“The aim remains – we want knee and hip replacements to last a patient their entire life.”

23 April 2019
A researcher looking down a microscope.

Hip and knee replacements are two of the most common forms of surgery and for that reason it’s a topic that frequently makes the news.

"Eight out of 10 knee replacements and six out of 10 hip replacements last as long as 25 years, says a large study from the University of Bristol." - BBC News

We spoke to Dr Jonathan Evans orthopaedic registrar, lead study author and research fellow at Bristol Medical School to find out more about this study, and why it’s so important to help people make informed decisions about their surgery.

Dr Jonathan Evans

Dr Jonathan Evans, orthopaedic registrar, lead study author and research fellow at Bristol Medical School

What was the motivation behind this study?

We decided to do two research studies as we were regularly being asked by patients in clinic about how long a knee or hip replacement would last if they decided to have one.

Whilst we could tell them typical percentages for 10 years, there was not good easily accessible data available for longer than this. The fact that we were asked the question so frequently made us realise how important this is to patients and that this information was not readily available to them.

We wanted to put ourselves in the position of a patient. But one that has access to the full university databases and skills to get a good answer to the questions on how long hip and knee replacements last.

There are lots of things that can make it complicated like the fact there are so many different types of hip and knee replacements on the market.

A knee or hip replacement is similar to a car, in that there are lots of different types and they all do slightly different things and work in slightly different ways to get you from a to b.

The other thing to say about ‘why now/why hasn’t it been done before’ is simply the fact that you need to wait a long time to find out the outcomes of a replacement.

The biggest databases that have been collecting data about replacements started in the 1970s in Sweden and elsewhere in Scandinavia. So, it’s taken until now to get the long-term data to put us in a position where we can reliably answer these questions.

We wanted to analyse all this detail and be able to give a really simple answer.

How do you monitor joint replacements?

As part of the National Joint Registry, what we do here in Bristol is monitor the performance of all joint replacements put in in England and Wales (and in Northern Ireland and the Isle of Man).

This is to make sure that no individual type of hip or knee replacement is performing statistically worse. If we think one is performing badly and might be unsafe for a patient, then it’s our job here to flag that so a decision can be made about whether it should continue being used.

Whilst I can’t say at the moment which ones are better. What we can say is that we work every day to make sure that if any of the hip or knee replacements are performing particularly badly, then we are noticing this and someone can stop them going in.

We've heard from many people who say they have been turned down replacement surgery because they are too young. Will this news make a difference to them? 

The decision of when to have a hip or knee replacement very much comes down to a joint decision between the patient and the surgeon. The patient should be making that decision based on information given by the surgeon and as many other trustworthy sources (such as Versus Arthritis) as possible.

It’s about trying to encourage patients to understand the risks associated with joint replacement surgery and help them make an informed decision. It’s not just about how long the majority of hip and knee replacements last, it’s looking at how long it will last in that patient. 

Although it’s great news that these replacements do last a lot longer than we thought, every patient needs to consider what it means for them, because it’s a life changing operation.

We’re incredibly fortunate as a group of surgeons to be able to do these operations and be able to turn around people’s lives. But we need to make sure we’re only doing it in people at the right time. You don’t want to jump in and do it too early when the patient might not be getting the most from the operation relative to the risks.

Do continued improvements in technology mean that replacement joints are likely to last even longer?

The ultimate aim still remains and will always remain, that we want hip and knee replacements to last as long as patient wants them to last.

Famously, Prof Sir John Charnley who invented modern hip replacement in 1960s, wrote in The Lancet that we cannot expect a hip replacement to last more than 30 years, but we’ve already shown this is not true and people are often seeing this.

There are things being developed that we think will make a difference. We want knee and hip replacements to last a patient their entire life. I don’t think you’ll see any hip or knee surgeons trying to stop achieving that aim until we’re there.

Is there a specific message you'd like to share about joint replacement surgery?

As an individual, I’m very keen for patients to understand as much as they can about their hip or knee replacement. This includes how long we think they’ll last as well as being aware of differences in technology.

There are lots of different types and I’d like patients to know this and engage with their surgeons and ask questions about why they are picking a certain type for them, and how well this one performed compared to others.

It’s important that patients feel in charge of their operation, very often they may feel swept up in processes from GPs to an operation. I try to tell my patients to take a step back, this is your operation, you’re in charge, so please ask any questions.

I would say to patients, we exist because of them and trying to make their lives better, so they should always feel like they can challenge and ask for more information. We want you to understand and feel happy.

Our clinical spokesperson and orthopaedic surgeon, Professor Mark Wilkinson has commented on the study and says:

"Not all people with arthritis will need surgery, however many people do end up having joint replacements. We know that arthritis can affect people of all ages and young people can also end up having surgery.

For many people, joint replacement can be life changing and help them to regain their independence. It’s important to know as much as we can about the benefits and downsides to joint replacements.

Research like this will help people with arthritis to have a more informed conversation with their surgeons to make sure they are choosing the treatment option that is right for them.”

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