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Hip and Knee Replacement: Low Rate of Repeat Surgery

Posted by medconsumers on October 1, 2008

Hip & Knee-Replacement Surgery: Need for Reoperation within Three Years is Extremely Low

People facing hip- or knee-replacement surgery might want to know whether there’s a success rate that can be checked beforehand. The National Joint Registry for England and Wales has provided just such information. It differs from the type of information generated by clinical trials, most of which take place in academic medical centers. The latter represents surgery performed under the best of circumstances, whereas registries provide information about surgery as it is performed in the real world.

In this case, the real world is England’s National Health Service between 2003 and 2006 when more than 150,000 people underwent hip or knee replacement. Nokuthaba Sibanda and colleagues of the London School of Hygiene and Tropical Medicine used the National Joint Registry to determine the rates of revision, or reoperation, within the first three years after surgery. Their findings were reassuring because the need for revision was low for both procedures. Overall, one in 75 people required revisions within three years of surgery.

Partial Replacement

When the researchers broke things down according to age, gender and different types of operative techniques, they found that those who underwent a newer technique called hip resurfacing were more likely to need another operation than people whose hips were fully replaced and cemented (3% vs. 0.9%).

Similarly, people who underwent unicondylar knee replacement, which replaces only half of the knee joint, also did not fare as well as the people whose knee joints were fully replaced. (For both unicondylar knee replacement and hip resurfacing, only the diseased parts of the joint are replaced, if the damage is limited to one component of the joint.) The revision rates were slightly higher for women who underwent unicondylar or hip resurfacing procedures. Additionally, the need for revision after knee replacement “strongly decreased with age.”

Sibanda and colleagues concluded that hip resurfacing should be performed only in men and unicondylar knee replacement only in elderly people. This conclusion was challenged soon after the study was published in the Public Library of Science Medicine, a peer-reviewed open-access online medical journal.

Conclusion Challenged

The conclusion that people fare worse after hip resurfacing and unicondylar knee replacement was called “misleading” and “erroneous” by Justin P. Cobb, professor of orthopaedic surgery, Imperial College, London. In a letter to the editor of the British Medical Journal, which had published a short report about the registry data analysis, Professor Cobb cites two studies to support his contention that partial replacement procedures provide better results.

The lower rate of complications after unicondylar knee replacement was established nearly 10 years ago with data from the Swedish registry, wrote Professor Cobb, “Total replacement is not more successful, just harder to revise.” There is a substantial group of people who not entirely happy with their total knee replacement result, he explained, “yet they choose not to undergo reoperation because revision of a total knee is a huge undertaking, while revising a partial knee [unicondylar] is a relatively simple affair.”

In response to an e-mail request for more explanations, Professor Cobb wrote that the registry analysis implies that any reoperation is equivalent to failure. “Of course any reoperation is an event best avoided, but the type of reoperation and the function following it are essential pieces of information,” he wrote. “Given the choice of lumpectomy or mastectomy, most women would accept a risk of one in 30 of having a second operation, if that meant a 29 out of 30 chance of saving a breast. So it is with partial knee replacement. If there’s a one in 30 chance of having your entire knee cut out and replaced, but a 29 in 30 chance of saving two-thirds of the joint and all the ligaments, then most would choose the conservative option.”

And what about hip resurfacing? “There does appear to be a higher failure rate for resurfacing among women,” responded Professor Cobb, “but the causes of that failure are still far from certain, and function following the more conservative operation of hip resurfacing does appear to be superior to that experienced when the entire hip is excised.”

Maryann Napoli, Center for Medical Consumers ©

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