title: Mixing of components from different manufacturers in total hip arthroplasty: prevalence and comparative outcomes.
abstract: OBJECTIVE
  There have recently been highly publicized examples of suboptimal outcomes with some newer implant designs used for total hip replacement. This has led to calls for tighter regulation. However, surgeons do not always adhere to the regulations already in place and often use implants from different manufacturers together to replace a hip, which is against the recommendations of the Medicines and Healthcare Products Regulatory Agency (MHRA) and the directions of the manufacturers.
  
  
  METHODS
  We used data from the National Joint Registry of England and Wales (NJR) to investigate this practice.
  
  
  RESULTS
  Mixing of components was common, and we identified over 90,000 cases recorded between 2003 and 2013. In the majority of these cases (48,156), stems and heads from one manufacturer were mixed with polyethylene cemented cups from another manufacturer. When using a cemented stem and a polyethylene cup, mixing of stems from one manufacturer with cups from another was associated with a lower revision rate. At 8 years, the cumulative percentage of revisions was 1.9% (95% CI: 1.7-2.1) in the mixed group as compared to 2.4% (2.3-2.5) in the matched group (p = 0.001). Mixing of heads from one manufacturer with stems from another was associated with a higher revision rate (p < 0.001). In hip replacements with ceramic-on-ceramic or metal-on-metal bearings, mixing of stems, heads, and cups from different manufacturers was associated with similar revision rates (p > 0.05).
  
  
  CONCLUSIONS
  Mixing of components from different manufacturers is a common practice, despite the fact that it goes against regulatory guidance. However, it is not associated with increased revision rates unless heads and stems from different manufacturers are used together.
authors.affiliation: a 1 Spire Hospital Norwich , Norwich.
authors.forename: Keith
authors.initials: K
authors.lastname: Tucker
authors.affiliation: b 2 Craneswater Consulting , Locks Heath.
authors.forename: Martin
authors.initials: M
authors.lastname: Pickford
authors.affiliation: c 3 Northgate Information Solutions Ltd , Hemel Hemstead.
authors.forename: Claire
authors.initials: C
authors.lastname: Newell
authors.affiliation: d 4 Derby Hospitals Foundation Trust , Derby.
authors.forename: Peter
authors.initials: P
authors.lastname: Howard
authors.affiliation: e 5 Musculoskeletal Research, University of Bristol , Bristol, UK.
authors.forename: Linda P
authors.initials: LP
authors.lastname: Hunt
authors.affiliation: e 5 Musculoskeletal Research, University of Bristol , Bristol, UK.
authors.forename: Ashley W
authors.initials: AW
authors.lastname: Blom
mesh_terms: D019644:Arthroplasty, Replacement, Hip / Q000706:statistics & numerical data*; D004739:England; D006622:Hip Prosthesis / Q000706:statistics & numerical data*; D006801:Humans; D015995:Prevalence; D011474:Prosthesis Design / Q000706:statistics & numerical data; D011475:Prosthesis Failure; D060489:Prosthesis Retention / Q000295:instrumentation / Q000706:statistics & numerical data; D012042:Registries; D016896:Treatment Outcome; D014852:Wales