Repeat Tear of Postoperative Meniscus: Potential MR Imaging Signs

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Abstract
To determine the usefulness of five magnetic resonance (MR) signs of repeat tears of the postoperative meniscus. Fat-saturated proton-density-weighted and T2-weighted MR images in 20 patients who had undergone at least two knee surgeries were reviewed. Second-look arthroscopic confirmation of meniscal status was available in all patients. MR images of 39 menisci (10 repeat tears, 11 postoperative menisci without repeat tears, three tears in previously normal menisci, and 15 normal menisci) were evaluated for (a) a linear area of abnormal signal intensity extending to an articular surface on intermediate-weighted images, (b) abnormal meniscal morphology, (c) likelihood of a typical postoperative appearance, (d) fluid extending into the linear area on T2-weighted images, and (e) cartilage defects. Two radiologists rated their confidence on a five-point scale for the presence of these signs and were compared for level of agreement. The intraclass correlation coefficient (range, 0.75-0.91) indicated a high level of agreement. Areas under the receiver operating characteristic curves were large (range, 0.70-0.87) for all five signs, with a line (grade 3 signal intensity) and fluid within a line having the highest areas. These two signs also had the highest statistical scores (chi 2 = 14.12 and 13.30; P < .002; odds ratio, 1.588 and 1.599 for the line and the fluid within the line, respectively). The two best MR signs of repeat tear of the postoperative meniscus were the presence of a line and fluid within the line extending to an articular surface.