Kinematics after Syndesmotic Injury: Assessing the Magnitude of Talus and Fibula Rotation and Displacement

CATEGORY: Ankle; Sports; Other INTRODUCTION/PURPOSE: High ankle sprains, or injuries to the distal tibiofibular syndesmosis, are predictive of long-term ankle dysfunction. Our objectives were to evaluate ankle mortise stability, radiographically, and kinematically, using a cadaveric model with a simulated syndesmotic injury. We also measured the ability of a suture-button system to restore natural joint motion. METHODS: Eight cadaveric specimens underwent serial sectioning of the anterior-inferior tibiofibular (AITFL), interosseous (IOL), posterior-inferior tibiofibular (PITFL), and deltoid ligaments. Specimens underwent external rotation and lateral translation testing after ligament release to obtain kinematic data (using a validated infrared LED motion capture system) and radiographic measurements. We then repeated external rotation and lateral translation testing after implementing a suture-button system. Repeated measures ANOVA with a Bonferroni/Dunn post-hoc test calculated the interspecimen comparisons. RESULTS: Sectioning of each ligament, beginning with the AITFL, significantly increased talar external rotation. After releasing the AITFL and IOL, fibular external rotation increased significantly. Posterior displacement of the fibula began following the release of AITFL. Significant radiographic widening of the medial clear space and the syndesmosis occurred only after the release of the deltoid ligament. Syndesmotic and medial clear space widening was not significantly different from the intact state under lateral translation until after the release of the deltoid ligament. Placement of the suture-button system successfully reduced the medial clear space but was unable to restore the native stability of the ankle joint. CONCLUSION: This project addresses rotational and kinematic changes in the ankle after syndesmotic injury by quantifying the effect of ligamentous disruption on the tibiotalar articulation. The change in joint kinematics may explain why patients with moderate-to-severe syndesmosis injuries take longer to heal and develop long-term dysfunction. Significant talar rotation and posterior fibular displacement occur during external rotation, even with moderate syndesmosis injury, and before the disruption of the deltoid ligament. Stress radiography does not appear to be a reliable indicator of mild or moderate syndesmosis injuries.