Abstract
Introduction
Previous studies have demonstrated the need of accurate reduction of ankle syndesmosis. Measurement of syndesmosis is difficult on plain radiographs. Recently, a difference of 2mm in anterior and posterior measurements at incisura of the inferior tibio-fibular joint on CT has been described as a measure of malreduction (depicted as ‘G’ for ease of description). Our practice changed towards routine post operative bilateral CT following syndesmosis fixation to assess the reduction and identify potential problems at an early stage. The aim of this primarily radiological study was to determine if the use of bilateral cross sectional imaging brings additional benefit above the more conventional practice of unilateral imaging.
Method
Between 2007 and 2009, nineteen patients with ankle fractures involving the syndesmosis were included in the study group who had bilateral CT post operatively. The values of ‘G’ and the mean diastasis (MD) were calculated, representing the average measurement between the fibula and the anterior and posterior incisura.
Results
When compared to the normal side, eight out of nineteen (42%) cases were found to have a residual diastasis even after fixation across the syndesmosis, However, if a standard value of G(2mm) was used for the injured leg only, all of the nineteen cases would have abnormal values of ‘G’ following reduction. The value of G for the injured side was poorly correlated with the mean inter-limb diastasis (MD, R=0.23).
Discussion
Our study has clearly demonstrated the need for individualising the assessment method to guide surgeons and radiologists prior to revision surgery. A standard value of ‘G’ of 2mm as the normal limit cannot be applied universally as apparent from the data presented in this study.
