title: All-polyethylene tibial components are equal to metal-backed components: systematic review and meta-regression.
abstract: BACKGROUND
  Less than 1% of all primary TKAs are performed with an all-polyethylene tibial component, although recent studies indicate all-polyethylene tibial components are equal to or better than metal-backed ones.
  
  
  OBJECTIVE
  We asked whether the metal-backed tibial component was clinically superior to the all-polyethylene tibial component in primary TKAs regarding revision rates and clinical functioning, and which modifying variables affected the revision rate.
  
  
  METHODS
  We systematically reviewed the literature for clinical studies comparing all-polyethylene and metal-backed tibial components used in primary TKAs in terms of revision rates, clinical scores, and radiologic parameters including radiostereometric analysis (RSA). Meta-regression techniques were used to explore factors modifying the observed effect. Our search yielded 1557 unique references of which 26 articles were included, comprising more than 12,500 TKAs with 231 revisions for any reason.
  
  
  RESULTS
  Meta-analysis showed no differences between the all-polyethylene and metal-backed components except for higher migration of the metal-backed components. Meta-regression showed strong evidence that the all-polyethylene design has improved with time compared with the metal-backed design.
  
  
  CONCLUSIONS
  The all-polyethylene components were equivalent to metal-backed components regarding revision rates and clinical scores. The all-polyethylene components had better fixation (RSA) than the metal-backed components. The belief that metal-backed components are better than all-polyethylene ones seems to be based on studies from earlier TKAs. This might no longer be true for modern TKAs.
  
  
  METHODS
  Level II, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
authors.affiliation: Department of Orthopaedics, Leiden University Medical Center, Postal Code J11R, PO Box 9600, 2300 RC Leiden, The Netherlands. K.A.Nouta@lumc.nl
authors.forename: Klaas Auke
authors.initials: KA
authors.lastname: Nouta
authors.forename: Wiebe C
authors.initials: WC
authors.lastname: Verra
authors.forename: Bart G
authors.initials: BG
authors.lastname: Pijls
authors.forename: Jan W
authors.initials: JW
authors.lastname: Schoones
authors.forename: Rob G H H
authors.initials: RG
authors.lastname: Nelissen
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D005260:Female; D005548:Foreign-Body Migration / Q000209:etiology / Q000601:surgery; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D008670:Metals; D008875:Middle Aged; D020959:Polyethylene; D011474:Prosthesis Design; D011475:Prosthesis Failure; D020127:Recovery of Function; D012086:Reoperation; D018570:Risk Assessment; D012307:Risk Factors; D013977:Tibia / Q000503:physiopathology / Q000601:surgery*; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D008670:Metals; D020959:Polyethylene