Formation of ring-shaped lateral meniscus following anterior cruciate ligament reconstruction: A case report

A Ring-Shaped Lateral Meniscus in an Anterior Cruciate Ligament Reconstruction Surgery

The ring-shaped meniscus is a rare variant of meniscus anomalies. We report a case of a young man who experienced right knee instability following a sports-related injury. Clinical examination suggested an anterior cruciate ligament (ACL) tear, which was confirmed through imaging studies. Intra-operatively, an incidental finding revealed the presence of a ring-shaped lateral meniscus. We discuss the diagnostic features of this uncommon abnormality.

"Ring-shaped" meniscus and accompanying intermeniscal bridge meniscus: a rare combined variant resembling a bucket-handle tear

Many anatomical variations have been described in the menisci, especially in the lateral meniscus. Among these, discoid meniscus is the most common variation. Others are described in the literature as double-layered meniscus, accessory meniscus, ring-shaped meniscus, and hypoplastic meniscus. Also, combined variations associated with ring-shaped meniscus have been described, and they can be confused with fragmented complex tears and cause unnecessary surgery. Increasing awareness of the imaging features of these accompanying combined variations may aid in the recognition and differentiation of this entity from meniscus tears. We report the case of a ring-shaped meniscus and accompanying intermeniscal bridge meniscus, which has not been described before in the literature, highlighting the MRI and arthroscopic imaging findings of it.

Ring-Shaped Meniscus, MRI Features, and Diagnosis: A Report of 2 Cases

CASE

A ring-shaped meniscus (RSM) is a rare malformation of debatable origin usually occurring on the lateral meniscus. Here, we present 2 cases of RSM with differing etiologies and discuss the current literature on the topic. These reports may help with the identification of RSMs in the future and assist in understanding the true etiopathogenesis of individual cases.

CONCLUSION

These 2 cases exemplify the variation in presentations of ring-shaped menisci and their radiological features on both x-ray and magnetic resonance imaging. This reinforces the idea that there may be both a congenital and an iatrogenic etiology to this rare condition.

The ring-shaped meniscus: a case series demonstrating the variation of imaging appearances on MRI

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.

Ring-shaped meniscus formation may arise from the regenerative response to meniscectomy during growth spurts: A case report

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We presented a case of newly formed ring-shaped meniscus-like tissue after partial resection of discoid lateral meniscus.

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The newly formed interhorn bridge could have represented a meniscus-like tissue that appeared secondary to tissue repair.

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Intra-patient findings indicate that growth spurts may promote the tissue repair.

Introduction

Ring-shaped meniscus is very rare and generally considered to be a congenital malformation. Here, we report a case of newly formed ring-shaped meniscus-like tissue following arthroscopic partial meniscectomy for a complete discoid lateral meniscus.

Presentation of case

A 14-year-old boy underwent arthroscopic partial meniscectomy for complete discoid lateral meniscus of the left knee. The growth plates were present at the surgery. Although pain improved immediately after surgery, he reported left knee pain at the 7-month follow-up. Magnetic resonance imaging revealed a bucket-handle tear of the lateral meniscus and a second arthroscopic surgery was performed. During arthroscopy, we found that the anterior and posterior horns of the lateral meniscus were connected by meniscus-like tissue forming a ring-shaped meniscus and the newly formed interhorn meniscal bridge was resected. Histological evaluation indicated that the newly formed tissue was meniscus-like tissue that had appeared secondary to tissue repair. He visited our hospital at 16 years old, after the growth plates had closed, complaining of right knee pain. Arthroscopic partial meniscectomy was performed for complete discoid lateral meniscus of the right knee. As of two years after this surgery, no morphological changes have been observed.

Discussion

Although the exact mechanisms of meniscus-like tissue formation remain unclear, the growth spurt may promote the mechanisms of tissue repair, forming ring-shaped meniscus-like tissue.

Conclusion

This is the first case of ring-shaped meniscus-like tissue forming after partial resection of a complete discoid lateral meniscus. Ring-shaped meniscus-like tissue can develop in growing patients.