Population requirement for primary hip-replacement surgery: a cross-sectional study

Summary

Background

There has been a long-standing failure in many countries to satisfy the demand for several elective surgical treatments, including total hip replacement. We set out to estimate the population requirement for primary total hip replacement in England.

Methods

We undertook a cross-sectional study of a stratified random sample of 28 080 individuals aged 35 and over from 40 general practices in inner-city, urban, and rural areas of Avon and Somerset, UK. Prevalent disease was identified through a two-stage process: a self-report screening questionnaire (22 978 of 26 046 responded) and subsequent clinical examination, incident disease was estimated from the point prevalence by statistical modelling. The requirement for total hip replacement surgery was estimated on the basis of pain and loss of functional ability, with adjustment for evidence of comorbidity and patients' treatment preferences.

Findings

3169 people reported hip pain on the screening questionnaire. 2018 were invited for clinical examination, and 1405 attended. The prevalence of self-reported hip pain was 107 per 1000 (95% Cl 101–113) for men and 173 per 1000 (166–180) for women. The prevalence of hip disease severe enough to require surgery was 15·2 (12·7–17·8) per 1000 aged 35–85 years. The corresponding annual incidence of hip disease requiring surgery was estimated as 2·23 (1·56–2·90), which suggests an overall requirement in England of 46 600 operations per year for patients who expressed a preference for, and were suitable for, surgery; the recent actual provision in England was about 43 500.

Interpretation

This research suggests that the satisfaction of demand for total hip replacement, given agreed criteria for surgery, is a realistic objective.

Introduction

Health-care rationing, in terms of both its justification and mechanisms, is one of the most important issues facing all health-care systems.¹ However, the rationing debate² is being conducted largely in the absence of data. The relevant literature mainly consists of assertion, political analysis, ethical discussion, and the exploration of economic principles. What is notable for its absence is the epidemiological basis for the underlying assumption that demand for effective treatments will invariably exceed supply. Waiting-list figures suggest that health services are apparently not satisfying demand³ in particular areas, but this conclusion does not mean that demand is generally insatiable.

The study reported here was an attempt to introduce some precision into this debate. We asked two epidemiological questions. What is the population distribution of the capacity to benefit from particular interventions? How does the incidence of remediable morbidity compare with the provision of treatment? Since there is no strong tradition of asking these questions, and of translating them into epidemiologically measurable variables, we should first justify our approach.

Health-care needs can be defined in terms of the individual's capacity to benefit from treatment.⁴ Within this broad range of need, the problem is to define the amount of particular treatments that should be provided to bring the greatest benefit. The term “health-care requirements” is preferred to denote this more specific definition.⁵ Heath-care requirements represent defined components of health-care needs that the population can expect to be satisfied. Health-care requirements must reflect three main attributes: the distribution in the population of those for whom treatment is indicated and desired; the effectiveness of the treatment for specific categories of disease; and some justification in terms of benefits per unit cost in relation to competing services. This area of health-services research can be described as the epidemiology of indications.⁶

We present empirical data on the population distribution of indications for primary total replacement of the hip. This intervention was chosen for study because it is one of the disorders with the longest waiting lists. The failure to dispose of waiting lists for this and other types of elective surgery was the main stimulus for a major National Health Service (NHS) reorganisation,⁷ and this continuing failure remains as a bulwark to conventional assumptions about rationing.⁸

Total hip replacement is one of the commonest elective surgical procedures; around 43 500 primary operations are done each year in English NHS and independent hospitals. There are some concerns about effectiveness, particularly with respect to prostheses that have not been fully evaluated and to the proper indications for treatment, but this procedure is generally regarded as unquestionably cost-effective.⁹

Potential demand can be estimated from data on use of health services, but this is clearly a circular process. Epidemiological studies of the distribution of radiological osteoarthritis of the hip have shown that prevalence increases with age, with 5% or more of the population older than 65 years showing evidence of severe change on radiography.¹⁰ Population requirements for surgery cannot be estimated from such findings, since the relation between radiographic change, symptoms, and function is uncertain. The only estimate of the numbers of individuals who might benefit from total hip replacement based on clinical examination¹¹ is now an unhelpful index of potential demand, since indications for surgery and views of anaesthetic risk have changed in the 20 years since that research was done. We therefore decided to investigate the health-care requirements for total hip replacement by the conventional epidemiological method of examining the distribution of the variables of interest by questionnaire and clinical examination in a population-based probability sample.