Limitations of Standard Fluoroscopy in Detecting Rotational Malreduction of the Syndesmosis in an Ankle Fracture Model

Background: When treating ankle fractures with associated syndesmosis injury, failure to anatomically reduce the syndesmosis may lead to poor outcome. While shortening and posterior subluxation of the distal fibula are readily detected by intraoperative fluoroscopy, it is unclear how well malrotation can be assessed. The ability of fluoroscopy to detect rotational malreduction of the fibula was the subject of this study. Materials and Methods: Distal fibula fractures with complete syndesmotic injury were produced in ten cadaveric ankles. Two Kirschner wires were used to fix the fibula in neutral (0 degrees), 10 to 30, degrees of external rotation (ER), and 10 degrees to 30 degrees of internal rotation (IR). Using C-arm fluoroscopy tibio-fibular clear space and tibio-fibular overlap in the AP and mortise views, and posterior fibular subluxation in the lateral view were measured to assess reduction of the syndesmosis. Results: The radiographic indices were able to detect as little as 10 degrees of IR but were within their normal range in up to 30 degrees of ER. When assessing for a 2mm difference compared to the intact ankle, sensitivity of all indices were low after more than 15 degrees ER, but high and clinically useful after more than 15 degrees of IR. Conclusion: Radiographic indices for syndesmosis disruption could not detect ER malreduction of the syndesmosis of up to 30 degrees. Clinical Relevance: In the setting of ankle fractures with syndesmosis disruption, fixing the fibula in as much as 30 degrees of external rotation may go undetected using intraoperative fluoroscopy alone.