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New Factors Challenge Traditional Testing Requirements

Knight also notes that additive manufacturing (AM), porous coatings, infused polymers and surface treatments for metals are areas that have experienced rapid advancement.

As newer technologies evolve, so will testing standards.

“With additive manufacturing comes the challenge of understanding the properties of your products and materials, and optimizing them,” says Gemma Budd, Business Manager, Healthcare, Lucideon. “For example, making titanium implants from AM results in an entirely different microstructure to cast or forged titanium, and the resultant impact on mechanical properties—typically weaker—is also clear. Understanding why this is, and how it might be improved, is something on which we are working closely with both the AM companies and the OEMs designing the products.”

“One of our OEMs brought us a 3D printed hip component, and FDA had asked for three or four different aspects of the standard test to be investigated closely,” Gascoyne says. “Part of the fear of 3D printing is porosity inside the implant—the small pores that form during the 3D printing process. Those can be removed using a standard technique of hot isostatic pressing called hipping. Whether or not that removes all of the voids within the implants, we don’t know. Voids can cause fracture and micro motion between the implant, leading to corrosion inside the body.”

   
hip joint_dic-Lucideon-webA hip joint under load is analyzed by Digital Image Correlation.
                

Printed metals, produced from powders and sintered via laser or electron beam into a hard object, are another area of concern, Gascoyne says.

“They [FDA] are worried that powder will remain on the surface of these implants and be released into the body slowly or suddenly right after implantation,” he says. “That metal might get into the articulating surface and cause high wear, or get into the modular connections of the implant and cause corrosion. It might cause tissue reactions. As industry is learning more and more about 3D printing and as we’re coming up to pre-product release testing, we’re learning as we go for this kind of system.”

Budd says she sees this with their customers’ products as well.

“They [OEM customers] are relying on our understanding of how materials behave—not just our ability to tell them what the test result is—to help them get to a product that they are confident is safe and effective,” she says.

Testing new devices that have no existing published test methods is another common hurdle.

“Device development typically outpaces standards development, so in many situations we guide our clients in developing custom test methods based on risk analysis, peer reviewed literature and prior experience with regulatory agency demands,” says Knight.

Market segments experiencing growth, such as small total joint replacement, is one example of this, Budd says.

“Aside from the normal mechanical tests, there are some performance properties that do not have standards associated with them,” she says. “For example, wear testing of shoulders, ankles, etc., doesn’t have an ISO or ASTM standard, but with the recent issues with wear debris from hip replacements, manufacturers are unsurprisingly wanting to take a closer look at these attributes, so they have to rely on literature methods and the expertise of their testing partner to design and validate an appropriate method for their products. We are getting asked more and more for this.”

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