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

INTRODUCTION: We presented the first case in the literature of inter-horn bridge formation involved in ring-shaped lateral meniscus after anterior cruciate ligament (ACL) reconstruction. PRESENTATION OF CASE: A 22-year-old man underwent anatomic double-bundle ACL reconstruction using semitendinosus tendon autograft. At the surgery, the lateral meniscus showed a normal appearance without meniscal tears and had no instability. There were no meniscal anomalies such as discoid meniscus and ring-shaped meniscus. Magnetic resonance image examination was performed before second-look arthroscopy at 1 year postoperatively. A coronal plane showed a small triangular fragment located at the medial border of the lateral tibial plateau. An axial plane demonstrated a ring-shaped lateral meniscus. On second-look arthroscopy, there was a meniscus-like tissue formation that connected the anterior horn to the posterior horn of the lateral meniscus at the lateral intercondylar tubercle. DISCUSSION: Ring-shaped meniscus is an extremely rare malformation of the meniscus. Our hypothesis was that drilling debris and remaining remnant of ACL might induce a scar tissue formation. CONCLUSION: This is the first case in the literature of inter-horn bridge formation involved in ring-shaped lateral meniscus following ACL reconstruction.