Hip replacement
More than 50,000 hip replacements are carried out in Britain every year, and over 70,000 knee replacement operations happen each year in England and Wales. These are among the most successful operations done in the UK, and can make a huge difference to the individuals concerned, giving them more mobility and independence, a reduction or end to joint pain and a better life.
However, orthopaedic specialists have been debating for some time whether a person’s weight affects the success of a hip or knee replacement (also known as arthroplasty). Now new data presented at the European Federation of National Associations of Orthopaedics and Traumatology (EFORT) in Copenhagen provides compelling evidence that it can indeed make a big difference.
The data showed that obese patients are more than three times as likely to develop an infection. (People with a Body Mass Index (BMI) of more than 30 are classed as obese.) They are also one and a half times more likely to develop a loosening of the replacement joint, and are at twice as much risk of thromboembolism (a blood clot in a vein, often in the legs or lungs). The greater the BMI the greater the risk.
"Weight is a very serious issue in terms of joint replacement," said Peter Kay, President of the British Orthopaedic Association, and Consultant Hip and Knee Surgeon, Wrightington Hospital, Lancashire. "If you are heavier throughout your life you’re more likely to end up needing a joint replacement, there’s very good evidence for this. And people who are considerably overweight before surgery, don’t tend to do as well after surgery, both in terms of a risk of getting a complication, such as an infection or blood clot, or another medical problem, such as chest or heart-related problems."
The researchers got their data from a variety of sources, one of them being a meta-study of the complication rates for total hip arthroplasty. This combined the results of 15 different studies – making up almost 10,000 case histories altogether. "The complications dramatically increased among the obese and were not of a negligible nature," said Dr Daniel Haverkamp from the Academic Medical Centre in Amsterdam, a leading author of the meta-study.” He went on to explain that infections or loosening of the joint would mean that the patient would have to undergo another operation. "In the case of infections, which may become chronic, sometimes three or four follow-up surgeries are needed."
Another source of information - a new Danish study - looked at 197 patients who all had total knee replacement surgery. Researchers studied how the patients themselves rated the results of their operation. They also looked at the KSS rating system that scored the results of the surgery based on walking distance, ability to climb stairs and the need for walking aids.
"Outcomes drastically worsened with an increase in BMI" explained Anette Liljensø (Århus University Hospital), leading author of the study. With a five point increase in the BMI scale, there was a 96 percent greater risk of having a poorer KSS result. If the patient’s BMI score was 10 points higher, that risk went up by 284 percent. However, Peter Kay points out that the reason these figures look so high is that generally, hip and knee replacement is a very safe operation, and so the overall risk is pretty low.
"The data no longer leave room for doubt," said Dr Daniel Haverkamp. "Overweight and obesity are predictive factors for dangerous complications and poor outcome in lower limb joint replacement, and we have to tackle that problem. Obese patients must be informed about these risks and urged to lose weight before surgery."
Peter Kay agrees. "The message to get out is that ideally people should try to lose weight before they have surgery. Ideally they should lose weight to try to protect their joints anyway, and to stop them getting other problems such as diabetes and heart disease."
First published June 3, 2011
Useful website
British Orthopaedic Association - www.boa.ac.uk