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Materials are the Next Frontier for Orthopedics, Surgeon Says

As a biomechanical engineer in the department of orthopedic surgery at the University of Vermont, Gordon Donald, M.D., coated stainless steel pins with bioglass. Ever since that project in the late 1970s, he’s been involved in coatings and materials in some capacity, including implant invention and development and now primarily focused on the molecular modification of surface materials.

Dr. Donald, who became a spine surgeon after his early engineering days, serves as Managing Member and Director of Spinal Surgery at NJ Ortho Group and Founder and Principal of Molecular Surface Technologies. Knowing his expertise on material innovation and his clinical background, we asked him about the future of materials in orthopedics.

What is your research and product development experience with materials?

Dr. Donald: I was the Co-chairman of the medical advisory committee for a company called Orthobond. They started working on surface modification materials about 10 years ago. Eventually, I left and founded Molecular Surface Technologies with a few very talented and innovative partners. We focus on the molecular modification of material surfaces to create properties of those materials that are not inherent to the materials.

For example, titanium is very weakly antimicrobial, but we can make it very potently antimicrobial without changing its material characteristics or mechanical properties. We alter it in a way that doesn’t involve a structured coating that can scratch, come off, delaminate, etc., but that changes the way the surface properties behave.

Another benefit to our methodology is that the changes are transparent to the surgeon. It doesn’t affect the way that materials or tools look or feel or perform. The only thing that changes is that all of the bacteria that touches the surface dies, which is exactly what we all want in order to prevent bacteria from adhering to implants. We do it for nonmedical purposes, as well.

How would you describe the current state of orthopedic materials?

Dr. Donald: I think it is improving, and has been recognized as our next frontier of importance in the field. The days of tweaking the mechanical properties of mechanical devices are limited because of all the great work that’s been done. We are going to start seeing more significant advancements in biology and surface science. In that regard, we are already seeing growth in the business sector focusing on this newer technology, and that is a great thing.

Additive manufacturing has been the buzz for the last few years, and my sense is that while it offers tremendous advantages to some materials, not everything can be or should be manufactured with a 3D printer. It’s an expensive process, and I think in the coming years we’re going to be able to define more clearly the best manufacturing techniques specific to certain implants and materials.

From a surface coating point of view, one advantage of a single-layer molecular modification is that you can manage the complex geometry of all of these 3D-printed or open-architecture types of materials quite easily. Whereas with some of the early generation coating technologies, you can’t get there from here.

We are actually trying to get away from use of the word “coating” because it’s such a generic term for all of the different processes that exist today, and honestly it doesn’t always have such great connotations to it. In the past, coatings were kind of considered bad things. Molecular modification is a much more specific description of what you’re actually doing.

What material enhancements should manufacturers focus on in the coming years?

Dr. Donald: I think the two primary strategies, specifically for orthopedic surgery, are antimicrobial and bone healing. As a surgeon, I can’t emphasize enough the importance of bone healing, but the reality of the situation is that dollars drive development and the money is in preventing infection. That being the case, emphasis will continue to be on antimicrobial, especially in certain niches in orthopedics such as joint reconstruction. My sense is that this will branch out into tissue healing in general. Muscles, tendons, ligaments as well as bone, but that’s years down the road.

Since spine is your specialty, what is your opinion on the titanium vs. PEEK debate?

Dr. Donald: I think 3D-printed titanium makes a lot of sense because of the open architecture when compared to solid blocks of metal, from a mechanical point of view. The difficulty in the argument, however, is from a clinical point of view, but there’s not much difference when you look at the end result.

I used PEEK for 15 years and it performed very well. When [PEEK implants] fail, it’s usually because they don’t heal, and the bone graft around it hasn’t healed. It’s merely a spacer between bones. Something truly advantageous about the PEEK implant is that it’s easy to remove when that is necessary. If PEEK could heal solidly to the bone and not just be graft growing around the implant, that could change the argument for many people.

Titanium can be a bit more challenging when revisions need to be made. I think the consensus is slowly drifting towards titanium, and hopefully, we’ll see better and improved materials as that continues. Coatings and surface modifications of materials are going to do things that neither PEEK nor plain titanium have ever been able to do for us, so that argument may become moot.

As the surface science of materials continues to change, we’re going to start selecting bulk materials for the mechanical properties that we want them to have, and we’ll start selecting surface modifications for the biologic properties we want them to have. That’s where we will see the real advancement in biomaterials.

For more insight from Dr. Donald, view his presentation from OMTEC 2019, "Orthopedic Coatings: Predictions for 2025, A Surgeon's Perspective."

Kim Snell is an ORTHOWORLD Contributing Editor.