title: Unicompartmental knee arthroplasty modes of failure: wear is not the main reason for failure: a multicentre study of 418 failed knees.
abstract: BACKGROUND
  This study originated from a symposium held by the French Hip and Knee Society (Société française de la hanche et du genou [SFHG]) and was carried out to better assess the distribution of causes of unicompartmental knee arthroplasty (UKA) failures, as well as cause-specific delay to onset.
  
  
  OBJECTIVE
  Our working hypothesis was that most failures were traceable to wear occurring over a period of many years.
  
  
  METHODS
  A multicentre retrospective study (25 centres) was conducted in 418 failed UKAs performed between 1978 and 2009. We determined the prevalence and time to onset of the main reasons for revision surgery based upon available preoperative findings. Additional intraoperative findings were analysed. The results were compared to those of nation wide registries to evaluate the representativeness of our study population.
  
  
  RESULTS
  Times to revision surgery were short: 19% of revisions occurred within the first year and 48.5% within the first 5 years. Loosening was the main reason for failure (45%), followed by osteoarthritis progression (15%) and, finally, by wear (12%). Other reasons were technical problems in 11.5% of cases, unexplained pain in 5.5%, and failure of the supporting bone in 3.6%. The infection rate was 1.9%. Our results were consistent with those of Swedish and Australian registries.
  
  
  CONCLUSIONS
  Our hypothesis was not confirmed. The short time to failure in most cases suggests a major role for surgical technique issues. Morbidity related to the implant per se may be seen as moderate and not greater than with total knee prostheses. The good agreement between our data and those of nationwide registries indicates that our population was representative. A finer analysis is needed, indicating that the establishment of a French registry would be of interest.
authors.affiliation: Private Hospital, 200, rue d'Auvergne, 62700 Bruay Labuissière, France. jae@orthowave.net
authors.forename: J-A
authors.initials: JA
authors.lastname: Epinette
authors.forename: B
authors.initials: B
authors.lastname: Brunschweiler
authors.forename: P
authors.initials: P
authors.lastname: Mertl
authors.forename: D
authors.initials: D
authors.lastname: Mole
authors.forename: A
authors.initials: A
authors.lastname: Cazenave
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects* / Q000379:methods*; D001315:Australia; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D005602:France; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011474:Prosthesis Design / Q000379:methods*; D011475:Prosthesis Failure / Q000639:trends*; D012042:Registries; D012086:Reoperation / Q000379:methods; D012189:Retrospective Studies; D018570:Risk Assessment; D013548:Sweden; D013997:Time Factors; D016896:Treatment Outcome