title: Kinematics and early migration in single-radius mobile- and fixed-bearing total knee prostheses.
abstract: BACKGROUND
  The mobile-bearing variant of a single-radius design is assumed to provide more freedom of motion compared to the fixed-bearing variant because the insert does not restrict the natural movements of the femoral component. This would reduce the contact stresses and wear which in turn may have a positive effect on the fixation of the prosthesis to the bone and thereby decreases the risk for loosening. The aim of this study was to evaluate early migration of the tibial component and kinematics of a mobile-bearing and fixed-bearing total knee prosthesis of the same single-radius design.
  
  
  METHODS
  Twenty Triathlon single-radius posterior-stabilized knee prostheses were implanted (9 mobile-bearing and 11 fixed-bearing). Fluoroscopy and roentgen stereophotogrammetric analysis (RSA) were performed 6 and 12 months post-operatively.
  
  
  RESULTS
  The 1 year post-operative RSA results showed considerable early migrations in 3 out of 9 mobile-bearing patients and 1 out of 11 fixed-bearing patients. The range of knee flexion was the same for the mobile-bearing and fixed-bearing group. The mobile insert was following the femoral component during motion.
  
  
  CONCLUSIONS
  Despite the mobile insert following the femoral component during motion, and therefore performing as intended, no kinematic advantages of the mobile-bearing total knee prosthesis were seen. The fixed-bearing knee performed as good as the mobile-bearing knee and maybe even slightly better based on less irregular kinematics and less early migrations.
authors: Department of Orthopaedics, Leiden University Medical Center, Leiden, The Netherlands.
authors: N
authors: N
authors: Wolterbeek
authors: E H
authors: EH
authors: Garling
authors: B J
authors: BJ
authors: Mertens
authors: R G H H
authors: RG
authors: Nelissen
authors: E R
authors: ER
authors: Valstar
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation* / Q000379:methods; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000209:etiology / Q000503:physiopathology* / Q000601:surgery*; D007719:Knee Joint / Q000503:physiopathology* / Q000601:surgery*; D007720:Knee Prosthesis; D008875:Middle Aged; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D016896:Treatment Outcome