Partial knee replacements for arthritis are safer than total replacement

People undergoing partial knee replacement surgery, in which only the parts of the knee affected by osteoarthritis are removed, have fewer complications, are less likely to be readmitted to hospital and less likely to die, the researchers found.

However, they are also more likely to have revision surgery – a repeat operation in which the implant has to be replaced.

Professor David Murray led the research at the Nuffield Departmental of Orthopaedics, Rheumatology and Musculoskeletal Sciences (NDORMS) at the University of Oxford. He said: 'For an individual patient, the decision whether to have a partial or total [knee replacement] is based on an assessment of the relative risks and benefits. The main benefit of the partial knee is that it provides better function.

'To put the risks in perspective, if 100 patients had a partial knee rather than a total knee replacement, there would be 1 fewer death and 3 more re-operations in the first four years after surgery.'

This suggests that if the proportion of partial knee replacements carried out was increased from 8% to 20%, the NHS could potentially prevent 170 deaths at the cost of 400 additional revisions.

Revision, re-operation and death were uncommon outcomes of either procedure, the Oxford researchers stressed.

Professor Murray added: 'Joint replacement, by making patients more mobile and fit, tends to save lives overall.'

The Oxford researchers, funded by Arthritis Research UK and the Royal College of Surgeons, used data from the National Joint Registry for England and Wales on the adverse outcomes of more than 100,000 patients who had undergone knee surgery.

If 100 patients had a partial knee rather than a total knee replacement, there would be 1 fewer death and 3 more re-operations in the first four years after surgery

Professor David Murray

Up to half of knees that require replacement, usually because of severe osteoarthritis, can be treated with either partial or total replacements.

Total knee replacement is one of the most common surgical procedures carried out, with over 76,000 performed annually in the UK. Only 5% of patients require revision surgery over a 10-year period.

Because of the higher revision rate of partial knee replacement surgery – which has traditionally been regarded as the most important factor in determining the choice of implant – its use in the treatment of end-stage osteoarthritis is controversial, with only about 7,000 being performed annually in the UK.

The researchers found that although the risk of life-threatening complications from knee replacement surgery is very small, people who undergo total knee replacement are four times more likely to die in the first month after surgery compared to those who have partial knee replacement and 15% more likely to die in the first eight years.

Patients undergoing total replacement are twice as likely to have a blood clot, heart attack or deep infection; three times as likely to have a stroke; and four times as likely to need blood transfusions – compared to those having partial replacement.

Patients who had a partial knee replacement are 40% more likely to have a re-operation, known as revision surgery, during the first eight years after the replacement.

Alex Liddle, an Arthritis Research UK clinical research fellow at Oxford University who ran the study, said: 'Partial and total knee replacements are both successful treatments and a large proportion of patients with end-stage knee osteoarthritis are suitable for either. Both have advantages and disadvantages, and the choice of which procedure to offer will depend on the requirements and expectations of individual patient.'

Medical director of Arthritis Research UK, Professor Alan Silman, said: 'This is a comprehensive study that provides both patients and surgeons with valuable information about the risk and benefits of two effective types of knee replacement operations. This new knowledge will enable them to make an informed decision about which type of surgery is best for particular individuals.

'Even in the elderly with other health problems, knee replacement is a very safe and effective procedure. These data remind us that there are still patients who, fortunately very rarely, can develop life threatening complications following surgery, and we still need to find surgical approaches that take away these risks whilst retaining a successful outcome for patients.'