title: Increased long-term survival of posterior cruciate-retaining versus posterior cruciate-stabilizing total knee replacements.
abstract: BACKGROUND
  Considerable debate remains regarding the use of posterior cruciate-retaining or posterior cruciate-stabilizing designs for total knee arthroplasty. Multiple studies have investigated kinematic, radiographic, and clinical outcomes of both. Nevertheless, long-term survivorship analyses directly comparing the two designs have not been performed, to our knowledge. Our goal was to analyze the fifteen-year survival of posterior cruciate-retaining and posterior cruciate-stabilizing total knee replacements at our institution.
  
  
  METHODS
  A retrospective review identified 8117 total knee arthroplasties (5389 posterior cruciate-retaining and 2728 posterior cruciate-stabilizing) that had been performed from 1988 to 1998. This range was chosen because both designs were used in high volumes at our institution during this period. Patients were followed via our total joint registry at one, two, and five years after the arthroplasty and every five years thereafter. Aseptic revision surgery was the primary end point of our analysis. Implant survival was estimated with Kaplan-Meier curves.
  
  
  RESULTS
  Survival at fifteen years was 90% for posterior cruciate-retaining total knee replacements, compared with 77% for posterior cruciate-stabilizing total knee replacements (p < 0.001). In knees with preoperative deformity, the fifteen-year survival was 90% for posterior cruciate-retaining total knee replacements, compared with 75% for posterior cruciate-stabilizing total knee replacements (p < 0.04). Likewise, in knees without preoperative deformity, the fifteen-year survival was 88% for posterior cruciate-retaining total knee replacements, compared with 78% for posterior cruciate-stabilizing total knee replacements (p < 0.001). After adjustment for age, sex, preoperative diagnosis, and preoperative deformity, the risk of revision was significantly lower in knees with a posterior cruciate-retaining total knee replacement (p < 0.001; hazard ratio = 0.5; 95% confidence interval, 0.4 to 0.6).
  
  
  CONCLUSIONS
  In evaluating the implants used at our institution for total knee arthroplasty during the study period, posterior cruciate-retaining prostheses had significantly improved survival in comparison with posterior cruciate-stabilizing prostheses at fifteen years. Furthermore, this significant difference remained when accounting for age, sex, diagnosis, and deformity.
authors.affiliation: Department of Orthopedic, Mayo Clinic, 200 First Street S.W., Rochester, MN 55905, USA.
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Abdel
authors.forename: Mark E
authors.initials: ME
authors.lastname: Morrey
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Jensen
authors.forename: Bernard F
authors.initials: BF
authors.lastname: Morrey
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016118:Anterior Cruciate Ligament; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000379:methods*; D015331:Cohort Studies; D016001:Confidence Intervals; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D053208:Kaplan-Meier Estimate; D007720:Knee Prosthesis; D008297:Male; D016119:Posterior Cruciate Ligament; D016016:Proportional Hazards Models; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012189:Retrospective Studies; D018570:Risk Assessment; D013997:Time Factors; D016896:Treatment Outcome