An Assessment of Normal Tibiofibular Anatomy on Lateral Fluoroscopy

Abstract

Background: Intraoperative identification of syndesmotic malreduction during ankle fracture fixation can be challenging. Prior studies describe the normal tibiofibular relationship on anteroposterior and mortise views to aid assessment, but the normal anatomic variation on the lateral view has not been well defined. The aim of this study was to describe the normal anatomy of the lateral radiographic view of the ankle, focusing on the relative position of the fibula and tibial plafond. Methods: We retrospectively identified consecutive adults undergoing ankle fracture open reduction internal fixation in 2011-2018. Two independent observers assessed the tibiofibular relationship on perfect lateral images of the uninjured side. Measurements were made in pixels, converted into millimeters using published parameters, and averaged for analysis. Reliability was calculated using Pearson correlation coefficients. Results: Of 751 cases of adult ankle fracture fixation identified, 50 patients had perfect lateral images of the contralateral side. In 11 patients (22%), the posterior border of the fibula intersected precisely at the posterior edge of the tibial plafond. Ten patients (20%) had anterior intersections, whereas 29 (58%) had posterior intersections. The intersection was within ±2 mm of the plafond edge in 27 patients (54%). Intrarater reliability was 0.86 and 0.93. Interrater reliability was 0.88. Conclusion: In most ankles, the posterior border of the fibula intersects the posterior extent of the tibial plafond within 2 mm. If more than 2 mm away, one should query malreduction, especially if anterior. This method of intraoperative assessment may decrease the occurrence of syndesmotic malreduction. Level of Evidence: Level III, comparative series.