Mortise view radiograph of left ankle
Lateral view radiograph of left ankle
A 23-year-old man complains of left ankle pain after falling awkwardly during a football game. He is unable to bear weight on the ankle. Mortise and lateral view radiographs are obtained.
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Ankle injuries represent nearly 30% of all sports injuries.1 Syndesmotic injuries occur with many ankle sprains and 23% of all ankle fractures.2 The ankle syndesmosis — the articular connection between the distal tibia and fibular — is stabilized by 4 main ligaments. These ligaments include the anterior inferior tibiofibular ligament, the posterior inferior tibiofibular ligament, the inferior transverse ligament, and the interosseous ligament. The ankle mortise, or syndesmosis, normally expands and contracts by 1 mm to 2 mm during ankle motion. The anterior aspect of the talar dome is wider than the posterior aspect so the mortise widens with dorsiflexion.3,4
The common mechanism of injury for syndesmotic injuries includes a forceful hyper-dorsiflexion or external rotation of the ankle. Disruption of the ankle syndesmosis results in abnormal contact pressures on the talus. Articular surface congruency is critical for normal function and stability of the ankle.
The key radiographic sign for a syndesmotic injury includes medial clear space widening, as seen in the mortise view radiograph of the case patient. Medial clear space widening is an indication for surgical fixation, with or without an associated fracture.
For this patient, the patient’s lateral malleolar fracture was fixed first during surgical fixation. A clamp was then placed to compress the tibia and fibula together, which reduces the syndesmosis. Once reduced, two tri-cortical screws were placed from lateral to medial to hold the reduction.
Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor-in-chief of the Journal of Orthopedics for Physician Assistants (JOPA).
- Waterman BR, Owens BD, Davey S, Zacchilli MA, Belmont PJ. The epidemiology of ankle sprains in the United States. J Bone Joint Surg Am. 2010;92:2279-2284.
- van Heest TJ, Lafferty PM. Current concepts review: injuries to the ankle syndesmosis. J Bone Joint Surg Am. 2014;96:603-613.
- Jones CB, Gilde A, Sietsema DL. Treatment of syndesmotic injuries of the ankle: a critical analysis review. JBJS Reviews. 2015;3(10).
- Karadsheh M. High ankle sprain & syndesmotic injury. www.orthobullets.com. Accessed June 21, 2018.