Epidemiology and economic evaluations relating to knee and hip replacement with evidence from routinely collected data

Knee and hip replacement have been shown, in general, to be both effective and cost-effective when compared with non-surgical alternatives. There has been, however, uncertainty around individuals’ risks of undergoing the procedures after diagnoses of osteoarthritis or rheumatoid arthritis, and patient outcomes after surgery. The first set of research questions answered in this thesis aimed to address the gaps in the evidence-base on patient prognosis under current practice. Routinely collected data from England and Catalonia, Spain, informed these analyses. In the research undertaken it was found that after a diagnosis of knee osteoarthritis, the lifetime risk of knee replacement was 30% for the average patient profile. Meanwhile, lifetime risk of hip replacement after a diagnosis of hip osteoarthritis was 14%, and lifetime risks of knee and hip replacement following a diagnosis of rheumatoid arthritis were 22% and 17%, respectively. It was also found that patients, on average, achieved more than 62% of their potential improvement in joint-specific outcomes after knee replacement, and more than 81% after hip replacement. Risks of post-operative complications were typically less than 1%, while lifetime risk of revision was 5% and 8% after knee and hip replacement for the average patient profile, respectively.
The second set of research questions which were addressed focused on the potential consequences of interventions which either reduce the risks of or improve outcomes after knee and hip replacement. Addressing these questions first required an understanding of outcomes under current practice, and this was provided by the preceding research. The effectiveness of tumour necrosis factor inhibitors on long-term risks of knee and hip replacement is not yet established, but if their use as a first-line therapy led to relative risk reductions of 20%, for example, 46 and 30 knee and hip replacements would be avoided per 1,000 individuals. This would also result in a combined procedure cost saving of over £300,000 for a cohort of that size. Meanwhile, one knee replacement is expected to be avoided for every 17 bariatric surgeries provided shortly after a diagnosis of knee osteoarthritis for individuals with a BMI of 40 (but otherwise average characteristics). Threshold prices, prices at which the net health benefits from funding the intervention would be zero, were estimated for computer or robot-assisted knee and hip replacement. Threshold prices for a 50% relative reduction in risk of revision were around £1,000, while they were approximately £10,000 for a 5% relative improvement in post-operative quality of life if unrevised.
These findings provide evidence to patients on their prognosis under current practice and will help to inform resource allocation decisions on interventions related to knee and hip replacement. Moreover, the research presented in this thesis also demonstrates the value of routinely collected data for considering the life course of a disease and its treatment.

Advisor: Pinedo Villanueva, R
Prieto Alhambra, D