title: Does bearing design influence midterm survivorship of unicompartmental arthroplasty?
abstract: Medial unicompartmental arthroplasties (UKA) are available with mobile- and fixed-bearing designs, with the advantages of one bearing over another unproven. We questioned whether the bearing design influenced clinical outcome, survivorship, the reason for revision, or the timing of failures. We retrospectively reviewed 179 patients (229 knees) who had medial unicompartmental knee arthroplasties between 1990 and 2007; of these 79 knees had a mobile-bearing design and 150 knees a fixed-bearing design. Patients with mobile-bearing UKA had a minimum followup of 1 year (mean, 3.6 years; range, 1-11.3 years); those with fixed-bearing UKA a minimum followup of 1 year (mean, 8.1 years; range, 1-17.8 years). Patients were evaluated with clinical outcome scores and radiographically using the Knee Society rating system. Seven of 79 (9%) mobile-bearing knees underwent revision at a mean of 2.6 years, and 22 of 150 (15%) fixed-bearing knees underwent revision at a mean of 6.9 years. The 5-year cumulative survival rates were 88% (SE +/- 0.47, 95% CI 0.7229-1) and 96% (SE +/- 0.16, 95% CI 0.93-0.9979) for the mobile- and fixed-bearing designs respectively using the endpoint of revision surgery. We observed no differences in the indications or complexity of revision surgery between the groups and none in midterm survivorship.
  
  
  METHODS
  Level III, comparative study. See Guidelines for Authors for a complete description of levels of evidence.
authors: University Hospital, London Health Sciences Centre, London, Ontario, Canada. jpwhittaker1@gmail.com
authors: John-Paul
authors: JP
authors: Whittaker
authors: Douglas D R
authors: DD
authors: Naudie
authors: James P
authors: JP
authors: McAuley
authors: Richard W
authors: RW
authors: McCalden
authors: Steven J
authors: SJ
authors: MacDonald
authors: Robert B
authors: RB
authors: Bourne
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation* / Q000379:methods; D005260:Female; D005271:Femur Head Necrosis / Q000601:surgery; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D017063:Outcome Assessment, Health Care; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011859:Radiography; D020127:Recovery of Function; D012086:Reoperation / Q000706:statistics & numerical data; D012189:Retrospective Studies; D016896:Treatment Outcome