Morphological Characteristics of the Posterior Malleolus Fragment According to the Ankle Fracture Patterns by Lauge-Hansen

Abstract

Category: Trauma Introduction/Purpose: The posterior malleolus fragment (PMF) of an ankle fracture occurs in various shapes with regard to injury mechanism. The purpose of this study was to evaluate the morphological characteristics of the posterior malleolus fragment according to the ankle fracture pattern by Lauge-Hansen classification using computer tomographic images. Methods: We retrospectively analyzed computer tomography data of 107 patients (107 ankles) who underwent surgery for tri- malleolus fracture from January 2012 to December 2014. A total of 76 ankles belong to Supination-Exorotation stage IV (SER group), 31 belong to Pronation- Exorotation stage IV (PER group). The type of PMF of two groups was respectively assessed by Haraguchi and Jan Bartonicek classification. The cross angle (α), fragment length ratio (FLR), fragment area ratio (FAR), sagittal angle and fragment height (FH) were measured as morphologic assessments. Results: The PMF type in SER group had mainly the posterolateral shape, while that in PER group had mainly the psotermedial two parts or large, posterolateral triangular shape (P= 0.02). The average cross angle (α) was no significant difference between two groups (SER group = 19.4°, PER group = 17.6°). The fragment length ratio and fragment height in PER group were significantly larger than that in SER group (P= 0.024, P=0.006). The fragment in PER group was significantly more vertical than that in SER group (P= 0.017). Conclusion: Morphological characteristics of the posterior malleolus fragment are different between SER group and PER group in trimalleolar ankle fracture. The SER type fractures are associated with smaller “rotational” fragment, while the PER type fractures are associated with larger “rotational and vertical” fragment with regard to the fragment volume and articular involvement.