Can We Tell if the Syndesmosis Is Reduced Using Fluoroscopy?

OBJECTIVE: To evaluate the ability of surgeons to determine whether the fibula is reduced in the sagittal plane in relation to the tibia based on the fluoroscopic images by comparison with the known normal for both the ipsilateral and contralateral ankles.
METHODS: Perfect lateral radiographs of both ankles were obtained in 7 cadaveric specimens. The fibula was translated 2.5 and 5 mm in the anterior and posterior directions. Four orthopaedic trauma-trained surgeons were presented with a fictitious case consisting of a "normal" image, followed by 10 randomly selected images from both ankles, and were asked to determine whether the fibula was reduced, or displaced anteriorly or posteriorly. The ability of the surgeons to identify displacement and interobserver reliability was assessed.
RESULTS: The surgeons were better able to identify malreduction than reduction (negative predictive value (NPV) 95% ipsilateral, 85% contralateral). The overall sensitivity for reduction was 94% for the ipsilateral ankle, but only 68% for the contralateral ankle. Anterior displacement and greater magnitudes of displacement were most easily diagnosed. All reviewers had the most difficulty with 2.5 mm of posterior displacement. The intraobserver agreement was excellent for anterior displacement and 5 mm of displacement in either direction (kappa = 0.71/0.75). Surgeons who routinely used the contralateral lateral radiograph were more accurate.
CONCLUSIONS: Although it is unknown how much translational displacement of the syndesmosis is acceptable, it seems that the experienced surgeon will be able to reduce the joint within 2.5 mm and that fluoroscopic comparisons to the normal ankle are helpful in determining malreduction.