Department of Musculoskeletal Radiology, Royal Orthopaedic Hospital NHS Foundation Trust, Bristol Road South, Northfield, Birmingham, UK.
Skeletal Radiol. 2020 Feb;49(2):281-289. doi: 10.1007/s00256-019-03277-y. Epub 2019 Jul 30.
The ring-shaped meniscus (RSM) is a rare meniscal variant in which there is an intermeniscal bridge between the anterior and posterior horns of the meniscus, thus forming a complete ring. The lateral meniscus is more commonly involved than the medial meniscus. Distinguishing an RSM from a bucket handle tear (BHT) with a displaced fragment in the intercondylar notch is challenging and there are reports of negative arthroscopies for suspected BHTs. There are many reports of symptomatic and asymptomatic lateral RSMs diagnosed on MRI in the literature. We report a series of RSMs in six patients, which includes MRI descriptions of two cases of medial RSM and a case of bilateral lateral RSM, which were diagnosed on MRI and have never previously been reported. This study will also describe the various imaging features of a RSM that distinguish it from a displaced BHT. We will also discuss associated rare malformations encountered in our study, such as hypoplastic anterior cruciate ligament and the anomalous insertion of the popliteus tendon onto the posterior horn of a lateral RSM.
环形半月板（RSM）是一种罕见的半月板变体，在前、后半月板角之间存在半月板间桥，从而形成完整的环。外侧半月板比内侧半月板更常受累。区分 RSM 与有移位碎片的桶柄撕裂（BHT）在髁间切迹中具有挑战性，并且有报道称对疑似 BHT 的关节镜检查为阴性。文献中有许多关于 MRI 诊断的有症状和无症状外侧 RSM 的报道。我们报告了 6 例 RSM 患者，其中包括 2 例内侧 RSM 和 1 例双侧外侧 RSM 的 MRI 描述，这些 RSM 是通过 MRI 诊断的，以前从未报道过。本研究还将描述 RSM 的各种影像学特征，以将其与移位的 BHT 区分开来。我们还将讨论在我们的研究中遇到的一些罕见的畸形，如前交叉韧带发育不良和腘肌腱异常插入外侧 RSM 的后角。
