This is a rare case of a patient with a double-layered lateral meniscus, undergoing surgical treatment. A 17-year-old woman who was a member of a volleyball club had a two-year history of right knee pain with episodes of locking, although she had no history of trauma. She was referred to our hospital because her condition did not improve after conservative treatment. On presentation to the hospital, she had full range of motion in the right knee. McMurray’s test revealed no clicks; however, it produced pain in the lateral part. Plain radiography revealed no abnormal findings, whereas magnetic resonance imaging showed high signal in the posterior segment of the lateral meniscus and an increase in its volume. Arthroscopic findings showed an accessory meniscus with a flat surface overlying a normal-sized lateral meniscus. It was firmly connected to the posterior root and middle segment of the lower normal meniscus. The accessory meniscus was markedly mobile as revealed by probing. The patient was diagnosed with double-layered lateral meniscus and underwent resection of the accessory meniscus. Postoperatively, she initiated strengthening of muscles and range of motion training without weight-bearing restrictions. Two months postoperatively, she had completely recovered and participated in volleyball practices. In the last follow-up at 18 months, she had no restrictions in daily or sports activities.
Background: Lateral discoid meniscus (LDM) should be treated and preserved with saucerization and/or suture repair. However, repair of the meniscal hoop structure is sometimes difficult due to displacement or large defects. In this study, we aimed to examine tear patterns based on the Ahn classification in those requiring meniscal repair and those undergoing subtotal meniscectomy. Methods: Twenty-three patients were evaluated (mean age, 27.4 years; mean follow-up period, 2.5 years). The following were evaluated: displacement morphology based on the Ahn classification, site of tear under arthroscopy, morphology, surgical procedure, Lysholm score at final postoperative follow-up, and clinical outcome of meniscus using Barrett’s criteria. Result: There were 16 knees without displacement (saucerization with suture repair, 13 knees; subtotal meniscectomy, 3 knees) and 10 knees with displacement (reduction with suture repair, 3 knees; subtotal meniscectomy, 7 knees). Subtotal meniscectomy was performed more often in cases with dislocation, especially in the central shift type as defined by the Ahn classification. The mean Lysholm score was 65.0 points preoperatively and 95.3 points postoperatively. Twenty-three knees (88%) were postoperatively categorized under the Barrett’s criteria as healing and 3 knees (12%) were categorized as non-healing. The number of non-healing cases that underwent subtotal meniscectomy was relatively small (1 of 10 knees), and the short-term results were not poor. Conclusion: Localized peripheral longitudinal tears tended to be repairable even with displacement, while peripheral tears covering the entire meniscus or with severe defects/tears in the body of the meniscus tended to be difficult to repair, leading to subtotal meniscectomy.
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