A 21 year old otherwise healthy female presents to the ED after an MVC. She reports that she was driving when the car was hit in traffic. During your physical exam, you notice the finding below. An X-ray of the foot is negative for fracture. What is the best test to evaluate this injury?

Image from Orthobullets

A. Weight Bearing Xray

B. CT

C. CTA

D. No further testing is necessary 

Answer: B. Plantar ecchymosis in the setting of a concerning traumatic mechanism is concerning for a tarsometatarsal joint complex injury, also known as a Lisfranc injury. These commonly occur when an axial load is applied to a plantar flexed foot, as may be a driver’s foot on the pedal during an MVC. This injury may be missed on standard X-ray views. Weight bearing X-rays may aid diagnosis but they are ultimately less sensitive than CT. Missed Lisfranc injuries typically have poor outcomes with significant functional limitations and chronic pain. Remember that the dorsalis pedis artery can be transected with a Lisfranc so always check the DP pulse!

See a Lisfranc on XR here: https://emdaily.cooperhealth.org/content/board-review-orthopedics