CASE
A 19-year-old college football player presents to your outpatient family practice clinic after suffering a right ankle injury during a football game over the weekend. He reports having his right ankle planted on the turf with his foot externally rotated when an opponent fell onto his posterior right lower extremity. He reports having felt immediate pain in the area of the right ankle and requiring assistance off of the field, as he had difficulty walking. The patient was taken to the emergency department where x-rays of the right foot and ankle did not show any signs of acute fracture or dislocation. The patient was diagnosed with a lateral ankle sprain, placed in a pneumatic ankle walking brace, and given crutches.
A high ankle sprain, or distal tibiofibular syndesmotic injury, can be an elusive diagnosis and is often mistaken for the more common lateral ankle sprain. Syndesmotic injuries have been documented to occur in approximately 1% to 10% of all ankle sprains.1-3 The highest number of these injuries occurs between the ages of 18 and 34 years, and they are more frequently seen in athletes than in nonathletes, particularly those who play collision sports, such as football, ice hockey, rugby, wrestling, and lacrosse.1-9 In one study by Hunt et al,10 syndesmotic injuries accounted for 24.6% of all ankle injuries in National Collegiate Athletic Association (NCAA) football players. Incidence continues to grow as recognition of high ankle sprains increases among medical professionals.1,5 Identification of syndesmotic injury is critical, as lack of detection can lead to extensive time missed from athletic participation and chronic ankle dysfunction, including pain and instability.2,4,6,11
Back to basics: A brief anatomy review
Stability in the distal tibiofibular joint is maintained by the syndesmotic ligaments, which include the anterior inferior tibiofibular ligament (AITFL), the posterior inferior tibiofibular ligament (PITFL), the transverse ligament, and the interosseous ligament.3-6,8 This complex of ligaments stabilizes the fibula within the incisura of the tibia and maintains a stable ankle mortise.1,4,5,11 The deep portion of the deltoid ligament also adds stability to the syndesmosis and may be disrupted by a syndesmotic injury.2,5-7,11
Mechanisms of injury: From most common to less likely
The distal tibiofibular syndesmosis is disrupted when an injury forces apart the distal tibiofibular joint. The most commonly reported means of injury is external rotation with hyper-dorsiflexion of the ankle.1-3,5,6,11 With excessive external rotation of the forefoot, the talus is forced against the medial aspect of the fibula, resulting in separation of the distal tibia and fibula and injury to the syndesmotic ligaments.2,3,5,6 Injuries associated with external rotation are commonly seen in sports that immobilize the ankle within a rigid boot, such as skiing and ice hockey.1,2,5 Some authors have suggested that a planovalgus foot alignment may place athletes at inherent risk for an external rotation ankle injury.5,6
Syndesmotic injury may also occur with hyper-dorsiflexion, as the anterior, widest portion of the talus rotates into the ankle mortise, wedging the tibia and fibula apart.2,3,5 There have also been reports of syndesmotic injuries associated with internal rotation, plantar flexion, inversion, and eversion.3,5,11 Therefore, physicians should maintain a high index of suspicion for injury to the distal tibiofibular joint, regardless of the mechanism of injury.
Presentation and evaluation
Observation of the patient and visualization of the affected ankle can provide many clues. Many patients will have difficulty walking after suffering a syndesmotic injury and may require the use of an assistive device.5 The inability to bear weight after an ankle injury points to a more severe diagnosis, such as an ankle fracture or syndesmotic injury, as opposed to a simple lateral ankle sprain. Patients may report anterior ankle pain, a sensation of instability with weight bearing on the affected ankle, or have persistent symptoms despite a course of conservative treatment. Also, they can have a variable amount of edema and ecchymosis associated with their injury; a minimal extent of swelling or ecchymosis does not exclude syndesmotic injury.3
A large percentage of patients will present with a concomitant sprain of the lateral ligaments associated with lateral swelling and bruising. One study found that 91% of syndesmotic injuries involved at least 1 of the lateral collateral ligaments (anterior talofibular ligament [ATFL], calcaneofibular ligament [CFL], or posterior talofibular ligament [PTFL]).12 Patients may have pain or a sensation of instability when pushing off with the toes,5 and patients with syndesmotic injuries often have tenderness to palpation over the distal anterolateral ankle or syndesmotic ligaments.7
Continue to: A thorough examination...