title: Long-term clinical outcomes and survivorship of press-fit condylar sigma fixed-bearing and mobile-bearing total knee prostheses in the same patients.
abstract: BACKGROUND
  We are aware of no study that has compared press-fit condylar Sigma fixed-bearing and mobile-bearing total knee prostheses in the same patients after more than ten years of follow-up. The purpose of the current study was to compare these two implants with respect to the functional and radiographic results, prevalence of osteolysis, and overall revision rates at a mean of 12.1 years of follow-up.
  
  
  METHODS
  The study consisted of a consecutive series of 444 patients (mean age [and standard deviation], 66.5 ± 7.4 years) who underwent simultaneous bilateral total knee arthroplasty, with one side treated immediately after the other. All of the patients received a press-fit condylar Sigma mobile-bearing prosthesis on one side and a press-fit condylar Sigma fixed-bearing prosthesis on the contralateral side. The minimum duration of follow-up was ten years (mean, 12.1 years; range, ten to thirteen years). At the time of each follow-up visit, the patients were assessed clinically and radiographically.
  
  
  RESULTS
  Postoperative total knee scores (95 and 94 points), Western Ontario and McMaster Universities Osteoarthritis Index (19 and 18 points), University of California, Los Angeles activity score (both prostheses, 5 points), range of motion (129° ± 6.3° and 127° ± 6.8°), and radiographic findings did not differ significantly between the press-fit condylar Sigma mobile and fixed-bearing designs at the final follow-up. The prevalence of aseptic loosening (1.4% and 1.8%) did not differ significantly between the mobile and fixed-bearing implant designs. No knee in either group had osteolysis. The estimated survival rate with revision as the end point was 98.2% (95% confidence interval, 91% to 99%) and 97.5% (95% confidence interval, 91% to 99%) at 12.1 years for the mobile and fixed-bearing implant groups, respectively.
  
  
  CONCLUSIONS
  The results of the present long-term clinical study suggest that excellent clinical and radiographic results were achieved with both the press-fit condylar Sigma mobile and fixed-bearing cruciate-retaining total knee designs. We found no significant clinical advantage for a mobile-bearing over a fixed-bearing total knee prosthesis.
  
  
  METHODS
  Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Joint Replacement Center, Ewha Womans University School of Medicine, MokDong Hospital, 911-1, MokDong, YangChun-Ku, Seoul, Republic of Korea 158-710. E-mail address for Young-Hoo Kim: younghookim@ewha.ac.kr.
authors.forename: Young-Hoo
authors.initials: YH
authors.lastname: Kim
authors.affiliation: Joint Replacement Center, Ewha Womans University School of Medicine, MokDong Hospital, 911-1, MokDong, YangChun-Ku, Seoul, Republic of Korea 158-710. E-mail address for Young-Hoo Kim: younghookim@ewha.ac.kr.
authors.forename: Jang-Won
authors.initials: JW
authors.lastname: Park
authors.affiliation: Joint Replacement Center, Ewha Womans University School of Medicine, MokDong Hospital, 911-1, MokDong, YangChun-Ku, Seoul, Republic of Korea 158-710. E-mail address for Young-Hoo Kim: younghookim@ewha.ac.kr.
authors.forename: Jun-Shik
authors.initials: JS
authors.lastname: Kim
authors.affiliation: Joint Replacement Center, Ewha Womans University School of Medicine, MokDong Hospital, 911-1, MokDong, YangChun-Ku, Seoul, Republic of Korea 158-710. E-mail address for Young-Hoo Kim: younghookim@ewha.ac.kr.
authors.forename: Sourabh S
authors.initials: SS
authors.lastname: Kulkarni
authors.affiliation: Joint Replacement Center, Ewha Womans University School of Medicine, MokDong Hospital, 911-1, MokDong, YangChun-Ku, Seoul, Republic of Korea 158-710. E-mail address for Young-Hoo Kim: younghookim@ewha.ac.kr.
authors.forename: Yoon-Hong
authors.initials: YH
authors.lastname: Kim
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D011474:Prosthesis Design; D011475:Prosthesis Failure; D016059:Range of Motion, Articular; D012086:Reoperation / Q000706:statistics & numerical data; D016896:Treatment Outcome