title: Formation of ring-shaped lateral meniscus following anterior cruciate ligament reconstruction: A case report.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
  
  
  CONCLUSIONS
  This is the first case in the literature of inter-horn bridge formation involved in ring-shaped lateral meniscus following ACL reconstruction.
authors.affiliation: Department of Orthopaedic Surgery, Okayama University, Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan.
authors.forename: Masataka
authors.initials: M
authors.lastname: Fujii
authors.affiliation: Department of Orthopaedic Surgery, Okayama University, Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan. Electronic address: matino@md.okayama-u.ac.jp.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Furumatsu
authors.affiliation: Department of Orthopaedic Surgery, Okayama University, Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Miyazawa
authors.affiliation: Department of Orthopaedic Surgery, Sumitomo Besshi Hospital, Japan.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Tanaka
authors.affiliation: Department of Orthopaedic Surgery, Okayama University, Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan.
authors.forename: Hiroto
authors.initials: H
authors.lastname: Inoue
authors.affiliation: Department of Orthopaedic Surgery, Okayama University, Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan.
authors.forename: Yuya
authors.initials: Y
authors.lastname: Kodama
authors.affiliation: Department of Orthopaedic Surgery, Okayama University, Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan.
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Ozaki
keywords: Anterior cruciate ligament reconstruction; Knee; Meniscus; Ring-shaped lateral meniscus; Second-look arthroscopy