title: Fixed- versus mobile-bearing unicondylar knee arthroplasty: are failure modes different?
abstract: OBJECTIVE
  An ongoing controversy exists on whether mobile-bearing design is superior over fixed-bearing design in unicondylar knee arthroplasties (UKAs). The present study conducted a systematic review to ascertain differences in performance between fixed- and mobile-bearing designs in UKAs.
  
  
  METHODS
  A literature search was performed in PubMed, Embase, Scopus and the Cochrane Library. A total of 9 comparative studies involving 915 knees comparing outcomes of mobile-bearing UKAs with fixed-bearing UKAs were included in the current analysis. Outcomes of interest included knee function, quality of life, radiographic outcomes, reasons and incidence of reoperation, timing of failures, and survivorship.
  
  
  RESULTS
  The results presented no significant differences between the two designs in terms of knee scores, range of motion, limb alignment, implant positioning, incidence of radiolucent lines and overall reoperation rates. However, their differences have been noted in their modes and timing of failures. Early failures are related to the risk of bearing dislocation in the mobile-bearing design. In contrast, later failures are related to the risk of polyethylene wear in the fixed-bearing design.
  
  
  CONCLUSIONS
  The available evidence has not confirmed the advantage of mobile-bearing UKAs over fixed-bearing UKAs but pointed out specific modes of failure.
authors.affiliation: Department of Orthopaedic Surgery, Shanghai Sixth People's Hospital, Shanghai Jiao Tong University School of Medicine, 600 Yisan Road, Shanghai, 200233, People's Republic of China.
authors.forename: Tao
authors.initials: T
authors.lastname: Cheng
authors.forename: Daoyun
authors.initials: D
authors.lastname: Chen
authors.forename: Chen
authors.initials: C
authors.lastname: Zhu
authors.forename: Xiaoyun
authors.initials: X
authors.lastname: Pan
authors.forename: Xin
authors.initials: X
authors.lastname: Mao
authors.forename: Yongyuan
authors.initials: Y
authors.lastname: Guo
authors.forename: Xianlong
authors.initials: X
authors.lastname: Zhang
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee; D005260:Female; D006801:Humans; D007592:Joint Diseases / Q000601:surgery*; D007719:Knee Joint / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure