Repeat tear of postoperative meniscus: Potential MR imaging signs

PURPOSE: To determine the usefulness of five magnetic resonance (MR) signs of repeat tears of the postoperative meniscus. MATERIALS AND METHODS: Fat-saturated proton-density-weighted and T2-weighte d MR images in 20 patients who had undergone at least two knee surgeries we re reviewed. Second-look arthroscopic confirmation of meniscal status was a vailable in all patients. MR images of 39 menisci (10 repeat fears, 11 post operative menisci without repeat tears, three tears in previously normal me nisci, and 15 normal menisci) were evaluated for (a) a linear area of abnor mal signal intensity extending to an articular surface on intermediate-weig hted images, (b) abnormal meniscal morphology, (c) likelihood of a typical postoperative appearance, (d) fluid extending into the linear area on T2-we ighted images, and (e) cartilage defects. Two radiologists rated their conf idence on a five-point scale for the presence of these signs and were compa red for revel of agreement. RESULTS: The intraclass correlation coefficient (range, 0.75-0.91) indicate d a high level of agreement. Areas under the receiver operating characteris tic curves were large (range, 0.80-0.87) for all five signs, with a line (g rade 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 13.10; P < .002; odds ratio, 1.588 and 1.599 for the line and the fluid wi thin the line, respectively). CONCLUSIONS: The two best MR signs of repeat tear of the postoperative meni scus were the presence of a line and fluid within the line extending to an articular surface.