summary High Ankle Sprain & Syndesmosis Injuries are traumatic injuries that affect the distal tibiofibular ligaments and most commonly occur due to sudden external rotation of the ankle. Diagnosis is suspected clinically with tenderness over the syndesmosis which worsens with squeezing of the tibia and fibula together at the midcalf. Plain stress radiographs of the ankle are required to diagnosis complete syndesmosis injuries with tibiofibular diastasis. Treatment is nonoperative for syndesmotic sprains without diastasis or ankle instability. Operative management is indicated for patients with diastasis of the tibiofibular joint or injuries with associated fractures. Epidemiology Incidence 0.5% of all ankle sprains without fracture 13% of all ankle fractures Etiology Pathophysiology mechanism of injury most commonly associated with external rotation injuries pathoanatomy external rotation forces the talus to rotate laterally and push the fibula away from tibia may lead to login to view 3 more bullets Associated injuries osteochondral defects (15% to 25%) peroneal tendon injuries (up to 25%) fractures ankle login to view 2 more bullets other login to view 3 more bullets deltoid ligament injury loose bodies Anatomy See complete ligament of ankle Ligaments distal tibiofibular syndesmosis includes anterior-inferior tibiofibular ligaments (AITFL) login to view 2 more bullets posterior-inferior tibiofibular ligament (PITFL) login to view 3 more bullets interosseous membrane interosseous ligament (IOL) login to view 2 more bullets inferior transverse ligament (ITL) Syndesmosis Biomechanics function maintains integrity between tibia and fibula resists axial, rotational, and translational forces motion during dorsiflexion, wider anterior talus engages the ankle mortise login to view 1 more bullet during plantarflexion, the narrow posterior talus engages the ankle mortise login to view 1 more bullet normal gait syndesmosis widens 1mm during gait deltoid ligament indirectly stabilizes the medial ankle mortise Presentation Symptoms anterolateral ankle pain proximal to AITFL may have medial sided ankle tenderness/swelling difficulty bearing weight lateral ankle sprains are often able to bear weight Physical exam palpation syndesmosis tenderness login to view 1 more bullet provocative tests squeeze test (Hopkin's) login to view 1 more bullet external rotation stress test login to view 1 more bullet Cotton login to view 1 more bullet fibular translation login to view 1 more bullet Imaging Radiographs recommended views AP, lateral, mortise view of ankle AP, lateral of entire tibia login to view 2 more bullets optional views external rotation stress radiograph gravity stress view login to view 1 more bullet contralateral ankle radiographs login to view 1 more bullet findings decreased tibiofibular overlap login to view 2 more bullets increased medial clear space login to view 1 more bullet increased tibiofibular clear space login to view 1 more bullet CT indications clinical suspicion of syndesmotic injury with normal radiographs useful post-operatively to assess reduction of syndesmosis after fixation sensitivity and specificity more sensitive than radiographs for detecting minor degrees of syndesmotic injury MRI indications clinical suspicion of syndesmotic injury with normal radiographs sensitivity and specificity lambda sign described as being highly sensitive and specific for detecting syndesmotic injury Treatment Nonoperative non-weight-bearing CAM boot or cast for 2 to 3 weeks indications login to view 1 more bullet technique login to view 2 more bullets outcomes login to view 2 more bullets Operative syndesmosis screw fixation indications login to view 3 more bullets outcomes login to view 3 more bullets syndesmosis fixation with suture button indications login to view 1 more bullet technique login to view 2 more bullets outcomes login to view 2 more bullets Techniques Syndesmotic screw fixation technique two 3.5 or 4.5 mm syndesmotic screws through 3 or 4 cortices placed 2-5 cm above the plafond login to view 9 more bullets postoperative typically non-weight-bearing for 6-12 weeks login to view 1 more bullet Complications Posttraumatic tibiofibular synostosis incidence ~10% after Weber C ankle fractures treatment surgical excision login to view 2 more bullets Prognosis Missed injuries may result in end-stage ankle arthritis Excellent functional outcomes if syndesmosis is anatomically reduced