title: High-flexion prosthesis improves function of TKA in Asian patients without decreasing early survivorship.
abstract: BACKGROUND
  Two previous studies recently raised the possibility of a high risk of early femoral components loosening with high-flexion (HF) prostheses in Asian populations and suggested that the high failure rate of HF TKAs was associated with HF ability. However, these findings are controversial given other studies reporting a low incidence of aseptic failures in HF prostheses.
  
  
  OBJECTIVE
  We therefore determined (1) the rate of achieving postoperative HF after HF TKA; (2) whether the aseptic loosening rate of HF prostheses is high; and (3) whether the survivorship was worsened in patients who achieved postoperative deep knee flexion in our cohort of Korean patients.
  
  
  METHODS
  We retrospectively reviewed 488 patients who had 698 primary TKAs using the NexGen(®) Legacy Posterior-Stabilized Flex system implanted from 2003 to 2010. There were 40 men and 448 women with a mean age of 68 years. We obtained Hospital for Special Surgery scores, maximal flexion, and radiographs. The minimum followup for functional and radiographic evaluations was 2 years (median, 4.8 years; range, 2-8.7 years). We performed a survival analysis on all patients for aseptic loosening.
  
  
  RESULTS
  Three hundred sixty knees (52%) could achieve ≥ 135° maximum flexion. Six of the 698 knees (0.9%) developed aseptic loosening (three femoral and three tibial). The survival at 5 years for aseptic loosening was 99.1%. The overall survival for aseptic failure did not differ between knees that achieved HF and those that did not.
  
  
  CONCLUSIONS
  We observed a low incidence of early aseptic loosening of HF designs in this series. Our findings suggest HF TKAs have high survival in Asian patients at 5 years although half of the patients attained maximum flexion more than 135° postoperatively.
authors.affiliation: Department of Orthopedic Surgery, College of Medicine, Catholic University, Incheon St Mary's Hospital, Bupyeong-gu, Incheon, Korea.
authors.forename: Bum-Sik
authors.initials: BS
authors.lastname: Lee
authors.forename: Jong-Won
authors.initials: JW
authors.lastname: Chung
authors.forename: Jong-Min
authors.initials: JM
authors.lastname: Kim
authors.forename: Kyung-Ah
authors.initials: KA
authors.lastname: Kim
authors.forename: Seong-Il
authors.initials: SI
authors.lastname: Bin
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000295:instrumentation*; D044466:Asian People; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011859:Radiography; D016059:Range of Motion, Articular; D020127:Recovery of Function; D056910:Republic of Korea / Q000453:epidemiology; D012189:Retrospective Studies; D013997:Time Factors; D016896:Treatment Outcome