Urban-rural differences in total hip replacements: the next stage.

Background: The aim of this study was to explore the differences in the incidence of primary elective total hip replacements between urban and rural communities and different age and sex groups in Northern Ireland, and to use this information to develop an equitable method for the allocation of surgical capacity among groups of general practices, in a system where referrals are matched to the contracted capacity.
Methods: A retrospective review was performed of all cases of primary elective total hip replacement between 1 April 1994 and 31 March 1997. Incidence rates were calculated using direct standardization. Age, sex, and urban and rural specific rates for Northern Ireland were calculated and applied to each general practice population giving that practice's annual expected number of total hip replacements.
Results: A total of 4,147 cases were analysed. The age and sex standardized incidence of primary elective total hip replacement for the total population was 87.6 per 100,000. The incidence was significantly greater in rural populations (101.3 per 100,000), than in urban ones (77.6 per 100,000), p < 0.001. The overall standardized ratio of males to females was 1:1 although it was 1:1.2 in urban and 1:0.9 in rural populations. Using a 3 year commissioning cycle, commissioning for a population of 130,000 allows a 10 per cent margin of error in the numbers of procedures required.
Conclusions: A system of calculating the expected need for a total hip replacements was developed based on the demography and rurality of individual general practices. This system allowed a method of commissioning to be instituted that could significantly reduce in-patient waiting lists for this procedure.