title: Registry outcomes of unicompartmental knee arthroplasty revisions.
abstract: Perceptions of the difficulty and outcome of unicompartmental knee arthroplasty revision (rev-UKA) vary. We analyzed differences in the complexity, cost, and survival of rev-UKAs compared with revision TKAs (rev-TKA). One hundred eighty knee arthroplasty revisions (68 rev-UKAs/112 rev-TKAs), defined as a minimum of tibial or femoral component revision, were identified from a community joint registry of 7587 knee implants performed between 1991 and 2005. Four of 68 rev-UKAs (5.9%) were revised a second time, whereas seven of 112 rev-TKAs (6.3%) were rerevised. Rev-TKA was predictably more complex than rev-UKA based on the proxies of operative time, use of modular augmentation and stems, and polyethylene liner thickness. Thirty-nine of 68 rev-UKAs (57%) had no form of augmentation and were revised as primary TKAs. There were more rev-TKAs than rev-UKAs with an implant cost greater than $5200 (42% versus 12%) and hospital charges greater than $33,000 (48% versus 25%). We found no difference in survival between the groups. Although rev-UKAs had less surgical complexity and bone loss at the time of revision compared with rev-TKAs, we were unable to show improved survival of rev-UKAs compared with rev-TKAs. Rev-UKAs were associated with lower implant costs and hospital charges compared with rev-TKAs.
  
  
  METHODS
  Level II, prognostic study.
authors.affiliation: Department of Orthopaedic Surgery, University of Minnesota, Minneapolis, MN, USA.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Dudley
authors.forename: Terence J
authors.initials: TJ
authors.lastname: Gioe
authors.forename: Penny
authors.initials: P
authors.lastname: Sinner
authors.forename: Susan
authors.initials: S
authors.lastname: Mehle
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000191:economics / Q000379:methods / Q000401:mortality; D005260:Female; D017722:Hospital Charges; D006801:Humans; D007720:Knee Prosthesis / Q000191:economics; D008297:Male; D008875:Middle Aged; D012042:Registries; D012086:Reoperation