Forgot your password ?




SICOT e-Newsletter

Issue No. 56 - May 2013

Worldwide News


TKA: Similar revision rates and outcomes for all-polyethylene and metal-backed components

Title: All-polyethylene tibial components are equal to metal-backed components: systematic review and Meta regression

Authors: Nouta KA, Verra WC, Pijls BG, Schoones JW, Nelissen RG,
Department of Orthopaedics, Leiden University Medical Center, Postal Code J11R, PO Box 9600, 2300 RC Leiden, The Netherlands

Clin Orthop Relat Res. 2012 Dec;470(12):3549-59.
doi: 10.1007/s11999-012-2582-2. Epub 2012 Sep 13
Published Date : December 2012
Level of evidence: Level II - Meta-analysis
PMID: 22972656
Type of Study: Meta analysis

Synopsis

26 articles (12,500 TKAs with 231 revisions) were identified to compare the clinical outcomes (revision rates and clinical functioning) of metal-backed and all-polyethylene tibial component in primary TKAs. Results indicated that there were no differences in revision rates or outcome scores between the two components, except for higher migration of the metal-backed components and less migration of all-polyethylene components.


Why was this study needed now?

While metal-backed tibial components are used in the majority of TKAs, the all-polyethylene component has been frequently recommended. However, it is unclear whether one component would display a superior performance over the other. Hence, this systematic review aims to investigate whether the metal-backed tibial component would be clinically superior to the all-polyethylene tibial component in primary TKA in terms of revision rates and clinical functioning. Additionally, this systematic review focuses on determining which modifying variables would affect the revision rate.


What was the principal research question?

Does the metal-backed tibial component provide clinically superior outcomes compared to the all-polyethylene tibial component in primary TKAs with regards to revision rates and clinical functioning?


Study Criteria

  1. The following databases were searched: PubMed, Embase, Web of Science, Cochrane, CINAHL, and Academic Search Premier. Furthermore, the journal databases for Science Direct and Wiley-Blackwell were searched.
  2. Index Terms: Index terms included: "polyethylene", "arthroplasty", and "knee replacement".
  3. Study Selection: The articles had to meet the following inclusion criteria: 
    1. The study had to be a comparative study.
    2. The intervention(s) assessed had to be all-polyethylene and metal-backed tibial components in primary TKAs for end-stage osteoarthritis or rheumatoid arthritis with the results separately reported.
    3. The metal-backed tibial components needed to have a fixed-bearing design.
    4. Outcome measurements in the studies had to include survival rates, clinical measurements, or functional measurements with minimal follow-up of 6 months. The articles were excluded if: 1) The study did not meet the inclusion criteria for title and abstract, and 2) the population had been reported in another included study).
  4. Data Extraction: Two reviewers (KAN, WCV) independently extracted data concerning summary patient demographics, methods, interventions, and outcomes. Disagreements in study and data extraction were resolved through consensus with a third reviewer (BGP).
  5. Data Synthesis: The 26 selected articles (11 RCTs and 15 non-RCTs) comprised of 2700 all-polyethylene and 9978 fixed-bearing metal-backed tibial components used in TKAs with 231 revisions for any reason. The review tested heterogeneity between studies with the I-squared statistic. Possible sources of heterogeneity were explored through meta-regression using the random-effects regression model. The random-effects model was used to combine all data for meta-analysis according to the pooled Mantel-Haenszel test for risk differences (RDs) and the pooled standard error for mean differences (MDs). Metafor package for R Version 2.13 was used to perform all analyses.


What were the important findings?

  • No differences in revision rates were displayed between the two tibial components; the revision rates were 0.975 (95% CI, 0.959-0.992) for the all-polyethylene component and 0.973 (95% CI, 0.959-0.988) for the metal-backed component.
  • The meta-regression for the primary outcome indicated an improvement in the all-polyethylene component with time compared with the metal-backed component. 
  • No differences were displayed in the secondary outcome measurements: ROM, The Knee Society Score (KSS), and Hospital for Special Surgery (HSS) scores between both components. Additionally, there were no differences in radiographic femorotibial alignment, anterior tibial alignment, and tibial slope between the two types of designs. 
  • All-polyethylene tibial components resulted in less migration compared to metal-backed components as the maximum total point motion (MTPM) for cemented tibial components using radiostereotactic analysis (RSA) indicated a mean difference of -0.29 (95% CI, -0.29, -0.21) favouring the all-polyethylene component.


How will this affect the care of patients?

This review suggests that the use of an all-polyethylene tibial component in TKA is an effective, safe treatment for end-stage osteoarthritis of the knee. However, further studies may be required before reconsidering the use of this component design.


What should I remember most?

There were no clinically relevant differences in revision rates, clinical function, or radiographic variables between the metal-backed and all-polyethylene components.


References:
  1. www.myorthoevidence.com
  2. Pubmed: www.ncbi.nlm.nih.gov/pubmed/22972656
  3. Clinical Orthopaedics and Related Research, Volume 470, Issue 12, pp 3549-3559