A new knee or hip has a life of three years

Research from the UK has found that hip and knee replacements in general last for around three years.

The research on the new surgical techniques of hip resurfacing and unicondylar knee replacement, has revealed that in 75% of patients their joint replacement needs revising after a period of three years.

Although this compares favourably with the rest of the world, the study reinforces concerns about these new surgical techniques.

The researchers from the Royal College of Surgeons examined records from the National Joint Registry (NJR) for England and Wales which is the largest national joint registry of any in the world, in order to establish the outcomes of such new surgical techniques in comparison to the many other types of surgical techniques and prostheses used to replace joints.

Hip and knee replacements are amongst the most frequent surgical operations performed and around 160,000 were carried out in England and Wales in 2006.

Since 2003 the NJR has collected comprehensive data available immediately following surgery, including patient characteristics, the type of prostheses and the surgical technique used to replace the joint, with the aim of providing evidence with which to assess these prostheses and techniques.

In order to identify how often the hip or knee replacement had to be re-done, Dr. Jan van der Meulen and colleagues linked the NJR records with another database, the Hospital Episodes Statistics (HES), which contains information on all admissions to National Health Service (NHS) hospitals in England.

They included revisions for any reason in the three years following a hip or knee replacement but also paid particular attention to hip resurfacing and unicondylar knee replacement, two techniques that are increasingly used but about which there is little evidence of their performance.

Hip resurfacing was introduced in the 1990s for younger patients or those with less severe disease, which instead of replacing the head of the femur, as happens in total hip replacement, the diseased surface of the joint is replaced with a metal component.

In unicondylar knee replacement only the damaged part of the knee is replaced and it also results in shorter recovery time.

The researchers found that of the 167,076 procedures that could be linked between the two databases between April 2003 and September 2006 - about half of all such operations carried out required a revision of their joint replacement, which is considered to be low.

As expected the patients who had cemented prostheses - cement being used to position the metal implant in place in the original replacement surgery - had the lowest revision rates.

For hip replacements the highest revision rates were experienced by women who had undergone hip resurfacing rather than total joint replacement and of patients who had undergone knee replacement operations, those who had unicondylar prostheses had the highest revision rates.

The researchers say there appeared to be no connection between a patient's age and revision rates for hip replacements, whereas revision rates after knee replacement decreased strongly with age.

They say the study demonstrates what can be achieved by linking together databases and on the basis of the data, the researchers suggest that "consideration should be given to using hip resurfacing only in male patients and unicondylar knee replacement only in elderly patients."

The study is published in the current issue of PLoS Medicine.