title: How to deal with lost to follow-up in total knee arthroplasty : a new method based on the competing risks approach.
abstract: OBJECTIVE
  The aim of this study was to develop a more accurate method to deal with patients lost to follow-up based on the competing risks approach.
  
  
  METHODS
  A cohort of 112 patients who received 143 primary cemented total knee arthroplasties forms the basis for this study. Follow-up was up to 25 years. The new method for dealing with lost to follow-up accounts for competing events (i.e. death and failure of a prosthesis) using the cumulative incidence estimator and estimates time to event for patients lost to follow-up using national demographic registries. The results of this new method were compared with the worst case scenario estimated by Kaplan-Meier.
  
  
  RESULTS
  Six different situations were identified covering all possible situations in long-term follow-up for total knee arthroplasty. The new method--considering all patients lost to follow-up as revised--showed a twofold reduction in revision rate compared to the traditional worst case scenario using Kaplan-Meier.
  
  
  CONCLUSIONS
  Lost to follow-up should be prevented whenever possible, but this may be unavoidable for long-term follow-up studies. In situations where lost to follow-up does occur, the new proposed method offers an efficient and valid approach to deal with this problem.
authors.affiliation: Department of Orthopaedics, Leiden University Medical Center, Postal code J11R, P.O. Box 9600, 2300 RC, Leiden, The Netherlands, kanouta@hotmail.com.
authors.forename: Klaas-Auke
authors.initials: KA
authors.lastname: Nouta
authors.forename: Bart G
authors.initials: BG
authors.lastname: Pijls
authors.forename: Marta
authors.initials: M
authors.lastname: Fiocco
authors.forename: J Christiaan
authors.initials: JC
authors.lastname: Keurentjes
authors.forename: Rob G H H
authors.initials: RG
authors.lastname: Nelissen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee; D003663:Decision Trees; D005260:Female; D006801:Humans; D059012:Lost to Follow-Up; D008297:Male; D008875:Middle Aged