|Mechanism of the injury|
Tarso-metatarsal (Lisfranc) injuries may be caused by direct or indirect forces.
Direct forces include a crush injury (MVA or industrial) or a direct blow. These may be combined with soft-tissue injury and present as open fractures.
Indirect injuries are more common. They result from an axial load to a plantarflexed foot. They may occur during sports, or stepping down from a stair or sidewalk.
There is midfoot swelling, usually dorsal. There is pain on palpation of the TMT area. A provocative test may show instability. This is painful, so it should be done carefully (under regional or general anesthesia, if possible).
There is often an area of plantar medial ecchymosis.
There is pain seemingly out of proportion to the injury. Unlike a routine ankle sprain, these injuries elicit patients’ comments of a visceral nature like “I almost passed out”, “I almost threw up”.
Beware of a patient who was told in the Emergency Room that they had a “sprained foot”. Since Lisfranc injuries may represent instability without frank displacement, ER x-rays (which are often non-weight bearing) may not show the extent of the injury.
Subsequent weight-bearing x-rays in the office or clinic may show displacement/instability.
Remember, that Lisfranc injuries involve frequently high energy, which dissipates through the soft tissues and therefore they may be associated with a compartment syndrome.
|X-ray - AP view|
- Lateral displacement of 2nd metatarsal on intermediate cuneiform
- TMT 1 disruption
- Gap between 1st and 2nd metatarsal
|X-ray - 30 degree oblique view|
Lateral displacement of 3rd metatarsal on lateral cuneiform
|X-ray - lateral view|
The dorsal cortex of the metatarsals should be even with the dorsal cortex of the cuneiforms. Dorsal displacement of the metatarsal bases above the level of the cuneiforms is abnormal and indicates Lisfranc injury.
The stress test can uncover instability that may not be apparent in a static x-ray. This, however, can be painful for the patient. It could be done under anesthesia. Routine x-ray film or image intensification can be used.
If you suspect a serious injury insist on a weight-bearing film within the patients tolerance.
There is often plantar comminution.
CT can be useful to further define the injury.
There are many classification systems available to describe midfoot/TMT injuries. None are particularly useful or predictive of outcome.
There are many injury patterns other than the example shown here.