Fractures of the Malleolus with Syndesmotic

7 Fractures of the malleolus associated with syndesmotic injuries are common. Diagnosis of the syndesmotic injury often is missed and requires stress testing. An initial stable syndesmosis on x-ray may get displaced in later x-ray and a high suspicion Index can prevent one from missing this injury. Figure 1 and 2. Accurate reduction and stable fixation of the syndesmosis are critical to outcomes. Unstable syndesmosis is particularly prone to malreduction including translation, rotation, and overcompression. Knowledge of the technical details regarding intraoperative reduction methods and reduction assessment can minimize the risk of syndesmotic malreduction and improve patient outcomes. Figure 3. Syndesmosis is a complex of ligaments that joins the distal fibula to the distal tibia at the level of the ankle joint. Four main ligaments contribute to the syndesmotic complex: the anterior-inferior tibiofibular ligament (AITFL), the posterior-inferior tibiofibular ligament (PITFL), the transverse ligament, and the interosseous ligament. The AITFL is situated obliquely between the anterolateral tibial (Chaput) tubercle and the anteromedial distal fibula. The PITFL connects the posterolateral tibial (Volkmann) tubercle to the posteromedial distal fibula. The transverse ligament represents a deep, thickened zone of the distalmost portion of the PITFL and functions like a labrum, deepening and stabilizing the tibiotalar joint. The PITFL and associated transverse ligament provide nearly half of the overall syndesmotic strength.1 The interosseous ligament is the distal aspect of the tibiofibular interosseous membrane and joins the tibia to the fibula several centimeters above the ar ticular surface.2 A concavity of variable depth and shape known as the incisura fibularis is located at the posterolateral aspect of the distal tibia.3 The distal fibula fits into this structure, which provides a small amount of bony support to this ar ticulation. However, without the ligamentous stability provided by the syndesmosis, the articulation is rendered unstable to physiologic stresses. In the normal ankle, the stabilizing ligaments of the syndesmosis provide a small amount of elasticity, allowing physiologic motion at the distal tibiofibular joint. With ankle dorsiflexion, the wider anterior talar body rotates into the mortise, requiring posterolateral and proximal translation of the fibula, as well as external rotation.4 Overall fibular displacement is normally approximately 1 to 2 mm through the entire ankle range of motion. The position of the fibula within the incisura and its relative stability are critical for maintenance of ankle mor tise congruity and normal distributionof tibiotalar car tilage forces, minimizing the risk of posttraumatic ar throsis. Because multiple individual structures contribute to distal tibiofibular joint stability, pathological instability presents along a spectrum, depending on the number and severity of structures injured. An untreated syndesmotic