A Lisfranc injury describes an injury of the foot between the metatarsal and tarsal spaces. Around 20-40% of lisfranc injuries are initially missed, so a high degree of clinical suspicion is required.
They can range greatly in presentation from an apparent simple sprain to an obvious fracture dislocation of the whole mid-foot. However, it is important that even simple sprains are diagnosed and treated appropriately as there is a very real risk of chronic pain, altered gait and arch instability.
The joint between tarsal and metatarsal bones of the foot is held by a number ligaments. The most important stabilising ligament is the Lisfranc ligament which runs from the base of the second metatarsal to the medial cuneiform.
Damage to this ligament (with or without further injuries) can lead to an instability of the whole of the mid-foot as the second metatarsal acts like the keystone in an arch.
The image below shows the normal anatomy, and a 3 way classification of types of Lisfranc injury. These may present with or without fracture (representing further subcategories).
1) Homolateral: All 5 metatarsals are displaced in the same direction. Lateral displacement may also suggest cuboidal fracture
2) Isolated: 1 or 2 metatarsals are displaced from the others
3) Divergent: Metatarsals are displaced in a sagittal or coronal plane.
The mechanism of injury is varied. From heavy direct trauma (such as crushing of the mid-foot) to indirect trauma such as twisting of the ankle. Commonly described in this manner is an axial loading or hyper-flexing of a plantar-flexed foot. For example a gymnast landing on their toes and their foot flexing under their body.
The mechanism can be a lot more subtle than this, and the variety of mode of injury described is quite broad.
Presentation / Examination
Patients will typically present reduced or non weight-bearing.
They may present acutely, but delayed presentation is not unusual as the patient may well self care for a ‘sprain’.
Bruising to the sole of the foot is common and considered a strong indicator of a Lisfranc injury, but is not always present.
Tenderness over the base of the 1st and 2nd metatarsal and medial cuneiform is suspicious.
Compress the whole of the mid foot to apply stress to the joint. Pain or palpable click is indicative of injury.
In patients with obvious dislocation of the mid-foot ensure you rule out compartment syndrome.
Of course perform your usual foot examination including checking for other concurrent injuries – ankle, knee – whether the injury is closed, neurovascularly intact etc.
Normal plain films of the foot may show widening of the space between the 1st and 2nd metatarsals, and / or the medial and intermediate cuneiform (on AP views).
- This can be very subtle.
- Comparative views of both feet can be useful.
- If the patient is able also consider weight-bearing views as this loading may open up 1st and 2nd metatarsal space if there is instability.
Check for congruity between the medial edges of the second metatarsal and the intermediate cuneiform. These should line up.
On lateral views check for congruity between the dorsal edge of the metatarsals. These should be at the same level as the corresponding cuneiform, with no appreciable step.
Be careful to check for subtle fractures of the base of the metatarsals, especially the medial aspect of the second (the lizfranc fracture).
Patients with any radiological signs should be considered a potential candidate for surgery and as such it is recommended you consult with on-call orthopedic service.
Patients without any radiological sign but for whom you consider a high index of suspicion – consider mechanism, non-weightbearing, plantar bruising, mid-foot tenderness – should be treated in a non-weightbearing cast and referred to fracture clinic as an outpatient.
Patients with a low threshold of suspicion, but where you don’t feel able to rule out a lisfranc injury should be advised to be non or very lightly weight-bearing with crutches and referred to ED follow up clinic for further investigation.
This video gives a good simple background for the anatomy and some radiological signs. It also discusses fixation.