膝关节盘状半月板的MRI诊断

目的　探讨膝关节盘状半月板的MRI表现以及MRI诊断盘状半月板的标准。材料与方法　对 2 6例经手术或关节镜证实的盘状半月板和 3 0例健康志愿者的膝关节进行MRI检查 ,对正常及盘状半月板的形态、大小及信号改变进行对照观察 ,包括半月板宽度和厚度的测量。结果　 2 6例盘状半月板中 ,2 5例为外侧盘状半月板 ,只有 1例为内侧盘状半月板 ,18例为厚板型 ,8例为楔型。冠状面上 ,盘状半月板体部平均宽度及厚度明显大于正常半月板 ,分别为 2 3 .4mm、11.5mm (P <0 .0 5 )和 3 .2mm、0mm(P <0 .0 1)。但盘状半月板边缘厚度与对侧半月板厚度差超过 2mm者只有 6例。矢状面上 ,连续 3层或 3层以上显示盘状半月板的前后角相连形成“领结”样改变 ,而正常半月板只有 2层有此表现。 2 6例盘状半月板中 ,2 4例并发半月板变性或撕裂。结论　盘状半月板多见于外侧半月板。盘状半月板特征性的MR表现是盘状半月板明显较正常半月板厚、大 ,MRI检查易于诊断。盘状半月板常并发半月板变性或撕裂。

MRI Diagnosis of Discoid Menisci of the Knee

Objective To investigate the MRI signs of discoid menisci and toestablish the criteria of MRI diagnosis of discoid menisci.Materials and Methods MRI of the knee was performed in 26 patients with proved discoid menisci and in 30 healthy volunteers. The shape, size and signal intensity of both the discoid menisci and normal menisci were evaluated, the width and thickness of the menisci were measured, and a comparison between discoid and normal menisci was made.Results Of 26 discoid menisci, 25 were in lateral and only one was in medial. Besides, 18 were classified as slab type and 8 wedge type. On coronal images, the average width and thickness at mid-body of the discoid menisci were significantly greater than those of normal menisci, which was 23.4mm vs 11.5mm (P＜0.05) and 3.2mm vs 0mm (P＜0.01), respectively. But a difference of over 2mm in the height at the periphery of the meniscus between discoid and opposite normal meniscus was noted in 6 patients. On sagittal images, “necktie” appearance, which was produced by the continuity of anterior and posterior horns, could be demonstrated on three or more contiguous 5mm sections in all discoid menisci, while on only two sections in normal menisci.Conclusion Discoid menisci are much more common seen in the lateral meniscus than in medial. The characteristic MR appearance of discoid meniscus is a meniscus which is significantly larger and thicker than a normal one, and which can be easily identified on MRI. Meniscal tears and degeneration are very common findings in discoid menisci.