Evaluation of Syndesmosis Reduction on CT Scan

Computed tomography (CT) imaging has traditionally been considered the gold standard for evaluation of syndesmostic reduction, but there is no uniformly accepted method to assess reduction. The aim of this study was to evaluate the intra- and interobserver reliability of published measurement techniques for evaluation of syndesmotic reduction on weightbearing CT scan (WBCT) in hopes of determining which method is best.

Medical records were reviewed to identify patients who underwent operative stabilization of unilateral syndesmotic injuries. Exclusion criteria included patients younger than 18 years, ipsilateral fractures extending to the tibial plafond, any contralateral ankle fracture or syndesmotic injury, and body mass index greater than 40 kg/m². Twenty eligible patients underwent WBCT evaluation of both ankles at an average of 3 years after syndesmotic fixation. The anatomic accuracy of syndesmotic reduction was evaluated by 2 observers using axial CT images at a level 1 cm proximal to the tibial plafond using 9 previously published radiological measurement techniques. Inter- and intraobserver reliability were assessed for each evaluation method.

The syndesmotic area calculation showed the highest interobserver reliability (0.96), the highest intraobserver reliability for observer 2 (0.97), and the second highest intraobserver reliability for observer 1 (0.92). Fibular rotation had the second highest interobserver reliability in our results (0.84), with intraobserver reliability of 0.91 and 0.8 for first and second observers, respectively. The intraobserver reliability of the side-by-side method was 0.49 and 0.24 for the first and second observers, respectively, and the interobserver reliability was 0.26.

Qualitatively assessing syndesmotic reduction via side-by-side comparison with the uninjured ankle had the least intra- and interobserver reliability and should not be relied on to determine syndesmotic reduction quality. In contradistinction, syndesmotic area calculation demonstrated the highest reliability when evaluating syndesmotic reduction, followed by fibular rotation. Given that syndesmotic area measurement techniques are not readily available on standard image viewers, technologically updating image viewers to allow such calculation would make this approach more accessible in clinical practice.

Level IV, case series.