Fri., 10/15/10 Foot & Ankle, Paper #50, 11:31 am OTA-2010
Prospective Intraoperative Syndesmotic Evaluation during Treatment of Ankle Fractures: Stress External Rotation versus Lateral Fibular Stress
Derek G. Dombroski, MD; Paul E. Matuszewski, MD; J. Todd Lawrence, MD;
John Esterhai, MD; Samir Mehta, MD;
University of Pennsylvania, Department of Orthopaedic Surgery,
Philadelphia, Pennsylvania, USA
Purpose: The syndesmosis of the distal tibia-fibula joint is important for stability in the weight-bearing function of the ankle mortise. Disruption of the syndesmosis influences treatment plans in ankle fractures and therefore diagnosis of this injury is important. Accurate diagnosis of a syndesmotic injury often requires intraoperative evaluation with stress imaging. Stressing the ankle can be achieved by one of two methods—stress external rotation and lateral fibular stress. We hypothesized that the method of stress external rotation more accurately reproduces the mechanism of injury and therefore this diagnostic method more likely detects injury to the syndesmosis.
Methods: A prospective evaluation using stress external rotation and lateral fibular stress was performed on 20 ankle fractures with syndesmotic injury at a single institution. These results were compared against unstressed images with normalized measurements of the tibia-fibula clear space, tibia-fibula overlap, and medial clear space.
Results: After normalization of the fluoroscopic measurements, there was no difference in detecting changes in tibia-fibula clear space or tibia-fibula overlap. However, there was a significant difference in detecting medial clear-space widening with stress external rotation. Compared to lateral fibular stress, stress external rotation demonstrated a 35% increase (P < 0.05) in medial clear-space widening. This difference correlates to between 1 and 2 mm difference of additional widening with stress external rotation.
Conclusion: While widening of the medial clear space does not directly indicate injury to the syndesmosis, this change is indicative of mortise instability, which impacts patient outcomes. The difference in widening with stress external rotation was significantly greater than lateral fibular stress and appreciable on standard fluoroscopic views. Stress external rotation radiographs are a more reliable indicator of mortise instability than traditional lateral fibular stress.
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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.