MJ Tuca, E Luderowski, E B. Gausden, C Goodbody, G Konin, D W. Green (Santiago, Chili)
Purpose We aim to (1) validate the Meyers and McKeever system (M&M) for use with x-rays, (2) propose a new MRI-based system for classifying tibial spine avulsion fractures (TSAFs) (3) assess how often using the MRI-based system changes the classification and potential treatment plan.
Methods We designed an MRI-based system for classifying TSAFs. Grade I: non- or minimally-displaced fractures (< 2 mm displacement). Grade II: posterior-hinged fractures with >2mm displacement of the anterior aspect of the fracture and <2mm displacement of the posterior aspect. Grade III: displaced fractures (>2mm of displacement of the posterior aspect), and any TSAF that results in meniscal or intermeniscal ligament entrapment, or fracture extension towards the weight-bearing surface of the tibial plateaus.
Four independent observers were asked to evaluate and classify the images of 20 patients. First, according to the M&M using plain X-Rays, and then on MRIs using our MRI-based system. Each observer graded images at two time points at least two weeks apart.
Results Both the M&M and the MRI-based system exhibited a fair inter-rater reliability (k=0.39 and k=0.38). Inter-rater reliability exhibited a substantial agreement for both systems (k=0.66). The intra-rater agreement of the MRI-based system tended to increase with years of rater experience. The use of an MRI-based system changed the fracture grade in 33% of cases.
Conclusion M&M classification and the new MRI-based system exhibited comparable fair to moderate intra- and inter-rater reliabilities. In 1/3 of the cases, assessment using MRI substantially modified grading.