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 articulates 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 attaches the medial cuneiform to the 2^nd metatarsal base via three bands, the dorsal ligament, interosseous ligament and the plantar ligament.

The ligament helps wedge the base of the 2^nd metatarsal base between the medial and lateral cuneiforms creating a keystone-like configuration, 'locking' the tarsometatarsal joint in place and acting as a key transverse stabilizer of the foot. Its integrity is crucial to the stability of the Lisfranc joint.

Etiology

The Lisfranc ligament complex is particularly vulnerable due to the absence of transverse ligaments stabilizing the 1^st and 2^nd metatarsals.

Injury mechanisms are varied and include:

• direct crush injury or an indirect load onto a plantarflexed foot ³
• forefoot abduction-type injuries where the hindfoot is fixed and there is rotation around the joint such as changing direction with a foot planted firmly i.e. with cleats or football boots (this is the classic 'horse stuck in stirrup mechanism)
• forced plantar-flexion where the plantarflexed foot undergoes significant axial loading

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. Still, 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 1^st and 2^nd metatarsal bases ¹⁰.

Other possible findings are malalignment between the lateral border of the base of the 1^st metatarsal and the lateral border of the medial cuneiform; malalignment between the medial border of the base of the 4^th metatarsal and the cuboid (on the oblique view); increased distance between the medial cuneiform and the 2^nd metatarsal; and increased distance between the medial and intermediate cuneiforms (C2) ¹³.

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. 

If the diagnosis is in doubt, it may be useful to obtain weight-bearing x-rays and comparison views of the contralateral side ¹¹.

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

Treatment may be non-operative or operative, with the aim being to have a painless, plantigrade and stable foot ¹².

Indications for non-operative treatment include undisplaced injuries that are stable with weight-bearing or poor surgical candidates such as non-ambulatory patients, patients with significant comorbidities that have high risk for complications (e.g. severe vascular disease, peripheral neuropathy) or pre-existing inflammatory arthritis ¹².

The indication for operative management is an unstable injury. These can be divided into joint saving or joint sacrificing. Joint saving surgery includes temporary fixation whilst awaiting definitive management and ORIF. Joint sacrificing surgery is either arthrodesis of the 1st, 2nd and 3rd tarsometatarsal joints or midfoot arthrodesis ¹².

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 these complications' features, 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.