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Comparison of radiographs and CT features between posterior pilon fracture and posterior malleolus fracture: a retrospective cohort study.

OBJECTIVES
This study explored the morphological differences between posterior Pilon fracture and posterior malleolus fracture from radiographs and computed tomography (CT) to provide detail for diagnosis and treatment of them.


METHODS
Radiographs and CT imaging data of 174 patients with distal posterior tibial fractures who were treated from January 2013 to January 2019 were retrospectively analyzed. Based on the operation and imaging examination, the fractures were classified into posterior Pilon fractures and posterior malleolus fractures. Radiographic parameters including the width, height, depth, α angle, β angle, γ angle, fragment area ratio 1 (FAR1), δ angle and fragment area ratio 2 (FAR2) of ankle mortise were measured.


RESULTS
There were 96 posterior Pilon fractures (type I: 30, type II: 22 and type III: 44) and 78 posterior malleolus fractures (type I: 40 and type II: 38). The ankle depth, α angle, γ angle, FAR1 and FAR2 of posterior Pilon fractures were larger than these of posterior malleolus fractures (p < 0.05). In addition, FAR1 and FAR2 of type II and type III posterior Pilon fractures were significantly larger than these of type I (p < 0.05). FAR1 and FAR2 of type I posterior malleolus fractures were significantly smaller than these of type II (p < 0.05).


CONCLUSIONS
Radiographs combined with CT analysis is an effective method to accurately distinguish morphological features between posterior Pilon fracture and posterior malleolus fracture.


ADVANCES IN KNOWLEDGE
Radiographs combined with CT distinguished the fracture of posterior malleolus and posterior Pilon rapidly and accurately, instead of operation.