Wednesday, October 3, 2012

Study: Outcome Poor with Hip Resurfacing

For male patients with smaller femoral heads hip resurfacing does not appear to be as effective as total hip replacement, researchers found.
And for women, 5-year implant survival was worse with hip resurfacing regardless of head size, Ashley Blom, PhD, of the University of Bristol in England, and colleagues reported online in The Lancet.

For men, implant survival was poorer with hip resurfacing than with other surgical techniques when the femoral head was less than 54 mm; for larger head sizes, implant survival was comparable.

"We recommend that resurfacing is not undertaken in women and that preoperative measurement is used to assess suitability in men," the authors wrote. "Before further new implant technology is introduced we need to learn the lessons from resurfacing and metal-on-metal bearings."

Hip resurfacing has been explored as an alternative to conventional total hip replacement in younger patients, because only 72% of traditional implants last 10 years when patients are younger than 55.
To assess implant survival with the various available techniques, Blom and colleagues looked at data from the National Joint Registry for England and Wales. The analysis included 434,560 primary total hip replacements performed from 2003 through 2011; 7.3% were resurfacings.

An unadjusted analysis showed that 5-year revision rates were higher for resurfacing than for stemmed total hip replacement (5.2% versus 2.8%), but there were important sex differences. The unadjusted 5-year revision rate was 8.5% for women and 3.6% for men, a difference not attributed to the smaller head sizes in women.

"Women might have an increased risk of osteoporotic fractures of the femoral neck or a greater predisposition to reactions to metal debris," the authors noted.

The median age of the patients who had a resurfacing was 55, and the researchers compared revision rates for the different techniques among patients of this age.

Women had worse implant survival with hip resurfacing across head sizes.
The predicted 5-year revision rates in 55-year-old women were 8.3% with a 42 mm resurfacing head, 6.1% with a 46 mm head, and 1.5% with a 28 mm cemented metal-on-polyethylene stemmed total hip replacement (the most common type of traditional implant).

Similar differences were seen for 55-year-old men with smaller head sizes.
The predicted 5-year revision rates were 4.1% with a 46 mm resurfacing head, 2.6% with a 54 mm resurfacing head, and 1.9% with a 28 mm cemented metal-on-polyethylene stemmed total hip replacement.

Of the male patients who underwent resurfacing, only 23% had head sizes of 54 mm or higher. In this group, hip resurfacing was associated with implant survival similar to that seen with conventional total hip replacement.

"Although our analysis focused on medium-term failure rates, other considerations need to be taken into account," the authors noted, including the conservation of femoral bone with resurfacing, differences in patient outcomes, and the release of metal into the patients' tissues, which can cause end-organ damage and DNA changes.

In an accompanying editorial, Art Sedrakyan, MD, PhD, of Weill Cornell Medical College in New York City, said that the higher revision rates with hip resurfacing represent "a class effect in the failure of hip resurfacing devices."

Like the study authors, however, Sedrakyan noted that other factors need to be considered when choosing between the different techniques. Good functional outcomes, for instance, may be particularly important for patients who have physically demanding jobs or who participate in sports.
"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," he wrote.

Blom and colleagues acknowledged that the study was limited by the observational, nonrandomized design, the relatively little information available on potential confounders, and the uncertain generalizability to patients beyond the U.K.

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