Becker's Spine Review

20 Executive Briefing: Sponsored by: T hroughout a spine surgeon's career, he or she will encounter a myriad of implants each derived from different materials. Because implants can be manufactured in countless ways — ranging from 3D printing to injection molding — there's no shortage of options in the spinal surgery industry. While various implant materials have come and gone, PEEK and titanium remain the most common. When Paul Kraemer MD, of the Indiana Spine Group in Carmel, launched his practice, PEEK was establishing itself as the go-to substance for implants. Dr. Kraemer understood PEEK's appeal but also saw challenges related to its use, particularly its inability to fully osseointegrate due to its bioinert hydrophobic properties. In recent years the industry shifted back to titanium, and while Dr. Kraemer noticed improvements to osseointegration with 3D titanium, he still saw complications. Specifically, problems with revision surgery, modulus and visualization. "The next generation of implants is not going to be plain PEEK," Dr. Kraemer said. "Instead, it's going to be a PEEK 2.0. Whether that's titanium coated or surface coated or altered PEEK, it's the same pendulum that goes back and forth. It gets better every time, and each time a little more refined." Despite the quality of implants continuing to improve, the spinal interbody market has never had a load-bearing biomaterial specifically engineered for bone growth and the immune response. To fill this need, DiFusion has developed ZFUZE, the first load-bearing biomaterial specifically engineered for spinal fusion. ZFUZE is a combination of PEEK with additive compounding of a negatively-charged-super-hydrophilic ZEOLITE. The negatively charged zeolite changes the surface chemistry from inert-plain-hydrophobic PEEK to a super hydrophilic and negatively charged ZFUZE surface, resulting in more bone and less inflammation. By changing the surface chemistry of PEEK, from an inert, hydrophobic surface to a negatively-charged super hydrophilic surface for ZFUZE, the immune system does not illicit a foreign body response. This lack of long term inflammation contributes to higher bone mineralization density and osseointegration. Not only does the ZFUZE negative, super-hydrophilic charge allow for early cellular adhesion and proliferation, it promotes an early switch from proinflammatory M1 Macrophages to the M2 Macrophage which is a key marker for the start of the pro-healing phase of the immune response. A prolonged M1 response leads to the formation of granularized tissue and fibrous encapsulation currently associated with plain PEEK implants. In 2013, PEEK commanded 73% of the $1.4 billion spinal interbody submarket. Surgeons and OEM's began to realize that they were seeing implants with fibrous encapsulation in PEEK revision surgeries. This has pushed the pendulum back to titanium as surgeons have foregone the visualization and modulus benefits of PEEK for the better osseointegration properties of 3D printed titanium. OEM's have rushed to commoditize the 3D titanium market as almost every company now has a 3D printed titanium implant with little to no differentiation. The swinging pendulum of titanium and PEEK When surgeons began using implants, titanium quickly emerged as the preferred material because of its sturdy consistency and the ability to customize it. Nevertheless, titanium is still not the perfect implant material. The body will sometimes reject titanium due to its rigidity. "The biomechanics of the titanium [implants] were such that they could sometimes impair normal healing by being too rigid and too stiff," said spine surgeon Nitin Bhatia, MD, of UC Irvine. The inelasticity in titanium implants spurred researchers and spine surgeons to explore alternate material options. Around 15 years ago, PEEK was introduced to the spine implant industry. PEEK has an advantage over titanium because its biomechanics are more consistent with bone. The End of an Era? — New ZFUZE Biomaterial Bridges the Gap Between PEEK and Titanium

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