A56-year-old woman presents with left foot pain and swelling. She claims she was wearing high-heeled sandals, and stepped off a curb, twisting her foot. On exam, she has marked midfoot tenderness and swelling.
What is your diagnosis, and how would you treat this condition? Continued on p. 12.
Lisfranc injuries are commonly undiagnosed and associated with impaired foot biomechanical function that can lead to severe debilitating pain. As many as 20 percent of these injuries are missed on initial presentation to the emergency department. (Am J Emerg Med 2001;19:71.)
The Lisfranc joint is at the junction between the mid- and forefoot at the tarsometatarsal junction. Named after Jacques Lisfranc de Saint-Martin, a surgeon in Napoleon's army, a Lisfranc injury is a term used to describe everything from a sprain to a complete tarsometatarsal disruption. (Phys Sportsmed 2010;38:119.) The midfoot is bound together by clever construction. The proximal second metatarsal is tightly enveloped at the base by the first (medial), second (intermediate), and third (lateral) cuneiform bones essentially locking the tarsometatarsal complex. The relationship between the proximal first and second metatarsal joint, on the other hand, is relatively weak, with no ligamentous attachments. The Lisfranc ligament acts as the primary stabilizer (between the proximal second metatarsal head and the medial cuneiform bone) of all the cuneiform bones and the second metatarsal joint.
In approximately 20 percent of patients, this ligament has two separate bands, dorsal and plantar. Direct impact (motor vehicle crash) or twisting forces on the midfoot (athletes who plant and turn) can cause the complex to rupture, resulting in a fracture at the base of the second metatarsal and dorsal displacement of the fracture fragment with collapse of the metatarsals because of loss of the transverse and longitudinal foot arch. (J Bone Joint Surg Am 2007;89:2225.) A branch of the dorsalis pedis artery dives deep under the Lisfranc ligament to form the arcus plantaris artery, which is at risk when this complex is disrupted.
Lisfranc fractures are rare, and account for only 0.2 percent of all fractures. (J Bone Joint Surg Br 1982;64:349.) They tend to be more common in athletes and men. Diabetic patients with distal neuropathy are also at risk to chronic torquing and sprain of the midfoot. Low-energy mechanisms account for approximately a third of injuries, with remaining ones related to motor vehicle crashes, falls from height, and industrial accidents. (J Am Acad Orthop Surg 2010;18:718.)
Patients with a Lisfranc injury typically have midfoot pain and swelling; some may have eccymosis on the plantar surface of the affected foot. Some patients may only complain of pain when bearing weight, which may make the diagnosis difficult. On examination, pain is typically exacerbated with passive forefoot abduction and pronation when the examiner's opposite hand holds the hindfoot in a fixed position. For severe injuries such as a fracture dislocation, complete midfoot instability may be appreciated.
The differential diagnosis of a Lisfranc fracture-dislocation is fairly circumscribed, and includes fractures of the other foot bones, compartment syndrome, and rupture of the posterior tibial tendon. The diagnosis of a Lisfranc injury may be extremely challenging because standard foot radiographs may be normal and not reveal the extent of the injury. If there is high clinical suspicion for a Lisfranc injury, AP stress views should be obtained. If the patient is unable to tolerate this maneuver, then noncontrast computerized tomography of the foot is an acceptable alternative. MRI and in some cases bone scan are acceptable alternatives to CT, but emergent diagnostic imaging is not typically warranted in the ED. (J Bone Joint Surg Am 2009;91:892.)
First- and second-degree sprains are from partial Lisfranc ligament disruption, and are associated with normal x-rays but not with midfoot instability. Instability and diastasis between the first and second metatarsal greater than 2 mm, with no fracture, is considered a third-degree sprain. (Clin J Sport Med 2007;17:311.)
Isolated Lisfranc sprains are possible but rare because the force required to disrupt the Lisfranc ligament often causes direct traumatic forces at the base of the second metatarsal, resulting in fracture. Stable nondisplaced fractures may be treated with conservative management. Six weeks in a non-weight-bearing short-leg cast may be indicated, with transition to a walking cast with pain as tolerated. (Wheeless' Textbook of Orthopaedics;http://www.wheelessonline.com.) For patients with minimally displaced injuries (less than 2 mm compared with the opposite uninjured foot and less than 15 deg of talometatarsal angulation), controversy currently exists about optimal treatment. Manual closed reduction and casting versus operative repair (internal fixation with pins or screws) are considered current therapeutic options. Operative repair is recommended for all unstable and displaced Lisfranc injuries. (J Am Acad Orthop Surg 2010;18:718.) Patients with significant swelling, open injuries, or vascular compromise may require delayed operative repair. After surgery, patients can be non-weight-bearing up to three months, but six to eight weeks is more common.
Emergency physicians should discuss patients diagnosed with a Lisfranc injury with an orthopedic specialist to determine if immediate reduction should be attempted rather than expectant urgent outpatient management for possible operative consultation or casting. Either way, ED patients should be placed in a posterior lower extremity splint, with instructions not to bear weight, crutches, ice therapy, elevation, and analgesia with nonsteroidal mediations (if no contraindications).
Unrecognized Lisfranc injuries can have serious complications, including foot compartment syndrome, flat foot deformity, and post-traumatic midfoot arthritis (most common, occurring in 50% of cases). (Wheeless' Textbook of Orthopaedics;http://www.wheelessonline.com; -Injury 2007;38:856.)
This patient was evaluated by the orthopedist in the ED, and scheduled for outpatient surgical repair, the result of which is shown in the x-ray at right.
Thanks to Stacy Trent, MD, for the radiographic images.
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