The midfoot is divided into two columns, with the medial column containing the navicular, cuneiforms, and the first three tarsometatarsal joints; the lateral column contains the cuboid and fourth and fifth tarsometatarsal joints (Figure 277-1). The midfoot is a vital bridge between the hindfoot and the forefoot. Injuries to the midfoot have the potential to dramatically affect an individual's daily function, including the ability to stand and walk. Untreated midfoot injuries in diabetics can lead to the development of Charcot's foot (collapse of the mid-foot arch) and lifelong complications with ambulating.8
The cornerstone of mechanism, diagnosis, and treatment of Lisfranc injuries lies in the anatomy of the second metatarsal and the Lisfranc ligament, which runs between the lateral base of the medial cuneiform and the medial base of the second metatarsal. Its strength exceeds that of the plantar ligament construct by severalfold.9 Lisfranc injuries range from sprains to fracture-dislocations, with concurrent fractures of the hind and forefoot being relatively common, especially fractures of the second metatarsal. The usual mechanism of injury for sprains is a low-velocity indirect force, whereas plantar-flexion with an axial load (such as strenuous jumping over an obstacle) is seen in more significant injuries. Sports injuries (specifically football) and motor vehicle crashes are common situations for these injuries.10,11
Pain elicited by torsion of the midfoot raises suspicion for a Lisfranc injury. Also, injuries about the tarsometatarsal joint, with pain on passive dorsi- or plantarflexion of the foot, should result in a specific evaluation of the midfoot for a Lisfranc injury. Radiographic studies should include at minimum bilateral weight-bearing anteroposterior (when tolerable), lateral, and 30-degree oblique views of the foot. Bony displacement of 1 mm or greater between the bases of the first and second metatarsals is considered unstable. CT imaging is the ideal imaging study for this injury.12 It provides better delineation of bony structures and diagnoses occult fractures or subluxations that can be missed on plain radiographs (Figure 277-6).
A. Radiograph of Lisfranc injury. B. CT of Lisfranc injury. Note the metatarsal bones are fractured (arrow) and displaced from the tarsus. [Image used with permission of Robert DeMayo, MD.]
Lisfranc injuries have multiple classification systems.10 The Nunley classification groups low-energy ligamentous injuries by diastasis and preservation or loss of arch height: type I are nondisplaced, type II involve diastasis between the first and second metatarsal heads, and type III involve diastasis with loss of arch height.11
Treatment of a nondisplaced injury (<1 mm between the bases of the first and second metatarsals) is with a non–weight-bearing splint, rest, ice, and elevation. Orthopedic reevaluation is usually scheduled within 2 weeks when repeat imaging will likely be obtained and a cast will likely remain on for an additional 4 weeks. At 6 weeks, gradual progressive weight bearing can be attempted.
Displaced Lisfranc injuries are unsTable and require orthopedic consultant in the ED and anatomic reduction.13 Whether the reduction is open or closed depends on the degree of the injury and is determined by the orthopedic consultant. Surgical options are variable and range from open reduction and internal fixation to primary arthrodesis.14 Compartment syndrome is an acute complication of significant Lisfranc injuries (see the chapter titled "Compartment Syndrome").
Navicular fractures are typically caused by a direct blow or axial loading. Avulsion injuries can also occur with a pulling or rotational force. On physical examination, tenderness and ecchymosis are found about the navicular. Imaging includes bilateral weight-bearing anteroposterior, lateral, and oblique radiographs. CT is best for evaluating the talonavicular joint surfaces. The goals of treatment are maintenance of anatomy and restoration of articular congruity. Nondisplaced fractures should be treated in a non–weight-bearing short leg cast for 6 to 8 weeks, with orthopedic reevaluation in approximately 2 weeks. Orthopedic consultation in the ED is usually required for displaced, and therefore unstable, fractures, to determine the management plan. Given that the central part of the navicular bone is avascular,15 complications include avascular necrosis, nonunion, and instability, all of which can lead to a flatfoot deformity.
The cuboid articulates with the calcaneus and the fourth and fifth metatarsals. Plantarflexion and abduction is the most common mechanism of injury. Imaging includes bilateral weight-bearing anteroposterior, lateral, and oblique radiographs. CT may be helpful. Nondisplaced fractures are treated with a short leg cast and initial non–weight-bearing status. Comminuted injuries are treated with surgery. Complications include foot instability and joint arthrosis.
The cuneiforms all articulate with the navicular. Isolated cuneiform injuries are very rare, but especially with a high-energy mechanism of injury, cuneiform fractures can coexist with other fractures of the foot. Imaging studies are the same as for the other bones of the midfoot. Treatment depends on which bone is injured: medial cuneiform injuries are typically treated with surgery, whereas closed reduction usually suffices for the middle and lateral cuneiform bones.