CORE EM: Lisfranc Injuries

Definition

• The Lisfranc joint complex is a tarso-metatarsal articulation named for Jacques Lisfranc (1790-1847), one of Napoleon’s battlefield surgeons. 
• Specifically, it is the articulation of the 1^st, 2^nd, and 3^rd metatarsals with the medial, intermediate, and lateral cuneiforms, respectively, as well as the articulation of the 4^th and 5^th metatarsals with the cuboid. (Englanoff 1995)
• The Lisfranc (or Oblique) ligament secures the second metatarsal to the medial cuneiform, serving as a mortise joint anchoring the entire complex and preventing medio-lateral or plantar displacement.
• Fractures and concomitant disarticulations of this joint are termed Lisfranc fracture-dislocations

Mechanism of Injury

• Motor vehicle and industrial accidents constitute the majority of Lisfranc injuries.
• In elderly patients and athletes, Lisfranc injuries may occur after low-energy rotational events.
• Typically occurs when an axial load is applied to a plantar-flexed foot.

Epidemiology

• Prevalence: 1 in 55,000 (Sherief 2007)
• Missed on first evaluation in 20% of cases (Englanoff 1995)

Classification

• No validated formal classification scheme exists for assessing the severity or management of a Lisfranc injury

Physical Exam

• In cases of complete ligamentous tear, ecchymotic discoloration of the plantar midfoot is common; however, findings on inspection may be subtle or absent.
• Tenderness to palpation over the midfoot
• Stress examination of the midfoot
  • Performed by stabilizing the heel with one hand and twisting the forefoot with the other.
  • Markedly exacerbates pain
• The “Piano Key” test: Exacerbation of pain with dorsal and plantar flexion of each digit (Wedmore 2015)
• Single limb heel raise: Exacerbation of pain when patient stands on one leg and then on tip toes (places significant strain on injured area)

Imaging

• Patients may not meet Ottawa ankle/foot imaging rules. In patients with suspicious mechanism, have a low threshold to image
• X-ray Yield
  • High-energy mechanism: Obvious fracture/dislocation of the associated tarsal and metatarsal bones will likely (but not definitely) be present on x-ray.
  • Low-energy mechanism (with high clinical suspicion of Lisfranc injury): Weight-bearing AP views of the foot can help make the diagnosis if the initial foot x-ray is normal. 
• Subtle x-ray findings suggestive of a clinically significant Lisfranc injury:
  • Loss of the smooth alignments at the medial border of the second metatarsal with the medial cuneiform and/or the medial border of the fourth metatarsal with the cuboid
  • Diastasis (separation beyond normal) of the space between the bases of the 1st and 2^nd metatarsals
    • • Diastasis is a measurement >2mm in a normal foot, or >1mm relative to the contralateral foot in people with widened joint spaces at baseline
      • Bilateral films are thus necessary when obtaining weight-bearing views.
  • A metatarsal shaft should never be more dorsal than its respective tarsal bone 
  • Presence of an avulsion fracture, called the “fleck sign”

ED Management

• Carefully perform neuromuscular examination with special attention to dorsalis pedis (DP) pulse – transection is rare but well described
• Any of the following conditions requires emergent reduction and orthopedic consultation
  • Fracture displacement
  • Associated dislocation
  • Evidence of compartment syndrome
  • Evidence of neurovascular injury
• CT scan of the foot
  • Improved visualization particularly when X-rays equivocal but continued suspicion (i.e. inability to bear weight)
  • Operative planning
  • Obtaining CT in ED will depend on department resources and orthopedic referral availability
• Immobilization with posterior splint
• Strict non-weight bearing (NWB) on crutches
• Orthopedic or podiatry follow-up within one week for possible surgical reduction and fixation

Prognosis

• When initially misdiagnosed/untreated, Lisfranc injuries carry a poor prognosis, often resulting in deformity, functional deficit, and chronic pain
• When diagnosed appropriately, patients who undergo open reduction and internal fixation of fractures have superior outcomes to those with purely ligamentous injury (Sherief 2007)
• Patients with no fracture on CT and no displacement on weight-bearing films generally are managed non-operatively

Take Home Points

• A Lisfranc injury must be part of the differential for any midfoot trauma because of the significant morbidity associated with missed diagnosis
• Physical exam findings, including deformity, swelling and ecchymosis, may be subtle or absent
• Normal foot x-rays do not rule out a Lisfranc injury, weight-bearing views or CT are essential

Read More

Radiopaedia: Lisfranc Injury

Radiopaedia: Lisfranc Joint

References

• Englanoff G et al. Lisfranc Fracture-Dislocation: A Frequently Missed Diagnosis in the Emergency Department. Ann Emerg Med 1995: 26 (2); 229-233.  PMID: 7618790
• Sherief, T et al. Lisfranc injury: How frequently does it get missed? And how can we improve?  Injury: International Journal of the Care of the Injured 2007: 34; 856-860.  PMID: 17214988
• Wedmore, I. et al. Emergency Department Evaluation and Management of Foot and Ankle Pain. Emergency Medicine Clinics of North America May 2015: 33 (2); 371-372.  PMID: 25892727