The Trans-Syndesmotic Axis in Relation to the Distal Anterior Medial Tibial Cortex

CATEGORY: Ankle INTRODUCTION/PURPOSE: Gardner et al. (2006) reported that over 50% of operative syndesmoses are malreduced. The functional consequence of syndesmotic malreduction at two years was reported in 2012. Miller et al. in 2013, found that the 15° and 30°clamp positions caused fibula external rotation and over compression of the syndesmosis joint. The 0° medial clamp position which was in line with the trans-syndesmotic axis (TSA) did not negatively impact fibular reduction as did the other two posterior clamp positions. The purpose of this study is to identify the medial exit point of the TSA on the tibia. We hypothesized that the TSA on the medial side of the ankle would be a constant distance from the medial anterior tibial cortex. METHODS: Fifty consecutive CT scans of uninjured ankles were reviewed from our image archive system. On an axial 2- dimensional reformatted image proximal to the ankle joint that included the entire incisura a line was drawn connecting the anterior and posterior limits of the incisura of the tibia. A second line was then drawn at 90 degrees at the midpoint of the first line and extended medially. RESULTS: The average distance of the medial TSA exit point from the anterior edge of the distal medial tibia was 2.9 mm (Range 0- 9 mm, standard deviation 2.03 mm). The average anterior to posterior length of the medial distal tibia was 23.6 mm (Range 16-30, standard deviation 3.01 mm). CONCLUSION: Syndesmosis reduction clamp placement may first involve identifying the TSA based upon the anterior edge of the distal medial tibia. This region may be used to locate the TSA for optimal medial clamp placement. This study provides a foundation for future clamp placement investigations.