title: The risk of revision after TKA is affected by previous HTO or UKA.
abstract: BACKGROUND
  High tibial osteotomy (HTO) and unicompartmental arthroplasty (UKA) are reconstructive surgeries advocated for younger patients. In case of failure or progression of osteoarthritis, they can both be converted to a total knee arthroplasty (TKA).
  
  
  OBJECTIVE
  We used registry data to answer if the risks of revision for TKAs after previous HTOs and UKAs differ and how these compare with that of de novo TKAs. Furthermore, we wanted to examine the extent of stemmed/revision implants being used for the conversions.
  
  
  METHODS
  We identified HTOs performed during 1998 to 2007 with the help of the inpatient and outpatient care registries of the Swedish National Board of Health and Welfare and gathered relevant information from hospital records. The Swedish Knee Arthroplasty Register was then examined to find all de novo TKAs, TKAs performed after HTO, and TKAs performed after UKA through the end of 2012.
  
  
  RESULTS
  For 920 TKAs after previous UKA and 356 TKAs after previous closed-wedge HTOs, we found the risk of revision significantly higher than for the 118,229 de novo TKAs (risk ratio, 2.8; confidence interval [CI], 2.2-3.5; p<0.001, and 1.7 CI, 1.1-2.6; p<0.001, respectively), whereas for the 482 open-wedge osteotomies, the difference was not significant (risk ratio, 1.2; CI, 0.8-1.8; p=0.44). Stemmed implants were used in 663 of the 117,566 primary de novo TKAs (0.6%), in 22 of the 809 HTO conversions (4%) and in 136 of the 920 UKA conversions (17%).
  
  
  CONCLUSIONS
  TKAs after previous reconstructive surgery carry an increased risk for revision. However, our findings do not mitigate against the use of UKA and HTO in selected cases.
  
  
  METHODS
  Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.
authors.affiliation: Department of Orthopaedics and Clinical Sciences, SUS/Lund University Hospital, 22185, Lund, Sweden, otto.robertsson@med.lu.se.
authors.forename: Otto
authors.initials: O
authors.lastname: Robertsson
authors.forename: Annette
authors.initials: A
authors.lastname: W-Dahl
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects* / Q000295:instrumentation; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D020370:Osteoarthritis, Knee / Q000175:diagnosis / Q000601:surgery*; D010027:Osteotomy / Q000009:adverse effects*; D018579:Patient Selection; D011183:Postoperative Complications / Q000601:surgery*; D016016:Proportional Hazards Models; D011474:Prosthesis Design; D012042:Registries; D012086:Reoperation; D018570:Risk Assessment; D012307:Risk Factors; D013548:Sweden; D013977:Tibia / Q000601:surgery*; D013997:Time Factors; D016896:Treatment Outcome