Effect of Posterior Malleolus Fracture on Outcome After Unstable Ankle Fracture

Background: The purpose of this article was to compare clinical and functional outcomes of surgically treated trimalleolar fractures with bimalleolar and unimalleolar ankle fractures. Methods: A prospective database was established to enroll all unstable ankle fractures treated operatively at our institution from October 2000 to July 2005. Demographic data on 456 patients, who sustained an unstable fracture of the ankle and were treated surgically, were entered into a database, and the patients were prospectively followed up. Of these 309 patients who had at least 1-year follow-up, 54 patients sustained an ankle fracture with involvement of the posterior malleolus. Two hundred fifty-five patients had an ankle fracture without involvement of the posterior malleolus. Of the 54 posterior malleolus fracture, 20 underwent fixation of the posterior malleolus. All patients were followed up at 3 months, 6 months, and 12 months after surgery and assessed functionally with Short Musculoskeletal Function Assessment and American Orthopaedic Foot and Ankle Society Scores. Results: There was no difference in age, sex distribution, or American society of anesthesiologists classification or incidence of diabetes between the two groups. At 1-year follow-up, all patients improved their function and pain status. Using the American Orthopaedic Foot and Ankle Society, patients with posterior malleolus fracture were significantly worse both for total score (p = 0.004) and pain function (p = 0.002). At 2-year follow-up, there was no significant difference in a smaller group of patients (41 patients). Using the Short Form-36, there was a significant difference seen with vitality and social function subgroups at 1 year. Using the Short Musculoskeletal Function Assessment, there was a significant difference at 1 year for dysfunction index (p = 0.04) for the trimalleolar group. Conclusion: Most patients after unstable ankle fractures treated surgically do well; however, some patients continue to have some pain and dysfunction at 1 year. There was a significant difference in outcomes comparing patients with unstable ankle fractures associated with and without posterior malleolus fractures. The presence of a posterior malleolus fracture may indicate higher energy of injury, and it does seem to result in worse outcomes at 1 year, but this seems to even out over time as was seen at 2-year follow-up in a smaller group of patients.