Thanks to their mechanical strength and other desirable properties, metals have been a mainstay in medical implants for decades. But will they continue to be prominent in next-generation implants, or will they be passed over in favor of other biocompatible medical materials? The answer may just be both. 
Over time, PEEK and other biocompatible polymers have supplanted metals—especially stainless steel—in a number of orthopedic applications, while the potential commercialization of Abbott Vascular’s bioabsorbable stent could serve as yet another example of devices that no longer depend on metal. Furthermore, some people question whether metal-on-metal hip implant designs have literally worn out their welcome: Inflammation and early implant failure have been attributed to metallic debris particulates generated by friction caused by the metal bearing materials.
In light of this design and attitude shift away from metals, I recently asked a panel of experts specializing in the PEEK polymer, metal alloys, and ceramics for their two cents on the role that metal may play in future implants. A response by Robert Raess, medical market manager and Midwest regional manager at Titanium Industries Inc., represents the general consensus of the panel. “There will always be a place for the mainstays, but there will be unique and new applications. There’s still a growing population, and there will always be new procedures, but I think there’s a market for everything,” he says.
Raess issues a solid assessment. It’s unlikely that metals will be out of the picture completely any time soon when it comes to implants; in fact, they remain important in a variety of applications. However, their role (along with the role biocompatible polymers) could be changing. For example, metal may no longer be the dominant material in a given device, but it may still be incorporated into the implant design to serve a particular function or provide specific properties. “The most important thing I see is integrating different materials together,” says panelist Andrew Nield, director of sales and marketing at C5 Medical Werks. There is no device that only uses a ceramic; it is integrated with polymer such as PEEK or a metal. That becomes much more important as you start to get smaller and smarter devices and you want to increase their reliability. You need to get more out of a material and get synergistic materials by putting two materials together.
Ultimately, the goal is optimizing biocompatible medical implants to enhance patient care, regardless of the material. “As we look at more-specific patient populations and their particular needs, it may be that new materials bring with them new benefits that outweigh those of metals or indeed other existing material solutions… I suppose it’s bringing something new that isn’t present at the current time for a particular niche application,” says panelist Marcus Jarman-Smith, technology leader at Invibio. Biocompatible polymers can bring their own benefits, ceramics others, and metals others. Really, we have to just consider the best solution for a patient and offer more high-quality choices to the engineers to hopefully encourage them to innovate either with a different material that allows them more freedom or with combinations of materials.”
What do you think about the role of metal in future implants? Let me know in the comments section. Also, read the full roundtable to find out more about our panelists’ thoughts on biocompatible metals, evolution versus revolution of materials, and what’s next for biomaterials. –Shana Leonard
REPRINTED FROM QMED ONLINE NEWLETTER.
