Characteristics of intercalary fragment of posterior malleolus fractures in adults

Abstract

Objective To investigate the incidence of intercalary fragment in adult ankle fractures and analyze the morphological characteristics of intercalary fragment as well as its relationship with the type of posterior malleolus fractures. Methods Data of 247 cases with posterior malleolus fractures from 369 cases of adult ankle fractures who were treated from January 2014 to January 2016 were retrospectively analyzed. The pre-operative X-ray and CT data of the group were analyzed, and the incidence of intercalary fragment was measured. The intercalary fragment was classified by position, size and shape of its morphological features. The posterior malleolus fracture was classified according to Bartonicek classification system. The relationship between type of posterior malleolar fracture and the intercalary fragment was studied. The incidence of malreduction was also studied using the criterion of more than 2 mm separation or step. Results One hundred and six cases had intercalary fragment, accounting for 42.91% (106/247) of the posterior malleolus fracture, and 28.73% (106/369) of all ankle fractures. There were 81 cases with intercalary fragment larger than 2 mm, accounting for 32.79% (81/247) of the posterior malleolus fracture. There were 33 cases with intercalary fragment larger than 5 mm, accounting for 13.36% (33/247) of the posterior malleolus fracture. The incidence of intercalary fragment occurred in the posterolateral side was 64.15% (68/247). According to Bartonicek classification, the incidence of type I, II, III, and Ⅳ posterior ankle fracture was 8.91% (22/247), 49.39% (122/247), 21.86% (54/247), and 19.84% (49/247), respectively. The incidence of intercalary fragment was 4.54% (1/22) in type I posterior ankle fractures, 40.16% (49/122) in type II, 70.37% (38/54) in type III, and 36.73% (18/49) in type IV. The incidence in type III posterior malleolus fracture was significantly higher than that of other types of posterior malleolus fracture. CT scan after operation was conducted in 43 cases in which 19 cases had their intercalary fragment malreducted, accounting for 44.19%(19/43). Conclusion Intercalary fragment has high incidence in the posterior malleolus fracture, and the highest incidence occurs in Bartonicek III type posterior malleolus fracture. The study helps to further understanding and treatment of the posterior malleolus fracture. Key words: Adult; Ankle joint; Fractures, bone