Extremity CLET Practice Exam

Midfoot instability from disruption of the tarsometatarsal joints is called a Lisfranc injury. This injury involves the joints where the bases of the metatarsals meet the tarsal bones, and it can be purely ligamentous or include fracture-dislocations. The second metatarsal base often acts as a keystone, so disruption can cause the midfoot to widen or the metatarsals to become misaligned with the tarsal framework. Recognizing it is crucial because instability in this region can be easily missed on initial imaging yet lead to chronic pain and arthritis if not treated. Mechanistically, a planted foot subjected to an axial load or rotational force commonly produces this pattern. Look for radiographic clues like widening between the first and second metatarsal bases, misalignment of the tarsometatarsal joints, or a fleck sign from Lisfranc ligament avulsion. Other terms refer to different areas or patterns: a Chopart injury involves hindfoot joints (talonavicular and calcaneocuboid), a dislocation at the tarsometatarsal joints is a component of a Lisfranc injury but the broad, widely used label is Lisfranc injury, and a fracture at the base of the fifth metatarsal is a different injury altogether.