A new, MRI-based classification system for tibial spine fractures changes clinical treatment recommendations when compared to Myers and Mckeever

Purpose Tibial spine fractures (TSFs) are graded according to the Meyers and McKever (MM) classification system, which is based on a qualitative evaluation of plain radiographs. However, although MRI images can provide important information about these fractures, there is no MRI-based classification system. This study aims to (1) establish the intra- and inter-rater reliability of the MM system for use with radiographs, (2) propose a quantitative, MRI-based system and compare its reliability to the MM system, and (3) assess how often using the MRI-based system changes the classification and potential treatment plan as previously determined using MM. Methods The MRI-based system was designed with three grades based on quantitative displacement patterns of the fractured fragment and tissue entrapment. Four raters from a tertiary care center evaluated 20 fractures according to the MM and MRI-based systems. Observers graded images at two time points at least 2 weeks apart, after which we compared the intra- and inter-rater reliability of each system (using Fleiss’ kappa and weighted kappa, respectively) and assessed how often using the MRI-based system changed the fracture grade. Results Both the MM and MRI-based systems exhibit fair to moderate intra- and inter-rater reliability (average kappa values ranged from 0.38 to 0.66). Use of the MRI-based system changed the fracture grade and as a result modified the treatment recommendations in 32.5% of cases: 6.9% were previously unnoticed fractures, 13.1% underwent a raise in grade, and 12.5% were graded as lower than before. Conclusion The MRI-based system is as reliable as the MM system and provides specific, quantitative criteria for classifying fractures according to fragment displacement and tissue entrapment. The new MRI-based system potentially clarifies treatment indications for TSFs. Level of evidence Diagnostic Study, Level II.