title: Mobile- vs. fixed-bearing total knee replacement.
abstract: OBJECTIVE
  It is unclear whether mobile-bearing (MB) total knee arthroplasties reduce the risk of tibial component loosening compared to fixed-bearing (FB) designs. This randomized study investigated implant migration, periprosthetic bone mineral density (BMD), and patient-reported outcomes (Oxford knee score)-all at 2 years-for the P.F.C. Sigma Cruciate Retaining total knee arthroplasty.
  
  
  METHODS
  50 osteoarthritis patients were allocated to either FB or MB tibial articulation.
  
  
  CONCLUSIONS
  At 2 years, the mean total translation (implant migration) was higher for the FB implant (0.30 mm, SD 0.22) than for the MB implant (0.17 mm, SD 0.09) (p = 0.04). BMD decreased between baseline and 1-year follow-up. At 2-year follow-up, BMD was close to the baseline level. The knee scores of both groups improved equally well. The FB tibial implant migrated more than the MB, but this was not clinically significant. The mobile polyethylene presumably partly absorbs the force transmitted to the metal tibial tray, thereby reducing micromotion.
authors.affiliation: Department of Orthopedics, Horsens Regional Hospital, Horsens.
authors.forename: Michael
authors.initials: M
authors.lastname: Tjørnild
authors.forename: Kjeld
authors.initials: K
authors.lastname: Søballe
authors.forename: Per Møller
authors.initials: PM
authors.lastname: Hansen
authors.forename: Carsten
authors.initials: C
authors.lastname: Holm
authors.forename: Maiken
authors.initials: M
authors.lastname: Stilling
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D015519:Bone Density; D016723:Bone Remodeling; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery*; D011474:Prosthesis Design; D011475:Prosthesis Failure; D059869:Radiostereometric Analysis; D016059:Range of Motion, Articular; D016896:Treatment Outcome