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Keith Barnard, MD
Oct. 4, 2012 – An operation known as hip resurfacing -- an alternative to hip replacement often recommended for younger patients - is prone to frequent failure and should not be used in women, a new study shows.
Researchers looked at data from 434,650 operations carried out in England and Wales between 2003 and 2011, of which 31,932 (7.4%) were resurfacings.
Hip resurfacing is similar to hip replacement. In a replacement operation, though, the rounded top section of the thigh bone, known as the femoral head, is completely removed and replaced. During resurfacing surgery, the femoral head is ground down to an even surface and given a metal cap.
Hip resurfacings always have metal-on-metal bearings, while total hip replacements can have a variety of bearing options, such as ceramic, metal, or plastic.
Researchers from the University of Bristol looked at the failure rate of resurfacing implants since the United Kingdom's National Joint Registry was set up in 2003. They used data from the next seven years to compare them with total hip replacements.
They found that the predicted seven-year failure rate for a 55-year-old woman who had undergone hip resurfacing ranged from 8.54% to 11.67%. This failure rate was dependent on the size of the femoral head, with the smallest sizes more prone to early failure.
These failure rates were much higher than full replacements with a metal ball and a polyethylene socket, where the failure rate was between 1.81% and 2.25% over seven years.
Men also experienced higher failure rates with resurfacing surgery compared to total replacement.
The findings appear in the online edition of The Lancet.
Ashley Blom, MD, PhD, is a professor of orthopaedic surgery in the University of Bristol’s School of Clinical Sciences, and one of the paper's authors. "Resurfacing failure rates in women were unacceptably high. In view of these findings, we recommend that resurfacing procedures are not undertaken in women," she says.
Furthermore, "the National Joint Registry for England and Wales has the biggest joint replacement database in the world, allowing us to analyze over 30,000 hip resurfacings up to seven years after surgery. Our findings show that resurfacings with smaller head sizes are prone to early failure, and in particular that resurfacing in women has much worse implant survival, irrespective of head size," she says.
The researchers also write that their findings cannot simply be explained by the use of smaller head sizes, since women fared worse than men even with the same head size. Women might have a higher risk of osteoporotic fractures in the thigh bone, or they may be more susceptible to complications from metal-on-metal prostheses.
The researchers acknowledge that surgeons will need to weigh other factors when assessing whether hip resurfacing is suitable for a patient, such as the relative benefits of total hip replacement and resurfacing surgery on patient function and quality of life.
In an editorial to the study, Art Sedrakyan, MD, PhD, of Weill Cornell Medical College in New York, said: "Regulators and surgeons need to make proper recommendations for patients, such as not using resurfacing in women, and developing decision aids for patients to convey the benefits, harms, and uncertainty related to second surgery with large metal-on-metal implants."
Nicola Lennard, MD, the deputy clinical director of the Medicines and Healthcare products Regulatory Agency in the U.K., says: "Decisions about what hip implants to use in patients are made by clinicians after careful consideration of the risks and benefits for each individual patient. This involves taking into account the patient’s age, gender, and activity level. For some patients a resurfacing hip implant may be the most clinically appropriate implant for them.
"The use of these hip resurfacing implants has fallen from about 11% in 2006 to about 2.5% in 2011, and only about one in six hip resurfacings were carried out on women in 2011. This change is a result of a better understanding by clinicians of the risks and benefits of hip resurfacing compared with other kinds of hip replacements in different patient groups."
SOURCES:Blom, A. The Lancet, published online Oct. 2, 2012.Sedrakyan, A. The Lancet, published online Oct. 2, 2012.News release, The Lancet.Medicines and Healthcare products Regulatory Agency (MHRA).
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