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Midfoot trauma: Lisfranc Injury

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Description

A Lisfranc injury refers to any injury to the tarsometatarsal joint–this could vary from a sprain to a fracture dislocation, and typically refers to a fracture of the midfoot bones and/or disruption of the midfoot ligaments due to excessive load to the midfoot. The resulting pain, swelling, and inability to bear weight often leads to a prolonged recovery period. Though rare, Lisfranc injuries can go undetected and carry a high risk of chronic secondary disability, therefore physicians should have a high index of suspicion when a patient presents with midfoot trauma. 

Structure and function

The main component of the midfoot is the the Lisfranc joint complex: the junction of the metatarsals and the midfoot (navicular, cuneiforms, and cuboid tarsal bones). Apart from the capsulo-ligamentous structures, attachments from posterior and anterior tibial tendons and peroneal tendons provide dynamic stability. The articulation of the cuneiforms and bases of the metatarsals create a Roman arch for skeletal stability. The keystone of this arch is the base of the second metatarsal, which is tightly recessed between the medial and lateral cuneiforms, locking the tarsometatarsal complex and preventing medial/lateral translation. Thus, dislocation of the metatarsals or cuneiforms typically also involve fracture of the second metatarsal.

The tarsometatarsal complex consists of bones and ligaments of the midfoot, but there is no ligament connecting the first and second metatarsal. This creates a point of weakness between the first and the other metatarsals. The main stabilizer is the oblique Lisfranc’s ligament which traverses from the plantar-lateral aspect of the medial cuneiform to the plantar-medial aspect of the second metatarsal (Figure 1). Biomechanical studies have shown the Lisfranc ligament to be significantly stronger and stiffer than the plantar and dorsal cuneometatarsal ligaments, highlighting the importance of the Lisfranc ligament for the stabilization of the midfoot. 


Figure 1: This Lisfranc joint complex, with its associated bones and ligaments (from http://orthoinfo.aaos.org)

There is a neurovascular bundle that runs across the arch of the midfoot that requires consideration during a surgical approach. The dorsalis pedis artery is a continuation of the anterior tibial artery and courses over the articular capsule of the ankle joint, the talus, the navicular, and second cuneiform bones. It then crosses Lisfranc’s joint and courses between the first and second metatarsals to form the plantar arterial branch—and so is susceptible to damage from a Lisfranc injury. During this path, the dorsalis pedis artery is surrounded by the tendon of the extensor hallucis longus on its tibial side, and by the first tendon of the extensor digitorum longus and the deep peroneal nerve on its fibular side. Near its termination, the dorsalis pedis artery is crossed by the first tendon of the extensor digitorum brevis. The neurovascular bundle also includes two veins along the tibial side of the dorsum of the foot to the proximal part of the first intermetatarsal space, where it divides into the first dorsal metatarsal and the deep plantar. 

Patient presentation

Patients with acute Lisfranc injuries will present with a history of a traumatic injury to the foot. These injuries can be caused by a low-energy injury such as a twisting fall, or by a high-energy injury like motor vehicle accidents, industrial accidents, and falls from heights. Common situations observed include:

  • sporting activities that require the use of foot straps, such as windsurfing and horse-back riding. 
  • in football players, when the foot is plantar flexed and the metatarsal-phalangeal joints maximally dorsiflexed, a force directed down onto the heel by a falling player or tackle from behind can lead to hyperplantarflexion at the Lisfranc joint. 
  • high speed motor vehicle accidents where the foot is often driven into the floorboard as the driver attempts to brake to avoid the crash

According to Englanoff et al. (PMID: 7618790), gross subluxation or lateral deviation of the foot is rare so pain in the midfoot region, swelling and bruising on the center plantar surface, and pain with weight-bearing with a consistent mechanism of injury may be the only findings that suggest the diagnosis of Lisfranc injuries. A Lisfranc injury may be stable or unstable. Stable Lisfranc injuries are characterized by a ligamentous injury that is not severe enough to allow the tarsometatarsal joints to displace. Stable Lisfranc injuries typically have no apparent fractures, or fractures that are non-displaced. Unstable Lisfranc injuries result in displacement of some or all of the tarsometatarsal joint with associated complete ligament disruption and/or signifiant fractures of the metatarsal base(s).

Objective evidence

On physical exam, the following can be observed with Lisfranc injuries:

  • Plantar ecchymosis: bruising in the plantar aspect of the midfoot (Figure 2)
  • Diminished dorsalis pedis pulse (the artery courses over the proximal head of the second metatarsal) can indicate a more severe dislocation
  • Palpation of the foot produces maximum tenderness at the base of the first and second metatarsals
  • Inability of the patient to bear weight on tiptoe
  • When weight-bearing (if weight-bearing is even possible), there is a wider gap between the big and second toe in the injured foot (the gap sign), as well as a convex bulge at the midfoot on the medial border (Figure 3)
  • While holding the hindfoot fixed, abduction and pronation of the forefoot will elicit acute pain and tenderness that suggests a Lisfranc injury over a simple sprain.
  • While stabilizing the second metatarsal, side-to-side compression of the midfoot and dorsal/plantar deviation to the first metatarsal head produce pain at the midfoot which is positive in all patients with a rupture of Lisfranc's ligament. 

Figure 2: Plantar ecchymosis associated with Lisfranc injury

Figure 3: The medial border of the right foot shows subtle convexity when compared to the left foot in a patient with Lisfranc ligament injury in the right foot.

Radiographs should include weight-bearing anteroposterior, lateral views, and 30 degree oblique views. These should be assessed for any fractures, dislocations, or incongruity of the tarsometatarsal joints. Obtaining a comparison image of the other foot is useful to have a reference for normal alignment. On review of the AP films, the diastasis between the bases of first/second metatarsals and between the medial/middle cuneiforms should be closely examined.  Alignment of the medial border of the second metatarsal/ middle cuneiform and the medial border of the first metatarsal/medial cuneiform should also be assessed. On lateral films, the superior border of the metatarsal base is normally aligned with the superior border of its corresponding tarsal, but when injured, the metatarsals may sometimes be shifted dorsally or plantar relative to their respective tarsal bone. On the oblique view alignment of the medial border of the fourth metatarsal and the cuboid is checked.  A radiographic finding pathognomonic of a Lisfranc injury is the "fleck sign." This is produced by a bony fragment avulsed at the attachment of the Lisfranc ligament and lying between the bases of the first and second metatarsals. 


Figure 4: Anteroposterior weight-bearing radiograph demonstrating fracture of the second metatarsal and subluxztion of the Lisfranc joint. 

Figure 5: Fleck Sign
Anteroposterior weight-bearing radiograph illustrating the medial second metatarsal base malaligned with the medial edge of the middle cuneiform. The triangles point to the "fleck sign" (PMID: 9672432) 

A CT or MRI scan may be ordered in cases where it’s difficult to diagnose subtle fractures or dislocations. 

Epidemiology

Lisfranc joint injuries are rare, complex, and frequently misdiagnosed. According to Englanoff et al. (PMID: 7618790), the incidence of Lisfranc fracture-dislocations are 1 in 55,000 persons per year, accounting for less than 1% of all fractures. Furthermore, as much as 20% of Lisfranc injuries are missed on initial radiographs. 

Differential diagnosis

Compartment syndrome
Longitudinal stress injuries
Cuboid fracture
Navicular fracture
Rupture of posterior tibial tendon

Red flags

Lisfranc injuries have a high risk of chronic secondary disability, so early diagnosis is important for good functional outcome and proper management. Any acute midfoot pain following a traumatic event should be considered a LIsfranc injury until proven otherwise. Common sequelae of Lisfranc injuries include late midfoot collapse (flatfoot deformity), metatarsalgia, posttraumatic arthritis. According to Arntz et al (PMID: 3796955), post-traumatic arthritis and flatfoot can occur in up to 50% of cases. 

Treatment options and outcomes

Non-operative Treatment of Lisfranc Injuries
For stable injuries, immobilization in a cast or boot can be recommended. Patients are usually asked to be non-weight bearing for 6 weeks. With a stable injury, the Lisfranc ligament remains intact, and 6 weeks is a sufficient amount of time for healing. After 6 weeks, the patient can gradually increase activity. However, full recovery for a stable LIsfranc injury can take several months, whereas fully recovery following a displaced Lisfranc injury requiring surgery often takes 12-18 months.

Operative Treatment fo Lisfranc Injuries
Surgery should be considered in unstable injuries, where the ligaments are displaced and the tarsometatarsal join is displaced. Surgical repair should be done within the first 12-24 hours after the injury or after 7-10 days (after the swelling has reduced).

  • Open reduction internal fixation (ORIF): this surgical technique is currently the accepted technique for displaced Lisfranc joint injuries. This procedure allows the bones and ligaments to be held in place for proper healing and involves reducing and fixing each affected tarsometatarsal joint with screws and/or a plate (see figure 6). The first metatarsal-medial cuneiform articulation is reduced and stabilized first, because this often results in the reduction of the second metatarsal-middle cuneiform joint (Lisfranc complex). Reduction of the fracture-dislocation of the second metatarsal is essential, and firm opposition of the lateral border of the medial cuneiform to the second metatarsal allows for healing of Lisfranc’s ligament. A subsequent surgery to remove the hardware may be necessary.
  • Primary arthrodesis: if the diagnosis is delayed or the injury is associated with a complete disruption of the midfoot ligaments, arthrodesis (fusion of the bones making up the involved tarsometatarsal joint) may be required to successfully address a LIsfranc injury. An arthrodeis eliminates motion in the affected joint completely. Prospective randomized studies by Henning et al (PMID: 19796583) and Ly et al (PMID: 16510816) seem to suggest primary arthrodesis may result in better short-term and medium-term outcomes for displaced Lisfranc injuries when compared to ORIF. The rate of secondary surgeries (planned and unplanned, including hardware removal and salvage arthrodesis) are significantly reduced with primary arthrodesis. However, it is unclear whether there is a difference in post-operative level of activities.

Figure 6: ORIF of Lisfranc injury (from www.footeducation.com)

Recovery
After either surgery (reduction or fusion), a period of non-weight bearing for 6 to 8 weeks is recommended in a cast or cast boot. Weight bearing is started while the patient is in the boot if the x-rays look appropriate after 6 to 8 weeks. This is also the time when the patient will be weaned from a boot to a stiff sole shoe. After between 2-6 months post-op, a subsequent surgery may be required to remove the hardware depending on the injury pattern and the surgeon's preference. A return to impact activities, such as running and jumping, may take many months and should be done in a graduate manner. It takes at least a year and often much longer to achieve maximal improvement. Some athletes never return to their pre-injury levels of sport after these injuries. Despite excellent surgical reduction and fixation, midfoot arthritis may occur from damage to the cartilage. This can lead to chronic midfoot pain and may require fusion in the future.

Complications
As reported by Arntz et al (PMID: 3796955), post-traumatic arthritis is the most common complication (occurring in up to 50% of cases) of Lisfranc joint injury, which is related to the degree of comminution of the articular surface. Arthrodesis procedures (fusion of the joint) to treat post-traumatic arthritis typically are not be performed until a year or more after the injury. The risks of midfoot fusion as treatment of post-traumatic arthritis includes potential damage to the superficial sensory nerves and the dorsalis pedis artery. Subsequent neuroma formation on the dorsum of the foot can be debilitating. There is also a risk of the extensor tendons being damaged. 

Miscellany 

Injuries to the tarsometatarsal joint were originally described by Lisfranc (a Napoleonic era gynecologist and field surgeon).  He noted that horse riders who got their foot caught in the stirrup when they were knocked off their horses would suffer a serious injury to this joint.  As a result he often needed to performed an amputation through the middle part of the foot. That joint through which he amputated now bears his name as does the major stabilizing ligament that runs from the medial cuneiform to the 2nd metatarsal.

Key terms

Lisfranc injury, Lisfranc ligament, fleck sign, plantar ecchymosis, midfoot arthritis, Lisfranc open reduction internal fixation (ORIF)

Skills

Recognize the physical exam signs of a Lisfranc injury.  
Assess foot radiographs for integrity of the tarsometatarsal joint.