VARIATIONS IN KNEE REPLACEMENT UTILIZATION RATES AND THE SUPPLY OF HEALTH-PROFESSIONALS IN ONTARIO, CANADA

Objective. To measure regional variations in knee replacement (KR) uti lization rates across the 49 counties of Ontario, Canada, since April 1, 1984, and to evaluate its relationship with the supply of health pr ofessionals. Methods, Utilization data were acquired from the Canadian Institute for Health Information, and physician data were. acquired f rom the Ontario Ministry of Health. There were 18,530 hospitalizations for KR in Ontario between April 1, 1984 and March 31, 1991, Utilizati on rates were defined as the number of KR procedures for all residents of each county (irrespective of where these procedures were performed ) divided by the resident population. Direct methods were used to stan dardize utilization for age and sex. The extremal quotient, the weight ed coefficient of variation, and the systematic coefficient of variati on were used as measures of variation. Results. Between fiscal years 1 984 and 1990, the extremal quotient fell from 8.1 to 3.4, the weighted coefficient of variation fell from 0.430 to 0.315, and the systematic coefficient of variation fell from 0.215 to 0.142. Utilization was gr eater in southwestern Ontario (p < 0.001) and lower in Toronto and Dur ham (p < 0.001) than elsewhere. Utilization in remote areas was not di fferent from that for the province as a whole (p < 0.001). The correla tion coefficient between standardized KR utilization and the density o f orthopedic surgeons was not significant (p = 0.26) at -0.16, but tho se for rheumatologists (r = -0.25, p = 0.08) and physical medicine spe cialists (r = -0.42, p = 0.002) were significant. Conclusion. Regional variation in KR surgery has fallen since fiscal year 1984 from ''very high'' variability to ''moderate'' variability. KR utilization was sh own to be negatively, but not significantly, related to orthopedic sur geon density. Therefore, proposals to modify surgeons' fees or to infl uence their practice locations may equalize the supply of surgeons, bu t are unlikely to affect the pattern of KR utilization.