A new study has been able to estimate, for the first time, how long hip and knee replacements are likely to last.

At least 4,500 hip replacements are carried out in Ireland every year, along with over 1,500 knee replacements.

"Patients often ask clinicians how long their hip or knee replacement will last, but until now, we have not had a generalisable answer. At best, we have only been able to say how long replacements are designed to last, rather than referring to actual evidence from multiple patients' experiences of joint replacement surgery," noted the study's lead author, Dr Jonathan Evans, of the University of Bristol.

The study involved a review of thousands of case studies that took place over a 25-year period in six countries, including Denmark, Finland and Australia. It found that eight out of 10 total knee replacements and six out of 10 total hip replacements are still in place after 25 years.

"Given the improvement in technology and techniques in the last 25 years, we expect that hip or knee replacements put in today may last even longer," Dr Evans pointed out.

He explained that while hip and knee replacements are common and effective types of surgery, they will eventually fail due to issues such as normal wear and tear, fracture and infection. In many of these cases, patients require revision surgery, which is more likely to fail and is more expensive than the original surgery.

Therefore, knowing how long a replacement is likely to last is important for patients and their surgeons, and is especially relevant given the fact that people are now living longer.

When it came to total hip replacements, the study looked at over 215,000 people whose cases were followed up for 15 years after their surgery, over 74,000 who were followed up for 20 years and more than 51,000 who were followed up for 25 years.

Overall, 89% of the total hip replacements were found to last 15 years, 70% lasted 20 years and 58% lasted 25 years.

When it came to total knee replacements, the study looked at over 299,000 people who were followed up for 15 years, over 88,000 who were followed up for 20 years and more than 76,000 who were followed up for 25 years.

Overall, 93% of the total knee replacements were found to last 15 years, 90% lasted 20 years, while 82% lasted 25 years.

The study also looked at partial knee replacements and found that 77% lasted 15 years, 72% lasted 20 years and 70% lasted 25 years.

The researchers noted that these findings gives doctors the information they need to give their patients ‘a reliable and evidence-based answer to one of the questions they consider most important when deciding whether it is the right time for them to have a joint replacement'.

Details of these findings are published in the journal, The Lancet.