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

Abstract

Highlights We presented a case of newly formed ring-shaped meniscus-like tissue after partial resection of discoid lateral meniscus. The newly formed interhorn bridge could have represented a meniscus-like tissue that appeared secondary to tissue repair. Intra-patient findings indicate that growth spurts may promote the tissue repair.

Chinese Experts Consensus and Practice Guideline on Discoid Lateral Meniscus

“…45 Monllau et al 46 believed that the ring-shaped meniscus could be considered the fourth type of DLM, and forming modified Watanabe classification system (Figure 2). In terms of such variants of the lateral meniscus as Wrisberg meniscus, ringshaped meniscus, etc., they are similar to NLM but different from DLM in histology, 11,13,14,38,51 and they are not broad in morphology. Therefore, they should not be classified as subtypes of DLM but as other variations of the meniscus.…”

“…There are many kinds of congenital variations for the lateral meniscus, including DLM, Wrisberg meniscus, ring‐shaped meniscus, layered meniscus, meniscus defects, meniscus separation, etc., among which the most common type is DLM, and the other variants are rare 7,38–41 . Morphologically, DLM is broader, the coverage area of the lateral tibial plateau is more than 70%, and the incidence of peripheral rim instability is higher (38%–88%) 1,3,9,42–44 .…”

“…There are many kinds of congenital variations for the lateral meniscus, including DLM, Wrisberg meniscus, ringshaped meniscus, layered meniscus, meniscus defects, meniscus separation, etc., among which the most common type is DLM, and the other variants are rare. 7,[38][39][40][41] Morphologically, DLM is broader, the coverage area of the lateral tibial plateau is more than 70%, and the incidence of peripheral rim instability is higher (38%-88%). 1,3,9,[42][43][44] Histologically, the circular collagen fiber of DLM is sparse and disordered in arrangement, and the proportion and distribution of cells differ from NLM 3,[10][11][12][13][14][15][16] (Grade E).…”

“…41 The ring-shaped lateral meniscus is hollow, without meniscus tissue in the central region, the incidence of which is 0.3-2.4%. 49,50 Given the morphology of these variants is not only significantly different from DLM, but the histopathological features, clinical features, diagnosis, and treatment of those also vary from DLM, 11,13,14,38,51 Wrisberg meniscus and ring-shaped meniscus should not be considered as subtypes of the DLM but as independent variants of the lateral meniscus 52 (Grade C).…”

Ring-Shaped Meniscus, MRI Features, and Diagnosis

“…It had previously been theorized that RSMs are a consequence of central perforation in a discoid meniscus through degenerative and/or traumatic mechanisms 17 . Recent publications have also documented the formation of an intrameniscal bridge as a potential regenerative response to surgical intervention, particularly after ACL reconstruction 6 and/or meniscectomies [20][21][22] . In these cases, Fujii et al 6 and Soejima et al 21 postulate that the interhorn structure may develop from the accumulation of mesenchymal stem cells and growth factors from bone tunneling leading to excessive scar formation, or as a result of ACL remnant metaplasia.…”