For decades, patients have been told that an artificial hip will need to be replaced again and again. A large international study now points to a shift in how hip replacement surgery should be understood: if you have an artificial hip fitted today, you can often expect it to last a lifetime. A professor says that this is an important message that could influence how patients and doctors plan both the operation and what follows.
There was a time when doctors routinely told patients facing hip surgery that they should expect a replacement after around 10 years.
Today, the picture is different. Overall figures in Denmark show that 80–85% of patients still have their original artificial hip after 20 years – across patient groups and types of hip. This is far more than previously expected, and many do not need another operation. In addition, it suggests that the understanding of how long a hip can last is changing.
Now, a new study finds a real turning point: the latest types of artificial hips included in the study can last a lifetime for most people. This changes how hip surgery is planned – and whether patients expect to need another operation at all.
“This is very good news that doctors can share with patients facing hip replacement surgery. Most people want to know when to expect another operation, and now we can tell them that they probably won’t,” says a researcher behind the study, Claus Varnum, Professor and Senior Consultant from the Department of Orthopaedic Surgery at Vejle Hospital, Denmark.
The research has been published in The Lancet.
From parts that wear out to lifelong solutions
The explanation lies in developments in the materials used for both the ball and the socket, which today make artificial hips far more resistant to wear. The joint surfaces wear down more slowly as they move against each other. As a result, hip replacements in many cases no longer function as temporary solutions – depending on the patient and level of activity – but as implants that may last for the rest of a person’s life.
Today, a metal head is typically used in combination with a wear layer of highly cross-linked polyethylene – a type of plastic engineered to be especially resistant to wear.
In Denmark, around 14,000 people receive such an artificial hip each year, and worldwide the number runs into more than a million.
“With this study, we did not just want to see how long artificial hips last in general but how this particular type – one of the most modern types of artificial hip – holds up. This gives patients the best indication of what they can expect,” explains Claus Varnum.
Claus Varnum chairs the steering committee behind the Danish Hip Arthroplasty Register. The registry shows that 80–85% of all artificial hips are still functioning after 20 years – meaning that they have not been replaced.
However, these figures cover all age groups and types of hip replacement and cannot therefore be directly compared with the most modern implants alone. This is precisely why the new study supplements the data with figures specifically for the latest types.
Data from nearly 2 million hips confirm the shift
To test whether this revised understanding holds, the researchers compiled data from 29 clinical studies and eight national registries in which patients were followed over time – and thus across both controlled studies and real-world patient pathways.
The study included 1,904,237 artificial hips of this type. In some cases, patients have been followed for up to 20 years.
The results are striking: after 20 years, 93.6% of the hips are still functioning – that is, without having been replaced. For many, this means that the need for a new operation never arises – in line with what the registry data also suggest.
When the researchers extrapolate beyond the periods they have directly measured, the models indicate that 92.8% are still functioning after 25 years and 92.1% after 30 years. This time frame covers the rest of many people’s lives – even if they undergo surgery relatively early in life.
“That is a surprisingly high figure. We knew that the new types of artificial hips last longer, but these figures show that for many people, the hip is likely to last a lifetime – and this is a game-changer,” says Claus Varnum.
From repeated operations to a one-time treatment
Although the results are based on extrapolations up to 30 years, and there is therefore some uncertainty about the longest time perspectives, Claus Varnum says that there is no indication that the hips will then begin to fail in large numbers.
However, this cannot yet be known with certainty because 30 years of real-world follow-up data do not yet exist.
“30 years is a very long time, and it increases the likelihood that you will never need to have an artificial hip replaced. We are certainly reaching a point where, in many cases, you can count on the hip lasting the whole time."
"This also applies to those who have it fitted at a younger age. This is positive news that we must pass on to our patients,” says Claus Varnum.
