title: International comparative evaluation of fixed-bearing non-posterior-stabilized and posterior-stabilized total knee replacements.
abstract: BACKGROUND
  Differences in survivorship of non-posterior-stabilized compared with posterior-stabilized knee designs carry substantial economic consequences, especially with limited health-care resources. However, these comparisons have often been made between relatively small groups of patients, often with short-term follow-up, with only small differences demonstrated between the groups. The goal of this study is to compare the outcomes of non-posterior-stabilized and posterior-stabilized total knee arthroplasties with use of a unique collaboration of multiple established knee arthroplasty registries.
  
  
  METHODS
  A distributed health data network was developed by the International Consortium of Orthopaedic Registries and was used in this study to reduce barriers to participation (such as security, propriety, legal, and privacy issues) compared with a centralized data warehouse approach. The study included only replacements in osteoarthritis patients who underwent total knee procedures involving fixed-bearing devices from 2001 to 2010. The outcome of interest was time to first revision.
  
  
  RESULTS
  On average, not resurfacing showed a more harmful effect than resurfacing did when posterior-stabilized and non-posterior-stabilized knee replacements were compared, while the risk of revision for posterior-stabilized compared with non-posterior-stabilized knees was highest in year zero to one, followed by year one to two, years eight through ten, and years two through eight. Posterior-stabilized knees did significantly worse than non-posterior-stabilized knees did when the patella was not resurfaced. This difference was most pronounced in the first two years (year zero to one: hazard ratio [HR] = 2.15, 95% confidence interval [CI] = 1.56 to 2.95, p < 0.001; year one to two: HR = 1.61, 95% CI = 1.48 to 1.75, p < 0.001). When the patella was resurfaced, posterior-stabilized knees did significantly worse than non-posterior-stabilized knees did. This was again most pronounced in the first two years (year zero to one: HR = 1.75, 95% CI = 1.27 to 2.42, p = 0.001; year one to two: HR = 1.31, 95% CI = 1.19 to 1.45, p < 0.001). There was a reduced risk of revision with a patient age of more than sixty-five years (HR = 0.57, 95% CI = 0.55 to 0.60, p < 0.001).
  
  
  CONCLUSIONS
  We found that fixed non-posterior-stabilized total knee arthroplasty performed better with or without patellar resurfacing than did fixed posterior-stabilized total knee arthroplasty. This effect was most pronounced in the first two years. The risk of revision for posterior-stabilized total knee arthroplasties was reduced with patellar resurfacing. Also, a patient age of more than sixty-five years and female gender reduced the risk of revision.
authors.affiliation: HealthEast Joint Registry (HEJR), 1690 University Avenue West, Data Science, Suite 400, Minneapolis, MN 55104.
authors.forename: Thomas
authors.initials: T
authors.lastname: Comfort
authors.affiliation: The Norwegian Arthroplasty Register, Department of Orthopaedic Surgery, Haukeland University Hospital, Mollendalsbakken 11, N-5021 Bergen, Norway.
authors.forename: Valborg
authors.initials: V
authors.lastname: Baste
authors.affiliation: Facultat de Medicina, Servei de COT, Hospital Universitari de Girona Dr. J. Trueta, Avinguda de França s/n, 17007 Girona, Spain.
authors.forename: Miquel Angel
authors.initials: MA
authors.lastname: Froufe
authors.affiliation: 6670 Alton Parkway, Irvine, CA 92618.
authors.forename: Robert
authors.initials: R
authors.lastname: Namba
authors.affiliation: Register of the Orthopaedic Prosthetic Implants (RIPO), c/o Medical Technology Laboratory, Istituto Ortopedico Rizzoli, Via di Barbiano 1/10, 40136 Bologna, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Bordini
authors.affiliation: The Swedish Knee Arthroplasty Register, Department of Orthopedics, Clinical Sciences, SUS/Lund University Hospital, 221 85 Lund, Sweden.
authors.forename: Otto
authors.initials: O
authors.lastname: Robertsson
authors.affiliation: Surgical Outcomes & Analysis Department, Kaiser Permanente, 8954 Rio San Diego Drive, Suite 406, San Diego, CA 92108.
authors.forename: Guy
authors.initials: G
authors.lastname: Cafri
authors.affiliation: Surgical Outcomes & Analysis Department, Kaiser Permanente, 8954 Rio San Diego Drive, Suite 406, San Diego, CA 92108.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Paxton
authors.affiliation: Weill Cornell Medical College, 402 East 67th Street, New York, NY 10065.
authors.forename: Art
authors.initials: A
authors.lastname: Sedrakyan
authors.affiliation: Australian Orthopaedic Association National Joint Replacement Registry, Discipline of Public Health, MDP DX 650 511, University of Adelaide, Adelaide, SA 5005, Australia.
authors.forename: Stephen
authors.initials: S
authors.lastname: Graves
mesh_terms: D000367:Age Factors; D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007719:Knee Joint / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery*; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012042:Registries; D012086:Reoperation; D012307:Risk Factors; D012737:Sex Factors; D016896:Treatment Outcome