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 ankleradiography measurement and computer assistted 3D modelling (CA3DM) methodsMethods: Fifty-one patients between january 2015 and november 2018 with posterior malleolar fractured wereincluded in this study. The rate of PMF to the articular surface at the distal end of the tibia was calculated by twodifferent imaging methods by two surgeons. According to posterior fragment size, patients were separated intotwo groups. Group 1 was consisted of posterior fragment size smaller than 15% and group 2 was bigger than15% due to CA3DM.Results: The interobserver correlation (IOC) between two observers and CA3DM was 44.3%. Also the IOCbetween first observer and CA3DM was 35.7% (p<0.05), second observer and CA3DM were 46.6% (p<0.01)and observers was 51.6% (p<0.01). For group 1, IOC between two observers and CA3DM was 41.2% (p<0.05),first observer and CA3DM was 30.6% (p>0.05), second observer and CA3DM was 51.6% (p<0.05) and twoobservers were 45.8% (p<0.05). For group 2, IOC between two observers and CA3DM was 27.9% (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 was49% (p<0.05).Conclusion: Our study shows that posterior malleolar fragment size measuring on plain radiography is not a safemethod for bigger fragments and CA3DM method may be a more reliable to assess correct fragment size andalso to analyze fracture morphology. But for fragments ≤15% CA3DM and plain radiographic measures are notstatistically different.