Films and Scans
Consider this scenario. You’re nearing the end of another busy shift in the emergency department but muster the energy to pick up one more chart…a healthy 65-year-old female with a foot injury. The x-rays are done. Should be a quick dispo, right?
She relates that she tripped and slid down about three wooden steps and now complains of severe pain in the right midfoot with inability to bear weight. You notice slight swelling and ecchymosis of the dorsal midfoot as well. A quick glance at her films shows no obvious fracture, so you offer ice, a hard-soled shoe, and crutches. She has a bruise or a sprain…doesn’t make much difference, does it?
Foot injuries are common in the emergency department. Midfoot injuries, however, are an uncommon subset that are often overlooked, leading to potentially disastrous long-term complications and liability exposure for the emergency physician. Missing the diagnosis can leave your patient with chronic pain and significant disability, while detecting subtle injuries will earn you respect amongst your orthopedic colleagues and improve patient outcomes.
The “Lisfranc” eponym is well known to all, and it applies to a spectrum of midfoot injuries ranging from simple sprains to fracture-dislocations. Jacques Lisfranc was a 19th-century French surgeon who pioneered a rapid forefoot amputation technique used on injured horsemen in Napoleon’s army. He amputated through the tarsometatarsal (TMT) articulation which includes nine bones. This articulation has come to be known as the Lisfranc joint complex, part of which serves as the “keystone” of the foot.
Lisfranc injuries can result from both high energy and low energy mechanisms. They may be missed due to distracting injuries in the case of high-energy trauma or, alternatively, because of a low index of suspicion or subtle presentation following low-energy trauma. Regardless of the mechanism, midfoot swelling, tarsometatarsal tenderness, pain with passive midfoot motion, or inability to bear weight should prompt further radiographic investigation. Initial imaging includes nonweightbearing AP, lateral, and oblique views of the foot; weightbearing radiographs, specifically a standing AP view of both feet, can be helpful if the patient is able to tolerate it. Images must be scrutinized for fractures, especially at the medial base of the second metatarsal and the lateral aspect of the medial cuneiform. Even a small avulsion of bone, or “fleck sign,” may indicate significant injury. Careful assessment of the alignment is also essential. Malalignment or a lateral step-off at the medial edge of the second TMT joint (second metatarsal and intermediate cuneiform) is a common abnormality.
When standard radiographs fail to demonstrate suspected injury, advanced imaging may be undertaken in the emergency department with CT or MRI. CT is most often used because of its greater speed and availability. It has excellent sensitivity for detecting fractures and malalignment when compared to radiographs and is also useful for characterizing known injuries to guide operative management. MRI nicely depicts the soft tissue anatomy but is more commonly employed in the outpatient setting.
d. 1st Cuneiform
e. 2nd Cuneiform
f. 3rd Cuneiform
Early diagnosis of a Lisfranc injury, regardless of severity, is essential for proper management and favorable outcome. Stable ligamentous sprains are treated with immobilization and non-weightbearing, while unstable injuries and fractures will typically require operative fixation. Urgent orthopedic evaluation or consultation is imperative, and compartment syndrome is a recognized complication of more severe injuries.
If we re-visit our case, the patient’s persistent pain and inability to bear weight prompted closer inspection of her radiographs. A small fleck of bone was noted at the base of the second metatarsal with slight malalignment.
Subsequent CT of the foot showed fractures at the base of the second, third, and fourth metatarsals, and it confirmed malalignment as well. The patient was discharged with a posterior splint and followed up with orthopedics the following day. She later underwent operative fixation and did well.
1. A Lisfranc injury can be a challenging diagnosis in the emergency department. Maintain a high index of suspicion in any patient presenting with midfoot complaints after low- or high-energy trauma.
2. Scrutinize radiographs for subtle fractures and/or malalignment. Advanced imaging modalities, such as CT and MRI, are helpful in making the diagnosis of Lisfranc injury when radiographs appear normal but clinical suspicion remains.