The past, present and future of total hip and knee arthroplasty in the UK : a population-based statistical analysis

The total replacement of the hip and knee joint has become one of the most successful surgical procedures of the late 20th century, yet in the United Kingdom little attention has been given to describing trends and exploring risk factors at a population level, with even less consideration given to future levels of activity. This thesis has used nationally representative primary care data from the Clinical Practice Research Datalink to describe past trends, estimate the lifetime risk, explore risk factors and project future levels of total hip and knee replacement for the UK as a whole. The data comprised over 100,000 surgical procedures spanning a twenty year period, and was accompanied by demographic and clinical details for patients undergoing these procedures. Temporal trends for hip and knee replacement between 1991 and 2006 were described by age and gender, and incidence rates were found to have increased considerably over the period. The lifetime risk of hip and knee replacement was estimated at between 5 and 10 percent for a 50-year old in the United Kingdom, which is much less than the lifetime risk of osteoarthritis, the disease for which the vast majority of these operations are performed. The time to failure of primary hip and knee replacements was found to have a small but significant association with body mass index. Finally, projections of the future rate of these replacement operations were presented, suggesting that changes in the distribution of body mass index in the UK may increase future levels of knee replacement more than hip replacement. This thesis has presented and discussed four published articles which build upon each other to add to the descriptive epidemiological literature on the past trends, current risks and future needs of hip and knee replacement in the UK. Over the coming decades, it is important that researchers continue to analyse population-level data on hip and knee replacement in order to report on changes in risk factors, to monitor changes in the characteristics of those undergoing joint surgery and to inform policymakers and healthcare providers.