The Classification, Pathoanatomy and Radiological Outcomes of Medial Wall Blowout Fractures of the Ankle
J Aamir, RM Kumar, M Ali, BS Abdullah, J McEvoy, C Wyatt, A Pillai, L Mason
Background: Medial wall blowout (MWB) ankle fractures have not previously been described in the literature. Our aim in this study was to analyse the morphology of medial wall blowout fractures and their radiological outcomes.
Methods: The MWB fracture fragments were characterised into four groups. A type 1A fracture was described as an anteromedial column fragmentation. Type 1B fractures consisted of posteromedial column fragmentation. Type 2 fracture consisted of both column wall fragmentation and type 3, any medial wall fragmentation with medial joint impaction.
Results: Over 2000 patients were identified across ten years with medial malleolar fractures across two centres; of these, 196 had MWB fractures with CT imaging. There were 95 1A fractures (48.5%), 31 1B fractures (15.8%), 40 Type 2 fractures (20.4%) and 30 type 3 fractures (15.3%). Type 1B fractures were significantly more likely to undergo plate fixation than other types (p = .001). MWB fractures occurred most in PER fracture types (50.8%). Type 2 fractures were different because they occurred more with SER-type mechanisms. PM fractures were a common association (82.4%), most commonly M+M type 1. MWB type 1B occurred more with M+M 2B fractures. The overall malreduction rate was 11.8%, although 1B fracture types had significantly higher malreductions (22.6%, p=.041). The overall nonunion rate was 20.6%, the highest nonunion reported in the type 2 fractures (33.3%), although not significant. Tibialis posterior tendon entrapment was common (47.3%), although it was significantly more likely in type 2 fractures (74.4%, p = 0.001).
Conclusion: The MWB fractures are an uninvestigated subtype of ankle fractures. The 1B type has a higher rate of malreduction, which could be due to its higher association with PM fractures. Tib post needs specific attention with these fracture types, especially Type 2 fractures.
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