HEALTH STATE UTILITIES IN KNEE REPLACEMENT SURGERY - THE DEVELOPMENT AND EVALUATION OF MCKNEE

Objective, 1. To develop McKnee, a classification system and direct ut ility 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 se lf-health utility one week before and 3 mo after surgery; (iv) evaluat e the stability of 3 clinical marker health states describing mild, mo derate, and severe knee disability; (v) compare self-health utility sc ores with the Short Form 36 (SF-36). Methods, 1. Instrument developmen t: The McKnee modified Health Utilities Index was developed and used t o 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 of 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: M cKnee 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 (m ean, 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 t ransition 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 intracl ass correlation coefficients for individual scores were low. Conclusio n, McKnee provides a preference based measure of health related qualit y of life that can be used to obtain and interpret clinically the knee disability utility scores 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 st ates and obtaining direct measurements of utility scores for selected health states.