Lisfranc Injury - A Matter of a Few Millimeters
Photo by Terje Tjervaag - Flickr (Modified)
Understanding the Injury
A Lisfranc injury occurs secondary to disruption of a major stabilizing ligament of the arch of the foot. In basic terms, it is a sprain of the Lisfranc ligament, also known as the oblique interosseous ligament. The Lisfranc ligament connects directly between the medial cuneiform and the second metatarsal (photo above). As with other ligaments such as in the ankle or knee, the Lisfranc ligament can be stretched, partially torn or completely torn, which directly relates to the extent of the injury. In the athletic population, the injury usually occurs with a force directed through the foot while the ankle is in a plantarflexed position and the toes are extended (photo below). The classic injury occurs in offensive lineman as they are engaged with a defensive player and the running back falls on the heel of their teammate. An injury to this ligament can lead to instability of the arch of the foot and therefore chronic pain and disability with activities of daily living and sports participation.
Mechanism of Injury
Patients with a Lisfranc injury may present with vague pain and swelling after the injury described above. With more severe injuries the patient will have difficulty walking as well as have the inability to do a toe raise secondary to pain. On exam, the provider will usually elicit pain at the base of the base of the first and second metatarsal in the area of the Lisfranc ligament (photo below). An examiner must be careful in diagnosing a simple "midfoot sprain" without careful evaluation of a Lisfranc joint. The next step would be to obtain imaging of the foot looking for signs of instability of the Lisfranc joint.
The first step in the diagnosis is to obtain a set of x-rays looking at several aspects of the foot. The primary focus of the x-ray is the space between the base of the first and second metatarsal bones, also known as the Lisfranc joint. In general, if the space between the first and second metatarsals is greater than 2 mm then a Lisfranc ligament injury should be considered. Additionally, if a "fleck" or avulsion fracture is seen at the base of the second metatarsal or medial cuneiform, one should also consider a Lisfranc injury. The most important aspect of the radiographic evaluation is to obtain x-rays with the patient weight-bearing in order to ensure one can appreciate the full extent of the injury. The diagnosis can be mistakenly excluded if the decision is made solely on images that are performed without significant bodyweight on the foot. Due to the slight variation in normal spacing at the Lisfranc joint, it may be beneficial to obtain a similar x-ray of the opposite unaffected foot. Lastly, if the patient is unable to bear weight, one may either perform the weight-bearing x-rays at a later date (7-10 days) or obtain an MRI to look at the integrity of the ligament.
In the AP view photo on the left you will notice there is no appreciable space at the Lisfranc joint, however the photo on the right shows a significant space greater than 2 mm indicating a Lisfranc ligament injury.
As with most injuries in sports, there are multiple treatment options, depending upon the specific athlete and experience of the treating provider. Typically patients who have a grade 1 injury with pain at the Lisfranc joint and no increased spacing on x-ray, can be treated non-operatively. Non-operative treatment involves 6 weeks of protected weight bearing in a boot or walking cast although some providers may opt to keep the patient non-weight-bearing during that time. The patient will usually be transitioned into a supportive athletic shoe with arch support and progressed back to activity over the next 4 - 6 weeks. Regarding grade 2 injuries (2-5mm spacing), patients are generally thought to require surgical stabilization. However, there is certainly an argument that can be made to treat patients with 2-3 mm of spacing at the Lisfranc joint with a non-operative trial. Lastly, patients with grade 3 injuries (>5 mm spacing) will require surgery to stabilize the joint and prevent long-term pain or disability in the foot.