Fri., 10/5/12 Foot & Ankle, PAPER #46, 10:52 am OTA-2012
Anatomic Reduction of the Syndesmosis: What Values to Trust?
Jonah Hebert-Davies, MD1,2; Marie-Lyne Nault, MD1,2; George Yves Laflamme, MD1;
Stephane Leduc, MD1;
1Hopital du Sacre-Coeur, Montreal, Quebec, Canada
2University of Montreal, Montreal Quebec, Canada
Background/Purpose: Anatomic reduction of the fibula with regard to the tibia has become the goal of treating syndesmotic injuries. Several studies have recently questioned our capacity to do so, implying that malreduction is much more common than originally thought. These studies focus on postoperative CT scans to show wide-ranging variation. Our hypothesis is that there exists a wide range of anatomic variation in the syndesmosis and this might lead to overly critical opinion of postreduction CT scans. The purpose of this study is to first describe and validate radiologic measurements to evaluate the syndesmosis reduction and establish normal values.
Methods: Ankle CT scans of 100 normal ankles were evaluated. The scans were originally done to evaluate patients with foot trauma but without documented ankle trauma. A series of eight measurements was devised based on previously published studies or described by our group. These criteria measure both anterior and lateral position of the fibula and rotation with regard to the tibia. Two independent reviewers evaluated all scans and all measurements were recorded initially. A third evaluator reviewed 30 scans to validate interobserver reliability and measurements were repeated at 6 weeks for intraobserver reliability.
Results: We found that the most reproducible measurement was the ratio of anterior to posterior gaps between tibia and fibula with a mean value of 0.603 and an intraclass correlation coefficient (ICC) of 0.879. This is the normal value and could eventually change with malreduction in rotation or specific anterior (AITFL) or posterior inferior tibiofibular ligament (PITFL) rupture. A mean central lateral distance of 2.8 mm was found and the ICC for that measure was also excellent (ICC = 0.75). A mean rotation index (defined as the angle between both malleoli at ankle level) was of 7.5° with ICC of 0.662. All other results were reproducible with good intra- and interobserver reliability with interclass correlations between 0.61 and 0.746.
Conclusion: Several studies have shown that reduction of the syndesmosis is essential to restore normal ankle mechanics and prevent secondary degenerative changes. Our results show that a significant amount of variability exists in the anatomical position of the syndesmosis. The evaluation criteria developed in the study can give the surgeon a guideline for evaluating postoperative reductions.
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• The FDA has not cleared this drug and/or medical device for the use described in this presentation (i.e., the drug or medical device is being discussed for an “off label” use). ◆FDA information not available at time of printing. Δ OTA Grant.