What is the diagnosis?

Fracture of the second metatarsal with widening between it and the base of the first, giving concern for LisFranc injury

Image 2. Image courtesy of The Radswiki, Radiopaedia.org, rID: 11581. Annotation by author

• Pearl: The articulation of the midfoot and the forefoot is referred to as the LisFranc joint complex. This is made up of several ligamentous connections between the metatarsals and cuneiforms or cuboid. The term LisFranc ligament specifically refers to the ligament connecting the medial cuneiform and second metatarsal. 

• Pearl: While high impact injuries are easier to identify, low impact LisFranc injuries are often missed to do subtle exam and imaging findings [1]. Quick identification and management are critical to reduce midfoot stability, arch collapse and osteoarthritis that could result in chronic stiffness, pain, and dysfunction of the foot and ankle complex [2].

What is the mechanism of injury?

There are two main mechanisms of injury:

• Direct - Crush or fall from height

• Indirect (more common in sports) - Bending or torsion of the tarsus, axial loading of the heel in plantar flexion [3]

What physical exam findings are expected?

Exam findings can vary depending on the severity of injury (<5 mm subluxations to severe fracture-dislocations), however most patients will be present with swelling of the forefoot and midfoot and inability to bear weight. Plantar ecchymosis may also be present. 

• Pearl: The “piano key” test can be useful in identifying the metatarsal affected by stabilizing the midfoot and assessing for joint laxity by moving the head of the affected metatarsal, though this can be limited in the acute setting due to pain and swelling [4].

Which imaging modalities can be used?

X-Ray is the initial modality assessing for fracture or widening and is 84% sensitive in detection [5]. In the case of a negative or equivocal X-Ray with high clinical suspicion, CT scan is useful in detecting subtle nondisplaced fractures or minimal bone subluxations. MRI is the gold standard in assessing for ligamentous injury, but this can be performed in an outpatient setting. 

Image 3: CT Scan of the Right Foot demonstrating fracture of the base of the second metatarsal. Case courtesy of Colin-John Perrins, Radiopaedia.org, rID: 60021

What is the management in the ED?

After identification of a LisFranc injury, the patient should be evaluated for compartment syndrome. Once this is ruled out the patient can be placed in a short posterior splint with stirrups or boot and is to remain non-weight bearing for at least 6 weeks. Injuries confined to the ligament can follow-up with orthopedics outpatient [6].

When do you consult Orthopedics?

When assessing for LisFranc injuries there should be a low threshold for consulting orthopedics. Instability on initial or repeat radiographs will need to be corrected surgically, though these can occasionally be managed non operatively if they are managed and heal appropriately [6,7].