title: Micromotion in cemented rotating platform total knee arthroplasty: cemented tibial stem versus hybrid fixation.
abstract: BACKGROUND
  Improving the longevity and reliability of cemented total knee arthroplasty (TKA) remains a major step to achieve. It is still unclear, whether a cemented tibial stem reduces micromotion of the tibial tray and produces therefore a better initial stability or not. The higher conformity of rotating platform design and the possible rotary forces to the tibial platform may produce higher micromotion when the tibial stem remains cementless (hybrid fixation).
  
  
  METHODS
  An in vitro study was performed using the PFC mobile bearing tibial tray (DePuy, Warswa, IN, USA) to test the hypothesis that the addition of cement surrounding the tibial stem reduces micromotion of the tibial tray in cemented TKA with mobile bearing design. Ten tibial trays with mobile design were implanted in sawbones with a 3-mm cement mantle beneath the baseplate of the tibial tray and with or without the cemented stem. Tibial trays were loaded additionally in the ventral, lateral, medial and posterior positions with 2,500 N using the Zwick Z010 instrumentation and HBM pick up Hottinger Baldwin.
  
  
  RESULTS
  In this study, a significant increased mean maximum liftoff was found when only cementing the tibial baseplate (hybrid fixation), compared to the fully cemented tibial tray (P<0.02).
  
  
  CONCLUSIONS
  In conclusion, the stem of mobile bearing tibial components should be cemented to provide increased micromotion and earlier loosening.
authors.affiliation: Department of Orthopaedic Surgery, University of Regensburg, Kaiser-Karl-V. Allee 3, 93077, Bad Abbach, Germany. c_luering@yahoo.de
authors.forename: C
authors.initials: C
authors.lastname: Luring
authors.forename: L
authors.initials: L
authors.lastname: Perlick
authors.forename: C
authors.initials: C
authors.lastname: Trepte
authors.forename: O
authors.initials: O
authors.lastname: Linhardt
authors.forename: C
authors.initials: C
authors.lastname: Perlick
authors.forename: W
authors.initials: W
authors.lastname: Plitz
authors.forename: J
authors.initials: J
authors.lastname: Grifka
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation* / Q000379:methods; D001843:Bone Cements; D002484:Cementation / Q000295:instrumentation* / Q000379:methods; D019544:Equipment Failure Analysis; D006801:Humans; D066298:In Vitro Techniques; D016268:Internal Fixators; D011474:Prosthesis Design; D011475:Prosthesis Failure; D013977:Tibia / Q000601:surgery*
chemical_list: D001843:Bone Cements