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 increased compressive stresses seen by the tibia increased likelihood of lateral subluxation of the distal fibula incongruence of the ankle joint articulation Associated injuries osteochondral defects (15% to 25%) peroneal tendon injuries (up to 25%) fractures ankle Weber C Weber B other 5th metatarsal base anterior process of calcaneus lateral or posterior process of talus deltoid ligament injury loose bodies Anatomy See complete ligament of ankle Ligaments distal tibiofibular syndesmosis includes anterior-inferior tibiofibular ligaments (AITFL) originates from anterolateral tubercle of tibia (Chaput's) inserts on anterior tubercle of fibula (Wagstaffe's) posterior-inferior tibiofibular ligament (PITFL) originates from posterior tubercle of tibia (Volkmann's) inserts on posterior part of lateral malleolus strongest component of syndesmosis interosseous membrane interosseous ligament (IOL) distal continuation of the interosseous membrane main restraint to proximal migration of the talus 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 distal fibula externally rotates and translates proximally and posterolaterally during plantarflexion, the narrow posterior talus engages the ankle mortise Distal fibula internally rotates and translates distally and anteromedially 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 single best predictor for return to play provocative tests squeeze test (Hopkin's) compression of tibia and fibula at midcalf level causes pain at syndesmosis external rotation stress test pain over syndesmosis is elicited with external rotation/dorsiflexion of the foot with knee and hip flexed to 90 degrees Cotton widening of the syndesmosis with lateral pull on the fibula fibular translation anterior and posterior drawer force to the fibula with the tibia stabilized causes increased translation of the fibula and pain Imaging Radiographs recommended views AP, lateral, mortise view of ankle AP, lateral of entire tibia may show fracture of proximal fibula abnormal lateral tibiofibular ratio is reliable way of diagnosing injury optional views external rotation stress radiograph gravity stress view will help determine competence of deltoid ligament contralateral ankle radiographs may help clarify syndesmosis widening versus normal anatomic variant findings decreased tibiofibular overlap normal >6 mm on AP view normal >1 mm on mortise view increased medial clear space normal less than or equal to 4 mm increased tibiofibular clear space normal <6 mm on both AP and mortise views 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 syndesmotic sprain without diastasis or ankle instability technique delayed weight-bearing until pain free physical therapy program using a brace that limits external rotation outcomes typically display a notoriously prolonged and highly variable recovery period recovery may extend to twice that of standard ankle sprain Operative syndesmosis screw fixation indications syndesmotic sprain (without fracture) with instability on stress radiographs syndesmotic sprain refractory to conservative treatment syndesmotic injury with associated fracture that remains unstable after fixation of fracture outcomes excellent functional outcomes if syndesmosis is accurately reduced often requires removal syndesmosis fixation with suture button indications same as for screw fixation technique fiberwire suture with two buttons tensioned around the syndesmosis may be performed in addition to a screw outcomes early results promising with some showing earlier return to activity when compared to screw fixation does not require removal 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 screw material no difference between stainless-steel and titanium screws bioabsorbable screws with similar outcomes number of cortices no difference between 3 or 4 cortices number of screws fixation with two screws is preferable position of foot during fixation a recent study challenges the principle of holding the ankle in maximal dorsiflexion to avoid overtightening postoperative typically non-weight-bearing for 6-12 weeks may prolong if screw breakage is a concern Complications Posttraumatic tibiofibular synostosis incidence ~10% after Weber C ankle fractures treatment surgical excision reserved for persistent pain that fails to respond to nonsurgical management ossification must be "cold" on bone scintigraphy prior to removal Prognosis Missed injuries may result in end-stage ankle arthritis Excellent functional outcomes if syndesmosis is anatomically reduced