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Back in November 2018, about 125 people packed into a hotel conference room for a one-day ASTM workshop on medical device coatings. Professionals from coating manufacturers, device companies and universities listened to two dozen presentations that reviewed coating applications, the success they’ve experienced and the challenges that remain with assessing their performance. FDA and ISO representatives were among the first presenters of the day.
The makeup of the room was significant in that few standards and guidance documents exist for coatings today. The workshop was designed to discuss and strategize needs in the development of coatings, with an intended outcome being a strategy for developing coatings standards and specifications that will serve as extensions of the recently published ISO standard, ISO 17327-1.
Coatings have been used in orthopedics for decades. So, why such a dialogue now? Gary Fischman, Ph.D., believes that device coatings are in a proliferation phase. Coatings are becoming more complex as implant surface relationship with bone integration becomes more important and companies seek to utilize coatings to prevent surgical site infection. These at the same time regulations, e.g. EU MDR, are becoming more stringent. Fischman, Principal of Future Strategy Solutions, is an integral part of the conversation worldwide as the U.S. voting delegate for the ISO TC 150 working group on coatings and the corresponding chair to the ASTM F04 coatings workshop.
“A coating is often times used to hide a surface or change what the biology sees of that surface,” Fischman says. “You see more coatings and surface modifications that effect how a product acts. As we do more of that and as people become confident with them, coatings become more available in medical devices. As they become more available in medical devices, they’re going to need to be standardized and regulated.”
Essentially, standards and guidance become inevitable as manufacturers seek to expand the use of technologies and get regulatory buy-in. Similar conversations are taking place with additive manufacturing, another technology that emphasizes surface characteristics. It was evident at the ASTM workshop that orthopedic coating manufacturers and device companies are leading the charge.
Attendees at the ASTM workshop were asked to write down gaps that they’ve identified when working with coatings. They wrote down broad, fundamental testing questions that demonstrate the importance of these groups work. The questions included: What’s the difference between a challenge test vs. a spot test? How do you test specific properties? How do you test adhesion?
The next steps for the ASTM working group are prioritizing which questions to answer, who should answer them (ASTM, ISO) and how they should be answered (standard, guidance). The process will likely take years, but the coordinated effort between ASTM and ISO should lead to less duplication of effort and less confusion when members of industry seek answers to questions.
“If you can create standards that can be used for compliance to regulations, they become extremely valuable,” Fischman says. “Groups like ASTM F04 and ISO TC 150 where they are tasked toward implants and surgical devices, there is a lot of interest in trying to get those standards together so that everything is easier to understand and everyone is on the same playing field.”
Fischman has decades of material and coatings experience, primarily in ceramics. He’s been in in the industry long enough that he consults for companies that are strategizing on ways to pick a coating and a material. When we spoke, we had to ask him what challenges manufacturers face during their decision making process.
“If you look at a coating, you’re looking at that system—so you’re looking at what you’re putting that coating on, whether that coating works well on that material. One has to understand a) what they want in the final product; b) they have to understand what a coating can do and c) they have to understand how coatings are put on so that they get the right process. If I take a physical vapor deposited coating, I can’t expect a strong interface on that without doing something else—not the kind of interface I would find with a plasma spray coating or an overlay coating. There are very, very different properties that are associated with those coatings, and there are also different properties with how that coating, which is a different material than the substrate, is going to act. …There are all sorts of things that play into the puzzle of what is the appropriate material, how is it manufactured. The questions are easier often because we have a limited number of coatings that we can use in medical devices. But at the same time, those materials may have more limited capabilities of becoming coatings. That’s a hedgy answer. But it’s a systems problem, and there is a systems-based set of questions that you need to ask.”
