title: Influence of the Medial Knee Structures on Valgus and Rotatory Stability in Total Knee Arthroplasty.
abstract: BACKGROUND
  Precise biomechanical knowledge of individual components of the MCL is critical for proper MCL release during TKA. This study was to define the influences of the deep MCL and the POL on valgus and rotatory stability in TKA using cadaveric knees.
  
  
  METHODS
  This study used six fresh-frozen cadaveric knees. All TKA procedures were performed using a cruciate-retaining TKA with a CT-free navigation system. We did a sequential sectioning on each knee, S1; femoral arthroplasty only, S2; medial half tibial resection with spacer, S3; anterior cruciate ligament cut, S4; tibial arthroplasty, S5; release of the dMCL, S6; release of the POL. The navigation system monitored motion after application of 10 N-m valgus loads and 5 N-m internal and external rotation torques to the tibia at 0°, 20°, 30°, 60°, and 90° of knee flexion for each sequence.
  
  
  RESULTS
  There were no significant differences in medial gaps. Internal rotation angles significantly increased after S2 at 0°, 20°, and 30°, and after S6 at 90° compared with those after S1. External rotation angles significantly increased after S3 at 0°, S4 at 60°, S5 at 0°, 30° and 90°, and after S6 at 30°, 60° compared with those after S1.
  
  
  CONCLUSIONS
  Significant increases of rotatory instability were seen on release of the dMCL, and then further increased after release of the POL. Surgical approach of retaining the dMCL and POL has a possibility to improve the outcome after primary TKA.
authors.affiliation: Department of Orthopaedic Surgery, Nippon Medical School, Tokyo, Japan.
authors.forename: Norishige
authors.initials: N
authors.lastname: Iizawa
authors.affiliation: Department of Orthopaedic Surgery, Nippon Medical School, Tokyo, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Mori
authors.affiliation: Department of Orthopaedic Surgery, International University of Health Welfare Hospital, Tochigi, Japan.
authors.forename: Tokifumi
authors.initials: T
authors.lastname: Majima
authors.affiliation: Department of Orthopaedic Surgery, Nippon Medical School, Tokyo, Japan.
authors.forename: Hidemi
authors.initials: H
authors.lastname: Kawaji
authors.affiliation: Department of Orthopaedic Surgery, Nippon Medical School, Tokyo, Japan.
authors.forename: Shuhei
authors.initials: S
authors.lastname: Matsui
authors.affiliation: Department of Orthopaedic Surgery, Nippon Medical School, Tokyo, Japan.
authors.forename: Shinro
authors.initials: S
authors.lastname: Takai
mesh_terms: D000368:Aged; D016118:Anterior Cruciate Ligament; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D001696:Biomechanical Phenomena; D006801:Humans; D007593:Joint Instability / Q000209:etiology* / Q000503:physiopathology; D007719:Knee Joint / Q000502:physiology* / Q000601:surgery; D017888:Medial Collateral Ligament, Knee / Q000502:physiology* / Q000601:surgery; D008875:Middle Aged; D016059:Range of Motion, Articular; D012399:Rotation; D019415:Torque
keywords: biomechanics; deep medial collateral ligament; instability; navigation; posterior oblique ligament; soft tissue release