From the Guidelines
Weight-bearing radiographs are the initial imaging modality of choice for suspected Lisfranc injuries, as they increase the detection of subtle injuries and abnormal alignment at the Lisfranc joint. The diagnosis of a Lisfranc injury involves several clinical tests and imaging studies. The most reliable clinical tests include the piano key test, where the examiner stabilizes the heel and moves the metatarsals up and down to check for abnormal movement or pain; the gap test, which involves squeezing the midfoot to assess for pain; and the pronation-abduction test, which evaluates stability by manipulating the forefoot.
Key Imaging Modalities
- Weight-bearing radiographs are essential for diagnosis, looking for widening between the first and second metatarsals or small avulsion fractures at the Lisfranc joint 1.
- CT scans provide more detailed visualization of fractures and joint displacement, while MRI can detect ligamentous injuries that may not be visible on other imaging 1.
- Stress radiographs may be necessary if the initial imaging is inconclusive but clinical suspicion remains high.
Importance of Early Diagnosis
Early diagnosis is crucial as missed Lisfranc injuries can lead to chronic pain, arthritis, and foot deformities.
Treatment Options
Treatment depends on the severity, ranging from non-weight-bearing immobilization for stable injuries to surgical fixation for unstable or displaced injuries.
Additional Considerations
In addition to a typical three-view radiographic study of the foot (anteroposterior [AP], oblique, and lateral), an AP view with 20 craniocaudal angulation can be added to improve detection of Lisfranc injuries 1.
From the Research
Diagnosis of Lisfranc Injury
To diagnose a Lisfranc injury, the following steps can be taken:
- Initial imaging evaluation consists of non-weight-bearing radiographs 2
- If findings on initial radiographs are equivocal, further evaluation is performed with weight-bearing radiographs, CT, or MR imaging 2, 3
- CT imaging provides a comprehensive evaluation of the injury for optimal treatment planning, with resultant decreased long-term patient morbidity 4
- MR imaging can show isolated ligamentous injury and bone marrow edema 5
Imaging Findings
Imaging findings for Lisfranc injury include:
- Diastasis of the base of the first and second metatarsals 4
- The "fleck" sign 4
- Subtle dislocation on lateral and weight-bearing radiographs 5
- Small fractures on computed tomography 5
- Isolated ligamentous injury and bone marrow edema on magnetic resonance imaging 5
Challenges in Diagnosis
Lisfranc injuries can be easily missed, especially if they present in a subtle form 6