title: Effect of radial meniscal tear on in situ forces of meniscus and tibiofemoral relationship.
abstract: OBJECTIVE
  To clarify the effect of the radial tear of the lateral meniscus on the in situ meniscus force and the tibiofemoral relationship under axial loads and valgus torques.
  
  
  METHODS
  Ten intact porcine knees were settled to a 6-degree of freedom robotic system, while the force and 3-dimensional path of the knees were recorded via Universal Force Sensor (UFS) during 3 cycles of 250-N axial load and 5-Nm valgus torque at 15°, 30°, 45°, and 60° of knee flexion. The same examination was performed on the following 3 meniscal states sequentially; 33, 66, and 100% width of radial tears at the middle segment of the lateral meniscus, while recording the force and path of the knees via UFS. Finally, all paths were reproduced after total lateral meniscectomy and the in situ force of the lateral meniscus were calculated with the principle of superposition.
  
  
  RESULTS
  The radial tear of 100% width significantly decreased the in situ force of the lateral meniscus and caused tibial medial shift and valgus rotation at 30°-60° of knee flexion in both testing protocols. Under a 250-N axial load at 60° of knee flexion, the in situ force decreased to 36 ± 29 N with 100% width of radial tear, which was 122 ± 38 N in the intact state. Additionally, the tibia shifted medially by 2.1 ± 0.9 mm and valgusrotated by 2.5 ± 1.9° with the complete radial tear. However, the radial tear of 33 or 66% width had little effect on either the in situ force or the tibial position.
  
  
  CONCLUSIONS
  A radial tear of 100% width involving the rim significantly decreased the in situ force of the lateral meniscus and caused medial shift and valgus rotation of the tibia, whereas a radial tear of up to 66% width produced only little change. The clinical relevance is that loss of meniscal functions due to complete radial tear can lead to abnormal stress concentration in a focal area of cartilage and can increase the risk of osteoarthritis in the future.
authors.affiliation: Department of Orthopaedic Surgery, Osaka University Graduate School of Medicine, 2-2, Yamada-oka, Suita-city, Osaka, 565-0871, Japan. tachibanayuta@gmail.com.
authors.forename: Yuta
authors.initials: Y
authors.lastname: Tachibana
authors.affiliation: Department of Orthopaedic Surgery, Osaka University Graduate School of Medicine, 2-2, Yamada-oka, Suita-city, Osaka, 565-0871, Japan.
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Mae
authors.affiliation: Biomechanics Laboratory, Faculty of System Design, Tokyo Metropolitan University, 1-1, Minami-Osawa, Hachioji-city, Tokyo, 192-0397, Japan.
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Fujie
authors.affiliation: Sports Orthopaedic Surgery Center, Osaka Yukioka Hospital, 2-2-3, Ukita, Kita-ku, Osaka, 530-0021, Japan.
authors.forename: Konsei
authors.initials: K
authors.lastname: Shino
authors.affiliation: Department of Orthopaedic Surgery, Osaka University Graduate School of Medicine, 2-2, Yamada-oka, Suita-city, Osaka, 565-0871, Japan.
authors.forename: Tomoki
authors.initials: T
authors.lastname: Ohori
authors.affiliation: Department of Orthopaedic Surgery, Osaka University Graduate School of Medicine, 2-2, Yamada-oka, Suita-city, Osaka, 565-0871, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Yoshikawa
authors.affiliation: Department of Orthopaedic Surgery, Osaka University Graduate School of Medicine, 2-2, Yamada-oka, Suita-city, Osaka, 565-0871, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Nakata
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D005269:Femur; D007719:Knee Joint / Q000503:physiopathology*; D008592:Menisci, Tibial / Q000503:physiopathology*; D012399:Rotation; D013552:Swine; D013977:Tibia; D000070600:Tibial Meniscus Injuries / Q000503:physiopathology*; D019415:Torque
keywords: 6-degree of freedom robotic system; In situ force; Lateral meniscus; Porcine knee; Radial tear; Tibiofemoral relationship