title: Failure rates of stemmed metal-on-metal hip replacements: analysis of data from the National Joint Registry of England and Wales.
abstract: BACKGROUND
  Total hip replacement (THR) is extremely common. Some prostheses fail, particularly in younger patients, and need to be revised, most commonly for loosening secondary to wear or dislocation. Surgeons have tried to address these problems by implanting large diameter metal-on-metal bearing surfaces. Our aim was to assess if metal-on-metal bearing surfaces lead to increased implant survival compared with other bearing surfaces in stemmed THR and, additionally, if larger head sizes result in improved implant survival.
  
  
  METHODS
  We analysed the National Joint Registry of England and Wales for primary hip replacements (402,051, of which 31,171 were stemmed metal-on-metal) undertaken between 2003 and 2011. Our analysis was with a multivariable flexible parametric survival model to estimate the covariate-adjusted cumulative incidence of revision adjusting for the competing risk of death.
  
  
  RESULTS
  Metal-on-metal THR failed at high rates. Failure was related to head size, with larger heads failing earlier (3·2% cumulative incidence of revision [95% CI 2·5-4·1] for 28 mm and 5·1% [4·2-6·2] for 52 mm head at 5 years in men aged 60 years). 5 year revision rates in younger women were 6·1% (5·2-7·2) for 46 mm metal-on-metal compared with 1·6% (1·3-2·1) for 28 mm metal-on-polyethylene. By contrast, for ceramic-on-ceramic articulations larger head sizes were associated with improved survival (5 year revision rate of 3·3% [2·6-4·1] with 28 mm and 2·0% [1·5-2·7] with 40 mm for men aged 60 years).
  
  
  CONCLUSIONS
  Metal-on-metal stemmed articulations give poor implant survival compared with other options and should not be implanted. All patients with these bearings should be carefully monitored, particularly young women implanted with large diameter heads. Since large diameter ceramic-on-ceramic bearings seem to do well we support their continued use.
  
  
  BACKGROUND
  National Joint Registry of England and Wales.
authors.affiliation: Orthopaedic Surgery, Musculoskeletal Research Unit, School of Clinical Sciences, University of Bristol, Bristol, UK. alison.smith@bristol.ac.uk
authors.forename: Alison J
authors.initials: AJ
authors.lastname: Smith
authors.forename: Paul
authors.initials: P
authors.lastname: Dieppe
authors.forename: Kelly
authors.initials: K
authors.lastname: Vernon
authors.forename: Martyn
authors.initials: M
authors.lastname: Porter
authors.forename: Ashley W
authors.initials: AW
authors.lastname: Blom
mesh_terms: D000367:Age Factors; D000368:Aged; D002516:Ceramics; D003627:Data Interpretation, Statistical; D004739:England; D019544:Equipment Failure Analysis / Q000706:statistics & numerical data*; D005260:Female; D006622:Hip Prosthesis / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008670:Metals; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000601:surgery*; D020959:Polyethylene; D011474:Prosthesis Design / Q000706:statistics & numerical data*; D017755:Prosthesis Fitting; D012042:Registries / Q000706:statistics & numerical data*; D012737:Sex Factors; D014852:Wales
chemical_list: D008670:Metals; D020959:Polyethylene