Titanium Surface Technologies Impact the Spinal Fusion Material Debate

The debate over materials for spinal fusion implants continues, one that is focused around titanium and PEEK. As orthopedic OEMs position themselves to manufacture the best product using one material or the other (or both for those companies developing hybrid solutions), they are attempting to push the limits of each material to create unique solutions that make their material of choice the preferred option among surgeons.
 
One company, Titan Spine, has developed a nanotechnology-based process for producing an enhanced surface on titanium implants that offer significant benefits for bone growth in spinal fusion implantations. This subtractive process (the company is unwilling to share the exact details of the technique, for obvious reasons) results in an implant that’s unique among other spinal fusion products.
 
Following up on a meeting I had with the company at the 2016 NASS meeting, I was able to get a number of my questions asked by Titan’s VP of marketing, Andrew Shepherd. He provided some clarity on the spinal fusion material debate, the differentiation of their product, and what was still to come.
 
Sean Fenske: What happened to titanium in the past such that it fell out of favor for spinal fusion technologies?
Andrew Shepherd: Titanium cages of the 1990s fell out of favor initially due to the design of the threaded cylindrical cages because they damaged the vertebral endplate during insertion, which often led to subsidence. Furthermore, the implants contained a lot of titanium material (as compared to today’s designs) that caused a lot of scatter on CT images and hindered the ability to assess fusion status. We now know that the combination of interbody device material and design is essential.
 
Fenske: What are the concerns with using PEEK as an alternative?
Shepherd: Several significant concerns with PEEK come to mind.

First, PEEK is a material that has now been shown to create an inflammatory response that is counterproductive to bone growth. This inflammation actually causes the body to surround it with fibrous tissue to protect itself from the material. We showed this in our Whitecloud-award winning research presented at IMAST 2014 and subsequently published in the March 2015 issue of Spine.
 
Second, some PEEK implant designs have demonstrated an increased overall subsidence compared to analogous titanium devices. Our results from a dynamic mechanical studypresented at ISASS 2015 demonstrated that the PEEK implant, compared to our titanium TA implant, had a statistically increased settling rate and overall subsidence amount. PEEK’s “hard landing” may be the result of its anti-expulsion teeth that distributed the overall compressive force over a smaller contact area as compared to our roughened macro surface. Importantly, this research showed that subsidence is a function of more than the implant’s material modulus, but also importantly involves device design, which may have meaningful clinical implications.
 
Finally, given the industry’s recent experimentation with titanium-coated PEEK implants, we conducted research through abiomechanical study, with results published in February 2016 issue of The Spine Journal, that demonstrated titanium-coated PEEK implants are susceptible to the generation of particulate debris during impaction into the disc space, whereas Titan’s titanium interbody fusion devices showed no signs of impaction debris. In fact, the results showed that 26 percent of the teeth on the titanium-coated PEEK implants lost coating material ranging in size from 1 to 191 μm—with more than half of the particles ranging in size (less than 10 μm) that allows for phagocytosis. This is significant because reducing the risk of debris-induced inflammation at the site of implantation is essential to patient safety. This study clearly indicates that the additive coating process used to create the tested coated PEEK devices produces impaction-related debris.
 
Fenske: Why is titanium making a comeback in the industry?
Shepherd: Today, surgeons are no longer buying into holdover concerns with titanium as a material for interbody implants—visualization concerns are no longer an issue since there is so much less metal in our implants than in the threaded implants of the past. The scatter effect on CT and MRI is virtually non-existent. They also no longer believe the marketed concept of modulus of elasticity-related benefits of PEEK. It has been proven to be false. And most importantly, it is becoming widely understood that titanium is a superior material for osteogenesis. We have published several studies that proves just that, including our landmark study that was published in Spine in 2012 that demonstrated a significantly greater amount of osteogenic growth factor production necessary for fusion compared to PEEK and smooth titanium. Our competitors often erroneously cite this paper in reference to their own technologies. Also, we are seeing positive clinical results with our titanium, roughened-surface technology implants, with patients having rapid and robust fusions and overall improved patient outcomes. Results from a study presented at ISASS 2013 showed a 100 percent fusion rate for our titanium implants in patients between 6 and 12 months, with no appreciable subsidence and an inter-observer reliability rate of 95 percent.
 
Fenske: Can you describe your technology and explain how it aids in spinal fusion procedures?

Shepherd: Titan Spine’s proprietary nanoLOCK surface technology, featured on our full line of Endoskeleton devices, consists of a unique combination of roughened topographies at the macro, micro, and nano levels (MMN). This unique combination of surface topographies is designed to create an optimal host-bone response and actively participate in the fusion process by promoting the upregulation of osteogenic and angiogenic factors necessary for bone growth, encouraging natural production of bone morphogenetic proteins (BMPs), downregulating inflammatory factors, and creating the potential for a faster and more robust fusion.
 
Fenske: Is additive manufacturing involved in the process to develop this surface on an implant?
Shepherd: There is no additive manufacturing involved; instead, our nanoLOCK surface technology is manufactured through a proprietary subtractive process. The subtraction is critical to generate specific topographies at the macro, micro, and nano levels of the implant that we know are important for rapid bone growth. It also eliminates the potential for shedding debris during impaction into the disc space.
 
Fenske: What action needs to happen to further enhance the acceptance of titanium for spinal implants?
Shepherd: From a surface technology perspective, we need to continue to drive the conversation with surgeons around the nano-architecture of an interbody device and its ability to drive bone growth. As surgeons become more comfortable with the concept that the implant is heavily involved in the bone growth process, the more accepted the implants will become. In addition, the dramatically increased access to surgeons and hospital systems our recently-awarded Section X new technology code from CMS affords us is essential to enabling surgeons to use our products. And from a standards perspective, I feel it is important to update some of the ASTM standards so that they accurately mimic the stresses the implants will see in situ. For instance, the standards used to assess particulate debris generated under shear are significantly lower than what the implant experiences during implantation. In the name of patient safety, the standards should be scrutinized further.
 
Fenske: Can you please expand on the nanotech clearance you’ve received?
Shepherd: Our nanoLOCK surface technology has received two differentiated government agency designations that highlight its uniqueness within the interbody fusion device market. In late 2014, Titan Spine added an additional U.S. Food and Drug Administration (FDA) clearance for “nano-textured surface” to the product line’s initial 510(k), making our spinal implants the first and only FDA-cleared interbody fusion devices to feature nanotechnology. In October 2016, nanoLOCK was granted sole access to the new nanotextured interbody device new technology code, formally known as an “ICD-10pcs New Technology Section X Code,” by the U.S. Centers for Medicare & Medicaid Services (CMS).
 
Fenske: How has industry responded to your technology? 
Shepherd: We are seeing a significant shift going on right now in interbody devices as the market is moving away from PEEK and toward our core competency of surface-enhanced titanium devices. Our competitors are now producing titanium products, which is validating and demonstrates that we have put a dent in the market that we are now seeing legacy companies heavily investing in producing and marketing titanium products.
 
Since launch in October 2016 at NASS, our nanoLOCK technology has now been utilized in 1,000 surgeries across 28 states, and we are currently in the process of signing contracts with several other large health systems. This has dramatically influenced our operations; we have had to double our sales management team to meet accelerating demand.
 
Fenske: What’s on the horizon for this technology and/or Titan Spine?
Shepherd: Next up for Titan, we want to focus on and continue showing surgeons our high-value technology, demonstrating how our nanoLOCK implants can better support the 30- and 90-day episode of care. Data suggests that our implants can help reduce length of stay, readmissions, post-op injections, and other metrics that affect short-term outcomes and the cost of spine surgery, and it’s up to us to differentiate on this basis to continue our growth and sales.
 
Fenske: What about the future of titanium in spinal implant technologies?
Shepherd: The market is overwhelmingly moving toward surface-enhanced titanium as the dominant material in spinal interbody fusion technologies. The next frontier will be to apply our surface technology expertise to other spine and orthopedic applications.
 
Fenske: Any other comments or thoughts you’d like to share?
Shepherd: We have enjoyed building the surface technology category in spine from the ground up and now fully embrace the challenges of maintaining our leadership position.