title: In vivo femoro-tibial kinematic analysis of a tri-condylar total knee prosthesis.
abstract: BACKGROUND
  An alternative tri-condylar implant has been designed to incorporate necessary posterior stability without a post, but has not been evaluated. The purpose of the current study was to determine the in vivo three dimensional femoro-tibial kinematics of a tri-condylar implant during a weight bearing deep knee bend activity.
  
  
  METHODS
  Fluoroscopy based in vivo femoro-tibial kinematics of the tri-condylar implant was assessed for 66 knees during a deep knee bend activity, using a three dimensional to two dimensional model fitting approach.
  
  
  RESULTS
  Average range of motion was 125.5° (standard deviation (SD)=20.5°) in sagittal plane, and 42 knees (63.6%) experienced at least 120° of weight-bearing knee flexion. The average amount of posterior femoral movement (PFM) was 8.7mm (SD=4.3mm) for the medial condyle and 11.2mm (SD=5.4mm) for the lateral condyle. PFM of the medial condyle was significantly smaller than that of the lateral condyle. The average amount of femoro-tibial axial rotation was 5.7° (SD=6.4°), and 56 knees (84.8%) experienced a normal axial rotation pattern. Condylar lift-off, mostly occurring in deep flexion range, was experienced in 16 knees (24.2%).
  
  
  CONCLUSIONS
  Knees in the current study did achieve high weight-bearing flexion, more normal-like greater posterior femoral movement of lateral condyle than the medial condyle and a normal axial rotation pattern, albeit, less in magnitude than the normal knee.
authors.affiliation: Center for Musculoskeletal Research, University of Tennessee, Knoxville, TN, USA; Department of Orthopedic Surgery, Kyoto University, Graduate School of Medicine, Kyoto, Japan. Electronic address: shnk@kuhp.kyoto-u.ac.jp.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Nakamura
authors.affiliation: Center for Musculoskeletal Research, University of Tennessee, Knoxville, TN, USA.
authors.forename: Adrija
authors.initials: A
authors.lastname: Sharma
authors.affiliation: Department of Orthopedic Surgery, Kyoto University, Graduate School of Medicine, Kyoto, Japan.
authors.forename: Hiromu
authors.initials: H
authors.lastname: Ito
authors.affiliation: Department of Orthopedic Surgery, Tamatsukuri-Koseinenkin Hospital, Matsue, Shimane, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Nakamura
authors.affiliation: Center for Musculoskeletal Research, University of Tennessee, Knoxville, TN, USA.
authors.forename: Richard D
authors.initials: RD
authors.lastname: Komistek
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000502:physiology; D005471:Fluoroscopy; D006801:Humans; D007717:Knee / Q000000981:diagnostic imaging / Q000502:physiology; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000502:physiology*; D007720:Knee Prosthesis; D008297:Male; D009068:Movement / Q000502:physiology*; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D012399:Rotation; D013977:Tibia / Q000000981:diagnostic imaging / Q000502:physiology; D016474:Weight-Bearing / Q000502:physiology*
keywords: Deep knee flexion; Fluoroscopy; Knee kinematics; Total knee arthroplasty; Tri-condylar implant