title: Health state utilities in knee replacement surgery: the development and evaluation of McKnee.
abstract: OBJECTIVE
  1. To develop McKnee, a classification system and direct utility measure for health states associated with knee replacement (KR) surgery. 2. To apply McKnee in a before-after study of KR surgery to: (i) gain experience with McKnee in an elderly population; (ii) confirm the practicality and usefulness of the McKnee system; (iii) assess self-health utility one week before and 3 mo after surgery; (iv) evaluate the stability of 3 clinical marker health states describing mild, moderate, and severe knee disability; (v) compare self-health utility scores with Short Form 36 (SF-36).
  
  
  METHODS
  1. Instrument development: The McKnee modified Health Utilities Index was developed and used to describe self-health and clinical marker health states: the clinical validity of the clinical marker states was evaluated by 5 clinicians involved in the care off KR patients. 2. Instrument evaluation: McKnee and the SF-36 were administered to 48 patients with osteoarthritis one week before and 3 mo after KR surgery.
  
  
  RESULTS
  Before-after study: McKnee was feasible and acceptable in the older patient group studied (mean age in years, SD: 69.9, 8.6). No change in self-health utility (mean, SD) was observed at 3 mo postsurgery: before -0.78, 0.17; after -0.78, 0.21. On the SF-36, only the change scores for pain and health transition were statistically significant. Utilities (mean, SD) for the clinical marker health states were: mild -0.80, 0.20; moderate -0.55, 0.28; and severe -0.48, 0.31. The clinical marker mean utility scores were stable between the baseline and 3 mo assessment, but the intraclass correlation coefficients for individual scores were low.
  
  
  CONCLUSIONS
  McKnee provides a preference based measure of health related quality of life that can be used to obtain and interpret clinically the knee disability utility scorers needed for cost-utility studies and medical decision-making models about KR surgery. The McKnee system provides a practical and useful method for classifying knee disability health states and obtaining direct measurements of utility scores for selected health states.
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, School of Business, McMaster University, Hamilton, Canada.
authors.forename: K J
authors.initials: KJ
authors.lastname: Bennett
authors.forename: G W
authors.initials: GW
authors.lastname: Torrance
authors.forename: L A
authors.initials: LA
authors.lastname: Moran
authors.forename: F
authors.initials: F
authors.lastname: Smith
authors.forename: C H
authors.initials: CH
authors.lastname: Goldsmith
mesh_terms: D000368:Aged; D003362:Cost-Benefit Analysis / Q000379:methods; D004185:Disability Evaluation; D005069:Evaluation Studies as Topic; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D007719:Knee Joint / Q000473:pathology / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000175:diagnosis / Q000191:economics / Q000601:surgery*; D011788:Quality of Life