Lisfranc injuries

The Lisfranc joint complex is composed of the bones and ligaments that connect the midfoot to the five metatarsals of the forefoot and Lisfranc ligament connects the base of the second metatarsal to the lateral aspect of the medial cuneiform providing stability to the joint, despite the absence of a ligamentous connection between the first and second metatarsal. 

Lisfranc injuries are a spectrum of injuries which typically occur when an axial load is applied to a plantar-flexed foot. The severity of injury may range from a simple sprain to complete disruption of the tarso-metatarsal joints in the midfoot. These injuries are easy to miss (often diagnosed as a sprain in EDs) because they are rare and often show only subtle or no x-ray findings (1/5 have normal X rays). 

It is important for emergency physicians to be aware of the anatomy of Lisfranc joint complex and have a high index of suspicion for this injury since missed injuries result in long-term misalignment and functional weight-bearing difficulties. 


Clinical Presentation

• Patients are typically unable to weight bear
• Hematoma/ecchymosis on the plantar aspect of the foot
• Significant dorsal midfoot swelling
• Signs of compartment syndrome
• Tenderness to palpation over the midfoot
• Tenderness on twisting the forefoot after stabilising the heel
• Exacerbation of pain with dorsal and plantar flexion of each digit 
• Exacerbation of pain when walking on tiptoes 
• Fleck sign - Small chip fracture from medial margin of the base of M2

Diagnosis

Normal findings on Ankle X Rays:

• On the AP view, the medial edge of the base of the second metatarsal should line up with the medial edge of the middle cuneiform
• The gap between the second metatarsal and medial cuneiform is <2 mm.
• On the oblique view, the medial edge of the third and fourth metatarsal should line up with the medial edges of the middle cuneiform and cuboid, respectively.1
• On the lateral view, the superior border of the first metatarsal should align with the superior border of the medial cuneiform 
• Look for widening between the bases of the 1st and 2nd or 2nd and 3rdmetatarsal bases. Widening >2mm is an indication for urgent surgical intervention

On the AP view (left), the medial edge of the base of the second metatarsal should line up with the medial edge of the middle cuneiform. On the oblique view (right), the medial edge of the third and fourth metatarsal should line up with the medial edges of the middle cuneiform and cuboid, respectively.

Superior border of the first metatarsal aligns with the superior border of the medial cuneiform 

Note widening between medical cuneiform and second metatarsal. Fleck sign - Small chip fracture from medial margin of the base of the second metatarsal

With high suspicion of Lisfranc injury but normal initial X Rays, obtain a30-degree oblique x-rays or do a CT of the foot. 

ED Management

Stable dislocation/fracture injuries are defined as having less than 2 mm of displacement between the first metatarsal and medial cuneiform. These can be managed non-operatively with reduction and casting. The patient should be placed in a non-weight-bearing below-the-knee cast for six weeks and have an outpatient orthopedic follow-up in 2 weeks.  Discharge instruction should include elevation of the leg and warning signs of compartment syndrome of the foot.

For unstable fractures and dislocations ((>2mm widening at the Lisfranc joint), immediate orthopedic consultation is needed for surgical intervention with internal fixation.

Posted by:

              

     Lakshay Chanana

     

     ST4 Trainee

     Royal Infirmary of Edinburgh

     Department of Emergency Medicine

     Edinburgh

     Scotland

     @EMDidactic