The MRI findings of meniscal root tear of the medial meniscus: emphasis on coronal, sagittal and axial images

The purpose of this study was to evaluate the accuracy of the characteristic magnetic resonance imaging (MRI) findings of medial meniscal root tear in the coronal, sagittal and axial planes. Thirty arthroscopically diagnosed patients who had undergone preoperative knee MRI were included in this study. They were compared to 30 age-matched patients with medial meniscus tears without root tears. The findings used for imaging analysis were as follows: the radial tear on the meniscal root of the medial meniscus in the axial plane, the presence of the truncation sign in the coronal plane and the ghost meniscus sign in the sagittal plane. Meniscal extrusion in the coronal plane was also evaluated. All the MRI findings of both groups were statistically analyzed. All the findings were more frequently found in the root tear group than those in the control group (P < 0.05). The sensitivity, specificity, positive predictive value and negative predictive value of finding a radial tear in the axial plane were 93.3, 100, 100 and 93.8%, respectively. In the coronal plane, rates for the presence of the truncation sign were 90, 100, 100 and 90.9%, respectively. In the sagittal plane, rates for the presence of the ghost meniscus sign were 96.7, 96.7, 96.7 and 96.7%, respectively. The rates for the meniscus extrusion in the coronal plane were 63.3, 90, 86.4 and 71.1%, respectively. The findings of medial meniscal root tear were characteristic as compared with the control group. Radial tear in the axial plane also showed similar diagnostic accuracy as that seen in the other planes. The characteristic findings provide high diagnostic accuracy, and axial plane is helpful to detect medial meniscal root tear. Diagnostic study, Level III.