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Hip resurfacing offers no benefits over total hip replacement in some patients, finds study

BMJ 2012; 345 doi: http://dx.doi.org/10.1136/bmj.e6627 (Published 01 October 2012) Cite this as: BMJ 2012;345:e6627
  1. Zosia Kmietowicz
  1. 1London

An analysis of more than 400 000 hip replacement operations carried out in England and Wales since 2003 has called into question the value of resurfacing after it was found that this type of procedure is more likely to fail within five years than a total hip replacement.

The likelihood of needing a second operation is especially high among women, but revision rates after resurfacing are also raised in those men who have smaller devices fitted, show the findings.1 Resurfacing should be avoided in both these groups of patients, say the authors.

In February a joint investigation by the BMJ and the BBC's Newsnight programme found that metal on metal devices had a failure rate of 11.8% for resurfacing and 13.6% for total hip replacements after seven years, much higher than the 3.3% to 4.9% for hip implants made of other materials.2 The findings, which were based on data from the national joint registry for England and Wales, also found that failure rates were highest in women and smaller men.

After the investigation the British Orthopaedic Society advised doctors not to use metal on metal total hip replacements with bearings of 36 mm or more, while the Danish Orthopaedic Society advised against the use of all metal on metal devices.3

Resurfacing was introduced as an alternative to total hip replacements in the 1980s and marketed at younger patients, in whom total hip replacements were more likely to fail. In 2010 14% of hip replacements in people under 55 years were resurfacing procedures. All resurfacings currently use metal on metal devices, although devices using other materials are being investigated.

For the new study, reported in the Lancet, researchers examined the same data from the national joint registry for England and Wales concerning 434 650 hip operations undertaken between April 2003 and September 2011, of which 31 932 (7.3%) were resurfacings. The analysis found that outcomes varied between men and women and according to size of the device used.

In women the five year revision rate was 8.3% (95% confidence interval 7.2% to 9.7%) for a 42 mm metal on metal resurfacing head and 6.1% (5.3% to 7%) for a 46 mm resurfacing head. Total hip replacements using conventional materials had much lower revision rates: around 2.5% for uncemented ceramic on ceramic devices and between 1.5% and 1.9% for metal on polyethylene devices.

In men the five year revision rates were 2.6% (2.2% to 3.1%) for a 54 mm metal on metal resurfacing head and 4.1% (3.3% to 4.9%) for a 46 mm head. These compared with 3.4% (2.6% to 4.4%) for uncemented ceramic on ceramic total hip replacement devices and 1.9% (1.5% to 2.4%) for cemented metal on polyethylene devices.

Commenting on the study in a linked editorial, Art Sedrakyan, of Weill Cornell Medical College in New York, said that the findings “signify a class effect in the failure of hip resurfacing devices.”4

He added, “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 and harms of hip implants.”

Ashley Blom, professor of orthopaedic surgery in the University of Bristol’s School of Clinical Sciences and one of the study’s authors, said, “Resurfacing failure rates in women were unacceptably high. In view of these findings, we recommend that resurfacing procedures are not undertaken in women.”

In the case of men the authors said that “the decision to undertake resurfacing procedures needs to be made carefully.” They added, “Because femoral head size is determined by patient anatomy, we recommend that preoperative measurement is used to establish suitability for resurfacing.”

They also warned, “Before further new implant technology is introduced [such as metaphyseal bearing implants and ceramic on metal bearings] we need to learn the lessons from resurfacing and metal on metal bearings.”

Speaking to the BMJ, Blom acknowledged that the UK Medical and Healthcare Products Regulatory Authority had a difficult job but that the rules for approving devices were different from those governing approval of drugs.

He said that hip devices were assessed only in mechanical engineering tests but that the problem with resurfacing devices “seems to be a biological one.”

“Regulation needs to be tight enough that patients are safe but not so tight that it stifles innovation. It is much easier to bring an implant to market than a drug, and maybe [the MHRA] needs to revisit that. All a device manufacturer needs to show is equivalence—that would never work for a drug,” said Blom.

Notes

Cite this as: BMJ 2012;345:e6627

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