According to new evidence published on bmj.com, new hip implants appear to have no advantage over traditional implants. Some evidence even suggests that new implants may be linked to higher rates of revision surgery.
Although hip replacement surgery is commonly successful, there are nevertheless a significant number of patients who require revision surgery within 10 years to replace implants due to dislocation, infection, wear, loosening, instability or other mechanical failures.
Traditional hip implants consist of metal on polyethylene or ceramic on polyethylene bearing surfaces and are linked to low revision rates, whereas newer alternatives are made from metal on metal or ceramic on ceramic bearings, however their benefits compared with traditional implants is still unclear.
BMJ has called for better regulation of medical advices after several incidents have been reported whereby it has been detected that patients with metal on metal hip implants displayed severe cases of accumulation of metal ions in their tissues. In light of this, the US Food and Drug Administration (FDA) initiated a comprehensive review of evidence for approved hip implants in 2009.
Professor Art Sedrakyan and his team collaborated with the FDA in comparing the safety and effectiveness of hip implants with different bearing surfaces. They evaluated results of 18 studies with 3,139 patients and more than 830,000 operations from data obtained in annual reports of registries and discovered that functional outcomes, such as the ability to carry out common daily activities, and general quality of life scores were equal between the new traditional metal on metal or ceramic on ceramic hip implants compared with traditional hip implants.
Although one study showed that metal on metal implants were linked to fewer dislocations, they found evidence in the three largest national registries that higher rates of implant revision was linked to metal on metal implants compared with traditional metal on polyethylene implants.
Even though one trial demonstrated fewer revisions with ceramic on ceramic compared with metal on polyethylene implants, researchers found that the finding was not supported by data from national registries.
They conclude their findings, saying:
"There is limited evidence regarding comparative effectiveness of various hip implant bearings, and the results do not indicate any advantage for metal on metal or ceramic on ceramic implants compared with traditional bearings."
The researchers strongly recommend a large randomized trial of bearing surfaces before claiming any benefits, saying that until that time, "national registries provide important real world data that are critical for the safety and future comparative safety and effectiveness evaluation."
Written by Petra Rattue