title: Unicompartmental knee arthroplasty in patients aged less than 65.
abstract: OBJECTIVE
  In recent years, there has been renewed interest in using unicompartmental knee arthroplasty (UKA). Several studies have reported increasing numbers of UKAs for osteoarthritis in patients who are less than 65 years of age, with low revision rates. To describe and compare the use and outcome of UKA in this age group, we have combined data from the Australian and Swedish knee registries.
  
  
  METHODS
  More than 34,000 UKA procedures carried out between 1998 and 2007 were analyzed, and we focused on over 16,000 patients younger than 65 years to determine usage and to determine differences in the revision rate. Survival analysis was used to determine outcomes of revision related to age and sex, using any reason for revision as the endpoint.
  
  
  RESULTS
  Both countries showed a decreasing use of UKA in recent years in terms of the proportion of knee replacements and absolute numbers undertaken per year. The 7-year cumulative risk of revision of UKA in patients younger than 65 years was similar in the two countries. Patients younger than 55 years had a statistically significantly higher cumulative risk of revision than patients aged 55 to 64 years (19% and 12%, respectively at 7 years). The risk of revision in patients less than 65 years of age was similar in both sexes.
  
  
  CONCLUSIONS
  The results of the combined UKA data from the Australian and Swedish registries show a uniformity of outcome between countries with patients aged less than 65 having a higher rate of revision than patients who were 65 or older. Surgeons and patients should be aware of the higher risk of revision in this age group.
authors.affiliation: Department of Orthopaedics, Clinical Sciences Lund, Lund University Hospital, Sweden. annette.w-dahl@med.lu.se
authors.forename: Annette
authors.initials: A
authors.lastname: W-Dahl
authors.forename: Otto
authors.initials: O
authors.lastname: Robertsson
authors.forename: Lars
authors.initials: L
authors.lastname: Lidgren
authors.forename: Lisa
authors.initials: L
authors.lastname: Miller
authors.forename: David
authors.initials: D
authors.lastname: Davidson
authors.forename: Stephen
authors.initials: S
authors.lastname: Graves
mesh_terms: D000328:Adult; D000367:Age Factors; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000379:methods; D001315:Australia; D006801:Humans; D007720:Knee Prosthesis / Q000009:adverse effects; D008875:Middle Aged; D011475:Prosthesis Failure; D012042:Registries; D012086:Reoperation; D012307:Risk Factors; D013548:Sweden; D016896:Treatment Outcome