title: Common causes of failed unicompartmental knee arthroplasty: a single-centre analysis of four hundred and seventy one cases.
abstract: OBJECTIVE
  We performed this retrospective study to determine the main causes for early and late failures of unicompartmental knee arthroplasty (UKA).
  
  
  METHODS
  Between January 2000 and March 2012, all patients treated for a failed medial UKA in the authors' institution were retrospectively reviewed. A total of 471 patients were identified, and causes of failure were analysed based on the medical records and radiographs at the time of revision.
  
  
  RESULTS
  The cohort included 161 males and 310 females, with a mean age of 67.7 years (range, 42-91 years; SD = 10.1) at the time of revision. The mean time from index arthroplasty to revision surgery was 6.1 years (range, 0.1-27.9 years; SD = 5.6). A total of 254 cases (53.9 %) failed within five years after primary implantation, and 108 cases (22.9 %) failed after ten years. The major reason for failure was the development of other compartment arthritis (39.5 %), followed by aseptic loosening (25.4 %).
  
  
  CONCLUSIONS
  Of importance, the mean time to failure after UKA was 6.1 years, with more than 50 % of failures occurring within the first five years postoperatively.
authors.affiliation: Department of Orthopaedic Surgery, Helios Endo-Kinik Hamburg, Hamburg, Germany, mcitak@gmx.de.
authors.forename: Mustafa
authors.initials: M
authors.lastname: Citak
authors.forename: Kathrin
authors.initials: K
authors.lastname: Dersch
authors.forename: Atul F
authors.initials: AF
authors.lastname: Kamath
authors.forename: Carl
authors.initials: C
authors.lastname: Haasper
authors.forename: Thorsten
authors.initials: T
authors.lastname: Gehrke
authors.forename: Daniel
authors.initials: D
authors.lastname: Kendoff
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods* / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D017211:Treatment Failure