A team of Bristol-based researchers are to investigate the safety of an increasingly commonly-used type of hip replacement surgery performed on younger people.

Metal-on-metal (MoM) hip resurfacing is a less invasive alternative to total hip replacement surgery for younger, more active people, and accounts for between five and ten percent of the 40,000-plus hip replacement operations carried out in the UK each year.

However, little is known about the biological effects of the MoM devices, and there is a theoretical risk of contamination of the body through absorption of metals from the implant.

Now a team led by Dr Patrick Case and Professor Ian Learmonth at the University of Bristol’s Department of Orthopaedic Surgery, in collaboration with colleagues in Leeds,  aim to investigate the amount of metal released from the MoM implants and any effect on chromosomes that it may cause to patients. Their three-year £226, 266 study will be funded by medical research charity the Arthritis Research Campaign (arc).

The team will recruit 80 patients from the Bristol area who are about to undergo hip resurfacing surgery and follow their progress over the next two years. Blood and urine samples will be taken before surgery then six months, one year and two years later. The team will investigate whether there are any differences in metal levels and chromosome changes between two different types of commercially available resurfacing implants.

“MOM resurfacing has been introduced as a new and potentially improved method of joint replacement for patients with arthritis, and is being increasingly used for young patients who will be exposed to the metals in the replacement for up to 60 years,” explained Professor Learmonth.

“Although the potential risks remain theoretical, and no patients have developed any problems, the biological effects of this procedure are not known. It’s very important that we find out about any chromosomal changes and document them in the most accurate manner.”

Currently patients awaiting hip replacement are told about the theoretical risks of the MoM as far as they are known, and also its benefits. But it is accepted by the orthopaedic community that knowledge about the long-term affects of MoM is insufficient.

As well as the arc-funded study, Professor Learmonth, in collaboration with the British Orthopaedic Association (BOA) is also planning to hold a major international conference in Bristol in the autumn to address the issue. The BOA has also obtained funding for a scientist to spend a year reviewing current knowledge of MoM with a view to producing guidelines for surgeons to enable them to provide informed consent for their patients.