邢丹      　宋东辉     　马信龙    　马剑雄

Syndesmosis is a kind of fibrous articulation in which the opposing joint surfaces are united by ligaments. The distal tibiofibular syndesmosis consists of a complex of ligaments that provide stability to the joints. The anterior, posterior and transverse tibiofibular ligaments together with the interosseous ligament form the distal tibiofibular syndesmosis. Syndesmosis injuries are rare, but very debilitating and frequently misdiagnosed. It is estimated that 10% of all ankle fractures and 20% of operatively treated ankle fractures are accompanied by syndesmotic injury. Distal tibiofibular syndesmotic ligament injury can also occur in isolation mostly due to an extorsion or in association with damage to the lateral ankle ligaments. Syndesmotic injury leads to subsequent mortise instability and should be treated with syndesmotic stabilization to prevent long-term complications of ankle joint. Immediate reconstruction of the unstable syndesmosis is indicated, because a delay could expedite the development of degenerative arthritis. However, the precise diagnosis of distal tibiofibular syndesmotic ligament injury is critically difficult. The distinction should be made between syndesmotic ligament disruption and real syndesmotic instability. Radiographic measures including tibiofibular overlap, tibiofibular space, medial and superior space are of little value in detecting distal tibiofibular syndesmosis, because all these parameters depend on the rotation of the ankle joint. CT and MRI could also be used in detecting syndesmotic disruption in patients with distal tibiofibular syndesmotic ligament injuries. Intra-operative stress testing is essential in the diagnosis for syndesmotic injuries. Although ankle arthroscopy is a more sensitive method than radiography, it is more invasive and not all surgeons have the expertise to perform ankle arthroscopy. Therefore, there has no “gold standard” diagnostic measure in testing the instability of distal tibiofibular syndesmotic ligament injuries. Furthermore, the need for distal tibiofibular syndesmotic fixation is not fully clear despite the abundance of literature concerning the treatment of ankle fractures and isolated syndesmotic injuries. Fixation using screw is widely preferred in the current concepts of surgical treatment. At present, the following items in treating distal tibiofibular syndesmotic ligament injuries are still in the arguments: location of the screw fixation, number of the screws used in the fixation, 3 or 4 cortex penetrated, diameter of the screw and the foot position. Therefore, the purpose of the present review article is to summarize the evidence about the diagnosis and treatment of instable distal syndesmotic injuries.