title: Factors affecting the durability of primary total knee prostheses.
abstract: BACKGROUND
  Failure of total knee arthroplasty is problematic. The purpose of this study was to evaluate the factors that influence the durability of a primary total knee prosthesis.
  
  
  METHODS
  A survivorship analysis of 11,606 primary total knee arthroplasties carried out between January 1, 1978, and December 31, 2000, was performed. An analysis of patient and implant-related factors affecting survivorship was done with use of a multivariate Cox model.
  
  
  RESULTS
  The survivorship was 91% (95% confidence interval, 90% to 91%) at ten years (2943 knees), 84% (95% confidence interval, 82% to 86%) at fifteen years (595 knees), and 78% (95% confidence interval, 74% to 81%) at twenty years (104 knees) following the surgery. Prosthetic survivorship at ten years was 83% for patients fifty-five years of age or less compared with 94% for those older than seventy years of age (p < 0.0001), 90% for those with a diagnosis of osteoarthritis compared with 95% for those with inflammatory arthritis (p < 0.005), and 91% for those with retention of the posterior cruciate ligament compared with 76% for those with substitution of the posterior cruciate ligament (a posterior stabilized prosthesis) (p < 0.0001). Survivorship at ten years was 92% for nonmodular metal-backed tibial components, 90% for modular metal-backed tibial components, and 97% for all-polyethylene tibial components (p < 0.0001). Survivorship at ten years was 92% for prostheses fixed with cement compared with 61% for those fixed without cement (p < 0.0001).
  
  
  CONCLUSIONS
  Significant risk factors for failure of total knee arthroplasty were the type of implant, age and gender of the patient, diagnosis, type of fixation, and design of the patellar component. In the ideal situation-treatment of a woman over the age of seventy years who has inflammatory arthritis with a nonmodular, metal-backed tibial component, cement fixation, an all-polyethylene patellar component, and retention of the posterior cruciate ligament-the ten-year survivorship of the prosthesis was estimated to be 98% (95% confidence interval, 97% to 99%).
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic Scottsdale, AZ 85259, USA. rand.james@mayo.edu
authors.forename: James A
authors.initials: JA
authors.lastname: Rand
authors.forename: Robert T
authors.initials: RT
authors.lastname: Trousdale
authors.forename: Duane M
authors.initials: DM
authors.lastname: Ilstrup
authors.forename: W Scott
authors.initials: WS
authors.lastname: Harmsen
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001168:Arthritis / Q000601:surgery*; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000379:methods / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000601:surgery*; D007720:Knee Prosthesis / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012042:Registries; D012189:Retrospective Studies; D012307:Risk Factors; D012737:Sex Factors; D013997:Time Factors