of 4th metatarsal aligned with medial border of cuboid on oblique – Lateral margin of the 5th metatarsal may project lateral to cuboid by as many as 3mm on oblique
  • On lateral, a line drawn along long axis of talus should intersect long axis of 5th metatarsal

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