Uncommon but important Emergency Medicine diagnoses: The Case of the Twisted Foot
Jacqueline MacKay PGY1 FM/EM
Edited by: David Lewis
A Lisfranc injury is a disruption of the tarsometatarsal ligamentous joint complex in the foot. It can occur by high or low energy mechanisms: up to 1/3 of Lisfranc injuries are due to low energy mechanisms such as a fall from standing and these injuries are commonly missed. Accurate diagnosis of Lisfranc injuries at initial presentation is crucial, as delayed definitive management can lead to arthritis, instability, pain, and disability.
The patient will complain of midfoot pain and inability to bear weight on the affected foot. The point of maximal tenderness and swelling will be around the medial midfoot. Dorsal bruising occurs acutely and plantar bruising subacutely. A separation of the first and second toes is called the “gap sign” and is evidence of midfoot abnormality.
Initial imaging is with plain x-rays; comparison with the non-injured foot may be helpful. The medial border of the second metatarsal should align with the medial border of the intermediate cuneiform; interruption of this line signifies Lisfranc injury. Weight bearing views or CT may be necessary if plain films are normal. If there is high clinical suspicion of injury even if initial imaging is negative, immobilization of the foot in a posterior slab and an urgent (within 7 days) referral to orthopedics is necessary.
Pearl: a high index of suspicion is crucial for diagnosis of Lisfranc injuries
(A) Non-weight-bearing dorsoplantar and oblique radiographs appear to be within normal limits. (B) On non-weight-bearing lateral radiograph, extensive soft-tissue swelling and a subtle step-off seen at the tarsal-metatarsal joint are were the only clue to a Lisfranc injury in this patient. (C) On weight-bearing dorsoplantar radiographs, subtle lateral dislocation of the second metatarsal relative to the second cuneiform (arrow) can be seen.
(From Gupta, Wadhwa, Learch, et al.)
References:
Eleftherio K, Rosenfeld P, Calder J. Lisfranc injuries: an update. Knee Surg Sports Traumatol Arthrosc. 2013:21;1434-46.
Wright M, Michelson J. Lisfranc injuries. BMJ. 2013:347;f4561.
Mayich DJ, Mayich MS, Daniels TR. Effective detection and management of low-velocity Lisfranc injuries in the emergency setting: principles for a subtle and commonly missed entity. Can Fam Phys. 2012:58(11);1199-204.
Gupta RT, Wadhwa RP, Learch TJ, et al. Lisfranc injury: imaging findings for this important but often-missed diagnosis. Curr Probl Diagn Radiol, 2008:37(3);115-26.
