title: Mobile and fixed-bearing (all-polyethylene tibial component) total knee arthroplasty designs: surgical technique.
abstract: BACKGROUND
  Proponents of mobile-bearing total knee arthroplasty believe that it has potential advantages over a fixed-bearing design in terms of diminished wear and improved motion and/or function, but these advantages have not been demonstrated in a randomized clinical comparison to our knowledge. We conducted a patient-blinded, prospective, randomized clinical trial to compare mobile-bearing and fixed-bearing cruciate-substituting total knee arthroplasties of the same design.
  
  
  METHODS
  Patients between the ages of sixty and eighty-five years were prospectively randomized to receive a cruciate-substituting rotating-platform design or a fixed-bearing design with an all-polyethylene tibial component. There were no significant differences in the demographic characteristics (mean age, 72.2 years; mean American Society of Anesthesiologists score, 2.7; mean body mass index, 31.8 kg/m2) or preoperative clinical or radiographic measures between the groups. Routine clinical and radiographic follow-up measures included the Knee Society score (KSS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Short Form-36 (SF-36) outcome measures.
  
  
  RESULTS
  The results of 312 arthroplasties (136 with an all-polyethylene tibial component and 176 rotating-platform designs) in 273 patients were analyzed at a minimum of two years (mean, forty-two months) postoperatively. Although there was significant improvement in both groups, there was no significant difference between the groups with regard to the mean postoperative range of motion (110.9° and 109.1°, respectively; p = 0.21), the mean KSS clinical score (90.4 and 88.2 points; p = 0.168), or the mean KSS pain score (44.9 and 43.1 points; p = 0.108) at this follow-up point. There were ten revisions: seven because of infection, one because of patellar fracture, one because of instability, and one because of aseptic loosening.
  
  
  CONCLUSIONS
  The two designs functioned equivalently at the time of early follow-up in this low-to-moderate-demand patient group. The rotating-platform design had no significant clinical advantage over the design with the all-polyethylene tibial component.
authors.affiliation: Department of Orthopaedic Surgery, University of Minnesota Medical Center, 2450 Riverside Avenue South, R200, Minneapolis, MN 55454, USA. jtluna@umn.edu
authors.forename: Jeffrey T
authors.initials: JT
authors.lastname: Luna
authors.forename: Jonathan N
authors.initials: JN
authors.lastname: Sembrano
authors.forename: Terence J
authors.initials: TJ
authors.lastname: Gioe
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D020370:Osteoarthritis, Knee / Q000175:diagnosis / Q000601:surgery*; D010147:Pain Measurement; D011095:Polyethylenes / Q000494:pharmacology*; D011446:Prospective Studies; D011474:Prosthesis Design; D019919:Prosthesis Implantation / Q000379:methods; D016059:Range of Motion, Articular / Q000502:physiology; D020127:Recovery of Function; D018570:Risk Assessment; D012720:Severity of Illness Index; D016037:Single-Blind Method; D016896:Treatment Outcome
chemical_list: D011095:Polyethylenes