Lisfranc injury

Lisfranc injuries, also called Lisfranc fracture-dislocations, are the most common type of dislocation involving the foot and correspond to the dislocation of the articulation of the tarsus with the metatarsal bases.

Pathology

Anatomy

The Lisfranc joint is the articulation of the tarsus with the metatarsal bases, whereby the first three metatarsals articulate respectively with the three cuneiforms, and the 4^th and 5^th metatarsals with the cuboid.

The Lisfranc ligament is a strong band attaching the medial cuneiform to the 2^nd metatarsal base on the plantar aspect of the foot. Its integrity is crucial to the stability of the Lisfranc joint.

Etiology

Injury mechanisms are varied and include direct crush injury, or an indirect load onto a plantarflexed foot ³. Tarsometatarsal dislocation may also occur in the diabetic neuropathic joint (Charcot).

Subtypes

There are several types of Lisfranc fracture-dislocation:

• homolateral: a homolateral injury is a lateral displacement of the 1^st to 5^th metatarsals, or of 2^nd to 5^th metatarsals where the 1^st MTP joint remains congruent
• divergent: a divergent injury is a lateral dislocation of the 2^nd to 5^th metatarsals with medial dislocation of the 1^st metatarsal
• isolated: this involves one or two metatarsals that dislocate dorsally in isolation

Radiographic features

Plain radiograph/CT

These injuries are well demonstrated on the standard views of the foot but subtle injuries may be missed and require further imaging such as CT, MRI or radiographic stress views with forefoot abduction. CT is however favored as it will also demonstrate unsuspected associated fractures.

The key finding is malalignment of the second tarsometatarsal joint, such as lateral displacement of the second metatarsal base on AP view and/or dorsal step-off sign on lateral view ¹⁰. An additional abnormality is diastasis >2 mm between the first and second metatarsal bases ¹⁰.

Associated fractures most often occur at the base of the second metatarsal, seen as the fleck sign. They may also be seen in the 3^rd metatarsal, 1^st or 2^nd cuneiform, or navicular bones. 

Ultrasound

Useful for assessing the ligamentous injury. Non-visualization of the dorsal C1-M2 ligament and a C1-M2 distance >2.5 mm is indirectly indicative of a Lisfranc ligament tear ⁵.

Dynamic evaluation with weight-bearing may show widening of the space between C1 and M2.

MRI

Again may be useful for assessing ligamentous injury especially when there is a high clinical concern with routine radiographs being inconclusive ⁷. 

Treatment and prognosis

Internal fixation is the most common treatment. 

Complications

The most common complications of ankle and foot fractures are non-union and post-traumatic arthritis. Although conventional radiography can usually demonstrate the features of these complications, CT is the better technique for delineating their details.

History and etymology

It is named after Jacques Lisfranc De Saint Martin (1790-1847), the chief of surgery at the Hôpital de la Pitie in Paris ².