title: Age and Preoperative Knee Society Score Are Significant Predictors of Outcomes Among Asians Following Total Knee Arthroplasty.
abstract: BACKGROUND
  The ability to predict patients' functional outcomes will add value to preoperative counseling. The purpose of this study was to evaluate predictors of good outcomes following total knee arthroplasty (TKA) among Asian patients.
  
  
  METHODS
  Registry data from 2006 to 2010 were extracted. The Oxford Knee Score (OKS) and the Short Form (SF)-36 physical component summary (PCS) were used to evaluate outcomes. A "good outcome" was defined as an improvement in scores of greater than or equal to the minimal clinically important difference (MCID) in the primary analysis. The MCID for the OKS was 5, and the MCID for the PCS was 10. For the sensitivity analyses, a "good outcome" was defined as an OKS of <30 and a PCS score of >50. Clinical variables were used to develop a multiple logistic regression model for a good outcome following total knee arthroplasty at 5 years.
  
  
  RESULTS
  Follow-up data were available for 3,062 patients who underwent primary TKA (mean age of 66.4 years; 79.5% female). Eighty-five percent had a good outcome on the basis of the OKS and 83%, on the basis of the SF-36 PCS. Age and preoperative Knee Society score (KSS) were found to be significant predictors. When outcomes were assessed by the MCID, lesser age and lower (worse) preoperative KSS predicted a good outcome at 5 years. When outcomes were assessed by absolute criteria (postoperative scores measured against OKS and PCS thresholds), a higher (better) preoperative KSS predicted a good outcome at 5 years. Body mass index, preoperative flexion range, SF-36 mental component summary (MCS) score, mechanical alignment, sex, education level, ethnicity, operative side, number of comorbidities, type of anesthesia, and type of implant were found not to be significant predictors.
  
  
  CONCLUSIONS
  The majority of Asian patients with osteoarthritis had good outcomes according to the MCID criterion and benefitted from primary TKA. On the basis of our findings, we believe that older patients with a lower (worse) preoperative KSS can be informed that they have a high likelihood of improvement but a lower likelihood of achieving as good a functional outcome as those with better scores.
  
  
  METHODS
  Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Singapore hamidrazak@gmail.com.
authors.forename: Hamid Rahmatullah
authors.initials: HR
authors.lastname: Bin Abd Razak
authors.affiliation: Saw Swee Hock School of Public Health, National University of Singapore, Singapore.
authors.forename: Chuen-Seng
authors.initials: CS
authors.lastname: Tan
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Singapore.
authors.forename: Yongqiang Jerry Delphi
authors.initials: YJ
authors.lastname: Chen
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Singapore.
authors.forename: Hee-Nee
authors.initials: HN
authors.lastname: Pang
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Singapore.
authors.forename: Keng-Jin Darren
authors.initials: KJ
authors.lastname: Tay
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Singapore.
authors.forename: Pak-Lin
authors.initials: PL
authors.lastname: Chin
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Singapore.
authors.forename: Shi-Lu
authors.initials: SL
authors.lastname: Chia
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Singapore.
authors.forename: Ngai-Nung
authors.initials: NN
authors.lastname: Lo
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Singapore.
authors.forename: Seng-Jin
authors.initials: SJ
authors.lastname: Yeo
mesh_terms: D000367:Age Factors; D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D044466:Asian People; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D017060:Patient Satisfaction; D011184:Postoperative Period; D011237:Predictive Value of Tests; D016059:Range of Motion, Articular / Q000502:physiology; D012720:Severity of Illness Index; D012846:Singapore; D016896:Treatment Outcome