Syndesmotic Anatomy as a Risk Factor for Syndesmotic Injury and Syndesmotic Malreduction

Abstract

Category: Trauma Introduction/Purpose: The anatomy of the syndesmosis is variable, yet little is known on the correlation between morphology and the risk of syndesmotic disruption and malreduction with operative fixation. The study aims at (1) comparing the bony anatomy of the syndesmosis in patients who sustained a high fibular fracture with syndesmosis disruption and that of the non-injured population and (2) at identification of certain anatomical features correlating with syndesmotic malreduction. Methods: For the first research question, the CT examinations of 75 patients who sustained a high fibular fracture with syndesmosis disruption and a control group of 75 patients with unrelated foot problems and without ankle pathology were compared. For the second research question, the bilateral postreduction ankle CTs of 72 patients were analyzed. Incisura depth, fibular engagement into the incisura and incisura rotation (Figure) of the injured patients were compared with those of uninjured controls and correlated with degree of syndesmotic malreduction in the coronal plane, sagittal plane, and rotational malreduction. Results: With the median values of the control group as cutoff there were 71% shallow, 71% disengaged and 77% retroverted syndesmoses in the injury group. The differences between the groups were statistically significant for every measure (P .0001). Clinically relevant syndesmosis malreduction in coronal plane, sagittal plane and rotation affected 8.3; 27.8; and 19.4% of, patients, respectively. The syndesmoses with a deep incisura and the fibula not engaged into the tibial incisura were at risk of overcompression (P< .05). Syndesmosis with an anteverted incisura were at risk of anterior fibular translation and those with a retroverted incisura were at risk of posterior fibular translation (P< .05). Conclusion: Patients with a shallow, disengaged and retroverted bony configuration of the tibial incisura at the syndesmosis are overrepresented among patients with syndesmotic disruption. Intraoperative overcompression of the syndesmosis is significantly more common in patients with a deep and less engaged incisura. Anteversion of the incisura correlates with anterior displacement of the fibula while retroversion of the incisura is correlated with posterior fibular displacement. Knowledge of the individual incisura morphology could be helpful when planning and performing reduction of an unstable syndesmosis.