For years surgeons have debated which type of hip implants work best in patients. There have been questions on whether alternative implants such as metal-on-metal products, which at one point exceeded 30% of the market, have better outcomes than traditional implants such as metal-on-polyethylene.

A new FDA-funded data analysis study sheds some light on the use of metal-on-polyethylene, metal-on-metal and ceramic-on-ceramic implants and according to data presented in the study, there is no clear advantage of one of these products over another in terms of effectiveness, but there is evidence of a potential for harm associated with metal-on-metal implants. Results were published in the Dec. 1 edition of the British Medical Journal.

In the new paper, Art Sedrakyan, director of the Patient-Centered Comparative Effectiveness Program and associate professor of public health at Weill Cornell Medical College (New York), and his co-authors examined records of 3,139 patients and 3,404 hips enrolled in 18 comparative studies and more than 830,000 surgeries in national registries, comparing device effectiveness and quality of life.

While one clinical study reported fewer joint dislocations associated with metal-on-metal implants, there was evidence of a greater risk for implant revision procedures associated with metal on metal implants in three of the largest national registries (including more than 700,000 patients) when compared with metal-on-polyethylene. And while one trial reported fewer revisions with ceramic-on ceramic as compared with metal-on-polyethylene implants, data from national registries did not support this finding.

"The important issue here is that these alternative bearings, which are metal-on-metal and ceramic-on-ceramic, were introduced into the market with the great hope and in fact with an implied effectiveness and better effectiveness in safety profile," Sedrakyan told Medical Device Daily. "They were introduced with the idea that they would be associated with lower (wear and tear) characteristics so they would last longer. But there's no such evidence."

He added, "In fact there's evidence that metal on metal products are associated with a higher rate of revision occurrence which can be an indication of a higher rate of failure than the traditional bearings which are metal onpolyethane."

Sedrakyan's study has a history dating back to 2009, when the FDA was taking a closer look at the performance of hip and knee products. In addition, when Sedrakyan started the study, the issue of Metallosis came up in discussions.

"When we studied this imitative we discovered - just a couple of months later- that a UK regulatory agency alerted the public about concerns with Metallosis - high iron level in blood with people implanted with metal-on metal," he said.

But the authors said that the current analysis did not summarize evidence related to metal sensitivity or toxicity because its clinical relevance and implications on quality of life are in a process of being established.

In the future, authors say that before any claims of benefit could be made there should be large, peer-reviewed clinical trials comparing these treatments. Until then, national registries provide important real-world data that is critical for the safety and future comparative safety and effectiveness evaluation.

To address this issue, the FDA Center for Devices and Radiologic Health recently initiated the International Consortium of Orthopedic Registries to improve the safety and effectiveness of orthopedic devices and procedures through collaboration. The Consortium will be led by more than 10 national registries that currently have information on millions of orthopedic surgeries capturing all implantable devices on the market.

But currently, Sedrakyan said he would want patients and surgeons to thoroughly discuss the use of metal-on-metal products before these implants are placed in the body.

"We're really hoping that in fact patients will be aware of the issue, and surgeons are certainly aware already that metal on metal has been publicized related to iron levels in blood, but this study adds that clinical outcomes for metal-to-metal implants are not different than traditional implants as well. This information should help surgeons' potential to make a better decision if patients really need this implant at all. Hopefully patients will also inquire from their surgeons, if there are any characteristics they have that make it absolutely necessary to use these metal-on-metal products."

Sedrakyan added, "We're not saying that there aren't any indications for these products but I think surgeons should scrutinize their prior understanding of who is potentially eligible to receive this product. It's possible that there is a very select group of people that will need these products."

-- Written by Omar Ford, Medical Device Daily Staff Writer. 2011 Copyright AHC Media. All rights reserved.