Incisura Morphology as a Risk Factor for Syndesmotic Malreduction

The goal of this study was to objectively assess if rotational or translational syndesmotic malreduction is associated with certain syndesmotic morphologies. Prior studies based on subjective assessment of syndesmotic morphology and reduction have not shown any difference between groups.

Thirty-five prospectively recruited patients with operatively treated syndesmotic injuries were recruited at an Urban Level I Trauma Center. Patients underwent postoperative bilateral computed tomographic (CT) scans of the ankle to assess incisura depth and syndesmotic reduction. The uninjured extremity was used as a control. Side-to-side differences of syndesmotic reduction were measured at several anatomic points and compared to the incisura depth.

There was a significant correlation between more shallow syndesmoses and increased anterior translation of the fibula in the incisura (r = -0.63, P ≤ .001). Six of 8 patients with "shallow" (≤2.5 mm) incisura were anteriorly malreduced greater than or equal to 1.5 mm compared to the contralateral ankle. The anterior malreduction rate in those with a shallow incisura was significantly greater than in the "non-shallow" patients (P < .001). There were 9 patients with incisurae greater than or equal to 4.5 mm deep. Five of the "deep" patients had posterior malreductions greater than or equal to 1.5 mm. The posterior malreduction rate in the "deep" group was significantly greater than the "non-deep" patients (P = .02). There was a significant correlation between increasing syndesmotic depth and increased malrotation (r = .46, P = .01).

Syndesmotic morphology was found to be associated with specific malreduction patterns. Shallow syndesmoses were correlated with anterior fibular malreduction, and were less likely to be malrotated. Conversely, deep syndesmoses predisposed to posterior sagittal plane and rotational malalignment. Preoperative CT scans that assess the syndesmosis morphology may allow surgeons to alter reduction strategies to avoid syndesmotic malreduction.

Level III, retrospective cohort study.