I would like to use this blog to introduce a term/condition: the “Lisfranc fracture equivalent.”
This new term identifies a patient who has a subtle ligamentous Lisfranc injury that is radiographically aligned within the midfoot keystone. This patient also has the uncommon stigmata of a Lisfranc fracture dislocation, which include: non-first interspace fleck fractures of the tarsometatarsal joints; lesser metatarsal neck fractures (often oblique); and/or a non-displaced cuboid injury/nutcracker fracture.
The Lisfranc fracture equivalent is important because the uncommon stigmata of the Lisfranc fracture alert the specialist that instability of the Lisfranc joint may exist and further medical investigation is warranted to uncover the Lisfranc injury. In this situation, a mechanical fluoroscopic stress exam will uncover the instability. In highly suspicious cases, an evaluation with the patient under anesthesia may be warranted. An unstable Lisfranc joint often requires surgical intervention.
I have excluded the first intermetatarsal space fleck fracture as part of the Lisfranc fracture equivalent because the presence of the fleck fracture is essentially synonymous with the Lisfranc injury and prompts the medical and radiographic workup, and a treatment protocol appropriate for Lisfranc injuries. However, one can probably consider this within the context of the Lisfranc fracture equivalent.
The rationale for distinguishing the Lisfranc fracture equivalent is to bring emphasis to the mechanism of injury so the radiographically obvious stigmata (metatarsal neck fractures, cuboid nutcracker fractures) are not mistakenly considered as stand-alone injuries that may not prompt further workup for instability at the Lisfranc joint. It is possible that immediate weightbearing begins for lesser metatarsal fractures in the face of an undiagnosed Lisfranc injury. This could result in midfoot arthrosis, malalignment and/or other short-term/long-term complications.
The photo at the top demonstrates a situation in which a patient had lesser metatarsal head fractures that were treated with open reduction internal fixation. The Lisfranc injury did not have a workup in this particular case and therefore no surgical intervention for the Lisfranc joint occurred. The image at three months illustrates diastasis at the first interspace from neglecting the Lisfranc injury.
Nonetheless, in my clinical practice, when I am confronted with stigmata of Lisfranc fractures, I initiate a workup to rule out an unstable Lisfranc joint. If the Lisfranc joint is unstable, then surgical intervention of the Lisfranc joint is warranted. If the Lisfranc joint is stable, I often over-treat this and emphasize a non-weightbearing cast. I believe this is preferable given the mechanism of injury that resulted in the stigmata injuries in the first place. This underlies the importance of the term Lisfranc fracture equivalent.
Dr. Blitz is Chief of Foot Surgery and Associate Chairman of Orthopaedics of Bronx-Lebanon Hospital Center. Dr. Blitz may be reached at firstname.lastname@example.org  .