title: Simultaneous bilateral, staged bilateral, and unilateral total knee arthroplasty. A survival analysis.
abstract: BACKGROUND
  The rates of perioperative morbidity and mortality are areas of concern associated with simultaneous bilateral total knee replacement. The purpose of this paper was to compare the rates of morbidity and mortality and the clinical outcome in large groups of consecutive patients undergoing simultaneous bilateral total knee replacement, unilateral total knee replacement, or staged bilateral total knee replacement.
  
  
  METHODS
  A total of 6200 total knee replacements, performed in 3998 patients between 1983 and 2000, consisted of 2050 simultaneous bilateral, 1796 unilateral, and 152 staged bilateral total knee replacements. A review of each group was conducted to compare the rates of morbidity and mortality, the survival of the prosthesis, and the clinical outcome. Kaplan-Meier survival analyses were performed with failure defined as revision because of aseptic loosening and as patient death. Complications and Knee Society scores were compared throughout the fifteen-year follow-up period (average, 4.3 years of follow-up).
  
  
  RESULTS
  The unilateral group had significantly lower Knee Society scores than the simultaneous bilateral group (p < 0.0001 up to twelve years, and p = 0.0067 at fifteen years) across all postoperative time-intervals. The percentage of patients who had thrombophlebitis was significantly higher in the simultaneous bilateral group (0.9%) than in the unilateral group (0.3%) (p = 0.0326). No significant differences were found with regard to prosthetic failure, cardiac complications, and the rates of death in the three groups. Ten years postoperatively, the simultaneous bilateral group had a significantly higher rate of patient survival than did the unilateral group (78.6% compared with 72.0%) (p = 0.0062).
  
  
  CONCLUSIONS
  The significantly higher rate of thrombophlebitis in the simultaneous bilateral group compared with that in the unilateral group may represent a greater risk to those patients. However, we believe that when there are adequate indications for bilateral total knee replacement, simultaneous bilateral arthroplasty is beneficial to patients, with a minimal increase in the risk of death or other complications compared with that associated with unilateral and staged procedures.
authors.affiliation: The Center for Hip and Knee Surgery, St. Francis Hospital, Mooresville, Indiana 46158, USA.
authors.forename: Merrill A
authors.initials: MA
authors.lastname: Ritter
authors.forename: Leesa D
authors.initials: LD
authors.lastname: Harty
authors.forename: Kenneth E
authors.initials: KE
authors.lastname: Davis
authors.forename: John B
authors.initials: JB
authors.lastname: Meding
authors.forename: Michael
authors.initials: M
authors.lastname: Berend
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D002423:Cause of Death; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D010043:Outcome and Process Assessment, Health Care; D011183:Postoperative Complications / Q000209:etiology* / Q000401:mortality; D016016:Proportional Hazards Models; D011475:Prosthesis Failure; D011655:Pulmonary Embolism / Q000209:etiology / Q000401:mortality; D012086:Reoperation / Q000379:methods; D012189:Retrospective Studies; D018570:Risk Assessment; D015996:Survival Rate; D013924:Thrombophlebitis / Q000209:etiology / Q000401:mortality