The Classification, Pathoanatomy and Radiological Outcomes of Medial Wall Blowout Fractures of the Ankle

Research Type: Level 3 - Retrospective cohort study, Case-control study, Meta-analysis of Level 3 studies Introduction/Purpose: Medial wall blowout (MWB) fractures of the ankle 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: This was a multicentre historic cohort study. 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: A total of 2,304 patients were screened, with 196 meeting inclusion criteria. There were 95 type 1A (48.5%), 31 type 1B (15.8%), 40 type 2 (20.4%), and 30 type 3 fractures (15.3%). MWB fractures were most associated with pronation external rotation (PER) mechanisms, except type 2, which occurred more with supination external rotation (SER). Posterior malleolar fractures (PMF) were present in 82.4% of MWB cases. Tibialis posterior tendon entrapment was seen in 47.34% of cases, most commonly in type 2 fractures. The overall malreduction rate was 11.8%, highest in type 1B fractures (22.6%, p=.041). On multivariable analysis, only tibialis posterior tendon entrapment remained significantly associated with malreduction (p=.015, OR 5.91). Conclusion: The MWB fractures are an under investigated subtype of ankle fractures. Classifying the fractures by morphology has shown specific associations, with an increase in rate of malunion in type 1B fractures. The tibialis posterior tendon needs specific attention with these fracture types, especially the type 2 fractures, as there is a statistical increase in malunion