The study was to propose a classification system of posterior malleolar fractures by fracture lines with the use of CT scans, including 3D CT reconstruction, which can better understand morphological characteristics, analyze the mechanism and guide the surgeon to choose optimal approach and fixation.

The investigators retrospectively analyzed consecutive patients with ankle fractures from January 2013 and December 2019 . Participants were included with OTA/AO type 44 fractures involving posterior malleolus and CT scans. The exclusion criteria were: (1) previous ankle surgery; (2) pathological fractures; (3) previous deformity in ankle joint; (4) age ≤16 years old. Finally, A total of 128 patients were included in this study. 128 consecutive participants with posterior malleolar fractures from January 2013 and December 2019. CT data were loaded into Mimics software (V20.0, Materialize), in which 3D CT reconstruction, morphological analysis and data measurements were made. Statistical analysis was performed using the Statistical Packages for Social Sciences V23.0 (SPSS, Chicago, IL, USA). Mann-Whitney U test were used. P value of < 0.05 was considered statistically significant.

Inclusion Criteria:

• OTA/AO type 44 fractures involving posterior malleolus and CT scans

Exclusion Criteria:

• Previous ankle surgery
• Pathological fractures
• Previous deformity in ankle joint
• Age ≤16 years old

OTA/AO type 44 fractures involving posterior malleolus

The results of the study are publicly available.