Instability of the distal tibiofibular syndesmosis after bimalleolar and trimalleolar ankle fractures.

We studied the late results after bimalleolar and trimalleolar ankle fractures in thirty-four patients after an average follow-up of four years. Twenty-one patients had had open reduction and internal fixation of the medial malleolus only and thirteen, internal fixation of both the medial malleolus and the lateral malleolus. Twenty-four lesions were supination-external rotation fractures; six, pronation-external rotation; and four, supination-adduction fractures. All initial and post-reduction roentgenograms were evaluated, and the patients were re-evaluated two to seven years after fracture. Re-evaluation included physical examination as well as standardized and stress roentgenograms of both ankles. Criteria were developed for measuring the width of the syndesmosis and assessing the late roentgenographic, subjective, and objective results, as well as any late instability of the syndesmosis and osteoarthritis. Significant correlations were found between: (1) the adequacy of the reduction of the syndesmosis and late arthritis, (2) the adequacy of the initial reduction of the syndesmosis and the late stability of the syndesmosis, (3) the late stability of the syndesmosis and the final outcome, and (4) the adequacy of the reduction of the lateral malleolus and that of the syndesmosis. Based on the findings in this small series and on the evidence published in the literature, we concluded that adequate reduction of the syndesmosis is necessary to achieve a stable ankle following supination-external rotation and pronation-external rotation fractures of the ankle, and that the reduction of the syndesmosis will be unsatisfactory if the lateral malleolus is not well reduced.