title: Femoro-tibial kinematics after TKA in fixed- and mobile-bearing knees in the sagittal plane.
abstract: OBJECTIVE
  Lack of the anterior cruciate ligament in total knee arthroplasty results in paradoxical movement of the femur as opposed to the tibia under deep flexion. Total knee arthroplasty with mobile-bearing inlays has been developed to provide increased physiological movement of the knee joint and to reduce polyethylene abrasion. The aim of this study was to perform an in vitro analysis of the kinematic movement in the sagittal plane in order to show differences between fixed- and mobile-bearing TKA in comparison with the natural knee joint.
  
  
  METHODS
  Seven knee joints of human cadaver material were used in a laboratory experiment. Fixed- and mobile-bearing inlays were tested in sequences under isokinetic extension in so-called kinemator for knee joints, which can simulate muscular traction power by the use of hydraulic cylinders, which crossover the knee joint. As a target parameter, the a.p. translation of the tibio-femoral relative movement was measured in the sagittal plane under ultrasound (Zebris) control.
  
  
  RESULTS
  The results show a reduced tibial a.p. translation in relation to the femur in the bearing group compared to the natural joint. In the Z-axis, between 110° and 50° of flexion, linear movement decreases towards caudal movement under extension. Admittedly, the study did not show differences in the movement pattern between "mobile-bearing" and "fixed-bearing" prostheses.
  
  
  CONCLUSIONS
  Results of this study cannot prove functional advantages of mobile-bearing prostheses for the knee joint kinematic after TKA. Both types of prostheses show typical kinematics of an anterior instability, hence they were incapable of performing physiological movement.
authors.affiliation: Department of Orthopaedic Surgery, Hannover Medical School, Anna-von-Borries-Strasse 1-7, Hannover, Germany, kraj@gmx.net.
authors.forename: Kiriakos
authors.initials: K
authors.lastname: Daniilidis
authors.forename: Steffen
authors.initials: S
authors.lastname: Höll
authors.forename: Georg
authors.initials: G
authors.lastname: Gosheger
authors.forename: Ralf
authors.initials: R
authors.lastname: Dieckmann
authors.forename: Nicolo
authors.initials: N
authors.lastname: Martinelli
authors.forename: Sven
authors.initials: S
authors.lastname: Ostermeier
authors.forename: Carsten O
authors.initials: CO
authors.lastname: Tibesku
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation* / Q000379:methods; D001696:Biomechanical Phenomena; D005269:Femur / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000209:etiology; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D007720:Knee Prosthesis; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000209:etiology*; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D013977:Tibia / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D014463:Ultrasonography