Comparison of two plain radiographic and 3D-based measurement methods for posterior malleolar fragment size in trimalleol ankle fractures

Aim: The aim of this study is, to compare the posterior malleolar fragment (PMF) sizing between lateral ankle radiography measurement and computer assistted 3D modelling (CA3DM) methods Methods: Fifty-one patients between january 2015 and november 2018 with posterior malleolar fractured were included in this study. The rate of PMF to the articular surface at the distal end of the tibia was calculated by two different imaging methods by two surgeons. According to posterior fragment size, patients were separated into two groups. Group 1 was consisted of posterior fragment size smaller than 15% and group 2 was bigger than 15% due to CA3DM. Results: The interobserver correlation (IOC) between two observers and CA3DM was 44.3%. Also the IOC between first observer and CA3DM was 35.7% (p 0.05), second observer and CA3DM was 51.6% (p 0.05), first and CA3DM was 18.6% (p>0.05), second observer and CA3DM was 7.1% (p>0.05) and two observers was 49% (p<0.05). Conclusion: Our study shows that posterior malleolar fragment size measuring on plain radiography is not a safe method for bigger fragments and CA3DM method may be a more reliable to assess correct fragment size and also to analyze fracture morphology. But for fragments ≤15% CA3DM and plain radiographic measures are not statistically different.